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Author Topic: Can cow farts make the Earth rotate faster?  (Read 56997 times)

Offline Bored chemist

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Can cow farts make the Earth rotate faster?
« Reply #50 on: 12/07/2011 19:46:03 »
"Now, when a cow farts, there is also a redistribution of mass (and a very small amount of vectored thrust due to the accelerated mass of exhaust gas), soooo, there is a change in angular velocity, and because there was also a redistribution of mass, the angular velocities of the components of the system are under no obligation to return precisely to their former values."

That same redistribution of mass will happen whichever way the cow is facing.
It happened yesterday, and it will happen tomorrow.
The carbon cycle (and it's friends)will ensure that, at whatever rate cow farts add methane to the air at an altitude of roughly a meter, other processes will return it (otherwise the concentration of methane in the air would increase continuously).

The "vectored thrust" you talk of is also a non starter. For a start, all thrust is a vector.
More importantly, unless you think that a cow's fart continues round the world forever, you must accept that it's brought to a halt (wrt the earth) by viscosity. The KE is degraded to heat and any momentum is transferred back to the system.

To whatever extent cow farts affect the spin of the earth, they already have done so.

I agree that, if you don't consider the atmosphere as part of the earth then you can change the angular momentum of either by transferring momentum to the other.
It's just that such a dissection isn't sensible because the two are locked together by friction/ viscous drag.
The earth rotates once a day,and so does the air.
As I have said several times now, there is not a thousand mile per hour wind at the equator.

You cannot sensibly consider the rotation of the atmosphere separately from the rotation of the earth (except for a rather short time).
 

Offline Geezer

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Can cow farts make the Earth rotate faster?
« Reply #51 on: 13/07/2011 00:41:54 »
It's true that the methane will eventually be removed from the atmosphere, but that's not exactly a rapid process. However, I accept that the whole debate is really silly!

It does prompt a more serious question though. In the past, large amounts of gas have been pumped into the atmosphere by volcanoes. I wonder if those emissions were great enough to alter the moment of inertia of the Earth/atmosphere system and alter its rate of rotation?
 

Offline Airthumbs

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Can cow farts make the Earth rotate faster?
« Reply #52 on: 13/07/2011 01:51:02 »
It is silly question Geezer which has had a fantastic amount of scientific input. You raise a very valid point, with regard to events such as volcanoes.  How do the forces of nature effect the rotation of planets.   One example for me, supposedly huge amounts of freshwater have been stored in Dams that have shown to cause a minuscule effect to the rotational speed of the Earth.  So redistribution of mass can effect the rotation of the Earth.  I would then ask if the tides in the oceans cause changes, as huge amounts of water are displaced everyday.  I suppose they would do but as they are cyclic the tides cancel the effect.  Could the sheer mass of water moved even contribute towards events such as Earthquakes even?

I would imagine that Olympus Mons has had some kind of effect on the rotation of Mars....




 

Offline Bored chemist

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Can cow farts make the Earth rotate faster?
« Reply #53 on: 13/07/2011 20:56:36 »
The earth is smoother than a billiard ball.
The effects of mountains are tiny and those of anything else are practically non existent.

Methane in the air lasts about 10 years, but that's not the point. The cows fart constantly and the gas is removed constantly so the overall concentration (and distribution) is constant.
 

Offline Airthumbs

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Can cow farts make the Earth rotate faster?
« Reply #54 on: 14/07/2011 05:54:18 »
The earth is smoother than a billiard ball.

And if you were to redistribute the mass on a billiard ball you may also find that this effects its rotational axis.....
 

Offline Bored chemist

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Can cow farts make the Earth rotate faster?
« Reply #55 on: 14/07/2011 07:00:31 »
The earth is smoother than a billiard ball.

And if you were to redistribute the mass on a billiard ball you may also find that this effects its rotational axis.....

Indeed, for example, if I moved all the mass a metre to the left, then I would move its rotational axis a metre to the left.
However, if it started and d=ended billiard ball shaped, then I wouldn't affect its moment of inertia. (assuming uniform density)
 

Offline Airthumbs

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Can cow farts make the Earth rotate faster?
« Reply #56 on: 14/07/2011 07:44:09 »
The earth is smoother than a billiard ball.

And if you were to redistribute the mass on a billiard ball you may also find that this effects its rotational axis.....

Indeed, for example, if I moved all the mass a metre to the left, then I would move its rotational axis a metre to the left.
However, if it started and d=ended billiard ball shaped, then I wouldn't affect its moment of inertia. (assuming uniform density)

Just how big are your billiard balls?  I said redistribute the mass on a billiard ball, I am pretty sure I did not say move it a meter to the left?
 

Offline Bored chemist

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Can cow farts make the Earth rotate faster?
« Reply #57 on: 14/07/2011 18:45:54 »
Sorry, it was a bit early in the morning. I read it as "the mass of...".
What I should have said was that if I redistribute the mass by rotating it through 180 degrees I might not find that the axis had changed.
The point remains that if it starts and ends billiard ball shaped, then the moment of inertia stays the same.
A better analogy might be that if I stripped the paint off a ball, then put it back, I wouldn't alter the moment of inertia very much.
« Last Edit: 14/07/2011 18:47:49 by Bored chemist »
 

Offline JP

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Can cow farts make the Earth rotate faster?
« Reply #58 on: 14/07/2011 19:29:56 »
And bear in mind we're talking about gas here, which will tend to redistribute fairly smoothly about the earth, rather than lumping to one side.  So I'd expect the axis of rotation would remain constant.

A bit off topic, but with the big earthquakes recently, it's been found that when the mass of the earth shifts a little in such an earthquake, the rate of rotation of the earth changes because of the change of it's moment of inertia: http://www.csmonitor.com/Science/2011/0314/Japan-earthquake-accelerated-Earth-s-rotation-study-finds 
 

Offline Geezer

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Can cow farts make the Earth rotate faster?
« Reply #59 on: 14/07/2011 21:48:47 »
For those that care to do the math, the mass of the Earth's atmosphere is about a million times less than the solid/liquid mass, and 90% of the mass of the atmosphere is less than 10 miles above the surface. So, even if all of the atmosphere was to suddenly disappear, it would not affect the angular velocity of the Earth very much, although it would make a measureable difference (assuming there was anyone still around to make the measurement.)
 

Offline JP

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Can cow farts make the Earth rotate faster?
« Reply #60 on: 14/07/2011 21:53:33 »
So if the cows let 'em rip with high enough velocity, could they eject the earth's atmosphere into space?
 

Offline Geezer

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Can cow farts make the Earth rotate faster?
« Reply #61 on: 14/07/2011 22:13:28 »
So if the cows let 'em rip with high enough velocity, could they eject the earth's atmosphere into space?

You'd probably only get enough acceleration to do that if the methane was ignited (very carefully.)
 

Offline Geezer

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Can cow farts make the Earth rotate faster?
« Reply #62 on: 15/07/2011 04:35:40 »
......or, we could turn it around a bit and consider how many cows it would take to release enough methane to form an explosive mixture that would consume all of the oxygen in the Earth's atmosphere in a single explosion.
 

Offline damocles

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Can cow farts make the Earth rotate faster?
« Reply #63 on: 18/07/2011 10:25:11 »
The greenhouse gases in the cows' flatulence will likely cause global warming, which will start to melt the Greenland and Antarctic ice caps, which will lead to a net redistribution of mass from poles towards equator, which will slow the earth's rotation (like a skater putting her arms out). No need to even get your cows to line up!
 

Offline Airthumbs

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Can cow farts make the Earth rotate faster?
« Reply #64 on: 18/07/2011 12:18:39 »
Anyone know what the current world pop. is of cows and how much gas they produce on average each day.  Of course we should include all ungulates but the task of calculating their output is inflammatory!  And what is the amount of methane needed to cause the possibility of combustion at sea level in our atmosphere?

I have not heard of a farmer blowing up their cowshed due to methane buildup?
 

Offline Geezer

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Can cow farts make the Earth rotate faster?
« Reply #65 on: 18/07/2011 17:44:43 »
I have not heard of a farmer blowing up their cowshed due to methane buildup?

I did read of a case not so long ago where several people on a farm were asphyxiated by methane. If I remember, it was released from a slurry pond.

http://www.usatoday.com/news/nation/2007-07-04-va-farm_N.htm
« Last Edit: 18/07/2011 17:48:41 by Geezer »
 

Offline Bored chemist

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Can cow farts make the Earth rotate faster?
« Reply #66 on: 18/07/2011 20:51:27 »
There's a James Herriot story about a cow with bloat setting fire to a shed when they treated it.
 

Offline Airthumbs

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Can cow farts make the Earth rotate faster?
« Reply #67 on: 19/07/2011 03:22:04 »
I have not heard of a farmer blowing up their cowshed due to methane buildup?

I did read of a case not so long ago where several people on a farm were asphyxiated by methane. If I remember, it was released from a slurry pond.

http://www.usatoday.com/news/nation/2007-07-04-va-farm_N.htm

That is quite a sad story Geezer  [:-[]

I think I have read all of James Herriot's Vet books.... used to make me laugh a lot!
 

Offline Bored chemist

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Can cow farts make the Earth rotate faster?
« Reply #68 on: 19/07/2011 19:12:56 »
The conclusion seems to be that cow farts don't speed the earth up (no matter which way they are facing) for any length of time and they may slow it down (depending on whether or not the methane levels in the atmosphere attributable to cows are stable).
 

Offline JP

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Can cow farts make the Earth rotate faster?
« Reply #69 on: 19/07/2011 21:40:17 »
The conclusion seems to be that cow farts don't speed the earth up (no matter which way they are facing) for any length of time and they may slow it down (depending on whether or not the methane levels in the atmosphere attributable to cows are stable).

Wasn't the conclusion that they can speed it up for a very short length of time (that we never determined), but that this effect would be short-lived due to friction/air resistance?
 

Offline damocles

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Can cow farts make the Earth rotate faster?
« Reply #70 on: 20/07/2011 00:57:28 »
I think the issue that Bored chemist had picked up on was that the consequences of the methane buildup in the atmosphere slowing down the earth, small as they are, far outweighed any effect, transitory or not, due to reactive torque.

Or in simpler language:
-- A lot of cows facing in one direction and letting rip might (or might not) provide a short term rocket-like kick that would speed up the Earth's rotation.
-- That effect, even if it existed, would be minute.

HOWEVER

If the polar icecaps of the Earth were to melt a little, there would be a movement of material from the poles to the tropics.
-- This would slow the Earth's rotation by increasing its moment of inertia
-- The effect would also be minute, but much greater than that arising from any rocket-like torque
-- Such a melting could be (and probably is being) triggered by a build up of methane and CO2 in the atmosphere.
-- Cow flatulence is triggered by methanogenic microorganisms --  C6H12O6 (sugar/cellulose) --> 3 CH4 + 3 CO2
 

Offline Bored chemist

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Can cow farts make the Earth rotate faster?
« Reply #71 on: 20/07/2011 18:48:14 »
OK, Poor phrasing on my part.
When I said "for any length of time" I meant it in the vernacular sense (i.e. "any significant length of time") rather than the literal sense.
 

Offline JP

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Can cow farts make the Earth rotate faster?
« Reply #72 on: 20/07/2011 19:38:27 »
BC: then I agree.
 

Offline Geezer

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Can cow farts make the Earth rotate faster?
« Reply #73 on: 21/07/2011 00:01:44 »
Well, see, it's pretty obvious really. The question was;

"Can cow farts make the Earth rotate faster?"

In fact, cow farts actually make the Earth rotate more slowly. This is because they are continuously converting "Earth mass" (grass etc.) into "atmospheric mass" in the form of methane. This results in a slight, but real, increase in the moment of inertia of the Earth/atmosphere system.

If all the cows were to suddenly stop producing methane, the moment of inertia would decrease, and the Earth would take less time to rotate.
 

Offline Airthumbs

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Can cow farts make the Earth rotate faster?
« Reply #74 on: 21/07/2011 10:07:37 »
What you are forgetting is total historical contribution for cow farts!  A lot of cow fart is locked up in the form of methane in massive quantities below the ocean and vast areas of land currently in a state of permafrost and melting! 


image:www.kobashi.co.uk
You might say that the energy from a cow fart is dissipated, and that would be in line with the theory of infinite dilution.  One molecule of methane, absorbs 20 times the amount of infra red radiation then that of Carbon Dioxide, making it a far more efficient green house gas.

So all that trapped cow fart is going to be released into the atmosphere.  If all of the gas was exploded in one place on earth, the resulting explosion would definitely have an effect of the earths rotational axis, haha!

Admittedly all the cows over history passing gas have not been standing in the same direction whilst doing so.  ::)


image:www.anorak.co.uk

Just look at all that energy! What a waste...  :o
« Last Edit: 21/07/2011 10:10:04 by Airthumbs »
 

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Can cow farts make the Earth rotate faster?
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