the special theory of relativity
Light Spectrum
Special Relativity is easier to understand than the general theory, but not as applicable in real life. It says that motion is relative to your perspective of viewing. For example, if you are reading this on your computer, your computer appears as if it’s still, but someone viewing the earth you are one is moving. Another example is if you were riding a train, people outside of the train would see you and the train move by very fast, but from the inside,you look like y4ou are standing still. In both cases, your perspective determines whether or not you believe you are moving.
The other thing the special theory of relativity covers is that the speed of light is always the same, no matter what you do to it. While I've given every day examples, this mainly applies to the speed of light. Say you were traveling at 90% the speed of light in a clear spaceship out in space. You would see stars ahead of you blue shifted, which is having its color appearing to be closer to the blue end of the spectrum (see picture), and if it was already close to the end, it would pass into the invisible spectrum. The opposite would happen with the stars behind you, except they would be closer to the red side of the spectrum, or be red shifted.
The other thing the special theory of relativity covers is that the speed of light is always the same, no matter what you do to it. While I've given every day examples, this mainly applies to the speed of light. Say you were traveling at 90% the speed of light in a clear spaceship out in space. You would see stars ahead of you blue shifted, which is having its color appearing to be closer to the blue end of the spectrum (see picture), and if it was already close to the end, it would pass into the invisible spectrum. The opposite would happen with the stars behind you, except they would be closer to the red side of the spectrum, or be red shifted.
Blue shifting and red shifting happens because you are going along with the light. Because of you going at this speed and seeing stars blue shifted, you are essentially seeing into the future (see diagram). A simpler explanation would be with sound. If you stood by train tracks, you would hear the whistle of a train at different pitches based on its position relative to you.