WEBVTT

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there's a supermassive black hole the

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center of every galaxy yeah there is

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also other black holes that aren't

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necessarily in the center of galaxies

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yeah so these little ones a little they

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a few times the mass of the Sun and

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they're from collapse tiles so they are

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stars at the end of their life very

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bigger than the Sun more massive than

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the Sun but they run out of their fuel

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and they start to collapse because

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gravity squashes them and if they're

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sufficiently massive then there's

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nothing that can stop the collapse and

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so they collapse as far as we know to a

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point right essentially an infinitely

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dense point we don't really know what

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happens at we don't know what happens

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right in the middle but they collapse to

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such an extent that there's a region

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around it where from which light can't

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escape and that's a so nothing can

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escape and that that's a black hole and

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what happens to them do they travel are

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they moving through space yeah they're

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still stars right you know so they

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they're still there they're surrounded

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this region where have you fall in it's

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called the event horizon and if you go

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across that horizon then you are going

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to the center there's one way of

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thinking about it which is quite cool

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which is that the time and space sort of

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flip is one way to think about it so in

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the same way that we are going into the

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future now so we're going to tomorrow

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there's nothing we can do about it we

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are going to tomorrow in the same way if

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you fall in across the event horizon of

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a black hole you are going to the middle

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the singularity is called so that's

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that's your future every every line of

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your future points to the center of the

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black hole so it's kind of the ultimate

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I've no escape for the ultimate prison

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you're gonna get squashed to an

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infinitely dense so point not every star

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becomes a black hole at the end of its

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life no because if something like the

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Sun and we have a small star it's quite

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small yeah and when it collapses there's

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a there's a sort of pressure a force if

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you like which is caused by the fact

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that electrons don't like to be very

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close to each other

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so it's called the Paoli exclusion

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principle but essentially what happens

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is that so as they get squashed closer

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and closer together they move faster and

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faster to get out of each other's way if

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you like and that makes a force which

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holds them up and so that creates what's

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called a white dwarf star so you can

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have a blob of matte so they're about

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the size of the earth but they're about

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the mass of the Sun and so that's that's

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for smaller stars they end up as these

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white dwarf things which are very dense

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objects there's another version which is

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called a neutron star which is the same

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thing but for neutrons and they they

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move faster and faster so if it's if

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it's massive enough that it overwhelms

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the electron thing and the electrons

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sort of fought crush into protons and

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turn into neutrons and the whole thing

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starts again and so a neutron star can

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be you know elite one-and-a-half times

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the mass of the Sun let's say but it can

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be about what 10 miles across so so

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that's an incredibly dense ball of

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matter held up by this the neutrons

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moving around it's got a fancy name it's

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called neutron degeneracy pressure with

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ice in it but if you go even bigger then

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even that can't hold it up and as far as

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we know then there's no known force that

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we know of that can hold hold the thing

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up if it's too massive and so that's

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when it just almost winks out of

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existence if you like oh it collapses

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and collapses and collapses and that's

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when you get a black hole we try to put

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that in a perspective of the earth the

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Sun is a million times bigger than the

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earth yeah and this this neutron star is

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would you say one and a half times the

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mass of this yes miles wide yeah yeah

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certain little loads of those around

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that they call pulsars so we see those

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all over the place though the first one

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that was discovered was called lgm1

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because they spin very fast and then it

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was called lgm1 because it's a very

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regular pulse and they thought it was

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little green men because it kind of

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jokingly a little green men one and then

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so yeah we've seen that there's one

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called the crab pulsar which is in the

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Crab Nebula which we saw the supernova

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explosion so that's when one of these

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stars explodes at the end of its life

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and then collapses to form a neutron

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star and we saw that

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1054 ad well it wasn't there some

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speculation that our gal or our solar

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system at one point was had was a binary

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star system and that one of those stars

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had become a dwarf I don't know and

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someone had read something about that in

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relationship to the dense object they

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believe is outside the Kuiper belt yeah

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I mean there's some evidence there's a

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bit of evidence that there's something

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out there yeah yeah because of the

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periodic extinctions and things on earth

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like you get periodic bombardments from

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out in the Kuiper belt so yeah I think

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one of the theories is realloc

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extinctions well yes so for like the you

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know that they've been there have been

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mass extinctions on earth when a lot of

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the life died and then we don't know

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what caused all those but sometimes

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their impacts from space that seems

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clear and so yeah there are theories

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that there's something orbiting out

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there which can disrupt all these

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objects out in the Kuiper belt that

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sends loads of comets and asteroids

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inwards to the inner solar system I

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think cause havoc and so that there's

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some people look at those theories