The size of the universe

[Megabrain]

Ok lets consider this,

 

Suppose we establish contact with a nearby alien society and send them some everyday objects from earth among which is an elastic band.

 

So they play with this and slowly stretch it taking readings of length, after a while they get bored, look at the data and decide that this elastic band could be stretched forever but they don't have the time to put this to the test so they mark rubber as infinitely strechable.

 

What the hell has this got to do with the size of the universe I hear you ask well not a lot except that we seem to be applying this form of logic to where we think the universe is going.

 

I'll explain, the data we have that suggests the universe is expanding at an everincreasing rate comes from modern observations of photons which started their journey towards us up to 12 billion years ago, thus surely it is only scientifically accurate to say that the data from 12 billion years ago supports the premiss that the universe was expanding then.

 

If for example the universe began collapsing towards us at the speed of light then we would have no prior warning of this.

 

we have no direct up-to-date data from the edge of the universe thus to say the universe is expanding is surely NOT a fact but at best only highly probable.

 

Any comments?

[Airbrush]

If for example the universe began collapsing towards us at the speed of light then we would have no prior warning of this...we have no direct up-to-date data from the edge of the universe thus to say the universe is expanding is surely NOT a fact but at best only highly probable.

 

Any comments?

 

That sounds right to me. Good question. Is it only because it is improbable for something that is seen to be expanding at an increasing rate to abruptly slow down, stop, and reverse? That reversing process seems unlikely, and would take a long, long time. It will be interesting to hear comments.

[Mr Skeptic]

On the other hand, you can expand a gas indefinitely, but eventually the gas would be so dispersed it would better be described as a vacuum. A rubber band has to stop because once its molecules are straightened out, they can't be straightened more and will snap instead.

[Megabrain]

As I said Mr Skeptic, nothing to do with the elastic band, merely an example of the misuse of logic. we have only a single slice of data for any given part of the visible universe, for the very edge of the universe this data is 12 billion years old, if the bubble has burst and the the universe is dissappearing (not 'shrinking') at the speed of light and coming towards us then all the galaxies we see would continue to expand until they were overtaken by the boundary - I also made the point of it being an alien testing the band and then not to far of course we know (but only through experience what will happen) whereas the alien may not yet have discovered that there is a limit to how small things can get.

[Klaynos]

We can state that the evidence we are currently measuring leads us to the conclusion that the universe is currently expanding at an accelerating rate. To as "what the universe is really doing" is a bit meaningless because unless you can experimentally test it, it's not science.

[Megabrain]

We can state that the evidence we are currently measuring leads us to the conclusion that the universe is currently expanding at an accelerating rate. To as "what the universe is really doing" is a bit meaningless because unless you can experimentally test it, it's not science.

 

Thats a wonderful piece of self contradiction there, the evidence we have left the edge of the universe 12 billion years ago thus to say that is what is happening today I agree is meaningless. I can accept that not everybody has a mind capable of understanding this point, in the same way of understanding the big bang defeats most people.

 

The facts are that the data we have from the edge of the universe is up to 12 billion years old.

 

Normally in science we would say that this shows that "at that time and befeore then, the universe was expanding at an accelerating rate"

For some reason the normal scientific caution is dispensed with in this case.

 

I fully accept that the universe may well still be expanding, in the light that we have no reason to assume otherwise, but if you saw a horse gallop off into the distance as a child would you assume that horse is still galloping away today simply you have no proof either way except by your experience of other horse and their probable lifespan, with the universe we have no other data.

[Klaynos]

To us that 12billion years ago is 'now' in terms of causality...

 

I don't think the normal scientific caution is dispensed with, it's just that scientists are often lax about language because they tend to talk to people who understand what they mean, this falls down when talking to the public, where comments that taken in context by another scientist can easily be misconstrued. A case of this in my own field is that of slow or stopped light...

 

The thing is you can tell what the horse is doing causally to within a very very short time scale it doesn't take 12billion years for the information to get to you.

 

The concept of "now" is pretty meaningless when we talk about astronomical events...

[NowThatWeKnow]

...

The facts are that the data we have from the edge of the universe is up to 12 billion years old.

...

 

Keep in mind that the expansion is not from the edge out, but is uniform. The expansion is also measured much closer to home so the horse is not all that far away. Since there is no reason to believe we are at the center of the universe we could represent what is happening everywhere.

[samtheflash82]

it basically just states, that we can not know for sure right now whether it is expanding or not.

[Klaynos]

it basically just states, that we can not know for sure right now whether it is expanding or not.

 

The issue is again what is meant by "now," causally "now" at the furthest point we can see is around 12billion years ago...

[Airbrush]

The expansion is also measured much closer to home so the horse is not all that far away. Since there is no reason to believe we are at the center of the universe we could represent what is happening everywhere.

 

We can measure expansion all along a continuum from near to far. Over that range of over 10 Billion years there WAS expansion of various consistent rates including inflated rates. So probably expansion continues.

[Martin]

I don't think the normal scientific caution is dispensed with, ...

 

The thing is you can tell what the horse is doing causally to within a very very short time scale it doesn't take 12billion years for the information to get to you...

 

... The expansion is also measured much closer to home so the horse is not all that far away. Since there is no reason to believe we are at the center of the universe we could represent what is happening everywhere...

 

We can measure expansion all along a continuum from near to far. Over that range of over 10 Billion years there WAS expansion of various consistent rates including inflated rates. So probably expansion continues.

 

I mainly want to concur with what has been said.

 

Gen Rel came out in 1915 and was initially tested by observing light-bending (Eddington 1919) and the planet Mercury (actually a post-diction but still a confirming test.)

 

On the basis of that Friedman developed the expanding universe model and published in 1922. He didn't base this on redshift. If it had any empirical basis it was Eddington 1919 and the perihelion of Mercury, that is observations within our solar system. It was one possible solution to Einstein's equation.

 

Then later, in 1929, Hubble published the linear correlation of distance and distance-increase-rate. He had discovered that largescale distances increase at approximately the same percentage rate. This fits Friedman's model.

 

Basically scientific theories are not intended to believe in, they are meant to be tested, by forcing them to yield testable predictions. Eventually the hope is if you push it far enough you can get a theory to predict something that turns out wrong and that will reveal some new physics and you get a chance to improve the theory.

 

General Relativity (which models dynamic geometry and gravity) has passed many tests with exquisite precision. It is confirmed by a lot of other empirical results besides redshifts! The redshift data keeps coming in and providing additional support but that is only part of the story.

 

That doesn't mean that astronomers believe GR is true. It is widely recognized to need improvement (that is what all the research in quantum gravity and quantum cosmology is about). But it is the best model we have so far of how geometry evolves, and how gravity works. It's also simple, which is a serious consideration.

 

A theory which agreed with GR on all past observations but predicted that tomorrow the moon would crash into the earth with the speed of light---a kind of "MegaChicken Little" theory ---would have to be extremely complicated.

 

Likewise one could presumably construct a mathematical model of geometry and gravity, a kind of Megachicken "The Universe is Falling!" theory which would duplicate the success of the Friedman model up until now and would predict that tomorrow all the observed redshifts would change sign and become blueshifts. That is aliens able to violate what we thought were laws conservation of energy and momentum and probably every other presumed law had made a sudden concerted effort and turned things around! Intervening in an orchestrated way such that we would only get the news of it tomorrow, and not a hint would arrive earlier.

 

This is possible and were it to happen would doubtless be welcomed by theoretical physicists and cosmologists because it would represent new physics. All the old laws would have to be revised! So as to be consistent with what had just been observed. In that case there would still be billions of years in which to figure out what was happening. (Unlike the case with the Moon falling on us. )

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Merged post follows:

Consecutive posts merged

...If for example the universe began collapsing towards us at the speed of light then we would have no prior warning of this.

...

 

If the Moon suddenly changed course and headed towards us at the speed of light we would also have no prior warning.

 

If this has in fact occurred then those at the point of impact now have around 1.2 seconds of blissful ignorance remaining them.

Edited April 12, 2009 by Martin
Consecutive posts merged.

[jackson33]

I could be wrong, but think your all are missing MB point; We are that near by alien society and have assumed the Universe is expanding, possibly forever as assumed by many. We base our opinions on what we are told, feel or in some strange manner accept. If you think about it, any mention today that the U is NOT expanding, will get instant rebuttal on all the "Empirical Evidence" often a phase used here....

 

If however the Universe has been decreasing in diameter, say for 2 billion years and at C, we would still be seeing what was emitted from the sources of energy from a source that then existed and see nothing of of what may currently be reality. We assume beyond the estimated 13.2 bly away is nothing, for this reason, while eliminating the possibility there may be nothing there, not necessarily that 13.2 bya was the then current limits of this U...Said another way, whatever photons we capture for the duration of earths existence has long been en route and nothing emitted over 2-3 billion years ago will ever be observed by whatever ends when our Sun begins to die...

 

If space with in the Universe has been decreasing, even from the limits at C, we would have no means to measure the lost space between objects. For all we know the distance from Earth to the moon, would have been increasing slightly more than it is and is relative to the U, getting closer to the earth. Your talking billions of years for that space between the earth and moon to lose enough space to hit the earth and no one would ever know when the collapse reached our MW.

[Airbrush]

I could be wrong, but think your all are missing MB point; We are that near by alien society and have assumed the Universe is expanding, possibly forever as assumed by many. We base our opinions on what we are told, feel or in some strange manner accept. If you think about it, any mention today that the U is NOT expanding, will get instant rebuttal on all the "Empirical Evidence" often a phase used here.....

 

The light that left galaxies Millions of years ago tell us the universe WAS expanding. The light that left galaxies Billions of years ago also tell us the universe WAS expanding. The light from galaxies everywhere in between (Millions and Billions of years ago) tell us the SAME thing. You propose a departure from a long-standing trend and nothing to support that.

 

I base my opinion on the opinion of the experts. They know better and I trust their judgment. If a scientist came up with evidence to the contrary, supporting your proposition, it would be VERY exciting among most scientists who would get busy trying to reconcile the new evidence.

[jackson33]

The light that left galaxies Millions of years ago tell us the universe WAS expanding. The light that left galaxies Billions of years ago also tell us the universe WAS expanding. The light from galaxies everywhere in between (Millions and Billions of years ago) tell us the SAME thing. You propose a departure from a long-standing trend and nothing to support that.

 

I base my opinion on the opinion of the experts. They know better and I trust their judgment. If a scientist came up with evidence to the contrary, supporting your proposition, it would be VERY exciting among most scientists who would get busy trying to reconcile the new evidence.

 

Perhaps a more complete assessment is that the interpretation of the metric expansion of space continues to provide paradoxes that are still a matter of debate.[2][3][4][5] The prevailing view is that of Chodorowski: "unlike the expansion of the cosmic substratum, the expansion of space is unobservable".[6] http://en.wikipedia.org/wiki/Metric_expansion_of_space

 

Actually I posted on this topic, to kind of welcome MB, with a desire he continue activity here, having known him for years. I had left his previous forum months ago, coincidentally over poor treatment of one of your current moderators and coincidentally no friend of MB. I have tried posting on 'The Original' subjects that interest me (in science) and/or would be interested in personal opinions. If I just wanted the current scientifically based theories, I could google, but feel I understand most that are current. Since I rather enjoy many of the posters here on other subjects, I just don't bother arguing Astronomy. I am an old guy, watched in disbelief over the past 60 years while what to me was a trashing of what is called 'Steady State'. IMO will in the end be accepted over what I perceive an agenda driven acceptance of a seriously flawed BBT. Sorry, if I ruffled your feathers, but what I posted, IMO could be backed up with alternative theory, though not the accepted.

[Airbrush]

Perhaps a more complete assessment is that the interpretation of the metric expansion of space continues to provide paradoxes that are still a matter of debate.[2][3][4][5] The prevailing view is that of Chodorowski: "unlike the expansion of the cosmic substratum, the expansion of space is unobservable.

 

I took a look at those paradoxes and I honestly don't understand them. Would you care to explain? What does it mean that the expansion of space is unobservable? Many science facts are unobservable. You cannot observe electrons running along a copper wire. Some science facts are proven by other means.

[jackson33]

I took a look at those paradoxes and I honestly don't understand them. Would you care to explain? What does it mean that the expansion of space is unobservable? Many science facts are unobservable. You cannot observe electrons running along a copper wire. Some science facts are proven by other means.

 

Guess MB, just wanted to taunt Ophiolite (ref; Message on Ophiolite Profile) and not interested in posting, defending his thread or the guestion "any thoughts"....so be it.

---------------------------------------------------

The expansion of the universe proceeds in all directions as determined by the Hubble constant today. However, the Hubble constant can change in the past and in the future dependent on the observed value of density parameters (Ω). Before the discovery of dark energy, it was believed that the universe was matter dominated and so Ω on this graph corresponds to the ratio of the matter density to the critical density (Ωm).

 

REFR; 2-3-4-5, article conclusion based on Refr. 6...

^ Alan B. Whiting (2004). "The Expansion of Space: Free Particle Motion and the Cosmological Redshift". ArXiv preprint. http://arxiv.org/abs/astro-ph/0404095v1. ^ EF Bunn & DW Hogg (2008). "The kinematic origin of the cosmological redshift". ArXiv preprint. http://arxiv.org/abs/0808.1081v1. ^ Yu. V. Baryshev (2008). "Expanding Space: The Root of Conceptual Problems of the Cosmological Physics". Practical Cosmology 2: 20-30. http://arxiv.org/abs/0810.0153. ^ JA Peacock (2008). "A diatribe on expanding space". ArXiv preprint. http://arxiv.org/abs/0809.4573v1. ^ Michał J. Chodorowski (2007). "A direct consequence of the expansion of space?". Monthly Notices of the Royal Astronomical Society 378: 239-244. http://arxiv.org/abs/astro-ph/0610590v3.

-----------------------------------------------

 

The above is all in that Wiki article, backing their opinions. The conclusion is based on NOT accepting the premise of constant conditions (see their chart). If the U has been expanding, then the dynamics could not be constant over those periods of times. Note however, these are not my opinions and was offered only to argue your point of observations are of some mythical value IMO, where so much time and other conditions must have changed.

 

Yes, your correct, BBT is based on not only the unobservable, a hypothetical scenario, but according to our science an impossible one. A singularity that just happened to be laying around dormant and was somehow activated (in some kind of nothingness) to increasing in size at logically impossible velocity over a very short period of time for all we can see though out those same 12/15 billion years in progress...IMO. Some how I have just accepted the fact that mankind with all it's wisdom, represents only a fledgling/primitive idea of what actually could be answers in Astronomy/Cosmology.

[AO2012]

I guess I'm quite dumb, because what I can't get my mind around are black-holes. I don't know very much, but still I find the sky inspiring. I don't know at what rate this said increasing rate is at, or if ... it can exceed that of light ... if gravity is ultimately stronger than light, via black-hole, how could anything ever really expand to begin with, unless like there is something that can trap light, there is something that can accelerate it?

 

I find it very strange indeed, some shows I have seen, professing that quite possibly black holes are not the abnormality they were once thought to be, but much rather ... the more common opposite. And like mega hurricanes, tornadoes, and volcanoes ... there are even mega black-holes looming in the hub of galaxies! Holy yin-yang Batman!!

 

Would there be a mega-ultra-ginormous black-hole at the center of the universe? How did anything ever escape it? Would all these black-holes eventually collect each other and everything, or just everything in their way as the are pushed ever outward by something with a greater effect on gravity, over that which swallows light?

 

To me the question almost seems like saying, how big or small is infinitely ... either. Could it work both ways? I think of the "universe" like bubbles ... some expand till they pop, some cave in on themselves, like stars .... and there is seemingly an unquantifiable amount of them like stars ... did, does, will, the big-bang ever stop? Do black holes .. ever ... stop? How many of them are there? My little brain is about to pop, I'll stick to science-fiction.

 

I admire the hunt for more, and can only suggest that we simply do not have enough data, or the right kind, if we know what that is.

[Megabrain]

I'll pop back in here and say I am delighted it is being debated, all too often on these forums, posters merely regurgitate what they learned in class, many if told they could theoretically fly would take the word of the scientist and leap into the abyss, there are many examples where at least a considerable section of accepted scientific thinking was clearly ill thought out and wrong, my object is to get people to think outside the box, to accept the 'other way' and play with it, if it does not work then fine but merely quoting Einstein [ (an ex patent clerk who may have stolen ideas from others) and produced a hald arsed botched paper (which he later admitted he tweaked), failed to accept black holes and universal expansion, ] is to follow blindly like sheep.

[jackson33]

To me the question almost seems like saying, how big or small is infinitely ... either. Could it work both ways? I think of the "universe" like bubbles ... some expand till they pop, some cave in on themselves, like stars .... and there is seemingly an unquantifiable amount of them like stars ... did, does, will, the big-bang ever stop? Do black holes .. ever ... stop? How many of them are there? My little brain is about to pop, I'll stick to science-fiction.

 

I admire the hunt for more, and can only suggest that we simply do not have enough data, or the right kind, if we know what that is.

 

Why couldn't infinity go both directions. Everything we think we know about our Universe, it's massive size, volume and content could be reduced to a speck of dust floating around in your room and if your were there, your existence would be based from that perspective, then you could see another speck of dust and imagine the same thing...on and on. We could already be a speck of dust in another existence, and so on...We know smallest has been redefined many times in the past few years, talking in nano measurements or the Technology itself. Nano inch being one/billionth and when you think of what 156 Billion light years (Said diameter of this Universe today) and the distance of ONE second being a light second or 186,200 distant miles, infinity is logical opposed to a necessity, IMO. Even today version of BBT indicates an expansion with no end, which implies infinity. It's the search for answers or the human desire to understand that makes it all worth while. Science Fiction is interesting to you, because it forces the potential possibilities into the realm of possible. In fact many of todays science endeavors have come from ideas proposed in SF and SF itself is based on what may be tomorrows science...

[Megabrain]

I did read that the expansion will continue until the average temperature of matter comes within one planck degree of absolute zero, at which time the matter will dissappear, as more matter 'dissappeares' the universe would shrink and eventually implode, I think it has credibility, since we cannot achieve a temperature of Absolute zero within a planck degree.

[lucaspa]

I'll explain, the data we have that suggests the universe is expanding at an everincreasing rate comes from modern observations of photons which started their journey towards us up to 12 billion years ago,

 

No, the data comes from supernovae in galaxies much closer to us than 12 billion light years away (see references below). Plus, add the fact that there isn't enough matter in the universe to cause the contraction plus add the fact that there is a repulsive force causing the expansion to accelerate.

 

All this adds to the inference that the universe is going to expand forever and never contract. There simply is no force to make it contract.

 

BTW, rubber bands cannot expand infinitely. Any sapient species is going to find the modulus of elasticity of a rubber band. Yes, materials have things like Young's modulus, stress vs strain curves, etc. All of these show limitations to the elasticity of materials.

 

Some references with the data for you to look up to verify the summaries of conclusions I have given you:

5. A Watson, Clusters point to a never-ending universe. Science, 278: 1402, 21 Nov. 1997. Discusses paper that will appear in Astronomy and Astrophysics about the clusters that bend light from distant objects. The model predicts the number of such clusters we should see. With 33% of the critical mass the model predicts 2500 clusters. We see 2300-2700. Up the mass to the critical value and the predicted number drops to 25.

6. JP Henry, UG Briel, and H Bohringer, The evolution of galaxy clusters. Scientific American 279: 52-57, Dec. 1998.

7. Lineweaver CH and Davis TM Misconceptions about the Big Bang, Scientific American 36-45 March 2005. http://www.sciam.com/article.cfm?chanID=sa006&colID=1&articleID=0009F0CA-C523-1213-852383414B7F0147

7. J Glanz, Exploding stars point to a universal repulsive force. Science 279:651-652, 30 Jan. 1998. New data indicates the cosmological constant is back.

7a. J Glanz, No backing off from the accelerating universe. Science 282: 1249-1250, Nov. 13, 1998. As the title says, 2 independent and competing groups continue to get data that agrees.

8. G Tarke and S.P. Swordy, Cosmic Antimatter. Scientific American, 278(4): 36-41, April 1998.

10. CJ Hogan, RP Kirshner, and NB Suntzeff, Surveying space-time with supernovae. Scientific American, 280: 46-51, Jan. 1999. Studies indicate that the rate of expansion of the universe is accelerating.

11. LM Krauss, Cosmological antigravity. Scientific American, 280: 52-61, Jan. 1999. discusses cosmological constant to explain accelerating expansion.

13a. Web sites for expanding universe

http://www.cnn.com/TECH/space/9802/...ating.universe/

http://www.space.com/scienceastrono...celerating.html

http://www.er.doe.gov/Sub/Accomplis...scovery/43.html

4. J Glanz, Microwave hump reveals flat universe. Science 283: 21, Jan 1, 1999. Data on microwave background radiation indicates that universe is flat.

24. http://www.lpi.usra.edu/publications/newsletters/lpib/lpib77/black77.html Website has equations to calculate age of universe

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Merged post follows:

Consecutive posts merged

I did read that the expansion will continue until the average temperature of matter comes within one planck degree of absolute zero, at which time the matter will dissappear,

 

 

And where did you read that matter will disappear? Why should it? From what I have read (see references above), the data right now indicates that the universe will expand forever and eventually go into "heat death". That is, all the fusable material in stars will be used up, they will cease to shine, and the temperature of the universe will go toward absolute zero. Also, as space continues to expand, evetually no part of the universe beyond the solar system will be visible to us. Scientific American had an article on this a couple years ago entitled "The End of Physics".

[Megabrain]

No, the data comes from supernovae in galaxies much closer to us than 12 billion light years away (see references below). Plus, add the fact that there isn't enough matter in the universe to cause the contraction plus add the fact that there is a repulsive force causing the expansion to accelerate.

It comes from a range of galaxies up to 12Bn Light years, and as little as lets say 2million light years, that means the youngest data comes from a time when your and my ancestsors were probably squabling over sharing out bananas.

 

All this adds to the inference that the universe is going to expand forever and never contract. There simply is no force to make it contract.

 

Inference yes, that's all it is. and your second point is irrelevant I did not describe a shrinking, (in the sense of it being the opposite of expansion) I described the universe dissappearing at light speed wwhilst galaxies were continuing to blindly fly outwards.

 

BTW, rubber bands cannot expand infinitely. Any sapient species is going to find the modulus of elasticity of a rubber band. Yes, materials have things like Young's modulus, stress vs strain curves, etc. All of these show limitations to the elasticity of materials.

 

Oh please,..... yawn!!! read what I said NOT what you think I mean.

 

Some references with the data for you to look up to verify the summaries of conclusions I have given you:

5. A Watson, Clusters point to a never-ending universe. Science, 278: 1402

I note 'point to' as opposed to 'prove' would you like me to explain the difference?

 

 

THe rest of your quotes are also humpty dumpty.

 

And where did you read that matter will disappear? Why should it? From what I have read (see references above), the data right now indicates that the universe will expand forever and eventually go into "heat death". That is, all the fusable material in stars will be used up, they will cease to shine, and the temperature of the universe will go toward absolute zero. Also, as space continues to expand, evetually no part of the universe beyond the solar system will be visible to us. Scientific American had an article on this a couple years ago entitled "The End of Physics".

 

The operative word here is 'indicates' ie another points to, such phrases are insurance to a scientist, it means "I can't be wrong because I never said it was fact" Probably all the work you have read is of this lewis carroll standard

The facts are scientists can only say with absolute certainty that

 

"The data we have today, some of which is almost as old as the universe suggests that at the time it was originally generated the universe appeared to be expanding"

 

If you try to fill it out any more than that then you are stepping beyond what a scientist would commit to.

[Martin]

I did read that the expansion will continue until the average temperature of matter comes within one planck degree of absolute zero, at which time the matter will dissappear, as more matter 'dissappears' the universe would shrink and eventually implode, I think it has credibility, since we cannot achieve a temperature of Absolute zero within a planck degree.

 

I agree with Lucaspa on MBs speculations here. They don't make sense. Aren't science really.

 

MB you cannot possibly have read what you say you read, from any legitimate science source. Not even a respectable science journalist would say what you claim to have read. So it is just plain fantasy, or delusion.

 

One reason is that the Planck temperature unit is around 1.4 x 10³² kelvin.

That is we are already within one planck degree of absolute zero and matter has not disappeared.

 

And there is no reason for matter to disappear no matter how close we get, a microkelvin, a nanokelvin. Cold is not going to make matter disappear. To make speculations like yours, I suspect one would need to be unusually credulous, or imaginative to the point of inventing fantasy.

 

Also you claim to have read that when the universe gets to within a planck degree of zero (which it certainly already is) the universe will "shrink and implode".

 

Where did you read such an assertion! There have been big crunch collapse scenarios discussed but they are all accompanied by very high temperature. What you are offering us sounds completely "made up".

 

If you want to keep this a legitimate speculation/pseudoscience thread, then you should give your source link. Where on the web does it say these things?

 

If anyone is interested the NIST (national institute of standards and technology) defines the Planck unit of temperature, also see:

http://en.wikipedia.org/wiki/Planck_temperature

http://physics.nist.gov/cgi-bin/cuu/Value?plktmp|search_for=universal_in!

Edited April 20, 2009 by Martin

[lucaspa]

It comes from a range of galaxies up to 12Bn Light years, and as little as lets say 2million light years, that means the youngest data comes from a time when your and my ancestsors were probably squabling over sharing out bananas.

 

Well. So you admit that your Opening Post statement that the data was only from 12 billion years ago is wrong. A backhanded way of admitting it, but an admission nonetheless. We have data from much more recent (in cosmological time) than 12 billion years. In fact, according to you, we have data from as recently as 0.00016 the age of the universe! Do you really expect something universal to appear so recently?

 

Inference yes, that's all it is.

 

You are denigrating inference. We do inference all the time. For instance, Agassiz looked at the marks of rocks in Europe and inferred that those marks were caused by glaciers. "Inference" is another way of saying: "the inference is the hypothesis that has survived all the attempts to show it wrong". Science is the business of inferring.

 

and your second point is irrelevant I did not describe a shrinking, (in the sense of it being the opposite of expansion) I described the universe dissappearing at light speed wwhilst galaxies were continuing to blindly fly outwards.

 

Excuse me, but the Opening Post said: "If for example the universe began collapsing towards us at the speed of light then we would have no prior warning of this." That would be "contracting", unless you have some hypothesis about all the matter moving only towards us.

 

You said "I did read that the expansion will continue until the average temperature of matter comes within one planck degree of absolute zero, at which time the matter will dissappear"

 

If you meant "matter will disappear from view", then you should have said so. There's no need to get agressive with me when the problem lies with you being unclear.

 

As it happens, because it is space that is expanding, objects the farthest away from us are indeed receding faster than lightspeed and are no longer visible to us. But to say "disappearing" by itself means that the matter no longer exists, not just that we can't see it.

 

I note 'point to' as opposed to 'prove' would you like me to explain the difference?

 

Strictly speaking, science cannot "prove". Science can disprove using deductive logic, but it can't "prove". So a characteristic of science is that it is tentative. We base our conclusions on the data we have now with the understanding that, if and when we get different data, we will change the conclusions.

 

This happened in cosmology within the last 10 years. The inference was that Einstein's cosmological constant = 0 and that the ultimate fate of the universe depended on whether there was enough matter in the universe to halt the expansion begun at the Big Bang thru gravity. New data made us change our minds.

 

If you want us to change our minds, then present us with some data, not rhetorical arguments.

 

The operative word here is 'indicates' ie another points to, such phrases are insurance to a scientist, it means "I can't be wrong because I never said it was fact"

 

See above. What it means is "based on the data we have now, this is the only valid conclusion. If there is new data that contradicts the conclusion, then the conclusion changes."

 

What you stated in the Opening Post was:

"Suppose we establish contact with a nearby alien society and send them some everyday objects from earth among which is an elastic band.

 

So they play with this and slowly stretch it taking readings of length, after a while they get bored, look at the data and decide that this elastic band could be stretched forever but they don't have the time to put this to the test so they mark rubber as infinitely strechable.

 

What the hell has this got to do with the size of the universe I hear you ask well not a lot except that we seem to be applying this form of logic to where we think the universe is going."

 

I was pointing out that your analogy and logic were wrong because the aliens would not do what you state. Very soon they are going to get to the breaking point with the rubber band. What's more, as they take readings of stress as well as strain (how far the rubber band stretches), the data is going to indicate that the rubber band has an ultimate breaking point.

 

The only known force that would counter the expansion of the universe is gravity -- a universal attractive force. The data shows that there is a counter universal repulsive force (dark energy) that is stronger than gravity forcing the expansion of the universe. Now, you can be unhappy with the expansion and say "we don't absolutely know it will go on forever." However, with all we know now, the only valid conclusion is that the expansion will continue forever. You are speculating and placing bets on data that doesn't exist. You can personally do that, but it isn't science.