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johnm214


Registered: 05/31/07
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Re: so in theory in space....... [Re: Stonehenge]
#14836681 - 07/28/11 02:06 AM (12 years, 9 months ago) |
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Quote:
Stonehenge said:
Seuss, you are convinced too aren't you? How could you doubt all that sincerity?
Rather than making irrelevant appeals, it would be helpful if you could indicate what exactly you find incorrect and how you've reached that conclusion. I explained why I felt the way I do, and you've not taken issue with any of it except to pick at straw man arguments such as 'sincerity' and other nonsense nobody asserted was persuasive.
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DieCommie said: "Energy of rotation" does not resist change in orientation, angular momentum does. And the angular momentum does not change, only the axis of rotation with respect to the body. Its in the tumbling over end that the bullet is able to maintain its angular momentum in spite of losing energy.
I assume this tumbling would tend to be transverse to the linear momentum, right? Since the bullet's angular momentum is initially parrallel to its linear momentum, I would assume that it would tend to retain this, given there's no aerodynamic considerations to prevent this. I couldn't tell if you were suggesting something else or not.
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Stonehenge said: DC and john, i'm sorry you don't understand the physics of a gyroscope or how it affects the trajectory of a bullet. I provided a link but it seems to have been ignored. You can say "so what" as many times as you want but not only physicists but people in the field have proven what i said to be true.
If you have some source that is persuasive your going to have to make an argument and cite it with particularity to the relevant portion. I'm not going to attempt to search out your argument for you in some document when I don't believe you are correct in the first place, especially not if you can't explain yourself.
Edited by johnm214 (07/28/11 02:13 AM)
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Stonehenge
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Re: so in theory in space....... [Re: johnm214]
#14838424 - 07/28/11 11:53 AM (12 years, 9 months ago) |
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I remember now that i read about this years ago in regards to the earths tilt on it's axis. The axis wobbles over time and the change in the wobble was referred to as the precession of the equinoxes and would change a tiny bit over centuries.
The earth is a non rigid body, it's made up mostly of liquids in the form of melted rock and molten iron. It is flying through space, much like a bullet. The bullet has no liquids in it and would rapidly lose what little heat it had and have a temperature close to absolute zero. The earth is said to be about 8 billion years old. My question to all you out there is why hasn't the earth flipped and why isn't it tumbling end over end? It is still rotating about its axis with only a minor wobble. Perhaps in another 8 billion years it will or it might take a lot longer.
I grant you a bullet will eventually start tumbling but not in the time frame indicated. Anything that takes billions of years to be seen is what i call negligible.
OK, we are all learning some science here. Everyone has gone silent on the dark objects absorbing and giving off radiant energy faster than white. I take it silence equals assent?
-------------------- “A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.” (attributed to Alexis de Tocqueville political philosopher Circa 1835) Trade list http://www.shroomery.org/forums/showflat.php/Number/18047755
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DieCommie

Registered: 12/11/03
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Re: so in theory in space....... [Re: Stonehenge]
#14838557 - 07/28/11 12:17 PM (12 years, 9 months ago) |
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Quote:
My question to all you out there is why hasn't the earth flipped and why isn't it tumbling end over end?
If and when the rotation slows down, it will.
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Anything that takes billions of years to be seen is what i call negligible.
Life took billions of years to be seen. But I dont suspect it would take anywhere near that long. Would be a fun little calculation to do.
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Everyone has gone silent on the dark objects absorbing and giving off radiant energy faster than white. I take it silence equals assent?
Ha. I dont know what to tell you. You keep confusing the process of absorbing radiation with the process of emitting it as a black body. As long as you choose not to see the difference, you will remain confused.
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Stonehenge
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Re: so in theory in space....... [Re: DieCommie]
#14839971 - 07/28/11 04:53 PM (12 years, 9 months ago) |
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>Would be a fun little calculation to do.
Knock yourself out
>Ha. I dont know what to tell you.
Fair enough
We may have explored this thread as far as it's reasonable to go.
-------------------- “A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.” (attributed to Alexis de Tocqueville political philosopher Circa 1835) Trade list http://www.shroomery.org/forums/showflat.php/Number/18047755
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johnm214


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Re: so in theory in space....... [Re: Stonehenge]
#14840365 - 07/28/11 06:36 PM (12 years, 9 months ago) |
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Still waiting on what your point of disagreement was and why, or any evidence that your point of view is correct. Not much to talk about if you won't answer any questions or provide the basis for your claims.
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imachavel
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Re: so in theory in space....... [Re: Stonehenge]
#14841123 - 07/28/11 09:44 PM (12 years, 9 months ago) |
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Quote:
Stonehenge said: I remember now that i read about this years ago in regards to the earths tilt on it's axis. The axis wobbles over time and the change in the wobble was referred to as the precession of the equinoxes and would change a tiny bit over centuries.
The earth is a non rigid body, it's made up mostly of liquids in the form of melted rock and molten iron. It is flying through space, much like a bullet. The bullet has no liquids in it and would rapidly lose what little heat it had and have a temperature close to absolute zero. The earth is said to be about 8 billion years old. My question to all you out there is why hasn't the earth flipped and why isn't it tumbling end over end? It is still rotating about its axis with only a minor wobble. Perhaps in another 8 billion years it will or it might take a lot longer.
I grant you a bullet will eventually start tumbling but not in the time frame indicated. Anything that takes billions of years to be seen is what i call negligible.
OK, we are all learning some science here. Everyone has gone silent on the dark objects absorbing and giving off radiant energy faster than white. I take it silence equals assent?
because it's perfectly balanced in precise orbit. to answer something for you, you are thinking a bullet that falls into a planets gravity or orbit won't tumble. sure it will. we are argueing that if the bullet flies through space infinitely that it will or won't tumble. I say it won't, it will follow the same path and in such as the same way that it left the gun. ever play asteroids? an object in motion tends to stay in motion, an object at rest tends to stay at rest. what would cause the bullet to change it's characteristics and tumble? air friction? doesn't exist in space? maybe tiny molecular particles broken off from the asteroid belt flowing around could. but really nothing else could. idk w/e
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I did not say to edit my signature soulidarity! Now forever I will never remember what I said about understanding the secrets of the universe by paying attention to subtleties!
I'm never giving you the password again. Jerk
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Seuss
Error: divide byzero



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Re: so in theory in space....... [Re: imachavel]
#14842420 - 07/29/11 04:16 AM (12 years, 9 months ago) |
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> My question to all you out there is why hasn't the earth flipped and why isn't it tumbling end over end?
The moon.
-------------------- Just another spore in the wind.
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Stonehenge
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Re: so in theory in space....... [Re: Seuss]
#14843053 - 07/29/11 09:51 AM (12 years, 9 months ago) |
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Imach, your answer flies in the face of the polhode theory which has been proven on the basis of the earth's wobble about it's axis as well as experimentally. Seuss, you haven't explained how the moon would do this.
The path of the bullet would depend on whether it escaped the gravity of the solar system as well as the gravity of planets in the system. It might go into orbit around the sun, around a planet or large asteroid. It might hit some solid object and shatter. Or, it could fly out into outer space and be pushed with a tiny acceleration by light pressure. Any pelhode wobble in it's spin would take possibly billions of years to show up. By then it may have made it to another solar system. Some poor alien might be walking along and whammo! gets hit by a chunk of lead. "where the @xF%! did that come from?"
-------------------- “A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.” (attributed to Alexis de Tocqueville political philosopher Circa 1835) Trade list http://www.shroomery.org/forums/showflat.php/Number/18047755
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Seuss
Error: divide byzero



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Re: so in theory in space....... [Re: Stonehenge]
#14843110 - 07/29/11 10:14 AM (12 years, 9 months ago) |
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Nature:
Quote:
Stabilization of the Earth's obliquity by the Moon
J. Laskar, F. Joutel & P. Robutel
Astronomie et Systèmes Dynamiques, Bureau des Longitudes, 77 Avenue Denfert-Rochereau, F75014 Paris, France
ACCORDING to Milankovitch theory1,2, the ice ages are related to variations of insolation in northern latitudes resulting from changes in the Earth's orbital and orientation parameters (precession, eccentricity and obliquity). Here we investigate the stability of the Earth's orientation for all possible values of the initial obliquity, by integrating the equations of precession of the Earth. We find a large chaotic zone which extends from 60° to 90° in obliquity. In its present state, the Earth avoids this chaotic zone and its obliquity is essentially stable, exhibiting only small variations of plusminus 1.3° around the mean value of 23.3°. But if the Moon were not present, the torque exerted on the Earth would be smaller, and the chaotic zone would then extend from nearly 0° up to about 85°. Thus, had the planet not acquired the Moon, large variations in obliquity resulting from its chaotic behaviour might have driven dramatic changes in climate. In this sense one might consider the Moon to act as a potential climate regulator for the Earth.
(Obliquity is the axial tilt.)
NASA:
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The Moon is more than a pretty accessory in our night sky. It stabilizes Earth's wobble, which led to a more stable climate and probably helped life evolve. The Moon also guides the ebb and flow of Earth's oceans.
NASA:
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Does the Moon stabilize Earth in its rotation?
Well, I'm no expert on motions of the Earth, but the Moon does add drag to the Earth's rotation in the form of tides, both oceanic and internal. This added drag tends to stabilize the rotation. It is also gradually slowing down the rotation of the Earth, which gradually lengthens Earth days.
Dr. Eric Christian and Beth Barbier
-------------------- Just another spore in the wind.
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Stonehenge
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Re: so in theory in space....... [Re: Seuss]
#14843162 - 07/29/11 10:42 AM (12 years, 9 months ago) |
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Seuss, that's interesting. But they couch it in terms of "may" stabilize the earth's tilt and climate variations. However, in the explanation of polhode wobble, they say that internal or external changes in torque drive the polhode effect. For example, movements of internal liquid can cause a loss of spin which would give more wobble. The moon exerting a drag would seem to be an external force which would drive it further. We seem to have competing theories here. Why would an external drag not add to the polhode effect? All i see above is the statement that it stabilizes but no hard facts to back it up. Sounds like speculation.
I quote from the source dc gave:
>The longest axis of symmetry (i.e. the axis through the center the wood block, from top to bottom) corresponds to the smallest or minimum moment of inertia. Rotation about this axis is also stable, but given enough time, such as a body rotating in zero g, any perturbations due to energy dissipation or torques would cause the polhode path to expand, in larger and larger ellipses or circles, and eventually migrate through the separatrix and its axis of intermediate inertia to its axis of maximum inertia.
-------------------- “A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.” (attributed to Alexis de Tocqueville political philosopher Circa 1835) Trade list http://www.shroomery.org/forums/showflat.php/Number/18047755
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DieCommie

Registered: 12/11/03
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Re: so in theory in space....... [Re: Stonehenge]
#14843192 - 07/29/11 10:50 AM (12 years, 9 months ago) |
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So which axis for an oblate spheroid corresponds to the smallest moment of inertia? Are you sure you are considering the right axis? Think about it for a bit. This might help, http://en.wikipedia.org/wiki/Ellipsoid
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HeavyToilet
The Heaviest OfThem All


Registered: 08/06/03
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Re: so in theory in space....... [Re: DieCommie]
#14866677 - 08/03/11 10:47 AM (12 years, 9 months ago) |
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I know this isn't quite on topic, but as it's related, I thought I would ask.
As there's no convection in space, and therefor cooling is very slow, how would it feel to put... say your hand into space? I guess after a number of seconds you would get 'the bends' in your hand, and that would cause some type of feeling associated with that effect, but how would the temperature feel on your hand?
I guess the thing that makes me wonder this, is all the time on Earth, we're having molecules hitting our skin (from clothing, air, water, etc), so I wonder if it would be a noticeable difference if someone placed their hand in space, and no molecules were hitting their hand.
Thoughts, anyone?
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ChuangTzu
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Re: so in theory in space....... [Re: HeavyToilet]
#14866856 - 08/03/11 11:41 AM (12 years, 9 months ago) |
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Quote:
HeavyToilet said: I know this isn't quite on topic, but as it's related, I thought I would ask.
As there's no convection in space, and therefor cooling is very slow, how would it feel to put... say your hand into space? I guess after a number of seconds you would get 'the bends' in your hand, and that would cause some type of feeling associated with that effect, but how would the temperature feel on your hand?
I guess the thing that makes me wonder this, is all the time on Earth, we're having molecules hitting our skin (from clothing, air, water, etc), so I wonder if it would be a noticeable difference if someone placed their hand in space, and no molecules were hitting their hand.
Thoughts, anyone?
It would feel like when you put your hand over the end of a vacuum cleaner except that pink circle that you get on your hand after doing that would cover your whole hand. Whatever you had sealing the rest of your arm off from the vacuum would get really tight when your hand swelled and it would cut off circulation to your hand. It would be very painful and I doubt you'd notice the temperature effects.
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HeavyToilet
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Re: so in theory in space....... [Re: ChuangTzu]
#14866884 - 08/03/11 11:48 AM (12 years, 9 months ago) |
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I'm thinking about more of an idealized situation. Like if there was such a way that you could have some kind of seal that would have your hand in outer space, but the rest of your body inside, and the seal wasn't strong enough to cut off circulation, but would prevent the oxygen and whatnot from rushing out.
I know such a thing would probably be impossible to set up, but I'm just wondering exclusively about the temperature, or lack of feeling of molecules constantly bumping into the skin, rather than considering all the issues with setting up such a situation.
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Stonehenge
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Re: so in theory in space....... [Re: ChuangTzu]
#14866886 - 08/03/11 11:48 AM (12 years, 9 months ago) |
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The water in your blood in the hand would tend to boil in the zero pressure of space. Unless it had sun shining on it it would get cold really fast. If it did have sun shining on it you would pick up a nasty burn in short order. Now picture yourself trying to get your hand back out and it's stuck. If you did pull it out the air in the cabin would fly out the hole unless it was quickly plugged.
-------------------- “A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.” (attributed to Alexis de Tocqueville political philosopher Circa 1835) Trade list http://www.shroomery.org/forums/showflat.php/Number/18047755
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ChuangTzu
starvingphysicist



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Re: so in theory in space....... [Re: HeavyToilet]
#14866892 - 08/03/11 11:51 AM (12 years, 9 months ago) |
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Quote:
HeavyToilet said: I know such a thing would probably be impossible to set up, but I'm just wondering exclusively about the temperature, or lack of feeling of molecules constantly bumping into the skin, rather than considering all the issues with setting up such a situation.
The lack of molecules bumping into the skin is exactly the feeling of your hand swelling up like a balloon that I described.
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johnm214


Registered: 05/31/07
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Re: so in theory in space....... [Re: Stonehenge]
#14870659 - 08/04/11 03:42 AM (12 years, 9 months ago) |
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Quote:
HeavyToilet said: I'm thinking about more of an idealized situation. Like if there was such a way that you could have some kind of seal that would have your hand in outer space, but the rest of your body inside, and the seal wasn't strong enough to cut off circulation, but would prevent the oxygen and whatnot from rushing out.
I know such a thing would probably be impossible to set up, but I'm just wondering exclusively about the temperature, or lack of feeling of molecules constantly bumping into the skin, rather than considering all the issues with setting up such a situation.
Ignoring the pressure change and all that entails, I would imagine you wouldn't feel much of anything, as if you were in room temperature, followed by a very gradual decrease in temperature due to radiative heat loss (your skin putting off more radiative energy than it takes in per period of time and thus the temperature decreasing). Of course, your blood stream would almost certainly provide many orders of magnitude more heat to the tissue than is lossed in radiative heat loss, so perhaps nothing at all.
Quote:
Stonehenge said: The water in your blood in the hand would tend to boil in the zero pressure of space.
Naw, that's just an old myth. Your blood isn't in the zero pressure of space, its in your blood vessels which are in your hand. If your blood vessels and tissueshave the integrity to maintain their shape and function during normal activities, they certainly have the integrity to resist to some degree the huge loss of pressure which would be required to bring the water in the mixture to the boiling point. Add in the other tissues which the vessels are imbedded into, and its obvious there's no way the pressure in your hand is going to drop to below boiling pressure for water at physiological temp, much less whatever temp is required to boil the mixture that is blood.
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Seuss
Error: divide byzero



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Re: so in theory in space....... [Re: johnm214]
#14870768 - 08/04/11 05:00 AM (12 years, 9 months ago) |
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>> The water in your blood in the hand would tend to boil in the zero pressure of space. > Naw, that's just an old myth.
You are both correct... This has been well documented by NASA and the Soviet Union through various accidents where people were exposed to a hard vacuum (and most lived to tell the tale). See http://www.damninteresting.com/outer-space-exposure/ for more details.
-------------------- Just another spore in the wind.
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johnm214


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Re: so in theory in space....... [Re: Seuss]
#14870830 - 08/04/11 05:36 AM (12 years, 9 months ago) |
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Hmm, are you suggesting there's some merit to the claim that the blood would tend to boil in a hand exposed to space?
That's an interesting article (wasn't aware there were real-world examples of this occurring) but I didn't see any mention of boiling blood inside the body. The closest was mention of pressure's effect on solubility of gasses, but that's not boiling (the gasses are already far past their boiling temperature at both terrestrial and space conditions, obviously).
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Seuss
Error: divide byzero



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Re: so in theory in space....... [Re: johnm214]
#14870845 - 08/04/11 05:48 AM (12 years, 9 months ago) |
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> Hmm, are you suggesting there's some merit to the claim that the blood would tend to boil in a hand exposed to space?
Yes, a tiny bit of merit (though I was thinking of an entire body exposed, not just a hand). Length of exposure and a beating heart would be large mitigating factors. A few seconds of exposure (to a hard vacuum) of a hand attached to a living body isn't going to cause blood to boil.
I could be wrong... 
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