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John Michell: Country Parson Described Black Holes in 1783 (2000)
- 29athrowaway 3y agoOnce you know speed of light is the maximum possible speed, you can try to guess what happens when you have enough mass to make escape velocity higher than the speed of light (it is not possible, therefore you can't escape).
- jfengel 3y agoThis doesn't assume that light is the maximum possible speed. But it does show that you couldn't use light to see such an object. Relativity makes black holes much more "final" than this original concept, but he was definitely thinking in the right direction.
- tzs 3y agoI've never liked the "escape velocity >= c" explanation of why you can't get out a black hole. The escape velocity for a body at a given point is the velocity needed to escape from that point ballistically. If you don't limit yourself to entirely ballistic trajectories you can escape without ever reaching that point's escape velocity. To explain why nothing, not even things on non-ballistic trajectories, cannot get out of black holes you've got to turn to weird headache inducing general relativity stuff.
- at_a_remove 3y agoYou are correct. It's a fortunate coincidence and nothing more. It's much easier to think of the gradual warping of spacetime around a black hole so that more and more directions are down. East? No, that's really east and down. Left? Nope, you thought you were going left but it is left and down. Less and less "up" is available to you until you are on a knife edge where you can make an orbit (assuming a non-rotating black hole, no angular momentum) around the event horizon with a photon. Beyond that, everything is some flavor of down.
- 29athrowaway 3y agoIn 1700s?
- tzs 3y agoYup. Those in the 1700s who wrote about stars with so much mass that light cannot escape would have known that their calculations only applied to ballistic trajectories. They would have believed that non-ballistic objects such as rockets would be able to escape because all they had was Newtonian physics. That when mass becomes high enough that light can't escape nothing else can escape either doesn't pop out of the math until you have general relativity.
- martyvis 3y agoThat's right. The Earth's escape velocity is just over 11km/s or 4000km/h. If you have a rocket that only has enough force to propel you at say 100km/h away from the earth you can go anywhere you want in the universe - provided you keep applying that force through thrust. If you stop the rocket you will be subject to gravitational force to bring you back (or until the gravitational pull from other bodies of becomes dominant)
- thfuran 3y ago>If you have a rocket that only has enough force to propel you at say 100km/h away from the earth you can go anywhere you want in the universe Unless the rocket collapses into a black hole under the sheer mass of all that fuel.
- albumen 3y agoNitpick: 11km/s escape velocity for earth is ~40,000km/h (not 4,000)
- marcosdumay 3y agoWell, if you go with Newton's explanation for light, it's quite obvious that it can only follow ballistic trajectories. One would certainly not expect elementary particles to function like rockets. But yeah, nobody could come with a description of a black hole anything like the modern one before 1900. Anything older is certain to be very different.
- jahnu 3y agoWe don’t need to assume a small rocket strapped to a particle ;) Imagine accelerating an electron in some sort of magnetic field, in series. In a Newtonian system any speed is achievable. GR forbids this though.
- naasking 3y ago> GR forbids this though. Does it though? https://youtu.be/9-jIplX6Wjw?si=xbNYKT9YN13VyJrV https://youtu.be/9-jIplX6Wjw?si=xbNYKT9YN13VyJrV
- pdonis 3y ago> enough mass It's not a question of enough mass. It's a question of being compact enough. There is no minimum mass for a black hole, but the smaller the mass, the smaller the surface area of the horizon (the 2-sphere that the mass has to collapse inside to form the hole).
- wyldfire 3y agoBut wouldn't you have to conclude / assume that light is affected by gravity? Was that well-known at that time?
- deleted 3y ago[deleted]
- tsimionescu 3y agoNewton introduced the corpuscular theory of light, in modern terms saying that light is made of tiny particles. Once you have that, it becomes natural to think that light is probably attracted by gravity just like everything else is. The wave theory of light came quite a bit later, in Maxwell's time.
- archgoon 3y ago> Once you know speed of light is the maximum possible speed But he didn't postulate this at all. He simply postulated (as per Newton) that light is made of particles with mass, which could thus be affected by gravity. Since they are moving at a finite speed, the light particles would be slowed down by gravity, and eventually completely stopped. He further proposed, based on this model, that the mass of an object could potentially be determined by determining how much slower the particles were moving. This doesn't work. Light doesn't really get slowed down by gravity, and you definitely don't have any slow light that was created from stars trillions of miles away. It's a cool idea, but doesn't work with how light actually propagates.
- RcouF1uZ4gsC 3y agoThis is one of those ideas that is so wrong that it is right: > He reasoned that such particles, emerging from the surface of a star, would have their speed reduced by the star’s gravitational pull, just like projectiles fired upward from the Earth. By measuring the reduction in the speed of the light from a given star, he thought it might be possible to calculate the star’s mass. >Michell asked himself how large this effect could be. He knew that any projectile must move faster than a certain critical speed to escape from a star’s gravitational embrace. This “escape velocity“ depends only on the size and mass of the star. What would happen if a star’s gravity were so strong that its escape velocity exceeded the speed of light? Michell realized that the light would have to fall back to the surface.
- synapsomorphy 3y agoI wouldn't say that. Yes, it's not exactly our modern understanding, but the core idea is the exact same: stars can get big enough that even light, which is super fast, can't escape them, and that was an entirely novel idea in his time.
- bmitc 3y agoI think it's more that the effective idea is the same, while the core idea is what is so vastly different. He was arguing as if light was affected by gravity. This is totally missing the rather revolutionary idea of general relativity, best explained by John Wheeler: "Spacetime tells matter how to move; matter tells spacetime how to curve".
- spindle 3y agoCan you say more about what's wrong about it? It seems plain right to me, in Newtonian physics, assuming only that light has a speed (which was not at all a crazy thing to think at that point), and historians of cosmology usually agree (source personal communication, so I could be wrong).
- mr_toad 3y agoBlack holes don’t alter the speed of light, they cause it to follow trajectories that don’t leave the event horizon.
- bloopernova 3y agoSome lesser known (and some well known) scientists of the industrial age are profiled by the wonderful TV show "Local Heroes": https://en.m.wikipedia.org/wiki/Local_Heroes_(British_TV_series) https://en.m.wikipedia.org/wiki/Local_Heroes_(British_TV_ser... Great show if you can find it. Another show, Connections, is much more popular, and traces the family tree of various inventions. Again, highly recommended!
- NaOH 3y agoSomeone here recently linked Connections episodes available on the Internet Archive and it's been great to watch episodes. https://archive.org/details/bbc-connections-1978 https://archive.org/details/bbc-connections-1978
- petepete 3y agoWe all watched local heroes at my house, Adam Hart Davies did such a good job of making the topics approachable, even for kids. Hard to believe it's a quarter of a century since it finished.
- noneeeed 3y agoLikewise. Adam should be a national treasure. I miss all those relatively unflashy science programmes. They all have to be a bit over the top and made into rather showy but shallow “event” TV, probably featuring Brian Cox on a mountain or in a desert for some reason.
- shusaku 3y ago> Michell was also the first to apply the new mathematics of statistics to astronomy. By studying how the stars are distributed on the sky, he showed that many more stars appear as pairs or groups than could be accounted for by random alignments. He argued that these were real systems of double or multiple stars bound together by their mutual gravity. This was the first evidence for the existence of physical associations of stars. What is our modern understanding of this? Are there kinds of local clusters you could detect with the naked eye?
- mathren 3y agoA very recent review from reputable young researchers in this specific subfield: https://arxiv.org/abs/2311.01865 https://arxiv.org/abs/2311.01865 For naked eye clusters look up pleiadis in the northern emisphere and LMC/SMC in the south, and then you can use stellarium (see other HN post)
- dudeinjapan 3y agoNo portrait of Michell exists, but he was described as “a little short man, of black complexion, and fat.” I think the most likely explanation is that John Michell was a space alien, looking to peddle common knowledge in his galaxy for Earth fame.
- fnordpiglet 3y agoOr a short fat black man that was extremely smart, I guess.
- dudeinjapan 3y agoOccam's razor: who is more likely to know about black holes, an 18th century English bumpkin, or a spacefaring visitor from another galaxy?
- InCityDreams 3y agoAs a 'bumpkin', by definition, would be considered a 'stupid person', my money, then, is on the traveller.
- dudeinjapan 3y agoThe counter-argument is that the aliens might be bumpkins too. Why do they keep abducting yokels driving down backwater dirt roads??
- denton-scratch 3y agoInteresting and original scifi plotline: humans encounter hayseed, never-been-to-the-city aliens. Perhaps they 'jacked their spaceship; or maybe they're a bit like The Dukes of Hazzard, using their ship to do handbrake turns, and yelling "yeehaw".
- fnordpiglet 3y agoGeorge Green, who discovered Greens Theorem, was such a bumpkin. His father was a miller in the unfashionable countryside, and he had a modest education. A mystery of math history is how such a bumpkin was so poorly versed in advanced mathematics (inaccessible to someone far from a university, where such knowledge was confined at that time), discovered such remarkable mathematics that the average engineering undergrad knows his name. https://en.m.wikipedia.org/wiki/George_Green_(mathematician) https://en.m.wikipedia.org/wiki/George_Green_(mathematician) Frankly history is replete with bumpkins making extraordinary discoveries. Being a bumpkin is associated with ignorance, not stupidity. Intelligence is pretty uniformly distributed, even among the black, short, fat, and bumpkins.
- pugworthy 3y agoI would probably describe him as a scientist who moonlighted as a parson, not the other way around.
- peterfirefly 3y agoDaylighted as a parson, surely?
- AlbertCory 3y agoSomewhat related: I just read a history of England where it was stated that country parsons had a very, very good living and not much work to do, up until 1850 or so, and many of them devoted their energies to all sorts of useful projects. Then the money dried up, as agriculture changed.
- blacksqr 3y agoIn fact, many men with literary or scientific aspirations aimed for careers in the clergy for just this reason. It was a lifetime scholarship.
- yareally 3y agoAlso music. Antonio Vivaldi was a priest, but had a special dispensation that excused him from most of the required duties. Gave him a lot of time to compose music.
- graemep 3y agoVery different as Vivaldi was an Italian (and presumably a Catholic priest) and he would have needed the special dispensation form his duties. What was specific to the Anglican church in England at the time was that because of the control of the church by the state and the aristocracy it was possible for people with the right connections to be just handed the job with little requirement to do it. IIRC they could even pay curate to do the actual work.
- blacksqr 3y agoThank you, my comment was intended to apply specifically to the Church of England. Any community that wanted a church was required to set aside farmland whose produce would be used to fund it, and the people had to donate their labor to work the land. So the English church had a rather unique arrangement where each parish had a source of funds independent of central government or church bureaucracy. That was the attraction of the job for intellectuals. As long as you kept your head down and didn't screw up big time, you were left alone.
- alex_young 3y agoIt’s worth noting that black holes were also independently described by Laplace in 1796. Quite a coincidence! https://researchonline.jcu.edu.au/9892/1/Microsoft_Word_-_Paper__Black_Hole_Concept_Final_.pdf https://researchonline.jcu.edu.au/9892/1/Microsoft_Word_-_Pa...
- ioblomov 3y agoHappens more often than you’d think: * Newton and Leibniz with calculus * Darwin and Wallace with evolution * all those shared Nobel Prizes by independent scientists (eg: Feynman and Tomonaga/Schwinger with quantum electrodynamics, et al) Presumably because knowledge converges and the field in question becomes ripe for discovery.
- roenxi 3y agoI'd bet economics. There are magic $/experiment thresholds where it becomes possible for scientists to try something, and one the threshold is crossed a bunch of people explore the same area at the same time. Take neural nets. FLOPS/$ crosses some magic number so that universities can afford the hardware, and bam; AI everywhere. No obvious theoretical breakthroughs since the 70s, but suddenly the field gets intense due to economics.
- Gh0stRAT 3y agoIIRC backpropagation was a very significant breakthrough on how to update weights when training neural nets.
- account-5 3y agoTIL: > ... it is conceivable that our entire observable universe is a supermassive black hole within a larger universe.
- pratnala 3y agoIt is black holes all the way down
- fasterik 3y agoYou're probably joking, but in case not, I would point out that black holes evaporate quickly at small scales, and cannot be smaller than the Planck length. One of my pet peeves is this vague idea about the universe being an infinite fractal, universes inside atoms, etc. It's an appealing idea, but it's totally inconsistent with quantum mechanics and the difference between the strength of forces on different length scales.
- pratnala 3y agoI was joking, yes :)
- ioblomov 3y agoThis mindfuck struck me too. Could a physicist speak to this? Is a black-hole universe a theoretical possibility because it’s a valid solution, say, of the Einstein field equations? Or is it a possibility simply because it’s not falsifiable?
- d1sxeyes 3y agoI don’t think it’s possible to say. Our current definitions of spacetime is limited to what is in the observable universe. What’s on the other side could be a whole different universe with similar spacetime. Or it could be an infinite void. Or it could literally not exist. Or it could be a vast sea of cream cheese. We don’t know, and according to our current understanding of physics, it is impossible for us to ever know. Edit: not a physicist by the way, would also love someone who actually knows what they’re talking about to butt in.
- UberFly 3y agoIt seems like he had a brain like Einstein but didn't have the means around him at the time to cultivate his ideas. Definitely in the majority I'm sure. Only some are in the right place at the right time.
- potamic 3y agoAs Newton said, "If I have seen further, it is by standing on the shoulders of giants".
- jtbayly 3y agoI quit here: “it is conceivable that our entire observable universe is a supermassive black hole within a larger universe.” It’s also possible that you’re just a simulation. What is the point? Just to shock.
- deleted 3y ago[deleted]
- fasterik 3y agoThis seems like a legitimate scientific question. What is the mass of the observable universe, and can light escape it? It's no more pointless than asking what the universe was like at the big bang or what it will be like 10^100 years from now.
- vfclists 3y ago> No portrait of Michell exists, but he was described as “a little short man, of black complexion, and fat.” Why are Wikipedia contributors hallucinating the meaning of "black complexion"? Apparently since "black people" were not capable of intelligent thought, "black complexion" means "In this case it means he was sad and melancholy". Do Wikipedia contributors then think that "fair or white complexion" must mean "happy and high-spirited"? Or is it because all the black people around in the medieval era were uneducated slaves performing menial tasks? What terminology would be used describe the complexion of people of "black African appearance" if "black complexion" meant "sad and melancholy" people? Charles II was described as "tall black man" when he was on the run during the civil war. I guess those on the look out for him were supposed to look for a tall, "sad and melancholy" looking man, as though that would be a help in picking him out, forgetting that in the middle of a bloody civil war there would be lot of sad people of all heights, shapes and widths out and about.
- fortran77 3y agoApparently the word "complexion" has shifted in meaning and it used to mean "temperment" even into the 19th century. https://en.wiktionary.org/wiki/complexion#Etymology https://en.wiktionary.org/wiki/complexion#Etymology
- kbelder 3y agoAre you saying that you think that description means the Michell was likely African-American? Or are you just saying that that description refers to a physical trait of being relatively dark-skinned for a Caucasian, instead of a behavioral trait? I would have parsed that as meaning he behaved in a generally dour way.