Are there other ways to explain redshift than an expanding universe?
It gets fairly problematic coming up with an alternative to the Big Bang. As time passes, there is more and more evidence consistent with the BB. For example, there is the Cosmic Background Radiation (essentially identical in all directions) and the discovery of high redshift galaxies at large distances.
Consequently, it takes a fairly useless ad hoc alternative theory to explain the current facts as we know them. Such a theory is useless unless it can make a prediction which distinguishes it from the current standard model.
By the way, the redshift arises in large part to the ongoing inflation of the universe, which is traced back to the very early universe (i.e. vicinity of first 10^-35 second).
There is the "tired light" theory. It proposes that light waves slowly flatten out as they travel. This would result in spectrums shifted further and furthuer toward the red as the light gets older.
This theory has a lot of problems, though.
The key thing is not just explaining the redshift, but the CMBR too, particularly it's isotropy. There are a number of theories that try to offer alternatives none are really satisfactory.
Dr.- Chinese I'm not sure what you mean by:
The inflation era started at about 10^-35 secs but it ended before the first second, which is hundreds of thousands of years before the earliest em radiation currently observed (technically the CMBR) was emitted and therefore it can account for none of the redshift. That said the word 'inflation' in astronmy, though almost universally is used to refer to the early period of exponentially accelerating expansion in the universe, actually just means 'accelerating expansion' and current observations suggest that the universe could currently be expanding at an accelrating rate.
It is possible to have expansion w/o a temporal big bang beginning - Harrison in his book on cosmology describes a number of different cosmic models that expand, but not from a singularity. One idea of interest is exponential expansion - most things in nature grow in proportion to the amount in existence e^kt - and what is more natural than the universe itself - in this model there is no need to explain chronometric beginning since time approaches 0 asympotically as you wind the clock backward.
Excellent! Lots of different answers!
(1) N0 : Redshift is caused by the expanding universe w/ Big Bang
(2) YES: Because Redshift might be a property of light
(3) NO : But w/o Big Bang; instead natural exp expansion
Please tell me if I have misinterpreted your answers.
One anti Big Bang site suggested that light might be interacting with clouds of molecular hydrogen and that this interaction might explain redshift.
Would clouds of interstellar molecular hydrogen explain redshift?
Would the interaction be refraction?
While I know how refraction works, I do not understand WHY it occurs.
Thanks for your responses.
There is a minority of thought that does not accept the notion of a big bang event - I can never figure out what prompts such resistance - it must be something to due with the fact that a happenstance created the universe - maybe these folks resent the inuendo that no special act of creation is involved - interestingly, the first person to suggest the abrupt beginning was a priest -
I think it was Asimov that said: "There is no idea, however foolish, that will find adherents who will defend it to the death."
Not at all. The BB model has plenty of holes in it, and anyone serious about learning the truth should be sceptical of such unsupported claims. The reasoning you give (about resenting the possibilties suggested by a certain model) apply just as well to those who continue to cling to the BB model inspite of observational evidence to the contrary.
But claiming a psychological motive to everyone who's view differs from our own is no way to find the truth. Clinging to BB ideas because of tradition or rejecting them to oppose tradition are equally unsupportable positions. This case must be decided on evidence, not sentiment. And right now, evidence seems, IMHO, to oppose the BB. For those of us who belong to this "minority of thought", this position will not change untill and unless further evidence can be discovered.
Hi Lurch - I find no fault with what you have said - there is no reason to cling to any idea if the evidence is contrary - my experience has been that those who vehemently attack expansion, finite universe concepts, temporal beginnings etc, are motiviated by religious bias - granted some of them have no idea at all as to the evidence on either side - and some will not admit to the bias. Perhaps in the last analysis, we are all biased. Myself, I admit to having deep conceptual difficulty with a temporal beginning - but no problem with the dynamics of expansion.
In the beginning there was nothing, and God said: "Let there be light"
And still there was nothing, but you could see it!
The Big Bang may have been a quiet expansion if the universe oscillates between a bang and a crunch.In this scenario spin half particles racing towards a singularity pair up into spin one massless particles and the resulting bosons pass through each other and expand causing an expansion in the opposite direction from which they came.
Would you care to share some of that evidence with us LURCH?
In so far as it's relevant, what are the alternatives to a BB theory, which equally well account for a) the CMBR, b) the Hubble redshift-distance relationship, and c) the observed primordial abundances of H, D, He-3, He-4, and Li-7?
The only proponents of the silly "tired light" notion I'm aware of are creationists. (To "explain" how we are able to see light from things further than 6,000 light years away -- Light used to be faster.)
Not the least of which is it isn't a scientific theory.
Also, the only person who was seriously pushing this (I don't recall the name) has apparently got some very serious problems with his data and analyses.
Hey guys - I am not an advocate of the No Big Bang Theory - but a person is entitled to express a view w/o it being called silly or crackpot - every theory dealing with ultimate questions has serious problems - inflation, cosmic acceleration, on and on - lets face it - we don't have any idea why the electron charge is what it is, or why G has the value it does - and so on. Afortori - we don't have anything but speculation
No one is 'silly or crackpot' for expressing a view
And current cosmological theories have lots of things that don't quite add up - observations that are rather too imprecise to constrain anything much, an apparent inconsistency here or there ... not to mention the *total* inability of GR and QFT to apply to the first ~10-43s
However, if there are some other ideas around, let's discuss their merits, from the POV of the data that we have to hand, esp that which can be well accounted for with the BB theory.
Perhaps my interpretation of the 'tired light' reference was wrong; what I recalled was a claim by Barry Setterfield, which I now see (having looked it up) isn't called 'tired light'.
There's also a new theory called Plasma redshift , that claims that cosmological redshift is due to an strange interaction of the photons with plasma that they find through its voyage through space. Plasma redshift was proposed in this paper
meteor didn't mention some other claims in this paper, for example:
- "... a simple and natural extension of the classical TGR to quantum mechanics leads to gravitational repulsion of the photons, which causes their blue shift as they travel from the Sun to the Earth. This change in frequency is closely related to the increase in velocity of light with the gravitational potential."
- it follows that "[t]he repulsion of photons means that the energy density of all photons corresponds, in some respect, to a negative mass density" (this is important because otherwise Brynjolfsson's IGM contains far too much (baryonic) mass
- the IGM is essentially an electron-positron plasma, with protons playing only a minor role
- SN only appear distant in high(er) z galaxies because much of the light from them is scattered away from our line of sight
- the CMBR originates from "absorption and emission of the radiation by microscopic dust particles in space" whose temperature is ~2.7K
- a new explanation for how the arms in spiral galaxies arise and are maintained
- relativistic jets observed from black holes originate at intense beams of high energy photons being repelled by the intense gravity of the BH.
As you might expect from such a radically different view, lots of questions are left unanswered, even though the paper is already 67 pages long.
Brynjolfsson himself says that he will examine gravitational lensing in a future paper, and proposes several tests of his idea, including more extended versions of historical experiments generally regarded as validating GR.
Nonetheless, I feel Brynjolfsson has a great deal more 'unexplaining' to do. For example:
- (spiral) galaxy rotation curves
- CMBR dipole
- binary pulsars
- anisotrophy of the IGM (Brynjolfsson uses some kind of 'average' value for temperature and electron density)
- Cepheids and other key rungs on the distance ladder
- variation in observed SN light-curves due to differences in local and line of sight plasma densities, compositions, and temperatures
- the Lyman forest.
Finally, Brynjolfsson's idea has some similarities to Thomas2's, as posted earlier to PF's own General Astronomy & Cosmology sub-forum.
speculation and richard feynman
"we don't have anything but speculation."
Richard feynman said that particle physics is so imprecise that the average man on the street has as much chance of getting the mass of the next particle to be discovered in an accelerator right.He also said that he thought
that his lectures were his greatest legacy to science.Doesn't sound as though he had much faith in his quantum field theory!
Yes, I agree with what you are saying. One of the problems with the early inflationary scenarios was that it started and stopped within the periods you described to make the observed isotropy work out. More recent scenarios allow inflation to be a continuing force in the universe, but not causing exponential expansion as in the early era. As you say, recent observations seem to support this.
Consequently, much of the observed redshift is due to an apparent (i.e. observed) velocity component imparted by ongoing spacetime expansion in turn fueled by inflation. Such inflation is still occuring and never completely stopped, even if its contribution is decreasing. In approximate terms:
Light from a galaxy receding from us with a redshift of 6 - having been emitted when the universe was .75 billion years old in an area of space that was at the time 3 billion light years away - took 13 billion years to reach us. That galaxy was receding from us at 3c and is now 46 billion light years away.
Thus the (inflating) expansion of the universe explains the CMBR isotropy AND observed high redshift objects in the universe very well. Competing theories have a high hurdle to cross.
Quite the opposite, not sure where you are getting that from but it is hardly representative of anything. Current theory is very precise on many levels and hardly speculative. That is why competing theories rarely get very far.
Good Post Dr Chinese - I guess we are all tempted to applaud ideas that are consonant with our own - I had concluded some time ago that inflation is an ungoing phenomena - it explains a lot of things - the fact that perhaps matter is continually created by expansion of the false vacuum - this leads to an intrinsic "critical density universe" Moreover, if the universe is under tension as per a false vacuum - the spatial medium can act like a string under tension so as to support transverse em waves, etc. Actually Alan Guth has advanced the same hypothesis - the thing that is troubling about the traditional "inflationary model" is that there must be something that turns it on and off. That always bothers me.
That bothered me greatly as well. So I like the new ideas on this that allow inflation to continue into today, though playing a much smaller role.
That is the great thing about an evolving standard model (actually in any area of science). You can trade off one fuzzy assumption for another until some real progress is made, and clear benefits appear in one of the competing theories. Inflation seemed sort of ad hoc and useless, until "all of a sudden" it fit nicely! Of course, that "all of a sudden" represents many years of analysis and wrong turns. So hats off to Guth and the others who have contributed so much on that!
I like yours discussion. I thought of it much. On ‘’big bang’’ you can read my sight: http://bigbang.iatp.ge/en-version.htm [Broken]. I shall be glad to your remarks.
The Cosmic Background Radiation is one of the main evidences for the Big Bang Theory (really nailed in place by the COBE satellite which showed that the CBR matches blackbody radiation, as expected, to an amazing degree of accuracy). In the past (ok, today too), some steady state theorists suggested that you could get similar observational evidence from uniformly distributed intergalactic dust that absorbs & re-emits microwave radiation. But that material would have to be so thick that distant galaxies would not be visible. And of course, they are visible.
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