Simce all these comments are very long. I’ll give an actual ELI5. Basically, as you speed up, the universe tries to make sure the speed of light is the same for you as for everyone else. To do this, if you are going really fast, the rest of the universe has to speed up to make sure light looks the same for you. No matter how fast you go, the universe will always just speed up for you.
To other people looking at you, you move slower and slower, (so the opposite effect). If you were to somehow reach light speed, you would just be frozen in time.
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