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> It is tempting to regard fundamental physics as a study of "Why are we here?", but it is really a study of "How are we here?" The difference is subtle but sub

> It is tempting to regard fundamental physics as a study of "Why are we here?", but it is really a study of "How are we here?" The difference is subtle but substantial. If "Why?" is what you're seeking, you are more likely to find that answer within, rather than within the study of physics. I don't want to know why, I just want to know the complete set of rules at the lowest level.

ISL 6y ago
It is unlikely that we will ever grasp the complete set of rules at the lowest level. I don't say this to be defeatist, but rather as a statement of pragmatism. To do so would be to have a convincing grasp of Planck-scale physics -- a detailed understanding of physics at and above energy-densities reached in the Big Bang. Some precision experiments and astrophysical measurements do constrain certain Planck-scale models, but a true test of whether or not we understand early-universe physics is likely to necessitate creating a few Big Bangs ourselves. Doing so, with known technology, seems impossible. If it were possible, doing so would seem fraught with actual risk. (N.B. for the non-expert reader: there are cosmic rays that strike the Sun at least once every five minutes (and Earth, at least once a month) with energies 10,000,000 times greater than anything humans have ever achieved. Those collisions, over the last 4,500,000,000 years, have not yet resulted in the disruption of spacetime or the formation of a black hole. You are very, very, very safe from physicists breaking the universe as you know it. :).) Edit to add: You, mseepgood, aren't alone in your desire for knowledge. One Stephen Hawking once stated, “My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all.”
- refulgentis 6y ago
  dumb q I was never smart enough to ask when I was doing a physics degree: how do we know the big bang required enormous energy and thus is impossible? in the few peeks we got at grad school physics, I walked with away with the likely erroneous impression that the best guess was the big bang happened due to "quantum fluctuations in a vacuum" which sounded suspiciously close to "at random" - and I won't lie, since, I've just assumed that at any point there could be another big bang and we'd be blown away!
  - ISL 6y ago
    I think the safest answer regarding the Big Bang is that we don't really understand the mechanism. In particular, anything regarding inflation stands on truly dubious ground (It gets the necessary outcomes right, but we have no presently-testable theory regarding the mechanism. Any mechanism that does must defy the laws of physics as we know them). I can't pretend to be an expert here, but the quantum-fluctuations in a vacuum that we all experience at all times do, over longer times ("long" here is generally unfathomably short), need to satisfy energy-conservation. To do otherwise requires paying an overwhelming probabilistic cost (a much bigger nigh-infinity than your garden-variety nigh-infinity). If you're worried about unexpected instantaneous death from the universe, I would argue that one should be far more concerned with, say, a gamma-ray burst nearby from within the galaxy (or, far more likely yet, a nuclear war) than being overrun by a Big-Bang-like event. For that same reason (energy conservation), perhaps the central question one might ask of the Big Bang theory is, "How did it come to pass that all of that energy wound up in such a tiny volume?" There are plenty of theories out there, the best of which attempt to confront inflation at the same time, but I am unaware of a clear leader. I don't mean to entirely disregard the importance of quantum fluctuations in cosmology. Indeed, the large-scale structure of the cosmic-microwave background is very consistent with pure quantum fluctuation, as if the fluctuations of a tiny volume of space had been magnified to cosmic scale. It is simply this experimentalist's opinion that there is probably substantially more to the story than the universe having won the lottery of all lotteries in order to exist at all.
    - spekcular 6y ago
      What do you feeling is wrong with "the universe having won the lottery of all lotteries in order to exist at all"? Our existence seems consistent with some multiverse picture where we just end up observing one out of many universes that was capable of supporting life. After all, if any of a number of fundamental constants gets tweaked by a small amount, then we end up in situations like e.g. hydrogen being the only naturally occurring element. (I'm purposely being a bit provocative here because I haven't heard an explanation for fine-tuning that doesn't rely on multiverses or divine intervention.)

ISL 6y ago

It is unlikely that we will ever grasp the complete set of rules at the lowest level. I don't say this to be defeatist, but rather as a statement of pragmatism. To do so would be to have a convincing grasp of Planck-scale physics -- a detailed understanding of physics at and above energy-densities reached in the Big Bang. Some precision experiments and astrophysical measurements do constrain certain Planck-scale models, but a true test of whether or not we understand early-universe physics is likely to necessitate creating a few Big Bangs ourselves. Doing so, with known technology, seems impossible. If it were possible, doing so would seem fraught with actual risk. (N.B. for the non-expert reader: there are cosmic rays that strike the Sun at least once every five minutes (and Earth, at least once a month) with energies 10,000,000 times greater than anything humans have ever achieved. Those collisions, over the last 4,500,000,000 years, have not yet resulted in the disruption of spacetime or the formation of a black hole. You are very, very, very safe from physicists breaking the universe as you know it. :).) Edit to add: You, mseepgood, aren't alone in your desire for knowledge. One Stephen Hawking once stated, “My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all.”

refulgentis 6y ago
dumb q I was never smart enough to ask when I was doing a physics degree: how do we know the big bang required enormous energy and thus is impossible? in the few peeks we got at grad school physics, I walked with away with the likely erroneous impression that the best guess was the big bang happened due to "quantum fluctuations in a vacuum" which sounded suspiciously close to "at random" - and I won't lie, since, I've just assumed that at any point there could be another big bang and we'd be blown away!
- ISL 6y ago
  I think the safest answer regarding the Big Bang is that we don't really understand the mechanism. In particular, anything regarding inflation stands on truly dubious ground (It gets the necessary outcomes right, but we have no presently-testable theory regarding the mechanism. Any mechanism that does must defy the laws of physics as we know them). I can't pretend to be an expert here, but the quantum-fluctuations in a vacuum that we all experience at all times do, over longer times ("long" here is generally unfathomably short), need to satisfy energy-conservation. To do otherwise requires paying an overwhelming probabilistic cost (a much bigger nigh-infinity than your garden-variety nigh-infinity). If you're worried about unexpected instantaneous death from the universe, I would argue that one should be far more concerned with, say, a gamma-ray burst nearby from within the galaxy (or, far more likely yet, a nuclear war) than being overrun by a Big-Bang-like event. For that same reason (energy conservation), perhaps the central question one might ask of the Big Bang theory is, "How did it come to pass that all of that energy wound up in such a tiny volume?" There are plenty of theories out there, the best of which attempt to confront inflation at the same time, but I am unaware of a clear leader. I don't mean to entirely disregard the importance of quantum fluctuations in cosmology. Indeed, the large-scale structure of the cosmic-microwave background is very consistent with pure quantum fluctuation, as if the fluctuations of a tiny volume of space had been magnified to cosmic scale. It is simply this experimentalist's opinion that there is probably substantially more to the story than the universe having won the lottery of all lotteries in order to exist at all.
  - spekcular 6y ago
    What do you feeling is wrong with "the universe having won the lottery of all lotteries in order to exist at all"? Our existence seems consistent with some multiverse picture where we just end up observing one out of many universes that was capable of supporting life. After all, if any of a number of fundamental constants gets tweaked by a small amount, then we end up in situations like e.g. hydrogen being the only naturally occurring element. (I'm purposely being a bit provocative here because I haven't heard an explanation for fine-tuning that doesn't rely on multiverses or divine intervention.)