Confusing cosmology; what we do not know (Introduction)

by David Turell , Friday, March 26, 2021, 14:17 (1338 days ago) @ David Turell

There are huge gaps in our knowledge about the universe:

https://aeon.co/essays/we-are-at-a-crossroads-in-the-search-for-a-new-physics?utm_sourc...

"While physicists have been busily verifying ideas devised in the past century, we’ve made almost no progress in figuring out where to go in this one. In fact, we’re at a complete loss at how to explain some of the most fundamental but baffling observations of how our Universe behaves. There is a tremendous, even cosmic, chasm between the physics we know and love, and some of the phenomena that we observe, but simply can’t make head nor tail of. We have no idea how to bridge this chasm – yet we are proceeding, at pace, to construct ever more expensive experiments and observatories in the hope that we will.

***

"Dubbed the theory of inflation – because the Universe inflated uncontrollably during that period – it’s very elegant and mathematically simple, but also highly speculative. The reality is that we have no idea what actually happened at the beginning of the Universe; if it was inflation, what was driving it; how it came about; and how it ended.

"If what happened at the beginning of the Universe is a mystery, what’s happening now is no less puzzling. We’ve come to realise that most of the matter in the Universe, the stuff that gravitates around galaxies, for example, is dark. In other words, it doesn’t emit or reflect light like the particles from the Standard Model, or the atoms and molecules that we’re familiar with from the lab. This dark matter outnumbers ordinary matter by a factor of six to one, and underpins any explanation of why the Universe looks the way it does on the largest scales. We know almost nothing about what it actually is, apart from the fact that it coalesces under the pull of gravity. Whether it’s one type of particle or an amalgam of different types of particles, whether it could be something more complex and substantial, like a sea of black holes, or some kind of quantum field, the explanation is completely up for grabs. And that’s been the situation since the idea of dark matter first took off more than 50 years ago.

"Dark matter is only a small part of a much wider sea of dark stuff that permeates the Universe. Since the mid-1980s, we’ve had an inkling that the Universe isn’t expanding as we might expect. And, in recent years, we’ve found incontrovertible evidence that the Universe’s expansion is in fact speeding up – driven, it seems, by some form of energy that doesn’t clump under the pull of gravity like ‘ordinary’ energy. Rather, it’s repulsive, pushing space and time apart, and doesn’t emit or interact with light. One possibility is that the dark energy is simply a constant, undiluted by the expansion of the Universe. This cosmological constant was first invented by Einstein when he constructed his general theory of relativity, but was put aside for almost a century as superfluous (and, in his mind, pointless). While it’s favoured by many, it has such bizarre properties, that it jars with the rest of physics. And so, as with the dark matter, we really have no idea what this dark energy is.

"These three puzzles – how the Universe began, what dark matter is, and what dark energy consists of – make a compelling science case for future particle accelerators, observatories and satellite missions.

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"And so we come back to our seemingly unbridgeable, cosmic chasm – between tried and tested physics, and the exotic effects we see playing themselves out on cosmic scales. On the one hand, we have a set of laws of physics, a mathematical model that works perfectly well and that we’ve confirmed with exquisite prediction. Yet we’re at a loss about how to address the true nature of what dark matter, dark energy and inflation really are.

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"I’ve spent most of my adult life staring at the cosmic chasm – the abyss between what we know and what we don’t. And while our knowledge of the Universe has improved dramatically in that time, our ignorance has become only more focused. We’re no closer to answering the big questions about dark matter, dark energy and the origins of the Universe than when I started out. This isn’t for lack of trying, and a titanic effort is now underway to try and figure out all these mysterious aspects of the Universe. But there’s no guarantee we’ll succeed, and we might end up never really grasping how the Universe works. That’s why we need to be creative and to explore. As Einstein once said: ‘Let the people know that a new type of thinking is essential if mankind is to survive and move toward higher levels.’ While bridging the cosmic chasm might not be a matter of survival, undoubtedly it’s one of the most pressing challenges of modern science."

Comment: The 50+ year old string theory and wild ideas about a multiverse are ample evidence of the author's conundrum. All questions created by the human brain that has no natural reason for being here.