Can cow farts make the Earth rotate faster?

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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).
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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?
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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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....


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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.
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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.....
Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction. (Einstein)

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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)
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Offline Airthumbs

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« 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?
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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 »
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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 

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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.)
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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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?

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Offline Geezer

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« 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.)
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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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.
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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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!
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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?
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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 »
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Offline Bored chemist

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« 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.
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Offline Airthumbs

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« 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!
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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).
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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?

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Offline damocles

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« 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
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Offline Bored chemist

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« 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.
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Offline JP

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« Reply #72 on: 20/07/2011 19:38:27 »
BC: then I agree.

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Offline Geezer

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« 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.
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline Airthumbs

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« 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! 

[attachment=14901]
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.  [::)]

[attachment=14899]
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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Offline CliffordK

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Can cow farts make the Earth rotate faster?
« Reply #75 on: 23/07/2011 01:30:23 »
If everyone stood up in a parked school bus (in neutral) and threw their book bags at the same instant towards the back of the bus, it would (theoretically) propel the bus forward for an instant.  Until the books slammed into the back of the bus.  At which point the movement of the bus would stop again.

Likewise, if everyone stood up, bent forward, and let some flatulence go...   
Well, the net effect on the bus would be nil, but people might be sent screaming out of the bus!!!!!!!

If you consider the earth as a closed system like the school bus, then the net effect will be nil.  However, if it was time synchronized, one might be able to imagine a slight bump, returning to zero, like the instant while the books were still flying through the air.

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Offline Bored chemist

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« Reply #76 on: 23/07/2011 16:05:31 »
Great analogy; I wonder if Geezer accepts it.
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Offline Geezer

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« Reply #77 on: 23/07/2011 17:37:14 »
Great analogy; I wonder if Geezer accepts it.
Almost, but not quite.

The bus was accelerated, therefore it was "made to move faster". Then it slowed down again and stopped.

However, the bus did not return to its original position, so we can't say the net effect was nil.
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline Airthumbs

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« Reply #78 on: 23/07/2011 18:45:21 »
What if the bus was propelled by a certain gas produced by the animal in question?  [;D]
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Offline Geezer

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« Reply #79 on: 24/07/2011 00:20:13 »
What if the bus was propelled by a certain gas produced by the animal in question?  [;D]

Well, then it would have to be green, wouldn't it?
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Offline damocles

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« Reply #80 on: 24/07/2011 02:33:33 »
A bit of lateral thinking -- nothing to do with animal flatulence

If we arranged for every city in the Northern hemisphere to have a one-way traffic system where vehicles were constrained to work in a clockwise direction, and a similar system where every city in the Southern hemisphere forced vehicles to circulate in an anti-clockwise direction, we might make a much more substantial contribution to speeding up the earth's rotation!

Even if the road rules in North America and Europe changed to drive on the left, vehicles would travel clockwise around roundabouts, and that could contribute.
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Offline Geezer

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« Reply #81 on: 24/07/2011 03:28:54 »
vehicles would travel clockwise around roundabouts, and that could contribute.

Not in Italy or Boston. They would drive straight across the roundabouts there.
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Offline Bored chemist

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« Reply #82 on: 24/07/2011 14:41:51 »
Great analogy; I wonder if Geezer accepts it.
Almost, but not quite.

The bus was accelerated, therefore it was "made to move faster". Then it slowed down again and stopped.

However, the bus did not return to its original position, so we can't say the net effect was nil.

For an ideal, "physics question" type frictionless bus, the C of G of the bus/ bags/ school-kids system would end up in exactly the same place that it started.

So we can say the overall effect was practically nil (except that the bus would be slightly warmer and bigger afterwards).

The analogous effect of the cow farts would be that one day would be slightly shorter, but that for all subsequent days the day length would be the same. You would introduce a change in phase, but not frequency, of rotation.

Also, the vehicles on the roundabouts have the same problem. They are part of the earth/ air/ cow/ fart/ vehicle system, and can not influence the overall angular momentum of the system.
There would be short term effects, but they would stop when the cars stopped or left the roundabouts. In particular, most effects would be cancelled out when the vehicles drove home.
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Offline damocles

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« Reply #83 on: 24/07/2011 15:55:12 »
From Bored Chemist:
Quote
Also, the vehicles on the roundabouts have the same problem. They are part of the earth/ air/ cow/ fart/ vehicle system, and can not influence the overall angular momentum of the system.
There would be short term effects, but they would stop when the cars stopped or left the roundabouts. In particular, most effects would be cancelled out when the vehicles drove home.

NO, that is the whole point of the one way systems and roundabouts. The movement of traffic, both morning and evening, would have a continuing vorticity in the same direction that would have to be deducted from the conserved angular momentum of the earth's rotation on a continuing basis.

Angular momentum (earth + traffic) is conserved. SO if we manipulate angular momentum (traffic) on a continuing basis, we make a real and lasting change in angular momentum (earth).

The traffic flow could not alter the total angular momentum of the earth system as bored chemist rightly points out. But it could lengthen or shorten the day, because the traffic makes a contribution to the system angular momentum that is separate from and independent of the contribution from the earth's rotation.
« Last Edit: 24/07/2011 16:03:36 by damocles »
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Offline Geezer

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« Reply #84 on: 24/07/2011 16:41:15 »

You would introduce a change in phase, but not frequency, of rotation.


Say what? How do you change phase without altering frequency?
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Offline Bored chemist

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« Reply #85 on: 25/07/2011 09:36:51 »

You would introduce a change in phase, but not frequency, of rotation.


Say what? How do you change phase without altering frequency?

I used to get up at 08:30 to go to work each day, but I changed my job.
Now I get up at 06:30.
That's a change in phase but it was always once a day so the frequency is the same.
The Sunrise does the same thing every day, it's once a day but the phase changes WRT noon.

The traffic will make a difference while it's in motion but if there's ever a moment when all the traffic stops - say the World cup final- then the speed of the earth will be just the same as it was before. Same with the cow farts, once they come to rest there's no effect on the spin.

As I said, if the cows faced East and started walking they would change the rotation rate slightly. The cars on roundabouts are much the same.

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Offline Geezer

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« Reply #86 on: 25/07/2011 19:23:31 »

I used to get up at 08:30 to go to work each day, but I changed my job.
Now I get up at 06:30.
That's a change in phase but it was always once a day so the frequency is the same.
The Sunrise does the same thing every day, it's once a day but the phase changes WRT noon.


Frequency is just the reciprocal of period (the interval between cyclic events). The interval had to change to produce a change in phase. Mathematically, it's impossible to change the period without changing the frequency.

The change in frequency may have been temporary, but it still had to change to produce a change in phase.
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline Bored chemist

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« Reply #87 on: 26/07/2011 19:03:46 »
If you picked the right day then the change in period was 2 hours in one day- about 8%.
If you loot at it over the course of a week then it's just over 1%. That year the average change was about 0.02%.
But this is a one off event so you have to average it over the whole of time. The mean change in frequency was zero.
Also, something that happens at 06:30 one day, but at 08:30 the next isn't a "cyclic event" because it doesn't repeat; It's not cyclical.
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Offline Geezer

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« Reply #88 on: 26/07/2011 20:05:54 »
Yes, but the frequency still changed.
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline Bored chemist

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« Reply #89 on: 27/07/2011 01:01:55 »
Yes, it changed by zero.
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Offline Geezer

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« Reply #90 on: 27/07/2011 07:12:26 »
Yes, it changed by zero.

Ah, right! You must be using the "new math" then. Either that or you have some previously unknown proof that frequency and period are not reciprocals up your sleeve, or perhaps you believe the period didn't actually change?



There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline Bored chemist

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« Reply #91 on: 27/07/2011 18:31:03 »
OK, it was 1/86400Hz before and it was 1/86400Hz afterwards.
What does old maths give as the difference between those?

There was a change, but that was a one off event; it doesn't have a frequency (unless you count zero).
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« Reply #92 on: 27/07/2011 20:13:39 »
OK, it was 1/86400Hz before and it was 1/86400Hz afterwards.
What does old maths give as the difference between those?

There was a change, but that was a one off event; it doesn't have a frequency (unless you count zero).


Perhaps you are thinking that frequency can only be determined by timing entire cycles? That's not necessary. We only need to know angular velocity.

If we plot the angular velocity against time and do a Fourier transform on it, we'll see lots of interesting changes in frequency when the angular velocity is changing.
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« Reply #93 on: 27/07/2011 22:31:51 »
What apodisation did you plan to use for the FT?
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« Reply #94 on: 27/07/2011 23:25:55 »
What apodisation did you plan to use for the FT?

Enough to prove that the frequency changed.
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« Reply #95 on: 28/07/2011 12:16:24 »
What apodisation did you plan to use for the FT?

Enough to prove that the frequency changed.

Please show your working

My hypothetical change of job happened on April 1st this year so, in a sense, rather than being 24 hrs long, that day was just 22 hrs.
Now, you can do an FT on a pulse lasting 22 hrs and come out with a nice "spectrum". If I remember rightly it comes out as a sinc function. Sure, it will have a dominant component at a frequency of 1/22 hrs^-1, but that's just a mathematical result.
It doesn't have a meaning.
There is no way that you can say that April 1 2011 has a frequency of "every 22 hrs" because it doesn't repeat itself.
It actually has a frequency of once in the whole of time.
1/ infinity is practically zero.
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« Reply #96 on: 28/07/2011 18:44:06 »

Please show your working


I've got a better idea. You show how frequency is not the reciprocal of period.
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« Reply #97 on: 28/07/2011 21:53:11 »
BTW BC, your "change in job" analogy is a load of twaddle a bit suspect.

The Earth's frequency is a function of its angular velocity. The time at which you start work has nothing to do with your angular velocity, so there was no phase shift in that case.
 

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« Reply #98 on: 29/07/2011 00:54:39 »
The Earth's frequency is a function of its angular velocity. The time at which you start work has nothing to do with your angular velocity, so there was no phase shift in that case.

The Earth's frequency... is that the Schumann thingy me bob?  Angular velocity, sounds like the kind of math you would need to determine the outcome of my original post which has somewhat drifted a wee bit, not that I mind as to be honest this thread was destined for the manure heap from it's conception.  98, 99 100....  [:P]
Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction. (Einstein)

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« Reply #99 on: 29/07/2011 15:30:34 »
Something that happens once, and only once doesn't have a frequency. It doesn't matter how long it takes, Only things that repeat have a meaningful frequency.
My granny may have lived for a hundred years, but she didn't live ten times per millennium.

And I'm sorry you don't understand that my working day and the earth's rotation have a simple fixed phase relation, except once when I changed it.
I used to get up at 08:30, that's about 60 degrees of the earth's rotation before the Sun is overhead. Now I get up at 06:30; that's about 90 degrees before noon. (I'm ignoring the half hours to keep the arithmetic easy.)
The change of 30 degrees is a real phase shift.
(obviously I'm simplifying it by also ignoring weekends, BST, and such)
« Last Edit: 29/07/2011 20:46:09 by Bored chemist »
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