[HN Gopher] Gravitational Machines
___________________________________________________________________
Gravitational Machines
Author : sohkamyung
Score : 182 points
Date : 2023-06-09 13:06 UTC (9 hours ago)
(HTM) web link (arxiv.org)
(TXT) w3m dump (arxiv.org)
| munchler wrote:
| I think this idea is essentially an example of a "gravitational
| slingshot".
|
| I found it interesting that such a system could be used to
| "accelerate delicate and fragile objects to a velocity of 2000
| km/sec at an acceleration of 10,000 g, without doing any damage
| to the objects. ... So a large space ship with human passengers
| and normal mechanical construction could easily survive the
| 10,000 g acceleration." This seems counterintuitive, but since
| the object is in freefall the entire time, I guess it makes
| sense.
| Qem wrote:
| The 10,000g would be approximately uniform through the entire
| volume of the ship, so no damage. In a regular rocket, the
| acceleration would have to be transmitted to passengers and
| cargo through the normal force, and that would crush you.
| mrkstu wrote:
| Makes sense, though if you'd asked me before your
| explanation, I'd have thought the idea of accelerating at
| high speed without leaving free fall impossible.
| z3t4 wrote:
| A gravitational assist/slingshot is just a transfer, think of
| cogs in a machine - by using axles and cogs you can change the
| speed and direction of the forces. source: KSP player
| [deleted]
| [deleted]
| abecedarius wrote:
| Does anyone have an idea what sort of design could achieve the
| proposal near the end:
|
| > Clearly the immense loss of energy by gravitational radiation
| is an obstacle to the efficient use of neutron stars as
| gravitational machines. It may be that this sets a natural limit
| of about 108 cm/sec to the velocities that can be handled
| conveniently in a gravitational technology. However, it would be
| surprising if a technologically advanced species could not find a
| way to design a nonradiating gravitational machine, and so to
| exploit the much higher velocities which neutron stars in
| principle make possible.
|
| From my dim memory of Kip Thorne's popular book, a spinning black
| hole could be used in this way, which would mean there's at least
| one solution.
| howexactly wrote:
| how exactly is energy extracted from such a system?
| bluepoint wrote:
| When a (perfect) ball is thrown at a (perfect) car, it will
| bounce off with the same velocity, v, but with its direction
| reversed. If the car is moving with some velocity -V, when the
| ball bounces off it will have a velocity -v - 2V, gaining an
| extra -2V. (This is easier to understand from the car's
| passenger's point of view, who will see the ball arriving with
| a relative velocity v + V and bouncing with -v - V, or -v - 2V
| relative to the ground).
|
| In the ball-car collision the electromagnetic forces are the
| ones responsible for changing the direction of the ball. But in
| the binary system, it is gravity. In particular as the shuttle
| enters orbit around the "incoming" star, the star's gravity
| will pull it forward mostly when it completed half orbit.
|
| I hope I make sense.
|
| Overall, such a joy to read this paper. With basic physics it
| makes you dream of sci-fi...
|
| EDIT: typos
| aruggirello wrote:
| Your ball morphed into another car at the second sentence.
| Surely an effect of quantum entanglement :)
| [deleted]
| Robotbeat wrote:
| A large mass is dropped on the right trajectory between the
| two, the gravitational forces slingshot it back at higher
| velocity, which can be captured with some sort of
| electromagnetic regenerative braking mechanism. Just a toy idea
| for how energy can be extracted.
| oopsemist wrote:
| Opposite is true also: it's possible to add energy into three
| body system and increase distance between them
| (antigraviation). In principle, spherical gradient of
| gravitation creates possibility to increase orbit using only
| energy and interaction between masses even in two body system
| (if smaller body can change it shape and distibution of mass
| to simulate three body system). I had idea of such aparatus
| when I was student 30 years ago, but then I forgot the
| details.
| PaulHoule wrote:
| It's an established technology
|
| https://en.wikipedia.org/wiki/Gravity_assist
|
| there is nothing speculative about it
| mr_mitm wrote:
| Figure 1 shows one possible mechanism. It's basically a
| gravitational slingshot using a binary star system. A test mass
| comes out with more kinetic energy than before and the binary
| star system's radius decreases, releasing gravity waves at the
| same time.
| howmayiannoyyou wrote:
| Can't say exactly, but kinetic energy can slightly alter mass.
| For example, increasing the speed of an object increases its
| mass.
| HarHarVeryFunny wrote:
| Of course there are also more mundane ways of utilizing gravity
| such as Tidal and Hydroelectric power, or just walking
| (controlled falling) for that matter.
| amelius wrote:
| But tidal energy will make the Moon lose altitude. Better to
| experiment outside the solar system.
| aldousd666 wrote:
| This talks about two bodies, but would the Halo Drive
| (https://arxiv.org/abs/1903.03423) also be one such thing? I
| mean, I guess the photons are the other bodies?
| mr_mitm wrote:
| I always wondered how you might be able to extract energy from
| the expansion of space. It's particularly interesting because
| conservation of energy does not hold on such large scales.
| oopsemist wrote:
| > It's particularly interesting because conservation of energy
| does not hold on such large scales.
|
| IMHO, conservation of energy still applies, so Big Bang model
| is just wrong. Use Occam's razor when in doubt.
| mr_mitm wrote:
| I'm not in doubt on this question. Please refer to https://ww
| w.preposterousuniverse.com/blog/2010/02/22/energy-... for a
| digestible piece on this topic.
| raattgift wrote:
| Think about harpooning a galaxy at, say, 100 megaparsecs,
| with a long rope attached to the harpoon. In the Milky Way,
| loop the rope around the rotor of an electric generator. In
| the distant galaxy, have the harpoon-end of the rope fall
| into its central supermassive black hole. Ignoring proper
| motions (the black hole and the electric generator are
| likely to move within their host galaxies, and their host
| galaxies within their galaxy cluster), this gives one about
| 72 kilometres per second per megaparsec of linear speed on
| the rope as the space between us and the distant galaxy
| increases.
|
| Of course, you need a lot of rope, for the rope to be
| indestructible (and ideally of low mass), for lucky aim
| when harpooning, and for the harpoon to be able to carry
| rope all the way to the target, and for the target and far
| end of the rope to be impossible to separate.
|
| The more local model for this is to erect a scaffolding
| well above an object in hydrostatic equilibrium (so
| anything from a round planet to a supermassive black hole)
| and fix electric generators to the scaffolding, driven by
| ropes dropping onto the scaffold-surrounded object. There
| are a lot of physics questions that can be explored using
| that model; it's a good exercise in all of them. (Some
| coursework uses this setting to explore the dominant energy
| condition of general relativity, since that imposes a
| maximum tensile strength on non-exotic matter rope or wire
| or filament: there is a speed limit on the operation of
| intermolecular/interatomic binding forces; c.f. Bell's
| rope-spaceship "paradox" in special relativity.)
|
| > energy is not conserved
|
| Carroll's point is that there is a generalization of
| conservation of energy in curved Lorentzian spacetimes,
| where changes in the motion of matter and changes in the
| spacetime geometry are exactly related. That applies in the
| harpoon-a-distant-galaxy model as well. The rope (and
| stresses within it) and power produced by the electric
| generator are all forms of moving matter, creating a
| geometrical change which (depending on the properties of
| the rope) may become non-negligible. A rope that is strong
| enough (and implicitly having much more mass per cm^3 than
| empty space) to connect two megaparsec+-separated galaxies
| (driving a generator at one end for appreciable time and
| feeding a black hole at the other for appreciable time)
| forces one into some calculating to answer the question:
| does the rope slow the metric expansion along its length?
|
| Next, how do you get the generator to turn rather than be
| carried out of our galaxy? (We can sharpen this somewhat by
| dispensing with a generator, and throwing each end of our
| megaparsecs-long rope into a megaparsecs-separated galactic
| centre black hole. What happens if there is a large mass-
| ratio (heavy:light) between the black holes, or their
| surrounding galaxies? Does the lighter black hole get
| pulled out of its galaxy by the heavier? What happens as
| the mass ratio goes to 1?
|
| Carroll's link above, showing \Nabla_{\mu}T^{\mu\nu} = 0
| says that as long as we don't introduce further degrees of
| freedom we can calculate the equations of motion in the
| systems above. That is, it's fine for an expanding space
| with nonzero vacuum energy, and for that plus
| noninteracting (except by gravity) dusts. However, our very
| long rope cannot be non-interacting (it must be at least
| self-interacting) and its extra degrees of freedom are
| liable to become important under extreme tension (e.g., it
| might get hot and radiate a ~blackbody spectrum), so a
| somewhat different covariant equation would apply.
| comboy wrote:
| Said rope is part of the expanding Universe i.e. it also
| expands, just the right amount, doesn't it?
| abbusfoflouotne wrote:
| Reminds me a lot of the Three Body Problem by Cixin Liu. Lot of
| space travel concepts explored there similar to this.
|
| https://www.amazon.com/Three-Body-Problem-Remembrance-Earths...
| sgt wrote:
| [flagged]
| forgetfreeman wrote:
| No, no it is not.
| lb1lf wrote:
| In a similar vein, John Kraus (Of Antennas... textbook fame)
| described a gravitational transmitting and receiving system as a
| fun (?) diversion near the end of the book.
|
| It has been a few years, but I seem to recall that the
| transmitter was a 500T steel bar spun at very close to the
| maximum RPM the tensile strength of steel allowed; the radiated
| energy was something like a fraction of an attowatt. (An attowatt
| = 1*10^-18W)
|
| There are more efficient transmitting schemes out there.
| agmm wrote:
| I became curious about this and went to the book to learn more.
| The system proposed in the book is capable of radiating around
| 2.2 x 10^-29 W by rotating a bar weighing 500 tonnes about 270
| times per minute.
|
| [1] Source: Kraus, J. D. (1988). Antennas (2nd ed., p. 769).
| Retrieved from
| https://ia802907.us.archive.org/8/items/KrausAntennas19882ed...
| bee_rider wrote:
| It is kind of wild that we stumbled upon transmitting
| information via electromagnetic waves so early on. They seem to
| be hard to beat.
| jjk166 wrote:
| It makes sense that the easiest to implement would also be
| the easiest to learn. It's more shocking just how much harder
| every other option is.
| comboy wrote:
| What other options are there apart from mentioned gravity?
| I mean there are waves in materials like sound but that
| seem to be easier than EM.
| alach11 wrote:
| Neutrinos, perhaps.
| dekhn wrote:
| it doesn't seem surprising to me. people were in the lab
| playing with DC and AC and clearly heard "clicks" from remote
| instruments that correlated with them turning switches on and
| off.
| thx-2718 wrote:
| Fortunately for us we can see them.
|
| Gravity waves are much harder to observe.
| BurningFrog wrote:
| You can also argue that we can see them _because_ they are
| stronger and are evolutionary important.
| mrkstu wrote:
| Well, I'd call the inner ear an evolutionary response to
| gravity...
| db48x wrote:
| Not unexpected; electromagnetism is 40 orders of magnitude
| stronger than gravity!
| valyagolev wrote:
| It's an article from 1962:
|
| "After the detection of the gravitational wave GW170817, Jason T.
| Wright (Physics Today, 72, 5, 12, 2019) reminded the community
| that many of its features had been predicted by Dyson more than
| half a century earlier. Dyson's article was published only once,
| in Cameron's long out of print collection, though a scan may be
| found at the web site of the Gravity Research Foundation
| (https://www.gravityresearchfoundation.org). Dyson thought it had
| been reprinted (in his Selected Papers, AMS Press, 1996, forward
| by Elliot H. Lieb) but it was not. Hoping to make the article
| easier to find, I wrote Dyson for his permission to post it at
| the arXiv"
|
| It's about using two big bodies, A and B, to accelerate objects:
| "The energy source of the machine is the gravitational potential
| between the stars A and B. As the machine continues to operate,
| the stars A and B will gradually be drawn closer together, their
| negative potential energy will increase and their orbital
| velocity V will also increase."
| samstave wrote:
| Would Google happen to have a scan of this in their whatever-
| its-called-book-scanning-archive?
| ur-whale wrote:
| Nice idea.
|
| I wonder if one could calculate an upper bound of the available
| potential gravitational energy available in the entire universe
| by estimating how far every massive point (baryon) is from all
| the others.
| floobertoober wrote:
| If space is expanding, does that also mean that gravitational
| potential energy is always increasing, too? I'd never thought
| of that before
| cyberax wrote:
| It's not. Moreover, the total energy is actually being
| lost, as particles "lose" kinetic energy due to expansion
| (and the light is red-shifted).
|
| If this seems to violate the law of energy conservation,
| you're spot on. It is indeed being violated.
|
| This is not fundamentally problematic by itself, because
| the law of conservation of energy depends on time
| invariance. Which doesn't hold in the case of an expanding
| universe. But it is an unsatisfying copout, and we hope
| that it can be resolved by the quantum gravity.
| titzer wrote:
| Space in our universe has a vacuum energy and our
| expanding (actually, accelerating) universe is in fact
| gaining "dark" energy.
|
| https://en.wikipedia.org/wiki/Dark_energy
| cyberax wrote:
| There is no known mechanism by which the lost energy can
| drive the expansion.
|
| Moreover, expansion without dark energy would still cause
| the kinetic energy loss.
|
| There are attempts to define the total energy of the
| universe in GR in such a way that it is preserved, but so
| far none are really successful.
| oopsemist wrote:
| Yes, it should increase on paper, but no source of energy
| to power that expansion is found yet. Big Shrink can power
| itself, so I'm voting in favor of
| https://en.wikipedia.org/wiki/Shapley_Attractor
| pdonis wrote:
| No, it doesn't, because the concept of "gravitational
| potential energy" is not meaningful for an expanding
| universe considered as a whole. It's only meaningful for
| isolated systems within the universe.
| thx-2718 wrote:
| Wouldn't there be meaning in saying it would take this
| much energy to push all the matter in the universe to one
| place?
|
| Which that amount should be increasing as space-time
| expands.
|
| Thought experiment, if you could place a mass of an
| arbitrary amount at any one point in space, how much mass
| would you need such that all the mass of the universe is
| now falling towards it.
|
| Or could you bend space-time to a point that all mass
| falls into it.
| pdonis wrote:
| _> Wouldn 't there be meaning in saying it would take
| this much energy to push all the matter in the universe
| to one place?_
|
| No. The universe is not an isolated system that we can
| operate on from the outside. You can't treat it as though
| it is. So your thought experiments aren't meaningful.
| thx-2718 wrote:
| Obviously the thought experiment requires energy that
| doesn't 'exist' or doesn't have meaning in the sense that
| it could happen literally. It's a what-if and that does
| have a number and that does have meaning.
|
| So there is meaning to the previous persons question
| which is what the thought experiments were meant to show
| but obviously that's something you can't imagine.
| pdonis wrote:
| _> Obviously the thought experiment requires energy that
| doesn 't 'exist'_
|
| No, it requires energy to be _added_ to the system from
| _outside_ the system. Which is precisely what you
| _cannot_ do with the universe as a whole. That 's what
| makes such thought experiments meaningless for the
| universe as a whole.
| faangsticle wrote:
| Now take off your nitpick hat and ignore that detail. Its
| what makes it a thought experiment.
| pdonis wrote:
| You can't ignore it because it's not a "detail"--it's a
| crucial feature of the thought experiment that doesn't
| work for the universe as a whole. What you're suggesting
| is like saying, in my thought experiment I assume that 2
| + 2 = 5, just ignore the fact that 2 + 2 is actually 4.
| faangsticle wrote:
| Yes, that's what a thought experiment is. A cat can't be
| alive and death at the same time, either.
| thx-2718 wrote:
| > it requires energy to be added to the system from
| outside the system.
|
| Yes that is exactly what energy that doesn't 'exist'
| means.
| wyager wrote:
| How is your objection not a useless and unfalsifiable
| catch-all that applies to calculating any quantity over a
| volume?
| pdonis wrote:
| Um, what? I can operate on an ordinary volume (say a
| beaker in my lab or a planet that I am in a distant orbit
| around) from the outside. I can't operate on the universe
| as a whole from the outside. How is this not an obvious
| difference?
| wyager wrote:
| Why is it not meaningful? "Isolated systems" seems
| meaningless - there is no objective cutoff where a
| gravitational system becomes "isolated", except perhaps
| in the sense of "non-intersecting light cones".
| pdonis wrote:
| See my response to thx-2718 downthread, about having to
| add energy from outside the system.
| [deleted]
| westurner wrote:
| The gravitational energy available without critical impulse
| at non-Lagrangian points; the gravitational potential energy
| where gravitational forces are not balanced? Are
| gravitational wave convolutions ever sufficient to cause a
| massful thing _at rest_ at a _Lagrangian point_ in the
| gravitational wave fluid field to move out of their inertia?
|
| I'll ask [Bard,] first:
|
| P: _What are the formulas for threshold force and critical
| impulse as sympy code,_
|
| > _The threshold force and critical impulse can be used to
| calculate the minimum amount of force that must be applied to
| an object to start it moving and the total momentum that must
| be imparted to the object, respectively._
|
| But "coefficient_of_friction" might instead be a fluid
| viscosity and/or curl term? When is fluid density zero?
|
| P: _What are the formulas for threshold force and critical
| impulse as sympy code, and then again with fluid viscosity
| instead of coefficient of friction?_
|
| > _As you can see, the threshold force and critical impulse
| are both proportional to the fluid viscosity. This makes
| sense, because a more viscous fluid will create more drag,
| which will make it more difficult to start an object moving._
|
| > _It is important to note that the formulas above are only
| valid for laminar flow. In turbulent flow, the threshold
| force and critical impulse will be much greater._
|
| > _Whether or not it makes sense to use fluid viscosity
| instead of coefficient of friction depends on the specific
| situation. If the object is moving through a fluid, then it
| is important to consider the fluid viscosity. However, if the
| object is not moving through a fluid, then the coefficient of
| friction is the more relevant parameter._
|
| P: _how does viscosity apply to superfluid quantum gravity
| with bernoulli 's?_
|
| > _[rotation of galaxies, rotation of planets,] The expansion
| of the universe: The expansion of the universe: The expansion
| of the universe is thought to be driven by dark energy. Dark
| energy is a mysterious force that is causing the universe to
| expand at an accelerating rate. One possible explanation for
| dark energy is that it is a type of superfluid with negative
| viscosity. This would mean that the pressure in the
| superfluid would increase as the volume of the universe
| increases, which would cause the universe to expand even
| faster._
|
| P: _How do we model 3 body gravity problems where it is
| possible to move bodies 1 and 2? Do we model such n-body
| gravity problems differently with superfluid quantum
| gravity?_
|
| > _In classical physics, 3-body gravity problems are
| typically solved using numerical methods. These methods
| involve integrating the equations of motion for each body in
| the system, taking into account the gravitational forces
| exerted by the other bodies._
|
| > _In superfluid quantum gravity, 3-body gravity problems can
| be modeled using a different approach. In this approach, the
| universe is modeled as a superfluid, and the bodies in the
| system are modeled as vortices in the superfluid. The
| gravitational force between two bodies is then modeled as the
| interaction between two vortices._
|
| > _[...]_ Here are some additional details about how 3-body
| gravity problems are modeled in superfluid quantum gravity:*
|
| > _- The equations of motion for the vortices are derived
| from the Navier-Stokes equations for a superfluid._
|
| > _- The gravitational force between two vortices is
| calculated using the Biot-Savart law._
|
| > _- The system is typically simulated using a numerical
| method called the finite element method._
|
| > _- The simulations can be used to study a variety of
| phenomena, such as the formation of binary stars and the
| evolution of planetary systems. [...]_
| westurner wrote:
| What is the issue with this comment?
| cwillu wrote:
| https://chat.openai.com/share/39580cd0-b5b2-4bec-89d4-092
| 97c...
|
| "[...] 5. Perceived Irrelevance or Lack of Relevance:
| Depending on the context of the Hacker News post, copy-
| pasting AI-generated content might be seen as irrelevant
| or not contributing to the topic at hand. This can be
| frustrating for users who are looking for meaningful and
| relevant insights from other community members."
| throwway120385 wrote:
| If I wanted to know what Bard or ChatGPT had to say about
| this, I would ask them.
| westurner wrote:
| But you don't know to ask: that's the problem; They're
| all trying new QG and dark energy correction factors.
|
| One can't solve 3-body problems without Superfluid
| Quantum Gravity, thus this that I took the time to add is
| very relevant.
|
| Not worth helping then.
| westurner wrote:
| Given such an anti- AI-with-citation policy, researchers
| preparing comment content with citations for the platform
| have a counterproductive incentive to parallel construct
| after using e.g. search engines that use AI (Google,
| Bing,), and also an incentive to not cite their sources?
| [deleted]
| westurner wrote:
| > _One can 't solve 3-body problems without Superfluid
| Quantum Gravity_
|
| The article (from 1962) does not predict 3-body
| accelerations of large masses or particles using current
| methods (probably because they had not yet been developed
| at the time).
|
| (Ironically, in context to the rejection of AI methods to
| summarize superfluid Quantum Gravity for the thread's
| benefit (and not my own),)
|
| N-body gravity problems are probably best solved by AI
| methods; it is well understood that there are no known
| closed-form solutions for n-body gravity problems.
|
| Three body problem: https://en.wikipedia.org/wiki/Three-
| body_problem
| thumbuddy wrote:
| I'd love to see a chatbot try lol. That's all I'll say
| about that...
| bookofjoe wrote:
| Dyson was like George Gamow, protean in intellectual power and
| scope and imagination yet forever just outside the Nobel
| sphere.
| heywhatupboys wrote:
| I think you are being a bit Anglo-centered.
| bookofjoe wrote:
| Georgiy Antonovich Gamov (Ukrainian: Georgii Antonovich
| Gamov, Russian: Georgii Antonovich Gamov) was born on March
| 4, 1904 in Odessa, Russian Empire (now Ukraine).
|
| His father taught Russian language and literature in high
| school, and his mother taught geography and history at a
| school for girls. In addition to Russian, Gamow learned to
| speak some French from his mother and German from a tutor.
| Gamow learned English in his college years and became
| fluent. Most of his early publications were in German or
| Russian, but he later used English for both technical
| papers and for the lay audience.
|
| He was educated at the Institute of Physics and Mathematics
| in Odessa[2] (1922-23) and at the University of Leningrad
| (1923-1929). Gamow studied under Alexander Friedmann in
| Leningrad, until Friedmann's early death in 1925, which
| required him to change dissertation advisors. At the
| university, Gamow made friends with three other students of
| theoretical physics, Lev Landau, Dmitri Ivanenko, and
| Matvey Bronshtein. The four formed a group they called the
| Three Musketeers, which met to discuss and analyze the
| ground-breaking papers on quantum mechanics published
| during those years. He later used the same phrase to
| describe the Alpher, Herman, and Gamow group.
|
| Upon graduation, he worked on quantum theory in Gottingen,
| where his research into the atomic nucleus provided the
| basis for his doctorate. He then worked at the Theoretical
| Physics Institute of the University of Copenhagen from 1928
| to 1931, with a break to work with Ernest Rutherford at the
| Cavendish Laboratory in Cambridge. He continued to study
| the atomic nucleus (proposing the "liquid drop" model), but
| also worked on stellar physics with Robert Atkinson and
| Fritz Houtermans.
|
| In 1931, Gamow was elected a corresponding member of the
| Academy of Sciences of the USSR at age 28 - one of the
| youngest in its history. During the period 1931-1933, Gamow
| worked in the Physical Department of the Radium Institute
| (Leningrad) headed by Vitaly Khlopin [ru]. Europe's first
| cyclotron was designed under the guidance and direct
| participation of Igor Kurchatov, Lev Mysovskii and Gamow.
| In 1932, Gamow and Mysovskii submitted a draft design for
| consideration by the Academic Council of the Radium
| Institute, which approved it. The cyclotron was not
| completed until 1937.
|
| Defection
|
| Gamow worked at a number of Soviet establishments before
| deciding to flee the Soviet Union because of increased
| oppression. In 1931, he was officially denied permission to
| attend a scientific conference in Italy. Also in 1931, he
| married Lyubov Vokhmintseva (Russian: Liubov'
| Vokhmintseva), another physicist in Soviet Union, whom he
| nicknamed "Rho" after the Greek letter. Gamow and his new
| wife spent much of the next two years trying to leave the
| Soviet Union, with or without official permission. Niels
| Bohr and other friends invited Gamow to visit during this
| period, but Gamow could not get permission to leave.
|
| Gamow later said that his first two attempts to defect with
| his wife were in 1932 and involved trying to kayak: first a
| planned 250-kilometer paddle over the Black Sea to Turkey,
| and another attempt from Murmansk to Norway. Poor weather
| foiled both attempts, but they had not been noticed by the
| authorities.
|
| In 1933, Gamow was suddenly granted permission to attend
| the 7th Solvay Conference on physics, in Brussels. He
| insisted on having his wife accompany him, even saying that
| he would not go alone. Eventually the Soviet authorities
| relented and issued passports for the couple. The two
| attended and arranged to extend their stay, with the help
| of Marie Curie and other physicists. Over the next year,
| Gamow obtained temporary work at the Curie Institute,
| University of London, and the University of Michigan.
|
| https://en.wikipedia.org/wiki/George_Gamow
| throwway120385 wrote:
| Mr. Tompkins in Paperback is an excellent read if you're
| curious about the practical effects of relativistic time
| dilation.
| [deleted]
| robertlagrant wrote:
| Is that why he invented the Dyson Sphere?
| samstave wrote:
| Seems like a well rounded fellow.
| swader999 wrote:
| Circular logic.
| mayormcmatt wrote:
| No, spherical logic.
| TeMPOraL wrote:
| No, distributed swarm logic, as apparently he later
| admitted that what he _thought_ about was what we now
| call a _Dyson swarm_ , and it's just the public that took
| the "sphere" bit literally and run with it.
| [deleted]
| 0xAltCunningham wrote:
| [dead]
| photochemsyn wrote:
| Dyson was quite the visionary. LIGO / Virgo gravitational wave
| detectors have confirmed all this (with much more development
| from people like Caltech's Kip Thorne and many others):
|
| > "The energy source of the machine is the gravitational
| potential between the stars A and B. As the machine continues to
| operate, the stars A and B will gradually be drawn closer
| together, their negative potential energy will increase and their
| orbital velocity V will also increase... the loss of energy by
| gravitational radiation will bring the two stars closer with
| ever-increasing speed, until in the last second of their lives
| they plunge together and release a gravitational flash at a
| frequency of about 200 cycles and of unimaginable intensity."
|
| The Ligo Lab's youtube channel has lots of great videos on the
| topic, from the sounds made by a pair of colliding black holes to
| long talks about how certain elements are mostly made by
| colliding neutron stars:
|
| https://www.youtube.com/@LIGOLabCaltechMIT/playlists
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