The End of Earth

The End of Earth

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This episode is brought to you by Brilliant.   Some say the world will end in fire, Some say in ice.   From what I’ve tasted of desire I hold with those who favor fire.  

Welcome to Science & Futurism with Isaac  Arthur as we celebrate our 300th episode   and take a look at how the Earth might come  to an end, and we will be covering a range   of options from natural to artificial, near term  to far future, fiery to frozen. There are a lot   of options, and this channel is not noted for  any compulsion for brevity, especially for our   300th episode special, so we’ll be here for a  bit and grabbing a drink and snack is advised.   Fiery and frozen endings are probably the two  most popular end of the world scenarios for   contemplation, and we opened the episode with  a quotation from famous poet Robert Frost’s   classic, “Fire and Ice”, and for anyone whose  curious Robert Frost is my favorite poet   and Fire and Ice one of my favorites by him.  There’s two reported inspirations for the poem,  

one being Dante’s Inferno and the other being a  conversation Frost had with an Astronomer about   the Sun exploding or extinguishing. Now that poem was written back in 1920,   and the popular notion for the fate of stars  at the time was that they were hot for the   same reason planetary cores are hot – they heated  under the immense gravity of their own formation   and have been slowly cooling. Such being the  case, stars would die off by slowly cooling and   dimming and the worlds about them by freezing.  Another notion that sometimes made the rounds   was that there was a limit how many times a planet  could make the rounds of its star, that its orbit   would eventually decay from friction with gas  and dust and perturbation from other planets.  

In such a scenario the planet falls  into the Sun for a rather fiery death.   Later we found out that their heat was being  replenished by the process of fusion, and that for   most stars as that fuel runs out they expand and  burn their inner solar system, and our knowledge   of that has been improved and corrected upon  since and we will discuss it as one option today.   And I do mean option because as we will see today,  even if the current modern theory is correct,   there are several other competing options and  scenarios for ending Earth in whole or part.   But while the notion of gravitationally heated  and slowly cooling stars was one of the first   serious scientific stabs at the end of the  world, it’s long been a topic of philosophical   and theological discussions. We will not be  discussing theology today, but it is always   striking how often various end of the world  scenarios suggested by science, and folks worry   over the most, seem to line up with those we find  in various religions, mythologies, and folklore.   Whether it is prophetic or gives an insight  into human psychology I obviously can’t say,   but as we do go through options today that  represent fiery or frozen ends, or which   resemble some other apocalyptic scenario like Grey  Goo self-Replicating Robots being analogous to a   swarm of locusts, we should keep in mind that  which end of world scenario is most poetic is   probably not relevant to which is most accurate. The other thing to keep in mind is that the End  

of Earth is not synonymous with the End of  Humanity. Humanity might venture off to other   worlds and burn Earth to ashes with our rocket  flames, metaphorically or literally. So too,   a virus might wipe out every human,  or an artificial intelligence might,   while leaving Earth otherwise untouched. For today though we will speak to both options,  

end of Earth and End of Humanity, and at times use  them interchangeably, though planet or biosphere   wrecking events are our main focus. Indeed  we can have multiple endings in this context,   as a planet whose biosphere was obliterated to  the point only a few bacteria remained might be   fully rejuvenated in a billion years, just in  time for the oceans to boil off into space.   We’ve got nuclear war and Nuclear Winter to  consider, Global Warming and Global Cooling.   We have Grey Goo, Planetary Disassembly for  building materials, planetary self-sentience,   consumption by a black hole in our core or  freezing if a black hole got in our Sun’s core   or a black hole or some other large body perturbed  Earth’s orbit and ejected us from the solar   system. We’ve got a warming sun boiling off our  oceans and atmosphere in a billion years or so,   or an expanding sun swallowing our planet in a  few billion more. We’ve got collisions with other  

planets or even our own moon dropping on us, in  a reverse version of the event we think scattered   the debris that our Moon eventually formed from. We have artificial scenarios to extend us past   these, like re-terraforming our planet if we  sterilized it with nukes, warming or cooling   it with solar mirrors and shades, if it boiled or  froze, moving it away from our Sun if we needed   to, as the Sun aged, or refueling or filtering our  Sun to extend its own life, or after life if we   were huddling around the dying embers of a white  dwarf once our Sun truly runs out of fuel.   We are mostly going to skim the topics of  Global Warming or Cooling from short term   or human-sources in terms of carbon dioxide  from factories or some volcano spewing ash out   to block sunlight. There’s tons of things that  can alter the atmosphere’s ability to absorb,  

reflect, or store sunlight and heat  energy, natural and artificial,   so even ignoring our current CO2 dilemma, we are  going to need to have plans and strategies for   managing planetary temperature in the long term. Even if we could convert to carbon neutral   tomorrow, it won’t eliminates scenarios  like volcanos, a comet or asteroid strike,   natural solar cycles, or even warming from  a nice clean and renewable power source like   fusion resulting in so much energy abundance  and economic growth that we had to make cooling   mechanisms just to handle all the waste heat from  the electricity being used by a trillion folks   living in environmentally sound Arcologies. Some folks might argue that the natural ones   like solar cycles or volcanoes need  not concern us since they are natural,   but personally I don’t care if they are artificial  or natural. Natural doesn’t impress me, natural is   folks sitting in trees sticking berries up their  noses and dying of random infections and plagues,   and natural is getting your civilization  wiped out by a tsunami or hurricane.  

So at some point we want to learn to manage  the sunlight hitting our planet to curb   warming or cooling and to start controlling  our weather to mitigate hurricanes and such.   The easiest way to do that is with solar shades  and mirrors, presumably sourced from the Moon or   Near Earth Asteroids and placed either in Orbit of  Earth or at our L-1 Lagrange Point with the Sun,   a spot about 1.5 million kilometers from Earth  toward the Sun, about 1% of the distance.   We’ve talked about this method many times, see  our Power Satellites episode for how to do this   and hopefully make a profit in the process, but in  summary, the planet’s temperature mostly depends   on how much sunlight hits it, either reflecting or  absorbing, and how long that heat gets retained.   Move the planet further or closer to the Sun –  something we’ll discuss later today – and it will   cool or warm respectively. But we can mimic that  by having thin shiny plates either bounce some  

additional sunlight down to Earth or to bounce  some away. We also potentially have the option of   using very thin and large reflective balloons that  floated up high enough to keep most sunlight out,   if we find that orbital mirrors are more difficult  to build and maintain than currently expected,   and such balloons might have some other advantages  to be used in tandem with orbital mirrors.   They are both conceptually simple, technologically  simple too, but a pain because tons of giant   mirrors can clutter your atmosphere and orbital  space, requiring extra effort to navigate and   keep it clear, and you also need to manufacture  them and fly them up and repair or replace them,   in the case of orbital mirrors. Hence we tend to like the idea of   doing it from the Moon as there’s tons of  aluminum on the Moon, which can be easily   cooked and made into shiny aluminum foil and  dragged into orbit. These mirrors will be our  

go-to for a lot of End of Earth prevention or  delaying options so their basic function and   creation bears repeating but see that episode  on Power Satellites for a more detailed dive.   Ironically they are non-optimal for dealing with  one type of climate change I didn’t mention,   which is a Nuclear Winter. Any nuclear war is  very likely to trash the orbital infrastructure   of a planet, and a few million shredded  solar mirrors each originally a kilometer   wide is certainly not going to help the space  debris issue. It’s not a big long term threat,   a solar shade or mirror falling out of orbit on  a planet wouldn’t even be a threat to those below   if it somehow didn’t get shredded and burnt up  in the descent, and they are easily replaced, but   to have them help correct a hypothetical nuclear  winter you’d either need them at your L-1 Lagrange   point or need to replace the orbital ones which  might be rather hard after a massive nuclear war,   those are assumed to be rough on industries and  economies. A nuclear winter is a catastrophe   theorized to cause a planet to cool after an  atomic war causes massive city and forest fires,   injecting vast quantities of soot into the  stratosphere, blocking much of the sunlight.   The modeling that came up with the concept has  been heavily criticized as flawed and simplistic,   so there’s doubt if a nuclear war would  cause one and if so to what degree,   but I could easily imagine that if one did, our  colonies on the Moon or Near Earth Asteroids might   see a big power shift as they have the resources  to be rebuilding that orbital infrastructure,   clearing the debris of the Kessler Syndrome, and  putting in new orbital mirrors or ones at L1.  

Additionally, another way we could get a  Nuclear Winter in the future is all that orbital   infrastructure getting blown to smithereens  and causing a thick cloud of debris around the   planet blocking light. Now we don’t have that  many satellites up in modern times, but when   we contemplate thousands of kilometer-wide solar  collectors, or space stations or space habitats,   that could cause an amount of debris large enough  to significantly dim incoming sunlight levels.   That would be temporary but potentially very bad  while it was slowly dissipating and clearing,   and ironically the fastest way to clear it would  be to detonate more nukes in higher orbits.   So there’s a number of things which can cause  a planet to cool and solar mirrors are probably   your go to for fixing most of them, and solar  shades for the reverse. Unnatural scenarios can   include nuclear war or global warming but can also  include Kessler Syndrome – which is when a bunch   of high-speed orbital debris hits other orbiting  objects, shredding them and causing more debris,   which cascades to ruin everything up there.  But that’s up there, not down below on Earth,  

so doesn’t concern us for this episode, as  even the cooling effect of such a cloud of   debris will be short term, at most decades, and  civilization disrupting, not humanity ending.   Of course that could cause a Snowball Earth  Scenario, which is when the whole planet freezes   over. The initial mechanism can vary but the idea  is that Earth’s temperature isn’t just about how   much light reaches the surface, but what happens  when it gets there. If it hits a mirror that light   leaves without doing much to warm things,  while if it hits a black object it absorbs   and warms things. Ice is quite reflective  to light compared to water or most dirt,  

so the fear is that if a bit more of the planet  got covered in ice, more light would reflect away   without warming us as much, causing a little lower  temperature, causing more ice to form and linger   further from the poles, causing more cooling, and  so on, cascading till the whole planet froze.   We suspect this may have happened to  Earth before, possibly repeatedly.   Now it is also likely to be temporary as a  frozen surface wouldn’t really affect volcanoes   but it would kill off most plant life. With  volcanoes spewing carbon dioxide every year,  

and very little photosynthetic life to remove  that carbon dioxide from the atmosphere,   the greenhouse effect would grow stronger and  stronger until it reached a tipping point,   whereupon the ice would start to thaw and  trigger the run away effect in reverse.   So too you’re adding layers of ash and debris to  the surface that are more absorptive to sunlight   rather than reflective white ice, there’s no  rain washing ash and soot away when it's frozen.   One alternative though, and which could happen  at any time, is something which causes Earth to   either get further from the sun or the Sun to  get dimmer. Indeed the Sun is actually getting   brighter with time but we could have weird  scenarios like some planetoid hitting the Sun   that caused its upper layers to darken for a  period or a black hole meandering into the Sun,   or a planet or star passing to nearby  to cause Earth’s orbit to be disturbed,   or even ejecting us into deep space. Indeed this  sort of planetary ejection is quite common and   we suspect interstellar space is littered with  such ejected frozen rogue or nomad planets.  

This is one way the Earth could die from  Ice, and folks wonder how long life would   last if the Sun shut off or we got moved from  it. The answer is actually a very long time.   First, if something did magically stop all fusion  in our Sun’s core, unlike in some films or shows   suggesting this would be rapid, years or  even minutes, we wouldn’t notice a thing   for many thousands of years. But a total shut  off of the Sun or us ejected into deep space   would still result in a long period of cooling. To begin with, the Earth has around 4x10^30 Joules   of Heat Energy in it, which is how much energy  the Sun releases in about 3 hours. However,   only about a two-billionth of the Sun’s light ever  reaches Earth, so that is akin to around 600,000   years worth of solar energy on Earth. We wouldn’t  stay warm that long on the surface obviously,  

but if you’ve ever wondered why the Earth’s core  is so hot, it’s a mixture of all the heat energy   of its formation and all the nuclear decay of bits  of uranium down there. That leaks out very slowly,   at a rate of about 50 Terawatts for the whole  planet, or a tenth of a watt per square meter,   and this process of cooling slows over  time, you lose heat more rapidly when hot,   and more slowly as you cool. This is important as the Earth   currently radiates around 5000 times more energy  from its surface than is coming up from below,   as geothermal heat, varying a bit by time of day  and year and location. It penetrates very little.   It would freeze pretty quickly, we anticipate  the oceans freezing over in a mere two months,   giving you that snowball Earth, but then as that  layer of ice insulates you, the rate of cooling   will slow even more. We’d expect liquid under  those oceans for at least another thousand years,   possibly much longer, and much would depend  on if the Moon was still tidally heating us,   which it would if the Sun went out but might  not if we got ejected from the solar system,   perturbations of that type can break satellites  off their primary, so the Moon might spin away.  

We can keep going even after that, in  underground caverns powered by nuclear reactors.   The surface would be dark, and yet even as  temperatures dropped to the point that you   might even get to see oxygen and nitrogen  raining down as liquids, a kilometer or two   down would still probably be livable. In such a  scenario you could keep retreating ever deeper,   to the extent of your ability to reinforce  and shore up tunnels – see our Subterranean   Civilizations episode for discussion of that. It also won’t cool completely, it would stop at   the point that the surface was radiating heat  at the same rate geothermal heat was working up   from the deep, again around a tenth of a watt per  square meter, or about 5000 times less than now,   and blackbody emission of light from hot objects  – or cold ones – goes up with the fourth power of   temperature. Unfortunately that would be around  8 Kelvin, considerably colder than even Pluto.   But we have discussed plenty of ways to inhabit  such frozen worlds before, and accomplishing   them on Earth would be easier given that all  our industry is already here. Realistically   though you would have to work very hard to get  as many nuclear power plants going as possible,   and locating all your good uranium and thorium  deposits, then hole up in caverns you further   insulated like thermos bottles to provide warmth  and artificial sunlight for flora and fauna.  

With sufficient technology and hard work, a  civilization could thrive on such a world,   so a Snowball Earth is probably not the End of  Earth or Humanity even if it happened tomorrow.   As I mentioned though the planet  would see the seas freeze over fast,   and indeed lose its atmosphere as the oxygen and  nitrogen in it cooled below their boiling point   and rained down on the frozen world below  as the Sun disappeared or darkened.   Now let’s contemplate the possibility of the  planet losing its seas and air as time goes   on and the Sun brightens, not so much death by  baking or asphyxiation given how slow it is,   but rather Death by Dehydration. The Sun grows brighter every year,   though it is very slow and amounts to about  a 10% to 25% increase in a billion years.  

Still that means in about a billion years the  amount of light hitting Earth at any given moment   will rise from the current average of 1361 Watts  per square meter to about 1500 Watts per square   meter, for a 10% increase, or 1700 for that  higher 25% brightness increase estimate. That’s   more than a trivial rise in illumination,  and thus temperature, akin to moving Earth   about 5 to 10 million miles or 8 to 15 million  kilometers closer to the Sun. It also means a   rise in certain nastier types of radiation. How much Ultraviolet or UV light comes off a   star for instance is a factor of both its total  brightness and the temperature. Raising a star’s   brightness by 10% doesn’t mean a 10% increase in  harmful UV light, because the spectrum or color   of any star peaks based on its temperature, so  we see even more UV light as the spectral peak   of the star shifts toward the blue and violet  and ultraviolet. This is a blue shift of light,  

a cooling star incidentally would red  shift, something we’ll discuss today too.   UV light doesn’t just give us suntans and  sunburns, it contributes strongly to ionizing   and stripping atmosphere off a planet. So too, a  brighter hotter sun is one producing more solar   wind, which also strips atmospheres off planets.  There’s several mechanisms for atmospheric escape   and most are exacerbated by hotter,  brighter, and more blue-shifted light.  

So as our sun grows hotter and brighter we  expect to see atmosphere depletion rise.   As atmospheres deplete, the rate of  depletion tends to snowball and accelerate.   Now as air leaves, pressure drops, and the boiling  point and evaporation point of water decreases   with that. As a brief tangent into chemistry,  liquids by and large cannot exist in a vacuum,   just solids and gases, in many ways a liquid  is just a gas being shoved together by external   air pressure, and the range of temperature in  which a material can exist as a liquid decreases   as pressure drops. For instance water at  normal earth air pressure exists between 0   and 100 celsius or 32 and 212 Fahrenheit,  but as pressure drops that range narrows,   the boiling point going down and by about a tenth  of normal pressure you will have about halved that   boiling temperature to around 50 Celsius or 120  Fahrenheit, by 1% of normal pressure its down to   boiling at 7 Celsius or 45 Fahrenheit. The reverse  is true too, higher pressure, higher boiling point   and wider range of temperatures for liquid phases  of materials. This is why we run steam engines  

and turbines under higher pressure, a higher  boiling point makes for more efficient engines.   Now as the air pressure drops all that ocean  beneath is going to start evaporating at lower   temperatures or faster than normal, and that  will not just raise humidity but should result   in some of those water gas particles ionizing  into hydrogen and oxygen and as a result,   some oxygen loss. The hydrogen will be  lost far faster than the oxygen to the   forces that deplete atmospheres, so essentially  you end up with ocean levels slowly dropping.  

Eventually your ocean disappears  and the atmosphere soon follows.   The worst case scenario models I’ve seen put  this at half a billion years ahead in our future,   assuming that higher end increase in  solar luminosity and worst scenarios   for atmosphere and ocean loss, and others put  it at nearly the red giant phase of our Sun,   our next topic, but 1-2 billion years tends to be  more in middle of estimates. We often see science   fiction descriptions of stars going red giant and  eating their worlds below, wiping out the last   life and seas, but in truth both would have long  since gone in even the most generous scenarios.   Now this is one of our easiest disaster and  end world scenarios to manage and prevent,   or at least delay. It has the three-pronged  advantage of being far in the future, very  

slow but obvious in its occurrence, and requiring  no advanced technology or mega-efforts to fix.   When it comes to problems, low-tech and low effort  solutions are nice, and problems you can’t ignore   or debate, but take a long time to slowly occur,  like coastal erosion, tends to be the safest bets   for handling, people can’t stick their heads in  the sand, but also have plenty of time to act.   The easiest method is those Solar  Shades we already discussed,   you just slowly increase how many of them you  have in orbit or at the L-1 Lagrange point.   Incidentally I mentioned coastal erosion as  an analogy a moment ago but we will give it   an honorable mention as a doomsday option.  Tidal and tectonic activity are harder to   model in terms of new land area being created  and old land being eroded away but most of this   planet is covered in water and the average  depth of that water is a few kilometers,   whereas much less of the planet is land and  very little of it is over a kilometer up,   so you could easily dump that land into  the oceans more evenly, submerging it all,   without making your seas shallow. Weather  and tides slowly remove land back into the   sea and we rely on tectonic plate collisions to  make new volcanoes and mountain chains arise,   to be weathered down into land masses. We  shouldn’t assume that is eternal, especially  

on other planets which might not have giant  moons or giant liquid metal cores and mantles.   So I could see the opposite of our sun-brightening  death-by-dehydration model, death by flood,   or by slow erosion anyway. Needless to say this  is easily corrected by a civilization with decent   industry given how slow it is. Nor is it a threat  to life existing on a planet. Or maybe it is. It   is possible a planet that became nothing but ocean  on its surface with no land for kilometers down   might lose all its nutrients and marine snow  with no sunlight anywhere near nutrients, and   given that the scenario assumes lower tectonic and  geothermal activity causing volcanoes and new land   to stop appearing, even the meager life possible  by deep sea thermal vents might shrink and halt.   Ditto without a big moon a planet might lose the  tidal effects that help with these processes,   and our Moon is getting further away every day,  and our own days longer. So death by the land   drowning into the seas is a possibility, and more  so on other planets perhaps, though given that   the ocean would be slowly dissipating too, the  Dehydration option is more likely by far I’d say.  

Now the sun will keep smoothly growing a little  brighter every year, but eventually that gradual   brightening will give way to a faster and larger  inflation into a sub-giant then a red giant,   but even when those relative surges happen it will  be pretty slow, and billions of years from now.   That red giant may well swallow Earth, but even if  it only got out to Venus, it would be implausible   that we could simply add enough solar shades to  Earth to keep it livable. We might be able to   extend the Sun’s own lifetime, by starlifting  material to reduce its mass, and prevent or at   least delay the red giant phase followed by the  white dwarf phase, which we’ll get to in a moment,   but an alternative is to just move the Earth. Now we’ve discussed building spaceships the size   of entire planets before, or bigger, and moving  at interstellar speeds – see our Planet Ships and   Fleet of Stars episodes for discussion of those  titanic craft – so moving a planet at less than   human walking speed away from the Sun to keep  us cool as it brightens is not much of stretch   of imagination compared to those. Indeed those  same solar mirrors and shades we discussed before  

can be used in greater number, combined with  gravity tractors or reflective patches on Earth or   on space towers, to slowly shove the planet away  using the Sun’s own light to power the process.   Indeed you might pack up the entire planet  and move it to a new solar system whose sun   is younger or had longer to live. And you might  maintain our ecosystem by a long network of relays   transmitting solar power from our own ever more  distant star, or stars enroute to our new star,   or you might use fusion. We mentioned the option  for the planet dying by Snowball earth if we   got ejected from the Sun, but that assumes a  natural act and not a technological effort.   Given the energy efforts involved, we’re not  talking about a few thermos bottle civilizations   buried kilometers below our frozen surface running  on fission power plants. We might be considering a   civilization running on nuclear fusion, in which  case the hydrogen in our own ocean is more than   sufficient to run civilizations for eons. Indeed you could artificially light our  

planet as bright as the Sun and as long as the Sun  normally would by hydrogen fusion of those oceans,   much shorter if you could only do deuterium based  fusion, which makes up only about 1 out of every   5000 hydrogen atoms in water, but still long  enough for a planet to coast to another solar   system in comfort and style. You can do vastly  better with a black hole as we’ll discuss in a   bit, but if you need to flee your own dying  sun, with decent technology and forewarning,   you can make the trip. You could later  return to our Sun after its red giant phase,   or have just moved into the Oort Cloud for it, and  bring Earth back to where it was, and ever closer,   as the Sun became a white dwarf and began cooling.  And through use of mirrors you could keep Earth   habitable around that cooling remnant for a very  long time. But white dwarfs themselves are out of  

fuel and are simply very hot and massive and cool  very slowly even compared to planets, but they are   out of fuel and are cooling, so living around  one eventually results in a Death by freezing.   Of course you might be able to refuel your  sun or extend its own life, and we discussed   the process for that in our episode Starlifting,  where by means magnetic and thermal you blow gas   off your Sun, pull out the elements heavier than  hydrogen – which include metals and key atoms for   organic life, and thousands of times more  than Earth has. You then drop the hydrogen   back in if you like, or keep it for other  uses. Either method extends the Sun's life,   which stirs and mixes its contents like a boiling  pot, but slowly concentrates helium in the core,   poisoning regular star burning of hydrogen  long before it runs out of hydrogen.   Indeed we estimate our Sun would only burn  about 10% of its hydrogen fuel before dying.   By removing the helium, and heavier elements, we  prevent this early natural death. What’s more,  

as a star mass decreases, whether by removing  just those heavier elements or also the hydrogen,   it burns slower and dimmer. As we’ve noted,  the Earth only gets about a two-billionth   of the Sun’s emitted light, so we could  dim our Sun a lot by lowering its mass,   extending its lifespan, and either move Earth  closer or just add a lot of solar mirrors.   It is also possible to take gas and fuel  from other stars to bring it to our sun,   removing spent fuel and adding fresh hydrogen.  Indeed most of the hydrogen in our galaxy is   floating around in clouds, not other stars, but  it's nicely concentrated in those stars which also   provide the power to disassemble them and hurl  giant pods of hydrogen back to our solar system.   In this way you could extend our Sun’s  lifetime for untold trillions of years.   On the topic of disassembly though, we probably  need to acknowledge that billions of years is a   long time to assume a status quo on Earth,  and civilizations disassembling other stars,   or other planets to help build giant stellar  engines like those used for Starlifitng, might   not consider Earth exempt from that. Or they might  place special value on Earth but find it easier  

to disassemble it, or its biosphere, for full  transport to another solar system, like moving a   house Brick by Brick. Earth may end simply because  it's seen as more valuable for its raw materials,   to humanity or to an alien invader or some  post human replacement for us like artificial   intelligence. That could happen a billion years  from now or even in just a few millennia.   Of course the end of the world might be an  accident too and even potentially in this century,   and from something artificial but not  intelligent. We often imagine inventing   self-replicating machines and them running  amok, disassembling everything to make more of   themselves, and we call this a Grey Goo scenario. Grey Goo is one way a world might be disassembled,   either an accident running away on us or an  intentional effort to disassemble the world   for raw materials, but ironically grey goo in  its natural and runaway state might not be an   Earth-ender, just an Earth changer. We often  compare grey goo to early life, green goo,   as basic microbes are essentially self-replicating  machines. We might expect grey goo to evolve  

more complexity with time too, as green  goo apparently did, even to the point   of sentient and sapient lifeforms. However  the whole planet was not really green gooed,   only a very thin film on its surface was. And this  is potentially true for gray goo too. Consider,   we contemplate runaway self-replicating machines  turning the whole planet into more of themselves   but how could the lower layers do this? There’s  no place for them to absorb sunlight to power   themselves for instance when buried  under kilometers of their cousins.  

Presumably regardless of their power  source they should seek to be on top   getting sunlight for free energy and open  air or space for easier cooling. So too,   what sort of machine could really operate when  buried under kilometers of other tiny machines?   Surely they would be crushed and grow hot, just  like our own magma. So grey goo would not get   the whole planet, and indeed we likely would see  slow mutation into many species as some specialize   in focusing on getting to the surface while others  learn to cannibalize and eat their damaged cousins   slowly sinking through the sea of each other to  the magma layer below. One can easily imagine much  

speciation and variations of our own ecosystems  including the marine snow of organic debris in   our own oceans feeding the sunless ecosystem  deep down below. Here though its cannibals in   a sea of metal and silicon floating on a raft  of wrecked and compressed predecessors itself   floating on the magma, occasionally perturbed or  volcanoed to higher levels to refresh things.   Nor would they be cannibals for long as they  diverged much as early life did here. So in truth,   grey goo would only replace the green goo layer on  Earth, and probably just spawn a new era of life.  

If you want to eat even the planet’s core,  truly obliterate Earth, then your better bet   might be a black hole, and these are amazing power  source civilizations will likely seek to master,   a hundred times better than even nuclear fusion,  but often perceived as dangerous. However, as we   saw in our episode Weaponizing Black Holes, while  they are dangerous it really takes a precision and   deliberate effort to destroy a planet with  one, or better yet a pair of them, and one   accidentally escaped from groundside power plants  would probably need millions of years to eat   Earth if they ever could. Plus you can actually  capture and remove one with sufficient effort.   They really would not sink to the core  of a planet till it was far too late to   care, instead bouncing around inside a  world. See that episode for the details.  

But Black Holes offer us one option for long term  survival that our Sun’s natural fate does not.   First, as probably the best power source in  known physics, you can slowly dump matter   into them to produce power. Every kilogram of  mass has the same fundamental energy in it,   E=mc², and you can get somewhere between a  fifth to half of that energy out of a black hole   by dropping it into one, and the rest as very  slowly released Hawking radiation long after.   Any kind of matter works equally well,  including your garbage or hazardous materials,   or abundant hydrogen and helium,  or potentially even dark matter.  

We’ve mentioned losing Earth’s ocean to  evaporation, and they mass about a billion,   billion tons. That represents a mass-energy  of about 10^38 joules or 100 million, billion,   billion, billion joules, which is about 10,000  years of light production for the whole Sun,   or 20 trillion years worth of sunlight for  the entirety of Earth, which again only gets   about a two-billionth of the Sun’s released  total sunlight. That’s a very long time,   and you could be feeding in mountains instead of  water. Earth itself masses more than a thousand   times what our oceans do, meaning you could  drip feed the whole planet into black holes   to run it for quadrillions of years, long  after every star in the Universe had died.  

You might run power off one for Earth from stores  of other matter too. Jupiter is around 300 times   more massive than Earth and the Sun a thousand  times more massive than Jupiter. And the galaxy a   trillion times more massive than that, if you want  to raid other solar systems for fuel. Including  

dead sources, there’s no reason you can’t  feed even dying white dwarfs into black holes,   though this is rather tricky without setting off  a supernova and far harder with a neutron star,   which are even denser and require even  more energy to starlift material off of,   though carefully skimming the surface off one  with a black hole is one possible approach,   albeit one requiring amazing precision  to avoid catastrophic explosions.   So when it comes to the End of the  Earth, it might be a long way off indeed,   not thousands of years or even a few  billion, but a billion-billion years or more.   Yet will it be by fire or ice? One might  think in a universe slowly cooling off   and run on scraps of power from black holes that  it would be ice, but our current theory say black   holes do evaporate over time, and give off energy  faster and faster as they get smaller and smaller,   releasing ever more Hawking radiation ever more  quickly, till growing to be miniature suns. In the   end, if true, and if you can survive long enough  to tap dying black holes for this sort of power,   your ending isn’t in darkness and ice, but a  swelling period of ever brighter millennia and   centuries ending in an explosive surge. You would  be consumed by fire, if you chose to remain close,  

but given that there would be nothing left to live  on, except maybe iron stars countless eons beyond,   there would seem little reason to escape the fire  and freeze in the cold endless night beyond.   So civilizations would get to pick, fire or ice,  as they so desired, but it’s a choice they need   not make till a future so far ahead in time it  makes a billion years seem like an eyeblink.   Today we are celebrating our 300th Thursday  episode and we will get to discussing that   and our upcoming schedule in just a moment,  but first: A common problem that comes up on   this show and other sciences shows  is always how much math to put in,   because it really is often very fundamental  to understanding and mastering concepts,   and yet lots of folks are not comfortable  with math. I try to minimize how much we   put on the screen because simply explaining math  doesn't help much. You have to practice with it   in a hands-on fashion, and that’s something our  friends at Brilliant focus on: Interactivity.   Over the last year, Brilliant has built a  whole new platform for their courses that   takes interactivity to the next level.  Pre-Algebra, Mathematical Fundamentals,  

and Algorithm Fundamentals are the first  courses launched on this platform.   Brilliant is a website and app built off this  principle of Interactivity: you learn best while   doing and solving in real-time, not by long  lectures or memorising formulas and facts.   With Brilliant you can jump right into solving  problems and be coached bit-by-bit until,   before you even realize it, you've learned a  new subject in STEM. And if you do get stuck   or make a mistake you can read the explanations  to find out more and learn at your own pace.  

Brilliant has something for everybody — whether  you want to start at the basics of math,   science, and computer science, or try any  of their many excellent daily challenges,   and if you'd like to join me and a community  of 8 million learners and educators today,   click the link in the episode description down  below or visit:   So as mentioned earlier, this is episode  300 and as I’ve explained in the past,   that is a somewhat debatable number because we  didn’t start doing weekly episodes until about our   20th, and the formal numbering system has actually  become the production week these days, so that 300   does not include any of the bonus episodes we’ve  done, which when combined with livestreams and   two-part collaborations, puts us at nearly 400  episodes, not 300. Amusingly it’s 357 weeks since   the very first episode and this episode comes out  exactly 2500 days after the original episode came   out, which somehow seems the better benchmark.  Nonetheless since we started doing them weekly,   we have never missed a single Thursday release,  not one week, not even on my honeymoon.   I occasionally think about resetting the  numbering in some fashion but the problem is   my own calendar of personal tasks and even my  journal uses this numbering these days, which is   pretty indicative of how much this show has grown  over the years from a casual experiment to a major   hobby to a full-time-plus profession, and it’s a  great chance to once again thank all the folks who   have helped the show grow. Every volunteer whose  helped with script editing or making animations or  

moderating our social media forums. Every patreon  and nebula subscriber, paypal or snailmail donor,   superchatter in the livestream, and our sponsors.  And every person whose watched episodes and   shared them with others, hit that like button,  left a comment, and subscribed to the show.   Without you, this show wouldn’t be possible  and I cannot thank you enough. I’ve also gotten   married since our last benchmark of 200 episodes,  which came out about the time Sarah and I started   dating, and I also can’t thank her enough for  her help on the show, including co-hosting our   monthly livestream, and putting up with the long  hours I spend writing and producing episodes.  

So thanks again to everyone and here’s  to 300 more episodes, 2500 more days   of production, and one more great week. Speaking of Livestreams, we will be having one   this weekend on Sunday July 25th at 4 pm Eastern  Time. Then we will close the month out with the   third episode of our Galactic Domination series,  the Galactic Laboratory. That will takes us into   August, which we’ll begin with a look at whether  or not it's time for us to Embrace Nuclear Power,   and the week after we’ll look at what the  next space station after the ISS will be,   before we have our mid-month Scifi Sunday episode:  Alien Artifacts & Xenoarcheology, on August 15th.   If you want alerts when those and other episodes  come out, make sure to subscribe to the channel,   and if you’d like to help support future episodes,  you can donate to us on Patreon, or our website,, which are linked  in the episode description below,  

along with all of our various social media forums  where you can get updates and chat with others   about the concepts in the episodes and many other  futuristic ideas. You can also follow us iTunes,   Soundcloud, or Spotify to get our  audio-only versions of the show.   Until next time, thanks for  watching, and have a great week!

2021-07-26 09:23

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