Going Insane
Like many of you, I have been cooped up in my house while avoiding the global health crisis. However, I seem to have had ten times as much schoolwork out of school than I did while I was still in school. Physics is probably my favorite subject, and I wanted to share some of the crazy things that I have been learning.
Why does light bend?
Take a clear glass of water, and stick a pencil in it. If you look at it from the side, you will probably see that it looks like it is cut off or bends at a weird angle. Why is that? In a vacuum (empty space with no air particles to get in the way) light always travels at 299,792,458 meters per second. That is extremely fast, about 671,000,000 miles per hour. In different materials, light travels slower. Just like you would run slower through a forest than you would through a field, light travels slower through objects made up of particles than it does through empty space.
Here is a short video I made demonstrating how the speed of a car can change its path:
When light hits a boundary between these different “mediums,” half of the beam will reach the slower medium before the other half. This causes the beam to bend away from a straight line. If the beam enters a slower material, it will “refract” towards the “normal,” which is an imaginary line that is perpendicular to the boundary. If the beam speeds up in the new medium, it will refract away from the normal.
What’s so special about special relativity?
I wrote earlier that light travels at 299,792,458 meters per second. Not only does light travel at this speed in a vacuum, but it travels at this speed no matter where you are measuring it from. If I was running at you at 4 m/s and then threw a baseball at you at 10 m/s, you would see the ball coming at you at 14 m/s. However, this starts to change with extremely high velocities.
If a spaceship was traveling toward you at 1/2 the speed of light and shined a flashlight at you, the light from the flashlight will still travel at exactly the speed of light, not one and a half times the speed of light. The person on the spaceship will also see the light from the flashlight traveling away from them at the speed of light. Because both people have to measure the same speed for light, time and space themselves bend to make the math work out. This video uses an illustration involving a train to show how time and space change with speed.
Conclusion
Light, time, and space do some crazy things. While you are sitting on your couch doing your part to save the world, take some time to keep your brain moving. The internet has a ton of resources that can help you learn a whole bunch of amazing things. Whether it is the finer points of special relativity or a new way to make a sandwich, learn something new every day and we’ll be out of this social distancing in no time.
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