What-If 0049: "Sunless Earth"

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AlexTheSeal
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Re: What-If 0049: "Sunless Earth"

Postby AlexTheSeal » Wed Jun 12, 2013 9:46 pm UTC

rmsgrey wrote: I have seen plausible arguments that quines can't exist based on some idea that a subset of an object can't contain enough information to describe the entire object in full detail...


That sounds fallacious to me. First, a quine isn't a subset of anything. It implicitly contains the entire programming language in which it's written, and a set of shared assumptions that go along with its presence as a computational object in the world. A good analogy is to human language, where a single word is meaningless without the baggage of all the shared cultural assumptions that make language and communication possible. You make use of subsets of language "that contain enough information to describe the entire object in full detail" every time you use a single word where you could use a phrase.

Code: Select all

10 REM WORLD'S SMALLEST ADVENTURE GAME
20 PRINT "YOU ARE IN A CAVE (N, S, E, W)? ";
30 INPUT A$
40 GOTO 10

Lulled to sleep by the one-hertz chuckle of Linux logfile writes since 1997.

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Re: What-If 0049: "Sunless Earth"

Postby rmsgrey » Wed Jun 12, 2013 10:36 pm UTC

AlexTheSeal wrote:
rmsgrey wrote: I have seen plausible arguments that quines can't exist based on some idea that a subset of an object can't contain enough information to describe the entire object in full detail...


That sounds fallacious to me. First, a quine isn't a subset of anything. It implicitly contains the entire programming language in which it's written, and a set of shared assumptions that go along with its presence as a computational object in the world. A good analogy is to human language, where a single word is meaningless without the baggage of all the shared cultural assumptions that make language and communication possible. You make use of subsets of language "that contain enough information to describe the entire object in full detail" every time you use a single word where you could use a phrase.


Yeah, the fact they conclude that quines can't exist means that there must be some kind of mistake in the argument somewhere - I mention it because it's essentially the same as one of the common arguments used to try to prove that we can't be in a computer simulation...

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Re: What-If 0049: "Sunless Earth"

Postby teelo » Wed Jun 12, 2013 11:05 pm UTC

Randall still hasn't answered the question: What if the sun went out... with a dude?

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Re: What-If 0049: "Sunless Earth"

Postby Reecer6 » Thu Jun 13, 2013 3:56 am UTC

teelo wrote:Randall still hasn't answered the question: What if the sun went out... with a dude?

Gross!
Is how I would describe the resulting burnt husk of their date when anywhere near the Sun. They'd definitely be star-crossed lovers by physics themselves. *wink wink*

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Re: What-If 0049: "Sunless Earth"

Postby Mike Rore » Thu Jun 13, 2013 5:30 am UTC

I think that if the sun went "off", there would be a sharply decrease in skin cancer globally, also, there would be no need to use sun blockers or anti-aging creams that claim to restore the damage caused by the sun.

Also, it would make the planet inhabitable for velociraptors.

But most importantly, almost the entire surface of the planet would be beautifully preserved for the next species of aliens to come up and thaw everything in some sort of archeological paradise...

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Re: What-If 0049: "Sunless Earth"

Postby orthogon » Thu Jun 13, 2013 8:00 am UTC

Bad Hair Man wrote:
WhiteDragon wrote:There is a star that has this happen every few hundred years, in the Vernor Vinge novel A Deepness in the Sky. There's actually a civilization that lives on a planet around said star, with everyone going into deep hibernation during the off times.

Ooh, creepy! It's like it's some sort of Winking Demon Star!

(Not to be confused with...

Quicksilver wrote:I still think the sun is evil.

...the evil Daystar.)

The yellow face! It burns!
xtifr wrote:... and orthogon merely sounds undecided.

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Re: What-If 0049: "Sunless Earth"

Postby NiteClerk » Thu Jun 13, 2013 2:19 pm UTC

I would save a lot of time not mowing my yard.

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Re: What-If 0049: "Sunless Earth"

Postby Asymtote » Thu Jun 13, 2013 8:11 pm UTC

Another part of this, if the sun were suddenly to no longer exist completely (say, by 'magic'), and since no information can travel faster than the speed of light (gross oversimplification, but functional here), not only would we see the sun shining for the ~8 minutes it takes for the light to reach Earth, but Earth would stay in orbit around the gone-for-8-minutes sun before flying off on a tangential path. Now, since each planet is moving at a slower and slower orbital velocity as you move farther away from the sun, is it possible for some future orbital configuration of the planets to all end up crashing into each other if the sun were to no longer exist?

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Re: What-If 0049: "Sunless Earth"

Postby Klear » Fri Jun 14, 2013 7:46 am UTC

Asymtote wrote:Another part of this, if the sun were suddenly to no longer exist completely (say, by 'magic'), and since no information can travel faster than the speed of light (gross oversimplification, but functional here), not only would we see the sun shining for the ~8 minutes it takes for the light to reach Earth, but Earth would stay in orbit around the gone-for-8-minutes sun before flying off on a tangential path. Now, since each planet is moving at a slower and slower orbital velocity as you move farther away from the sun, is it possible for some future orbital configuration of the planets to all end up crashing into each other if the sun were to no longer exist?


I'd say the odds against that are literally astronomical.

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Re: What-If 0049: "Sunless Earth"

Postby cjmcjmcjmcjm » Fri Jun 14, 2013 6:31 pm UTC

armandoalvarez wrote:
Dyolf_Knip wrote:
armandoalvarez wrote:Then you magically restore the sun.

Brutal. All the atmosphere would have condensed into snow and ice, and then suddenly gets blasted with normal daylight? It'd cause storms powerful and destructive beyond imagining.

I mean, that depends on how long this "finite amount of time" cjmcjmcjmcjm is talking about lasts. If we're talking picoseconds, I think we're good. The earth wouldn't have had long enough to cool down and cause the atmosphere to condense into ice. If we're talking 1 billion years, not so much.

I was thinking of some time reasonable for humans. Mostly different scenarios lasting between an minute and a year.
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Re: What-If 0049: "Sunless Earth"

Postby Flumble » Sun Jun 16, 2013 7:14 am UTC

Asymtote wrote:Another part of this, if the sun were suddenly to no longer exist completely (say, by 'magic'), and since no information can travel faster than the speed of light (gross oversimplification, but functional here), not only would we see the sun shining for the ~8 minutes it takes for the light to reach Earth, but Earth would stay in orbit around the gone-for-8-minutes sun before flying off on a tangential path. Now, since each planet is moving at a slower and slower orbital velocity as you move farther away from the sun, is it possible for some future orbital configuration of the planets to all end up crashing into each other if the sun were to no longer exist?

The odds that any two planets crash into eachother after the Sun is removed, are very rare already. Imagine you are a planet and you're drifting away from the now-gone Sun. The other planets all start out at a certain location and are moving with a certain motion vector from your viewpoint. Since the planets had a different orbital speed and orbital inclination, you can just as well take some random lines x=a+dt,y=b+et,z=c+ft) in R³ and see how many will cross the origin. (or use Zk³ and keep t small if you want something measurable)

(apologies for any vagueness, but I've been awake for far too long)

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Re: What-If 0049: "Sunless Earth"

Postby NotThatGuy » Sun Jun 16, 2013 12:54 pm UTC

"Source: I'm going to go out on a limb and say 'The US Naval Observatory' on the assumption that no one there will read this."

Randall, are you just trolling us? Your artwork decorates many a cubicle wall on Mass Ave, and I'm sure it's the same out in Flagstaff.
Can't tell you how many comments you've had for the 'radiation' and 'economy' charts, but especially for 'oceans' bathymetry' as you might imagine.

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Re: What-If 0049: "Sunless Earth"

Postby DR6 » Sun Jun 16, 2013 8:33 pm UTC

All the people talking about how we could try to survive are forgetting something: no matter how much geothermal and nuclear bullshit you use, entropy still decreases on closed systems, and the only thing that is feeding us entropy now is the sun. We might be able to scratch a bit from the entropy left, but it would be gone really soon...

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Re: What-If 0049: "Sunless Earth"

Postby brenok » Sun Jun 16, 2013 9:44 pm UTC

I believe you mean "energy", not entropy.

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Re: What-If 0049: "Sunless Earth"

Postby Copper Bezel » Sun Jun 16, 2013 9:57 pm UTC

I think he meant entropy, but I think he's misusing it. An even distribution of thermal energy can't be used to do work. Of course, that's not what we have here.

The Earth would be a closed system in the sense that the sun + Earth is a closed system now. After 4.5 Ga, most of the parts of Earth that aren't crust and aren't liquid are solid because of pressure, not temperature. There's still a hell of quite a temperature gradient going on there, thus, a hell of a lot of work still doable.

And that's not getting into the nuclear thing, although the potential geothermal energy is many, many orders of magnitude greater in total.
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Re: What-If 0049: "Sunless Earth"

Postby ijuin » Mon Jun 17, 2013 2:50 am UTC

The amount of energy available from the fissile material recoverable from the earth by mankind short of refining the entire mantle and core is indeed a drop im the bucket compared to the sum total of the planet's internal heat. However, the half a quintillion tons of hydrogen in the planet's water supply can dwarf even that if used as fusion fuel. As long as our sunless humanity is using this energy to heat and light habitats hundreds of meters or more underground instead of wasting it on the surface where it will radiate away, then there should be enough energy to last for millions of years. Also, if the other planets are still around, we can mine Saturn for its three to five septillion tons of hydrogen fuel, which itself would be more than enough to fuel engines big enough to move the entire earth on a thousand year voyage to a new sun.

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Re: What-If 0049: "Sunless Earth"

Postby Diadem » Mon Jun 17, 2013 7:22 am UTC

ijuin wrote:The amount of energy available from the fissile material recoverable from the earth by mankind short of refining the entire mantle and core is indeed a drop im the bucket compared to the sum total of the planet's internal heat. However, the half a quintillion tons of hydrogen in the planet's water supply can dwarf even that if used as fusion fuel. As long as our sunless humanity is using this energy to heat and light habitats hundreds of meters or more underground instead of wasting it on the surface where it will radiate away, then there should be enough energy to last for millions of years. Also, if the other planets are still around, we can mine Saturn for its three to five septillion tons of hydrogen fuel, which itself would be more than enough to fuel engines big enough to move the entire earth on a thousand year voyage to a new sun.

Now I want to write a sci-fi story about this :)
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Re: What-If 0049: "Sunless Earth"

Postby gmalivuk » Mon Jun 17, 2013 8:00 pm UTC

Asymtote wrote:no information can travel faster than the speed of light (gross oversimplification, but functional here)
How is that a gross oversimplification? Current scientific understanding has that no information can travel faster than the speed of light in a vacuum. Full stop.

Diadem wrote:
ijuin wrote:The amount of energy available from the fissile material recoverable from the earth by mankind short of refining the entire mantle and core is indeed a drop im the bucket compared to the sum total of the planet's internal heat. However, the half a quintillion tons of hydrogen in the planet's water supply can dwarf even that if used as fusion fuel. As long as our sunless humanity is using this energy to heat and light habitats hundreds of meters or more underground instead of wasting it on the surface where it will radiate away, then there should be enough energy to last for millions of years. Also, if the other planets are still around, we can mine Saturn for its three to five septillion tons of hydrogen fuel, which itself would be more than enough to fuel engines big enough to move the entire earth on a thousand year voyage to a new sun.

Now I want to write a sci-fi story about this :)
Note that we'd want to keep acceleration down around a micron per second per second, since that is on the order of current tidal forces and water sloshing around could become a problem at higher accelerations (though I suppose if we let the oceans freeze solid it becomes less of an issue).

At that rate, it would take rather longer than a thousand years to get to the nearest star. 4.5ly is about 4e16 meters, so to turnaround (if we accelerate halfway and decelerate halfway, at 10^-6 m/s^2), time^2 is 4e22, which works out to 200 billion seconds, or about 6300 years.
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Re: What-If 0049: "Sunless Earth"

Postby Copper Bezel » Mon Jun 17, 2013 8:56 pm UTC

An awesome bit of calculation, but I'm more impressed that the original approximation was accidentally within an order of magnitude.
So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

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Re: What-If 0049: "Sunless Earth"

Postby Diadem » Mon Jun 17, 2013 10:39 pm UTC

Yeah that is pretty awesome. It really doesn't even take that long, considering how slow 1 micron per second per second is.

You wouldn't even have to stop the earth though, at your destination. You could send unmanned, or even manned, spacecrafts ahead of the earth to scout, and to set up mining facilities at the next system's gas giants for hydrogen. Basically you'd be setting a permanent course through interstellar space refuelling every few thousand years.
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Re: What-If 0049: "Sunless Earth"

Postby rmsgrey » Mon Jun 17, 2013 11:20 pm UTC

Diadem wrote:Yeah that is pretty awesome. It really doesn't even take that long, considering how slow 1 micron per second per second is.

You wouldn't even have to stop the earth though, at your destination. You could send unmanned, or even manned, spacecrafts ahead of the earth to scout, and to set up mining facilities at the next system's gas giants for hydrogen. Basically you'd be setting a permanent course through interstellar space refuelling every few thousand years.


Recommended reading: Tau Zero by Poul Anderson - a ramscoop ship suffers an engineering malfunction that prevents it from turning to decelerate, so the only option is to keep accelerating until they can figure out a solution...

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Re: What-If 0049: "Sunless Earth"

Postby gmalivuk » Mon Jun 17, 2013 11:40 pm UTC

Copper Bezel wrote:An awesome bit of calculation, but I'm more impressed that the original approximation was accidentally within an order of magnitude.

A thousand years is not within an order of magnitude of 13000 years, last I checked.

rmsgrey wrote:
Diadem wrote:Yeah that is pretty awesome. It really doesn't even take that long, considering how slow 1 micron per second per second is.

You wouldn't even have to stop the earth though, at your destination. You could send unmanned, or even manned, spacecrafts ahead of the earth to scout, and to set up mining facilities at the next system's gas giants for hydrogen. Basically you'd be setting a permanent course through interstellar space refuelling every few thousand years.


Recommended reading: Tau Zero by Poul Anderson - a ramscoop ship suffers an engineering malfunction that prevents it from turning to decelerate, so the only option is to keep accelerating until they can figure out a solution...
Larry Niven has a couple of relevant things as well. The Puppeteers' Fleet of Worlds are a group of 5 planets heading toward a Magellanic Cloud, and those feature in several of his novels. I also remember a short story about one person chasing another to infinity in ramscoops, as neither one is ever willing to stop accelerating lest the other win. (For the sake of having an interesting drive, Niven ignores the fact that a ramscoop actually has a fairly modest terminal velocity, relativistically speaking, since eventually the relative incoming velocity of interstellar hydrogen will match the exhaust velocity and the ship couldn't go any faster.)
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Re: What-If 0049: "Sunless Earth"

Postby Pfhorrest » Tue Jun 18, 2013 5:00 pm UTC

gmalivuk wrote:
Asymtote wrote:no information can travel faster than the speed of light (gross oversimplification, but functional here)
How is that a gross oversimplification? Current scientific understanding has that no information can travel faster than the speed of light in a vacuum. Full stop.

I wonder if he's thinking of something like quantum entanglement, where the particles are in some level of communication with each other (to "know" each other's state) faster than c, but which still can't be used to send a signal faster than light. Or maybe even something like how the group speed of a pulse can travel faster than light, but that still can't be used to send a signal faster than light. There are various FTL phenomena like these I could see complicating the original statement, but the overall gist is still that any such thing is useless for FTL communication. Calling that "gross oversimplification" seems a little uncalled-for though; I'd say it's more "the bottom line": sure there are some FTLish phenomena but when the rubber hits the road you can't send a signal faster than light, period.
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Re: What-If 0049: "Sunless Earth"

Postby gmalivuk » Tue Jun 18, 2013 11:51 pm UTC

"Nothing goes faster than light" is a simplification, since there are some "things" which could (the simplest example is just the dot of a laser pointer shining on a surface sufficiently far away).

But "No information travels faster than light" is not a simplification of reality, it just is. (Well, I guess it does gloss over the fact that we're talking specifically about the speed of light in vacuum rather than through a medium, and that "information" has a precise definition as used in the statement.)
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Re: What-If 0049: "Sunless Earth"

Postby elasto » Wed Jun 19, 2013 2:44 am UTC

rmsgrey wrote:The other obvious mistake people often make in arguing that the universe can't be a simulation is in assuming that all 1030 or so cubic light-years are being simulated down to the planck length at intervals of the planck time - if I were setting up a Matrix-style simulation, I'd mostly just model things down to the cubic millimeter or so in the vicinity of people, and not bother keeping the simulation updated for anything on the other side of the skybox - you only need to do enough simulation to supply the data that people perceive - who'll know or care if a dozen galaxies wink out on the far side of the universe?


Cool post-Singularity story - one of my favorite stories ever: http://localroger.com/prime-intellect/mopiidx.html
(Warning: contains extreme depictions of acts of sex and violence though)

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Re: What-If 0049: "Sunless Earth"

Postby Flater420 » Tue Aug 27, 2013 5:11 pm UTC

Safer combat pilots: Many people sneeze when exposed to bright sunlight. The reasons for this reflex are unknown, and it may pose a danger to fighter pilots during flight.[9] If the Sun went dark, it would mitigate this danger to our pilots.


I was told in school that the heat of the sun causes the mucus in your nose (which is spread like a film between your nose hairs) to contract, which slightly moves the hairs in your nose and triggers a sneeze. We tested it in class by blowing hot or cold air in someones face. The ones that got the hot air stream sneezed noticeably more.

Or has this since been disproven?

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Re: What-If 0049: "Sunless Earth"

Postby Nnelg » Tue Sep 10, 2013 6:57 am UTC

Asymtote wrote:Now, since each planet is moving at a slower and slower orbital velocity as you move farther away from the sun, is it possible for some future orbital configuration of the planets to all end up crashing into each other if the sun were to no longer exist?

Actually, the orbital velocity increases for orbits with greater semi-major axes. It's kind of misleading though, since the greater distance to travel means it takes longer to complete an orbit overall.

As for planets crashing into each other, I really have no idea -but I wouldn't be surprised if they didn't.
keithl wrote:As a rule of thumb, it is imprudent to pass over speed bumps faster than orbital velocity.

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Re: What-If 0049: "Sunless Earth"

Postby gmalivuk » Tue Sep 10, 2013 7:24 pm UTC

Nnelg wrote:Actually, the orbital velocity increases for orbits with greater semi-major axes.
No, it most certainly doesn't.
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Re: What-If 0049: "Sunless Earth"

Postby rmsgrey » Tue Sep 10, 2013 8:06 pm UTC

Nnelg wrote:
Asymtote wrote:Now, since each planet is moving at a slower and slower orbital velocity as you move farther away from the sun, is it possible for some future orbital configuration of the planets to all end up crashing into each other if the sun were to no longer exist?

Actually, the orbital velocity increases for orbits with greater semi-major axes. It's kind of misleading though, since the greater distance to travel means it takes longer to complete an orbit overall.

As for planets crashing into each other, I really have no idea -but I wouldn't be surprised if they didn't.



The orbital period goes up as the 1.5th power of the semi-major axis, while the length of the orbit goes up as the 1st power, so the mean orbital velocity goes down.

What you may have been thinking of is the fact that, among orbits with the same periapsis, orbits with longer semi-major axes have greater orbital speed at periapsis (but lesser average orbital speed).

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Re: What-If 0049: "Sunless Earth"

Postby Nnelg » Thu Sep 12, 2013 12:37 am UTC

rmsgrey wrote:What you may have been thinking of is the fact that, among orbits with the same periapsis, orbits with longer semi-major axes have greater orbital speed at periapsis (but lesser average orbital speed).

Yeah, that would be it then. (I blame Kerbal Space Program. :P)
keithl wrote:As a rule of thumb, it is imprudent to pass over speed bumps faster than orbital velocity.


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