How to Build a Black Hole | Space Time | PBS Digital Studios

[MUSIC PLAYING] Black holes are one of the strangest objects in our universe. To make one, we need both general.


[MUSIC PLAYING] Black holes are one of
the strangest objects in our universe. To make one, we need
both general relativity and quantum mechanics. Today, I’m gonna show you how. [MUSIC PLAYING] In a previous episode, we
discussed the true nature of black holes. We talked about them as
general relativistic entities, as space time regions whose
boundary curvature effectively removes the interior from
our observable universe. Now, it’d be a great idea
to watch this video first, if you haven’t already. Now, these are some
abstract ideas. And really, black holes
were, at first, just a strange construction
of general relativity. And just because something
exists in the mathematics does not mean it has
to exist in reality. So are black holes real? The answer is yes. Black holes are
astrophysical realities that we have ample evidence for. Yet, to actually
form a black hole, Einstein’s descriptions of
mass energy and space time are not enough. We need quantum mechanics. If you’re up for it,
let’s build a black hole. First step– find a very
massive star, and wait. Let it cook– not for long
because these guys have very short lives. Just wait a few million
years for the supernova. If you get impatient, you can
turn up the core temperature by bombarding it with
gravitational waves. It’ll be done quicker. The details of the
deaths of massive stars are pretty awesome. But they can be found
in lots of places. So we’ll just gloss
over them here. In the last throes of a
very massive star’s life, increasingly frantic
fusion in the interior produces one periodic
table element after another, in
Russian doll shells of increasingly
heavy nuclei that finally surround an iron core. The formation of
that core represents the end of exothermic fusion. Fusing two iron nuclei
absorbs energy. It doesn’t release it. So starved of an energy
source, the stellar core collapses on itself. Electrons are slammed into
protons in the iron nuclei, forging a neutron star. The collapsing outer
shells ricochet off this impossibly dense nugget
in a supernova explosion, enriching the galaxy
with juicy new elements. The leftover core,
the neutron star, is a very weird beast– a ball
of neutrons the size of a city, with a mass of at least
1.4 suns and the density of an atomic nucleus. We see them, when we
see them, as pulsars. Now, beneath the thin
atmosphere of iron plasma, a neutron star is a
quantum mechanical entity. And it’s a quantum phenomenon
that saves it, for the moment, from final collapse. It’s also a different
quantum phenomenon that will let us push
it over the edge, creating a black hole. To understand how space works
for a quantum object like this, we need to think not in regular
3D space or even 4D space time but, rather, in six dimensional
quantum phase space. For a neutron star,
this is the space of both 3D position
and 3D momentum. And it defines the
volume that can be occupied by the strange
matter in a neutron star. Now, the exact way that the
matter of a neutron star fills this 6D
quantum phase space depends on two
important principles of quantum theory,
the Pauli exclusion principle and the Heisenberg
uncertainty principle. These govern the
delicate balance between stability and collapse. The Pauli exclusion
principle basically just says that two things can’t
occupy the same place at the same time. And by thing, I mean
fermion, the particle type comprising all regular matter. For example, electrons,
protons, and neutrons. Now, by place, I mean location
in quantum phase space. So two fermions can occupy
the same physical location just fine, as long as their
momenta or any other quantum property is different. Now, this rule is
what keeps electrons in their separate stable
orbits and, in turn, is part of what allows solid
matter to have its structure. In the case of a neutron star,
position momentum phase space is completely full of neutrons. Every spatial location and
every momentum location connected to those spatial
locations contains a neutron. OK. Jargon alert. This weird state of
matter where phase space is completely full– we
call it degenerate matter. And the degeneracy pressure,
resulting from particles not having anywhere
else to collapse into, is incredibly
strong– strong enough to initially resist the
insane gravitational crush of a neutron star. As far as we know,
there’s no way to overcome Pauli exclusion–
at least, not directly. See, it’s not a matter of force. Two fermions just can’t ever
occupy the same quantum state. And that’s that. So the neutron star is safe. But come on. We want to build a black hole. Fortunately, there’s
another quantum phenomenon that lets us get around the
Pauli exclusion principle. The Heisenberg
uncertainty principle tells us that the properties
of a quantum entity are fundamentally uncertain. The details may be a
topic for another episode, but in short, quantum
mechanics describes matter as a distribution
of possibilities. Certain numerical
properties that you can assign to a
particle exist in a wave of varying degrees of maybe. Location is one such property. A neutron, for instance,
is not in any one place but exists as a cloud
of possible locations that might be
tightly constrained or may be very spread out. Location remains a
possibility cloud until the neutron interacts
with another particle, at which point, its
location is resolved. This is the weirdest, coolest
aspect of quantum mechanics. And we’ll try to get back
to it in another episode. But for now, we have
a black hole to make. The Heisenberg
uncertainty principle tells us that particular
pairs of quantities, position and momentum
or time and energy, must, when taken together,
contain a minimum degree of uncertainty. If one is tightly
constrained, then the other must be uncertain and span a
wide range of potential values. So a neutron star is comprised
of the densest matter in the universe. Its constituent neutrons
are about as constrained in position as you can get. Therefore, the Heisenberg
uncertainty principle tells us that they must have
highly undefined momenta. Very, very large
neutron velocities become part of the
possibility space. To put it another
way, the neutrons are packed so close
together in position space that their momentum
space becomes gigantic. Phase space expands. And here’s the
thing– the denser the neutron star becomes, the
more momentum space you get. So Heisenberg lets us circumvent
that pesky degeneracy pressure. If we can somehow add more
matter to a neutron star– throw another star
at it, maybe– it won’t get spatially larger. The extra matter certainly
needs somewhere to go. The star must expand. But it doesn’t expand
in position space. The star expands
in momentum space. In position space, it
actually gets smaller. The more massive of the neutron
star, the smaller its radius. This is a quantum effect,
even though it’s happening on the scale of a star. Until now, the neutron star has
hovered above a critical size. The space time curvature at
the neutron star’s surface is pretty extreme. Clocks run noticeably slower. And the densities
inside the star produce some very
strange states of matter. However, despite this, the
star is still very much a thing in this universe. And yet, below the
star’s surface, there lurks the potential
event horizon, the surface of infinite time dilation. Now, the event horizon
doesn’t actually exist as long as the
neutron star stays larger than the would-be horizon. However, if we can increase
the mass of the neutron star, the actual star shrinks, and
the event horizon expands. You can see where
I’m going with this. There’s a mass where the
radius of the neutron star and the event horizon overlap. It’s three times
the mass of the sun. At this point, the event horizon
actually comes into being. And the neutron star
submerges beneath it. We’ve finally created
our black hole. But what happens
to the star when it slips below its event horizon? Everything inside is
lost from this universe. Space time is radically
altered inside the star with all geodesics, space
time paths, turning inward, towards the center. When the black hole
first forms, the material inside must resemble the stuff
of the original neutron star. But there’s no stopping
ultimate collapse. All paths lead to the central
point of infinite curvature, the singularity. From the point of view
of the star itself, the inward cascade happens. All position space collapses
towards the singularity. While momentum space
expands accordingly, with the corresponding enormous
velocities all inward-pointing. Neutrons are certainly
shredded into component quarks and gluons. But what happens to these
as the star approaches an infinitesimal point,
the Planck scale? Physics cannot yet tell us. From the point of view of
an outside observer– so, us– this never happens. The black hole forms. The stellar core goes dark. But on our timeline,
nothing ever happens beyond the
event horizon again. We can’t meaningfully think
about what’s happening now; beneath the event horizon
there is no corresponding now. The material of the star and all
events that happen to it are no longer a part
of the timeline of the external universe. On our clock, the singularity
forms infinitely far in the future. To us, there is only
the event horizon. So this is how a real
astrophysical black hole is made. The mass of the stellar core
becomes the apparent mass of the black hole. And very few other properties
of the collapsed material are remembered. The black hole retains mass,
electric charge, and spin. And these continue to influence
the outside universe, sometimes in very important ways. Of course, a real black hole
is not the static creature that we sometimes
describe in theory. They grow. They leak. They change. We’ll get to what this
means, for black holes and for the universe, in
another episode of “Space Time.” In a previous episode, we talked
about the Alcubierre drive. Well, our friends over
at “The Good Stuff” just made a video
about a man who’s attempting to build his own
Alcubierre drive in his garage. You should check this out. They interview some
Australian astrophysicist about the drive’s plausibility. Now, “The Good
Stuff” guys talk some smack about the lack of
beards here on “Space Time.” And sure, they have some
pretty luxuriant flavor savers. But I challenge you guys to
grow this much handsome stubble in between single frames. Now, in the last
full episode, we talked about how to
stop a killer asteroid from hitting the earth. You guys had some
great questions. Jonathan Sny and others
wonder whether, instead of the gravitational
tractor, you could just land a spacecraft
on the asteroid and push it with its rockets. Well, actually, it’s going to
take the same amount of fuel to pull by a
gravitational tractor as it would to push
an asteroid by landing a rocket on it, assuming
that the rocket can push with perfect efficiency. Now, that’s tricky because
the asteroid will certainly be rotating. And you can only push when
the rocket is pointing in the right direction. Also, as we’ve
discovered recently, when we landed Philae
probe on a comet, landing on irregularly shaped bodies,
with very weak gravity, is extremely tricky. The gravitational tractor
gets around these issues. moxshyfter asked about the
plausibility of directing a killer asteroid into the sun. So even the largest
asteroid hitting the sun would barely make a splash. The problem is that changing its
velocity enough to hit the sun, or even to fall into
Earth’s orbit– which was another suggestion–
would take vastly more energy than just nudging it off course. Sam Gilfellan wants
know how large an object we’d need to destroy
in order to form a ring system around the earth. So if we want a ring system like
Sam’s, that has the same ratio of planet mass to ring mass–
of about 1 to 50 billion, then we’d need an
object the same size as the one that killed the
dinosaurs, so more than 100 trillion tons. We’d also need to nudge it off
direct impact and explode it. But totally worth it. A ring system around the
earth would be awesome. A lot of people point out that
One-Punch Man could easily destroy a killer asteroid. I agree. NASA, this is “Space Time.” Tell Mr. Willis to stand down. Yeah. We have a new guy. [MUSIC PLAYING]

100 thoughts on “How to Build a Black Hole | Space Time | PBS Digital Studios”

  1. Are neutron stars uniform density, or are they more dense towards the middle? If there is a density gradient, and the inside gains the critical density to become a black hole, but the outer part does not, and the inside collapses…
    1. Could you get a black hole inside the neutron star? If the outer layers fall in, they might not have the same density as the inner layers.
    2. Is there outwards pressure from the core post-collapse? If spacetime is pinched/asymptoted off then there is no volume available inside the star, and all the space curving down the asymptote was occupied by mass, so would it be empty? Does the density and pressure change?

  2. Every time He says "however" I'm reminded of a Godzilla Movie and expect something terrible to happen โ€ฆ not very scientific, I know.

  3. isnt it just mind blowing that if you fill a room way over its max capacity it collapses in on itself and becomes a black hole… just.. HOW!!!

  4. This episode caught Dr. oDowd late. In his bedroom, just out of shower, he forgot to change in streaming chothes, put on his beard, and grab his studio-grade microphone, so he's recording on the phone.

  5. I made mine in my basement. The super nova exploded my home and the insurance says it's not paying for this. Can anyone help???

  6. *Why do I need to a guy moving his hands in every video*,

    He is not helping in explaining or delivering an idea.

    is he trying to be famous or the channel lacks video materials??

    I believe he thinks (I look smart then I'll be famous)

    But it only makes the videos more weird.

  7. Wow. Why has nobody explained this to me before? But I have so many more questions now. Would an observer falling into a back hole see a neutron star, or a singularity? Also, the moment the event horizon becomes larger than the neutron star…… is this instantaneous, or is there a some kind of transitional period where it has properties of a black hole and a neutron star? How long could a star stay in this transitional state (from an outside timeline).

  8. I have nothing to say reaallyyy ๐Ÿ˜๐Ÿ˜๐Ÿ˜๐Ÿ˜๐Ÿ˜๐Ÿ˜๐Ÿ˜๐Ÿ˜๐Ÿ˜๐Ÿ˜

  9. What is the charge of black hole (+or -), and if neutron stars are made of neutrons than black hole are made of what higgs bosonssssss hhhhhhh just a theory

  10. So, if the majority of the mass of a boson comes from the confinement of its quarks by the strong nuclear force, why doesn't the mass drop and the event horizon shrink when the neutrons of the neutron star are pulled apart? And what is the source of mass of the singularity and why is the mass of the original star conserved?

  11. I guess that answers my question of why fusion doesn't start back up, if a black hole sucks up a bunch of hydrogen. But with Hawking Radiation, why doesn't the black hole turn back into a neutron star? Wouldn't losing mass cause it to balloon back out, or does that mean since it doesn't do that, that it really is a hole in spacetime?

  12. The old guy was good but I can't help but like this guy more, I feel more comfortable with his voice and body language for some reason.

  13. Asteroid belt around Earth… well, maybe cool to think of, but in the same mass ratio like Saturn, would it be visible even at night?
    And we have just a man made spacedebris problem. Do we need urgent another potential field of dangerous debris to navigate through?

  14. I understood many of the words used in the making of this video. But it does help me understand a David Brin book I've read. Heaven's Reach.

  15. All the neutrons are destroyed in the heart of a star when it collapses into a tiny singularity. This tiny object contains all the mass and exerts the same amount of gravity as the stellar core. Maybe this gravitation mass is the fundamental state of reality that is the singularity… It is just a compact speck of space-time.

  16. hope isis dont see this video… we fucked if they learn quantum mechanics and some how hack the large hadron collider. can you imagine??

  17. What's inside a BH? There is simply nothing because it's not there yet.
    One could even say that knowing the BH evaporates in less than infinite
    time, then the objects entering the horizon are in fact being "vaporised"
    during the same less than infinite time, like water drops on a hot pan.

    There is something I don't hear though about BH: entering the horizon
    doesn't mean the falling object as reached c speed. So its clock doesn't
    seem to be stopped because of special relativity (speed) but because of
    general relativity (gravity). Misconception?

    Another: do falling object ever get converted to energy? if so, that
    avoids the problem of infinite density, no?

    Last, when a BH gets smaller by evaporation, shouldn't its mass become
    insufficient to overcome neutron degerecy pressure (iirc) and pop back into
    normal space ? (well not really visibile since it would long dead and cold
    by that time…) That's maybe a naive question, but I've never
    read/watched anything explaining why not…
    Thanks for redirecting me to clarifying material, if any.

  18. how can black holes last for an infinite amount of time on our scale if we know they die on our scale due to hawking radiation?

  19. https://www.facebook.com/photo.php?fbid=2351389634895148&set=a.1285245298176259&type=3&theater
    Can someone help me out? I had an idea and i can figure out if its crap! Its supposed to be on my facebook page because i can't post pictures to the comments. thanks!

  20. omg so basically we are "waiting" to see wtf happened to the star and hence all we see is like a LAG (blackhole) we can only truly "see" what happened if we are on the other side(s)

    LOL my head hurts ๐Ÿ˜€

  21. What happens if one of a pair of quantumly entangled particles falls into a blackhole while the other remains outside?

  22. so a neutron star could be just on the other side or the Event Horizon of some black holes if we would not know when we cross an event horizon why would the neutron star

  23. I feel like quantum physics is less about the math and more about understanding completely screwball concepts that make basically no sense to us.

  24. Whenever I click on a video it says โ€œyou should watch this video firstโ€ ok soooo maybe make a playlist that is in order or else Iโ€™ll never be able to watch anything on here

  25. if in our timeline we see the black hole "frozen in time"' how can we notice the black hole growing or evolving

  26. The minimum mass of a pulsar is 1.44 solar units (the chandrasekhar limit).
    Minimum mass for a black hole is double that (the Holiday limit)

    White dwarfs contain degenerate matter (matter that has overcome electron degeneracy). They are 200,000 times more dense than granite.
    Pulsars have over come both electron and nuetron degeneracy.
    There are no infinite singularities. No infinite density. No time stop event horizons. These are mathematical errors that do not exist in space time.
    Current theory is extremely complex because it is detached from what is real.
    Black holes are really black holes connected to white holes in the shape of an Einstein-Rosen Bridge.
    The star Betelgeuse will soon prove this to be correct.
    And we can discard thinking in 6 dimensions unless we are talking about a 6 dimensional object.

  27. Youtube comments are full of amusements sometimes….
    https://chrome.google.com/webstore/detail/threelly-ai-for-youtube/dfohlnjmjiipcppekkbhbabjbnikkibo

  28. I wish I could go back in time and tell past Brian that we took a picture of one only four years later. I wonder what heโ€™d say.

  29. I find black holes interesting but very confusing.

    Can black holes be theoretically destroyed by being pried apart from their dense state by other nearby matter?

    For example if there is a black hole, and it orbited by many black holes or even many, many dense stars, then would the other black holes or stars combined gravity impact on the inner black hole and (providing can be made to remain stable in orbit) reverse the state of the black hole being a black hole?

  30. Are 'juicy" new elements measurable or quantifiable on any known scale? Like the Scolville scale for spiciness heat? The Dowd Juicy Scale?

  31. Let's say you are in a space ship parked in front of a clock… As soon as the clock strikes noon you instantly reach light speed and travel away from the clock….
    Why does that mean time stopped?

    The clock IS still changing, we just don't see it because the light from the clock showing 12:01 can't catch up to us.
    Let's say you have a clock on your ship that's synchronized to the clock you're traveling away from and you place it on the dashboard of your ship. You see it changing time because the light is coming to you. This clock matches the clock behind you, so you can assume the clocks are both changing at the same moment. Right?

    Biological processes are still occurring in our body, we are still aging, correct?
    Just because light can't catch us why does that mean time has stopped?

    Like if someone shoots at you and the bullet is traveling 100mph, you travel at 100mph in the same direction… The bullet never hits you.
    Same with the light coming from the clock. So I don't understand why that stops time. How do we stop aging just because we are going fast….
    Does this mean light isn't aging? In a vaccum of course..
    But the moment light is created in our sun and travels to Earth. Is it not aging? The moment it hits water on earth and slows down it finally starts to become older?

  32. PBS Space Time, I have a question.
    What's up with the star designated R136a1?
    Isn't it impossible for stars to actually become this big? How is this giant possible?

  33. Ohhhhhh….. we just need to think in 6 dimensions. Well why didn't I think of that? I'm sitting here stretching my brains feeble intellectual capacity to its limit trying to comprehend black holes and 4d space time but this entire time I was 2 dimensions short.
    #facepalm #sillyme #imaworthlessstupidpieceofshit

  34. Any thoughts on whether it's correct to say
    a vacuum is a region of space wherein matter and antimatter exist in equilibrium?

  35. What would happen if a black hole has so much mass the all of the physical space of all possible momentums up to the speed of light are taken up and the uncertainty cannot exist without breaking causality?

  36. I was all ready to go and make a black hole, but there's a slight shortage of neutron starsin my local stores. any ideas.

  37. You're pretty much the only one I've heard actually get this stuff right. Especially the part about how due to the impossibility of defining a universal simultaneity, that there is no "now", no "what is happening now" to the material that formed the black hole. It pisses me off every time I hear someone say the size of the observable universe is something like 80 billion light-years because they reject that what you see 13.8 billion light-years away is 13.8 billion light-years away "right now" and insist that it's much further away "right now". No it isn't, there's no such thing as right now, for it, it has passed the static limit, the edge of the universe from our reference frame, and that's the same as falling through the event horizon of a black hole, and it is not possible to talk about what it's doing right now, 13.8 billion years after emitting the light we're now seeing, because it has left our timeline. It is just as valid to say that it "is" 13.8 billion light years away, if it was 13.8 billion light years away from where we are now, 13.8 billion years ago, because from the reference frame of the photon emitted by there and arriving here, the 2 events were simultaneous.

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