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Questions tagged [special-relativity]

Questions regarding Albert Einstein's theory that posits, among other things, the equivalence of mass and energy.

In 1905, Albert Einstein published a series of papers. In one of them, he proposed his celebrated theory of special relativity. It posits that mass and energy are the same thing. It also predicts effects at high-speeds, such as mass increase, time dilation, and length contraction.

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How old would I be if I travelled 1000 light years in one year

If I were to travel 1000 light-years, and witness only 1 year elapse in my frame of reference, how much time would have passed in the frame of reference of the Earth?
lakhassane
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Is it possible to know if you are travelling close to the speed of light if you have nothing to compare your speed with?

This is a question that has been bugging me for some time. Let's see if I am able to make me understood! Imagine you are travelling in a spaceship at 99.9999999999% the speed of light and you are somehow within a spaceship without windows. My…
Ignacio
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Does the twin paradox work in an almost empty universe?

Background The twin paradox is the popular thought experiment involving twins, one of whom makes a journey to a nearby star in a high-speed rocket (travelling at a velocity close to the speed of light) and when he reaches the star, changes direction…
John Davies
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Length contraction of a star

Something moving toward or away from us will be contracted in length according to special relativity. As the M31 galaxy is moving toward us at great speed it's "depth" should appear slightly flattened for us. A sphere moving toward us at the speed…
frodeborli
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Observing a point 13.82b ly away, 1b years ago

I understand that we can observe far away galaxies to get an idea how the universe looked like in the past. Assuming the universe is 13.82b years old, would it be correct to say that if we looked at a galaxy that was 13.82b ly away, we would see…
Nickpick
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