<p>For the specific question on travelling to a point 500 light years away, the answer is <em>no</em>.  There is enough matter in the Milky Way to keep space from expanding inside the Milky Way. So if the destination is not moving relative to the Earth, then it will still be 500 light years away when you reach it.</p>
<p>If you are travelling to a distant galaxy that is 500 000 000 light years away, then the expansion of space does become significant.  The expansion of space means that the distant galaxy <em>is</em> moving away from the Earth, so by the time you reach the galaxy (in more than 500 000 000 years) it will have moved further away.  The distance it had travelled would depend entirely on how long you had taken to reach the galaxy, and so would depend on your velocity.</p>
<p>There although distant galaxies are moving away from us due to the metric expansion of space, there is nothing very strange happening here. If I am running to catch up with a friend, but my friend is walking away from me, then I'll need to account for their motion.</p>
<p>Over even longer distances, the length of time required means that assumptions like &quot;the rate of expansion is constant&quot; are no longer valid.</p>
<p>But over &quot;short&quot; distances, like 500 lightyears, space isn't expanding.</p>

CC BY-SA 4.0
2022-11-06T06:57:25.153Z
Thanks for your swift response James, and for your understanding of what I meant when applied to galaxies beyond our own, it is very much appreciated .
Lux Magi
CC BY-SA 4.0
2022-11-05T11:14:02.873Z
2022-11-05T11:14:02.873Z
James K
<p>If a place is 500 light years away, then I set out to this place, then is it true to say that, the place which I set out from, will be 750 light years away from my destination, once I have reached it?</p>
<p>I am thinking of expanding space, as the reason for the additional distance possibly accumulated. Also to be considered for other galaxies separate from our own. Also what would be the estimated increase in the distance would it be half as much, or a quarter or third?</p>
<p>If the speed of light is 186 282 miles per second, then what would be the distance of expansion accumulated which occurred within the time it would take for a craft traveling at this speed to reach a galaxy beyond ours, or even a distance of 500 light years away, obviously there are innumerable distances of light years which could be applied to this calculation.</p>

CC BY-SA 4.0
2022-11-03T05:31:16.657Z
@DialFrost This is a repost of a question from a few weeks ago which was automatically deleted because the system thought it was abandoned. Some of the info in the question was added in response to comments.
PM 2Ring
CC BY-SA 4.0
2022-11-03T05:34:15.877Z
@PM2Ring Ah my bad, I didn't look closely enough (I can't see deleted questions either) :3 (Close vote retracted)
DialFrost
CC BY-SA 4.0
2022-11-03T10:16:30.130Z
500 light-years from Earth is _well_ within the Milky Way galaxy.  As such, the overwhelming effect on the distance between your origin and destination on arrival is the relative motion of the two objects and your travel time, not universe expansion.
notovny
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2022-11-03T13:40:02.940Z
Not even just the overwhelming effect, but the entire effect! The galaxy isn't expanding.
Sten
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2022-11-05T18:11:28.023Z
You can't have a spacecraft travel at the speed of light.
ProfRob
CC BY-SA 4.0
2022-11-06T06:52:39.770Z
I am well aware that present day spacecraft can nowhere near reach the speed of light, I was asking the question from a hypothetical standpoint, to demonstrate the scenario.
Lux Magi
<observational-astronomy><astrophysics><cosmology><universe><space-time>
Time and space travel as applied to expanding space and the ratio of/between time and distance
Lux Magi
# Time and space travel as applied to expanding space and the ratio of/between time and distance

(Asked by: username_0 on 2022-11-02)

If a place is 500 light years away, then I set out to this place, then is it true to say that, the place which I set out from, will be 750 light years away from my destination, once I have reached it?

I am thinking of expanding space, as the reason for the additional distance possibly accumulated. Also to be considered for other galaxies separate from our own. Also what would be the estimated increase in the distance would it be half as much, or a quarter or third?

If the speed of light is 186 282 miles per second, then what would be the distance of expansion accumulated which occurred within the time it would take for a craft traveling at this speed to reach a galaxy beyond ours, or even a distance of 500 light years away, obviously there are innumerable distances of light years which could be applied to this calculation.

**Tags:** observational-astronomy, astrophysics, cosmology, universe, space-time

> **Comments:**
> **username_1**: @username_2 This is a repost of a question from a few weeks ago which was automatically deleted because the system thought it was abandoned. Some of the info in the question was added in response to comments.  
> **username_2**: @PM2Ring Ah my bad, I didn't look closely enough (I can't see deleted questions either) :3 (Close vote retracted)  
> **username_3**: 500 light-years from Earth is _well_ within the Milky Way galaxy.  As such, the overwhelming effect on the distance between your origin and destination on arrival is the relative motion of the two objects and your travel time, not universe expansion.  
> **username_4**: Not even just the overwhelming effect, but the entire effect! The galaxy isn't expanding.  
> **username_5**: You can't have a spacecraft travel at the speed of light.  
> **username_0**: I am well aware that present day spacecraft can nowhere near reach the speed of light, I was asking the question from a hypothetical standpoint, to demonstrate the scenario.  

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## 1 answers

### Answer by username_6 on 2022-11-05. Score: 1

For the specific question on travelling to a point 500 light years away, the answer is *no*. There is enough matter in the Milky Way to keep space from expanding inside the Milky Way. So if the destination is not moving relative to the Earth, then it will still be 500 light years away when you reach it.

If you are travelling to a distant galaxy that is 500 000 000 light years away, then the expansion of space does become significant. The expansion of space means that the distant galaxy *is* moving away from the Earth, so by the time you reach the galaxy (in more than 500 000 000 years) it will have moved further away. The distance it had travelled would depend entirely on how long you had taken to reach the galaxy, and so would depend on your velocity.

There although distant galaxies are moving away from us due to the metric expansion of space, there is nothing very strange happening here. If I am running to catch up with a friend, but my friend is walking away from me, then I'll need to account for their motion.

Over even longer distances, the length of time required means that assumptions like "the rate of expansion is constant" are no longer valid.

But over "short" distances, like 500 lightyears, space isn't expanding.

> **Comments:**
> **username_0**: Thanks for your swift response James, and for your understanding of what I meant when applied to galaxies beyond our own, it is very much appreciated .  

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