Hubbles Law and Relativity

[Ray02]

So recently I read about the Hubbles Law, Relativity and Doppler effect. The Universe is expanding but that means that it has where to expand. So where does it expand? 

[Zakalwe]

1 hour ago, Ray02 said:

 The Universe is expanding but that means that it has where to expand. So where does it expand? 

Spacetime is expanding. It doesn't need "anywhere" to expand into.

[cloudsweeper]

Exactly!  It's counter-intuitive, and goes against our everyday perceptions of what space is.

Doug.

[Pippy]

mmmm, a little mind bending isn't it.

The fact that the universe is here at all is a complete paradox for the human mind.

 

[Ray02]

10 hours ago, Zakalwe said:

Spacetime is expanding. It doesn't need "anywhere" to expand into.

Well but how can you imagine time expanding because space and time expands, not only time. Everything has to expand somewhere because otherwise the universe is endless and that means the BB is incorrect. 

[Ray02]

6 hours ago, Pippy said:

mmmm, a little mind bending isn't it.

The fact that the universe is here at all is a complete paradox for the human mind.

 

Yeah! You are totally right we seem to know a lot more than a century ago but the more questions we answer the more questions we get. For me personally Universe, Earth and everything else is amazingly amazing. My life changed when I started astronomy and stargazing, it makes you feel like someone totally different than you were before.  

 

Never stop dreaming...

[Zakalwe]

9 minutes ago, Ray02 said:

Well but how can you imagine time expanding because space and time expands, not only time.

Imagination has nothing to do with it.

9 minutes ago, Ray02 said:

 Everything has to expand somewhere because otherwise the universe is endless and that means the BB is incorrect. 

That's opinion and one that doesn't seem to tally with what is observed. The Universe is under no obligation to act in the way that is understandable to us.

No-one is able to say whether the BB is incorrect or correct. Rather, at the moment, it seems to be the best theory to fit what we see.

 

 

[ollypenrice]

A very clever friend of mine (who once beat Nigel Short at chess) was sitting down on our terrace one morning with his 8 year old daughter on his knee. We'd all been 'astronomizing' the night before. As I strolled outside I heard him say to her, 'No, it doesn't expand into anything. All that there is is expanding.'  And Saskia, cool as a cucumber, replied, 'Oh yes, I see.'

Which made me think of Einstein who defined common sense as 'That set of prejudices accumulated by age eighteen.'

If the universe had anywhere into which to expand it would not be the universe. The universe would be the place into which it was expanding.

Olly

PS It may be a detail but the Doppler effect does not describe the cosmological redshift. The Doppler effect describes two objects moving apart because they are moving apart in the sense that they have been accelerated away from each other. The cosmological redhift can describe two objects which are not moving apart because they have been accelerated but becauase the space betaeen them is expanding. An oft-used analogy concerns coins stuck to a balloon to represent galaxies. They cannot be accelerated because they are stuck to the balloon, but they can move apart if you blow into the balloon. Like all analogies it has its limits, but on a balloon of a constant size you could accelerate not-stuck coins apart with your fingers. That is a different scenario to the 'stuck coins/expanding balloon' one. The Doppler effect describes 'not stuck' coins and the cosmological redshift describes the stuck ones.

And so to bed!

Olly

[Pippy]

Time and indeed space may infact be just an illusion that we ourselves have created in order to try and understand what the universe really is. Their's a good chance that our perception and interpretation of time and space is really quite wrong, and quite false, but it's currently how our minds are working with trying to find out what the heckers this place we call the universe actually is etc.

[acey]

Picture an infinite universe where every star (galaxy, cluster, whatever) is one distance-unit (light-year, parsec, whatever) away from its nearest neighbour. Imagine that distance growing. That's what's happening.

[Ray02]

So many answers and witch to choose? But anyways thanks for everyones relplied I had a nice time over thinking it

[Pippy]

On 11/10/2016 at 20:11, ollypenrice said:

Which made me think of Einstein who defined common sense as 'That set of prejudices accumulated by age eighteen.'

One could easily argue that all our teachings from before second one are THE cause for any and all our prejudices - "prejudices" meaning bias in all areas of thought

[Herzy]

Pretend the universe is the sphere. It is comprised of only two dimensions, and it is curved through a higher dimension to form a sphere. This sphere is obviously finite, but it can expand. Does that help?

[Pluto the Snowman]

On 11/10/2016 at 09:51, cloudsweeper said:

Exactly!  It's counter-intuitive, and goes against our everyday perceptions of what space is.

Doug.

 

Its the thing that a big house has plenty of and a small house has little of. The universe has an astronomically huge amount of it. That is how I perceive it. Im going to the toilet.