Earth on the scale of things...

[bandit]

Antares is 604 light years away from Earth. If it went supernova right this second, we wouldn't be able to tell until 604 years from now because that's how long it would take the light from the explosion to get here. It's far enough away not to kill us.

actuaslly that just measn its very far away..., not that it could not kill us...!

as an aside.

given that we can:

estimate the movement of galaxies
guess that the universe is expanding in all directions at around about the same speed

has someone figured where the centre of the universe is?

 

[AJUK]

has someone figured where the centre of the universe is?

Me, I am the centre of the universe.

 

[Inquisitor]

has someone figured where the centre of the universe is?

No, it's impossible.

 

[badgermonkey]

I'm surprised at the size of some of these. Uranus is huge!

Hence the name "gas Giant"

 

[badgermonkey]

estimate the movement of galaxies
guess that the universe is expanding in all directions at around about the same speed

has someone figured where the centre of the universe is?

No, because everything isnt just moving away from a central point, everything is moving away from everything else.And as scientists reckon we can only see perhaps 10% of the entire universe (some say as high as 80, some say as low as 0.1) then we won't ever accurately find out "where" it all started. But that's because the where means nothing, at the time there was no "where". I refuse to now confuddlel my tired brain going into the details, i finished physics weeks ago!

 

[Inquisitor]

No, because everything isnt just moving away from a central point, everything is moving away from everything else.And as scientists reckon we can only see perhaps 10% of the entire universe (some say as high as 80, some say as low as 0.1) then we won't ever accurately find out "where" it all started. But that's because the where means nothing, at the time there was no "where". I refuse to now confuddlel my tired brain going into the details, i finished physics weeks ago!

This is something I've been wondering about. Although you can't meaningfully say 'where' the big bang happened, because as you say, there wasn't any concept of space, there must, in theory be a centre of the universe, must'nt there? (Assuming you accept that the universe started as a singularity and expanded in all directions from there.) Assuming that the universe is an expanding sphere of space, it must have limits. These limits, or edges, would therefore give a reference point for an absolute centre of the universe.

 

[Psyk]

Surely something could be worked out from the directions that other galaxies are moving away from us? For example if we discovered a galaxy moving perpendicular to our own then we could find a point of origin.

 

[Spyhop]

This photo shows the centre of the universe:

 

[Inquisitor]

Surely something could be worked out from the directions that other galaxies are moving away from us? For example if we discovered a galaxy moving perpendicular to our own then we could find a point of origin.

The problem is that it looks the same wherever you are.

For example, the galaxy Andromeda, which is around 2.5 million lightyears away, is currently moving away from us at about 50km/s. However, if we went to Andromeda, the Milky Way would appear to be moving away from us at 50Km/s, so wherever you are, you appear to be at the centre of the universe.

 

[badgermonkey]

This is something I've been wondering about. Although you can't meaningfully say 'where' the big bang happened, because as you say, there wasn't any concept of space, there must, in theory be a centre of the universe, must'nt there? (Assuming you accept that the universe started as a singularity and expanded in all directions from there.) Assuming that the universe is an expanding sphere of space, it must have limits. These limits, or edges, would therefore give a reference point for an absolute centre of the universe.

But you can't guarantee that the universe IS an expanding sphere of space. As for the start, it is described as a singularity, but that's not quite true. First there wasn't, then there was. Not "There wasnt anything", just "There wasn't".

Within roughly a second (it is thought) the universe was already a few lightyears wide.

 

[Psyk]

The problem is that it looks the same wherever you are.

For example, the galaxy Andromeda, which is around 2.5 million lightyears away, is currently moving away from us at about 50km/s. However, if we went to Andromeda, the Milky Way would appear to be moving away from us at 50Km/s, so wherever you are, you appear to be at the centre of the universe.

I know but I'm not talking about the speed at which they are moving away from us, I'm talking about direction. If you drew an infinitely long straight line in the direction we are moving, and a similar line in the direction another galaxy is moving, then the point at which they meet is the centre.

 

[Inquisitor]

I know but I'm not talking about the speed at which they are moving away from us, I'm talking about direction. If you drew an infinitely long straight line in the direction we are moving, and a similar line in the direction another galaxy is moving, then the point at which they meet is the centre.

But that's my point; how do we know what direction we are moving in, or any other galaxy? All we can see is that they are moving away from us.

Remember, velocity and displacement are relative; they require a reference point to have meaning. Since we don't have a reference point, other than ourselves, we can't determine the absolute velocity or displacement of anything (if such a thing exists).

 

[badgermonkey]

I know but I'm not talking about the speed at which they are moving away from us, I'm talking about direction. If you drew an infinitely long straight line in the direction we are moving, and a similar line in the direction another galaxy is moving, then the point at which they meet is the centre.

But that's my point; how do we know what direction we are moving in, or any other galaxy? All we can see is that they are moving away from us.

Remember, velocity and displacement are relative; they require a reference point to have meaning. Since we don't have a reference point, other than ourselves, we can't determine the absolute velocity or displacement of anything (if such a thing exists).

That pretty much answers you, you NEED a reference point but we cant be fully sure of anything. Then throw in the added problems caused by redshift and time dilation and you have yourself one impossible cookie to crack. If you dont know what time dilation is go read up on it, because that'll boggle your mind even further

 

[SourChipmunk]

Within roughly a second (it is thought) the universe was already a few lightyears wide.

That would require faster-than-light travel, would it not?

 

[Calibos]

I know but I'm not talking about the speed at which they are moving away from us, I'm talking about direction. If you drew an infinitely long straight line in the direction we are moving, and a similar line in the direction another galaxy is moving, then the point at which they meet is the centre.

I hope the physicists can confirm but I think this is where the balloon example comes in. You are saying draw lines back from the direction a selection of galaxies are moving in and where the lines intersect is the centre of the universe. Imagine the galaxies are a few coloured sticky dots you stick to a flacid baloon. Blow up the balloon (This is the universe expanding. From each dots/galaxies perspective, all the other dots are all moving away from each other, so in effect if you draw lines back from theses other dots/galaxies, all the lines will point back to your home dot/galaxy meaning it always seems as if where you are is the centre of the universe like inquisitor said.

 

[badgermonkey]

That would require faster-than-light travel, would it not?

Indeed I already questiuoned this, but my Physics teacher was also unclear on this theory. I think its something to do with the fact that it has to be accepted that SOMETHING we're not sure about was involved in this, as there are MANY things involved in the big bang that make absolutely no sense.

It could have been a few minutes, im still unsure entirely tbh.

 

[badgermonkey]

I hope the physicists can confirm but I think this is where the balloon example comes in. You are saying draw lines back from the direction a selection of galaxies are moving in and where the lines intersect is the centre of the universe. Imagine the galaxies are a few coloured sticky dots you stick to a flacid baloon. Blow up the balloon (This is the universe expanding. From each dots/galaxies perspective, all the other dots are all moving away from each other, so in effect if you draw lines back from theses other dots/galaxies, all the lines will point back to your home dot/galaxy meaning it always seems as if where you are is the centre of the universe like inquisitor said.

Thats the best example ive heard in the last 2 years! (Stupid physics teachers, I already had to explain something to him once!)

But yep, i think that sums it up.

 

[Psyk]

But that's my point; how do we know what direction we are moving in, or any other galaxy? All we can see is that they are moving away from us.

Remember, velocity and displacement are relative; they require a reference point to have meaning. Since we don't have a reference point, other than ourselves, we can't determine the absolute velocity or displacement of anything (if such a thing exists).

But I don't see why we wouldn't be able to tell what direction other galaxies are moving, relative to us. I would have thought it would be simple to see if another galaxy is moving at right angles to us, providing we had a method to make those measurements.

 

[Inquisitor]

But I don't see why we wouldn't be able to tell what direction other galaxies are moving, relative to us. I would have thought it would be simple to see if another galaxy is moving at right angles to us, providing we had a method to make those measurements.

Well yes, that would be easy to notice. The thing is that it wouldn't be moving at right angles to us, it would be moving away from us.

 

[Locky]

The other strange thing is how our current technology allows us to travel around the whole of earth in around 24 hours, just seems a little convenient that the earth is the perfect size for air travel, so if our planet was the size of say Jupiter do you think our technology would be more advanced and allow us to travel even faster?

tbh yes. like a gold fish etc it can only grow to the size of its tank

so same mayb applyed to us. if we needed to travel distances of much larger planets, we would have been pushed and there is a need for this.