The speed of light is very fast, as you know. It slows down a bit when it (i.e. the photons it's made of) bump into atoms in our air. Based on Einstein's work, we now think that the speed of light is the maximum speed that any object with or without mass can go.
Do you understand mass? You may know it as weight, but that is only on Earth. Mass exists everywhere! We use mass constantly to calculate important things to understand our world. When we push on something, our Force equals mass times the acceleration of the thing (F=ma). When something is moving, it has a certain momentum that keeps it moving based on its mass and velocity (momentum = mass x velocity). So we use mass all the time. In gravity like here on Earth, mass is the same as weight. Two objects with mass attract each other with gravity. Our planet has a lot of mass so it attracts all of us and gives us weight. All of the things that we live with, like cars and airplanes, travel at far less than the speed of light because of their mass.
We don't understand why the speed of light is the fastest speed that anything can go. We may learn that as we learn more about physics. It has something to do with how our world is built, but we don't fully understand it yet. If you learn as much as you can about physics, then maybe you can help us understand more about our world!
How can an object not have mass?
ReplyDeleteThe answer depends a little bit on what you mean by "an object". All of the things that we normally think of as objects certainly do have mass. But there are a few very important "objects" that do not have any mass. The most familiar one is the photon. Objects without mass can travel at exactly the speed of light - which makes sense since photons are light!
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