What happens when you fall into a black hole?

[@justmyopinion2205]

Great lesson on black holes. I found myself saying “WOW! That is so cool!”, way too many times. Thank you very much for your lessons.

[@braddixon3338]

Hmmm, learned a couple things here, 1) larger black holes don't tear you apart as you enter, and 2) there is energy lost as you approach the black hole, which changes the perceived wavelength of light of the object as it nears the black hole. Great stuff, keep them coming. I'm subscribed and always enjoy your content!

[@abakanazer]

There is en unspoken caveat in this presentation... As object which slows down as they close near the horizon of the black hole, we know they in fact speeds up, as they fall in. But something must give up.. and that is "the length of the travel" object needs to pass from standard space to the horizon. That length reaches infinity, and that is also the reason why the object seems to go slower and slower as it approaches the horizon of the black hole. Couse, you need time more then universe have itself to pass through infinite length. Fun fact, that is also a reason you can not turn back! Black hole is literally an infinite length hole in the fabric of space-time. Mindblowing eh...

[@subirmajumdar4493]

It will tear you apart, just give it a couple more mili seconds because of the distance involved.

[@sasca854]

​@@subirmajumdar4493 It's true that the time between first feeling the tidal forces to being torn apart by said tidal forces is very short-- only 100ms or so traveling at nearly the speed of light. But the entire journey to that point from the edge of the horizon takes much longer than that for SMBHs. Sag A* is roughly 12 million km wide, so it would still take ~30 to 40 seconds to be spaghettified. TON 618's black hole is more massive than an _entire small galaxy_ and has an event horizon 30x wider than the solar system; it would take you _weeks_ to fall far enough into it to be spaghettified. This is all in contrast to stellar mass black holes, where you are spaghettified before you even reach the event horizon.

[@MichaelChatary]

If that was true how would we know bruh....

[@Condor512]

Thanks Dr. Don, for another great, informative, and 'fun' video. I don't know how you do it, but please don't stop. Your physics videos make my week 👍.

[@TerryBollinger]

4:07 "As the object gets very close to the event horizon, a distant observer can see the time between blinks take a thousand years, then a million, and eventually longer than the lifetime of the universe." Five other fun effects often overlooked when falling into a black hole are (1) tunnel vision, (2) UV obliteration, (3) quantum orbiting, (4) watching the universe end, and (5) watching the black hole evaporate before you. (1) Tunnel vision: As you approach the event horizon, your line of sight is warped by the bending of light into parabolas, like baseballs tossed into the air. Parabolic light makes the black hole's horizon appear to rise as your line of sight bends more and more sharply back towards the surface of the black hole. Consequently, your view of the outside world becomes an ever-shrinking tunnel that ends in a pinprick of intense light. (2) UV obliteration: Just as _rising_ light increases in wavelength and fades in intensity, _falling_ light does the opposite. It increases in frequency and amplitude until the light your distant friend helpfully shines toward you escalates not just into the ultraviolet but into the extreme gamma range. First, it obliterates you chemically. Next, it induces nuclear fusion. But those nuclei don't last since ever-higher gammas break down your nuclei into a neutron-proton plasma. Finally, even your protons and neutrons collapse into a quark-gluon plasma. You may want to ask your friend not to bother with the helpful light! (3) Quantum orbiting: You might think higher gravity would overcome any "off-target" aiming. Not so! Angular momentum is a stubbornly conserved quantity that gets more, not less, extreme as you approach a target. Think instead of ice skaters pulling in their arms to spin ever faster. A particle with the slightest deviation from "straight down" must, eventually, transfer all that angular momentum into the black hole's rotation. It becomes a quantum issue for individual particles: How can the particle fall in if doing so removes its angular momentum from the universe? A more likely outcome for such a particle is to enter into an event horizon momentum state akin to ones Gerard 't Hooft has proposed in recent years. Even under such extreme conditions, the most minute units of sideways-moving angular momentum must quantize. For particles, the result is akin to an enormously scaled-up, gravity-bound version of an atomic _p_ (or higher) orbital. (4) Watching the universe end: Just as your outside friend sees your time slow down, you observe your friend's time speed up by symmetry. Near the event horizon, this gets extreme in both directions. In fact, in the split instant before hitting the event horizon, you see the end of the universe! Now, if you are a fan of paradoxes, think about that for a moment: How, precisely, does one "observe" the end of the universe if the black hole into which you are falling is, by definition, part of that universe? The counter to this - a good one - is that you, the infalling person _must_ conserve linear momentum in your frame. Thus you cannot stop at the event horizon and wait for the end of the universe. Relativity says you _must_ plow through the event horizon smoothly from your perspective. The momentum-conserving smoothness argument is valid and brings up the final point, which is… (5) Watching the black hole evaporate before you: Assuming all your particles are headed straight down - the black-hole equivalent of atomic _s_ orbitals - you need not worry about slowing down to watch the universe end. That's because, due to Hawking radiation, even the most gigantic black evaporates at incredible speed just in front of you, doing so quickly enough not to slow you down. Your gravitational time dilation keeps increasing until it reaches a balancing point for preserving your inbound linear motion. You don't need to know how much you slowed down since it's a self-correcting loop: Slower evaporation means slower time flow for you, and faster evaporation means faster time flow. To you, it's all smooth: The black hole, no matter how big, goes _poof_ just before you pass through its event horizon, removing any chance of you observing its interior. Singularities need not apply! ---------- Terry Bollinger CC BY 4.0 2022-10-03.22.30 EDT Mon PDF: sarxiv.org/apa.2022-10-03.2230.pdf

[@Dragrath1]

The UV obliteration effect is one that rarely gets discussed and one which is likely quite relevant with respect to Hawking radiation as the infalling observer approaches the event horizon while this light would have long wavelengths to a distant observer this should no longer be the case for an infalling observer as time dilation also increases the luminosity. As light carries momentum would this not eventually result in the ionized particles that once constituted the observer and everything else that ever has or ever will fall into the black hole becoming embedded within the burst of evaporating hawking radiation as the in fall of gravity balances out with the radiation pressure much like how the radiation pressure from fusion reactions in a stars core balances out with gravity?(Though in this case the radiation pressure seems like it should dominate in the naive limit where all hawking radiation is via photons rather than including gravitational waves in the case of astrophysical black holes however the energies are so large relative to the radiation pressure needed to hold back the mass of a typical human observer that this probably doesn't matter much in principal) In this context a black hole is much like Hawking described in the title of his definitive paper really just a extremely time dilated explosion at least from the perspective of anything outside the black hole when it first gravitationally collapses.

[@TerryBollinger]

​@@Dragrath1, your idea is interesting enough that I've attempted to write my interpretation of it below. Please let me know if anything is in error. Beyond quoting what I think may be the most relevant section of the Hawking paper, please note that I have neither done a literature search on your idea nor assessed it mathematically. -Cheers, Terry Bollinger -------------------- *Dragrath's Hawking Radiation Equilibrium Theorem* (As interpreted by Terry Bollinger on 2022-10-05) Shouldn't UV obliteration work in _both_ directions, that is, on both light falling in from the outside universe and light rising from black hole Hawking radiation? Additionally, since the observer is falling towards the black hole rather than away from it, shouldn't the blue-shifted version of Hawking radiation eventually dominate and create an equilibrium point that keeps particles from falling any closer to the event horizon? As an observer approaches closely to the event horizon, the initially cold and negligible Hawking radiation of the black hole grows exponentially hotter and brighter due to time dilation and the inbound acceleration of the observer. Time dilation concentrates all light, whether from behind or in front. However, Hawking radiation gets blue-shifted more than light from the outside universe due to inbound acceleration. At some point, the radiation pressure of the outbound Hawking radiation should first reach and then exceed that of incoming light and then the gravitational pull of the black hole. At this hot equilibrium point - one well-hidden from the outside universe - the particle stops falling and thus never reaches the event horizon. The resulting _Hawking radiation equilibrium point_ thus would be akin to the radiation pressure from fusion in star cores that keeps them from entirely collapsing under gravity. The concept of a Hawking equilibrium point makes a black hole more akin to a highly time-dilated explosion. Interestingly, the title of Hawking's definitive 1974 paper _Black hole explosions?_ [1], suggests a similar view. Here is a related quote from that paper: ----- [1] S. W. Hawking, _Black Hole Explosions?,_ Nature *248,* 5443 (1974). "… Part of this wave will be scattered by the curvature of the static Schwarzschild solution outside the black hole and will end up on I- with the same frequency ω. This will give a δ(ω - ω') behaviour in α_(ωω'). Another part of the wave will propagate backwards into the star, through the origin and out again onto I+. These waves will have a very large blue shift and will reach I- with asymptotic form Cω^(-½) exp{-iωκ^(-1) log(v0 - v) + iωv} for v < v0 and zero for v ≥ v0, where v0 is the last advanced time at which a particle can leave I-, pass through the origin and escape to I+." -------------------- ---------- Terry Bollinger CC BY 4.0 2022-10-05.17.04 EDT Wed PDF: sarxiv.org/apa.2022-10-05.1704.pdf

[@juliavixen176]

@@TerryBollinger short answer: no Hawking radiation is basically the same thing as the Unruh effect. An observer in free-fall is not accelerating, that is, they are in an inertial reference frame, and at rest with respect to the various fields that we call “space”.

[@TheChzoronzon]

"The black hole, no matter how big, goes poof just before you pass through its event horizon" I have severe problems with all these concepts... if that's so, how can anything actually fall into a black hole? Btw, thanks for your work about open source software&like, you rock man

[@TheChzoronzon]

@@Dragrath1 I think you are asking the same as I, but better put, lol

[@duggydo]

Good to have the context along with the explanation.

[@talkingmudcrab718]

It depends on the black hole. For instance I fell into a Black Hole called "Indiana" and outside observers saw me build a family and buy a pickup truck.

[@bozo5632]

You may still be able to escape.

[@williamtetrault1300]

LOL!

[@RavenRedwood]

The event horizon is the point of no return So that must be Ohio

[@bsadewitz]

Indeed, J.C. Mellencamp, et. al. published prolifically on this in the 1980s.

[@yaakovgrunsfeld]

We were somewhere around Barstow on the edge of the desert when the Wall Drug signs began to appear. Before the sky cracked, Wall Drug had been a shopping center in South Dakota. There aren't a lot of things in South Dakota, so the own-ers of the shopping center had tried to turn it into a tourist attraction. They put up billboards along the highway-"Only thirty miles to Wall Drug!"-"Only twenty miles to Wall Drug!"-"Only another ten miles to go before WALL DRUG!" Presumably the expectation of getting ever closer would turn an ordinary shopping center into some sort of transcendental recreational/commercial experience. The radius had grown. "Only fifty miles to Wall Drug!" "Wall Drug, in just another hundred miles!" Finally, it metastasized through the entire Midwest, becoming the omphalos of its own coordinate system: "I don't know what state we're in, but it's only another two hundred eighty miles to Wall Drug." Some wag at US McMurdo Station had briefly planted a "9,333 Miles To Wall Drug" sign at the South Pole. After the sky cracked, the Wall Drug coordinate system started to impose itself more and more upon the ordinary coordinate system of longitude and latitude. Worse, the two didn't exactly correspond. You could be driving from New York to New Jersey, and find a billboard promising Wall Drug in only thirty miles. Drive another ten, and sure enough, WALL DRUG, TWENTY MILES. Drive ten more, and you'd be promised a South Dakotan shopping center, only ten miles away. Drive another ten, and ... who knows? No one has returned from Wall Drug in a generation. It's become not only an omphalos, but a black hole in the center of the United States, a one-way attraction and attractor fed by an interstate highway system which never gives up its prey. Some say it is in Heaven, others in Hell, others that it remains in South Dakota, from which no word has been heard for thirty years. Interstate travel is still possible, but it follows a very specific pattern. You go forward until you see a Wall Drug billboard. Then you hastily switch directions and go back to the previous city, transferring you back to the normal American landscape. Then you tentatively go forward again. After enough iterations, you can make it from Point A to Point B intact. But if ever you see a Wall Drug billboard and continue to travel, the land will start looking less and less like where you came from, more and more like the grassy semi-arid plains of South Dakota. Once that happens, you can still turn back. But if you turn back too late, you may find that Wall Drug is in that direction too, that every point of the compass brings you closer to Wall Drug, with no choice but to remain in place forever or go boldly towards that undiscovered country from whose bourn no traveler returns.

[@prabha5148]

I greatly appreciate your videos that you make and is very helpful and so I thank you for spending your valuable time for improving our knowledge Sir.

[@vinm300]

Nothing happens. If the Black hole is Galactic size the tidal force would be no different to being on Earth One wouldn't know one had crossed inside. One could spend years travelling to the centre.

[@d_mosimann]

Thank you for part I: From an outside perspective. Looking forward to part II: From the falling object's perspective, until it's inside the Black Hole and even beyond that.

[@DellAnderson]

Extremely fascinating! Thank you. To summarize, if we have to choose, fall into a super large black hole to avoid being torn to pieces as we would in a smaller one. But inside the black hole, you eventually get smashed into an infinitely small space anyway. But we would look like we were hovering on the event horizon forever. Crazy stuff!

[@funpinkgnome]

This guy's gotta be one of my favorite human beings. I love these videos.

[@tcarr349]

This guy is my favorite nerd from Fermilab!!

[@abelfonseca]

if objects take longer than the age of the universe to fall into a black hole from the perspective of an outside observer, then why do black holes exist from our perspective?

[@johnbennett1465]

Dr. Don, your explanation matches my understanding for non-rotating black holes. As I understand it, rotating black holes are more complicated. I know that frame dragging happens and maybe other effects, but I have no idea what this would mean to an object falling into it. So would you please make a video covering this. Thanks.

[@dugldoo]

Agreed! after all, all real black holes are spinning black holes.

[@davidfordyoyoguy]

Not to mention the orbital mechanics that change everything in this scenario, yet rarely gets brought up. Average people usually picture themselves in a spacesuit floating in one place just outside of the event horizon and tossing a ball into it. If you were to get anywhere near the EH, you are cruising at ridiculous speeds! Now you have THAT time dilation to deal with as well! I want videos talking more about this.

[@narfwhals7843]

Something I never see mentioned with the redshift is that to resolve an objects location you need a certain maximum wavelength. So as you see it redshifted you eventually also lose information about where it is. This means the object is invisible and smeared across the entire black holes event horizon. So it effectively has become part of the black hole. It has "fallen in", as it were.

[@pompeymonkey3271]

Until the last quanta of information. Yeah. Elegant. :)

[@narfwhals7843]

@@greggoog7559 I do, thank you.

[@nmarbletoe8210]

In a related vein, I have heard that a photon with a wavelength larger than the hole's diameter can't fall in, it could be scattered but it would keep going past the hole.

[@themcchuck8400]

Informative and entertaining as usual. Much appreciated. The fundamentals: 1. The total energy at every point is a constant. (Planck energy) 2. There is no such thing as negative (anti) energy. (This has nothing to do with opposite types or directions.) 3. Spacetime is a field of potential energy governing motion. (Motion is a standing wave.) 4. Space is Euclidean. Spacetime is hyperbolic. (Time has an imaginary component to make it 90 degrees off everything else.) Everything else follows. There are no contradictions. There are no infinities. There are no singularities.

[@ffggddss]

Nice explanation, including some stuff not ordinarily mentioned or acknowledged. I do have one small quibble, however. When that blinking light is falling in, the outside observer will not see the blink-period increase to a million years, then to more than the age of the universe, etc. Well, at least, that's not quite an accurate description. Because in its own instantaneous rest frame, the light continues to blink 1ce/sec, and the time it experiences to the Event Horizon (EH) is finite; thus the number of blinks it emits before reaching the EH is finite, and there will be a last blink seen by any observer outside the EH. In that sense, I suppose you could say that the "next" blink will take longer than the age of the universe, but that's really just because there will *be* no next blink. As seen from outside, that is. Make that two quibbles. When a finitesimal-size object is in a Schwarzschild metric gravitational field, yes, there is a "stretching force" in the radial direction. But just as important, there are "compression forces" in the two azimuthal directions, due to the change of direction of the traditional gravitational force, with sideways displacement. These are in fact, each just half the magnitude of the radial stretching force, so that the 3 "forces" sum to 0. [More technically, for a freely-falling body, the tidal gravitational stress tensor is traceless. As a spatial transformation, it is volume-preserving.] This fact effectively doubles the deformation ("spaghettification") of the falling object. Fred

[@glennstasse5698]

Always something good in these videos even if sometimes I’m lost. Not this time, though. The box and the lines representing gravity was brilliant!

[@SiqueScarface]

Fascinating is also the idea, that a black hole large enough can have a gravitational potential at the event horizon which is just about the same size than that of Earth, 9.81 kg*m/s². It would be huge (10^48 kg or 10^18 times the mass of the Sun, which is 1 million times the mass of even the largest galaxies), but still within the realm of the possible. In theory, you could build a Dyson sphere just above the event horizon and walk on it as you would walk on Earth.

[@kylebowles9820]

Always fun to think about the similarities and differences between this and the CMB

[@ebenolivier2762]

I'm struggling to think of a difference. The CMB is essentially identical to the whole universe falling into a black hole outside of it.

[@ArawnOfAnnwn]

@@ebenolivier2762 PBS Spacetime has an episode on that!

[@davidpraesent]

Two questions concerning a feet first straight fall into a black hole after passing the event horizon: 1. Would you see a flashlight mounted on your feet? 2. Would your nerves function properly? Would you be able to register pain in your feet?

[@narfwhals7843]

For a large enough black hole, yes. You would see the flashlight and your nerves function just fine. The event horizon is not a special place at all for a person crossing it.

[@ThomasJr]

What this means is that the gravitational acceleration g of 9.8m/s^2 near the surface of the Earth is just simplification. The g is a function that is not constant. But for most purposes that assumption is good, as the real g is a function of the altitude.

[@Mysoi123]

That’s absolutely correct.

[@bob456fk6]

Thanks for the very good explanation using the blinking white light. 🙂

[@NomenNescio99]

Please do a video about spooky action at a distance and hidden variables explaining this year's Nobel prize in physics.

[@rickymcriver]

Black hole series please 😀

[@brothermine2292]

One additional point about spaghettification with a supermassive black hole: the spaghettification will occur later, after passing inside the event horizon (assuming the mass of the black hole is concentrated at its center).

[@drdon5205]

True, but unseen.

[@brothermine2292]

@@drdon5205 : Unseen by observers OUTSIDE the event horizon. Someone who falls into a supermassive black hole would eventually see himself torn apart, if he doesn't fall unconscious first due to the agony.

[@ArawnOfAnnwn]

@@brothermine2292 You'd have likely already been burnt to death by then anyway, from all the stuff swirling around in there. But in case you weren't (and didn't die of starvation or just anoxia), you still likely won't be spaghettified in your lifetime, instead just swirling around the center for eons before finally falling into it.

[@kitmoore9969]

@@drdon5205 Sorry, but this is still bugging me ... and I don't know how to explain why :( Be kind ... The video talks about the concentration of radial lines as the "total amount of gravity", which is another way of saying the effective force of that gravity? As you get closer, the lines tighten up and gravity increases? I'm not smart enough to know the numbers, but there's a force at the event horizon which can prevent light escaping (call it x joules) and another force which can spaghettify a human (y joules). The claim is that, for a supermassive black hole, spaghettification occurs later, inside the event horizon. Since the force of gravity increases as we go in, y must be greater than x. But there's an implication that a smaller black hole causes spaghettification to occur earlier, relative to the event horizon where force=x. We could say that it occurs outside the event horizon, where y is less than x. In other words, either y, x or both vary with the radius of the event horizon? How does the radius come into the calculation? It's already intrinsic to x, and it's irrelevant to y.

[@JustinMShaw]

@@kitmoore9969 It might help you to consider another force - that required to rip the falling object apart. The difference emerges in exactly where in the space around the black hole will experience that force over an area of the size of the falling object.

[@donald-parker]

Here is a black hole topic I would be interested in seeing you cover: Nested black holes. I first started thinking of it when seeing some theories about the universe is a black hole (which seem pretty dodgy), but it does not seem to far fetched to imagine a stellar mass black hole merging (falling into or passing through the event horizon) of a galactic core super massive black hole and retaining its identity as a stellar mass black hole for some time. But then I got thinking about how density of matter and energy changes as it approaches the singularity and I was wondering if it becomes so extreme that it could form black holes even before reaching the singularity. So now I have this crazy mental image of a whole sea of blackholes swarming around each other near the supposed singularity. And then what ...

[@TheDanEdwards]

"time slows down" - I'm with Sean Carroll in not liking that phrase. Time does not slow down. Instead what an observer is experiencing is simply that the blinking light is in a different reference frame. The light is still experiencing the emission of light every second (according to its own clock.)

[@johngrey5806]

If I knew this info when I was in school, I would've raised the classroom clock higher. At least a foot!

[@azurlake]

I love Dr. Don videos, and I regularlo watch these shows like PBS Spacetime, the Wonderful Person guy, Dr. Becky... but don't get me wrong, but at the risk of sounding impertinent I have to say some science topics seem to be stuck at the edge of a black hole if you know what I mean. More and more I'm starting to think like Sabine Hossenfelder and started wondering where should we put our collective efforts in order to get past that point, but in the eyes of the rest of the universe.

[@lightdark00]

Should I watch this? If it turns out what I saw on the show Andromeda wasn't true I don't think I could cope. 😳

[@MarceloSaturn]

For an external observer, the falling object would *never* really cross the event horizon, but what if we take Hawking Radiation into consideration? Even if it takes aeons to begin, the Schwarzchild radius will decrease over time, making the boundary ever smaller, until it no longer exists. I've never seen anyone address the implications of that. What does that mean in the reference frame of the falling object? To be consistent, they should also see the event horizon shrinking as they fall, never touching it, until it has evaporated completely. After an unimaginable amount of time for the outside observer, the object (and by extension everything that ever fell on the black hole) should be free to escape.

[@juliavixen176]

Yeah, I’ve considered the black hole just evaporating out from underneath you as you fall in scenario... So... Hawking radiation and the Unruh effect are basically two different ways of talking about the same thing... the thermal radiation appears just outside of event horizon (the edge of the hole in the quantum vacuum), and the temperature of the blackbody is proportional to surface area of the volume of spacetime the event horizon encompasses. Smaller black hole means hotter (higher energy) radiation... (a larger black hole is colder, barely emitting radio waves)... So, just as a practical thing, when the black hole is really really small, it will be putting out a lot of hard gamma rays. Also... most of what is falling into a black hole is the core of the collapsing star (neutron star) which formed it... that’s “falling down forever” too... like the supernova never completely stopped, and it’s just happening in extreme slow motion over billions of years... I’d imagine that if you filmed a black hole for billions of years, and then sped the movie up by trillions of times, it would probably look a lot like the star it was originally made out of... ... and it might look like that again as you fall in and “catch up” with it.

[@juliavixen176]

I lost my train of thought, as I was saying... the Hawking/Unruh radiation is only seen by accelerating observers. If you are in free-fall, you are not accelerating, so you won’t see Hawking radiation. Also, if you’re in free-fall, I don’t think you can catch up with anything that “fell in” ahead of you. And anything falling in behind you will never catch up with you... (As long as you never accelerate.) The curvature really grows asymptotically, it’s ln(r), as r goes to zero. That’s pure GR without any QM stuff... because there isn’t really a good theory yet of whether or not some QM thing happens before that curve can get all the way to infinity.

[@MarceloSaturn]

​@@juliavixen176 I see. I'm not considering what effects the radiation might cause on the object (and not even spaghettification), just the shrinking effect itself, which *must* happen in some way to all observers. My idea is that if for an outside observer it takes infinite time for something to truly cross the event horizon, and the black hole evaporates in finite time (making the event horizon disappear), then all things will escape at the end, perhaps even preserving their properties (if they are subatomic particles), except possibly the matter that first formed the black hole, since it will be converted into radiation.

[@jimmyzhao2673]

I read somewhere that you can avoid Spaghettification by tucking and rolling.

[@TheOtherSteel]

1 - Gravity can escape a black hole. 2 - If you fall into a black hole, and could modulate outgoing gravity waves, you could send out a communication. 3 - This suggests that there is no way to manipulate gravity waves, and thus no way to generate gravity artificially (beyond accumulating or dispersing matter in large quantities , which you wouldn't be doing from inside the black hole).

[@narfwhals7843]

Your first statement is false. Gravity does not escape the black hole. The black hole is a feature of the gravity in the region. Spacetime curvature is sourced by the stress energy tensor. You can only manipulate gravity by manipulating the stress energy in a region. That basically means for large effects you have to move large masses.

[@tfhmobil]

You explain photons as 2 dimensional in a other vlog. It’s obvious that because photons can’t escape a black hole, the inside of a black hole is single dimensional. It’s not “flat” like a photon, it’s simply single dimensional. That said, you provide some of the best vlogs on physics 👍 Very enjoyable 👍

[@paul_gradenwitz]

This is a well known description. Let something fall in a straight line into the BH. But what happens if we let the object fall to the BH and MISS?. That is when the object makes at least one half orbit around the BH and comes out to a distance so that we can see it again? It will not fall in an elliptic orbit. It will not fall in a parabolic orbit. But it will fall in some curve that has a closest distance to the BH. Now take the known effect of the Shapiro Delay. This is described with curvature of space. But we can project that into flat space and see that light takes longer to traverse a trajectory if that trajectory comes close to a gravitating mass. The same happens with matter. It also slows down wen its trajectory comes close to a gravitating mass. This explains the Mercury orbit. The light that grazes in its trajectory the event horizon will be slowed down so much that it never emerges from that path. In the projection of curved spacetime onto flat space the light appears to have stopped. The effective speed of light as projected to flat space has halted. That means that, because an object that comes close to the Event Horizon always has to obey that it can't move faster that light, the object thus also has to slow down and stop at the event horizon. If it remains at some distance from the BH so that it orbit allows it to emerge out of the BH, then its delay will prove that it had to slow down and not accelerate. So, any object falling towards a BH comes at rest at the surface and never enters below that. Try to prove me wrong without violating GR.

[@randalljsilva]

I really don’t think an outside observer would see the blinking object stop at the event horizon. In all the CGI simulations of black holes, they always show the accretion disk spiraling around and the astronaut stick to the horizon like a fly on fly paper. The particles themselves don’t stop-it’s the speed of particle interactions (EM and Weak and Strong force bosons) that are slowed immensely.

[@zakirhussain-js9ku]

Two Observers on opposite sides of light emitting object, one closer to black hole other away from black hole will measure different light frequency due to doppler & gravitational shift. While object is emitting single frequency. Observer on closer side of black hole will measure blue shifted frequency due to doppler & gravitational blue shift while observer away from black hole will measure frequency resulting from combined effect of doppler red shift and gravitational blue shift. Since both Observers are measuring frequency other than object's frequency, measurement involving Observer can't be relied upon. I think extream gravity of black hole will split object's atoms into mass, electric & magnetic charge. Gravity will pull mass which will be absorbed by black hole while electric charges will initially circle equatorial region and magnetic charges spiral towards polar regions of black hole but eventually drift into & absorbed by surrounding space.

[@Bit-while_going]

Never get into a staring contest with a black hole: they never blink.

[@hiriamlackey9189]

As an observer, If you are falling into a super massive black hole but looking up what do you observe? If an outside observer see's you slowing down, and red shifting until you fad away, does the observer see the universe age out of existence, until the light being blue shifted into gamma radiation rips you apart molecule by molecule?

[@drdon5205]

Yeah, pretty much.

[@bsadewitz]

Once you pass the event horizon, you can't just hover there. You MUST fall ever inward. So I don't know if this blue shift thing would actually happen.

[@a.lewisraymer7772]

Yay! Another video from Dr. Don!

[@Sd-bi7ey]

It's a treat to watch your videos sir...A fan from India..

[@c.ladimore1237]

worth noting that a lot of ppl will be thinking that because an object seems to "freeze" forever at the edge that the black hole would look like it is covered in things like asteroids, planets, or the wayward astronaut b/c they forget about the red shifting and that it is the photons emitted or bouncing from those objects that make them visible. so as soon as those photons go to infrared or radio, any observer, no matter how close, would see them vanish, not get "stuck" on the edge like a car pile-up

[@Activan1]

a large black hole will only allow you to get a lifetime experience of passing through the event horizon. closer to the center of a large black hole, the lines of force of the gravitational field will converge in the same way as was shown for a small black hole, and the difference in attraction will tear you apart. and so on to quark plasma and then turn into something that I do not know.

[@jzahoraiii4425]

Falling "in" is a misnomer; Boltzmann's entropy shows that each unit of information added to a "black hole" increases the circumference by 1 Planck length unit.

[@Jopie65]

Suppose falling Bob takes a light clock (light bouncing between mirrors) with him and stationary observer Alice looks at Bobs clock which starts ticking slower. Because light moves at the same speed for all observers it means that for Alice the clock gets bigger, because it takes longer for the light to bounce between the mirrors while the speed of light remains the same. That means Bob gets bigger and bigger until he wraps around the horizon and will basically be smeared out over the BH surface. Now seen from Bob the clock keeps ticking at the same speed but is now nearing the BH . Hence his clock remains the same size. So that means that the BH seen from him must get smaller and smaller until it becomes an infinitesimal small point to which he wraps around: the singularity. Conclusion: the event horizon = the singularity. It's just from which point of view you're looking at it.

[@thedeemon]

Nice try but no. In GR light moves at same speed *locally*. Light far away from you may move at other speeds, as measured in your frame of reference. Alice would "see" that light in Bob's clocks actually moves slower than c. See en.wikipedia.org/wiki/Shapiro_time_delay

[@Jopie65]

@@thedeemon Ah, shapiro time delay. I didn't know about that phenomenon... Thnx!!

[@CyberwizardProductions]

it's still blinking at the rate of 1 time per second - the observer is experiencing lag - it just looks like it's blinking slower - it's not that it isnt' blinking slower and it's NOT that time is moving differently - it's all observational lag in the case of the light. And probably everything else.

[@joseraulcapablanca8564]

Thanks Doctor Lincoln, informative,entertaining and concise as ever.

[@fernweh3726]

It would be great to have some videos taking into account the quantum effects and the thermodynamic of black holes.

[@shawn0fitz]

You mean like Hawking radiation?

[@fernweh3726]

@@shawn0fitz That's part of it

[@justinreschke3642]

Why is it that a distant observer sees an object become frozen in time when falling into a black hole, but we have no problem observing black hole collisions. Shouldn't they be frozen in time right before the moment of collision?

[@Pkshah420]

Hey man....you are doing a great job Atleast for me

[@mohitsoni3275]

Spaghettification makes you look thinner, which eating Spaghetti doesn't.. 😁😜

[@ronaldkemp3952]

Please, do a video on galaxy's high velocity dispersion rate. Explain why our solar system is moving away from the black hole at a high velocity, 900,000 mi/h instead of towards it like the cosmological model predicts.

[@francissreckofabian01]

If you don't get ripped apart what happens? In Frederik Pohl's Hugo winner Gateway novel some people get stuck on the event horizon. Not going in but unable to get out. So, according to Wiki: Due to the gravitational time dilation of the black hole's immense gravity field, time is passing much more slowly for his former crewmates and none of them have actually died yet. The protagonist, however, concludes that this means that they will still be alive when he dies, - Is this "true" If time slows does their metabolism slow? What about air and food? Will they be stuck there, alive until sometime in the future when/if the black hole evaporates? This may, of course, be bad physics but I only have high school science. Thanks.

[@thedeemon]

Yes, if they hover above the horizon time should pass really slow for them compared to far away observers. They would feel normally, but each day for them is like many days / months for those far away. All processes "slow down", comparatively. But they will feel enormous gravity force, they'll need to use engines all the time in order not to fall in. It's impossible to orbit in free fall near the horizon, the closest stable orbit is 1.5 times the BH radius, where time is only about 30% slower.

[@katimartidonoghue]

Best story ever ❤

[@CoraxCatcher]

Love Dr. Lincoln’s videos! Question: Since fundamental particles are energy excitations in Quantum Fields, then isn’t it the Quantum Fields that are collapsing into black holes? I don’t think I’ve heard black holes discussed from this perspective. I guess Quantum Gravity is hard to explain to general audiences. Where could we find more on that?

[@dugldoo]

Dr. Don, with GW190521 two black holes of 85 and 66 solar masses collided and produced a BH of 142 SM. Energy equal to 9 solar masses radiated away as gravitational waves. But we're told that all the mass of a BH is concentrated in its central singularity and nothing can leave a BH. So something is amiss. Where did the 9 solar masses of gravitational wave energy come from?

[@tresajessygeorge210]

THANK YOU... PROFESSOR LINCOLN...!!!

[@peterdamen2161]

I really like the videos of Don Linclon. Including his sometimes somewhat nerdy humor. But in this video I have to set the record straight! At the beginning of the video, around 1:20 min, Lincoln criticizes the answers seen in books and videos. Unfortunately, he is also wrong in stating that an object approaching a black hole becomes seemingly frozen in time (around 4:35 min). That is simply not true. Matter does not become suspended forever, just outside the event horizon of a black hole. As that it is not true that time comes to a standstill at the event horizon. Look e.g. at the article by Pounds et al. (An ultrafast inflow in the luminous Seyfert PG1211+143. Mon Not R Astron Soc (2018) 481, 1832-8). In it they describe that an object falls into a black hole. "We were able to follow an Earth-sized clump of matter for about a day, as it was pulled towards the black hole, accelerating to a third of the velocity of light before being swallowed up by the hole". Apparently, Lincoln has to redo his homework......

[@drdon5205]

As it neared the event horizon, time slowed down and it faded from visible to infrared to radio waves. They lost sight of it, but that says something about the wavelength they could image.

[@peterdamen2161]

@@drdon5205 Check the paper I referred to..... In addition, Einstein was a bit wrong. I'll explain that in a couple of months......

[@drdon5205]

@@peterdamen2161 The paper you mentioned talks about the strongly red-shifted inflow, which is consistent with the claims of the video. The paper is more about the dynamics of accretion disks and how they interact in a scenario where the orbital plan and spin axis of the black hole are not aligned.

[@peterdamen2161]

@@drdon5205 Hi Don, thanks for your quick reply! And the strongly red-shifted inflow, as described in the paper, is indeed consistent with the claims of the video. I didn't question that. However, the inflow of matter at v ∼ 0.3c is not in my view. And that is what I was referring to. In addition, like I already said, I'll explain it much more thoroughly in a couple of months. Just be patient 🙂

[@youstandcorrected]

I am sure Event Horizons would be good spots for any Alien Predecessors to place "eternal post cards". We should start looking.

[@fps079]

Ok, Dr Don, I think I get the dependence of acceleration of the points of the observer as they relate to the singularity, but would not spaghettification occur for a large black hole as one approaches the singularity whether the person is inside or outside the event horizon? Within the event horizon things should be the same as outside the event horizon. Spaghettification depends on the difference in acceleration between points of your head and feet., which for a large black hole, would still occur. Or is there something about passing the event horizon I do not understand?

[@drdon5205]

Spaghettification would occur inside the event horizon, but someone observing the event would never see it fall through the horizon. Answering the question depends greatly on the observer asking the question.

[@gertboltenmaizonave2421]

I understand that nobody knows what happens inside the event horizon, without a theory of quantum gravity.

[@kitmoore9969]

He seems to be arguing that the singularity in a supermassive black hole has an enormous radius compared to one inside a stellar-mass BH?

[@drdon5205]

@@kitmoore9969 Not the singularity - the event horizon.

[@fps079]

@@drdon5205 I was thinking of the object experiencing the Spagettification. Thank you for the help.

[@sohelranashaikh8032]

Great lecture

[@JdeBP]

If you are going to think about real non-point-size objects, you are also going to think about tides. Very few popular explanations of black hole cosmology remember that real macrocosmic objects, as opposed to thought experiment point masses, travel in orbits and experience tides.

[@narfwhals7843]

Spaghettification is a tidal effect.

[@sethapex9670]

Doesn't the person falling into the black hole see the light from the outside world get blue shifted as it falls into the black hole such that they would essentially get cooked with gamma rays before they pass the event horizon.

[@drdon5205]

Partially true - the blue shifting. But the time changing has other consequences. As I said in this video, I didn't talk about that facet of falling into a black hole.

[@leomuzzitube]

If it takes an unimaginable amount of time for us distant observers to see things falling into the black holes, how can we detect black holes merging with other objects through gravitational waves?

[@c.ladimore1237]

gravity moves at the speed of light, so while light can't get out of black holes, gravitational waves generated by them merging do. well not from inside, but from the immediate merges/passes

[@leomuzzitube]

@@c.ladimore1237 that is not the point, although this is also interesting to discuss. But the point I was making is: the "merges" should never happen if objects are frozen forever at the event horizon from our perspective.

[@drdon5205]

@@leomuzzitube The shaking of spacetime doesn't only occur at the event horizon. It's the shaking of space originating at larger distances that speeds across the cosmos.

[@c.ladimore1237]

@@leomuzzitube they aren't frozen. they go into it just fine. the light from smaller things just turns into radio waves, which are invisible, so it looks like they vanish, not freeze, before merging. more massive things like other black holes create gravitational waves, which, being outside the event horizon and moving at the speed of light, are detectable.

[@leomuzzitube]

@@drdon5205 thanks, that makes sense. But don't we see the moment when the gravitational waves from a merge event stop, and interpret that as the two masses becoming one?

[@trescatorce9497]

correct me if i am wrong= acceleration equals distance/the square of time. On a close approach to a black hole, time goes to infinity, hence acceleration goes to zero. Space or distance gets warped by the gravitational field, which would deflect the falling object tangential to the field, so the stretching is around the horizon, not into it

[@thedeemon]

if the BH is not rotating there is nothing to deflect it tangentially. Pure radial motion. And since one part of the object is trying to accelerate faster than the other, it breaks apart at some point.

[@drGigg]

Isn't there a high energy barrier as well, like a firewall of photons?

[@TheMateusz28]

Dr Don, thank you for great video! I wonder, from our perspective objects are getting frozen in time when they fall into black hole. In that case how old a black hole is from black hole perspective? Aren't they very young?

[@Dragrath1]

In principal yes with time dilation it's likely that a black hole from the perspective just at the horizon (as we can't say anything about the interior) likely is more of a moment or se of moments in time. Factoring in Hawking radiation and the local reference frames close to the black hole, a black hole quite probably isn't much more than an extremely time dilated explosion.

[@Grey_Area570]

Do we know the temperature of a black hole? and if we could measure it, would it be close to absolute zero? Just thinking about density of matter and the ability to move being somewhat constrained.

[@dmitrikourennyi6093]

Would it be correct to conclude that spaghettification happens from the point of view of the falling object, but pancakification (flattening) should happen from the point of view of a stationary observer? The bottom of the object will experience slower time and eventually will "stop", while the top would still be falling in.

[@ryann1669]

I have a feeling that if you were falling into a black hole with hawking radiation and were not torn apart, you would never enter the black hole. Time for you would slow down relative to earth so they would never see you enter. but for yourself, time would be going at a normal rate. This differential tells what would happen to the faller. Specifically: as they get closer to the event horizon they would witness the evaporation of the black hole before ever actually getting inside. Because time on earth (or some other spot outside the influence of the black hole) the faller would appear to be falling slower, their brain chemicals would also appear to be reacting slower and by the same amount as the slowing fall. From the faller's side, they would not notice any slow down but would notice a speed up of things not inside the influence of the black hole. Things on earth would look much faster including the chemical reactions in brains of people on earth. So, time would slow down (or speed up depending on your perspective) such that FROM BOTH SIDES the faller never actually falls into the black hole. The faller ends up witnessing the death of the black hole.

[@thedeemon]

No, that's not how time dilation works in GR. If we see the traveler slowed down it doesn't mean they see us accelerated. Both of us actually see each other slowed down. For the falling observer they are in an inertial frame of reference and you accelerate away, getting time dilated. See these materials, especially lectures 6 and 7: kzbin.info/aero/PLpGHT1n4-mAvcXwzOIz3dHnGZaQP1LEib

[@stephenbrickwood1602]

Love your work

[@Khannea]

Tell me how much the blueshift of the surrounding universe, stars, CMBR, cosmic rays, etc etc would be TO the object falling into a SMBH, and whether or not such an attractive experimental subject would in effect being vaporized ? Also tell me how much the Hawkin Radiation would go up exponentially (from your subjective position) as you approach the event horizon ? Also tell me how much the time dillation of you falling in to the black hole would in effect mean that relative to the rest of the universe you'd arive in infinite years to the singularity? Explain to me what the literal theological consequences would be of being in a suspended state there? When falling into a black hole does god of christianity actually at some point intervene and come save your soul if you have been a saintly christian, or is the power of the almighty effectively unable to enter and consequently leave the gravity well of the black hole?

[@jkinkamo]

BH can radiate gravitational field lines from behind the event horizon? How about electrically charged BH's, do they radiate electric field lines from behind the event horizon? Or are these field lines generated just at the surface of the event horizon?

[@anoopcjose78]

Thank you for the wonderful presentation. I am a great fan of yours. Your video about the edge of the observable universe was a real Eye opener for me. I have a doubt about the content of this video. As per my understanding, a freely falling object is in an inertial reference frame. Assume that a Freely falling clock starts to fall from infinity to a black hole. Before starting to fall, its time is synced to another clock located at infinity. Now, as the falling clock gets closer and closer to the black hole, it passes by various clocks at various distances from the black hole. All those clocks are stationary with respect to the black hole and situated at various strengths of the gravitational field of the black hole. This means none of them is in inertial reference frames. The closer they are to the black hole slower they are with respect to the clock at infinity. Now the falling clock is in an inertial reference frame all along. My doubt is, when the falling clock passes by each of those stationary clocks, will there be any time dilation between those clocks and the falling clock? if yes, then will there be any time dilation between the falling clock and the clock @ infinity. Because they were initially synced, and both of them were in inertial reference frames all along.

[@drdon5205]

As the clock falls, it changes reference frames. The stationary clocks are in accelerating reference frames, each different from one another, although stationary in one frame. However, the moving clock changes to a number of different frames. Relativity takes a while to internalize. It's easy to make assumptions that you don't realize.

[@drdon5205]

Actually, GR describes the state of all frames, inertial or otherwise. Hence the "general."

[@RodneyAllanPoe]

Terrific video. Can you explain how matter collapses to form a black hole and into a singularity? PBS Space Time covered this, but Matt only said the momenta of particles became huge, allowing particles to share the same points in space, eventually creating a singularity. A whole episode about this phenomenon would be great. 🔎

[@shawn0fitz]

A black hole doesn't require a singularity. Singularities are predicted by General Relativity, but black holes can just be really massive objects smaller than their event horizon (or Schwarzschild radius).

[@RodneyAllanPoe]

@@shawn0fitz OK then. But nobody ever mentions the possibility that one could cross the event horizon and get splattered onto the surface of something like a neutron star. It's always about the "singularity, a point of infinite density". 🤔

[@juliavixen176]

@@RodneyAllanPoe To simplify things... back in the days before we had electronic computers... “vacuum” solutions to Einstein’s field equations were used... so, a black holes would be eternal, always existing as a curved region of spacetime, just... because... So, real black holes aren’t like that, because they are created by the collapse of massive stars, or neuron star collisions, or whatever... so there should be “stuff” inside... *but*! Degenerate neutron matter is held up by... basically two neutrons not being able to be in the same place at the same time. (Same thing with protons and electrons in a white dwarf.) inside a black hole... spacetime is going to try to make those neutrons be in the same place at the same time... and the question is, who will win? Gravity or neutron degeneracy pressure? If gravity wins you’ll get a singularity...

[@cptechno]

QUESTION ABOUT BLACK WHOLES: Why some blackholes have two fast particle jets coming out of two opposing poles? Why doesn't the law of gravity apply to these two jets? Are these two jets coming from the inside of the event-horizon or from the region outside of the event-horizon?

[@narfwhals7843]

The jets aren't coming from the black holes themselves. They are created by the accretion disk and its magnetic field causing high energy particles to spin towards the poles and out from there. The laws of gravity absolutely apply.

[@pointer2null]

It's crazy to think you could send a probe into Sagittarius A*, and it could survive for a while (but never be able to send anything back).

[@LinkenCV]

Question: What happens with changing of wave function which obbeys Dirac`s equation? Because the deal is that inside black hall time and space "flip each other" and from anavitable future(time direction), you get anavitable singularity(space direction) Mindblowing for me was theory: object that falls to black hall immediately evaporates at horizon, and we see remnants of this event and events before that(up to collapsing of the star) billions years after because time almost stops at horizon. And maybe its a Hawking radiation

[@johneonas6628]

Thank you for the video.

[@thebanksfamily1564gig]

Great information..

[@FlyboyMillar]

It's been determined and proved that time slows as gravity increases. That said, the distance between celestial objects is measured in light years. ( a measurement of time ) If time is faster in deepest space, is it possible the size of the universe is very different than what we perceive due to time dilation?

[@sohelranashaikh8032]

Great teacher

[@fslurrehman]

It's very scary that black hole takes a sort of black and white picture of every object it has eaten and then it decorates the album around itself. 🥶

[@oldjoec3710]

Dr. Don - There's puzzling contradiction in this description that I can't sort out. At 2:27, "the object heads toward the center of the black hole; nothing changes as it passes the event horizon". At 4:18, (it takes, in an external view) "eventually longer than the lifetime of the universe" to pass through. However, we understand that the black hole will evaporate away due to Hawking radiation (in the same external view) BEFORE the end of the universe. So, two questions: (1) Wouldn't the object see itself as riding down though this radiation zone, rather than falling normally? (2) Wouldn't the release of the entire mass of the black hole as Hawking radiation over the short subjective time of the descent make this an extremely intense (and destructive) experience for the falling object? 🤔

[@thedeemon]

In the falling object's POV only short time passes and there is no "time compression", it won't see the BH evaporate, in that 30 minutes of fall it will see about 30 minutes of BH evolution - nothing spectacular. However light from the falling object will take a lot of time to reach outside observers, so outside observer will "see" the object slowed down, this is just an "optical illusion" in a sense. If the outside observer starts chasing the fallen object, it will discover the object is long gone, it's not hanging there at all. Even light is not able to chase that object after some point. So light from later events will not be seen by the falling object.

[@dontwanttousemyrealnametol6765]

Answers always avoid a more detailed "graphic" explanation of what happens to a human body traveling at certain speeds in a vacuum towards a black hole, given certain starting conditions like orientation an distance to the black hole, the amount of gasses and cavities of air in the body, the temperature distribution over time, surface heat, etc... I'd like to know how what happens in vivo, and at which point a live human is most likely to die, so which other vital organs fail by inflation even if air could escape from the lungs, and if the human would likely be conscious by the time gravity effects on blood flow, organs and tissue enough to cause trouble.

[@saimon174666]

When you are nearby black hole and look "up" to the ship that dropped you there - does it look like the time passes faster for them? If the light from you gets redshifted when looked from outside, does the light from outside get blueshifted for you? Wouldn't that kill you very quickly as light would become gamma rays?

[@Bob-of-Zoid]

I like watching my legs spaghettify!🤓 It's when I do a silly dance to enhance the effect!🕺

[@Jim-uq1mc]

*** Paradox *** The different experiences of Alice watching Bob falling into the black hole leads to some irritating paradox. Alice never sees Bob crossing the event horizon even if she watches infinitely long, but Bob in his own experience does cross the event horizon and falls right towards the center of the black hole. Now, what if the black hole evaporates within finite time and Bob sort of becomes part of our universe again. In principle he then might tell Alice what he experienced after he crossed the event horizon. How would you reconcile this paradox?

[@juliavixen176]

The statements: “sort of becomes part of the universe again” and “tell what he experienced”, is doing a lot of work... There won’t be a discontinuity... Bob never left this universe, and never stopped communicating with us... his communication (emitted light) was just delayed by a few billion years, but when it catches back up with us, he’ll be outside of the event horizon. (Arguably, from Bob’s perspective, he never actually crosses the event horizon either. The event horizon is not actually a “thing” and it’s location depends on the location of the observer.)

[@Metaldetectiontubeworldwide]

Obey gravity , Don.. We wanted to see Don's Spaghetti? ...lol Well done ☆☆☆☆☆

[@sapelesteve]

Another fantastic video in this Black Hole series Dr. Don! Now I am wondering if vastly different sizes of BH's have significantly different gravitational forces at their centers? 🤔🤔🤔🤔

[@docteurslump5517]

What is never described in explanatory BH videos is that a falling observer sees the outside universe aging super fast to the end of times, before crossing the event horizon. Unfortunately it's also the case here

[@narfwhals7843]

That is described all the time and it is _wrong_ . The falling observer sees the outside world slow down as well due to reshifting. An observer who tried to hover above the event horizon would see the outside world speed up, because they have to accelerate. Check out this video by ScienceClick where they explain why this is a misconception kzbin.info/www/bejne/aqO3p2ytq9uUqpo

[@docteurslump5517]

@@narfwhals7843 thanks, will watch this with interest

[@Valdagast]

The black hole's Yelp reviews are saved by the fact that no one who fell in can leave a review outside the hole.

[@ericmelton4186]

Your diagram of a black hole looks like magnetic field lines. And spaghetti afacation looks like nothing more than tidal forces. Love your show never stop you allow me to think outside the box

[@thedeemon]

but spaghettification is indeed caused by tidal forces!

[@ericmelton4186]

@@thedeemon kool. I’m learning

[@thepooz7205]

You still get spaghettified in the example of the super massive black hole, just not outside of the event horizon to be visibly spaghettified to an outside observer.

[@farben_]

I'm more interested in what happens inside a black hole, although that one I don't think we'll ever know.

[@TunaFreeDolphinMeat]

The galaxies further away from us accelerating away at a greater speed could be a type of flying spaghettification indicating we are in a black hole

[@prabha5148]

No, as the universe expands the gaps between also expand and thus galaxies appear to go farther and isn't spaghettification.This also explains some galaxies appearing more reddish day by day.

[@juliavixen176]

Technically yes, but no. The field equations are the exact same equations for all of this... because the entire universe is just one whole gravitational field. In some places space is shrinking (called “gravity”), and in others it’s stretching very slightly, which makes distant objects appear to be moving away from us. Things which are not accelerating are, essentially standing still, and this gravity stuff is just the spacetime changing shape around them.

[@ericmelton4186]

I have been watching professor susskind at Stanford explain cosmology. He is awesome!👍 lecture ten will blow your mind on several levels

[@curiodyssey3867]

Dr don you are such a baller

[@drdon5205]

😁

[@phil.1]

Any fun theories that connects a black hole to dark energy? Like if spacetime fabric gets sucks into a black hole, it stretches the current entire universe’s fabric apart showing up as expanding universe 😂

[@juliavixen176]

It’s all one single “spacetime fabric”. The equation for dark energy and gravity are the exact same equation... and it doesn’t “suck”.

[@billgaudette5524]

Does an object falling into a black hole fall -with- space, or through it? My thoughts always come back to whether something could still live once past the event horizon. If nothing can escape a black hole, and space and time switch places inside (as in, all timelines end at the singularity), how would it be possible for anything to move in any direction away from the singularity while inside the event horizon? No waving arms, no thoughts, no nerve signals could occur, as no ions could be transported across a nerve ending farther away from the singularity. Unless, space itself is falling into the singularity and everything that moves with it has certain degrees of freedom relatively. Thoughts that keep me up at night!

[@Activan1]

together. the speed of free fall is. For a black hole beyond the event horizon, the speed of free fall is equal to the speed of light. just to stay in place and not continue falling, you need to fly at the speed of light directly from the singularity. though this may all be nonsense. we do not know the nature of even the magnetic field.

[@kitmoore9969]

You can't escape a black hole. That's why they are black. Everything falls onto, and becomes part of, the singularity: enormous mass, zero size.

[@ronaldkemp3952]

Why didn't the G-02 gas cloud become spaghettified when it got close to the supermassive black hole in the core of our galaxy? Surely the gravity if it is as powerful as predicted by general relativity should have cause the gas to be stretched out of proportion and even cause some of the gas to be pulled into the event horizon. According to the laws of motion the gas cloud didn't have enough mass to produce angular momentum. So it should not have escaped it's gravity unscaved. But the gas cloud came out from behind the black hole and retained its spherical shape. Astrophysicists predicted in 2010 the G-02 gas cloud would be spaghettified but it wasn't. Because the gas cloud didn't fall in or become spaghettified in 2014 they postulated that maybe there was a few stars hiding in the gas. They went over the infrared telescope data on Sgr A* and could not see any stars hidden in the gas. They couldn't explain why the massive gas cloud was barely affected by the gravity of the black hole. If special relativity is correct then why doesn't time dilation occur to the S-type objects orbiting close to the black hole Sgr A*? S-02 orbits the black hole extremely close and shows no sign of time dilation happening to it. Instead of time slowing down the star appears to accelerate as it approaches the black hole.