# Object traveling in vacuum

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1. Apr 24, 2015

### Biscuit

So a couple of days ago I ran into someone who said that an object traveling forever in a vacuum will eventually come to a stop due to deformation. After a little research I wasn't able to find much on the topic can someone explain it to me, and is it true that he object will eventually stop. Just off of the top of my head the only thing that I can think of that would deform an object in a vacuum would be its own gravity, but I doubt this because from my little understanding on the matter gravity and its object are at an equalibruim.

2. Apr 24, 2015

### nasu

Maybe deformation of the space-time?
Anyway, there is not much to talk about here. There is no way to find the context, probably, as it is just word of mouth.

3. Apr 24, 2015

### Staff: Mentor

OP,

That makes no sense at all.

4. Apr 24, 2015

### DaveC426913

For starters, there is no such thing as "come to a stop" in space. Best it can do is be at rest relative to some arbitrarily chosen point such as a nearby planet or star. On this alone, your friend is clearly naive about the physics. You could tell him that, and go no further.

If an object were big enough, it might eventually become spherical under its own gravity. But that will have zero effect on its velocity.

Perhaps he's thinking that sufficient impacts with interstellar debris will slow it to some average velocity.

5. Apr 24, 2015

### rootone

In a vacuum the only thing which significantly can change the object's trajectory, (and possibly slightly deform the object), would be the gravity of other massive objects which it passes nearby.

6. Apr 24, 2015

### DaveC426913

And impacts with bodies, gas, dust and other debris.

7. Apr 24, 2015

### rootone

But then it isn't travelling in a vacuum.

8. Apr 24, 2015

### DaveC426913

Of course it is.

No vacuum is completely free of particles. Best natural (or even artificial) vacuum is measured in particles per unit volume.

http://en.wikipedia.org/wiki/Interstellar_medium
Read paragraph 3 for some examples.

9. Apr 24, 2015

### rootone

Well yes, there is no actual absolute vacuum in nature, so over a very long time the accumulation of minor impacts could slow it down.
I had read then OP as meaning an idealised vacuum with literally nothing at all present other than the object itself.

10. Apr 24, 2015

### Biscuit

well thank you all for the answer, I was on your side in the first place. It did seem strange to me that he said this thank you for re-enforcing this for me. I would also like to say that when I say "come to a stop" don't try to take it too meaningful i think you know what i meant.

11. Aug 21, 2016

### phinds

Yes, you meant something that is meaningless in actual physics which is why you got the answer you did. We DO tend to take actual physics as being meaningful.

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