Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Dennis Soley on 16/01/2009 09:00:41
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Dennis Soley asked the Naked Scientists:
do we ever face the centre of the universe meaning do we ever face where the supposed big bang occured during the earths rotation?
What do you think?
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No, we cannot face the centre of the universe because we are always facing it. the centre is nowhere and everywhere because of the expansion of space itself.
If we look to the cosmic microwave background the size of the piece of universe we can see is only about as big as our galaxy but we have to look all over the sky to see it because it is all round us.
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No, we cannot face the centre of the universe because we are always facing it.
On the face of it that would not seem to make sense unless you are of course talking about an infinite universe.
So if the universe is infinite how could it be expanding.
Could it be that it is space time that is expanding and what it is expanding into is the universe.In which case space time must have had a beginning somewhere,Big Bang?.
After all do we not base a lot of our theory on the red shift to say that the universe is expanding and does the red shift not depend on observing light emitting objects in the universe that are apparently receding from us.Although I read that the Andromeda galaxy is going to collide with our own in about 6 billion years.So how can that be if we are expanding away from one another.
Cheers
justaskin
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Your logic is wrong. It is quite possible for an "infinite" universe to expand because it IS the space itself that is expanding.
Gravity still applies and galaxies tend to congregate together and merge to form large elliptical galaxies. The expansion of space does not become apparent until you get the the scale of clusters of galaxies and hundreds of millions of light years.
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Your logic is wrong. It is quite possible for an "infinite" universe to expand because it IS the space itself that is expanding.
Hmm did I not say something like that here.
Could it be that it is space time that is expanding and what it is expanding into is the universe.
Then if it is space that is expanding what is what it is expanding into called.Nothing, the universe, what?.
Cheers
Justaskin
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you stated and I quote "So if the universe is infinite how could it be expanding." which I understand means that you consider that an infinite universe could not expand.
The universe in its strictest sense meens absolutely everything so there cannot be anything anywhere that is not in the universe so it cannot have another name.
The universe could either be bounded or of indefinite size (infinite if you perefer tto use the mathematical term)
It is quite possible for a space to be finite and bounded like the inside of a black hole in whatever direction you travel at whatever speed (including light) you will never reach the edge but you could cross your path. It is also not possible to know anything about any other space that may be outside of the black hole.
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you stated and I quote "So if the universe is infinite how could it be expanding." which I understand means that you consider that an infinite universe could not expand.
Yes that is correct.
The universe in its strictest sense meens absolutely everything so there cannot be anything anywhere that is not in the universe so it cannot have another name.
Did I suggest another name for the universe.
The universe could either be bounded or of indefinite size (infinite if you perefer tto use the mathematical term)
Indefinite and infinite are not the same thing.And who bestowed the right on the mathematical community of soul ownership of the word infinite.
It is quite possible for a space to be finite and bounded like the inside of a black hole in whatever direction you travel at whatever speed (including light) you will never reach the edge but you could cross your path. It is also not possible to know anything about any other space that may be outside of the black hole.
I don't think that black holes are a fact just yet are they.As no one has ever been inside a black hole what happens inside one is only informed speculation.And if a black hole has a boundry how can it be infinite.
Cheers
justaskin
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When we say space is expanding it is just that. Imagine familiar objects separated by lots of tiny blobs of space every so often one of these blobs of space splits and becomes a pair of blobs of space. space has just got a bit bigger. It's just that this expansion is so tiny and so slow that you need absolutely enormous chunks of space to see any difference.
I never said that the inside of a black hole was infinite I said it was a bounded space that you could never reach the edge of. In just the same way it is possible to travel all over our approximately spherical world and never reach the "edge"
As far as black holes not existing. There is a large mass at the centre of our galaxy around which stars can be observed orbiting using observations in the infra red spectral band. The orbital sizes velocities and periods (as low as 16 years. A whole orbital period of this star has been observed this is not just one obscure measurement.) define the maximum size and mass of this dark object a some millions of solar masses in a very small volume. This is far too small a volume for any sort of normal matter because if it was it would radiate energy very violently. It is also very unlikely to be dark matter because the nature of dark matter prevents it from getting rid of the excess energy to congregate into large dense lumps it can only become diffuse blobs like galaxies. So currently the only option is a black hole which fits well with theory. observations of other galaxies show similar high velocity objects close to their centres so our galaxy is in no way special.
Black holes with masses of a few times that of the sun can also be observed and measured with confidence but the detailed evidence is too long and complex to present here. These are the sort generated by some types of supernovae.
That is enough evidence of the existence of black holes for me and most of the rest of the scientific community.
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And who bestowed the right on the mathematical community of soul ownership of the word infinite.
I think it's something to do with the fact that they have actually managed to define what they mean by the term - unlike other people who bandy it around without being sure what they mean by it.
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That is enough evidence of the existence of black holes for me and most of the rest of the scientific community.
That is fair enough you are entitled to your beliefs and understandings.Just that a cursory look around the internet would indicate the science is not quite settled yet.As with AGW, science is not a consensus subject.
There seems to be some holes in the theory of black holes. [:D]
SC I have provided you with my uneducated meaning/meanings of the word infinity.Maybe you would like to grace us with your learned meaning/meanings of the same word.
Cheers
justaskin
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Please remember that there is a vast amount of nonsense science around on the web because it is an easy place for any crank with a mad idea to get publicity so the statistics of opposing views is not a reliable measure of the general consensus of the main stream science community. It is quite true that some of the wild ideas may have value and some of the current main stream is probably wrong but the only tests are those of true scientific rigour and peer review.
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Yes SS I am painfully aware of quoting the web as some kind of authority.
Cheers
justaskin
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Gravitational lensing (http://www.etsu.edu/physics/bsmith/blackholes/bh.html) also seems to confirm the existence of black holes.
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It depends on what you consider the center of spacetime. You can't face backward in time. And then there is the question whether a beginning or end of time is meaningful. So the answer is either "yes, always" or "no, never" but nothing in between.
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If the big bang occurred at all then the center of where it happened must have a more than usual concentration of space matter. And the matter there must be moving at a slower rate than the matter further from it. For all I know, no one knows where it is.
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Don't think so Demadone:)
That's what the 'inflation theory' is about.
Explaining why we have such a even density to our observable universe.
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Justaskin, read the new topic on the Big Bang and the Horizon Problem - some of the discussion in there may help you to visualise why the 'centre' of the universe is in all directions.
Cheers.
JS
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Justaskin, I'm not too good with the higher maths either, but here's a good example of an infinity growing, or an infinity that is bigger than another infinity. You could have the set of all positive intergers {1,2,3,4,...∞} which goes on forever and ever to an infinity. If that then grew to all numbers with one decimal place you'd have {1.0,1.1,1.2,1.3,1.4,1.5,1.6,1.7,1.8,1.9,2.0,2.1,2.2,.............∞}. Both are infinities, but one is a bigger infinity, and I don't know exactly why but an infinity can get bigger. One explanation as to how it gets bigger is dark energy in space, which no one has pinned down yet. Anyway that's a quick example without any math I would be floundering in.
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DISCLAIMER- I barely made it through high school, but managed to survive for 20 years after graduation.
This boils down to one of the oldest questions in science. We can never know the answer until we know the right question. Infinite has a diferent answer depending on the question.
ex- travel in the same direction for an infinite amount of time. How far did you go? Infinite?
Walk around the earth for an infinite amount of time. How far did you go? Better yet, how many times did you pass the same spot?
To me, they are all the same answer. INFINITE
If the word is used to quantify something, it is not infinite and can not be used to calculate.
I'd rather say "I don't know" than call it infinite.