Science: Energy: Bioenergy
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Give earthlike planets a kickstart

Earthlike planets that have little or no rotational motion will produce very little life, if any. This idea is for a manless spaceship with enough explosives to induce rotation in a small planet (I'm guessing a few Teratons of TNT in the form of nuclear warheads could be stuffed into canyons and aimed with a nonsymmetrical blast radius to induce a massive momentum into the side of the canyon wall and thus spinning the planet.

edit: by canyon walls I mean sea cliffs and mountian bases (no opposite sides).
-- daseva, Oct 29 2007

If you shaped the teraton charge... http://www.llnl.gov/str/Baum.html
...I suspect you'd just punch a hole. [pertinax, Oct 29 2007]

Blast the earth http://www.lpl.arizona.edu/impacteffects/
[Klaatu, Oct 31 2007]

I'll defer to the resident explosives experts, but I'd have thought that this wouldn't work in a canyon; the other side of the canyon would surely take almost as much of a hit as the side where you stuck the bombs. I know you can direct the force from, say, the warhead of an anti-tank missile, but I'd be surprised if the shockwave from a teraton nuke could be tamed in the same way.

Wouldn't you really need to find something more like a sea-cliff, where there's no equal-and-opposite cliff between bomb and horizon?
-- pertinax, Oct 29 2007


Yes, yes that sounds better, thanks [pertinax]. I agree that the probablility of being able to do this remains quite low at the moment.

It's like waking up the dormant lifeforce in the universe, all very positive and foreward thinking.
-- daseva, Oct 29 2007


Wouldn't the explosions need to be outside the atmosphere?
-- neutrinos_shadow, Oct 29 2007


Strange category, unless it's actually a metaphor for getting yourself into a spin.
-- xenzag, Oct 29 2007


[neutrinos_shadow],surely the non-rotation of the atmosphere would simply give you a gentle East wind (i.e., a wind which, from the point of view of someone standing on the ground, would seem to come from the direction of sunrise).

Gentle, but somewhat radioactive.
-- pertinax, Oct 29 2007


Mmm. I reckon you would just get a big hole too, but we need to get off this rock sooner or later. Be nice to have a place to go. Terraforming is a good start, perhaps a more gentle approach?
-- the dog's breakfast, Oct 29 2007


"...and there we were, planning our hol's to the sunny side, when some massive explosion knocked us off our feet. I'm goin' to get my money back, 'cos now it's only sunny for half the time. Damned inter-galactic do-gooders."
-- Ling, Oct 29 2007


[marked-for-deletion] This is bad science. For reasons of conservation of angular momentum, your explosion won't do anything at all. You can't simply create angular momentum with an explosion. It will push on the cliff face, but it will push on the air in the opposite direction as well. Equally. That air will eventually transfer its momentum to the planet, and you'll be back where you started.
-- ldischler, Oct 29 2007


Or not. If I jump off a small boat, the boat moves. The air around me dosen't whip back around to catch the boat.
-- daseva, Oct 29 2007


You, your boat, and the air are not in a closed system. You're pushing the boat precisely because you're leaving it - you go to one side, balancing the movement of the boat to the other. The explosive blast isn't leaving the earth; it stays within the atmosphere.
-- jutta, Oct 29 2007


Yes, [jutta]. The warhead casings would go flying!

Note that we are using directional explosions. They perfer to explode into the wall, thereby pushing it as the casings go bye bye probably up into space.

Also, note that it may be possible to aim the explosions into the surface of the planet at some angle and still impart an overall tangential force. So, we can angle lower into the planet to ensure elimination of the casings. This might be essential as [jutta] points out (something has to leave the planet).
-- daseva, Oct 29 2007


//Note that we are using directional explosions.//
Doesn't matter. Even directional explosives don't break the conservation of momentum laws.
-- ldischler, Oct 29 2007


Besides, explosives aren't as efficient as chemicals with less snap to them. The best way to try this wouldn't involve explosives at all. But I'm not going to try to explain a good way to spin up a planet. I'm just gonna say it's going to take a whole lot more energy than you'd ever think (--look at tidal energy and think in billions of years).

Bad method, bad science, bad fish.
-- baconbrain, Oct 29 2007


//Earthlike planets that have little or no rotational motion will produce very little life, if any.// Says who?
-- nuclear hobo, Oct 29 2007


I was about to ask if anyone had done the calculation, or was the "few Teratons" just plucked out of thin air? The rotational energy of the Earth (as an example) is something on the order of 10^22 or 10^23 Joules. So, if you want to spin an earth-sized planet up to earth-like speeds, that's how much energy you need to put in. Strangely enough, a teraton of TNT is about 0.4 x 10^22J, so a few teratons of TNT would do nicely.

You would have to use that energy to eject some stuff (maybe an alp or two) into space, at a tangent to the planet's surface. Otherwise (as some have noted), conservation of angular momentum takes hold and all you ewnd up with is a non-rotating planet with a large dent. You'd probably also want to do this symmetrically on opposite sides of the planet.

It would be quite cool to make the planet spin north-over-south instead of east-about-west.
-- MaxwellBuchanan, Oct 29 2007


Thanks, [MB]. Insightful.

[21], the dependence on lifeforms and rotational activity is assumed due to the prevalance of biorhythms and the conditions on earth. A cycle, at some point, is necessary.
-- daseva, Oct 29 2007


//The rotational energy of the Earth (as an example) is something on the order of 10^22 or 10^23 Joules.//
According to a calculation on Wikipedia, the figure is roughly 2.6E29 J. (Probably a bit less since they assumed uniform density.)
-- ldischler, Oct 29 2007


OK, so going with [MaxwellBuchanan]'s explanation, and supposing we're going for conventional rotation (sunrise in the East), we find the eastern side of a mountain and dig a very large L-shaped sapper's mine (first down, then westward), preferably close to existing fault-lines in the rock.

Then, we dig some more, to the north and south, getting shallower in each direction, until we have a striped approximation to the cone of a shaped charge. I'm supposing we couldn't make an actual, continuous cone without making the tunnels collapse.

Then, we pack the tunnels with nuclear explosives (maybe more in the horizontal tunnels, because of the need to overcome gravity), light the blue touch paper and retire to a safe distance.

If this works, then I suppose it could also give us an extra moon.
-- pertinax, Oct 30 2007


//The dependence on lifeforms and rotational activity is assumed due to the prevalance of biorhythms and the conditions on earth. A cycle, at some point, is necessary.//

That is, if you'll pardon me saying so, a circular argument. Big things that live on the surface or in shallow water have adapted to day/night because it would be boorish not to. But most living things (bacteria) generally don't bother about diurnal or any other cycles. Likewise, things that live in the deepths of the ocean generally don't bother about night/day or even tidal motions.

There's no fundamental reason why you need diurnal variation for life, other than to make sure that one face of the planet doesn't freeze while the other toasts.
-- MaxwellBuchanan, Oct 30 2007


Perhaps, but might there be some geological activity arising from the rotation that begets even the deep ocean lifeforms?
-- daseva, Oct 30 2007


[daseva] The only thing we are less knowledagble about than life on Earth is life elsewhere in the universe.
-- nuclear hobo, Oct 31 2007


From experience, the Sun must rise in the East for life to evolve.
-- Ling, Oct 31 2007


//Perhaps, but might there be some geological activity arising from the rotation that begets even the deep ocean lifeforms?// Perhaps, but perhaps not. In the case of Earth, I'm pretty sure that our rotation doesn't cause any significant geology. In the case of places like Europa, tidal forces caused by its rotation relative to its parent body, Jupiter, cause massive tidal forces that probably keep its deep oceans liquid. But the the tides (both solar- and lunar-powered) on Earth aren't all that significant; some life has had to adapt to them, but that's about it.
-- MaxwellBuchanan, Oct 31 2007


1. Drive a post into the ground. 2. To that post attach several hundred thousand miles of carbon fiber nano-rope. 3. Wrap that around the planet a whole bunch of times. 4. Throw those teratons of nukes into a propulsion device attached to a rocket. 5. Light it up. 6. Spin that planet like a top.
-- Noexit, Oct 31 2007


7. Pull it a little out of orbit in the process.
-- RayfordSteele, Oct 31 2007


I think it would take a LOT of nukes to do this. I have supplied a <link> where you can impact the earth with different-sized objects at varying speeds and angles. Most produce no effect.

Added: I impacted the earth with an object 120 miles in diameter at a velocity of 25 km/s at an angle of 45° and got:

Energy before atmospheric entry: 2.23 x 1028 Joules = 5.34 x 10^12 MegaTons TNT

The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.
The impact does not shift the Earth's orbit noticeably.
-- Klaatu, Oct 31 2007


Alright, [klattu], for a given simulation here are my answers:

Major Global Changes: The Earth is not strongly disturbed by the impact and loses negligible mass.
100.00 percent of the Earth is melted
The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.
The impact does not shift the Earth's orbit noticeably.

So, melted but not damaged. Ok, I'm sceptical.
-- daseva, Oct 31 2007


I'm pleasantly amazed that the energy needed to melt the earth is much less than the energy need to alter its rotation. Learn something new every day.
-- MaxwellBuchanan, Oct 31 2007


I picked a 5000 mile impactor, and I still didn't get a rotation change. Of course, there was no longer an earth to rotate: "The Earth is completely disrupted by the impact and its debris forms a new asteroid belt orbiting the sun between Venus and Mars."
-- ldischler, Oct 31 2007


//I picked a 5000 mile impactor, and I still didn't get a rotation change.//

Try 2500 mile - 10000 density - 30 km/s - angle 25° - Crystalline impact. You will get rotational changes. It only melts 1/2 the earth.

The interesting thing is the mind-boggling yield it takes to efect a change in planet rotation.

Be sure to put yourself 10,000 miles from impact. It still won't save you, but:
"Your position is in the region which collapses into the final crater."
-- Klaatu, Nov 01 2007


I missed this one. Gotta (+) it because I wondered the same thing.
You are all thinking in terms of throwing more and more force at a planet to spin it, but much less force in the form of a standing wave which attained harmonic resonance would eventually speed up a planet without all the destruction.
Focussing waves through the mantle to converge and pulse within the core itself would probably be the most effective but it could be done from the surface as well.
-- 2 fries shy of a happy meal, Oct 10 2011


I am wondering why continual heat from the sun on one side of the planet creating wind movement over a period of time does not gradually cause the planet to slowly begin to revolve?
-- Ah Supp, Oct 10 2011


[Ah Supp] -- I suddenly realize I am a microcosm of that system and may have discovered a corollary! Continual heat from the metabolic processes initiated by the over-consumption of baked beans and egg salad sandwiches created forceful (dare I say explosive) tail winds of a magnitude never before experienced by a crowded grocery store check out line causing all OTHER bodies in that celestial market to rotate. Me, not so much. Bitter Irony, thy name is GROG. Wait a minute --- what were we talking about?
-- Grogster, Oct 10 2011


Shirly conservation of angular momentum is no limitation if the explosion blows some mass (atmosphere, say) into space? Really large fusion bombs can do that.
-- mouseposture, Oct 10 2011


Good explanation Grogstar. Think you might have made a quantum leap onto the chuck wagon scene from "Blazing Saddles" somewhere along the line
-- Ah Supp, Oct 11 2011


A ball of iron with a diameter of a mere 1,800,000 meters sent at a speed of 30 kilometers per second and an angle of 1 degree to the ground could spin up an earth sized planet to one rotation per 24 hours without melting more than 1.5% of it.

As a bonus you would be left with quite a nice moon.
-- Voice, Oct 11 2011


Why don't you just ask Q to modify the local value of the Gravitaional Constant ? If he thinks it will annoy the hell out of Jean-Luc Picard, he'll do it for free.
-- 8th of 7, Oct 11 2011


The thing is, there probably aren't any lifeable planets without spin.

All planets form with spin, by reason of the way they form. The only way they can lose that spin is by tidal forces, which will only be a problem if they are embarrassingly close to their star and therefore probably too hot anyway.
-- MaxwellBuchanan, Oct 11 2011


//be a problem if they are embarrassingly close to their star//

This, and //Dumbth// is what I am taking away from the halfbakery, today.

Thankyou, so very much. Each and every one of you.
-- MikeD, Oct 12 2011



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