Question by David Morgan
I am only a layman and not an academic but I would be grateful to receive a response to my question, below.
I understand that the most distant galaxies from earth are accelerating away from us faster than the nearer galaxies. (On the basis of their red shift readings). Assuming the light from a distant galaxy has taken say 12 Billion years to reach us and the light from a nearer galaxy say 2 billion years to reach us If the distant galaxy is travelling faster than the nearer galaxy couldn't you say that 12 Billion years ago galaxies were travelling apart faster than they were 2 Billion years ago. This suggests to me that the rate of expansion is slowing down and not accelerating.
Where have I gone wrong in my thinking ?
Reply
The observation that Hubble made almost 100 years ago is that more distant galaxies have a larger redshift than galaxies closer to us, and that this relationship is linear. So, to take your figures, a galaxy 12 billion light years away has 6 times the redshift of a galaxy 2 billion light years away. Now, first of all, it is a mere theoretical assumption that the observed redshift is linked to recessional velocities (Hubble himself never fully subscribed to this interpretation, which in fact is
logically and physically flawed). But even assuming we are dealing with recessional velocities here, there is no implication that any of the galaxies are accelerating. On the contrary, you can only have the observed linear relationship if their velocities are constant. As an illustration, consider an explosion where the fragments are flying away with different velocities. If each fragment has a constant velocity, the distance covered within a given time will be exactly proportional to its velocity, that is a fragment with velocity v
1 will travel a distance x
1=v
1.t within time t, whereas the fragment with velocity v
2 will be at distance x
2=v
2.t, so the ratio x
2/x
1=v
2/v
1= const., which is nothing but Hubble's law. As long as the velocities of the fragments are constant, it doesn't even matter that you see the fragments at different times due to the finite speed of light. You see a galaxy that is 2 billion light years at the distance and with the redshift it had 2 billion years ago, but a galaxy that is 12 billion light years at the distance and with the redshift it had 12 billion years ago. Now this 'time layering' doesn't matter if the velocities are constant, because the redshift of each galaxy would never change with time. The distance changes of course, but by the same proportion for both galaxies (if the distance for the slow galaxy doubles, the distance for the fast galaxy doubles as well), so the distance/velocity ratio would change by the same factor in the same time, which means the different travel times of the light signal to us do not affect the Hubble law as such. However, if the velocity of the galaxies would be increasing with acceleration 'a' (rather than being constant), there will be the same velocity Δv=a*t added within time t; but as you observe the further galaxy 2 at an earlier time than the closer galaxy 1 i.e.as t
2<t
1, we have Δv
2<Δv
1, that is the further galaxy has less redshift added due to the acceleration than the closer galaxy. This means that with increasing distance of the galaxies, the redshift is increasingly smaller than expected on the basis of the linear Hubble law. Or you can see it the other way around: the apparent distance (as judged from the brightness) gets increasingly larger than expected from the observed redshift. This is at least what the data are claimed to show (see
this reference), but if you look at the given data points in Fig.2 in this reference, then this does not appear at all obvious, contrary to the claim made towards the end of the figure caption (if the data would somehow relate to either of the dashed curves in Fig.2, it should be obvious to the naked eye, which it clearly isn't). A very recent re-analysis of the supernova data also concludes that an acceleration does not conclusively follow from the data (see
this reference).
Anyway, as indicated above already, an expansion of the universe (whether uniform or accelerated) is a flawed physical concept as it violates mass conservation. The redshift
must be due to causes other than a recession, and I have suggested a mechanism for this on my page
Plasma Theory of the Hubble Redshift of Galaxies and, based on this, on my page
Galactic Redshifts and Supernova Light Curves I have also given an explanation for the fainter than expected objects at larger distances that has led to the conclusion of the accelerating expansion (if that could be substantiated by the data at all).
Question by Tom
I recently read the articles on the pages regarding the
Expansion of the universe and
Edwin Hubbles view of this concept.
I only have a somewhat limited understanding of cosmology, so my question can be elementary and be totally missing the point.
From what I understand, physicists would probably counter your statement about expansion and density by saying that space itself is expanding, so it is possible for the concentration of galaxies in all 3D boxes to decrease (becoming less dense), without violating mass conservation. As I understand it, they would say that the boxes themselves are having larger and larger volumes, so density decreases for all arbitrarily drawn 3D boxes that make up the entire universe.
Would they say that? If so, how would you respond?
I don't know how one proves any of this or maybe, deep down, we (or physicists in general) just declare a theory as an explanation absent of any other explanation (as you, Vincent Sauve, and even Hubble himself have written). In science, the attitude is that if no experimental data violate our theory (or rather, there is still not enough data that we can't ignore which contradicts the accepted theory yet), then we consider the theory valid. I would assume that an astrophysicist can look up a microscope and do some math. I would say some particle simulation is possible but i don't know how available those really are to actual physicists that do the work.
Reply
It is well acknowledged by cosmologists that rigid structures (or even gravitationally bound structures like our solar system or galaxies) are not expanding together with the 'Hubble flow', as the force responsible for the latter is much too small. So if the distance between galaxies would be continuously increasing, the number of of galaxies would be decreasing in
all of the grid boxes, so mass would be continuously lost in the universe (this is essentially the argument I have given on my page
Expansion of the universe debunked).
On my page
Plasma Theory of Hubble Redshift of Galaxies I have suggested an alternative redshift mechanism that avoids the logical inconsistencies associated with an expanding universe. It suggests that light waves are simply stretched in intergalactic space due to the electric field between the charges as long as their wavelength is smaller than the average distance between charged particles. This means that the redshift effect would actually break down for wavelengths long enough (probably in the meter region), and some recent observation show actually an indication of this (see
this paper where they find that the redshift is reduced by about 3% in the radio region compared to the visible region).
Comment by Amrit Srečko Šorli
Reading your article
The Big Bang Theory - A Flawed Concept I feel better, I'm not the only one who knows the Big Bang model is religious dogma. We published recently an interesting article about
Evidence-Based Cosmology.
Reply
Yes, as shown on my page you quoted, as well as on my page regarding the
Expansion of the Universe, the Big-Bang theory is a naive model that violates fundamental logical and physical principles. The observed systematic redshift of galaxies with distance can therefore not be related to recessional velocities (which by the way even
Hubble never accepted as the cause of the redshift.) So the crucial task here is to find the actual physical explanation for the fact that the 'cosmological' redshift is a linear function (more or less) of distance, i.e. for the Hubble law. In this respect, I have suggested an
alternative redshift mechanism caused by the electric microfield in intergalactic space. This is a,, hitherto unknown, fundamental physical effect which can not be reproduced in the lab as it is so weak that it only becomes apparent over cosmological distances. The interesting thing is that this effect should break down for large enough wave lengths (probably in the radio region), and evidence for this was indeed recently provided by an article presenting
observations of radio recombination lines from a quasar which show a redshift significantly reduced (by about 3%) to lines in the optical spectrum. If confirmed by further observation, this would obviously spell the end of the Big-Bang theory (although of course, as you argued in your article as well, this should - for many reasons - never have been accepted as a scientific theory in the first place).