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Cake day: July 3rd, 2023

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  • Then the arm could slide the magnet upwards to detach, reposition it, and repeat.

    This would work, but this is the point where you’d need to involve an external energy source. If you move the truck-magnet-arm system such that the whole system reaches a steady state and the truck has “moved” (relative to an outside observer), to continue any motion, you need to disturb the steady state to reposition the arm and create a new resting point. Doing so would require energy. From a battery, or an engine, or whatever, but you need energy from an external source. And so we’re right back to where we started: instead of all this jazz, why not just spend energy to spin the wheels instead?








  • A cache is not a stack, it’s memory stored in parallel cells. The CPU could theoretically, depending on the implementation, directly find the data it’s looking for by going to the address of the cell it remembers that it’s in.

    Not all L1 caches operate the same, but in almost all cases, it’s easy to actually go and get the data no matter where it physically is. If the data is at address 0 or at address 512, they both take the same time to fetch. The problem is if you don’t know where the data is, in which case you have to use heuristics to guess where it might be, or in the worst case check absolutely everywhere in the cache only to find it at the very last place… or the data isn’t there at all. In which case you’d check L2 cache, or RAM. The whole purpose of a cache is to randomly store data there that the CPU thinks it might need again in the future, so fast access is key. And in the most ideal case, it could theoretically be done in O(1).

    ETA: I don’t personally work with CPUs so I could be very wrong, but I have taken a few CPU architecture classes.




  • As a little nitpick, “extreme pressure” is partially true. We do need “extreme” pressure; not extremely high pressure, but extremely low pressure. We have these series of pumps that are able to remove more and more particles at each step. We have your standard pumps that get rid of most gases, then we have turbomolecular pumps that blow away a lot of the matter that remains, and then we have things like ion pumps, which electrocutes molecules in a vacuum and sucks them out using electric fields. This way, we’re able to create better vacuums here on Earth better than Space itself.

    And honestly, that’s pretty much wizardry to me.