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What is gravity, and how does it keep us stuck to the ground?

Fun Science: Forces Of Nature

Professor Gizmo (Amazing Science Presentations) gives expert video advice on: What is static electricity, and why does it make my hair stand up?; Why do we get a shock from electricity?; What are the different types of matter? and more...


Well, gravity is a force between two objects. It's like an attraction where the larger object, in this case would be earth, has to force or pull on other objects, and it keeps them attached to and connected to the earth.


Static electricity is fun. Why does your hair stand up when you take your hat off? Static electricity is a gain of, or a loss of, electrons. When something rubs against something else, those objects will either gain electrons or lose electrons. When you put your hat on, or you take your hat off, sometimes this causes this charge. When you take your hat off, a charge builds up, and it tries to get away from your body. Electrons are trying to get away, and they're going through your hair, which makes your hair stand up on end. Once I was out in the mountains and a storm was approaching. We were at a lookout area on the top of a mountain. I looked around and my whole family's hair was standing on end. It was because the electrons in the earth were trying to come through us and out again. There was a positive charge in the sky. That is a pretty good sign that lightening is going to strike. So, when I noticed this, we got out of the way, because that little signal from static electricity told us that there was a very strong charge in the area, and we had better move.

What is an "electron"?

An electron is a part of an atom. It's one of the parts of the atom that spins around the outside, and these electrons can be shared and moved. What happens with static electricity is, some of these electrons build up in one object and are lost in another object. That difference in charge between one atom with electrons and another atom with electrons will either cause these to be drawn together if the charge is different, or if both charges are the same, they repel, and they push apart.

Why do we get a shock from electricity?

A lot of times some of the electric current in an object builds up and it is looking for a way to get out. If we form the connection between a positive and a negative and our body is that connection, we can get a shock from it. So, sometimes when you reach out and touch something, you get a shock. This is because the electricity is basically going through whatever object you are touching, jumping to your finger and then through your feet and down to the ground.

What is a "sonic boom"?

A sonic boom is when some object, usually an aircraft that's going as fast as the speed of sound, builds up all these sound waves in front of it. When the plane or rocket goes through that, it creates this burst of energy, and behind it is this sonic boom because the object has gone through this buildup of sound waves out in front of the aircraft.

What is "absolute zero"?

Absolute zero is really really cold. It's 459 degrees below zero. That's cold, and it's defined as absolute zero because they don't think things can get any colder. Absolute zero is the temperature when molecules stop moving, and it's very very difficult even to get close to that temperature. It's very cold.

How fast is faster than the speed of light?

The speed of light is 186,000 miles per second, and I don't know of anybody or anything that's gone actually faster than the speed of light. There's theories that say as you approach the speed of light time slows down. They even did experiments where they would take an airplane, and a very fast jet and fly around the Earth a couple of times, and what they tried to do is measure the time on Earth, and the time on the airplane that was going very fast, and there were fractions of a second difference. Now that doesn't seem like much, but the airplane didn't go anywhere near 186,000 miles per second. So the speed of light is the time it takes light to travel, and it's extremely fast.

What is "evaporation"?

Evaporation is a process where a liquid changes to a gas. Evaporation -like water, for instance - when it rains outside, you don't have to go outside and clean up the rain because it evaporates. It changes from a liquid into a gas and evaporation is actually a cooling process. So when we get hot in the summer and we're running around, do you notice we sweat a lot? That's because our bodies are producing this moisture on our skin and that moisture then evaporates. And evaporation is a cooling process because needs energy to do so and it makes our bodies cooler.

Does the "theory of relativity" have anything to do with my family?

No, the theory of relativity has nothing to do with your family; it's all about my family... No, the theory of relativity is a theory that states that energy and matter is related and you're not going to lose one or gain one but they're related. So, it has nothing to do with your family or family history. It is a theory that was proposed by Albert Einstein.

What are the different types of matter?

Different types of matter, there's solids, liquids and gases. Solids are a type of matter that take up a definite shape and amount of space. A liquid is similar to that except it doesn't keep it's shape. It will take the shape of the container it's in. A gas is similar to that also, but a gas will always fill it's container. No matter how much you put in there. You have a totally empty container, it's a vaccuum, you put a little bit of gas in there it will fill a container, you put a lot of gas in there, it will fill a container. So, you have three types of matter. Solids, liquids and gases.