20 Weird Physics Facts for Kids
Science

20 Weird Physics Facts for Kids (AND Curious Adults!)

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Physics is a fascinating subject. It’s all about explaining why things happen the way they do. As you learn more, you realize that the world is even more amazing and fantastic than you ever imagined. Here are 20 weird and wonderful physics facts that will get anyone excited and hooked on learning more.

Related post: Physics Experiments For Kids [7 Awesome Ideas]

#1 Grapes are Magnetic

One of the first science experiments we’ve all done in elementary school uses a magnet. You see what sticks to the magnet to find out what’s magnetic and what isn’t. Since the list of magnetic things is pretty short, it’s quite easy to remember – items made from iron or steel are magnetic, and everything else isn’t. Except that’s not the whole story.

This test lets you find which objects are ferromagnetic. But that’s not the only type of magnetism. It is the strongest type, though, which is why it’s easy to observe. But, if you hang a grape from a string, then use a strong magnet, you find that the magnet can move the grape. It turns out that everything is magnetic. It’s just that some things are more or less magnetic than others. If the magnetic effect is small, it can be hard to see.

Courtesy Exploratorium (CC BY-NC-SA 4.0)

#2 Light Move Slowly Inside the Sun

One of the most critical features of light is that it’s fast – VERY fast. In fact, nothing in the universe can travel faster than the speed of light.`

It takes about 8 minutes for light from the sun to travel approximately 93,000,000 miles (150,000,000 km) to reach the Earth. So you might find it hard to believe that it takes longer for it to cross the shorter distance of 440,000 miles (700,000 km ) from the center of the sun to the edge. In fact, it takes a lot longer – around 100,000 years.

Why does this happen? Well, the speed of light isn’t constant. Just like a car can go faster on a road than it can on sand, some materials slow light down. That’s why things look different underwater. The denser the material, the more the light is slowed down. It takes so long for a photon to travel through the sun because it’s really densely packed.

#3 The Sun is Much Bigger Than You Think

Sun

Models of the solar system are fun to make. However, I do have a bone to pick. Even when you get the distance to scale, something that’s almost always forgotten is to represent the size difference between the sun and the planets. Hopefully, you all know that the sun is much bigger than the planets that orbit it. But, do you know how much bigger it is?

99.8% of the mass of the solar system is taken up by the sun. Its diameter is about 109 times larger than the Earth’s. That might not sound like that much, but it means you could fit around 1 million planet Earths inside the sun.

For a scale model, if you used a marble to represent the Earth, you’d need a ball the same height as Dolly Parton to be the sun. If you want to get a feel for the scale of things on the universe this is a great tool for doing just that.

#4 We Can Observe Less Than 5% of the Stuff in the Universe

Scientists have spent a long time studying the universe. We know an awful lot about the elements, light, electricity, and even the stars. But, it turns out that despite all the time spent studying the universe, we’ve only been looking at a tiny percentage of it.

The matter we’re made of and the things we can see and measure only represent a fraction of the ‘stuff’ in the universe. Around 95% of the universe is made up of Dark Matter and Dark Energy. This is matter that we can’t see or touch.

If you’re wondering how we know it’s even there if we can’t see it, then you’re thinking like a physicist. That’s a great question. We know it’s there because it affects the way that galaxies move. We can measure the speed at which galaxies spin and calculate how much mass there should be. It turns out there is a lot more than we can account for.

So despite all our hard work, we’ve only just begun to learn about the world we live in. Isn’t that awesome!

#5 Antimatter is Real

Have you ever watched a science fiction show where they talk about antimatter? Surprisingly, antimatter isn’t fictional. It’s a real thing. We can make antimatter particles. It’s tough, though, because if antimatter touches matter, it goes through a process called annihilation.

Antimatter is a little like the opposite of matter. All the fundamental particles have antimatter equivalents. For example, the antimatter partner to an electron is a positron. There are only two differences between a particle and its antimatter ‘twin’. An antimatter particle will be almost identical except for having the opposite charge and spin.

At the beginning of the universe, there were large amounts of both matter and antimatter. When the universe cooled down a tiny bit, all the matter and antimatter began to annihilate. Fortunately, there was a tiny bit more matter than antimatter. Everything in the universe today is made up of this little bit of extra matter formed at the very beginning of the universe.

Universe in a person's hands

#6 There is a Serious Theory that Electrons Travel Through Time

One of the wonderful things about physics is that it requires a lot of creative thinking. Explaining how and why things happen the way they do isn’t easy. Theoretical Physicists develop theories and ideas about what is happening to the particles that make up the universe.

Electrons are one of the most fundamental particles in the universe. Despite all our study of them, there’s still a lot we don’t understand about them. The fact that they all appear to be absolutely identical led one physicist to suggest that there might only be one electron in the whole universe. It just moves in a different plane than we can, and each time it crosses our plane, we see it as a new electron.

This theory led Richard Feynman (a very famous and respected scientist) to suggest that perhaps the difference between electrons and positrons is the direction they move through time. Electrons go forwards, and positrons go backward.

#7 The Expansion of the Universe is Speeding Up

One of the most critical pieces of evidence for the big bang theory is that the universe is getting bigger. If you think of the big bang as an explosion, then the universe is expanding because it was all pushed away by the ‘bang’.

We can tell that this is happening by looking at the light from far away stars. But something the big bang theory can’t explain is why the expansion of the universe appears to be getting faster. We can tell it’s happening, but no one is quite sure why. A lot of astrophysicists think that it might have something to do with dark matter. It’s one of the biggest questions in physics today.

#8 When Protons Collide in the LHC, They Have the Same Energy as a Train Collision

The Large Hadron Collider is one of the biggest particle accelerators in the world. It’s a machine used to accelerate tiny particles to around 99.991% the speed of light. The particles then crash together and release a lot of energy as well as interesting new particles.

Protons, the things inside the nucleus of an atom, are used in this fantastic machine. When they collide together, they have the same energy as two 400 ton trains traveling at 150km/h would. It’s so much energy that, for a moment, the point of the collision is hundreds of times hotter than the sun.

#9 Electrons Behave Differently if You Watch Them

Have you ever tried to type while someone is watching you? Do you suddenly find that you make way more mistakes than usual? I know I do. Sometimes when we’re being watched, we find ourselves behaving differently. It turns out electrons do the same thing.

If you fire a stream of electrons through two small holes, they’ll make a special pattern with lots of lines on the other side. Scientists wanted to know what was happening to cause this pattern. So they set up detectors to measure which of the holes the electrons were going through. But as soon as they did that, the electrons no longer formed the pattern. Half went through one hole, half went through the other, and that was it.

So, by just observing what the electrons were doing, the scientist caused them to behave differently. This is an example of just how strange and fascinating quantum physics is.

#10 You are Mostly Empty Space

Our bodies are made up of atoms. Atoms can be thought of as a nucleus with electrons orbiting around it. You might not realize that the gap between the core and the orbiting electrons is (comparatively) huge. Most of an atom is just empty space.

If we were to take the terrifying step of removing all the empty space in all the atoms in all the humans on Earth – we could fit what was left inside a single sugar cube.

Of course this idea is only true, as long as you’re looking at the electrons that make up your atoms. When we’re not looking they stop acting like small particles and instead act like waves, which means they are in fact in every bit of all that ‘empty space’ all the time.

#11 Everything Falls at the Same Speed

This is an idea that a lot of people struggle to get their heads around. An object’s weight does not affect the rate at which it falls. Heavy things don’t fall faster than light things.

Only two things affect the rate at which an object will fall – gravity and air resistance. If you take away air resistance, you will find that a feather and a bowling ball take the same amount of time to reach the ground.

#12 Substances Can Melt, Freeze, And Boil All At The Same Time

For all pure substances, you can take them through state changes by either changing their temperature or their pressure. For instance, if you start with a solid and warm it up, it will first melt and then boil. You can achieve the same effect by increasing the pressure on it but keeping the temperature the same.

As a result, you can change the temperature at which a substance melts or boils by adjusting the amount of pressure it’s under. If you get it just right, you can change things so that the melting and boiling points are the same temperature. This is called the triple point. At this point, the substance will instantly switch between a solid, a liquid, and a gas.

Some materials can exist in even more than these three states. So it’s actually possible to find some materials, like helium, which can simultaneously be in four different states. In this case, it’s called a lambda point.

#13 Cats Always Land on Their Feet Because They Use Physics!

Most people would agree that cats are very good at landing on their feet. They’re not the only animals that can do this. Squirrels, for instance, are also good at landing on their feet when they fall. What’s really interesting is how they manage to do it.

If you’ve ever done any gymnastics, then you might know that once you start turning in the air, it’s hard, if not impossible, to change direction. This is due to the conservation of angular momentum. This basically means that you can’t change the amount of turning in a system without applying an outside force. But there are some tricks you can use to alter your angular momentum once you start turning.

For instance, ice skaters do this all the time. If they start spinning, they can change the speed of their spin without having to push on the ice again. Putting their arms out slows the spin. Pulling them in speeds it up. You can do this in a spinny chair as well.

Cats rotate their bodies in two halves. They pull in their arms to make their font half-turn towards the ground quickly while stretching out their legs, so it only turns a tiny amount in the opposite direction. This keeps the amount of turning unchanged. Then they stretch out their arms and tuck in their legs to turn their back feet to the ground. Finally, they stretch all their legs out to brace for landing.

What’s really impressive about this is that it’s a reflex action. Cats are born with the ability to perform this complicated maneuver. They don’t even have to learn the physics behind it!

#14 The Eiffel Tower Grows in the Summertime

The Eiffel Tower is undeniably the symbol of Paris. It was only ever intended to be a temporary structure, though. When it was first built in 1889, the plan was to pull it down after 20 years. However, it became so popular and was used for so many landmark scientific experiments that when it came time to pull it down, the French government had a change of heart.

Another fascinating thing to know about the Eiffel Tower is that it changes size depending on the time of year. During the summertime, it is as much as 6 inches taller than it is during the winter. This is because metals change size depending on the temperature. They expand in heat and contract in the cold.

The engineers who built the Eiffel Tower had to design it to allow this growth to happen. If they hadn’t done so, all the joints would have weakened over time until the whole structure fell down.

#15 Looking at the Stars is Like Looking Back in Time

The universe is a pretty fascinating place. One of the most important things about it is that it’s enormous. It’s unimaginably big. If you think you can imagine how big it is, you’re wrong – it’s even bigger. I mention this because it explains why looking into the night sky is the same as looking back in time.

The universe is so big that the light from the stars we can see took a long time to get to us. Let’s just think about our nearest stars (other than the sun). Alpha Centauri is a collection of three stars that’s 4.3 light-years away. So when you look up at Alpha Centauri, you’re seeing it as it looked 4.3 years ago. If you could press a button to make it turn purple, you’d have to wait over four years to see if it worked.

The further away the star, the further back in time you’re looking.

It’s only because the universe is so big that it actually gets dark at night. There are so many stars in the universe that there is at least one in every single direction you can look. But, thankfully, many are so far away that their light hasn’t reached us yet. That’s why there are dark spots in the night sky.

Here’s one last little mind-bender to leave you with. Some stars have been born, gone through their entire millennia-long lifecycles, and burnt out. But their light still hasn’t reached us yet. So by the time, we can see them, they’ll already be gone.

#16 You Can’t Burp in Space

The reason you burp is that the gas you’ve ingested separates from the solids and liquids inside your stomach. It rises to the top and can leave through your mouth. For this to happen, you need one essential ingredient – gravity.

You don’t have to go that far into space to experience this. Astronauts on the International Space Station can tell you all about it. The downside to being unable to burp is that all that gas still has to leave your body somehow…

#17 You Can Only See 2 Dimensions

We live in a three-dimensional world. That means that we and everything we experience has length, depth, and thickness. But our eyes are only capable of seeing 2 dimensions.

The light that enters your eye hits the retina at the back. This forms an image of whatever you’re looking at. But it’s only an image. The information your eye sends to your brain is essentially completely flat. We can see depth because our brain uses the slight differences in what each eye sees to turn the 2D information into a 3D image.

Your eyes are placed so that they get overlapping views of the world. It is this that gives us, and all other hunting animals, our depth perception.

#18 Every Time You Shuffle a Deck of Cards, You Are the First Person in History to Put Them in That Order

Math and probability are prominent features of physics. Which is my excuse for sharing this unbelievable but true fact with you.

If you play card games, you know how important it is to give the cards a good shuffle. After all, you’re aiming to get the cards into a random order. If you shuffle the cards properly to get them into a new order, it will be the first time in history that anyone has put a deck of cards in that order. Seriously.

This is because, with 52 cards, you can put them into a lot of different orders. To figure out how many, you need to do a little bit of math. For the first card, there are 52 options; for the second card, there are 51 options; for the third card, there are 50 options. I’m sure you get the idea. To find the total number of options, you multiply these numbers together – 52 x 51 x 50 …. This is called 52 factorial or 52!. It’s a BIG number. It’s an 8 followed by 67 zeros.

Because there are so many ways that you can sort a deck of cards. It means that it’s almost impossible that in the history of the world, anyone else will have ever shuffled a deck of cards into the same order.

What’s a ‘good’ shuffle?

I can already hear the clamoring masses wanting to know the proper definition of a good shuffle. Well, mathematicians far smarter than I have taken the time to calculate what makes a perfect shuffle. If you can do a riffle, you need to do 7 riffles to get a genuinely random deck. Alternatively, you can put all the cards face down on the table and mix them up; that works too.

#19 Physics Can Make a Chain Jump Out of a Container!

There is a very cool phenomenon called a chain fountain, or the Mould effect. It’s a phenomenon where you coil up a chain inside a container. Then you pull one end out and let it drop to the floor. This will pull the rest of the chain out of the box. But the chain doesn’t just run over the edge. It, in fact, leaps up and over the edge instead.

The reason this happens is mathematically pretty complicated. But if you can imagine that each link is like a seesaw. If you pull one end of the seesaw up, the opposite end moves down. The links in the chain are a little like that. However, when you lift one side of the chain, the other end can’t go down because it’s sitting on the rest of the chain. Instead, it experiences an upward reactionary force. It’s this upward force that ultimately propels the chain fountain.

#20 Gravity is The Weakest of All the Forces

Gravity, the force that keeps our feet on the ground, is actually pretty weak. When you think about it, it’s incredible just how weak it really is. The gravity we experience is due to the mass of the planet we live on. The entire mass of the planet acts together to cause the gravitational force we all feel. But, a fridge magnet is strong enough to overcome it.

The problem of how weak gravity is a wonderful example of just how strange physics can be. We can use physics to predict precisely what gravity will do and how it will affect objects. But, we don’t understand what it is or how it really works.

Compared to other forces in the universe, gravity is 10^40 times smaller. This difference in size is so confounding to physicists that it’s got its own name. It’s called the hierarchy problem. If you want to learn more about it, there is an excellent discussion in a book called Knockin On Heaven’s Door, that I heartily recommend.

Frequently Asked Questions

How do you get kids interested in physics?

One of the best ways to get kids interested in physics is to expose them to it. Talk about it, ask questions, and puzzle out the answers with them. If you’re enthusiastic about a subject, your kids will pick up on that and want to know more.

Isn’t physics hard?

A lot of people seem to think that physics is the hardest out of the scientific disciplines. But I think that’s unfair. It’s fascinating, interesting, and surprising. Just learning some of these fun physics facts should give you a taste of how interesting it is.

Admittedly if you want to study physics academically, you’re going to need to be really good at math. But, to learn about what’s going on and why you just need a curious mind.

What’s interesting about physics?

Everything! Except for the space stuff, that’s a bit dull if you ask me. Physics is all about understanding why things happen. The answer isn’t always what you think it’s going to be either. The more you learn about physics, the more you realize that the universe is a really odd place, which is truly incredible. You’ll also find out that there’s so much we don’t know yet, so there’s still a lot to explore.

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