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Dave W.
Info Junkie
USA
26022 Posts |
 Posted - 05/26/2004 : 10:20:12 [Permalink]
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| Hey, verlch: why not read about how the Moon hasn't always been receeding at 3.82 cm per year before you spend time clarifying your mistakes into clearer astronomical nonsense? |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 05/28/2004 : 07:46:17 [Permalink]
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quote:
Originally posted by Dave W.
Hey, verlch: why not read about how the Moon hasn't always been receeding at 3.82 cm per year before you spend time clarifying your mistakes into clearer astronomical nonsense?
I could theorise as to WHY the rate was less in the distant past. Without consulting web pages first. But I don't see the point, since I would have to rely on scientific theories. And we all know what Verlch thinks about science. Besides, though Verlch is highly intelligent, I'm not sure he has the mathematical background needed to understand. |
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"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 05/28/2004 : 13:23:04 [Permalink]
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Having gotten some beer and calmed down, I'm in a better mood than before, so I think I'll have a stab at explaining why the moon's orbital radius was increasing with less than 3cm in the distant pass.
First I will have to touch on the subject of gravitational force, for several reasons.
Let me first remind you that the theory of gravitation is just a theory. Creationists and Fundies(tm) demanding Absolute Truth will probably not accept the Theory of Gravitation, because it's not written in the Bible. However, the majority of the experiments conducted in this field has shown that Newton's Law of Gravity works for the majority of situations one might encounter.
In mathematical terms, the force attracting two bodies of mass is proportional to the mass of each object, and inverse proportional to the square of the distance.
F=k*m1*m2/d²
m1 and m2 are the mass of the respective bodies,
d is the distance between the objects,
F is the force pulling them together, and finally
k is the gravitational constant.
This formula is the foundation to a sub-category of physics science called "orbital mechanics". Together with some other formulae, (like the one about acceleration, F=m*a, centrifugal force, F=m*v²/r or F=4(pi)²*m*r/T², Potential and kinetic energies W=m*g*h and W=m*v²/2 ) you can bake together some pretty amazing conclusions.
All this meddling in math, and formulae are boring for people with short attention-span, so here's the short version:
* The moon needs energy added in order to move away from Earth. (Science-geeks refer to this as 'negotiate the gravitational well')
* The tidal effect on Earth adds a fairly constant level of energy to the moon each year.
* The gravitational pull between the Earth and the moon decreases with the square of the added distance. Which means that you can add more distance for the same amount of energy the farther out the moon is.
* Using the same calculations, you can also tell that in the past when the moon was closer, it took more energy to add the same distance as now. Which means that during a year "back then" it got less distance for the same push.
Conclusion: half a billion years ago (when Verlch thought that the distance to the moon should have been half of what it is now) the moon didn't increase it's orbital radius with 3,8cm/year. The rate was much less.
(Edited to adjust some stuff) |
Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
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| Edited by - Dr. Mabuse on 05/28/2004 13:30:39 |
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Dave W.
Info Junkie
USA
26022 Posts |
Posted - 05/28/2004 : 21:30:13 [Permalink]
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| Mab, the Talk.origins article I linked to earlier in this thread also talked about there being differences in tidal dynamics due to there being a different configuration of the continents way back when. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
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thecor
New Member
Italy
27 Posts |
Posted - 05/28/2004 : 21:35:23 [Permalink]
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Dr. Mabuse,
Thank you for the information. This is more in line with why I am here-to learn, (talking to intelligent people directly is much more rewarding in the sense of information gardening, than all the reading I could do in the few years I have left).
I do have a question tho. In regard to: "The tidal effect on Earth adds a fairly constant level of energy to the moon each year." Could you explain how what I would expect as a 'drag' effect is a mechanism for adding energy to the moon? Thank you
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 05/29/2004 : 05:04:15 [Permalink]
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quote:
Originally posted by Dave W.
Mab, the Talk.origins article I linked to earlier in this thread also talked about there being differences in tidal dynamics due to there being a different configuration of the continents way back when.
That would affect the energy transfer to the moon. To what extent though, I'm not sure...
Another thing that I haven't mentioned is that with the moon closer to earth, the orbital period will be less, which would mean that rotational difference between earth and moon will be smaller. The friction will be less, which in turn would decrease the energy transfer.
The moon is slowly spinning away from us in an accelerating spiral. |
Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3
"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 05/29/2004 : 05:28:44 [Permalink]
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quote:
Originally posted by thecor
Dr. Mabuse,
I do have a question tho. In regard to: "The tidal effect on Earth adds a fairly constant level of energy to the moon each year." Could you explain how what I would expect as a 'drag' effect is a mechanism for adding energy to the moon? Thank you
The tidal effect gathers lots of water (make the ocean rise) toward the moon. If the Earth hadn't rotated, the center of the mass of the water would align itself in a straight line between earth's center of mass, and the moon's center of mass.
But because the earth is rotating, it is twisting away the gathered water from that straight line between Earth and the moon. This introduces a third center of mass (the tidal water's mass) that is offset from Earth's center of mass, and it is this that constantly tugs at the moon.
The aparent distance offset of the tidal water's mass due to friction depends on the rotational difference between the moon and Earth.
Today, if you use the moon instead of the sun to define a day, one day would be roughly 24+(~1) = 25 hours. If the distance to the moon was only half of what it is, then the orbital period would be one fourth. One day would be 24+(~4) = 28 hours.
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Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3
"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse
Support American Troops in Iraq:
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thecor
New Member
Italy
27 Posts |
Posted - 05/29/2004 : 10:26:09 [Permalink]
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quote:
The tidal effect gathers lots of water (make the ocean rise) toward the moon. If the Earth hadn't rotated, the center of the mass of the water would align itself in a straight line between earth's center of mass, and the moon's center of mass.
But because the earth is rotating, it is twisting away the gathered water from that straight line between Earth and the moon. This introduces a third center of mass (the tidal water's mass) that is offset from Earth's center of mass, and it is this that constantly tugs at the moon.
This "tug" at the moon is what I meant by drag. Wouldn't that cause the moon to move closer to the earth and not away form it? |
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 05/29/2004 : 15:12:02 [Permalink]
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quote:
Originally posted by thecor
This "tug" at the moon is what I meant by drag. Wouldn't that cause the moon to move closer to the earth and not away form it?
No... because the mass of the water is part of the mass of the Earth. What happens is that some of the mass gets displaced. This displacement cause the center of gravity to move in a circle around the average center of the system.
Actually, the link that Dave_W provided is very good.
http://www.talkorigins.org/faqs/moonrec.html
Scroll down to the third picture, and you'll see what I've been talking about.
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Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3
"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse
Support American Troops in Iraq:
Send them unarmed civilians for target practice..
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thecor
New Member
Italy
27 Posts |
Posted - 05/29/2004 : 23:18:56 [Permalink]
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Dr. Mabuse,
Now that I know about the torque process, I can understand the added energy imparted to the moon- what an awesome and complex process the whole earth/moon system is. As the article stated,"Although it may seem to the casual reader that the Earth-moon system is fairly simple (after all, it's just Earth and the moon), this is only an illusion." And I am guilty as charged!
Thank both you and Dave for the information. |
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ljbrs
SFN Regular
USA
842 Posts |
Posted - 06/12/2004 : 16:22:16 [Permalink]
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According to the prevailing theory, a planet approximately the size of Mars (but not Mars) collided with Earth and threw out material into an accretion disk around Earth which thrown-out material eventually became the Moon.
There is a nice book, "The Big Splat" by Dana Mackenzie which explains this theory and goes through the ideas previously considered about the formation of the Moon. When the astronauts gathered material and rocks from the Moon (Apollo Program), these rocks showed this connection. Evidently the planet which collided with Earth had an iron core and was engulfed by Earth in the collision, throwing out mantle material which became the Moon.
The material collected during the Apollo program shows such a probable scenario.
I would suggest that anybody interested in this fascinating theory should read "The Big Splat". The price (at Borders Books and Music) was $24.95. It should be offered on the Internet somewhere.
Dr. Mabuse explains it earlier in this thread (with some great sketches).
ljbrs |
"Innumerable suns exist; innumerable earths revolve about these suns in a manner similar to the way the seven planets revolve around our sun. Living beings inhabit these worlds."
Giordano Bruno
(Burned at the stake by the Roman Catholic Church Inquisition in 1600) |
| Edited by - ljbrs on 06/12/2004 16:44:52 |
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ljbrs
SFN Regular
USA
842 Posts |
Posted - 06/12/2004 : 18:46:57 [Permalink]
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Folks:
I bought "The Big Splat, or How Our Moon Came to Be," by Dana Mackenzie, after reading a review: "The Genesis of Earth's Natural Satellite" in the May issue of PHYSICS TODAY, one of my favorite magazines (really, my very FAVORITE). I began to write about it, but could not find the review after looking through my most recent copies of PHYSICS TODAY for the book report about it. I had forgotten (until a few minutes ago) that I had torn out the review and slipped it into my copy of "The Big Splat...." The book review gives a very thorough account of all of the theories about the Moon, going way back to ancient times. I strongly recommend it. It also mentions that the Moon rocks brought back by the Apollo Astronauts gave firm support to the fact that the Astronauts did go to the Moon and puts the imbecillic critics of the Moon program "up a creek without a paddle" (as the saying goes). If anybody is seriously interested in the full story, this is the book to buy. It comes highly recommended by PHYSICS TODAY (and it was very, very difficult for me to put the book down). The book keeps you in suspense. However, our whole discussion here somewhat spoils it for us, because Dana Mackenzie did not let on what the final theory would be until nearly the end of the book.
ljbrs |
"Innumerable suns exist; innumerable earths revolve about these suns in a manner similar to the way the seven planets revolve around our sun. Living beings inhabit these worlds."
Giordano Bruno
(Burned at the stake by the Roman Catholic Church Inquisition in 1600) |
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ljbrs
SFN Regular
USA
842 Posts |
Posted - 06/13/2004 : 17:24:33 [Permalink]
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I almost forgot. In addition, there is an excellent article in the April 2004 issue of Physics Today entitled "Origin of Terrestrial Planets and the Earth-Moon System," by Robin M. Canup. Physics Today should be in some libraries. Without a question, it ought to be in university libraries.
ljbrs |
"Innumerable suns exist; innumerable earths revolve about these suns in a manner similar to the way the seven planets revolve around our sun. Living beings inhabit these worlds."
Giordano Bruno
(Burned at the stake by the Roman Catholic Church Inquisition in 1600) |
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