Universe expansion

[ollypenrice]

We cannot determine based on one attribute alone, Redshift alone cannot determine whether it is expanding or collapsing, the paper I linked basically uses another attribute. Redshift has been shown to be erronus too. Expanding universe is one of many theories, that is all it is, a theory, I really hate it when people treat it like fact, it is anything but fact, but mearly a hypothesis, that has other hypothesis throwing it into question, like the paper I linked earlier.  using the attribute they used, it states the universe is static.

Remember some galaxies have been shown to have unusual redshifts when they are apparently phyiscall connected/interacting. The paper I linked uses the surface brightness, which should be lower on further away galaxies, however it was constant between nearby and far off galaxies, this contradicts the expanding universe thesis.

Theory should never be confused with fact and no serious scientist ever does confuse the two. Nor should hypothesis ever be confused with theory, though plenty of people do confuse the two...

An hypothesis is the starting point for a theory before it has undergone testing against observation, before it has made successful predictions and before it has been scrupulously peer-reviewed. 

At what point does it become fact?  Never. 

Olly

[ollypenrice]

"Andromeda is changing line into ours." was the part I was responding to. The idea that M31 is doing the moving.

My understanding is that nothing in the universe travels in a linear manner. All moving in various curving paths. Therefor MW and M31 are each moving into each others paths, although at different rates of angular change.

A useful term when thinking about what you here call a 'linear manner' is 'geodesic.' A geodesic is the shortest possible trajectory through spacetime. When spacetime is curved (as it always is to some extent) the term 'straight line' becomes - peculiar!  An object in gravitational free fall follows a geodesic. A geodesic is a generalized straight line which still makes sense when spacetime is curved by gravitation.

Pours gin and tonic.

Olly

[cathouse42]

Just going to read it now, though on a quick skim read, they are basing some of their assumptions on 'some other unknown factors'... But let me read it first. 

The traditional big bang model first hypothesised by Hubble has already been shown to be largely incomplete, however, the theories of expansion when combined with the big bang suggest a fractal universe which the CMB supports to a very large extent.

Also remember, just because it has been peer reviewed, doesn't mean that it has been accepted as accurate As they implied in the introduction to the first paper you linked to, if it turned out to be true, it would rewrite our knowledge of the cosmos. Unfortunately, relativity substantially backs up many of the claims of expansion and relativity itsself has passed every test it has been given so far.

You can just enter "Expanding universe" into Google Schollar to get a huge list of papers.

you can also use the DOI index to find lots of interesting papers. Some are public access some require subscription. That is the world of Journals Each with their own peer review policies and cross publishing is NOT allowed by authors, the only way a paper can be cross published is by aggreement between jouransl (for example ACM and IEEE cross publish by their own agreements but WE cannot publish to more than ONE Journal).

The second paper Is one I found that was public accessible. I do have access to paid journals though.

But there is many interesting theories, hence why I firmly believe one attribute and one alone is not grounds for a solid theory on a scale with many influencing factors such as a universe lol.

[Tiny Small]

Except the many prediction of relativity and many other theories back up the conclusions drawn from observing red shift, so it isn't a single attribute.

[kalasinman]

As I have been trying to point out, many ideas have been put forth. As the jury is still out, and will be for some time,  I don't believe that extrapolating from data well over a few billion years old is reliable. That is unless you believe that we can apply Newtonian physics to the  universe. We seem to make the assumption that the universe is expanding at an increasing rate based on observations that light from more distant objects is more red shifted. As these objects are further away in time, perhaps they are merely showing inertia left over from inflation, and slowed to match the rest billions of years ago and the light hasn't gotten here yet.

If dark energy repels mass and there is a multiverse, then at some point mass from our universe would interact with another. Would the 2 dark energies not then repel the 2 universes from each other.? Would this not create an oscillating universe as mentioned by Carl Sagan (and BTW postulated by Indian science for 3,000 years or so)?

To be factual, all we can say is that galaxies were moving away from each other some time ago.

[cathouse42]

So according to the "big bang" theory, galaxies brightness should be fading over distance and their size getting larger. Surface brightness should be less for distant galaxies than nearer ones. Light is also stretched over distance therefore also dimming them.

This would be the case if the Universe was not expanding, ie., static.

Redshift could be caused by something else. Perhaps.

[ollypenrice]

So according to the "big bang" theory, galaxies brightness should be fading over distance and their size getting larger. Surface brightness should be less for distant galaxies than nearer ones. Light is also stretched over distance therefore also dimming them.

This would be the case if the Universe was not expanding, ie., static.

Redshift could be caused by something else. Perhaps.

Why would their size be getting larger? Galaxies are gravitaionally bound so that, internally, they overpower the Hubble Flow. Expansion occurs between galaxies, not within them.

I think that the evidence for an acceleration of the expansion now taking place is young and could possibly be mistaken, though I find it compelling and, more significantly, so did the Nobel committee. However, arguing against the expansion itself, rather than the rate of the Hubble Flow variously over time, is going to take some doing.

As has been pointed out before on this thread, the redshift alone cannot be used to dervive the rate of expansion. What is needed is a distance determinant against which the observed redhift can be compared. This has tended, I think, to come from type 1a supernovae which are now available almost 'on demand' using large scope technology working at cosmological distances. I suppose the worry must be that early Type 1a SNs might have behaved differently from present ones. However, the evolution of their ight curves agrees with the predictions of relativistic time dilation which I think is just incredibly cute! Take a bow, Albert. 

Another interesting bit of expanding universe theory is this; if you use the redshift to give a distance to a galaxy and then use a different method like the Tully-Fisher (which derives a brightness from roation velocities and seems pretty stable) then you get a slight disagreement. The marvellous thing is that this disagreement is non-random. In particular parts of the universe the differences in measured distance, if connected by lines in a 3D map, tend to point in the same general direction. But this will be a different general direction in other areas. The interpretation here is that what we are seeing are the galaxies 'beating against the current' of the Hubble Flow under the influence of great unknown sources of attraction. 

Olly

[CedrikG]

Thanks a lot everyone for your answer, your point of view and the small debate. Extremely interesting thread.

[Tiny Small]

I think that the evidence for an acceleration of the expansion now taking place is young and could possibly be mistaken, though I find it compelling and, more significantly, so did the Nobel committee. However, arguing against the expansion itself, rather than the rate of the Hubble Flow variously over time, is going to take some doing.

As has been pointed out before on this thread, the redshift alone cannot be used to dervive the rate of expansion. What is needed is a distance determinant against which the observed redhift can be compared. This has tended, I think, to come from type 1a supernovae which are now available almost 'on demand' using large scope technology working at cosmological distances. I suppose the worry must be that early Type 1a SNs might have behaved differently from present ones. However, the evolution of their ight curves agrees with the predictions of relativistic time dilation which I think is just incredibly cute! Take a bow, Albert. 

Olly

Exactly, though I find the evidence of acceleration very strong indeed. As to arguing against the expansion itself, don't forget the CMB. The fact that temperatures of the CMB are almost exactly the same, to billionths of a degree, across the entire cosmos can only really be explained by the expansion expected as a result of an explosive start to the universe from a singularity.

[kalasinman]

Exactly, though I find the evidence of acceleration very strong indeed. As to arguing against the expansion itself, don't forget the CMB. The fact that temperatures of the CMB are almost exactly the same, to billionths of a degree, across the entire cosmos can only really be explained by the expansion expected as a result of an explosive start to the universe from a singularity.

Actually it can only be explained in the case of inflation, a faster than light expansion initially. We therefor have evidence of a different rate of expansion than what Hubble saw.. There is no "young data" . All of what we have trickles in at speed of light. Even data from Andromeda is over 2 million years old. Although it is convenient to assume that the rate of expansion, or even the rate of change has remained constant, there is no fresh evidence to support that assumption in the case of distant objects.

[ollypenrice]

Actually it can only be explained in the case of inflation, a faster than light expansion initially. We therefor have evidence of a different rate of expansion than what Hubble saw.. There is no "young data" . All of what we have trickles in at speed of light. Even data from Andromeda is over 2 million years old. Although it is convenient to assume that the rate of expansion, or even the rate of change has remained constant, there is no fresh evidence to support that assumption in the case of distant objects.

Yes, but we might expect the age of the data, if growing old made it unreliable, to create problems in spectroscopy, for instance. But it doesn't. The elements remain as easily identifiable in old light as in new. That, for me, argues that old light is still good light.

Olly

[kalasinman]

If I understand it, red shift does indeed shift the lines in spectroscopy. The relationship of the lines to each other doesn't change, as the periodic table isn't affected by Doppler shift. Seems to me that there are five possibilities: no expansion, constant expansion, accelerating expansion,  varying expansion, or contraction. There seems to be evidence supporting the latter and inflation seems to also establish that considerably different rates have existed than what we see now. The universe is full of surprises, witness the discovery of the quantum world and uncertainty.

Just as there is a somewhat different set of "rules" at the quantum level, could there also be another at present unknown set of rules governing the macro cosmic?

We know next to nothing about 75% of matter in our universe, and only a tiny bit more about another 20%. Given that much of our data is ancient, it seems a bit early to hang ones hat on any conclusion at this point. Old data is what it is. At extreme distances we simply know nothing about what has actually happened over the ensuing billions of years, and like never will have more current data.

As Carl Sagan pointed out, our existence as a species has occurred  in 7.7-5 of the estimated life of the universe.

[kalasinman]

"There seems to be evidence supporting the latter and" this was wrong after I edited and added more possibilities. Should have been removed, sorry

[ollypenrice]

Some wag once said, 'Cosmologists are often in error but never in doubt.'

lly

[cathouse42]

Some wag once said, 'Cosmologists are often in error but never in doubt.'

lly

I don't doubt they're in error.

[ollypenrice]

To be fair, good scientists are acutely aware of the Feynmanism, 'Science is a culture of doubt.'

To be sure is not to be scientific but to be doggedly pig-headed is fine...

lly

[Tiny Small]

Actually it can only be explained in the case of inflation, a faster than light expansion initially. We therefor have evidence of a different rate of expansion than what Hubble saw.. There is no "young data" . All of what we have trickles in at speed of light. Even data from Andromeda is over 2 million years old. Although it is convenient to assume that the rate of expansion, or even the rate of change has remained constant, there is no fresh evidence to support that assumption in the case of distant objects.

Yes. I really should have made what I meant clearer, and that is that it suggests inflation which is included in newer iterations of the big bang theory, all of which support expansion.

Whilst this is all interesting to discuss, I find it odd that, despite the absolute wealth of evidence (redshift, density measurements, spectroscopy, standard model predictions and all the other methods that either directly correlate to an expanding universe, or support the evidence that does), you don't support expansion, but instead choose to support alternative theories despite the lack of credible evidence from reliable and appropriate sources. There really are very few cosmologists that don't support expansion. Hubble's favoured view of a static universe has pretty much been shown to be incorrect. To form a proof, you need lots and lots of examples and experiments. To disprove a proof, you only need a single counter example. I don't mean this as a personal attack, just that I do really find it odd. But then, I find it amazing that there are millions of engineers out there that still cling to a belief in a higher power, despite having an excellent understanding of the basic (and in some cases, very advanced) sciences.

If substantial and compelling evidence was presented to the contrary then I would change my opinion, but to date, I haven't seen anything to sway me.

[kalasinman]

Yes. I really should have made what I meant clearer, and that is that it suggests inflation which is included in newer iterations of the big bang theory, all of which support expansion.

Whilst this is all interesting to discuss, I find it odd that, despite the absolute wealth of evidence (redshift, density measurements, spectroscopy, standard model predictions and all the other methods that either directly correlate to an expanding universe, or support the evidence that does), you don't support expansion, but instead choose to support alternative theories despite the lack of credible evidence from reliable and appropriate sources. There really are very few cosmologists that don't support expansion. Hubble's favoured view of a static universe has pretty much been shown to be incorrect. To form a proof, you need lots and lots of examples and experiments. To disprove a proof, you only need a single counter example. I don't mean this as a personal attack, just that I do really find it odd. But then, I find it amazing that there are millions of engineers out there that still cling to a belief in a higher power, despite having an excellent understanding of the basic (and in some cases, very advanced) sciences.

If substantial and compelling evidence was presented to the contrary then I would change my opinion, but to date, I haven't seen anything to sway me.

I don't recall writing anything that disputed expansion or inflation as taken from the evidence we have.  Based on what we know now, an accelerating expansion is a logical conclusion. The evidence from the CMB clearly implies that the expansion has perhaps exceeded the speed of light at one point. I'm saying that if the evidence shows that the expansion can proceed at different speeds, both slowing and speeding up, it's reasonable to conclude this may have happened already in the last few billions of years and we haven't seen the evidence yet.

[michaelmorris]

Hi guys

With the discussion straying into comments about "higher powers" please remember SGL's code of conduct - no religion

[mikeDnight]

Not quite as that would indicate a negative acceleration, or a slowing down as you move from the big bang to our present time. The way expansion is measured is through red shift. Every element in the universe emits light in one form or another and has a signature embedded into the emitted light. It shows up as absorption lines. As the origin moves and or accelerates away from us, these (unique) signatures are moved to the red end of the spectrum as the light wave is stretched out. This means that if something demonstrates redshift, it is further away from us now than it was in the past. Now, knowing that if a source of light moves away from us, it will redshift and if we know the source of light has a constant velocity, we can calculate how much it should be red shifted by, however, when we look into space almost everything we look at (Andromeda is on of the few exceptions as it's moving towards us) has a much greater redshift than it should have, meaning a positive acceleration. Repeated observations confirm a constant acceleration (meaning that the positive change in speed or direction is a constantly increasing change) and therefore, the universe really is expanding and the expansion is accelerating.

Wiki has some useful things to say about redshift; http://en.wikipedia.org/wiki/Redshift

Red shift is a useful indicator for such things as determining the rotational direction of a galaxy etc, but the theory that the universe is expanding faster the further away we look is simply nonsensical. Where is the energy coming from to allow for this expansion? Some galaxies have been measured as moving apart from eachother faster than light. The whole thing is simply rubbish, needing mythical, Alice in Wonderland hypothesis such as Vacuum Energy.

Often in science the simplest answers are usually the right ones. In this case Red Shift is the stumbling block. At extreme distances it simply cannot be relied upon as a measure of recession, there is something else at play here.

Rather than thinking of light as a wave which is stretched leading to red shift, view it as a quanta of energy, which is what it actually is. A high energy photon coming our way from a distant galaxy has mass. Most scientists believe the mass of a photon to be so insignificant as to be ignored completely. That's an error on their part.

The photon coming our way will regularly throughout its vast journey hit other various subatomic particles. With each such collision our photon will lose energy, so in actual fact it is not the same photon, as it is now of a different energy level, therefor as our high energy photon loses energy it moves towards the red end of the spectrum. This implies that far from being a measure of recession, red shift becomes an indication of distance and not expansion.

Perhaps the microwave background radiation that seems to flood our universe is the visible aftermath of higher energy photon collisions?

[kalasinman]

Red shift is a useful indicator for such things as determining the rotational direction of a galaxy etc, but the theory that the universe is expanding faster the further away we look is simply nonsensical. Where is the energy coming from to allow for this expansion? Some galaxies have been measured as moving apart from eachother faster than light. The whole thing is simply rubbish, needing mythical, Alice in Wonderland hypothesis such as Vacuum Energy.

Often in science the simplest answers are usually the right ones. In this case Red Shift is the stumbling block. At extreme distances it simply cannot be relied upon as a measure of recession, there is something else at play here.

Rather than thinking of light as a wave which is stretched leading to red shift, view it as a quanta of energy, which is what it actually is. A high energy photon coming our way from a distant galaxy has mass. Most scientists believe the mass of a photon to be so insignificant as to be ignored completely. That's an error on their part.

The photon coming our way will regularly throughout its vast journey hit other various subatomic particles. With each such collision our photon will lose energy, so in actual fact it is not the same photon, as it is now of a different energy level, therefor as our high energy photon loses energy it moves towards the red end of the spectrum. This implies that far from being a measure of recession, red shift becomes an indication of distance and not expansion.

Perhaps the microwave background radiation that seems to flood our universe is the visible aftermath of higher energy photon collisions?

Love to agree with you as red shift relies on ancient data which cannot be confirmed. However, to agree with you, one would have to deny General Relativity. By definition, photons travel at light speed and therefore if they had any mass at all it would have increased infinitely at light speed, making one photon the heaviest object in the universe.

[DRT]

What a fascinating discussion, most of which I struggle to understand

One serious question I have about the accelerating expansion theory is what is the force that is acting upon the objects in the universe to make them accelerate? I get that the Big Bang would have created a shock wave causing initial acceleration but presumably that shock wave dissipated many millions of years ago? So what is pushing or pulling everything now to maintain the acceleration?

[ronin]

One serious question I have about the accelerating expansion theory is what is the force that is acting upon the objects in the universe to make them accelerate?

The objects are not accelerating away, the space between the objects is expanding/accelerating.

Bit like putting a bag on a rubber walkway at an airport, the bag is not moving but it will get further away.

The bag is the galaxy, the rubber walkway is space/time.

Another bit is nothing "in" space-time can move faster then the speed of light, but space-time itself can, so, in a way, galaxies far enough away are receeding away from us faster then c and can/will never see them. More correct term would be "carried away" from us.

The acceleration is caused, in simple terms, by that lovely item called Dark Energy.

Dark because we have no idea, Energy because to expand anything (well we think anything) takes energy.

Another term is, or may be, vacuum energy.

Quite a bit of this assumes that space-time operates in a similar way to materials we see here on earth, there seems little reason for this presumption. Consider if a fundimental property of space-time was simply that it always attempts to get as far away as possible from every other bits of space-time.

One other aspect to consider is that Einstein did have a solution to GR or SR that at great distances gravity could be negative and so become repulsive not attractive. That solution was discarded as non-sensible. Gravity attracts doesn't it ??.

[DRT]

The objects are not accelerating away, the space between the objects is expanding/accelerating.

Bit like putting a bag on a rubber walkway at an airport, the bag is not moving but it will get further away.

The bag is the galaxy, the rubber walkway is space/time.

But the bag is moving away from me relative to where I am standing and relative to everything else, including the bag. Isn't it?

Would I be right in thinking that there is a common, very well researched, robust and predictable theory that the universe is expanding at an accelerated rate and the hypothesis that the acceleration is caused by a mysterious, unexplained and unobservable thing called "Dark Energy", which means we really don't know why it is accelerating or what the force causing it to do so actually is?

That would be good enough for me as it leaves the door open for more wonders to be discovered

[Piero]

Another bit is nothing "in" space-time can move faster then the speed of light, but space-time itself can, so, in a way, galaxies far enough away are receeding away from us faster then c and can/will never see them. More correct term would be "carried away" from us.

Could you explain why space-time itself can go faster than  the speed of light? To understand this a bit better it would be also helpful if you could provide some example of this and what are the consequences of this. 

Thanks