# How fast do galaxies 1 billion light-years away move away from us?

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• Dreksler
In summary: It is only a result of expansion of space.In summary, galaxies that are 312 times further away from us than those 1 megaparsec away are moving away from us at a recession velocity that is 312 times greater, due to the expansion of space. This means that the galaxies that are 312 megaparsecs away would be receding from our position at a speed of approximately 22,000 km/s. It is important to note that this movement is not proper motion, but rather a result of the expansion of space.
Dreksler
TL;DR Summary
If a galaxy that is 1 megaparsec away from us is moving away at a speed of 70 km/s. Does that mean that a galaxy that is 312 megaparsecs away is moving away at a speed of 22k km/s (312 times greater speed)?
We know that galaxies that are 1 megaparsec away from us (3.2 million light-years) are moving away from us here at a speed that is approximately 70km/s. Given that that is the case would that also imply that galaxies that are 312 megaparsecs (1 billion light-years) away from us are moving away from our position here at a speed of about 22,000 km/s?
Since they are 312 times further away would they also recede from our position here at a speed that is 312 greater?

Yes, recession velocity is proportional to distance.

stefan r and Dreksler
Dreksler said:
Summary:: If a galaxy that is 1 megaparsec away from us is moving away at a speed of 70 km/h. Does that mean that a galaxy that is 312 megaparsecs away is moving away at a speed of 22k km/h (312 times greater speed)?

We know that galaxies that are 1 megaparsec away from us (3.2 million light-years) are moving away from us here at a speed that is approximately 70km/s. Given that that is the case would that also imply that galaxies that are 312 megaparsecs (1 billion light-years) away from us are moving away from our position here at a speed of about 22,000 km/s?
Since they are 312 times further away would they also recede from our position here at a speed that is 312 greater?
Your use of "velocity" and "speed" is incorrect. The movement you are talking about HAS to be described as "recession velocity", not velocity or speed because those terms imply proper motion and there is none (or only a trivial amount) in the cases you are describing. You'll note that Perok was careful to say "recession velocity" because of the condition I just stated. That is, recession is NOT movement in the way you normally think of movement.

Dreksler

## 1. How do we measure the speed of galaxies 1 billion light-years away?

The speed of galaxies 1 billion light-years away can be measured using a variety of methods, such as redshift measurements, which measure the change in wavelength of light from distant galaxies. This can give us an indication of how fast the galaxies are moving away from us.

## 2. Is the speed of galaxies 1 billion light-years away constant?

No, the speed of galaxies 1 billion light-years away is not constant. In fact, the farther away a galaxy is, the faster it appears to be moving away from us. This is due to the expansion of the universe, which causes galaxies to move away from each other at an accelerating rate.

## 3. How does the speed of galaxies 1 billion light-years away relate to the expansion of the universe?

The speed of galaxies 1 billion light-years away is directly related to the expansion of the universe. As the universe expands, galaxies are carried along with it, causing them to move away from each other at faster speeds.

## 4. How long does it take for light from galaxies 1 billion light-years away to reach us?

Since light travels at a finite speed, it takes 1 billion years for light from galaxies 1 billion light-years away to reach us. This means that when we observe these galaxies, we are seeing them as they were 1 billion years ago.

## 5. Can we observe the movement of galaxies 1 billion light-years away in real time?

No, we cannot observe the movement of galaxies 1 billion light-years away in real time. Due to the vast distances involved, the light we receive from these galaxies is already billions of years old, so we are essentially seeing them as they were in the past.

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