Can a black hole be destroyed? - Fabio Pacucci
-
0:07 - 0:12Black holes are among the most
destructive objects in the universe. -
0:12 - 0:16Anything that gets too close to the
central singularity of a black hole, -
0:16 - 0:19be it an asteroid, planet, or star,
-
0:19 - 0:24risks being torn apart by its
extreme gravitational field. -
0:24 - 0:29And if the approaching object happens
to cross the black hole’s event horizon, -
0:29 - 0:32it’ll disappear and never re-emerge,
-
0:32 - 0:36adding to the black hole’s mass and
expanding its radius in the process. -
0:36 - 0:39There is nothing we could throw
at a black hole -
0:39 - 0:41that would do the least bit of
damage to it. -
0:41 - 0:44Even another black hole won’t destroy it–
-
0:44 - 0:47the two will simply merge into a larger
black hole, -
0:47 - 0:52releasing a bit of energy as gravitational
waves in the process. -
0:52 - 0:53By some accounts,
-
0:53 - 0:58it’s possible that the universe may
eventually consist entirely of black holes -
0:58 - 0:59in a very distant future.
-
0:59 - 1:06And yet, there may be a way to destroy,
or “evaporate,” these objects after all. -
1:06 - 1:07If the theory is true,
-
1:07 - 1:10all we need to do is to wait.
-
1:10 - 1:11In 1974,
-
1:11 - 1:14Stephen Hawking theorized a process
-
1:14 - 1:17that could lead a black hole
to gradually lose mass. -
1:17 - 1:20Hawking radiation, as it came to be known,
-
1:20 - 1:26is based on a well-established phenomenon
called quantum fluctuations of the vacuum. -
1:26 - 1:27According to quantum mechanics,
-
1:27 - 1:33a given point in spacetime fluctuates
between multiple possible energy states. -
1:33 - 1:37These fluctuations are driven by the
continuous creation and destruction -
1:37 - 1:40of virtual particle pairs,
-
1:40 - 1:44which consist of a particle and its
oppositely charged antiparticle. -
1:44 - 1:49Normally, the two collide and annihilate
each other shortly after appearing, -
1:49 - 1:51preserving the total energy.
-
1:51 - 1:57But what happens when they appear just at
the edge of a black hole’s event horizon? -
1:57 - 1:59If they’re positioned just right,
-
1:59 - 2:02one of the particles could escape the
black hole’s pull -
2:02 - 2:04while its counterpart falls in.
-
2:04 - 2:08It would then annihilate another
oppositely charged particle -
2:08 - 2:10within the event horizon
of the black hole, -
2:10 - 2:13reducing the black hole’s mass.
-
2:13 - 2:15Meanwhile, to an outside observer,
-
2:15 - 2:19it would look like the black hole
had emitted the escaped particle. -
2:19 - 2:25Thus, unless a black hole continues
to absorb additional matter and energy, -
2:25 - 2:30it’ll evaporate particle by particle,
at an excruciatingly slow rate. -
2:30 - 2:31How slow?
-
2:31 - 2:37A branch of physics, called black hole
thermodynamics, gives us an answer. -
2:37 - 2:42When everyday objects or celestial bodies
release energy to their environment, -
2:42 - 2:44we perceive that as heat,
-
2:44 - 2:47and can use their energy emission to
measure their temperature. -
2:47 - 2:49Black hole thermodynamics
-
2:49 - 2:53suggests that we can similarly define the
“temperature” of a black hole. -
2:53 - 2:56It theorizes that the more massive the
black hole, -
2:56 - 2:58the lower its temperature.
-
2:58 - 3:00The universe’s largest black holes
-
3:00 - 3:06would give off temperatures of the
order of 10 to the -17th power Kelvin, -
3:06 - 3:09very close to absolute zero.
-
3:09 - 3:13Meanwhile, one with the
mass of the asteroid Vesta -
3:13 - 3:16would have a temperature close to 200
degrees Celsius, -
3:16 - 3:21thus releasing a lot of energy
in the form of Hawking Radiation -
3:21 - 3:23to the cold outside environment.
-
3:23 - 3:25The smaller the black hole,
-
3:25 - 3:27the hotter it seems to be burning–
-
3:27 - 3:30and the sooner it’ll burn out completely.
-
3:30 - 3:31Just how soon?
-
3:31 - 3:32Well, don’t hold your breath.
-
3:32 - 3:37First of all, most black holes accrete,
or absorb matter and energy, -
3:37 - 3:41more quickly than they emit
Hawking radiation. -
3:41 - 3:45But even if a black hole with the
mass of our Sun stopped accreting, -
3:45 - 3:49it would take 10 to the 67th power years–
-
3:49 - 3:53many many magnitudes longer than the
current age of the Universe— -
3:53 - 3:55to fully evaporate.
-
3:55 - 3:59When a black hole reaches
about 230 metric tons, -
3:59 - 4:02it’ll have only one more second to live.
-
4:02 - 4:04In that final second,
-
4:04 - 4:07its event horizon becomes
increasingly tiny, -
4:07 - 4:11until finally releasing all of its energy
back into the universe. -
4:11 - 4:15And while Hawking radiation has never
been directly observed, -
4:15 - 4:20some scientists believe that certain gamma
ray flashes detected in the sky -
4:20 - 4:23are actually traces of the last moments
-
4:23 - 4:28of small, primordial black holes formed
at the dawn of time. -
4:28 - 4:32Eventually, in an almost inconceivably
distant future, -
4:32 - 4:36the universe may be left
as a cold and dark place. -
4:36 - 4:38But if Stephen Hawking was right,
-
4:38 - 4:39before that happens,
-
4:39 - 4:44the normally terrifying and otherwise
impervious black holes -
4:44 - 4:48will end their existence in a final
blaze of glory.
- Title:
- Can a black hole be destroyed? - Fabio Pacucci
- Speaker:
- Fabio Pacucci
- Description:
-
View full lesson: https://ed.ted.com/lessons/can-a-black-hole-be-destroyed-fabio-pacucci
Black holes are among the most destructive objects in the universe. Anything that gets too close to a black hole, be it an asteroid, planet, or star, risks being torn apart by its extreme gravitational field. By some accounts, the universe may eventually consist entirely of black holes. But is there any way to destroy a black hole? Fabio Pacucci digs into the possibility.
Lesson by Fabio Pacucci, directed by Provincia Studio.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:49
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