White Holes | Space Time

White Holes | Space Time


This episode is supported by LegalZoom. Lurking in the depths of the mathematics of Einstein’s general relativity is an object even stranger than the mysterious black hole. In fact, it’s the black hole’s mirror twin: the white hole. Some even think that these could be the origin of our universe. The astrophysical phenomenon of the black hole has captured the imagination of scientist and science enthusiast alike for many decades. When the idea first emerged from Einstein’s general theory of relativity, physicists wondered how seriously to take this mathematical description of an inescapable region of spacetime. Astronomers have since demonstrated that black holes are very real, with convincing evidence that quasars, x-ray binaries, even the center of our own Milky Way galaxy harbor these gravitational monstrosities. But the mathematics that predicts the existence of the black hole also describes entities that are even stranger. But whose relationship with reality is still unclear. One such entity is the white hole. A white hole is the “opposite” of a black hole, in a very literal, mathematical sense. In fact, it’s a time-reversed black hole. A black hole is defined as a region of inward-flowing space-time with a one-way boundary called the event horizon, from inside of which nothing can ever escape. That makes a white hole a region of outward-flowing space-time. It also has an event horizon, but that horizon prohibits entry, not exit. Nothing outside a white hole can ever enter, and everything inside must be ejected. Not even light can leave a black hole, hence the whole “black” thing. But light can only leave a white hole. So, these might be expected to radiate like crazy, and “white” would be an understatement. Now, before everyone gets too excited, white holes are probably a figment of mathematical imagination. But they’re a fascinating one. And the idea may help us understand the origin of the universe. White holes first emerged in the very earliest mathematical description of black holes. Only a few months after Einstein published his general theory of relativity, Carl Schwarzhild solved its equations for a very particular case. A single point of mass in an otherwise empty space-time. The resulting Schwarzschild Metric actually describes a black hole, the simplest black hole possible. One without spin, without charge, or without change. An eternal black hole, that doesn’t grow or shrink, and has always existed. We’ve talked quite a bit about the bizarre behavior of space, and especially time, at and below the event horizon of a black hole. Here’s a little playlist if you want a refresher. But here’s the low-down. The time that happens inside a black hole is not part of the past or future history of the outside universe. From the perspective of an outside observer, any events occurring at the event horizon, including falling into it, happen infinitely far in the future. Once you fall into the black hole, the Schwarzschild Metric tells us that space and time switch their roles. The singularity no longer occupies a central location it now occupies an inevitable future time. Now, a real black hole form from the gravitational collapse of a massive star’s core. After the collapse, the “future singularity” comes into being. And in the past, well, there’s just a star. But what does this idealized, eternal black hole look like in the past? If we followed the Schwarzschild Metric back in time, we find something very strange. We find the singularity again, lurking infinitely far in the past. From the point of view of the outside universe, the eternal black hole’s singularity exists in both the infinite future and infinite past. That may sound strange, but it gets stranger. To really understand what this eternal black hole looks like, we’re going to need to use a tool that we’ve already played with: the Penrose diagram. To refresh your memory: In a Penrose diagram, the x and y axes are redefined from space and time to merge space and time into new coordinates. They compactify space-time so that time bunches up towards the edges and the borders correspond to infinite past and future. Also, lines of constant distance and time curve, so that light paths always travel on 45 degree paths. We are hanging out here and now, at the center of the diagram. If we place an eternal black hole far to the left, then the future-left boundary represents the black hole’s event horizon. Any movement to the left brings you closer to that event horizon. The event horizon itself is a 45 degree line. In our weird Penrose coordinates, this represents a constant distance from the center of the black hole. Light traveling at that 45 degree angle takes infinite time to escape the event horizon. And the region beyond that line represents the interior of the black hole. There, the dimensions of space and time switch roles. The once-vertical contours of space are now time-like. And flow inexorably towards the future singularity. These two regions—our universe and the black hole interior—are just the Schwarzschild Metric mapped out using Penrose coordinates. But our map isn’t complete. Remember, this is an eternal black hole, so it must exist in the past Map into the past and we see a time-reflected version of our future black hole. Everything about it is time-reversed. The singularity is a past event. Space within is time-like, but instead of flowing towards the singularity, it flows away. And the event horizon is now a barrier to entry, not to exit. We could make some sense of the behavior of this strange region by using the Penrose diagram. Imagine: that something in our past was traveling at the speed of light and trying to reach the past event horizon. There’s no way it can get there, unless it goes faster than light. Oh, it’ll reach an event horizon, but only the event horizon of our future, where it plunges into a regular black hole. Remember, that all this is from our perspective, far from the event horizon. We can never see anything cross the horizon; the light rays from any crossing reach us infinitely far in the future. Even if the black hole plunge began far in the past. So, the past region of the eternal black hole has an event horizon that’s a barrier to entry. But also, light rays within that region must move up on the diagram. That suggests they must exit into the outside universe. Anything inside the past eternal black hole must be ejected. So far, this region fits perfectly the description of a white hole. The eternal black hole of the past technically is a white hole. However, it’s not one that we can ever observe. For two reasons: One: Light rays exiting that past white hole can never reach us. The past singularity and past event horizon are infinitely far in the past from our point of view. Light has to traverse infinite time to reach our location. And two: there’s no such thing as an eternal black hole. The universe hasn’t existed for eternity, and it didn’t even begin with black holes in place. Even though this type of white hole isn’t observable, some physicists have taken the description very seriously. The math describing the white hole is a perfectly good use of the Schwarzschild Metric. It obeys general relativity. It really is just a black hole, but if viewed backwards in time. Yet general relativity is time-reversal symmetric. Something that can happen forwards in time should also be able to happen in reverse. So, can new white holes actually form? Well, theoretically, yes, but to make one, you need to reverse entropy. See, although it’s possible to build a white hole in general relativity, there are other laws of physics the universe needs to obey, For example, the 2nd law of thermodynamics. It demands that entropy, a measure of disorder, always increase. This law defines the direction of the flow of time. To reverse time, you need to break the law. You need to decrease entropy. Now, this is technically possible because entropy is a statistical phenomenon. Very rare reductions in entropy do happen, as long as globally, entropy increases on average. It’s conceivable that an incredibly rare entropy dip could lead to an effective reversal in time and a white hole could form. However, it would immediately explode in a burst of energy as soon as entropy and time resumed their normal flow. Upwards and forwards. We actually did talk about a case where a random drop in entropy led to something very much like a white hole in this episode. It’s been speculated that the Big Bang itself came from such a profoundly improbable entropy dip. And as it happens, the Big Bang looks, mathematically at least, much like a white hole. It’s an expanding outpouring of space-time, containing a vast amount of energy, and the Bang itself can never be entered. After all, it’s in the past. The difference between the Big Bang and a white hole is that the former possesses no singularity. It happened everywhere at the same time. Still, that hasn’t stopped physicists from having fun with the idea. It’s been proposed that when a black hole forms, a white hole forms on the opposite… “side”. Energy entering the black hole exits the white hole. Physicist Lee Smolin takes it a step further to suggest that the resulting white hole is the Big Bang of a new, baby universe. And that, in fact, our universe formed that way. More on that another time. But speaking of other universes… It turns out that we haven’t finished building our Penrose diagram yet. The past white hole was revealed when we traced the eternal black hole backwards in time. In fact, what we did was to “maximally extend” space-time. We required that all paths be traceable through infinite past and future space, provided they don’t hit the singularity. But what about light rays entering or leaving our eternal black hole from the opposite side? The mathematics of the Schwarzschild Metric describes an entirely independent region of space-time parallel to our own. It looks like an identical alternate universe on the other side of the black hole. Accessible through what we call an Einstein-Rosen bridge – better known as a wormhole. In the not too distant future, we’ll investigate the reality of this mysterious parallel patch of space-time. Thanks to LegalZoom for sponsoring this episode. LegalZoom helps you take care of your legal needs. If you own a business, they can help you with the right formation, plus provide you with many of the tools and resources you need to run it. If you have a family, they can help you create your estate plan through their products and network of attorneys. You can also schedule an attorney consultation for business or personal legal advice through their independent network of attorneys. Without having to leave your home. Legalzoom is offering Space Time viewers 15% off their next purchase from Legalzoom. Go to Legalzoom.com/spacetime or click on the link in the description to learn more.

100 comments / Add your comment below

  1. What if an ancient civilization mastered all aspect of space time and created a white hole which created the big bang, erasing the previous universe. Okay time to sleep.

  2. OK, my first time hearing about White Holes. Just a guess here, but it seems like the first, obvious, thing to come to mind; maybe things get sucked into the Black Hole then get spewed out of the White Hole. What happens to it in between is anybodies guess. Unless someone has an answer for that, as well.

    My Best. Out.

  3. “Come to me, all you who are weary and burdened, and I will give you rest.” – Jesus Christ (Matthew 11:28 NIV)

  4. Question if you disappear into area infinitely small. What would there be to give it white or volume. You'd be reataching quarks, and such to replace what was removed before, wouldn't you

  5. You know, I always thought I had my head around the core concepts of relativity, space time, black holes and the likes. Until I watched this video. I got a lot more learning to do.
    Thanks a lot PBS Spacetime

  6. Like a smoke ring or donut ever rolling back in on itself, the shape of things could look like a giant depiction of a gravitational magnetic field diagram you see of earth enter the black hole – spewed out of the white big bang +. Like a giant recycling magnetic gravity engine spiraling through space building mass? & pulling all in its wake some how defeating friction at its core with speed of entry sling shotting mass through its centre? The mind boggles, red & blue shift light depict direction if that helps figure anything out visually lol

  7. Well I guess I'll be the one to say it dude look like a white hole… just my opinion……☻
    A seed is created in the dark
    Have they found any white holes Shining on the floor of the Ocean by any chance just wondering
    ☻Dogon☻☥☥☥
    Cosmos

  8. It just feels like the white holes exist in pocket dimensions connected to black holes…. they’re in the same spot, in a sense, but exists parallel to that black hole. Idk I know nothing about this

  9. Wouldn't a white whole just look like a super massive star?

    Is it possible that we have seen many, while not recognizing then for what they really are?

  10. Every action has an equal and opposite reaction.. why wouldn’t a black holes act balancer be a white hole?

  11. sing+ ularity its a entry. not a point , the is a ponit ity or neualie what is time? I just mention that read again no not smart electrons at a point of five ao sp this is the ity city of the dark contrast of space

  12. all the black holes of the universe… eventually will swallow everything right? hence it will be like mirroring the while hole and the space still expanding them? I mean if you see big bang and far far our universe where everything was eaten it's the same right? space expnasion just slowly evaporating the black hole invariant potential? I mean will it make sense to say black hole 1,,2,3, ? Uniformity will make them act like fluctuations right?

  13. Literally nobody even knows exactly what singularity means. It's a word concocted by some scientists trying to explain the universe when they can't.

  14. Thought experiment: Consider a White Hole as the largest imaginable – our observable universe expanding. Would the Cosmic Background Radiation stage of this expansion surrounding the source be equivalent to a Black Holes accretion disk orbiting its source? Since these two phenomena are opposites.

  15. Usually I'm pretty good at understanding theories about space time, but this? I'm more than a little confused.

  16. So we just recently discovered what happened after 2 black holes collided together but what would happen if a black hole and a white hole collide??

  17. Perhaps White Holes share their event horizons with Black Holes, but produce a transformed energy or matter… Hawking Radiation?

  18. I don't know if I heard this anywhere else, or if anyone else in the comments thought this, but I think that white holes appear in antimatter galaxies, where matter is opposite.

  19. Well, if they were real the black hole should not keep its mass as it would got out the other side.

  20. White hole would have negative gravity to push the incoming light of. Its impossible otherwise perpetum mobile would be possible, just push white hole and black hole next to each other and they would chase each other forever.

  21. The Universe is Electric. Not gravitic. It's time to update our cosmology into the 21st century. Thunderbolts.info = Real physics. Real experiments. Real predictions. Real evidence. Explained in terms you can understand. No theoretical abstractions. Thunderbolts.info

  22. @4:41 To refresh your memory !! 😀 😀 😀 of a guy who just watched a video of cat scared of cucumber..

  23. Black hole stuff goes out white hole…what if another black hole there waiting for white hole stuff, would a possible universe be sucked up immediately by that 2nd black hole? And if that were the case would the 2nd white hole create a super universe? Now I understand god and religion. It doesn't hurt the brain.

  24. Okay a black hole is a large body of mass and weight so great that it makes a hole in space and time a white hole is impossible because a black hole is just matter while a so called white hole would be energy and at some point it would run out and be no more a black hole does not suck things in things fall in a thing that pushes objects away would have to use energy and it would loss it so a white hole would die very very fast even fast then a gient white star

  25. Could a white hole just be what's on the other side of a back hole? One takes in and the other pushes out.

  26. ok so lets say white holes do indeed exist how low would their escape velocity have to be as a blck holes is at light speed meaning you would have to travel even faster than light speed to escape its gravity or atleast that would be the case if not for it's infinite density

  27. thay are talking about a "" white hole"" opposite end of a real black hole . Matter pulled by a black hole gose in a separate dimension and white holes repulsive Gravity spreading out all matter in another universe so it is a infinite circle😅😅😂😂
    no body ask what about increasing Event Horizon ????
    when black eat something its Event Horizon increase it means matter dose not go anywhere it stays in our universe .
    in this case what white hole pull out??
    anything looks just fine on a pepper doesn't mean a real possibility in our real reality.
    you can subtract 50-80=-30 and it a right answer but in real world you cannot get -30 bear from your refrigerator.😊

  28. Why don't we take prisoners sentenced to life and send them into black holes so we can know for sure what happens.. in orde to advance our knowledge of the cosmos we have to take giant leaps and stop being pussies..

  29. A white hole could be the whole universe itself. And the exiting matter could be those virtual particles appearing into existence

  30. I didn't watch this vid.I've given up on this because of the Guess Work going on on a Religious scale.If every object that approaches a black hole freezes in time then wouldn't black holes be littered with objects all around it. Is that what a Quazar really is all the objects that fell in frozen in time around it.Since we haven't seen any white holes maybe our sun is a white hole, maybe theirs a black hole for every white hole but our Sun's black hole is on the negative side of the universe. So if you entered a black hole here you come out throw a star on the other side or go into our sun and come out a black hole on the negative side or just some where else in our universe. well I guess I can see how much fun it is to guess.

  31. our known Universe exploded from a white hole after all matter reached a perfect pitch while anti-matter exploded from the black hole ,multi Universe to keep perfect balance,all matter will race back around to its start,this is life cycle of our Universe

  32. If white "holes" are the opposite of black holes then I think it's not a good idea to call them "holes" since the opposite of a hole can obviously not be a hole. A hole is "something on the edge and there is nothing in the middle" . The entity they call white "hole" is "everything is in this middle and nothing surrounds it".

  33. What happens inside of a BH is matter is still being compressed much more than the event that forms one when the mother star first collapsed forming the BH itself, matter is so compressed that it's not detectable possibly smaller than a molecule but infinitely dense, this event will spark another singularity creating big bang on the other side of the BH, these events have been going on for trillions and trillions of years birthing an infinite number universes, our universe crazily large but only one of an infinite number

  34. if we say in relativity we have to involve an object and an observer, can we say that if there is only one atom in the whole universe relativity can never work? because i for one tend to look at the universe as a mirror that mirrors and creates infinite relative possibilities, so can we then say that relativity still works on a quantum scale in relation to the universe and space time for objects that cannot work with relativity on a grand scale which makes them stable enough to work on a scale of lesser energy required for a single mass to reach the speed of light?

  35. Maybe this happens on an infinitely small and infinitely large scale. Maybe the small black holes have the same size white holes at the center of our galaxy after all we cant see the center of our galaxy. There's probably infinitely large black holes swallowing galaxies and infinitely large white holes extruding galaxies but we can't see them because we aren't close enough to the white holes and if we were you probably couldn't see the black holes being to far away and if I'm not mistaken black holes can grow. Implying white holes can too. So near the end of our time in this universe you will end up with one super massive black hole and one super massive white hole filled with all different size white and black holes and they will merge into each other then collapse on it self creating a giant black hole but on the otherside is the big bang (super massive white hole) keep in mind this covers trillions and trillions of light years and the thought that everything is expanding but also shrinking. It's hard to grasp and hard to prove. Maybe that's the point.

  36. There was one famous white hole known as the big bang. Everything came out of singularity.White hole was in the past.

  37. I was under the understanding that black holes with no change were just a special case of the maths of the Schwarzschild, because they were not advanced enough to describe an actual black hole.

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