Could the Earth be swallowed by a black hole? - Fabio Pacucci
From asteroids capable
of destroying entire species,
to gamma-ray bursts and supernovae
that could exterminate life on Earth,
outer space has no shortage of forces
that could wreak havoc on our tiny planet.
But there’s something in space
that seems more terrifying
than any of these –
something that wipes out
everything it comes near.
Could the Earth
be swallowed by a black hole?
A black hole is an object so dense
that space and time around it
are inescapably modified,
warped into an infinite sink.
Nothing, not even light,
can move fast enough
to escape a black hole’s
gravitational pull
once it passes a certain boundary,
known as the event horizon.
Thus, a black hole is like a cosmic
vacuum cleaner with infinite capacity,
gobbling up everything in its path,
and letting nothing out.
To determine whether a black hole
could swallow the Earth,
we first have to figure out
where they are.
But since they don’t emit light,
how’s that possible?
Fortunately, we’re able to observe
their effect on the space around them.
When matter approaches a black hole,
the immense gravitational field
accelerates it to high speed.
This emits an enormous amount of light.
And for objects too far away
to be sucked in,
the massive gravitational force
still affects their orbits.
If we observe several stars orbiting
around an apparently empty point,
a black hole could be leading the dance.
Similarly, light that passes
close enough to an event horizon
will be deflected in a phenomenon
known as gravitational lensing.
Most of the black holes that we’ve found
can be thought of as two main types.
The smaller ones,
called stellar mass black holes,
have a mass up to 100 times larger
than that of our sun.
They’re formed when a massive star
consumes all its nuclear fuel
and its core collapses.
We’ve observed several of these
objects as close as 3000 light-years away,
and there could be up to 100 million
small black holes
just in the Milky Way galaxy.
So should we be worried?
Probably not.
Despite their large mass,
stellar black holes only have a radius
of around 300 kilometers or less,
making the chances
of a direct hit with us miniscule.
Although because
their gravitational fields
can affect a planet from a large distance,
they could be dangerous
even without a direct collision.
If a typical stellar-mass black hole
were to pass in the region of Neptune,
the orbit of the Earth
would be considerably modified,
with dire results.
Still, the combination of how small
they are and how vast the galaxy is
means that stellar black holes
don’t give us much to worry about.
But we still have to meet the second type:
supermassive black holes.
These have masses millions or billions
times greater than that of our sun
and have event horizons that
could span billions of kilometers.
These giants have grown
to immense proportions
by swallowing matter
and merging with other black holes.
Unlike their stellar cousins,
supermassive black holes aren’t
wandering through space.
Instead, they lie at the center
of galaxies, including our own.
Our solar system is in a stable orbit
around a supermassive black hole
that resides
at the center of the Milky Way,
at a safe distance of 25,000 light-years.
But that could change.
If our galaxy collides with another,
the Earth could be thrown towards
the galactic center,
close enough
to the supermassive black hole
to be eventually swallowed up.
In fact, a collision
with the Andromeda Galaxy
is predicted to happen
4 billion years from now,
which may not be great news
for our home planet.
But before we judge them too harshly,
black holes aren’t simply agents
of destruction.
They played a crucial role
in the formation of galaxies,
the building blocks of our universe.
Far from being shadowy characters
in the cosmic play,
black holes have fundamentally contributed
in making the universe
a bright and astonishing place.
