Why Gravity as we know it is the only explanation for Cosmic Acceleration
This World, in This Universe
Did you see that film Yesterday about a man who wakes up in a world where (almost) everyone has forgotten the Beatles and their songs, and they did not become a part of the culture?
Lately, and increasingly, I have a feeling I am in a world like that, i.e. a world where, to me, it seems there’s a gaping missing piece of knowledge that everyone should be aware of, that should be a part of our culture, and yet only I see it. Perhaps it’s not a unique problem, this quasi-solipsistic feeling, and we all have some version of it.
In my case, the ‘Why can’t anyone see the big elephant in the room?’ concerns cosmology, and in particular, the accelerating expansion of the cosmos.
In the world of scientists, astrophysicists and cosmologists, this phenomenon, that was first gathered in 1998 (from observations of supernovae by Perlmutter, Riess and Schmidt), is a big mystery. Nobody expected or predicted it, and even now nobody has an explanation for it. Even the most well-known theory, that the acceleration is caused by ‘dark energy’ or the vacuum energy of space (that theoretically exists according to quantum physics), comes nowhere near explaining it. Indeed this theory is famously 120 orders of magnitude off target. And so it seems, every month new theories come and go, contrived, complex, obscure or requiring the much sought after ‘new physics’ or complex inaccessible maths.
But for me I see a simple answer; one that all scientists and rational people should be aware of. With this answer I actually predicted the cosmic acceleration in 1994, years before it was observed.
How so?
Well firstly, it should not have surprised anyone that the cosmos might be accelerating apart, rather than its expansion slowing down as was generally assumed. (At that time scientists like Hawking and co were wondering whether the expansion might be slowed down enough (by gravity) for it to stop and then contract/ collapse again, or whether the expansion would just keep slowing down but never stop).
The acceleration should not have been a surprise because the assumption that the expansion had been slowing down led to a certain puzzle; that the (then) calculated age of the universe, from the rate of expansion, was too young, at about 10 billion years, to account for the apparent age of many of its galaxies.
I saw the simple answer (in 1994), that the cosmos /visible universe could be accelerating apart, meaning it took a lot longer to reach its present rate of expansion – and so had an age that could accommodate the apparent state of evolution of the galaxies. So when the cosmic acceleration was observed in 1998 it agreed with that part of my theory at least.
But in reasoning the cosmos should be accelerating apart, the next question is why? Again, to me, there was a simple answer, according to the laws of physics – GRAVITY.
Ok so now you’re saying gravity is supposed to pull things together, not accelerate them apart, and of course that is the reason no scientist, not even the likes of Roger Penrose or Stephen Hawking could speculate that the cosmos was accelerating apart, because gravity must be slowing the expansion down.
Well, you don’t need to refer to General relativity to know that gravity does not always pull things together. If you have two masses, A and B, that are a distance apart, then the gravity between them would pull them together (unless in an orbital relationship) but if you introduce a third (greater) mass, C, into the scenario then whichever of A and B is nearest C would accelerate faster towards C , and so C’s gravity can cause A and B to move/accelerate apart.
That is perhaps the simplest way of explaining why everything in our visible universe would be, on the very grand scale, slowly accelerating apart; because there is another unseen mass beyond the mass of our universe; the mass of a greater infinite eternal universe containing infinite other sub-universe, cosmoses, big bangs. And the gravitational relationship with that causes our local cosmic acceleration (though it’s a tad more complicated than the ABC example I gave).
But, if we have such a greater universe outside ours, ever existent (with bangs coming and going) then why would we not see the bright collective light from all those sources? We are not afforded the current answer given for the darkness of the night sky (Olbers paradox) - that the universe is not old enough for light from beyond a certain expanding range to reach us - but we do have GRAVITY (again). The gravity of the infinite surrounding collective mass, beyond a certain distance, would also stop its light from reaching us.
Gravity stopping light (the reason for black holes) is known as gravitational redshift. This background gravitational red/blackshift also solves another puzzle that has emerged in cosmology; a discrepancy in the calculated Hubble rate of expansion and the age of the universe…
If, between here and the dark infinity, there is a progressive redshift caused by that infinite mass, then a component of all the redshifting we observe is due to that dark background. That means that the Hubble constant becomes an overestimate of the redshift caused by a Doppler effect (receding motion) – so the visible universe is expanding slower and must be older than previously calculated. It also means the cosmic microwave background radiation is not as red-shifted by time and cooling as we think, meaning it is younger than deduced. So the age of the universe, as deduced the CMBR , can converge on that deduced from astronomical observations to explain the puzzle of the 9% discrepancy between their calculations.
Her then is a theory, the only theory that actually predicted the cosmic acceleration, the only theory that can explain it, the only theory that also explains the Hubble constant problem (and other observations that mystify cosmologists), so how come it is not out there, widely known about and referred to? Is it because somehow the collective human mind is not yet ready to accept the ultimate theory of the universe; that it is infinite eternal and our own ‘big bang’ is just another little firework in the infinity, surrounded by endless others (and endless variety).
What about other theories? Are there so many out there that they swamp out the best theory? By the principle of Occam’s razor it is this simple theory, based on known physics and no more, that should stand out among the more contrived complex speculative new physics theories. It is surely also the most sober/ sane/ realistic theory, for what else gently moves huge masses on vast scales? - only Gravity.
Maybe a confusion when cosmologists talk of an accelerating expansion of space as being in itself the cause. They are saying nothing more than what is observed is the cause of what is observed. There is a semantic problem with calling it an expansion of space when in truth we are only seeing things moving apart. If the context of space were expanding then everything should expand with it, including the sizes of fundamental particles, but we are only observing an expansion of the space between things, which is no more that things moving apart. Still, if you want to see this as the expansion of space, it nevertheless requires an explanation for what could cause that. And again there is only one reasonable culprit; Gravity. It is Gravity, in general relativity, that distorts, warps, and here stretches, space - though I still prefer to say it is gravity here is moving things apart rather than stretching space..
Similarly we might say we know that gravity bends paths of light (as we see in gravitational lensing) but then Einstein might prefer to say light always travels in straight lines (not strictly true if you consider quantum physics) and so the apparent bending of light paths is showing the warping of space. The effect is the same though.
Setting this confusion aside, there is one consideration that really should settle the matter, and make it clear that Gravity is the only explanation that agrees with the laws of physics, to discard all the other theories. Because, if you don’t think gravity is the cause of the accelerating expansion, what else can you be thinking of?
It’s got to be some force/ agent/cause that is overcoming gravity in pushing everything apart. As such it is an agent that is doing work, continually adding energy to the cosmos, meaning that it is breaking the conservation of energy principle. To put it another way, it is understood that whenever you are working against gravity and ’lifting things up’ then you are adding to their gravitational potential energy. Similarly as everything in the cosmos is being pushed apart then it is ever adding to the gravitational potential energy. But if this moving of things apart is also accelerating them then it is also adding to the kinetic energy of everything, meaning an overall total disrespect for the laws of the universe. Only if the accelerating expansion is motion according to gravity ( i.e. a falling towards the mass of the infinity, wherein the gravitational potential energy is decreasing as the kinetic energy increases) does one have a scenario that agrees with the laws of physics.
So now, since this is the only theory that agrees with the laws of physics, predicted and explains the accelerating expansion, the Hubble rate problem (and a lot of other necessary things that I have not gone into here) I return again to that film Yesterday and wonder why no one else saw it or sees it now.
Indeed, just like that film, where the man was not the only one who remembered the Beatles, I am not the only one who can get this theory. Everyone I have explained it to can understand it and I have heard others suggest it, but in the world of cosmology it is weirdly never mentioned, even as a candidate (despite my efforts). I conclude that the world of human affairs here on Earth is stranger and more mysterious than the unfathomable universe.
MJ Bridger (@MarktheStars), Artist, Oxford, 28th October 2019
