Hello, I'm new to this forum and come here with a simple question. I am just starting to understand special relativity and read up on the Twin Paradox which overloaded my wtf-o-meter. Basically from what I understand is that time does not progress at the same rate everywhere, the rate at which time progresses from one person's perspective relative to another's depends on each person's velocity relative to the speed of light (?) So if someone leaves earth traveling at the speed of light, comes back later at the speed of light, they will have aged more slowly than the people on earth. So if twins are born on earth, and one travels to the nearest star and back at almost the speed of light, the travelling twin will be 5 years old but the earth twin will be 10 years old at the time they meet again. Not just an illusion, they will actually be different ages. I understand that this is fact, but can somebody please explain why. More fundamentally, what exactly is time and what physically causes time to progress? Why is the rate of time different in different places and why does the speed of light have anything to do with anything? Can someone please help me understand? If you can explain without having to use math more advanced than basic calculus (I have 2 quaters under my belt) that would be ideal. Thanks ahead of time!