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Cake day: June 30th, 2023

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  • I may be wrong, but I suspect that any nearby black holes (i.e. within a few dozen light-years) with active accretion disks would already be visible to us in visible light and would also be bright enough in x-ray emissions that prior searches would have uncovered them.

    In my limited googling, the smallest active black hole I could find was A0620-00A, which is about 6 solar masses. Its accretion disk is visible in x-rays from 3000 light-years away, so I assume any small black holes accreting matter anywhere near us would also be visible.

    So more sensitive x-ray instruments would be useful for finding more distant SMBHs, but not necessary for finding any small, nearby black holes that we could actually stand a chance of reaching with a spacecraft. Most likely there just aren’t any active black holes in our neighborhood — only quiet ones we can’t see in x-rays.


  • That’s a pretty good idea, especially when you consider another problem that needs to be solved by any fast-moving spacecraft: dust.

    If a spacecraft hurtling through interstellar space at .3c encounters even a tiny grain of dust, the energy released by the collision is going to be enormous — more than enough to destroy the ship entirely. So far, the best strategy anyone has come up with to mitigate this risk is to just… send a shitload of probes all at once. Basically shotgun blast tiny craft at the sky in hopes that at least one of them makes it to the final destination unscathed.

    I imagine it wouldn’t be too hard to modify this strategy and stagger the launch times somewhat to create more of a ‘caravan’ of probes that could also double as a signal relay.



  • This has been my experience as well, only the company I work for has mandated that we must use AI tools everyday (regardless of whether we want/need them) and is actively tracking our usage to make sure we comply.

    My productivity has plummeted. The tool we use (Cursor) requires so much hand-holding that it’s like having a student dev with me at all times… only a real student would actually absorb information and learn over time, unlike this glorified Markov Chain. If I had a human junior dev, they could be a productive and semi-competent coder in 6 months. But 6 months from now, the LLM is still going to be making all of the same mistakes it is now.

    It’s gotten to the point where I ask the LLM to solve a problem for me just so that I can hit the required usage metrics, but completely ignore its output. And it makes me die a little bit inside every time I consider how much water/energy I’m wasting for literally zero benefit.


  • The proposal here is very similar to the Breakthrough Starshot initiative that wants to send a probe to Alpha Centauri, the nearest star system to our sun.

    Basically the idea is to take a very small (i.e. low mass) craft with a large solar sail and accelerate it to a significant fraction of the speed of light using very powerful ground-based microwave laser arrays. The neat thing about this concept is that all of the technology essentially exists already — it’s just a matter of scaling up existing concepts and miniaturizing existing sensors.

    The black hole rendezvous suggested in this paper is a lot more ambitious than Starshot, targeting a distance of 20-40 light-years (for comparison Alpha Centauri is only about 4 light-years away) and a max speed of 30% the speed of light (vs a speed of ~10% c targeted by Starshot). I think the main problem here (other than the requirement of building what essentially amounts to a microwave death ray) would be developing an antenna that’s both small enough to fit under the strict mass limits and powerful enough to broadcast the data 20+ light-years back to Earth. Maybe space-time lensing effects around the black hole itself could be used to amplify the signal? Another problem is that even at extreme speeds, this is a multi-decade mission — like 70+ years. Considering the travel delay involved in sending back a signal, it’ll be a century at least before any data would arrive at Earth. Unfortunately, century-long projects are an extremely hard sell for the people who hold the scientific purse strings.

    Oh, also… We don’t currently know of any BHs within the target range, and the paper’s author even admits that any targets more distant than 50ish light-years are basically unreachable. The current closest-known BH is more than 1000 light-years away, so we’ve still got a lot of work to do in finding a suitable target. Fortunately the field of black hole detection is advancing quickly, and the new Vera Rubin observatory is very likely to spot many previously-unknown black holes in the coming years. Hopefully some of those will be close!


  • maybe a wide field telescope and a software stack on the ground specifically built to catalog the “wobble” of stars and find invisible binary partners? It would double as an exoplanet detector, and IIRC there are already systems doing this.

    This has indeed already been done! In fact, the closest known black hole to earth was discovered by GAIA, a space telescope that collects this kind of data.

    We’ve also done what are called ‘microlensing surveys’ that look for the effect of spacetime distortion on background stars rather than the wobble of binary partners. Some of these have already found candidate objects over the years, however the new Vera Rubin observatory that’s just come online is expected to be really good at this sort of thing so we should spot many more over the next few years.

    Accretion disks seem to have peaks around 7KeV, so maybe a very specialized x-ray telescope?

    We’ve done this too! The Chandra space telescope has discovered hundreds of thousands of x-ray sources throughout the universe, including many, many black holes. Most of those are supermassive black holes at the centers of other galaxies, but hundreds of “local” objects have been found as well.











  • We’re not exactly sure, but we do know they’re not from impacts.

    They occur in a region of the planet called Tombaugh Regio, which has some of the youngest surface features on all of Pluto. The leading theory seems to be that the pits are caused by ice fracturing as the ‘crust’ of the planet is stressed by internal forces.

    We still don’t know for sure what’s heating Pluto’s interior, but one of the great discoveries from New Horizons is that Pluto is a very active world — possibly even as active as Earth’s surface. Warm(ish) water in the interior likely behaves similarly to how magma behaves on Earth, leading to activity analogous to plate tectonics and volcanism.