Astrophysics question

[John21]

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John,

Which do you think is more likely?

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Obviously, that the universe is expanding.

I was just wondering if the universe wasn't expanding, would an observer in another galaxy possibly look at the milky way galaxy as some type of black-hole?

And then just speculating if the rate of contraction was 3×10^8 metres per second.

[John21]

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If everything was shrinking wouldn't the distances between normal objects expand too? Like the distance between me right now and my tv set is about 2 meters. If both me, the tv set and every meter-measuring rod in the world was shrinking, it would seem to me like the tv was moving away from me.

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Wouldn't the gravitational forces, that are causing the contraction, contract space as well?

[JimNashe]

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Wouldn't the gravitational forces, that are causing the contraction, contract space as well?

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I dunno, it's your made up universe not mine.

But if space and things contracted at the same pace then nothing would happen and you'd have no explanation for the expanding universe. (other than the big bang)

[madnak]

Uh, there's no difference between the two phenomena, is there? Size and distance are relative, no? It's neither "shrinking" nor "expanding" per se, but an intuitive understanding of how everything is changing is impossible, and therefore we talking about "expanding" in the same way we refer to electrons as "particles" even though they don't resemble any kind of particles we're able to understand concretely.

[gull]

Because our yardstick would be changing with the universe, distances, as they are defined, would be the same. How you can someone say the universe is getting smaller without having some supernatural yardstick? In the fishbowl example, it would be the world outside the fishbowl.

[Big Limpin]

OP, this would imply that all things in our galaxy are contracting equally, for us not to notice differences in relative measurements, i.e. earth diameter vs earth to sun distance vs sun to other star distance. I would find it quite coincidental for dense objects like a planet to be contracting in exact harmony with interstellar distances.

[gull]

Wait, is space contracting or are objects in space contracting?

[whatnow1080]

I'm not sure if I completely understand your question, but I'm going to give it a try anyway. If our galaxy was contracting there would be a corresponding increase in the gravitational affects between all the matter in our galaxy. The gravitational force is constant and is proportional to distance, therefore objects in our galaxy would start moving faster. We do not see such things happening supporting the expanding universe theory. Also if our galaxy was shrinking there would be a noticible effect on the gravitational affects on nearby galaxys like the Andromeda and Triangulum. But once again no such observations have been made.