Astrophysics question

[John21]

I'm thinking of a fish inside a bowl, and the fish keeps getting smaller and smaller.

How do we know that our galaxy is not contracting, giving the appearance that the rest of the universe is expanding?

[goodsamaritan]

Because we'd be able to tell if everything in our galaxy was getting closer together

[John21]

[ QUOTE ]
Because we'd be able to tell if everything in our galaxy was getting closer together

[/ QUOTE ]

Relative to what?

Suppose you and all of your component parts shrunk to 1/10 of your current size, how could you determine if the rest of the world expanded or you shrunk?

[Lestat]

My guess:

We don't just measure distances, but radio active energy, x-rays, gamma-rays, etc. Unless our intruments here on earth (and their sensitivity to data), were shrinking as well, we would be able to detect disparities in the signal images being emitted by stars and other objects within our galaxy as they shrunk.

Now if you want to say that EVERYTHING is shrinking, including everything on earth, etc., then I guess there would be no way to tell. But that would be an illogical conclusion to come to.

[wazz]

[ QUOTE ]

Suppose you and all of your component parts shrunk to 1/10 of your current size, how could you determine if the rest of the world expanded or you shrunk?

[/ QUOTE ]

It doesn't matter which.... that's like blowing up a triangle to 10x its size then asking what is the new sum of the angles within.

Re your original question.... I'm not quite sure what you meant here. If the universe is expanding and our galaxy is somehow contracting, then it won't be long before we end up in some black hole. I don't see how one specific part of the universe would suddenly deem to contract, though. If the universe were expanding or contracting and our galaxy was doing the same at the same rate, it wouldn't make any difference to anything whatsoever.

[wazz]

K sorry I misunderstood.

It still doesn't make any difference though. Scales are scales. If Ax = 2Bx, then A5 = 2B5. Someone explain this better than me please.

[JayTee]

Correct me if I'm wrong John. I think he means that everything is shrinking except for space itself (the fish bowl). Giving the appearance that space is expanding, but in reality it is not.

[Borodog]

John,

Which do you think is more likely?

[JimNashe]

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.

[Borodog]

Good point.

[John21]

[ QUOTE ]
John,

Which do you think is more likely?

[/ QUOTE ]

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]

[ QUOTE ]
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.

[/ QUOTE ]

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

[JimNashe]

[ QUOTE ]

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

[/ QUOTE ]

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.