If time is relative, is speed also?

Question

If we measure time by the solar year, would we calculate speed on another planet, like mars maybe, differently based on it’s solar year? Or would we use “Earth speed”?

In: 0

Answer 1

You’re conflating different things are and also you have some incorrect assumptions. You’re fundamentally misunderstanding what relativity means and how we measure time.

First, time is not measured by the solar year. I have no idea where you got that from but it’s wrong. Time is measured by the second. A second is always a second no matter where you are. You could be in New Jersey or Australia or Mars or the Andromeda galaxy, you will always experience a second to be the exact same length of time. So when we say one of the Mars rovers drove at 50 meters per hour, that’s the exact same speed as 50 meters per hour on Earth because it’s the exact same second and the exact same meter and we’re measuring it from the perspective of the Mars rover itself.

Now this is not what you were asking about, but velocity *is* relative, just not in the way that you meant. Right now I’m standing still on Earth. From the frame of reference of Earth, my velocity is 0 because I’m standing still. But the Earth is traveling around the Sun at roughly 30 kilometers per second. That means from the frame of reference of the sun, my velocity is 30 kilometers per second, so my velocity is different depending on what you use as a reference point. There’s a lot more to relativity than this but that’s beyond the scope of this question

Answer 2

You’re conflating different things are and also you have some incorrect assumptions. You’re fundamentally misunderstanding what relativity means and how we measure time.

First, time is not measured by the solar year. I have no idea where you got that from but it’s wrong. Time is measured by the second. A second is always a second no matter where you are. You could be in New Jersey or Australia or Mars or the Andromeda galaxy, you will always experience a second to be the exact same length of time. So when we say one of the Mars rovers drove at 50 meters per hour, that’s the exact same speed as 50 meters per hour on Earth because it’s the exact same second and the exact same meter and we’re measuring it from the perspective of the Mars rover itself.

Now this is not what you were asking about, but velocity *is* relative, just not in the way that you meant. Right now I’m standing still on Earth. From the frame of reference of Earth, my velocity is 0 because I’m standing still. But the Earth is traveling around the Sun at roughly 30 kilometers per second. That means from the frame of reference of the sun, my velocity is 30 kilometers per second, so my velocity is different depending on what you use as a reference point. There’s a lot more to relativity than this but that’s beyond the scope of this question