For any physicists reading, I have a question about the Big Bang: Is the standard consensus that the specific physical description is literal or just the closest approximation/visual model we have that matches the data?
I ask because I was in my 30s before I learned that Dark Matter and Dark Energy are effectively metaphors. There is something that contributes more gravity in the universe than our understanding of the it predicts. And there is something that contributes energy to accelerating the expansion of the universe, and we have no idea what. So we call them "matter" and "energy" but TECHNICALLY they don't have to be right? It could also be that something exists that is completely beyond our bounds of understanding.
I ask because this feels very much the situation with the Big Bang. Even if all the data shows the universe rapidly expanding in fractions of a second, it is incomprehensible to understand where the energy for it came from, or what happened "before". And the answer "nothing happened before because that's when time started" feels like an acknowledgement of the limitations of our human understanding.
So here's my follow-up question: Obviously we build an understanding of the universe based on observations of the data. And sometimes the data doesn't match and we have to upgrade Newtonian Physics to Einsteinian, or introduce Quantum Mechanics, etc. So are there comparable/equivalent investigations/experiments going on today that reveal numbers/observations that are basically fundamentally unexplainable without looking beyond the realms of our understanding of the limitations of our universe?
> "nothing happened before because that's when time started" feels like an acknowledgement of the limitations of our human understanding.
"Nothing happened" is not the correct answer. The correct answer is that we don't know what happened because before you get to the big bang, our current theories of physics stop working. If you run the equations of general relativity backwards from current conditions you get to a singularity and at that point you can't go back any further. That singularity is called the "big bang". But we know that this is (almost certainly) not an accurate model of what actually happened because we know that GR is (almost certainly) just an approximation of some as-yet-undiscovered theory of quantum gravity, just as Newtonian mechanics is an approximation of GR (in the case of weak gravitational fields).
> So here's my follow-up question: Obviously we build an understanding of the universe based on observations of the data. And sometimes the data doesn't match and we have to upgrade Newtonian Physics to Einsteinian, or introduce Quantum Mechanics, etc. So are there comparable/equivalent investigations/experiments going on today that reveal numbers/observations that are basically fundamentally unexplainable without looking beyond the realms of our understanding of the limitations of our universe?
They're trying. The big problem is that all of the low-lying experimental and theoretical fruit has been picked, and doing experiments that will actually advance fundamental physics (i.e. whose outcomes cannot be predicted accurately by GR and QFT) is fantastically difficult. The math turns out to be really hairy too. No one has been able to figure out out to quantize gravity so that GR and QFT can be combined into a single theory, let alone propose an experiment that could test such a theory. It's a major problem, almost at the level of a crisis. Fundamental physics essentially has made no progress since the standard model was finished 50 years ago.
The idea that the universe rapidly expanded in a fraction of a second right at the beginning is called inflation theory, it's a supplemental modification of the big bang theory and not all physicists that accept the big bang theory also accept inflation theory. There are also some theories that try to explain what there might have been 'before' the big bang, conformal cyclic cosmology for example. Then there's zero energy universe hypothesis, which suggests the universe may have arisen from a random quantum fluctuation - though a fluctuation of what is unclear.
So there are quite a few alternative variations on big bang theories. The observation that the universe is expanding seems solid, and the detection of the cosmic microwave background means something must have happened long ago that blasted out all that energy, seemingly everywhere at once. When you go beyond those though things start to get less certain.
I've proposed a modified gravity theory that you might be interested in taking a look at. If correct, it would answer a lot of these questions. You may look at a pdf of it here:
Not metaphors . We know these are out there — we just don’t know a lot about them. The situation is similar to atoms in second half of 19th century : we knew they are there , we knew some of their properties but only it the first quarter of 20th century we learned how much more there is to learn about atoms
Metaphor probably isn't the right word, but it's not really wrong either. "Placeholder" is also sorta correct but not entirely. Dark matter is a placeholder for an as-yet-unknown thing that interacts with gravity, in the most popular theories. There are less-popular ideas--still given serious study and consideration--like MOND that may some day explain the effects currently labeled as "dark matter". I don't think it's accurate to say "we know these are out there", and if it turns out that MOND or some other alternative explains observations, "dark matter" will turn out to have been fairly metaphorical (or just plain wrong).
We say "dark matter" rather than "weird gravity behavior" because the evidence thus far doesn't just look like gravity being weird. It looks like stuff, actual honest to God stuff, floating around. If MOND is right dark matter does not exist and never did. Dark matter is the name of the actual matter we believe is out there; we could be wrong, but it's not just a generic placeholder.
Atoms is a good example. Are atoms really out there in the way that most people would imagine? ("Electrons orbiting a nucleus of protons and nucleus") Or are they all actually fields of statistical probability or some other concept that is basically impossible to imagine in a physical world but matches our equations?
They're "actually" what QFT says they are, but the rest isn't wrong either. It's not wrong to say "a house exists" because it's actually a pile of bricks in the shape of a house.
Dark matter must be "matter" if it exists, because there's not a category of things that aren't matter.
> Dark matter must be "matter" if it exists, because there's not a category of things that aren't matter
I mean, ehhh? Like, yes, absolutely, no matter how weird dark matter turns out to be it's the obligation of our definition of matter to adapt to it, but it's also not the same kind of category error as saying atoms don't exist. Depending on how weird gravity's integration into QFT is, dark matter could be arbitrarily divorced from what we expect matter to behave like. If, horror of horrors, there is no such integration, I'd say it's fair to call dark matter something truly other.
Sure, I guess what I mean is it'd still end up in on the table of subatomic particles whether or not it's a new one.
Maybe if it's something like another universe of stuff that only interacts with ours through gravity then we'd just be unable to find out which kind of stuff it is? But I don't know how we'd even get to that point.
I ask because I was in my 30s before I learned that Dark Matter and Dark Energy are effectively metaphors. There is something that contributes more gravity in the universe than our understanding of the it predicts. And there is something that contributes energy to accelerating the expansion of the universe, and we have no idea what. So we call them "matter" and "energy" but TECHNICALLY they don't have to be right? It could also be that something exists that is completely beyond our bounds of understanding.
I ask because this feels very much the situation with the Big Bang. Even if all the data shows the universe rapidly expanding in fractions of a second, it is incomprehensible to understand where the energy for it came from, or what happened "before". And the answer "nothing happened before because that's when time started" feels like an acknowledgement of the limitations of our human understanding.
So here's my follow-up question: Obviously we build an understanding of the universe based on observations of the data. And sometimes the data doesn't match and we have to upgrade Newtonian Physics to Einsteinian, or introduce Quantum Mechanics, etc. So are there comparable/equivalent investigations/experiments going on today that reveal numbers/observations that are basically fundamentally unexplainable without looking beyond the realms of our understanding of the limitations of our universe?