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Gravity Experiments for Kids

July 5, 2021 By Emma Vanstone Leave a Comment

These gravity experiments are all fantastic demonstrations of gravity and a great way to learn about Isaac Newton and Galileo ‘s famous discoveries. If you enjoy them, do check our my book This IS Rocket Science which is full of exciting space activities demonstrating how rockets overcome gravity and other forces to launch into space followed by a tour of the solar system with an activity for each planet.

What is Gravity?

Gravity is the force that pulls objects towards the Earth. It’s the reason we walk on the ground rather than float around.

Gravity also holds Earth and the other planets in their orbits around the Sun.

Did you know – gravity exists on the Moon but it is not as strong as on Earth, which is why astronauts can jump higher on the Moon than on Earth. This article from ScienceAlert tells you how high you could jump on each planet in the Solar System compared to Earth.

Great Gravity Experiments for Kids

Galileo and gravity.

Galileo was a famous scientist in the 16th and 17th Century. His most famous observation was that two objects of the same size but slightly different mass (how much “stuff” it is made of) hit the ground at the same time, as far as he could tell, if they are dropped from the same height. This happens because the acceleration due to gravity is the same for both objects and that actually this acceleration has nothing to do with the mass of an object. This fact has been demonstrated many times, even on the moon with a feather and a hammer.

Back on our air-filled planet, if a feather and a ball are dropped from the same height they clearly do fall at different rates. This is because gravity is not the only force acting on the falling object, air resistance is also a factor and that does depend on quite a few properties of the object and the fluid it is falling in. This does include its mass, the surface area and how fast it is moving. The feather suffers a lot here being so light and having a much greater surface area.

Galileo dropped two balls of different weights but the same size off the Leaning Tower of Pisa, giving a hint that the mass of an object doesn’t affect how fast it falls.

However if a ball and feather are dropped in a vacuum , where there is no air resistance as there’s no air, the ball and feather will fall together and hit the ground at the same time.

Bottle Drop Experiment

Following on from the ball and feather experiment another great example of Galileo’s discovery is to half fill one plastic bottle and leave another ( the same size ) empty. If dropped from the same height they will hit the ground at the same time!

Issac Newton and Gravity

According to legend Issac Newton was sitting under an apple tree when an apple fell on his head, which made him wonder why if fell to the ground.

Newton published the Theory of Universal Gravitation in the 1680s, setting out the idea that gravity was a force acting on all matter. His theory of gravity and laws of motion are some of the most important discoveries in science and have shaped modern physics.

Film Canister Rocket

A film canister rocket is a fantastic demonstration of all three of Newton’s Laws of Motion , but it falls back to the ground thanks to gravity.

Water powered bottle rockets are another great fun example of gravity and lots of other forces too!

Defy gravity with a magnet

Did you know you can defy gravity using magnets. We love this activity as you can theme it however you want. Your floating object could be a spaceship in space, a flower growing towards the sun or even a plane in the sky.

The magnet holds the paperclip in the air as if it’s floating!

Straw Rockets – Gravity Experiment

Create your own straw rockets and launch at different angles to investigate how the trajectory changes. Of course these don’t have to be rockets, they could be anything you want, so get creative!

Parachutes are another great gravity experiment and perfect for learning about air resistance too!

Marble Runs

A DIY marble run is another hands on way to demonstrate gravity. Can you build one where the ball has enough energy to move uphill?

DIY Sling Shot

Finally, a simple slingshot is a brilliant and simple STEM project and perfect for learning about gravity as a shower of pom poms fall to the ground!

Last Updated on May 25, 2022 by Emma Vanstone

Safety Notice

Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

Showing Science: Watch Objects in Free Fall

A physics problem from Science Buddies

By Science Buddies

Key concepts Physics Free fall Forces Gravity Mass Inertia

Introduction Have you ever wondered how fast a heavy object falls compared with a lighter one? Imagine if you dropped both of them at the same time. Which would hit the ground first? Would it be the heavier one because it weighs more? Or would they hit the ground at the same time? In the late 1500s in Italy the famous scientist Galileo was asking some of these same questions. And he did some experiments to answer them. In this activity you'll do some of your own tests to determine whether heavier objects fall faster than lighter ones.

Background In fourth-century B.C. Greece the philosopher Aristotle theorized that the speed at which an object falls is probably relative to its mass. In other words, if two objects are the same size but one is heavier, the heavier one has greater density than the lighter object. Therefore, when both objects are dropped from the same height and at the same time, the heavier object should hit the ground before the lighter one. Is this true?

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Some 1,800 years later, in late 16th-century Italy, the young scientist and mathematician Galileo Galilei questioned Aristotle's theories of falling objects. He even performed several experiments to test Aristotle's theories. As legend has it, in 1589 Galileo stood on a balcony near the top of the Tower of Pisa and dropped two balls that were the same size but had different densities. Although there is debate about whether this actually happened, the story emphasizes the importance of using experimentation to test scientific theories, even ones that had been accepted for nearly 2,000 years.

Materials • Two balls of the same size, but different mass. For example, you could use a metal and a rubber ball or a wooden and a plastic ball, as long as the two balls are about the same size. If two spherical balls like this are unavailable, you could try something like an apple and a similar-size round rock. • A ladder or step stool  • A video camera and a helper (optional)

Preparation • You will be dropping the two balls from the same height, at the same time. Set up the ladder or step stool where you will do your test. If you are using a heavy ball, be sure to find a testing area where the ball will not hurt the floor or ground when it lands. • If you are using a video camera to record the experiment, set up the camera now and have your helper get ready to record. • Be careful when using the step stool or ladder.

Procedure • Carefully climb the ladder or step stool with the two balls. • Drop both balls at the same time, from the same height. If you are using a video camera, be sure to have your helper record the balls falling and hitting the ground. • Did one ball hit the ground before the other or did both balls hit the ground at the same time? • Repeat the experiment at least two more times. Are your results consistent? Did one ball consistently hit the ground before the other or did both balls always hit the ground at the same time? • If you videotaped your experiments, you can watch the recordings to verify your results. • Can you explain your results? • Extra: Try this experiment again but this time use balls that have the same mass but are different sizes. Does one ball hit the ground before the other or do they hit it at the same time? • Extra: Try testing two objects that have the same mass, but are different shapes. For example, you could try a large feather and a very small ball. Does one object hit the ground before the other or do they hit it at the same time? • Extra: You could try this experiment again but record it using a camera that lets you play back the recording in slow motion. If you watch the balls falling in slow motion, what do you notice about how they are falling over time? Are both objects always falling at the same speed or is one falling faster than the other at certain points in time? Observations and results Did both balls hit the ground at the same time?

You should have found that both balls hit the ground at roughly the same time. According to legend, this is what Galileo showed in 1589 from his Tower of Pisa experiment but, again, it's debated whether this actually happened. If you neglect air resistance, objects falling near Earth’s surface fall with the same approximate acceleration 9.8 meters per second squared (9.8 m/s 2 , or g ) due to Earth's gravity. So the acceleration is the same for the objects, and consequently their velocity is also increasing at a constant rate. Because the downward force on an object is equal to its mass multiplied by g , heavier objects have a greater downward force. Heavier objects, however, also have more inertia, which means they resist moving more than lighter objects do, and so heaver objects need more force to get them going at the same rate.

More to explore Elephant and Feather—Free Fall , from The Physics Classroom Engines of Our Ingenuity: No. 166: Galileo's Experiment , from John H. H. Lienhard, University of Houston Video: Fall of 2 Balls of Different Weights , from Matthias Liepe, Cornell University What Goes Up, Must Come Down: Conduct Galileo's Famous Falling Objects Experiment , from Science Buddies

This activity brought to you in partnership with  Science Buddies

Falling for Gravity

Calculate the acceleration of gravity using simple materials, a cell phone, and a computer to record, watch, and analyze the motion of a dropped object.

• Two-meter measuring tape or two meter sticks
• Masking tape
• Small, cheap, rugged flashlight
• Towel, carpeting, or other soft material for the dropped flashlight to land on
• Digital camera with video capability (the HD camera on a phone should work fine)
• Computer with a program that lets you play videos frame by frame (not shown)
• Pencil and paper to record data (not shown)

• Locate a wall with a non-reflective surface. This Snack will not work in front a whiteboard or window.
• Tape the two-meter measuring tape to a flat wall. Position the measuring tape so that the 0 cm mark is at the top and the remainder hangs straight down. (If using meter sticks, tape and stack the two sticks together to make a total length of two meters.)
• Directly below your measuring tape, place a towel, carpeting, or other material that will soften the impact of dropping the flashlight on the floor.
• To make the measurements more visible, add extra marks on pieces of masking tape and stick them next to the measuring tape every 5 or 10 centimeters.

Collect your data

Have one partner stand next to the measuring tape. Turn on the flashlight and point it upwards. Make sure your flashlight is on a non-blinking setting. Place the light as close to the 0 cm mark as possible and against the measuring tape. If possible, use only one finger to hold the flashlight still until the time of release. Have someone else film the drop with a digital camera (in HD at standard 30 frames per second).

Check your video to make sure you got the shot. Digital video is easy to erase and reshoot. Redo it if you didn’t get a clear view of your flashlight’s light falling straight down. Transfer your video file to a computer.

Record your data

Make a table with two columns to record your data. Label the columns “Time in seconds” and “Distance in meters.” (See the sample table below.)

Time Data: Since your camera records 30 frames a second, each frame represents only 1/30 of a second, or about 0.033 seconds. That means each frame will add an additional 0.033 seconds.

Distance Data: In your video player, find the frame just before your flashlight drops. (Note that frame-by-frame players usually let you move forward or backward via arrow keys. The frame you’re now at is time 0s and distance 0m.)

Now, step by step, record the distance in meters dropped and the corresponding time of the flashlight’s fall. Watch the screen closely. Notice that, during the first few steps, the flashlight doesn’t fall very much.

If your flashlight leaves a streak of light, only record the location at the bottom of the streak (the streak is a 1/30 th  of a second record of the light's fall).

Calculate the acceleration due to gravity

Acceleration describes how fast the rate of something changes.

Acceleration = ( V final – V initial ) / the time to make this change

Here’s an example using our data (see the table above): V initial is the flashlight’s velocity just before it’s dropped, or 0 m/s; V final is the velocity of the light at the end of the drop.

In our case, at time 0.297 to 0.33 s (time = 0.033 s), the distance traveled is from 0.4 m to 0.51 m (distance = 0.11 m).

V = distance / time

So, V final = 0.11 m / 0.033 s = 3.33 m/s

The time it takes to make that change is 0.33 s

Acceleration = (3.33 m/s – 0 m/s) / 0.33 s = 10 m/s 2

Use your own data to calculate the acceleration of the flashlight you drop.

In your own experiments, you can collect data from shorter or longer distances.

$$\text{Acceleration} = \frac{3.33 \text{m/s} - 0 \text{m/s}}{0.33 \text{s}} = 10 \text{m/s}^2$$

Gravity is a force that draws objects to one another. In this case, the objects are the flashlight and the earth. This fundamental interaction of nature causes objects like the flashlight to move toward the earth faster and faster.

Look at your data. You might notice that the distances between successive time intervals increases. This also means the object’s velocity is increasing, and increasing velocity is known as acceleration. You might have heard a car commercial use the phrase “Zero to sixty in five seconds,” or some such thing. That means the car went from one velocity to another in a certain period of time—that’s acceleration!

Things accelerate toward the earth at a constant rate. Your data should show that this rate is about 9.8 meters per second per second, or 9.8 m/s 2 . Scientists, engineers, teachers, and students also know this constant as, simply, g .

Graphing is a great way to see what’s going on with your data. Try plotting distance vs. time.

Is your graph a straight line? Is it a curve?

It should be a curve with the formula: d = 1/2 g t 2 ​. The graph of our sample data is shown below.

Put an object on a scale. Is it moving? Although it doesn’t look like it, your object is actually accelerating towards the earth. The scale’s pan is pushing again your object and forcing it from moving downward. The weight you read on your device is a result of the object’s mass and g .

Try doing this activity again, but drop lightweight objects with lots of surface area, such as coffee filters or feathers, and see how the results differ. Although g is still at work here, air resistance also plays a role.

See this Snack in action in this video .

Related Snacks

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15+ Preschool Science Experiments that Explore Gravity

August 17, 2016 by Sheryl Cooper

Last Updated on July 22, 2024 by Sheryl Cooper

Inside: Explore gravity with these 7 fun preschool science experiments ! Activities that include pushing, throwing, and falling – all hands-on and fun!

Have you noticed how preschoolers are fascinated by things that move? Whether it’s pushing, throwing, or falling, they are very into it!

So why not tap into this interest?

Here are 7  fun preschool gravity experiments that you can add to your classroom or home activities , or for weekend fun.

 When talking about gravity with preschoolers, we keep it simple.

During our morning meeting or circle time , we demonstrate what happens if we drop an item.

We notice that it went down instead of up.

We can then try a gravity experiment during small groups, noticing that if we alter the movement or materials, things change.

This is basic and yet fascinating for this age group!

Defy Gravity  – This super cool activity is easy to make with paperclips and magnets. (Buggy and Buddy)

Drip Painting – Discover what happens when watercolors are dropped from the top of a vertical surface.

Galaxy in a Bottle  – The glitter doesn’t fall down, but instead rises as it settles. Crazy! (One Little Project)

Gravity Splatter Art – What happens when you drop something with paint on it?

Exploring Gravity with a Tube – Why does the position of the tube change the speed of the car? (HOAWG)

Exploring Gravity with Balance – Learn how to make a craft stick stand up right on a chopstick. (Rookie Parenting)

Gravity with a Pendulum  – Learn about the forces of motion and gravity by placing paint in swinging pendulum. (Innovation Kids Lab)

Pool Noodle Gravity Play – Explore gravity and slope by making your own pool noodle marble run. (Little Bins for Little Hands)

Ball Dropping Experiment – Drop different types of balls and see which one hits the ground first. (Inspiration Laboratories)

Apple Races – Explore gravity, motion, slopes, and more as they are rolled down plastic rain gutters. (Little Bins for Little Hands)

Water in a Jar Activity – How can you stop water from coming out of a glass when it’s turned upside down? (The Homeschool Scientist)

Bottle Rocket Launch – After making your own bottle rocket, make it launch by pumping air into it. (Science Sparks)

Which One is Heavier – Make your own balance scale and find different objects to weigh. (Go Science Kids)

Parachute Egg Drop Experiment – Learn about gravity and air resistance while dropping an egg using a parachute. (Science Sparks)

Center of Gravity Balancing Activity – This Cat in the Hat inspired activity involves balancing objects on a single point. (Preschool Pool Packets)

Exploring the Effects of Speed – Learn how speed has an effect on the gravitational pull on an object. (JDaniel4’s Mom)

More science for preschoolers:

Rainbow Science Activities

Winter Science Activities

15 Space Activities

Check out our favorite science toys and materials:

More science resources:

Hands-On Preschool STEM Activities

Science Activities that Explore Gravity

10 Science Experiments Preschoolers Love

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About Sheryl Cooper

Sheryl Cooper is the founder of Teaching 2 and 3 Year Olds, a website full of activities for toddlers and preschoolers. She has been teaching this age group for over 25 years and loves to share her passion with teachers, parents, grandparents, and anyone with young children in their lives.

Science Experiments for Kids: Learning About Gravity

Up, up, and away: fun and easy gravity experiments for kids.

Table of Contents

Amaze your friends and family with a science show. Ask your audience to predict the outcome of each of these easy science experiments about gravity .

All objects on Earth are pulled toward the planet’s center by the force of gravity. Gravity is the force that makes a basketball swish through a hoop. Gravity is the force that makes your glass of juice crash to the floor when it slips out of your hand. Gravity is the force that keeps your feet on the ground when you go for a walk. As Judy Breckenridge points out in Simple Physics Experiments with Everyday Materials, “Without gravity we would all float off into outer space.” Hooray for gravity!

In this post, we will share some of the best gravity experiments that you can do with your kids, using everyday materials that you can find at home. From balloon rockets to pendulum painting, these experiments will keep your kids entertained and educated all at once. Get ready to inspire your little ones with the wonder of science!

Quick Introduction to Gravity

Gravity is the force by which a planet or other body draws objects toward its center. The force of gravity keeps all of the planets in orbit around the sun . Earth’s gravity is what keeps you on the ground and what makes things fall. It’s what holds the atmosphere in place so we can breathe and it’s what allows us to use rockets to launch into space.

Gravity is a fundamental force of nature that is present everywhere in the universe. It is what gives objects weight and is responsible for the motion of planets, stars, and galaxies. Without gravity, the universe as we know it would not exist.

Understanding the basics of gravity is important for many areas of science, including physics, astronomy, and engineering. By conducting simple gravity experiments, kids can learn about this fascinating force of nature in a fun and engaging way. From exploring how gravity affects different objects to create their own mini-gravity wells, there are many exciting experiments that kids can do to learn more about this fundamental force.

Science Experiment: Dropping objects of different weights

Experiment 1: Dropping objects of different weights is a classic gravity experiment that teaches kids about mass and gravity. All you need for this experiment are a few objects of different weights, like a feather, a rock, and a rubber ball, and a place to drop them from, like a balcony or a staircase.

Start by asking your child what they think will happen when they drop each object. Will the heavier object fall faster or slower than the lighter object? Then, drop each object one by one and observe what happens.

You’ll find that all objects fall at the same rate, regardless of their weight. This is because gravity pulls all objects towards the earth at the same acceleration rate , which is 9.8 meters per second squared. You can explain this to your child by saying that the earth’s gravity pulls all objects towards it with the same force, so they all fall at the same rate.

You can also ask your child to try dropping the objects from different heights and see if that affects the way they fall. This will give them a better understanding of how gravity works and how it affects objects. This experiment is a great way to introduce your child to science and to help them understand the world around them.

Science Experiment: Making a gravity well

A gravity well is a concept that is used to represent the way gravity affects the path of objects in space. In this experiment, your child will learn how gravity works by creating a visual representation of a gravity well.

Materials needed:

• A large, flat container (such as a baking tray)
• A small ball (such as a marble)
• Food coloring (optional)

Instructions:

• Pour a thin layer of flour into the flat container, making sure it covers the entire surface.
• Place the small ball in the center of the container.
• If desired, add a few drops of food coloring to the flour around the ball.
• Use your fingers to gently press down on the flour around the ball, creating a depression in the flour. The depression should be deepest around the ball and gradually become shallower as you move away from the ball.
• Observe how the ball remains in the center of the depression you created in the flour. This is because the flour represents the fabric of space-time and the ball is pulled towards the center by the force of gravity.

To take the experiment further, you can try adding more balls to the container and observe how they behave differently depending on their mass and distance from the center of gravity well. This experiment is a great way to introduce your child to the fascinating concept of gravity and spark their curiosity about the world around them.

Science Experiment: Magnets to simulate gravity

Using magnets to simulate gravitational pull can be a fun and interactive way to teach kids about gravity. In this experiment, you’ll need a few simple materials such as a magnet, paper clips, and a thin piece of string.

First, tie the string to the magnet and then attach a few paper clips to the other end of the string. Next, hold the magnet above one of the paper clips and release it. You’ll notice that the paper clip is attracted to the magnet and will follow it as it falls. This is similar to how gravity works, as objects with more mass are attracted to each other.

You can also use this experiment to show how different objects with varying masses will be affected by gravity. Try attaching different objects to the string, such as a feather, a coin, and a small toy car. You’ll notice that the magnet has a stronger pull on the coin and car due to their greater mass, while the feather will not be affected as much because it has less mass.

This experiment is a great way to introduce kids to the concept of gravity in a fun and interactive way. It can also be a starting point for further discussions about the laws of physics and the universe around us.

Science Experiment: Making a simple pendulum

Making a simple pendulum is a fun and easy way to learn about gravity and motion. For this experiment, you will need a few simple materials:

• A piece of string or thread
• A small weight, such as a paperclip or washer
• A sturdy surface to attach the string

To make your pendulum, tie the string around your weight and attach the other end to your sturdy surface. You can use a table, a chair, or any other surface that won’t move around too much.

Once your pendulum is set up, give it a gentle push to set it swinging. Watch how it moves back and forth, and notice how the speed and direction of the pendulum change.

To make your experiment even more fun, try changing the length of the string or the weight of the pendulum. How does this affect the way the pendulum moves? Can you predict how the pendulum will behave based on these changes?

Making a simple pendulum is a great way to introduce kids to the concept of gravity and motion. Plus, it’s a fun and easy experiment that can be done with materials you probably already have at home.

Science Experiment: Gravity and Air Resistance

Before performing this experiment, show your audience a shoe and a flat piece of notebook or copy paper. Explain that you will be dropping both objects from the same height. Then ask your audience these questions:

• Who thinks the shoe will hit the floor first?
• Who thinks the paper will hit the floor first?
• Who thinks both objects will hit the floor at the same time?

Experiment:

• Hold the shoe in one hand and the paper in the other.
• Hold both objects high in front of you at equal heights.
• Release both objects at the same time.

Observation: The shoe hits the floor first.

Explanation: Because of the paper’s shape, its fall is slowed by air pushing up against its under-surface – this slowing effect is called air resistance.

Science Experiment: Effect of Gravity on Plant Growth

One of the most interesting aspects of gravity is its effect on living organisms. In this experiment, we’ll be looking at how gravity affects plant growth.

To start, you’ll need to gather some materials. You’ll need:

• 2 identical plants
• 2 identical pots
• Begin by filling both pots with soil and planting one of your plants in each pot.
• Water them both thoroughly and place them side by side in a sunny location.
• Now comes the fun part. Take one of the pots and place it on its side. This will cause the plant inside to be growing at a 90-degree angle to the ground. Leave the other pot standing upright.
• Over the next few weeks, observe the growth of both plants. Measure their height using the ruler and take note of any other differences you can see.

What you should find is that the plant growing at a 90-degree angle to the ground will grow differently than the plant growing upright. This is because gravity plays an important role in how plants grow. The plant growing on its side will have to work harder to grow against the pull of gravity, resulting in a different growth pattern than the one growing normally.

This experiment is a great way to teach kids about the effects of gravity on living organisms and can lead to further discussions about how gravity affects everything from trees to humans. Have fun experimenting!

Science Experiment: Gravity and Weight

Before performing this experiment, show your audience the shoe and the piece of paper crumpled into a ball. Explain that you will be dropping both objects from the same height. Then ask your audience these questions:

• Who thinks the paper ball will hit the floor first?
• Hold the shoe in one hand and the paper ball in the other.

Observation: The shoe and the paper ball hit the floor at the same time.

Explanation: Even though the earth exerts more pull on a heavier object, a lighter object experiences a greater degree of acceleration, meaning that it moves at a greater speed. Consequently, objects of different weights fall at the same rate when other forces such as air resistance are not a factor.

Science Experiment: Center of Gravity

Now it’s time for audience participation in your science show. Ask for volunteers for each of these exercises involving the center of gravity:

Pick up a penny

Ask a volunteer to stand against a wall with his feet together, heels pressed against the wall. Place a penny about one foot away on the floor in front of him. Ask him to pick up the penny without moving his feet or bending his knees. Can he do it?

Lift your left foot

Ask a volunteer to stand with her right side against a wall, pressing her right foot and cheek against it. Instruct her to lift her left foot off the floor. Can she do it?

Jump forward

Ask a volunteer to bend forward and grab his toes, keeping his knees slightly bent. Tell him to jump forward without letting go of his toes. Can he do it?

Ask a volunteer to sit in a straight-backed chair. Tell her to keep her back straight, her feet flat on the floor, and her arms folded across her chest. Then ask her to stand up. Can she do it?

Observation: Because all of these tasks restrict the center of gravity, it’s almost impossible for a person to perform any of them.

Explanation: As far as gravity is concerned, the weight of an object is concentrated at a single center point. The center of gravity for an object with a regular shape – the Earth, for example – is located at its geometric center. However, in irregularly shaped objects – the human body , for instance – the center of gravity moves around. If you try to shift too far away from your center of gravity, you’ll lose your balance.

Share Fun Science Experiments With Family and Friends

Learning new things about the world around you is fun and exciting. It’s even more fun when you share your discoveries with your family and friends. Gravity is just one of the interesting forces of nature – there are many more to explore and share.

Final thoughts on teaching kids about gravity

Gravity is a fascinating concept that has been studied and explored by scientists for centuries. Teaching kids about gravity can be a fun and engaging way to introduce them to the wonders of science and the natural world around them.

By conducting simple experiments and activities, kids can learn about the basic principles of gravity and how it affects the world around us. From dropping objects of different weights to observing how objects fall at the same rate, there are endless ways to explore this fascinating force.

Not only can teaching kids about gravity be fun, but it can also help to develop their critical thinking skills, problem-solving abilities, and scientific knowledge. By encouraging kids to ask questions and explore the world around them, we can inspire a love of learning and an appreciation for science that can last a lifetime.

Teaching kids about gravity can be a fun and rewarding experience for both children and adults alike. By providing opportunities for hands-on exploration and discovery, we can help kids develop a lifelong love of science and learning. So, let’s get started and see where the wonders of gravity take us!

• Bardhan-Quallen, Sudipta. Championship Science Fair Projects . NY: Sterling Publishing, 2004.
• Breckenridge, Judy. Simple Physics Experiments with Everyday Materials . NY: Sterling Publishing, 1993.
• Cobb, Vicki. Bet You Can’t! NY: Lothrop, Lee & Shepard Books, 1980.

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Gravity Activities For Preschoolers

There are so many low or no-prep hands-on gravity activities that you can do with young kids to introduce this concept! We love easy preschool science activities !

Fun Ways To Demonstrate Gravity

Here’s my son at age 3, exploring a book filled with pictures of kids testing out gravity. Then, we had a blast jumping, falling, dropping, rolling, and pouring things together. I think he got the idea that what goes up must come down (unless it gets stuck)! Here are super quick ways to demonstrate gravity in 2 minutes.

• Pour water into a glass.
• Knock something (not breakable) off a table.
• Fall onto a bed or a pile of cushions.
• Push a toy car down a toy ramp (Hotwheels tracks).
• Toss a pile of socks in the air.

Gravity Activities For Kids

How do you explain gravity to young kids? You show them! Take a look at these playful, hands-on activities that get kids moving and explore how fun gravity is. My son loves anything gross motor involved, and gravity activities can incorporate lots of movement for young kids.

💡Get up and test gravity for yourself with a free gravity activity pack ! Share this information guide, quick activity, and gravity coloring sheet with your kids!

Some activities share an easy description to get you started, as they are meant to be low to no prep. In comparison, some activities have links to explore further how to do the activity!

💡 Note: While the concept of gravity is much more involved than the simple examples below, it’s just the right amount of information for our youngest scientists! For older kids, check out these gravity experiments !

Dropping Objects

Have kids drop various objects (e.g., balls, feathers, toys) from different heights and observe how they fall. Explain that gravity pulls objects down towards the Earth.

Feather and Coin Test

Place a feather and a coin side by side. Ask kids which one will hit the ground first when dropped. Demonstrate that they both fall at the same rate due to gravity.

Water Balloon Toss

Fill water balloons and play catch. Discuss how the balloons fall because of gravity pulling them downward.

Show how gravity affects us by performing jumping jacks, jumping on a trampoline, or simply jumping in place and feeling the force pulling us back to the ground.

Magnet Play

Use a magnet and a variety of metal and nonmetal objects to show how magnetic pull is stronger than gravity. Check out all sorts of fun magnet activities here .

Balancing Act

Use a ruler or stick to balance various objects on the edge. Talk about how gravity keeps them stable or causes them to fall. Check out our balancing apple or balancing animal activities to try this!

Paper Airplanes

Fold paper airplanes and see how gravity pulls them downward when thrown. make our paper airplane launcher here.

Rolling Race

Use toy cars or balls to race down ramps at different angles. Discuss how gravity influences their speed. Check out our ramps and friction activity for preschoolers or this fun apple race gravity demonstration.

Waterfall Experiment

Pour water down a sloped surface and watch it flow due to gravity. Build a water wall!

Floating and Sinking

Test different objects in a water basin to see which ones float (buoyancy) and sink due to gravity. Try this sink or float experiment!

Marble Run/Maze

Build a simple marble maze and observe gravity pulling the marbles through the tracks. Use paper towel tubes to create a marble coaster.

Helium Balloons

Compare regular and helium balloons to show how gravity pulls one down while the other floats up.

Quick explanation: Gravity is still pulling down the balloon but the special gas inside keeps is different than regular air so it keeps it floating instead. In fact, if you don’t tie down a helium balloon it will float away until the gas inside slowly leaks out.

Musical Chairs

Play musical chairs and discuss how gravity keeps everyone seated until the music stops.

Bouncing Balls

Show how gravity causes a ball to bounce back up after hitting the ground. Have fun tossing and bouncing different balls. See how you can incorporate this into gravity art below.

Fly Swatter Balloon Tennis

Play a fly swatter balloon tennis game where kids try to “swat” falling balloons to show gravity in action.

Gravity Art

Place a large sheet of paper on the floor. Have kids stand up and drip paint onto paper placed on the floor and watch how gravity creates unique patterns. Try using eye droppers or basters! Alternatively, you can take it outside and have kids drop small bouncy balls covered in paint onto the paper. Fun, messy, process art for kids!

Collapsing Towers

Build towers with various materials (e.g., cards, paper cups) and let kids knock them down to see gravity at work. Try this paper cup tower challenge to get started!

Rolling Downhill

Walk outside and have fun rolling balls or toys down a hill to see gravity’s influence. If you are daring roll yourself down the hill.

Playground Fun

Take a trip to the playground and point out how gravity affects you on the slide, monkey bars, and swings! Gravity is always pulling you back down and can make the monkey bars quite challenging!

Slinky Play

A slinky loves gravity and a set of stairs. If your kids have never played with a slinky, it’s a must-try activity.

Remember, preschool-age kids learn best through hands-on play, so try to make these activities engaging and interactive. Encourage their curiosity and ask open-ended questions to help them explore the concept of gravity further. I love the question, “What do you think will happen if_______?”

What is Gravity?

Earth’s gravity is the force that keeps everything on the planet’s surface and makes things fall to the ground. Good thing!

Imagine you are standing on the ground, and there’s an invisible force pulling you down toward the Earth. That force is called gravity. It’s like a giant magnet that attracts everything with mass toward the center of the Earth.

The Earth is super big and has a lot of mass, which means it has a strong pull. That’s why we don’t float away into space like astronauts do when they’re far from Earth. Instead, gravity keeps us firmly planted on the ground.

Have you ever watched a NASA video of an astronaut floating around inside his/her ship?

The Moon also has gravity, but its pull is not as strong because it’s much smaller than Earth. That’s why astronauts can jump higher on the Moon than on Earth!

Even if you can jump really high, you’ll still come back down!

Now, the Earth’s gravity doesn’t just work on you; it also works on everything around you, living and nonliving! It pulls down the trees, the buildings, and even the air you breathe. That’s why things always fall when you drop them. The Earth’s gravity is pulling them like the glass of milk that my son knocked off the table this morning!

When you throw a ball up in the air, it comes back down because of gravity!

Gravity is a fantastic force that keeps our feet on the ground, helps things stay where they are, and makes the world work together. Without gravity, everything would be floating around in space. So, we can thank Earth’s gravity for making our planet such a fantastic place to live!

TIP: Get kids talking about what types of things they think gravity effects in their life!

Books About Gravity

Here are some simple and engaging book ideas that will introduce the concept of gravity in a fun way, making them suitable for preschoolers and kindergarteners who are just beginning to explore scientific concepts.

“Newton and Me” by Lynne Mayer : This beautifully illustrated picture book introduces young children to the concept of gravity through the story of a young boy and his toy. It’s a charming and easy-to-understand book for preschoolers.

“Gravity” by Jason Chin : While this book is suitable for older preschoolers and kindergarteners, it features stunning illustrations and a straightforward explanation of gravity that young children can enjoy with the help of an adult.

“What Is Gravity?” by Lisa Trumbauer : This book from the “Rookie Read-About Science” series is designed for young readers and provides a basic introduction to gravity. It includes simple text and colorful pictures, making it perfect for kindergarteners.

“I Fall Down” by Vicki Cobb : Geared toward preschoolers and kindergarteners, this book playfully explores the concept of gravity. It features interactive experiments and encourages young children to think about gravity daily.

“Gravity Is a Mystery” by Franklyn M. Branley : Part of the “Let’s-Read-and-Find-Out Science” series, this book is aimed at early elementary readers but can be suitable for kindergarteners with adult guidance. It uses simple language and illustrations to explain gravity in a way that young children can grasp.

Helpful Science Resources To Get You Started

Here are a few resources that will help you introduce science more effectively to your kiddos or students and feel confident yourself when presenting materials. You’ll find helpful free printables throughout.

• Best Science Practices (as it relates to the scientific method)
• Science Vocabulary
• 8 Science Books for Kids
• All About Scientists
• Science Supplies List
• Science Tools for Kids

Printable Preschool Activities Pack

Get ready to explore this year with our growing Preschool STEM Bundle .

What’s Included:

There are 12+ fun preschool themes to get you started. This is an ” I can explore” series!

Each unit contains approximately 15 activities, with instructions and templates  as needed. Hands-on activities are provided to keep it fun and exciting. This includes sensory bins, experiments, games, and more! Easy supplies keep it low cost and book suggestions add the learning time. 

This is great! So many fun ways to explore gravity!

AWESOME explanation and such a variety of ways for children to experience gravity! I am in love with your indoor slide combo – wherever did you get it?

I always thought of gravity as too complicated to explain to my preschooler but you nailed it with these fun ways to show gravity in action! The slinky is an awesome idea. My daughter would have a blast falling down and throwing things in the air only to see them fall, all in the name of science! 🙂

What a simple but fun way to explain the meaning of gravity and what it can do. I think reading gravity’s definition in a book makes it more complicated. I am sure Liam did enjoy the whole activity just looking at the photos.

It’s called Rhapsody by Cedar Works. We were lucky to purchase this from a friend used so the cause was significantly lower. S cool to have! Everyone is always jealous when they come over.

Gravity is a fascinating subject. Love a giant slinky experiment – so fun! Thanks for sharing with Afterschool!

Thank you for having us! He had a lot of fun experimenting around the house!

I love these simple experiments! I am featuring it today as part of a round up of Science activities for After School.

Awesome! Thank you. I will stop by to check it out!

Comments are closed.

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~ projects to try now ~.

G is for Gravity Experiment

We’re continuing the A to Z Science series  for toddlers and preschoolers here at Inspiration Laboratories with the letter G. G is for Gravity Experiment . Experiment with gravity and have some fun with science.

What is Gravity?

Gravity is a force that attracts things {objects, masses, particles, light}. Most of the time we think about gravity as the reason we are walking on the ground rather than floating in the air. We are attracted to the Earth. Gravity is why objects fall to the ground. The strength of the attraction depends on the mass of the two objects and the distance between them. The greater the mass, the greater the attraction.

How to Explain Gravity to Toddlers and Preschoolers?

For toddlers, you may not even want to explain it to them. It’s okay to just let them experience the concept without actually giving it a name yet. For preschoolers you can simply explain it as this: Gravity is what keeps your feet on the ground. It’s why objects fall to the ground.

Have your child jump up. Ask: Why did you fall back to the ground? Why didn’t you stay in the air?  Because gravity pulled you back down.

Simple Gravity Experiment

Collect a number of balls of different sizes and weights. You might also want to grab a stopwatch. Choose a location to conduct your experiment. You can simply have your child stand on the floor. You could also head to the park and drop balls from atop the playground equipment.

Explain to your child that she is going to drop the balls and see which one hits the ground first. Ask her to predict which ball will hit first. {Choose one over another, or they can both hit at the same time.} It may be easier to drop the balls one at a time. In this case, you’ll want a stopwatch to time the fall.

Have your child hold a ball up and then drop it to the ground.

You can also have your child drop two at a time. Hold the balls at the same height. Be sure to drop them at the exact same time. You might want to practice a few times.

The Results

Did each ball take the same amount of time to hit the ground? They should have. The force of gravity depends on the mass of the object. The greater the mass, the greater the force of gravity. However, no matter the mass, an object will free fall at the same rate {the acceleration due to gravity}. The explanation has to due with inertial mass and a few other things that toddlers and preschoolers will not understand nor should they.

The point of the experiment is to observe gravity at work, ask questions, and make predictions.

If you drop two objects at the same height and they do not hit the ground at the same time, friction and air resistance are most likely to blame. They can slow down an object. Try different shaped objects and see what I mean.

Be sure to check out the rest of the  A to Z Science  series!

Subscribe to the Inspiration Laboratories weekly newsletter. Each issue has exclusive hands-on science explorations for children, a recap of our latest activities, and special resources selected just for you!

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3 Unique Gravity Experiments to Try with Your Kids

Simply put, gravity is the force of the earth that pulls objects towards its core, preventing them from floating off into space. For many adults, explaining the concept of gravity to a child can seem daunting. However, through the use of the following gravity experiments for kids, children will gain a better grasp of gravity’s role in our everyday lives while also having some fun!

Paperclip Gravity Experiment

Most gravity experiments don’t require many materials. For this experiment you’ll use:

• Paper clips

First, tie one end of a piece of string to a paperclip and tie the other end around the stick. Repeat twice more so that the stick has three paper clips attached. Hold the stick up in the air, allowing the paperclips hang freely. Tilt the stick back and forth.

As is demonstrated, Earth’s gravity is continuously pulling our bodies and the objects around us to its core. Even when the stick is tilted, Earth’s gravitational pull exerts its force on the paper clips pulling them straight down toward the Earth.

Gravity Water Drop

This next experiment requires just three items:

• A paper cup

On the outside of the cup near the bottom, poke a hole using a pencil. Placing a finger over the hole, fill the cup with water. Remove your finger from the hole. You should find that the water flows out of the cup in an even, steady stream (if the water is not quite flowing smoothly, try poking a new hole and refill the cup with water). Next, holding your finger over the hole, fill the cup once again with water. Drop the cup, removing your finger from the hole at the same time. You’ll find that as the cup falls, no water flows out of the hole.

When you first held the cup in the air and removed your finger, gravity pulled the water down towards the ground and water pressure forced it out of the hole. However, when the cup and water fell at the same speed, there is no water pressure. Without this force, the water remains inside the cup as gravity pulls both to the ground.

Galileo’s Experiment

• A sturdy chair
• Various household items

Gather items of differing weights and sizes, such as a ball, action figure or doll, and a balloon. Have your child stand on top of the chair while holding the items. One at a time, have your child drop each item from the same height. Keep track of how long it takes each item to reach the ground.

Though many believe that larger, heavier items will hit the ground first, this is not true. The rate of Earth’s gravitational pull on all objects is the same regardless of weight. Given the absence of air resistance, each object should reach the floor at the same time. Do your finding support this?

Testing the laws of gravity (or defying them !) can be done in a variety of hands-on, entertaining ways around the house and at school. Experiments for kids like those above are a great way to get kids learning and asking important questions about the world around them.

• Next Post: Using Pre-School Games to Help Kids Learn the Alphabet →
• ← Previous Post: Kindergarten Word Searches to Begin Building Your Child’s Vocabulary

Department of Earth and Planetary Sciences, Northwestern University

Measuring gravity, demonstration goals:.

• Explain how the acceleration of gravity gives a planet’s mass
• Measure the acceleration of gravity using the ball-drop method
• Understand the limitations of this method
• Measure acceleration of gravity using the period of a pendulum

Measuring gravity using the ball-drop method

Perhaps the most famous of Galileo ‘s experiments involved dropping two balls from a great height. (In actuality, he never dropped anything from the Leaning Tower of Pisa; instead, he had them dropped from the crow’s nest at the top of a sailing ship.) To replicate his experiment, you will need:

• Ball drop apparatus (Fisher VBS40881-1 $40.0 and VBS40990-1 $339.00)
• 2 Balls, of roughly the same size, but different weights
• Table or other flat, hard surface

1. Set up the Ball Drop apparatus before class. Double-check to make certain that the battery is charged, and that the room is dark enough for the IR sensors to work.

2. Pass the balls around the class. Have the students predict which ball will hit the ground first, the heavier or the lighter, and record their predictions on the blackboard.

3. Hold the balls in one hand, at a height of at least one meter over the table. Release the balls, and note the simultaneous noise of the impact. Point out that (to a first-approximation) the weight of the ball does not affect the rate at which it falls.

Now let’s go Galileo one better!

4. Place the small plastic ball that came with the ball drop apparatus. Show that the acceleration due to gravity can be found from the difference in velocities, as measured at the two IR sensors. Release the ball, and record the times one the board. Calculate the acceleration using:

g = d*(t 1  – t 2 )/(t 1 *t 2 *t 12 )

where d is the diameter of the ball, t 1  is the time the ball takes to pass through the first gate, t 2  is the time the ball takes to passthrough the second gate and t 12 is the time the ball takes to pass between gates.

5. Repeat with the steel ball, and compare the results.

For Discussion: How well do your measurements agree with the accepted value of ~9.78 m/s/s? Why do you think the difference in the times between the two balls exists? (HINT: Think friction!)

Measuring gravity with a pendulum

One day, while attending a Mass in the Duomo di Pisa, Galileo noticed that the lamp above him was swaying slowly. The slow, regular motion of the lamp inspired Galileo to check the measurements for gravity (which he had previously done using the inclined plane) by using the well known formula for the period of a pendulum: t = 2 pi sqrt (L / g) where L is the length of the pendulum. For this experiment, you will need:

• A Stopwatch
• A pendulum (Fisher CHS41475 $51)
• Alternative:  Make a pendulum using 1.5 m of string, a lead fishing weight and a ring-stand apparatus (or equivalent)

1. Set the pendulum length at .5 m.

2. Time how long the pendulum takes to make 10 oscillations.

3. Using the formula given above, calculate the gravity.

4. Now set the pendulum length to .75 m and repeat the experiment. Once again, calculate the gravity.

For Discussion: How well do your measurements agree with the accepted value of ~9.78 m/s/s? How well do the two values compare? What may have caused the difference in the two values? (HINT: Think about the effect of pendulum length on the period.)

Related pages:

• The Galileo Project (A guided tour of Galileo’s life)
• Il Museo della Storia delle Scienze, Firenze  (A science museum in Florence with many artifacts from Galileo)

Aliens From the Fourth-Dimension May Be Invading Our World—And We Don’t Even Know It

Theoretically, it’s impossible for us to perceive a 4D creature. That is, unless it broke into our three-dimensional reality.

The book Flatland: A Romance of Many Dimensions by Edwin A. Abbott explores the concept of physical dimensions through characters who encounter higher-dimensional beings. The protagonist, “A. Square,” lives in a two-dimensional world called Flatland. When the three-dimensional “Sphere” visits him, Square realizes that a whole world exists that he never could have imagined. Eventually, his interactions with Sphere open his mind to the possibility of even higher dimensions.

Higher dimensions are a necessary feature in mathematics as the only way to understand certain concepts. For example, string theory—so far, our best explanation for how the tiniest particles in the universe behave—requires the existence of higher physical dimensions. Otherwise, the behavior of vibrating “strings” that theorists think make up all particles cannot work. Today’s physicists accept the theoretical possibility that our universe started out with as many as 11 dimensions .

Over the years, experiments and mathematical modeling have provided some inkling of four-dimensional characteristics. For example, two-dimensional experiments in both the U.S. and in Europe 2018 showed evidence of a four-dimensional existence because scientists could make logical inferences based on how electrons behave while undergoing a specific change in their electric charge. First, the electrons moved in one direction through an electrically conductive material. When researchers put a magnetic field perpendicular to the material, it forced the electrons to divert either to the left or to the right. The electrons were essentially stuck in two dimensions. Physicists involved in the experiment extrapolated that a comparable effect would occur in the fourth dimension, and that we would see its effects in our familiar third dimension.

In other words, we can see evidence of the fourth dimension in our own. As three-dimensional beings, we cast a two-dimensional shadow. The same principle could be true for four-dimensional beings who could leave traces of themselves in our world. To understand how, let’s start with the basic concept of how different dimensions relate to one another.

As residents of a three-dimensional world, we easily perceive three dimensions: height (or length), width, and depth. We can travel up and down, left and right, and forward and backward. And we know the lower dimensions. The zeroth dimension is a point, which has no height, width, or depth. The first dimension branches out, becoming a line, with length only. Nothing would exist beyond this line to a one-dimensional creature. Two-dimensional shapes, like the characters in Flatland, are what we can draw on paper, like squares and circles. They have both width and length, and they can also travel in these directions. A two-dimensional creature wouldn’t be able to escape the piece of paper they live on, however, because they simply cannot perceive anything other than two dimensions. With the addition of a third dimension, a far richer reality emerges, because now the shape can travel up and down, leaping right off the paper. This is the shape of the universe we know and take for granted.

Now comes the tricky part. To step into higher dimensions, you’re basically making a right angle to the previous shape: first squaring the line for the second dimension, and then cubing the line to reach the third dimension. To step up to the fourth dimension, you need to do the same thing—make a right angle to the cube, extending it into a “ hypercube ,” or tesseract. Four lines connect to every point, and every surface is a cube. Sometimes physicists describe the fourth dimension as a space that’s perpendicular to a cube. (Feeling lost yet?) This description, while geometrically accurate, is not much help—no brain wired for a 3D world can understand what a tesseract or other higher-dimension object actually looks like. So theoretically, we would not be able to perceive a four-dimensional being with our senses—unless they somehow physically accessed our three-dimensional reality.

How would we see aliens from higher dimensions if they entered our three-dimensional world? “Well, it depends on what part of the 4D object is passing through our 3D space,” science communicator Toby Hendy explains. She provides a neat visualization of what it would be like to see a four-dimensional object in our three-dimensional reality on her YouTube channel, Tibees. Supposing there is a four-dimensional ball, Hendy holds out her hand, and a little red ball of yarn pops into existence on it. “Right now, we see a small sphere, because this slice is near the edge of the 4D ball,” she says. As the ball moves through our world, it appears to grow. As it moves out of our plane of existence, it shrinks again, then disappears. “The 4D ball still exists, but our slice of space does not contain it,” Hendy concludes. On the other hand, a 4D being would be able to see the ball and know exactly where it is, she says.

In the same way, an alien from the fourth dimension may pass largely undetected through a “slice” of our three-dimensional universe. Only a part of it would appear, materializing out of nowhere, and then we would see more and more of its parts. But we’d never be able to see all of it at once, because we can’t actually see the fourth dimension with our senses. Finally, it would shrink down to nothing again.

If you can’t quite wrap your head around that (we don’t blame you) then think of it this way: The square in Flatland cannot comprehend the third dimension. So how would it perceive a sphere, a three-dimensional object, invading its two-dimensional plane of existence? Imagine you are the square on the sheet of paper. As the sphere descends onto the sheet in front of you, you start to see a small circle appearing (out of nowhere). This is the leading “slice” of the sphere that’s entering your two dimensions. Gradually, as the sphere continues passing through your two-dimensional plane, the circle—which indicates the diameter of the sphere’s body—gets larger and larger, until the middle of the sphere is fully in your plane. This slice of sphere then shrinks, until nothing is left. At this point, the sphere has traveled completely out of your 2D universe.

For us, that means aliens might be larger than they appear, because we would see only a three-dimensional slice of them at a time. This is exemplified in the games Miegakure and 4D Miner , where you can experience a four-dimensional world through our comprehensible three-dimensional perceptions. So, objects like trees and hills appear and disappear, since our perception of them changes as we move through three-dimensional space. The 4D “hyperspider” predators in 3D Miner are extra menacing because they can move through objects as they hunt us. That’s because a four-dimensional object can slide through gaps that we can’t perceive or access.

Once we hit higher dimensions, it becomes even more difficult to picture what the beings living in there would be like, and how they would interact with our three-dimensional lives. Mathematically, you can keep going with these dimensional iterations, and make cool-looking models. In the end, even models like these four-dimensional shapes are overly simple analogies for a complex reality that’s out of our reach.

So, what would a four-dimensional alien make of us if they visited our three-dimensional reality? Theory suggests they would be able to see inside of us. Just as we can see an array of objects scattered over a two-dimensional surface, all at once from our vantage point in the third dimension, a four-dimensional being would be able to see all of us at once. Kind of creepy.

Perhaps while they are studying us, we have no clue. Based on what we know about physical dimensions, it may be hard to detect an alien spacecraft popping into our space. Could it be that if any UFO sightings are truly related to aliens, they’re hard to prove because the aliens can easily slip away into a higher dimension?

Before joining Popular Mechanics , Manasee Wagh worked as a newspaper reporter, a science journalist, a tech writer, and a computer engineer. She’s always looking for ways to combine the three greatest joys in her life: science, travel, and food.

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August 14, 2024

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Physicists throw world's smallest disco party with a levitating ball of fluorescent nanodiamond

by Purdue University

Physicists at Purdue are throwing the world's smallest disco party. The disco ball itself is a fluorescent nanodiamond, which they have levitated and spun at incredibly high speeds. The fluorescent diamond emits and scatters multicolor lights in different directions as it rotates. The party continues as they study the effects of fast rotation on the spin qubits within their system and are able to observe the Berry phase.

The team, led by Tongcang Li, professor of Physics and Astronomy and Electrical and Computer Engineering at Purdue University, published their results in Nature Communications . Reviewers of the publication described this work as "arguably a groundbreaking moment for the study of rotating quantum systems and levitodynamics" and "a new milestone for the levitated optomechanics community."

"Imagine tiny diamonds floating in an empty space or vacuum. Inside these diamonds, there are spin qubits that scientists can use to make precise measurements and explore the mysterious relationship between quantum mechanics and gravity," explains Li, who is also a member of the Purdue Quantum Science and Engineering Institute.

"In the past, experiments with these floating diamonds had trouble in preventing their loss in vacuum and reading out the spin qubits. However, in our work, we successfully levitated a diamond in a high vacuum using a special ion trap. For the first time, we could observe and control the behavior of the spin qubits inside the levitated diamond in high vacuum."

The team made the diamonds rotate incredibly fast—up to 1.2 billion times per minute! By doing this, they were able to observe how the rotation affected the spin qubits in a unique way known as the Berry phase.

"This breakthrough helps us better understand and study the fascinating world of quantum physics," he says.

The fluorescent nanodiamonds, with an average diameter of about 750 nm, were produced through high-pressure, high-temperature synthesis. These diamonds were irradiated with high-energy electrons to create nitrogen-vacancy color centers, which host electron spin qubits.

When illuminated by a green laser, they emitted red light, which was used to read out their electron spin states. An additional infrared laser was shone at the levitated nanodiamond to monitor its rotation. Like a disco ball, as the nanodiamond rotated, the direction of the scattered infrared light changed, carrying the rotation information of the nanodiamond.

The authors of this paper were mostly from Purdue University and are members of Li's research group: Yuanbin Jin (postdoc), Kunhong Shen (Ph.D. student), Xingyu Gao (Ph.D. student) and Peng Ju (recent Ph.D. graduate). Li, Jin, Shen, and Ju conceived and designed the project and Jin and Shen built the setup.

Jin subsequently performed measurements and calculations and the team collectively discussed the results. Two non-Purdue authors are Alejandro Grine, principal member of technical staff at Sandia National Laboratories, and Chong Zu, assistant professor at Washington University in St. Louis. Li's team discussed the experiment results with Grine and Zu who provided suggestions for improvement of the experiment and manuscript.

"For the design of our integrated surface ion trap," explains Jin. "We used a commercial software, COMSOL Multiphysics, to perform 3D simulations. We calculate the trapping position and the microwave transmittance using different parameters to optimize the design. We added extra electrodes to conveniently control the motion of a levitated diamond. And for fabrication, the surface ion trap is fabricated on a sapphire wafer using photolithography. A 300-nm-thick gold layer is deposited on the sapphire wafer to create the electrodes of the surface ion trap."

So which way are the diamonds spinning and can they be speed or direction manipulated? Shen says yes, they can adjust the spin direction and levitation.

"We can adjust the driving voltage to change the spinning direction," he explains. "The levitated diamond can rotate around the z-axis (which is perpendicular to the surface of the ion trap), shown in the schematic, either clockwise or counterclockwise, depending on our driving signal. If we don't apply the driving signal, the diamond will spin omnidirectionally, like a ball of yarn."

Levitated nanodiamonds with embedded spin qubits have been proposed for precision measurements and creating large quantum superpositions to test the limit of quantum mechanics and the quantum nature of gravity.

"General relativity and quantum mechanics are two of the most important scientific breakthroughs in the 20th century. However, we still do not know how gravity might be quantized," says Li. "Achieving the ability to study quantum gravity experimentally would be a tremendous breakthrough. In addition, rotating diamonds with embedded spin qubits provide a platform to study the coupling between mechanical motion and quantum spins."

This discovery could have a ripple effect in industrial applications. Li says that levitated micro and nano-scale particles in vacuum can serve as excellent accelerometers and electric field sensors. For example, the US Air Force Research Laboratory (AFRL) are using optically-levitated nanoparticles to develop solutions for critical problems in navigation and communication .

"At Purdue University, we have state-of-the-art facilities for our research in levitated optomechanics," says Li. "We have two specialized, home-built systems dedicated to this area of study. Additionally, we have access to the shared facilities at the Birck Nanotechnology Center, which enables us to fabricate and characterize the integrated surface ion trap on campus. We are also fortunate to have talented students and postdocs capable of conducting cutting-edge research. Furthermore, my group has been working in this field for ten years, and our extensive experience has allowed us to make rapid progress."

Journal information: Nature Communications

Provided by Purdue University

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Purdue physicists throw world's smallest disco party - Elmore Family School of Electrical and Computer Engineering - Purdue University

Purdue physicists throw world's smallest disco party

Physicists at Purdue are throwing the world’s smallest disco party.  The disco ball itself is a fluorescent nano diamond, which they have levitated and spun at incredibly high speeds. The fluorescent diamond emits and scatters multicolor lights in different directions as it rotates. The party continues as they study the effects of fast rotation on the spin qubits within their system and are able to observe the Berry phase. The team, led by  Tongcang Li , professor in the Elmore Family School of Electrical and Computer Engineering at Purdue University, published its results in  Nature Communications .  Reviewers of the publication  described this work as “arguably a groundbreaking moment for the study of rotating quantum systems and levitodynamics” and “a new milestone for the levitated optomechanics community.”

“Imagine tiny diamonds floating in an empty space or vacuum. Inside these diamonds, there are spin qubits that scientists can use to make precise measurements and explore the mysterious relationship between quantum mechanics and gravity,” explains Li, who is also a professor in the Department of Physics and Astronomy and a member of the  Purdue Quantum Science and Engineering Institute .  “In the past, experiments with these floating diamonds had trouble in preventing their loss in vacuum and reading out the spin qubits. However, in our work, we successfully levitated a diamond in a high vacuum using a special ion trap. For the first time, we could observe and control the behavior of the spin qubits inside the levitated diamond in high vacuum.”

The team made the diamonds rotate incredibly fast—up to 1.2 billion times per minute! By doing this, they were able to observe how the rotation affected the spin qubits in a unique way known as the Berry phase.

“This breakthrough helps us better understand and study the fascinating world of quantum physics,” he says.

The fluorescent nanodiamonds, with an average diameter of about 750 nm, were produced through high-pressure, high-temperature synthesis. These diamonds were irradiated with high-energy electrons to create nitrogen-vacancy color centers, which host electron spin qubits. When illuminated by a green laser, they emitted red light, which was used to read out their electron spin states.  An additional infrared laser was shone at the levitated nanodiamond to monitor its rotation. Like a disco ball, as the nanodiamond rotated, the direction of the scattered infrared light changed, carrying the rotation information of the nanodiamond.

The authors of this paper were mostly from Purdue University and are members of Li’s research group: Yuanbin Jin (postdoc), Kunhong Shen (PhD student), Xingyu Gao (PhD student) and Peng Ju (recent PhD graduate). Li, Jin, Shen, and Ju conceived and designed the project and Jin and Shen built the setup. Jin subsequently performed measurements and calculations and the team collectively discussed the results. Two non-Purdue authors are Alejandro Grine, principal member of technical staff at Sandia National Laboratories, and Chong Zu, assistant professor at Washington University in St. Louis. Li’s team discussed the experiment results with Grine and Zu who provided suggestions for improvement of the experiment and manuscript.

“For the design of our integrated surface ion trap,” explains Jin, “we used a commercial software, COMSOL Multiphysics, to perform 3D simulations. We calculate the trapping position and the microwave transmittance using different parameters to optimize the design. We added extra electrodes to conveniently control the motion of a levitated diamond. And for fabrication, the surface ion trap is fabricated on a sapphire wafer using photolithography. A 300-nm-thick gold layer is deposited on the sapphire wafer to create the electrodes of the surface ion trap.”

So which way are the diamonds spinning and can they be speed or direction manipulated? Shen says yes, they can adjust the spin direction and levitation.

“We can adjust the driving voltage to change the spinning direction,” he explains. “The levitated diamond can rotate around the z-axis (which is perpendicular to the surface of the ion trap), shown in the schematic, either clockwise or counterclockwise, depending on our driving signal. If we don’t apply the driving signal, the diamond will spin omnidirectionally, like a ball of yarn.”

Levitated nanodiamonds with embedded spin qubits have been proposed for precision measurements and creating large quantum superpositions to test the limit of quantum mechanics and the quantum nature of gravity.

“General relativity and quantum mechanics are two of the most important scientific breakthroughs in the 20th century. However, we still do not know how gravity might be quantized,” says Li. “Achieving the ability to study quantum gravity experimentally would be a tremendous breakthrough. In addition, rotating diamonds with embedded spin qubits provide a platform to study the coupling between mechanical motion and quantum spins.”

This discovery could have a ripple effect in industrial applications. Li says that levitated micro and nano-scale particles in vacuum can serve as excellent accelerometers and electric field sensors. For example, the US Air Force Research Laboratory (AFRL) are using optically-levitated nanoparticles to develop solutions for critical problems in  navigation and communication .

“At Purdue University, we have state-of-the-art facilities for our research in levitated optomechanics,” says Li. “We have two specialized, home-built systems dedicated to this area of study. Additionally, we have access to the shared facilities at the Birck Nanotechnology Center, which enables us to fabricate and characterize the integrated surface ion trap on campus. We are also fortunate to have talented students and postdocs capable of conducting cutting-edge research. Furthermore, my group has been working in this field for ten years, and our extensive experience has allowed us to make rapid progress.”

This research was supported by the National Science Foundation (grant number PHY-2110591), the Office of Naval Research (grant number N00014-18-1-2371), and the Gordon and Betty Moore Foundation (grant DOI 10.37807/gbmf12259). The project is also partially supported by the Laboratory Directed Research and Development program at Sandia National Laboratories.

Source: Purdue physicists throw world’s smallest disco party

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The Physicist Who’s Challenging the Quantum Orthodoxy

July 10, 2023

Jonathan Oppenheim, a physicist at University College London, is developing hybrid theories that could unify classical gravity and quantum mechanics.

Philipp Ammon for Quanta Magazine

Introduction

Most physicists expect that when we zoom in on the fabric of reality, the unintuitive weirdness of quantum mechanics persists down to the very smallest scales. But in those settings, quantum mechanics collides with classical gravity in a resolutely incompatible way.

So for almost a century, theorists have tried to create a unified theory by quantizing gravity, or sculpting it according to the rules of quantum mechanics. They still haven’t succeeded.

Jonathan Oppenheim , who runs a program exploring post-quantum alternatives at University College London, suspects that’s because gravity simply can’t be squeezed into a quantum box. Maybe, he argues, our presumption that it must be quantized is wrong. “That view is ingrained,” he said. “But no one knows what the truth is.”

Quantum theories are based on probabilities rather than certainties. For example, when you measure a quantum particle, you can’t predict exactly where you will find it, but you can predict the likelihood that it will be found in a particular place. What’s more, the more certain you are about a particle’s location, the less certain you are about its momentum. Over the 20th century, physicists gradually made sense of electromagnetism and other forces using this framework.  

But when they tried to quantize gravity, they ran into unnatural infinities that had to be sidestepped with clumsy mathematical tricks.

  The problems arise because gravity is a result of space-time itself, rather than something that acts on top of it. So if gravity is quantized, that means space-time is also quantized. But that doesn’t work, because quantum theory only makes sense against a classical space-time background — you can’t add and then evolve quantum states on top of an uncertain foundation.  

Video : Oppenheim describes why he thinks gravity can’t be squeezed into the same quantum box as the other fundamental forces — and what he’s proposing as an alternative.

Christopher Webb Young/ Quanta Magazine ; Noah Hutton for Quanta Magazine

To deal with this deep conceptual conflict, most theorists turned to string theory, which imagines that matter and space-time emerge from tiny, vibrating strings. A smaller faction looked to loop quantum gravity, which replaces the smooth space-time of Einstein’s general relativity with a network of interlocked loops. In both theories, our familiar, classical world somehow emerges from these fundamentally quantum building blocks.  

Oppenheim was originally a string theorist, and string theorists believe in the primacy of quantum mechanics. But he soon became uncomfortable with the elaborate mathematical acrobatics his peers performed to tackle one of the most notorious problems in modern physics: the black hole information paradox .  

In 2017, Oppenheim started searching for alternatives that avoided the information paradox by taking both the quantum and the classical worlds as bedrocks. He stumbled across some overlooked research on quantum-classical hybrid theories from the 1990s, which he’s been extending and exploring ever since. By studying how the classical and quantum worlds interrelate, Oppenheim hopes to find a deeper theory that is neither quantum nor classical, but some kind of hybrid. “Often we put all our eggs in a few baskets, when there are lots of possibilities,” he said.  

To make his point, Oppenheim recently made a bet with Geoff Penington and Carlo Rovelli — leaders in their respective fields of string theory and loop quantum gravity. The odds? 5,000-to-1. If Oppenheim’s hunch is correct and space-time isn’t quantized, he stands to win bucketloads of potato chips, colorful plastic bazinga balls , or shots of olive oil, according to his fancy — as long as each item costs at most 20 pence (about 25 cents).

We met in a north London café lined with books, where he calmly unpacked his concerns about the quantum gravity status quo and extolled the surprising beauty of these hybrid alternatives. “They raise all kinds of remarkably subtle questions,” he said. “I’ve really lost my feet trying to understand these systems.” But he perseveres.  

“I want my 5,000 bazinga balls.”

The interview has been condensed and edited for clarity.

Why are most theorists so sure that space-time is quantized?

It’s become dogma. All the other fields in nature are quantized. There’s a sense that there’s nothing special about gravity — it’s just a field like any other — and therefore we should quantize it.

Oppenheim and his students, seen here in and around the UCL campus, are developing a new class of hybrid quantum-classical theories in which gravity stays classical. Maybe, Oppenheim argues, gravity is special and the quantum consensus is wrong.

Is gravity special in your view?

Yes. Physicists define all the other forces in terms of fields evolving in space-time. Gravity alone tells us about the geometry and curvature of space-time itself. None of the other forces describe the universal background geometry that we live in like gravity does.

At the moment, our best theory of quantum mechanics uses this background structure of space-time — which gravity defines. And if you really believe that gravity is quantized, then we lose that background structure.

What sorts of problems do you run into if gravity is classical and not quantized?

For a long time, the community believed it was logically impossible for gravity to be classical because coupling a quantum system with a classical system would lead to inconsistencies. In the 1950s, Richard Feynman imagined a situation that illuminated the problem: He began with a massive particle that is in a superposition of two different locations. These locations could be two holes in a metal sheet, as in the famous double-slit experiment. Here, the particle also behaves like a wave. It creates an interference pattern of light and dark stripes on the other side of the slits, which makes it impossible to know which slit it went through. In popular accounts, the particle is sometimes described as going through both slits at once.

But since the particle has mass, it creates a gravitational field that we can measure. And that gravitational field tells us its location. If the gravitational field is classical, we can measure it to infinite precision, infer the particle’s location, and determine which slit it went through. So we then have a paradoxical situation — the interference pattern tells us that we can’t determine which slit the particle went through, but the classical gravitational field lets us do just that.

But if the gravitational field is quantum, there is no paradox — uncertainty creeps in when measuring the gravitational field, and so we still have uncertainty in determining the particle’s location.

So if gravity behaves classically, you end up knowing too much. And that means that cherished ideas from quantum mechanics, like superposition, break down?

Yes, the gravitational field knows too much. But there’s a loophole in Feynman’s argument that could allow classical gravity to work.

What is that loophole?

As it stands, we only know which path the particle took because it produces a definite gravitational field that bends space-time and allows us to determine the particle’s location.  

But if that interaction between the particle and space-time is random — or unpredictable — then the particle itself doesn’t completely dictate the gravitational field. Which means that measuring the gravitational field will not always determine which slit the particle went through because the gravitational field could be in one of many states. Randomness creeps in, and you no longer have a paradox.

So why don’t more physicists think gravity is classical?

Well, it is logically possible to have a theory in which we don’t quantize all the fields. But for a classical theory of gravity to be consistent with everything else being quantized, then gravity has to be fundamentally random. To a lot of physicists that’s unacceptable.

Oppenheim started out as a string theorist, but he eventually grew frustrated with the clumsy mathematical tricks his colleagues employed to get around one of the most notorious conundrums in physics: the black hole information paradox.

Physicists spend a lot of time trying to figure out how nature works. So the idea that there is, on a very deep level, something inherently unpredictable is troubling to many.

The outcome of measurements within quantum theory appears to be probabilistic. But many physicists prefer to think that what appears as randomness is just the quantum system and the measuring apparatus interacting with the environment. They don’t see it as some fundamental feature of reality.

What are you proposing instead?

My best guess is that the next theory of gravity will be something that is neither completely classical nor completely quantum, but something else entirely.

Physicists are only ever coming up with models that approximate nature. But as an attempt at a closer approximation, my students and I constructed a fully consistent theory in which quantum systems and classical space-time interact. We just had to modify quantum theory slightly and modify classical general relativity slightly to allow for the breakdown of predictability that is required.

Why did you start working on these hybrid theories?

I was motivated by the black hole information paradox. When you throw a quantum particle into a black hole and then let that black hole evaporate, you encounter a paradox if you believe that black holes preserve information. Standard quantum theory demands that whatever object you throw into the black hole is radiated back out in some scrambled but recognizable way. But that violates general relativity, which tells us that you can never know about objects that cross the black hole’s event horizon.

But if the black hole evaporation process is indeterministic then there’s no paradox. We never learn what was thrown into the black hole because predictability breaks down. General relativity is safe.

Recently, Oppenheim made a 5,000-to-1 bet with two colleagues that gravity can’t be quantized. If he wins, he gets to stuff his pockets with 5,000 bags of potato chips or bazinga balls or anything else that suits his fancy — as long as each item costs at most 20 pence (about 25 cents). “I feel I’ve made a pretty safe bet, even if I lose,” Oppenheim said.

So the noisiness in these quantum-classical hybrid theories allows information to be lost?

But information conservation is a key principle in quantum mechanics. losing this can’t sit easily with many theorists..

That’s true. There were huge debates about this in recent decades, and almost everybody came to believe that black hole evaporation is deterministic. I’m always puzzled by that.

Will experiments ever resolve if gravity is quantized or not?

At some point. We still know almost nothing about gravity on the smallest scales. It hasn’t even been tested to the millimeter scale, let alone to the scale of a proton. But there are some exciting experiments coming online which will do that.

One is a modern-day version of the “Cavendish experiment,” which calculates the strength of the gravitational attraction between two lead spheres. If there is randomness in the gravitational field, as in these quantum-classical hybrids, then when we try and measure its strength we won’t always get the same answer. The gravitational field will jiggle around. Any theory in which gravity is fundamentally classical has a certain level of gravitational noise.

How do you know this randomness is intrinsic to the gravitational field and not some noise from the environment?

You don’t. Gravity is such a weak force that even the best experiments already have a lot of jiggle in them. So you have to eliminate all these other sources of noise as much as possible. What’s exciting is that my students and I showed that if these hybrid theories are true, there must be some minimal amount of gravitational noise. This can be measured by studying gold atoms in a double-slit experiment. These experiments already place bounds on whether gravity is fundamentally classical. We are gradually closing in on the amount of indeterminacy allowed.

On the flip side of the bet, are there any experiments that would prove that gravity is quantized?

There are proposed experiments that look for entanglement mediated by the gravitational field. As entanglement is a quantum phenomenon, that would be a direct test of the quantum nature of gravity. These experiments are very exciting, but probably decades away.

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Living Reviews in Relativity: “Gravity experiments with radio pulsars”

• by Frank Schulz
• 2024/08/14 2024/08/15

The open-access journal Living Reviews in Relativity has published a new review article on 22 July 2024:

Paulo C. C. Freire and Norbert Wex, Gravity experiments with radio pulsars. Living Rev Relativ 27, 5 (2024). https://doi.org/10.1007/s41114-024-00051-y

Abstract: The discovery of the first pulsar in a binary star system, the Hulse-Taylor pulsar, 50 years ago opened up an entirely new field of experimental gravity. For the first time it was possible to investigate strong-field and radiative aspects of the gravitational interaction. Continued observations of the Hulse-Taylor pulsar eventually led, among other confirmations of the predictions of general relativity (GR), to the first evidence for the reality of gravitational waves. In the meantime, many more radio pulsars have been discovered that are suitable for testing GR and its alternatives. One particularly remarkable binary system is the Double Pulsar, which has far surpassed the Hulse-Taylor pulsar in several respects. In addition, binary pulsar-white dwarf systems have been shown to be particularly suitable for testing alternative gravitational theories, as they often predict strong dipolar gravitational radiation for such asymmetric systems. A rather unique pulsar laboratory is the pulsar in a hierarchical stellar triple, that led to by far the most precise confirmation of the strong-field version of the universality of free fall. Using radio pulsars, it could be shown that additional aspects of the Strong Equivalence Principle apply to the dynamics of strongly self-gravitating bodies, like the local position and local Lorentz invariance of the gravitational interaction. So far, GR has passed all pulsar tests with flying colours, while at the same time many alternative gravity theories have either been strongly constrained or even falsified. New telescopes, instrumentation, timing and search algorithms promise a significant improvement of the existing tests and the discovery of (qualitatively) new, more relativistic binary systems.

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