The Worst Way To Cook Spaghetti - EWTS #011

Joe: Hello and welcome to Enough with the Science. I'm Joe.

Senan: And I am Senan. How are you Joe?

Joe: I'm not too bad. Looking forward to this week's episode. And for anybody who is joining us for the first time, basically Senan is a font of all knowledge when it comes to things scientific; and he tries to explain to my tiny brain what is actually going on in the world.

Senan: But the benefit of Joe having a tiny brain is I can tell him anything and he'd believe it.

Joe: Yeah, especially the nice stuff. I believe the nice stuff.

Senan: So, Halloween is nearly upon us. So we should probably talk about monsters.

Joe: No, we shouldn't.

Senan: Why? Are you still worried about them in the darkness of the night? Do you hide under the bed covers?

Joe: I actually... they get worse as you get older. You think like kind of as soon as you stop being a kid you stop believing in monsters? No, they become more real. So you're lying there in bed wondering are they... is there something under me bed? Or keeping me toes in incase something reaches up from under the bed and grabs them. What is going to get you? That's the question. What is going to get you eventually?

Senan: So the bad news is there really is monsters; so you were right to still believe in them.

Joe: There is something wrong with your brain. There is something wrong with your mind.

Senan: And there are millions of them and they are worse than your worst nightmare. The things they can do to you is just... they can lock you up in an inescapable prison; they can burn you up; they can stretch you like a thin string of spaghetti; there's just so many horrible things they can do to you.

Joe: So the monsters we're talking about are black holes.

Senan: Aha!

Joe: That was the longest segue into black holes I've ever heard in my life. But yes.

Senan: And the reason we're calling them monsters is they are the most extreme, largest objects out there in space.

Joe: They're the largest objects?

Senan: That we know of, yeah. The largest single individual objects. And they are also monstrous in their power; they have the most intense gravity you can imagine. And it's that really unbelievably intense gravity that actually makes them so so interesting. And also is the source of all their horrible power.

Joe: And we don't really understand them.

Senan: We understand theoretically mostly thanks to the work of Einstein. But we better go back a little bit. So gravity as I said is their big attribute that they have, the big hammer they're holding behind their back or the big sword they're swinging. I guess it was only when Einstein came along that the possibility that black holes might exist kind of became a real thing. Before that our understanding...

Joe: Just people kept losing stuff. That's where all the stuff that you lose goes. The sock.

Senan: It's all in a big black hole somewhere. Yeah. And that must be a damn smelly black hole. So anyway; imagine before Einstein came along our understanding of gravity was something like what I'm going to describe now. Imagine two magnets on top of a table you're holding them with your fingers and as soon as you let them go they pull towards each other.

Joe: So it's an attraction of some kind.

Senan: Gravity is not magnetism but that was kind of our understanding that you had two objects that had some invisible force that pulled them together. So Einstein came up with this theory of general relativity and essentially he discovered or invented or theorised something called spacetime; he realised that space and time were actually two sides of the same coin.

Joe: So they called it Spime?

Senan: He could, yeah. Most of his work revolved around advanced mathematics. And his mathematics led him to believe that spacetime was like a fabric; and that it could be warped or bent; you could put dimples in it or bowls or whatever you want to call them. But he called it warping of spacetime. And essentially any object that has mass causes some kind of a dimple or a warp in spacetime.

Joe: Even me.

Senan: Even you. You have a very, very small Joe-shaped dimple in spacetime.

Joe: So I have a gravitational pull on tiny things.

Senan: You've got to get away from the idea of pull because it's not a force; it's a warping of spacetime.

Joe: I have a gravitational warp around me. I feel slightly more important now because of that.

Senan: And that basically what we observe as two objects like the moon and the earth being pulled towards each other by gravity is actually a side effect of the fact that the space around those two objects is bent or warped or curved or whatever you want to call it. So what appears to be those two objects being pulled towards each other is just those two objects trying to travel in a straight line but having been forced into a curve by the warping of spacetime.

Joe: So the two... so the moon and the earth... so the moon has its own gravitational warping.

Senan: Yeah. Look, the tides on earth are caused by the moon.

Joe: By the warping of spacetime.

Senan: Effectively, yeah. Yeah.

Joe: Oh my head is beginning to hurt already. So let me just... so if we can imagine for example the earth has caused a bowl shape warping of the spacetime fabric and the moon is like one of those motorcycles in the circus that goes round the wall of death.

Senan: Yeah. Yeah.

Joe: Because that... like the bowl is the wall of death essentially.

Senan: Yeah. So the motorcyclist from his point of view is going in a straight line. But it's just the surface he's riding on is in a curve. So from an outside observer looking at him; he's going in a curve. That's a very good analogy actually for what's going on with with the warping of spacetime. Then when Einstein started following his mathematics to their ultimate conclusion; it seemed to him like it was possible for there to be what he called a singularity; a point in space where there was infinite gravity. Where the warping, the amount of mass that you could gather together in one point, would be so much that you could cause infinite gravity; which didn't make any sense to him. So he basically... that was essentially what started out as the theory of black holes although he didn't believe it was physically possible to have that in space.

Joe: So obviously then the warp of spacetime would just be so extreme that it would... I don't know... it's like a funnel or a tunnel or...

Senan: Yeah. So I suppose the most famous attribute of black holes is that light can't escape from them.

Joe: Right.

Senan: That's probably the reason it's called a black hole is because light is falling into it and never gets out. So it's... the reason that happens is interesting. And it kind of joins in to Einstein's theory. So light is made from photons; like all electromagnetic radiation be it radio waves or X-rays or whatever. And photons are known to be massless. They have no mass, no weight effectively.

Joe: No religion. [laughter]

Senan: Indeed. And so in theory if you assume... it's always been assumed since the time of Isaac Newton that the amount of mass that an object had determined how much gravity it had.

Joe: Okay.

Senan: So the earth is larger than the moon so its mass is greater than the moon so it pulls stronger than the moon does and so on. So that... what follows from that is you would assume that if you have a particle which has no mass, like a photon that light is made from; that gravity couldn't possibly affect it. It should be able to escape. But what's actually going on inside a black hole according to Einstein's theories is that gravity was so incredibly intense in a black hole that space was warped almost into a complete circle so that there was... once you went inside beyond what's called the event horizon; I'll come back to put a pin in that, I'll explain that in a minute...

Joe: Okay.

Senan: Once you went beyond the event horizon which is near the black hole; that space became warped or bent so much that there was no path which led out. Every single path even though the photons in there would be traveling in straight lines; the space was so warped that no path would lead out.

Joe: So they would just keep going round and round?

Senan: Well, they would eventually... all paths would lead in. All paths would bend around until they bent back towards the black hole.

Joe: Okay.

Senan: It's a bit like... I'm going to give you an analogy but it isn't perfect but it might help to understand it or visualize it.

Joe: You're overestimating me. [laughter]

Senan: Imagine you've got a donut that's hollow. So it's a donut...

Joe: I can't imagine any other type of donut.

Senan: No I don't mean the hole in the middle. I mean the bit where the dough is on the inside.

Joe: Okay. On the inside of the donut. Okay.

Senan: Imagine you're in there. If you think about it every path leads back towards the middle of the donut. If you're on the inside surface walking around on the inside surface of the donut there's no path which leads out. They all curve back in towards the center no matter which way you go. So it's kind of like that is what prevents light from escaping; it's essential the geometry of curved spacetime.

Joe: Okay. And so light is sucked in then as well?

Senan: So... oh yeah well obviously if light... imagine there's a beam of light traveling through space minding its own business and it encounters a black hole. Once it gets inside the event horizon; that's it. It's in.

Joe: Okay. The event horizon. There you go. The event horizon is like the bouncer.

Senan: So the event horizon is not... it's kind of a... imagine it's like a sphere or a shell that's outside away from the black hole. So the black hole is like a point in the middle of that sphere. But the event horizon is what we call the place where once you cross the event horizon no light can escape. So that essentially means nothing... light is the fastest... nothing can travel faster than light. So any event that occurs in there cannot be observed from outside. Because light or any other form of information will not get out. So that's why it's called the event horizon.

Joe: So like when you look at an event horizon from a distance it just is a blank space in space?

Senan: Yeah, well look nothing... yeah and it's interesting. That's how kind of the first black hole was discovered. So Einstein didn't come up with the term black hole. There was another guy called Wheeler in 1967 who was kind of working on Einstein's theories and trying to, you know...

Joe: Steal his ideas. I know about it yeah.

Senan: Develop them out a bit further. And he theorised that there might be a region of space with gravity so strong that light couldn't escape. And he said that yes; he called it a black hole. That was his term. And then it was only a few years... so that was 1967 but the actual first essentially proof or observation that tended to prove the existence of a black hole didn't happen until 1971. What's now called Cygnus X-1; the X-1 meaning it's the first black hole.

Joe: Because black hole begins with X.

Senan: X marks the spot. So there was a star they were observing. And it was orbiting in a very tight orbit around something they couldn't see. Now, they can... you can... if you're a scientist and you understand these things; once you understand how heavy, what how much mass something has, and you know how fast it's traveling; you can deduce the size of the thing it's orbiting based on how...

Joe: So there's a formula for that.

Senan: Yeah, yeah probably a very long one with lots of Xs and Ys and Js and Ts in it. Anyway, they were observing this star and it was obvious from the way it was behaving that it was orbiting something really enormous. Like really, really something with a huge amount of mass; huge amount of gravity. And yet they couldn't see anything. This star was apparently orbiting an empty area of space. So that was kind of the first observation or proof that black holes did exist.

Joe: So it had to be... it was so big that it should have been visible but they couldn't see anything.

Senan: Oh I mean if it was a star it would have been really, really bright. Much brighter than the other star they were looking at. So the only thing that might have had that amount of mass that might have been that size would have been maybe another very, very massive star. So that was kind of the first; and since then obviously we've found a lot of them. And there's some really interesting statistics about how, why they are monsters. So...

Joe: Oh good.

Senan: We have since discovered that most galaxies have a black hole in the centre of the galaxy that essentially everything else in the galaxy is orbiting around. Now...

Joe: Plughole.

Senan: Yeah there's some galaxies that don't have that kind of shape of... that there's obviously things orbiting around in a circle, you know, or an ellipse of some kind. The one that's at the centre of our galaxy we've called it Sagittarius A. It is four million times heavier than our sun. Right? So that's a pretty big object. Now people might be wondering how heavy is our sun? Our sun is three hundred times heavier than the earth.

Joe: Okay and so do the maths there...

Senan: Four million by three hundred... our sun is three hundred thousand times heavier than the earth. Did I say three hundred? I did. Sorry that was a mistake. I meant 300,000.

Joe: I thought wow. Only a little sun.

Senan: And so like it's... Sagittarius A, our local black hole for want of a better description, is absolutely enormous. Four million times bigger than our sun.

Joe: And like did they... did we know where the centre of our galaxy was before we found the black hole?

Senan: Yeah I mean it was obvious from observations that the galaxy was rotating around something. But you know, didn't know what was the source of that. But I'm not finished there with the statistics. Some of the biggest...

Joe: Oh good. You can't wait for the next statistic.

Senan: I'm on the edge of my seat here.

Joe: Okay good. Let's go. Size. Let's go.

Senan: Some of the biggest black holes based on what we've observed in the very far away universe could be up to fifty billion times the weight of our sun. So that begs the question how in God's name do these things form in the first place?

Joe: But like it's just so unimaginable. You know; you're dealing with numbers... like first of all a billion, that's unimaginable. Fifty billion. Like the size of our sun is pretty unimaginable and then multiplied by fifty billion. You're just kind of going...

Senan: Oh yeah yeah. I mean those are numbers our brains can't comprehend. But just large; extremely large. The definition of big.

Joe: Monstrous if you will. If you're going to persist with this analogy for Halloween.

Senan: Well, you know as a man of science I try not to believe in monsters but the evidence that they're there unfortunately exists. So how do they get formed in the first place? A star... they form from collapsing stars. Now not every star ends up being a black hole. You've got to be bigger than a certain size. So we believe that a star has to be at least twenty times bigger than our sun before it's capable of creating a black hole at the end of its life.

Joe: Okay. That's kind of comforting.

Senan: So stars end their lives in various ways; some of them go supernova, some of them turn into brown dwarfs. But some of them by virtue of the amount of stuff that's in them, how big they are, will turn into black holes. And how that happens is interesting. So those stars typically might be a couple of million kilometres in diameter. Pretty big things. You know even our sun is is in the region of I think it's about three hundred thousand kilometres in diameter. Anyway. The nuclear... stars shine brightly because there is nuclear fusion taking place. So what's happening is there's a huge amount... there's an awful lot of material, stuff, gathered together in one tight ball. And the gravity that that material has is so strong that it's squashing all the atoms together. And that causes something called fusion which essentially means that lighter elements like hydrogen and helium are being squished together until they become heavier elements like carbon and various other things, silicon and what have you. The process of fusion releases energy. And that energy has outward pressure. So that pushes against the gravity that's trying to collapse all the material the star is made of. But and they're evenly balanced. So while the star is burning throughout its lifetime the amount of outward pressure from the fusion is balanced against the inward pressure from the gravity which is causing the fusion in the first place. Everything's hunky dory, right? Everything is stable.

Joe: So keeps... so it explodes things out and then drags them back in and squishes them down and then explodes them out again?

Senan: No it's not a pulsing thing. It's a smooth continuous amount... so the fusion is taking place continuously and there's a constant outward pressure caused by the energy from that fusion and that's counteracting the inward pressure from the gravity which is causing the fusion in the first place. But the point comes where the star runs out of fuel. In other words all the helium and hydrogen and whatever else it is fusing is used up.

Joe: Okay.

Senan: And something really really dramatic happens. Remember we're talking about very big stars now; at least twenty times the size of the earth's... of our sun. In less than a second from the point... it's like flicking a switch; from the point that the fuel is extinguished the star collapses into a black hole. Less than a second.

Joe: Less than a second? Now this is theoretical.

Senan: Oh yeah well obviously... I believe they have observed it happening all right in distant stars.

Joe: It's like... it must be just a light switch, like a big light switch just going off. It's just like it's there; everything's hunky dory; then it's gone.

Senan: Yeah. Yeah. Of course its gravity is now multiplied because all that material that was spread over the full million something... couple of million kilometres that were the diameter of the star is now concentrated into an area you know, that's maybe only a thousand or two thousand kilometres. It's all been squished down. And that is what causes the intense gravity because all that matter is now in such a small space. And like they all start off... all the black holes start off as baby black holes we'll call them. Relative... you know the mass of one star. Be it a very big star but relatively small. But what happens then of course is they have this huge intense gravity at their disposal and anything that passes near them gets pulled in and gets added into the mass. Even other...

Joe: No, they don't get pulled in. Like kind of the warp in spacetime it just like kind of... it travels in a straight line round a...

Senan: You were listening! That was a test I wanted to make sure you were listening.

Joe: I was.

Senan: So yeah. So even other black holes. And actually if I could digress for a minute; a few years ago a very advanced experiment that was set up in the States called LIGO detected gravity waves. So never before... it was theorised that there could be gravity waves passing through spacetime; essentially ripples in spacetime that were being propagated out like waves in the sea. But it was detected for the first time ever by LIGO a few years ago when two black holes merged. So what happened was as they approached each other their angular momentum meant that they didn't just smack together; they actually started orbiting each other tighter and tighter and tighter and tighter and at a ridiculous speeds like they were orbiting each other like a hundred times a second. And that movement of two extremely dense gravity heavy bodies around each other created ripples that propagated out; all across the universe. So this merger occurred like millions of light years away from here; but yet this detector was able to detect gravity waves for the first time ever resulting from the merger of two black holes. So that's part of how they grow; they not only do they pull in stars and planets and any other dust or gas that they can find but they will also pull in other black holes that are nearby.

Joe: Now this... these gravity waves that were just in that particular experiment; like this is something that happened millions of years ago.

Senan: Oh yeah, they travelled at the speed of light. So if it was a million light years away then the event would have happened a million years ago yeah.

Joe: And so the guys who built these tunnels theorised that this was...

Senan: Oh yeah it was a theory that gravity waves were possible yeah.

Joe: I just am just amazed that they could make this stuff out of Lego.

Senan: I should know what LIGO stands for, I can't remember.

Joe: Long Interesting Tracking...

Senan: Well it's funny enough long features in it because you've got these really long tunnels like hundreds of metres long; two of them at right angles; actually couple of kilometres long I think. Two of them at right angles to each other. And they fire a laser beam from... there's a point where they meet. And they fire a laser beam up each tunnel; there's a mirror at the far end and they measure how long it takes for the light laser beam to come bounce back again. And they know what the speed of light is; they know what it should be. So what happens when the gravity wave passes through our region of space is everything gets very very slightly stretched or squeezed. Now we're talking about say the distance from here to the sun; it might alter the distance from here to the sun by like the width of a human hair. We're talking about a really tiny amount. But in one of the tunnels 'cause the tunnels are at right angles from each other one of them stretches a certain amount and the other one squeezes the same amount and vice versa. So that's how we detect the waves passing through. So actual everything was momentarily stretched and squeezed; including you and I when that gravity wave passed through.

Joe: And is... like was it something that was just a wave passing through and they caught the wave or was it a group of waves that like over several...

Senan: Oh it was a set of waves yeah. So every time those two black holes before they merged orbited around each other one wave went out and then another one then another one then eventually... and the waves got... they were able to detect the series of waves passing through and they got... they could measure them getting faster and faster and faster because the black holes were getting closer to each other and spinning faster and faster and faster so the waves...

Joe: So the guys who built these tunnels theorised that this was...

Senan: Oh yeah it was theory that gravity waves were possible yeah.

Joe: And since that... they have built more sensitive ones since and they've detected plenty of other occurrences of gravity waves since. Wow. It's just one example of the extreme physics that black holes are presenting to us. So yeah, the event horizon we spoke about that. Spaghettification.

Joe: Spaghettification.

Senan: That's a scientific term believe it or not.

Joe: You didn't make that up? Are you sure? I'm going to check that later.

Senan: I didn't. It refers to stretching. So the whole point of that word is that in the gravity is so extreme around a black hole that there's a gradient of gravity. And there is a gradient of gravity anyway so you know; when you're near the earth the pull of the earth is much stronger than when you're far away from the earth. So the further away you get from any object the less is the strength of its gravity; its pull on you.

Joe: Or the less warp is in the space fabric of spacetime. There you go.

Joe: I hate to have to correct you on these things.

Senan: You know what? I think the roles are reversed here. Off you go. You do the rest of it and I'll... [laughter].

Senan: So there's a gradient. But the gravity is so extreme around a black hole that the gradient is much tighter. So that means that for example there's a point; a smallish black hole; about a thousand kilometres away from the black hole the gradient gets so strong that there's a big difference between the amount of gravity that would be on your head versus your feet. So over a two metre length of an average human body it would be much; if your feet are towards the black hole it would be much stronger pull on your feet than on your head and your body would start to stretch. And it would just keep stretching. Now probably after it has stretched twenty percent or so you would just disintegrate 'cause your body isn't capable of stretching and you'd probably be well dead by then.

Joe: Imagine... the stretching is the least of your worries if you're in that scenario.

Senan: But if you were made from something that was much stretchier like rubber or something; the stretching would just keep going, keep going. You'd be stretched out into a long string of spaghetti.

Joe: Has anybody ever survived this?

Senan: Nobody that we know of has ever fallen into a black hole. Thankfully there's none anywhere near us that we know of. As I said the one at the centre of our galaxy, the nearest I think that we know about, is Sagittarius A at the centre of our galaxy and that is about twenty five thousand light years away from us. So it's a long way.

Joe: You'd think that was a safe distance. You would think.

Senan: So how do we... it's become... we've realised there's an easier way of observing black holes than just seeing what it's doing to some star that happens to be going around it.

Joe: In movies. You watch them in movies.

Senan: That's true. Like Interstellar. And that is something called an accretion disk.

Joe: Oh wow. Because we were talking all about secretions last week.

Senan: Yay. A secretion disk is a big different thing I think. So an accretion disk; so it accretes material. So the stuff that's going to fall into the black hole usually doesn't fall straight in because it's not going at... it's traveling through space at an angle to the black hole and suddenly it comes within the influence of the gravity and it starts to curve around and goes into a kind of an orbit around the black hole. And it spirals in until it eventually is going to fall in and become part of the black hole. But it spends quite a long time rotating around, orbiting around. So you've got this; what happens is this disk of material builds up in orbit around the black hole, all the stuff it's sucking in. And the huge gravity involved starts accelerating that stuff. So it starts to move faster and faster and faster as it moves in towards the black hole. And you get a lot of friction; it starts hitting off all the bits and pieces of it start hitting off each other. If there's planets or stars involved they probably have their own magnetic field so all that magnetism is churning around in there as well and there's real maelstrom of chaos. And the material heats up enormously. It heats up to millions of degrees and starts to glow.

Joe: So this is visible then?

Senan: Yeah so we see this; we have directly imaged at least one black hole with by looking at this dull orangey red ring around it. So that's a new way for us to observe black holes. And the accretion disks like the heat and they're emitting X-rays, they're emitting all kinds of radiation because of the extreme violence of what's going on in there. And does the accretion disk; is that a feature of every black hole or they burn out after a while or...?

Senan: Well any black hole that is sucking in any significant amount of material is going to have an accretion disk. Now some black holes are probably in places where there's nothing near them and then you don't; like you know you wouldn't see that. You wouldn't know it was there unless you were able to observe the effect it was having on some other nearby object. So yeah. And those accretion disks are... another one of Einstein's theories is that matter and energy are just two different forms of the same thing. And they're actually able to convert up to about forty percent of their matter into pure energy that radiates away as X-rays or whatever before it falls into the black hole. Like there's so much violence going on in those accretion disks.

Joe: So the accretion disk is outside the event horizon?

Senan: Yes, correct yeah yeah. 'Cause we wouldn't see it if it was inside it. Now there's probably a part of it inside the event horizon that we can't see, you know. So that's another very interesting piece of physics that's involved. And then you've got these things called relativistic jets which are something that occurs at the poles of some black holes. Now it's still outside the event horizon so it's material from the accretion disks that is interacting with the magnetic field. Now this is highly theoretical; this is they're not well understood. But they've been observed.

Joe: You do know; you just can't give us the information.

Senan: They've been observed like people can see them but the reason, how they occur is not fully understood. Essentially they're like a beam of particles of high energy particles that's shining like a lighthouse shining out of the pole, the north and south pole of the black hole. By pole I mean so pretty much every object in space is spinning and black holes are spinning too so the poles are obviously the top and bottom of in relation to the spin. It's theorised that the extremely strong rotating magnetic field of a black hole at its poles is interacting with the material in the accretion disk and is accelerating it up to over ninety percent of the speed of light. It's the fastest... obviously photons light travels at light speed but anything that has mass; and these particles that are in the accretion disk have mass; they're being accelerated up to ninety percent of the speed of light. It's incredible. It's the fastest moving things in the universe. Like really incredibly fast.

Joe: Over huge distances.

Senan: Oh and they're squirted out over massive distances like thousands of light years they some of them could be squirted out from the north and south poles. And can they use this to detect black holes then?

Senan: Good question. I'm not sure how they observe them. I'm not sure how but perhaps; but I'm just we're getting beyond the edge of my event horizon now there.

Joe: You do know you just can't give us the information.

Senan: So like there's just so much fantastic physics going on around black holes. They are... our theories which are based on Einstein's general relativity just break; the mathematics just breaks down when you get into the region of a black hole. So they really are a mystery for physicists because our understanding of physics that we can see in operation in the rest of the universe just doesn't occur inside a black hole. There's something weird going on in there. It's theorised that we might need something called a quantum theory of gravity to explain what we see going on inside black holes because well or what we, you know what we seem to be going on in there. And there's just so many other, so many other things that I didn't touch on called for example Hawking radiation which is essentially a theory that says that black holes will gradually evaporate. Even though originally we thought nothing could escape from a black hole; this theory is now accepted as very likely to be true and that very slowly that black holes evaporate particles off their surfaces back into space. But it would take trillions of years for one to actually completely evaporate.

Joe: So what would happen if I just happened... I was out for a stroll in one of the nether regions of space and happened to walk into an event horizon?

Senan: What would happen? Well I mean once you cross the event horizon that's it; you're not coming out.

Joe: Right. So it's like a bar.

Senan: From the point of view of an outside observer; because of the warping of spacetime—remember I said Einstein established that space and time were both two sides of the same coin; an outside observer not at the event horizon watching you fall towards it would see you slow down, slow down, slow down until when you reach the event horizon you would freeze; just solid; and you would then kind of turn a weird red colour and fade away slowly into nothingness. From your point of view none of that would happen. You would not be aware of any slowing down; you would not be aware of any freezing; you would cross the event horizon, everything would feel normal to you and you would continue on towards the black hole. Now at some point depending on how big the black hole is you would be spaghettified by the extreme gravity. Either that or cooked by the accretion disk.

Joe: So the spaghetti analogy just keeps giving.

Senan: So yeah it's weird that time effectively, from the point of view of an outside observer, stops at the event horizon whereas for the person at the event horizon it doesn't; all down to the warping of spacetime.

Joe: Speaking of time stopping; I think it might be time to stop this episode of Enough with the Science.

Senan: Yes indeed. We've probably done enough time bending for today and you know hey; if you've got any energy left by the time you have finished listening to us maybe you might give us a review on your favourite podcasting platform. It really helps us.

Joe: And do join us next time on Enough with the Science. We're going to fade away over event horizon now. Bye.

Senan: Yes I can see the black hole coming. Have a nice day.