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Joined 7 months ago
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Cake day: December 9th, 2023

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  • The difference is that aether unraveled pretty quickly when we started seriously looking for it because experiments kept being outright inconsistent with what it was predicted we would see if it were there, whereas there are lots of independent lines of evidence that all point to the dark matter existing in the same page, so it really is not the same situation at all. The only problem with dark matter is that it doesn’t show up in our particle detectors (so far, at least), but there is no law of the universe that says that everything that exists has to.


  • It helps to realize that mass is just a bookkeeping label that we assign to the “internal” energy of a system, where the choice of what counts as being “internal” is somewhat arbitrary and depends on the level we are studying.

    For example, if you measure the mass of the nucleus of some atom, and then compare your measurement to the sums of the masses of the protons and neutrons inside of it, then you will see that the numbers do not agree. The reason for this is that much of the mass of a nucleus is actually the energy of the strong force bonds holding the nucleons together.

    But you can actually drop down another level. It turns out that the vast (~ 99%) majority of the mass in the proton in turn does not come from the quarks but from the energy of the gluon field holding them together.

    And if you drop down yet another level, the quarks get their mass through their interactions with the Highs field.

    So in short, it is energy all the way down.











  • Yes. My rule of thumb is that generally rebasing is the better approach, in part because if your commit history is relatively clean then it is easier to merge in changes one commit at a time than all at once. However, sometimes so much has changed that replaying your commits puts you in the position of having to solve so many problems that it is more trouble than it is worth, in which case you should feel no qualms about aborting the rebase (git rebase --abort) and using a merge instead.


  • The way I structure my commits, it is usually (but not always) easier and more reliable for me to replay my commits one at a time on top of the main branch and see how each relatively small change needs to be adapted in isolation–running the full test suite at each step to verify that my changes were correct–than to be presented with a slew of changes all at once that result from marrying all of my changes with all of the changes made to the main branch at once. So I generally start by attempting a rebase and fall back to a merge if that ends up creating more problems than it solves.





  • The root of the problem is that you think of momentum as being defined to be the product of something’s mass and its velocity, but this is actually only an approximation that just so happens to work extremely well at our everyday scales; the actual definition of momentum is the spatial frequency of the wave function (which is like a special kind of distribution). Thus, because photons can have a spatial frequency, it follows simply that they therefore can have momentum.

    Something else that likely contributes to your confusion is that you probably think that where something is and how fast it is going are two completely independent things, but again this is actually only an approximation; in actuality there is only one thing, the wave function, which is essentially overloaded to contain information both about position and momentum. Because you cannot pack two independent pieces of information into a single degree of freedom, it is not possible for position and momentum to be perfectly well defined at the same time, which is where the Heisenberg uncertainty principle comes from.