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Cake day: August 11th, 2023

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  • Ligo provides great science summaries for most publications, here is the one for this.

    By comparing the data to these models, we found that these black holes weighed approximately 137 and 103 times the mass of the Sun, respectively. Taking all uncertainties into account, their total mass was likely between 190 and 265 solar masses, dethroning GW190521 as the most massive black hole binary observed so far.
    […]
    The merger produced a black hole with a mass likely between 182 and 251 solar masses.

    So it seems 137 and 103 solar masses are the best estimates for each single black hole before merger. Due to uncertainty however, their total mass is in the range of 190-265 solar masses, of which 182-251 remain after merger. The rest of mass is emitted as gravitational waves.


  • What you describe is more like black start, providing power to the grind when it is down. This has to be controlled well, and only a few plants need to be capable of it.

    Grid following means something like whatever the grid does, the inverter injects power supporting it. A grid forming generator or inverter also follows the grid somewhat, but tries to get it to an optimal condition. This entails things like voltage control by reactive power, frequency control by operating reserve, fault ride trough capability and so on. Many of those are naturally provided by large conventional power plants using synchronous generators like gas, nuclear or hydro. For inverter based systems, they have to be considered explicitly. For battery storage most are relatively easy to implement, some also in solar inverters. The tech exists, but yes, in some countries the regulations have not kept up with rapid expanse of inverter based power generation in the last years.


  • Out of interest I did some estimates and it seems that an asymmetry of three billionth of the total thermal radiation would be enough to rotate the probe once over a timescale of 10 years. So if the radioisotope generator has even just a tiny bit of a different infrared brightness on one side, it would turn voyager in a few years.

    notes on calculation

    Voyager weight: 815 kg
    Approximate Diameter: 1 m
    Assume mass and thermal radiation emitted with a center distance of this diameter. Then we can calculate as it would need to move 2π 2 m. It should be enough as coarse estimate and underestimate the acceleration. Distance to move: d = 6.3 m

    Assume constant acceleration due to thermal radiation
    RTG power at start: 3 * 2.4 kW = 7.2kW
    RTG power now: 7.2kW * 10^(48/88) = 4.9 kW
    Total of thermal radiation: 4.9kW / c = 16 uN
    distance moved: d = a t^2 / 2
    assuming 10 years accelerated movement movement:
    a = 63 mm/yr^2
    F = 52 fN
    3 * 10^-9 of thermal force



  • The thing is, now we have one 1-2 3.7 meter sized antenna on the voyager probes and a 100 meter sized antenna on earth with high transmission power. Signal decays with distance squared. To get the same signal power to the voyager probe assuming an relay in the middle, it would need an 25 meter antenna with the large transmitter/receiver currently on earth on space.

    In short it’s easier to build a 4 times better transmission system on earth than in an relay in space.

    One point where relays are used are mars rovers. There the orbiter has an large antenna and is close to the rover, so you don’t need to land the large antenna at the surface.

    Edit: fixed antenna diameter




  • Yes colors have a meaning. However, they change ober time and culture. So why not use the word which describes exactly what we mean?

    I agree, nowadays blacklist/whitelist has practically nothing to do with skin color. However i do think it is weird to use the same words for describing the appearance of people and good/bad.

    Well i would be indifferent to the renaming to primary, because it doesn’t really matter to me what they call their branches, as long as it is descriptive. primary also conveys the meaning. I would probably continue using main/dev because i see no reason to change.
    I am not someone who says “You should change this!”. I just say, think of it, there are some reasons to change and the only reason to keep it, os that we did it always like this. I think there are reasons for selecting better words. And I am only annoyed by people who are outraged by things others do, which does not really affects them negatively. I get it that someone wants to continue using blacklist, master, etc. and I am ok with that.


  • Even ignoring the question of racism, they are still stupid names.

    Imagine teaching a child about this and it asks: Why is white allowed and black not? The only answer is, because it is like this for a long time. If we name them allowlist and denylist, it is obvious to all English speaking people. Shouldn’t we strive for descriptive names in programming?

    However, if you use names whitelist an blacklist, you need to make the implicit connection white-positive black-negative. Yes obviously this does not make you racist if you do this in programming. But is it good?