I recently took part of a socially-oriented group-reading, using an excerpt from the Steve Hawking book “A Brief History of Time”. This was a book which I had not read before, but which for some reason, our group chose to in to, on Chapter 10, which I believe is a chapter, in which the author tries to explain, ‘What is the theory of everything, with emphasis on Gravity?’
I think that one aspect of this book which was not taken seriously enough, would have been precisely, to present it as one interpretation of Physics. I think that as much as Science and Physics is supposed to be objective, this extremely broad field is in fact subject to fashion trends.
And so there is one example from this Chapter 10, which I would like to use, to exemplify of Physics is ripe with fashion. Steven Hawking tries to explain, why and why not Gravity has been incorporated into the Unified Theory of Physics.
Steven Hawking points out, that there have been false dawns in the evolution of Science, but that we are making progress, including in our understanding of Gravity. But Gravity has always had as its main drawback, the fact that it lends itself the least, to interpretation according to Quantum Mechanics.
That problem began in the middle of the 20th century, when Physics was making a turn away from theories that can be called the Classical Theories, based on Fields – hence, the Albert Einstein ambition to produce a Unified Field Theory – in favor of the particle-based Universe, which now dominates the current definitions of the Universe, and which has arisen out of a relatively sudden desire to translate all Physics knowledge, into particle-based, QM knowledge equivalents.
Scientists have always been quick to point out, that the particle explanation of EM radiation is easy, in the existence of Photons. The explanation for the Strong Nuclear Force has been easy, either in the form of Quarks, or in the form of Gluons. But then Scientists were at an initial lack for gravity, in response to which it was simply stated ‘Gravity is mediated by a Graviton.’
Nobody ever explained what the behavior of a suspected Graviton was supposed to be, to result in what is observed as gravity. And the way Steven Hawking responds to this in his book, is to suggest that Scientists cheat a little bit, by adapting their theories to observed facts. In fact, If Science does not explain observed facts, it becomes useless.
Gravity acts on all the objects of the Universe, over great distances, without any certification from Humans, as being QM-conform. But when Physicists were asked in the 1970s, to explain how, and to make use of the construct of a Graviton, they actually started to build a concept of “Super Gravity”.
There is a reason, why I had not heard of Super Gravity, before the chapter-reading. As an individual, I could simply be satisfied that Gravity had not been adequately explained, in terms of actual Gravitons. But professional Scientists do not have this luxury, because they always need to find the answers, where questions are still unanswered.
And so in the 1970s, they started to build a concept of Super Gravity, according to which Gravity was no longer caused by a Graviton alone, but rather by a Group of Particles, that included Fermions and Bosons!
This concept eventually gave rise to a model which was so complex, that it would have needed to be tested on computers to see – whether it reflects known facts about how gravity behaves. And it was the failure of Super Gravity, to provide a simpler answer, which also gave rise to the success which followed it – the Revival of String Theory in the 1980s.
But the failure of Super Gravity was not actually, as far as I can tell, an actual failure with Super Gravity. This failure takes its roots in the simple fact, that because every phenomenon needed to be caused by a particle, Gravity needed to be caused by a particle, this particle was named, but nobody can explain how a Graviton is supposed to work, even to this day.
Well, Mathematicians have found that String Theory makes the most sense, if its equations are describing a Graviton. But they too, cannot provide a common-sense explanation, for how that proposition is supposed to work. They simply like String Theory, because they do.
And as far as I am concerned, the most up-to-date description of the subject remains, that in theory, Gravity should be mediated by Gravitons then, but that Scientists still do not really know how. This was also the state of affairs, before Super Gravity was attempted.
Also, Steven Hawking makes the statement that Quantum Mechanics is generally the Art, of balancing positive an negative infinities, such that the finite residuals will correspond to the observable. This is very similar to how he simply explains, that directly after the Big Bang, there just happened to be slightly more matter, than there was antimatter, and that this was the reason then, for why today, the Universe consists almost entirely of matter.
These statements might be brilliant conjecture, but do not count as facts. The only place where Physics balances infinities, is in the special field of Virtual Particles. And otherwise the subject does not crop up, as a general feature of QM. But it is a fixture, to the Steven Hawking interpretation, of how the Universe works. Which somehow needs to conform to a very Human notion of QM.