Hello! I have looked at this forum a number of times but haven't been quite able to understand something. I took intro physics in college and although I accept the theories of general and special relativity, I never quite understood *why* some aspects of it work.(adsbygoogle = window.adsbygoogle || []).push({});

Please bear with me--I'll use an example similar to some that I've read.

Suppose Bert is traveling toward Alpha Centauri at near the speed of light (c). Let's say his velocity is 0.999c. Bert's friend Ernie is waiting back at Earth for Bert's return. Alpha Centauri is about 4.37 light years from Earth. So, from Ernie's perspective, it takes Bert nearly 8.75 years to travel to and from Alpha Centauri. However, from Bert's perspective, the trip only takes less than 5 months.

I understand and believe that this is true, but I have a question. If Bert is traveling at 0.999c, how does he travel that distance (8.269X10^13 km) in less than 5 months? Does the distance change from Bert's perspective? If not, I don't understand how he travels that distance in that time. I know it must be something simple that I am missing, but I can’t figure it out on my own.

Any help understanding this or directing me toward a good book or website would be much appreciated. A friend has offered a book by Nigel Calder, I think called "Einstein's Universe"... has anyone read this?

Thanks!

Zambi

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# Relativity question

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