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I thought of this question after seeing this related question which deals with Norse gods. This question deals with the supernatural actions of the Judeo-Christian God.

In Chapter 10 of the Book of Joshua of the Bible, the following events occurred:

12. On the day the Lord gave the Amorites over to Israel, Joshua said to the Lord in the presence of Israel:

“Sun, stand still over Gibeon,

and you, moon, over the Valley of Aijalon.”

13. So the sun stood still,

and the moon stopped,

till the nation avenged itself on its enemies,

as it is written in the Book of Jashar.

The sun stopped in the middle of the sky and delayed going down about a full day.

14. There has never been a day like it before or since, a day when the Lord listened to a human being. Surely the Lord was fighting for Israel!

The following events must occur on Earth:

  1. The Sun and the Moon must stop moving as viewed from the surface of the Earth for 24 hours, and continue on their motion afterwards.

  2. As viewed by the people on Earth, there should not be any significant abnormal events above and beyond the celestial bodies ceasing their motion. This includes earthquakes, gusts of wind, compasses breaking down, etc.

What is the minimum amount of energy required to replicate this event?

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March Ho
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  • Do the tides still need to go round as per normal? It's a very small amount of energy to think about, all things considered, but if they do then you'll need some extra energy for it. – Joe Bloggs Oct 21 '15 at 09:43
  • @JoeBloggs Yes, preferably nothing should change except the relative positions of the Sun and Moon. – March Ho Oct 21 '15 at 09:53
  • Are you expecting just the Sun and Moon position to stay stable, or a day/night-difference between Gibeon and the Valley of Aijalon? – Layna Oct 21 '15 at 09:55
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    Since you are talking about a fairly limited number of people to expecience this, i get the impression that making them believe it has happened rather than actually at least providing the illusion would be a lot more economical. Let them have a nice celebration after the event to explain the reasons for the hangover. – Burki Oct 21 '15 at 11:20
  • The sun is already stopped. – Oldcat Oct 21 '15 at 17:35
  • Do you mean actually stopping the Earth from orbiting? In that case we will plummet towards the sun. Or to simply make it appear as if the sun and moon stopped. – Jax Oct 21 '15 at 17:51
  • The apparent motion of the sun due to earths orbit is too slow to see by eye. The apparent motion is almost entirely due to the rotation about its axis. – Oldcat Oct 22 '15 at 16:58
  • @Burki Yeah, an illusion would definitely be much easier to arrange for a small population isolated to a particular location. You could do it all with mirrors and lenses, in fact. – user867 Oct 26 '15 at 07:27

5 Answers5

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Lowest energy way to do this? Like the Truman show.

Essentially: Stopping the motions of any celestial bodies is an epic task, especially if you don't want to mess up the tides, etc. Instead you just want to give things the appearance of having stayed where they were. This is easiest to do as an illusion rather than an actual celestial event.

Position four disks in strategic places. These discs need to be insanely powerful screens capable of projecting in all the wavelengths their respective objects, one for the moon, one for the sun, and two to take over for the starfield of the blocked objects. As you position these discs you can use the screens to 'take over' for the objects they represent, then lock the sun/moon disks in place and move the starfield disks to continue blocking the actual sun/moon. After 24 hours, when everything is back in the same place (or longer in the case of the moon), take the disks out of the way to restore the status quo.

This seems exorbitant: You've got to output the energy of the sun that falls on the earth for 24 hours, which is a lot of power. On the other hand you've got a huge solar panel that's taking all the energy that the earth would usually get, and you don't have to try stopping an entire planet's rotation or halting the moon, and dealing with all the effects that that entails. The exact amount of energy required depends upon the construction of your disks, but it will be some orders of magnitude below the energy required to stop the moon.

So the easiest way to make is seem like the Sun and Moon have stopped is to make it seem like the sun and moon have stopped.

Joe Bloggs
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    A portal of suitable size would have the same effect as well. You need something to absorb the sun's energy from the real direction and emit it from the fake direction so anything that redirects it will work just fine. – Tim B Oct 21 '15 at 10:44
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    I think Tim B is on the right track, you initially need to do something with the light sun and moon are outputting anyway to hide they are moving. And the output you need to get rid of just happens to be roughly same magnitude as the one you need to fake. Instead of a portal maybe satellite mirrors might do. You'd need multiple mirror "clouds" to bounce the light for 24 hours and they'd need to be huge. But the energy needed would be much smaller. – Ville Niemi Oct 21 '15 at 11:00
  • @VilleNiemi is correct. The actual energy needed is 0, the question is how do it without being inefficient. – NPSF3000 Oct 21 '15 at 11:16
  • I was assuming our powers were limited to just moving objects around rather than portal'ing radiation, but I suppose if we're positing that we can stop planets then being clever enough to bounce some light around isn't too much of an issue. ( I went with powerful screens and solar panels because then you don't have to worry about getting the images the right way round/aberrations/focal distances etc). – Joe Bloggs Oct 21 '15 at 11:47
  • Relevant Invader Zim episode. – Wrzlprmft Oct 26 '15 at 14:52
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Like many things in the Bible, this event is physically impossible. Regardless of how much energy you have you still have the problem of momentum. The stopping force would have to be applied to every atom of the Earth and Moon individually otherwise they would be torn apart by their own momentum.

Let's assume it takes a few seconds for the Earth to stop spinning at it's current surface speed of 1,674 km/h. Everything on the Earths surface will still be travelling at that speed. This will probably be noticed by the discerning human. In fact, it probably wouldn't, everyone would be instantly dead.

If you want to just say "God is able to stop every atom individually, including those of objects and animals on the Earths surface" then your question is pointless as any "abnormal events" could just be prevented with a click of God's fingers.

Just to be complete, the mass of Earth is 5.972 × 10^24 kg and it's angular speed is 1,674km/h, making it's rotational kinetic energy (m/v^2)/2 = (5.972E24/1674^2)/2 = 1,065 x 10^14 Joules.

The mass of the moon is 7.348 × 10^22 kg and it's speed is 3,683km/h, making it's kinetic energy (m/v^2)/2 = (7.348E22/3683^2)/2 = 27 x 10^14 Joules.

The current energy these objects have is also the energy needed to stop them. If someone with better physics knowledge than me could check my working, would be appreciated, I haven't done any physics for over 5 years! Values I retrieved from Wikipedia.

Varrick
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  • The rule suggested current kinetic energy = energy required to stop is not correct in general. For example, a matching energy input is not required to stop a bullet with an obstacle, or to stop a car moving by applying the brakes. Instead in those cases the existing energy is converted/dissipated with no requirement of an equal energy input. The kinetic energy in the system is relevant (it has to be dumped somehow), but the problem with stopping the earth and moon is more to do with preservation of momentum (and sheer scale required for any mechanical solution). – Neil Slater Oct 21 '15 at 21:21
  • That was my first point. Anyway the work done (energy) by the friction of the air or the brakes is surely equivalent to the kinetic bullet or car? – Varrick Oct 21 '15 at 21:29
  • If a 1kg mass travelling at $10ms^{-1}$ (50J) collides and sticks to 10kg mass travelling at $1ms^{-1}$ (5J) in the opposite direction, their momentums cancel, and they stop moving, even though the kinetic energies are not equal. The work done in the collision is 55J . . . and will probably raise the temperature of the new combined object. – Neil Slater Oct 21 '15 at 21:43
  • @NeilSlater ok I get that, but how do I correct my answer? – Varrick Oct 22 '15 at 08:04
  • Well the energies involved still give a sense of the scale of the task. I suggest 1) Remove the statement "The current energy these objects have is also the energy needed to stop them", because it is not true. 2) I also think your numbers are wrong, rotational kinetic energy of the Earth is $2.138×10^{29} J$, see https://en.wikipedia.org/wiki/Rotational_energy 3) Optionally. Compare the energies involved to feasible things we can do (e.g. atomic blasts are popular units of measurement) 4) I think that when using small objects (such as bombs) you are likely to need far more energy, not equal. – Neil Slater Oct 22 '15 at 08:34
  • @NeilSlater sorry to bring it back up, but your mass and stick example made the assumption that the mass would just stop. A lot of different things could happen depending on the density (binding energy) of the stick. Putting that example aside, and looking to find the "minimum" energy to stop an object. Let's attach a rocket to a moving object, facing the opposite direction the object is travelling in. How much chemical energy would be contained in the fuel required to stop the object? Assuming that all energy is converted to thrust, would it not be close to the kinetic energy of the object? – Varrick Oct 22 '15 at 15:42
  • The rocket/target example is almost identical to my example. If the rocket was a lot physically smaller than the object you are trying to stop, then assuming the masses combine, the rocket would need far more chemical energy to accelerate it than the kinetic energy of the target in order to bring it to rest (in any frame) - because energy is $\frac{1}{2}mv^2$ whilst momentum is $mv$ and you need the two momentums to be opposite and equal. It is easy to see that if you have two different values for $m$ and use a collision mechanism, then the kinetic energies have to be different. – Neil Slater Oct 22 '15 at 15:57
  • @NeilSlater if the rocket is attached to the object then it's mass is part of the mass of the whole thing... – Varrick Oct 22 '15 at 16:23
  • Oh sorry missed that. Energy doesn't convert to thrust directly (you need reaction mass, and we're back to momentum conservation here). But yes if you had some magical perfect propulsion then you could equate the energies. In practice you will need a lot more, like the collision scenario, unless you had a lot of reaction mass. – Neil Slater Oct 22 '15 at 16:33
  • So would it really be that much to say that the minimum amount of energy required to stop something via any method (and this is God doing the stopping we're talking about here) would be equal to the kinetic energy of the object? Obviously in the real world we don't get perfect efficiency but again, we're talking about a God's minimum. – Varrick Oct 22 '15 at 16:39
  • Sort of. It kind of works when you manipulate or oppose the effect of the energy like-for-like. Another thought: The spin of the Earth is actually energy that could be used for something . . . you could theoretically harness it to a generator and make electricity. In no way would that require the input of a matching amount of energy . . . – Neil Slater Oct 22 '15 at 16:50
  • How much energy did you use to build the harness? :P – Varrick Oct 22 '15 at 17:03
  • Well yes that may be a problem :-), but it isn't really part of the equation "how much energy does it take to stop the Earth". For instance, what if I already had built the harness for another planet and used it to extract enough energy to make fuel to move it to Earth . . . . – Neil Slater Oct 22 '15 at 17:05
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One word: impossible. Although I went to exorbitant lengths about a scientific explanation of Noah's flood in this question, but here it won't work.

Forget energy. The very concept is so immensely destructive, all life on Earth would be wiped out (except for some bacteria perhaps). Here is why:

Stopping The Sun Or Stopping Earth?

Your first question is about stopping the sun in midday. For this you have to actually stop Earth's rotation on its axis. As it happens, if you stop the solid part of Earth in one second, the momentum of wind and the oceans would literally rip things apart. The circumference of Earth is 24,901 miles. During 24 hours, Earth travels this much distance in a circular path. So everything on Earth (including oceans and the air) is rotating as a speed of 1037 miles per hour.

If you somehow stop Earth's solid mass from rotating (forget the energy and whatever), the momentum of air and oceans would be horrible. We are talking about a gale at speed ~1000 miles/h. For reference, category 5 hurricane has a speed of paltry 160 miles/h and the fastest wind speed recorded on Earth was in a cyclone at 255 miles/h. You can imagine yourself what would happen at ~1000 miles/h speeds.

And then the oceans. All oceans, seas, lakes and rivers would spill their waters eastwards at ~1000 miles/h. I don't want to go into the gory details, but it looks like most of (if not all) humanity would be killed in a very very horrible way.

Stopping The Moon

This one is no less disastrous. Even if you magically save Earth from the disastrous consequences of stopping its spin, this one would be equally deadly. Moon is the major source of tides on Earth. Stopping moon still around Earth on one spot would ... you know what ... start pulling it directly towards Earth in a straight line. Now talk about the one huge tide that would collect on one side of Earth.

Considering that moon does not slam into Earth and completely obliterate its existence within the 1 day of its stoppage, the huge tidal wave collecting on moon's side of Earth would destroy several cities. And once moon starts revolving around Earth again, that tidal wave would retreat and cause a horrible tsunami on the other side of the oceans. The ensuing destruction would be far greater than that of phase 1.

Furthermore, the tidal effect of moon's gravity on Earth's atmosphere can also not be neglected. Once concentrating most of the air on one side of Earth would create terrible storms and then suddenly releasing that amassed air to be equally distributed again would cause terrible storms again ... only in the opposite direction.

Conclusion

Foregoing the energy concerns for the task at hand, and the impossibility involving in delivering that energy to Earth and moon, the very consequences of carrying out the task would be so disastrous and immense that all multicellular life (exclusing some lucky flies or fleas maybe?) would be wiped out.

Deduction: Don't try this at home!

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Youstay Igo
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  • Seems like this isn't impossible, you just need to stop everything as one (not just the solids) and carefully control the gravity of the moon. – NPSF3000 Oct 21 '15 at 11:21
  • More like magic than science, if you ask me. – Youstay Igo Oct 21 '15 at 11:27
  • That's kinda the point isn't it? – NPSF3000 Oct 21 '15 at 11:34
  • It is. Of corpse! – Youstay Igo Oct 21 '15 at 11:35
  • @YoustayIgo "Any sufficiently advanced technology is indistinguishable from magic." - Arthur C. Clarke – Howard Miller Oct 21 '15 at 15:30
  • Yes indeed. But I find no relevance to this quote with this question or answer. You cannot expect us to answer with future technology aka magic. Our knowledge is limited to what we know and that is never magic. Magic is what a person from past would feel about a technology of future. The question above has physics, solar-system and religion tags, but magic (or outrageously advanced futuristic technology) is not allowed. – Youstay Igo Oct 21 '15 at 15:53
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Since the whole point was to give the army enough time to fight the enemy, and the Bible talks about the sun and the moon standing still as seen by the Jews, the most straightforward way is to accelerate (many times) their time perception. This has been done many times in fiction since the Bible, e.g. the classic Common Time by James Blish.

There are of course tons of problems, starting with light redshifting, gravity, air resistance etc. But nothing insurmountable for an omnipotent being.

Radovan Garabík
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  • How would this use less energy than the other methods, though? – March Ho Oct 23 '15 at 12:49
  • @MarchHo If done correctly, it wouldn't require any extra energy, since you are not moving any celestial bodies. The time accelerated field affects only the bodies of the soldiers (and maybe their surroundings, to let them breathe and strike & cut their enemies). – Radovan Garabík Oct 23 '15 at 12:54
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This answer is a bit late, but the most economic approach is a really powerful drug.

I am a layman, but I think with enough psychological conditioning and a really advanced mix of mind-influencing chemicals it could actually be possible to craft such an experience. In all cases, its easier than all the other approaches.