4 ms·

Dark Matter and Dark Energy make up 95% of the Universe (the rest is all the normal matter and energy in all of the galaxies put together). Our understanding of

by db48x 4y ago

Dark Matter and Dark Energy make up 95% of the Universe (the rest is all the normal matter and energy in all of the galaxies put together). Our understanding of physics is both very complete, and contains large unknowns. You might imagine that there are a lot of aliens hiding in the Dark Matter, but as far as we can tell Dark Matter particles pass right through each other, as well as normal matter. They cannot clump together to make stars or planets or life forms the way normal matter can. Thus all aliens would be made of normal matter like us.

colordrops 4y ago
> Our understanding of physics is both very complete Citation please.
- db48x 4y ago
  I’m sure I could find some, but I haven’t bothered. We know that our current understanding of physics is incomplete (various niggling little problems with the Standard Model, the whole Dark Matter question etc), but these are surprisingly small problems. We only know about these problems because of the extreme sensitivity of our instruments. The new physics that will eventually fill these gaps will answer fascinating questions, but won’t change anything about our understanding of life. For example, petaquarks were first observed in the early 2000’s, and the Large Hadron Collider provided additional evidence for their existence. But they’re so unstable that they can never stick around long enough to participate in any life processes, so as far as our understanding of aliens goes they are irrelevant. Maybe they exist naturally inside the cores of neutron stars, but that’s not really a very habitable environment. Similarly, however we resolve the apparent paradoxes in our understanding of gravity and quantum mechanics won’t matter at all to the study of life. Gravity is so weak that it is essentially irrelevant in any sort of chemical system, even when quantum mechanics is necessary to understand the fine details.
  - colordrops 4y ago
    What I mean is, "complete" according to what criteria? It seems trivially obvious that our human model of physics could only be complete in the sense of accounting for all things we are capable of observing, but that isn't the same as being able to account for all things. There is nothing I am aware of in the model of physics that claims that it accounts for all aspects of reality, observable or not. We don't even know if there are multiple universes, and to what degree they interact, and if there are universes that mostly don't interact with ours at all. There is nothing in physics that precludes another universe that normally doesn't interact with ours, but advanced conscious beings within it being able to bridge that gap if they so choose, similar to how we could go to some island to visit an ant hill if we so choose.
    - db48x 4y ago
      On that last point you are incorrect. The known laws of physics rule out all forms of Einstein–Rosen bridge (aka “wormholes”) that you might imagine, except possibly inside of black holes (and those wouldn’t be traversable). That includes wormholes between points in our own universe, and between universes. Einstein and Rosen studied them because they are technically a valid solution to the equations of General Relativity, but not all solutions to those equations are realizable. In this case, opening a wormhole requires a considerable quantity of negative mass, and there is exactly zero negative mass available. Mass (or energy density), is simply never negative. As for completeness, each revision we make to the known laws of physics is always smaller than the ones that came before. Einstein’s Relativity trumped Newton’s laws of gravity and motion, but only at high speeds or energies. At high speeds you start to notice weird effects like time dilation, but at low speeds the time dilation is so small that you would never notice it unless you knew to look for it. Likewise, in most situations the difference between classical mechanics and quantum mechanics is unobservable. There were some edge cases where classical mechanics just couldn’t explain observable phenomena, like the photo–electric effect or phosphorescence, and all quantum mechanics does is fix those edge cases while still being able to explain all the rest of chemistry and such that we already knew about. The changes introduced by Quantum Electro–Dynamics and later Quantum Chromo–Dynamics were even subtler than that. The only easily–measured thing that QCD explains that QED couldn’t is radioactive decay, which is basically irrelevant to life. QED is much more useful to biologists because it explains how chemical reactions can release light (fireflies!), how chemicals can be sensitive to particular parts of the light spectrum (think rhodopsin in the cone cells in your eye), etc. Because every new addition to our understanding of physics must not contradict anything we already understand (if it did then we would know it was wrong), we are asymptotically approaching a limit (as it were). That limit is either the full laws of physics, or I suppose you would say some limitation of our own minds. But why should our minds be unable to comprehend the full laws of physics? Even if those get harder and harder to learn about and understand, we have all the time in the universe to come to grips with them. Any individual can maybe hit a limit of how clever they can be, but the human race as a whole? I doubt it; we’ll crack that nut eventually. Even if humanity gives up at some point, nothing that we fail to learn could contradict what we have already figured out.

by db48x 4y ago

colordrops 4y ago

> Our understanding of physics is both very complete Citation please.

db48x 4y ago
I’m sure I could find some, but I haven’t bothered. We know that our current understanding of physics is incomplete (various niggling little problems with the Standard Model, the whole Dark Matter question etc), but these are surprisingly small problems. We only know about these problems because of the extreme sensitivity of our instruments. The new physics that will eventually fill these gaps will answer fascinating questions, but won’t change anything about our understanding of life. For example, petaquarks were first observed in the early 2000’s, and the Large Hadron Collider provided additional evidence for their existence. But they’re so unstable that they can never stick around long enough to participate in any life processes, so as far as our understanding of aliens goes they are irrelevant. Maybe they exist naturally inside the cores of neutron stars, but that’s not really a very habitable environment. Similarly, however we resolve the apparent paradoxes in our understanding of gravity and quantum mechanics won’t matter at all to the study of life. Gravity is so weak that it is essentially irrelevant in any sort of chemical system, even when quantum mechanics is necessary to understand the fine details.
- colordrops 4y ago
  What I mean is, "complete" according to what criteria? It seems trivially obvious that our human model of physics could only be complete in the sense of accounting for all things we are capable of observing, but that isn't the same as being able to account for all things. There is nothing I am aware of in the model of physics that claims that it accounts for all aspects of reality, observable or not. We don't even know if there are multiple universes, and to what degree they interact, and if there are universes that mostly don't interact with ours at all. There is nothing in physics that precludes another universe that normally doesn't interact with ours, but advanced conscious beings within it being able to bridge that gap if they so choose, similar to how we could go to some island to visit an ant hill if we so choose.
  - db48x 4y ago
    On that last point you are incorrect. The known laws of physics rule out all forms of Einstein–Rosen bridge (aka “wormholes”) that you might imagine, except possibly inside of black holes (and those wouldn’t be traversable). That includes wormholes between points in our own universe, and between universes. Einstein and Rosen studied them because they are technically a valid solution to the equations of General Relativity, but not all solutions to those equations are realizable. In this case, opening a wormhole requires a considerable quantity of negative mass, and there is exactly zero negative mass available. Mass (or energy density), is simply never negative. As for completeness, each revision we make to the known laws of physics is always smaller than the ones that came before. Einstein’s Relativity trumped Newton’s laws of gravity and motion, but only at high speeds or energies. At high speeds you start to notice weird effects like time dilation, but at low speeds the time dilation is so small that you would never notice it unless you knew to look for it. Likewise, in most situations the difference between classical mechanics and quantum mechanics is unobservable. There were some edge cases where classical mechanics just couldn’t explain observable phenomena, like the photo–electric effect or phosphorescence, and all quantum mechanics does is fix those edge cases while still being able to explain all the rest of chemistry and such that we already knew about. The changes introduced by Quantum Electro–Dynamics and later Quantum Chromo–Dynamics were even subtler than that. The only easily–measured thing that QCD explains that QED couldn’t is radioactive decay, which is basically irrelevant to life. QED is much more useful to biologists because it explains how chemical reactions can release light (fireflies!), how chemicals can be sensitive to particular parts of the light spectrum (think rhodopsin in the cone cells in your eye), etc. Because every new addition to our understanding of physics must not contradict anything we already understand (if it did then we would know it was wrong), we are asymptotically approaching a limit (as it were). That limit is either the full laws of physics, or I suppose you would say some limitation of our own minds. But why should our minds be unable to comprehend the full laws of physics? Even if those get harder and harder to learn about and understand, we have all the time in the universe to come to grips with them. Any individual can maybe hit a limit of how clever they can be, but the human race as a whole? I doubt it; we’ll crack that nut eventually. Even if humanity gives up at some point, nothing that we fail to learn could contradict what we have already figured out.