Distance

Poll

Question in the first post.

If two people A and B stay in the same location and do not move, then the distance between them:

1. Doesn't change.

2. Can change.

3. Becomes shorter.

4. Wtf?

Please give me a reason if possible.

Reply 1

nota bene

doesn't change?

I mean the distance between to stationary objects surley can't change, do you see your walls moving :s-smilie:

?

Or am I missing some deep philosophical/physical reasoning?

Reply 2

Morbo

All 4 answers.

- Firstly, WTF indeed. What motivated you to ask this?! (4)
- If these two people are close to each other, then gravity will eventually pull them together. (3)
- If they are further from each other, the expansion of space will increase the distance between them. (2)
- If these two effects are similar, I guess you won't see much happen for a while. So (1). However, if you define these people as staying in "same location" relative to each other by, for example, them holding two ends of a rigid metre rule, then also (1), because you are defining the distance between them to be constant.

Reply 3

Eau

There is only one correct answer. As this is from a university-level exam paper. Well besides the last option obviously.

Reply 4

Morbo

What university asks this kind of (multiple choice??) question in a physics exam? The University of Obscurity? Is this even physics?

What do you think the answer is? And why?

Reply 5

Eau

How is this not physics?

I am guessing 2. the distance can change - because the universe is expanding, so they may eventually move apart if they stay in the same location forever? But on the other hand the universe could collapse.

But I may be wrong.

This is a physics course for laymen, not a mathsy one.

Reply 6

Morbo

The question isn't specific enough, basically. I'd say (2) because it's the one that's true in the most general case. What a crap question though.

Worzo

- If these two people are close to each other, then gravity will eventually pull them together. (3)

How does that work?

Reply 9

Morbo

Abra

How does that work?

Umm...because of Newton's law of gravity? Two massive bodies attract each other with a force "proportional to the product of their masses and inversely proportional to their separation"