Black holes are going to kill you and everyone
you love. Well, maybe. As one of the most powerful forces in the
universe, black holes were originally believed to be a myth for centuries, and were only
recently proven to in fact exist by modern science. Way back in 1687, Newton blew the mind of
every scientists alive when he dropped his famous book, Principia. When earth's scientists were done scooping
their brains back inside their skulls, they discovered that Newton's three-volume work,
Philosophiae Naturalis Principia Mathematica, had mathematically described the laws of motion
and universal gravitation. Then a hundred years later a British monk
by the name of John Michell used Newton's own math to deduce that there might in fact
be an object so massive that matter would need an escape velocity greater than the speed
of light in order to escape its gravitational attraction- a physical impossibility. This didn't jibe well with the scientific
establishment, and in the 1900s even Einstein joined in on the anti-black hole bandwagon. Then in 1970 scientists discovered Cygnus
X-1, which was at the time the best candidate for a real-live black hole, and in 1994 the
Hubble telescope took photos of stars orbiting at incredible speeds near the center of their
galaxies, indicating an invisible supermassive object. Then, following the age-old adage of “picture,
or it didn't happen”, scientists managed to photograph a black hole for the first time
earlier this year. We'd love to say that this for sure settled
the debate on the existence of black holes with even the most die hard unbelievers, but
well, there's hundreds of thousands of people around the world who still believe the world
is flat. This picture of a black hole was taken from
the galaxy M87, and shows a supermassive black hole at the heart of the galaxy with a mass
of 6.5 billion of the earth's suns, and with a diameter of 24 billion miles (38 billion
kilometers). The black hole is so big, that if you were
to try to cross it by a modern jetliner... then you would instantly be disintegrated
because nothing can enter a black hole and survive. That's because a black hole's gravity is greater
than any force known or predicted by science, and there's simply no escape once you're caught
inside it. That includes light, which is why the photo
of the black hole inside galaxy M87 is only possible due to the superheated gas and material
that is stuck around its event horizon- the point of no return. The intense gravity causes this material to
spin so quickly that it heats to incredible temperatures, and makes the edges of a black
hole visible to X-ray detectors. Not content to let these galactic monster
lie dormant, scientists have continued to press on in their quest to understand black
holes, and one of their leading questions was: just how fast do these monsters really
spin? The answer turned out to be, really, really
fast. Measuring the spin of five different supermassive
black holes, all safely located around 10-11 billion light years away from earth, scientists
discovered that the event horizon of one of these giants was spinning at just shy of the
speed of light, 670 million miles an hour (1.1 billion kph). Turns out that this particular black hole
was an overachiever though, and the other four black holes were only found to be spinning
at about half of that rate. One of these black holes however had a large
spinning vortex of material, known as an accretion disk, which was found to be spinning at a
vomit-inducing seventy percent the speed of light, which might just make it some of the
fastest moving material in the universe. But you can rest your fears about black holes
to rest, because the truth is that, despite popular opinion, black holes are actually
pretty safe stellar phenomenon. That's because black holes don't really 'suck
in' objects, but rather have a gravitational influence that catches wayward objects. As long as you stay outside of its gravitational
influence, you and your space ship would be perfectly fine. Even if you managed to get inside its gravitational
field though, most matter is spun around with so much force that it is ejected back out
into space. Only a small percentage of matter actually
manages to reach the event horizon, where its fate is doomed. If your ship reached this point, then you're
in some serious trouble. As you approach the black hole the gravity
is so intense that the gravitational force your feet experiences is far greater than
your head, and so your body would be stretched out at the atomic level in a process scientists
have termed, 'spaghettification'. The good news is though that time itself would
be warped by the intense gravity, so much so that it would actually move at a fraction
of the speed it moves for the rest of the universe. So as you fell inside the black hole your
own personal perception of time would slow to a crawl, and if you were to look out at
the universe you would see the rest of the universe moving along at normal speed- so
as you're slowly being sucked into a black hole you would actually be able to watch the
universe evolve over billions and billions of years. Well, you'd be able to do this if you weren't,
you know, a long string of atoms being slowly ripped into their fundamental particles. So just stay out of a black hole and you're
safe, right? Well, remember how at the start of this episode
we told you a black hole was going to kill you and everyone you love? That was only half-wrong. Most black holes are so massive that they
hold the rest of the galaxy in place around themselves, all the stars and their planets
orbiting around what becomes the galactic core. The stars are caught in the black hole's gravity
field, but due to their velocity are safely kept in orbits that never bring them close
enough to be consumed. Therefore, relative to you and me, the black
hole at the center of our own galaxy doesn't move- it never gets any further or closer
away from us unless our own orbit is highly eccentric. Not all black holes play by the rules though,
and some black holes are galactic wanderers. While scientists don't believe that supermassive
black holes are capable of being galactic wanderers, many smaller black holes are believed
to be right now roaming space, devouring everything they come across and totally invisible as
they stalk the heavens above. Black holes may be huge sources of gravity,
but they too are affected by the gravity of other objects- thus smaller black holes can
be ejected from stable orbits by interactions with other sources of gravity, and set them
on a collision course with stars, planets, and maybe, possibly, one day you and me. Such an encounter would be extremely rare,
and probably doesn't warrant much panic- but some scientists have hypothesized that the
earth encounters much, much smaller black holes the width of a human hair, at a rate
of about 1 per 1,000 years. These are remnants from the Big Bang, formed
in the first nanoseconds of all creation, and whizzing through space like cosmic bullets. While these shrimpy black holes most likely
don’t exist and certainly won't be able to destroy the earth, if one were to cross
your path the incredible tidal effects on your body might just kill you. So don't worry, because black holes aren't
going to kill you and everyone you love. Probably. Maybe. How would you save the earth from a rogue
black hole? Let us know in the comments! And as always if you enjoyed this video don't
forget to Like, Share, and Subscribe for more great content!
