Hey, Vsauce. Michael here. This symbol, commonly called a Yin Yang symbol, is a taijitu meaning diagram of the supreme ultimate. The principal of Yin and yang, opposites existing in
harmony, is associated with ancient Chinese
philosophy. But the very first use of the iconography,
the classic symbol, actually comes from a shield pattern
used by the ancient Romans seven hundred years before its first known use in China.
A connection between the two has yet to be found.
Regardless of who came up with it first, the symbol was a bright idea.
But what’s the brightest object in the entire universe? Well, apparent magnitude. Commonly used when stargazing refers to
how bright an object appears to us, say, when looking up from Earth. It depends on Earth-centric factors,
like how close the object is to our planet. Magnitudes are logarithmic and arranged like golf, where a smaller number means a greater brightness. But today I’m looking for absolute magnitude, a measure of how bright things all over
the universe near and far would be if we looked at them
from the same distance. Absolute magnitude will guide
us to the most blinding light in the universe, irrespective of it looking faint to us here on Earth, just because it’s far away. The difference is significant. A 100-watt light bulb placed closer than 8 centimetres – about
3 inches – from your eye will appear brighter than the Sun in the sky. But that’s not fair. If you could see the Sun and the bulb from the same distance, the Sun would be
a septillion times brighter. That’s bright. But the Sun shines punily compared to the rest of the cosmos. If you could line the Sun up with
everything else out there, giving every star and cosmological
phenomenon a fair chance, the Sun’s absolute magnitude would be 4.8. Not bad. But check out R136a1. This nuclear fuelled beast isn’t the biggest star in terms of volume but it’s 256 times more massive than our Sun.
It’s the most massive star ever found and it’s also the brightest. Remember that lower absolute
magnitudes are brighter. R136a1 isn’t 4.8, like our Sun, it is -12.6, which means it is 8.7 million times brighter than our own Sun. But R136a1 isn’t the brightest thing out there.
When a giant star dies, it explodes violently in what is known as a supernova or hypernova. As I mentioned in my video ‘How Hot Can It Get?’,
supernovas can eject terrifying flashes of radiation known as gamma ray bursts.
Arguably, the brightest electromagnetic events in
the universe. A typical gamma-ray burst releases as much energy in a few seconds as our Sun will release altogether in its entire 10 billion year lifetime. If WR104, a gamma-ray burst future candidate, directly struck Earth with such a beam for only 10 seconds astronomers predict it could deplete 25% of our ozone layer and lead to mass extinction and starvation. The largest thermonuclear bomb ever detonated didn’t do anything close to that and it
was exploded right here, in our atmosphere. Whereas WR104 is eight thousand light years away.
You can’t even see it with your naked eye or a pair of binoculars.
But gamma ray bursts are merely brief events lasting only a few minutes at most, sometimes just a matter of milliseconds. If you want the brightest sustained thing, you’ll paradoxically have to look at the darkest thing. Black holes. To be fair, dark matter is ostensibly darker. But because dark matter has been hypothesized to not even interact with light, with electromagnetism at all, calling dark matter “not bright” is kind of like calling your peanut butter sandwich “a not fast airplane”.
It’s not really even in the same category. Black holes, however, do interact with light; reflecting so little, well, they don’t let any escape, at least not in a form resembling the way it came in. That’s dark. But the intense energies created by
black holes in the process of eating things like stars is anything but dark.
Gas and debris from the stars they eat swirl into arcipluvian cosmic gallows known as accretion discs before making their final death plunge
into the black hole. In the disc, debris spins at unfathomable
speeds, pulled around by a black hole billions of times more massive than our Sun.
Friction in the accretion disk generates heat on a level difficult to fully appreciate. Just as hot things glow, the disk does too. So brightly it has its own name. A quasar.
Quasars shine thousands of times more brightly than even the brightest stars. I’m kidding, it’s scarier than that.
Quasars shine thousands of times more brightly than galaxies containing billions of stars. The first identified quasar, 3C 273,
has an absolute magnitude of -26.7, making it four trillion times brighter than our Sun, about 100 times more luminous than the
total amount of light produced by the entire Milky Way. If you put 3C 273 33 light years away from us it would
shine as brightly as our Sun – a mere 8 light minutes away.
Blocking the brightness of a quasar with the corona graph reveals that quasars exist in the
centers of galaxies that are larger than them in area, but are, nonetheless, drowned out by their light. Such galactic centres are called active galactic nuclei. The bulk of their energy spewing forth
in the form of a powerful radiation jet, the length of which puts even our solar system to shame.
The visible part of the jet in this photograph, for instance, is so
long it could stretch from the Sun to Pluto and back, one-and-a-half million times. Now, specifically, if a large portion of
this ajected energy heads toward Earth, it’s responsible for what we call a quasar. But if Earth is right and the active
galactic nucleus’ sights, it’s got a scarier name: a blazar. And it’s blazar 3C 454.3 that clocked
in the greatest brightness ever observed.
At historically high levels of activity it registered in absolute magnitude of -31.4. To put the brightness of quasars in yet another perspective, take a look
at the one hundred thousandth picture snapped by the Hubble telescope. This is a star a few hundred light years away. And this thing looks just about as bright, but it is a quasar. 9 billion light years away. Why are quasars so far away? Well, a quasar is not forever. They are billions of light years away, which means the light we receive from
them, the pictures we take of them, are pictures of things happening
billions of years ago. They represent a phenomenon more common early in the universe’s history, when
monster black holes hadn’t eaten all the stars around them to fuel their
accretion discs and before those holes became too fat to be active. Neil deGrasse Tyson points out that in order to remain a quasar producer, a black hole must consume about 10 stars a year. Many consume more than a thousand stars a year, 600 Earths worth of matter every single minute. The more stars a black hole consumes,
the larger its event horizon becomes until, eventually, it no longer shreds stars apart to fuel an accretion disc.
Instead, it just swallows them whole in one dimmer, but still terrifying, gulp. Quasars are some of the most
ancient things in our universe. If you could teleport instantaneously to one right now faster than light, it would most likely
no longer be burning. What we see are just their ghosts. Light that left when they were active that traveled longer than they could live. But quasars can still be born. They can even be born right here, in fact. In my video ‘What Will We Miss?’ I pointed out that
the Andromeda Galaxy is headed our way. In 3 to 5 billion years it will collide with our own galaxy, the Milky Way. And the collision could rearrange stars near the
galaxy’s central black holes to be consumed, reigniting a quasar right here, in our galactic backyard. Funny enough, right now very few of us even see Andromeda, even though all you
need is your unaided eye. Light from our cities drowns out the night sky like a quasar drowns out its host galaxy. Artist
Thierry Cohen mocked up what big cities would look like if all their lights were off and the sky above them could be seen fully. New York, Hong Kong, Shanghai, Tokyo, Los Angeles. It’s beautiful and rare. In the 1990s, during a blackout in the city of Los Angeles,
a number of residence actually called the police they were
afraid of mysterious glowing clouds hovering above the city. They were seeing our galaxy for the first time in their lives. At night, artificial lights allow us to see what’s around us but we lose what’s above us. The brightest places have the darkest, emptiest skies. There’s Yin and Yang again. A taijitu
has actually been lurking in this video the entire time. The brightest things in the universe, quasars, are caused by the darkest things in the universe – black holes. The process that unshackles the most light is caused by the thing that best imprisons it. And as always, thanks for watching.