A black hole in your pocket?


Transcript


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What would happen to you if a black hole the size of a coin suddenly appeared near you?

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Short answer: you’d die.

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Long answer: it depends.

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Is it a black hole with
the mass of a coin,

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or is it as wide as a coin?

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Suppose a US nickel with
the mass of about 5 grams

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magically collapsed into a black hole.

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This black hole would have a radius
of about 10 to the power of −30 meters.

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By comparison, a hydrogen atom is about
10 to the power of −11 meters.

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So the black hole compared
to an atom is as small as

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an atom compared to the Sun.

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Unimaginably small!

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And a small black hole would also have
an unimaginably short lifetime

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to decay by Hawking radiation.

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It would radiate away what little mass it
has in 10 to the power of −23 seconds.

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Its 5 grams of mass will be converted
to 450 terajoules of energy,

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which will lead to an explosion
roughly 3 times bigger than

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the atomic bombs dropped on
Hiroshima and Nagasaki combined.

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In this case, you die.

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You also lose the coin.

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If the black hole had the
diameter of a common coin,

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then it would be considerably
more massive.

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In fact, a black hole with
the diameter of a nickel

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would be slightly more
massive than the Earth.

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It would have a surface gravity
a billion billion times greater

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than our planet currently does.

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Its tidal forces on you would be so strong

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that they’d rip your
individual cells apart.

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The black hole would consume you before
you even realized what’s happening.

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Although the laws of gravity
are still the same,

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the phenomenon of gravity that you’d
experience would be very different

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around such dense objects.

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The range of the gravitational attraction

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extends over the entire
observable universe,

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with gravity getting weaker the farther
away you are from something.

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On Earth right now, your head and your
toes are approximately the same distance

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from the center of our planet.

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But if you stood on
a nickel-sized black hole,

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your feet would be hundreds
of times closer to the center,

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and the gravitational force would be
tens of thousands of times as large

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as the force on your head and
rip you into a billion pieces.

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But the black hole wouldn’t
stop with just you.

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The black hole is now a
dominant gravitational piece

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of the
Earth–Moon–Black-Hole-of-Death system.

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You might think that the black hole would
sink towards the center of the planet

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and consume it from the inside out.

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In fact, the Earth also moves up onto the black hole and begins to bob around,

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as if it were orbiting the black hole,

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all while having swathes of mass eaten with each pass,

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which is much more creepy.

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As the Earth is eaten up from the inside,

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it collapses into a
scattered disk of hot rock,

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surrounding the black hole
in a tight orbit.

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The black hole slowly doubles its mass
by the time it’s done feeding.

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The Moon’s orbit is now highly elliptical.

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The effects on the Solar system
are awesome—

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in the Biblical sense of awesome,
which means terrifying.

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Tidal forces from the black hole would
probably disrupt the near-Earth asteroids,

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maybe even parts of the asteroid belt,

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sending rocks careening
through the Solar system.

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Bombardment and impacts
may become commonplace

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for the next few million years.

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The planets are slightly perturbed, but
stay approximately in the same orbit.

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The black hole we used
to call Earth will now

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continue on orbiting
the Sun in the Earth’s place.

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In this case, you also die.

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This bonus video was made possible
by your contributions on Patreon.

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Thank you so much for your support!

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The topic is based on a question on
the AskScience subreddit

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and the glorious answer by Matt [Caplin?],
who also worked with us on this video.

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Check out his blog, Quarks and Coffee,
for more awesome stuff like this!

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If you want to discuss the video,
we have our own subreddit now.

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To learn more about black holes or equally
interesting neutron stars, click here.

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Subtitles by the Amara.org community

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