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View Full Version : 100 kilogram probe threatens Earth-Moon Balance!



Rodina
2002-Sep-18, 08:42 AM
Instapundit (www.instapundit.com) points on this very, very strange thing at Democrats.Com..


(EDITORIAL COMMENT: For present purposes (lest this digress into a political squabble), I'll profess agnosticism about everything about the Bush Administration. Say what you will about his position on international law, I just can't bring myself to believe that his failure to stop the TransOrbital private moon mission is a dangerous neglect of his duties because..

(Hold on to what's left of your brain cells)

Like all the other international laws, Bush is now ignoring those pertaining to space. As America is distracted by 9/11 remembrances and warnings of new threats, His Heinous has turned the moon over to a private, for-profit corporation called TransOrbital that has a far-reaching, frigthening agenda for the corporate domination of space. All TransOrbital had to do was promise not to contaminate and pollute the moon - yeah, right. That's what the oil companies say about ANWR. There was no Congressional vote - not even any consultation. Bush simply acted as if the moon were his to give away. The TransOrbital venture could be disastrous for the globe - no scientist today could predict yet >>>HOW ADDING MASS TO THE MOON VIA HUMAN INFRASTRUCTURE OR REMOVING MASS, VIA MNING, WILL IMPACT THE DELICATE GRAVITATIONAL INTERPLAY BETWEEN EARTH AND ITS ONLY SATELLITE<<<. The moon belongs to all the people of the Earth - not to George. W. Bush or his friends at TransOrbital.


(Emphasis added by Instapundit, not in original Democrats.com piece).


<font size=-1>[ This Message was edited by: Rodina on 2002-09-18 04:44 ]</font>

Wally
2002-Sep-18, 11:04 AM
Sweet. . . No leftist leanings in THAT report, is there!!! Heaven forbit a free enterprise attempt to do something for profit. Everyone knows only the government knows what's best for mankind. (sniff, sniff. . . yep, smells like sarcasm!).

Seriously, I would assume anyone attempting to build on the moon would most likely find a method to use the Moon's resources to do so. That would sure be a lot more economical (and therefore, profitable. . .EGAD!!!) than hauling everything up from Earth! Besides, shifting mass from Earth to the moon would merely shift the orbit point (currently inside of Earth) an extremely tiny tiny amount, wouldn't it?

Mainframes
2002-Sep-18, 11:22 AM
I think to alter the relative orbits of the earth-moon system you would probably have to transport a significant percentage of the earths crust to the moon and even then the effects would be minimal....

Conrad
2002-Sep-18, 02:59 PM
I'll have some of whatever they've been smoking, thanks!

This subject has been addressed on another thread, rather more seriously, but I can't remember which one.

Russ
2002-Sep-18, 07:53 PM
On 2002-09-18 04:42, Rodina wrote:
(snip)
The TransOrbital venture could be disastrous for the globe - no scientist today could predict yet >>>HOW ADDING MASS TO THE MOON VIA HUMAN INFRASTRUCTURE OR REMOVING MASS, VIA MNING, WILL IMPACT THE DELICATE GRAVITATIONAL INTERPLAY BETWEEN EARTH AND ITS ONLY SATELLITE<<<. (snip)
<font size=-1>[ This Message was edited by: Rodina on 2002-09-18 04:44 ]</font>


I think if you do a little research, you will find that the grandest of human endevours on the Moon would would constitute such a sub-atomically small percentage of the Earth_Moon mass as to be TOTALLY insignificant. Mind you, I may be over stating our potential impact by several orders of magnitude. /phpBB/images/smiles/icon_smile.gif /phpBB/images/smiles/icon_biggrin.gif /phpBB/images/smiles/icon_lol.gif

moving_target
2002-Sep-19, 05:22 AM
oh.. what's an order of magnitude between friends /phpBB/images/smiles/icon_wink.gif /phpBB/images/smiles/icon_smile.gif

Bad Engineer
2002-Sep-19, 04:34 PM
If you scroll further down the Instapundit page, you'll see some of the comments on these folks' mathematically-challenged mindset:


The Moon's mass is .07 x 1024 kg. The Earth is approximately 81 times more massive. By contrast, TransOrbital is talking about payloads in the hundreds (102) of kilograms at most. Can these people do math? Do they have any idea what they're talking about?

One comment that caught my attention was this one:


If I recall correctly, the strongest gravitational influence on the moon is not the earth, it's the sun. The earth and the moon share more or less the same orbit around the sun, passing each other as they go.

I'm not sure if I understand what is meant by this - does this imply that the moon is not really 'orbiting' around the Earth? I'm a bit confused now

B.E.

Kaptain K
2002-Sep-19, 04:58 PM
I'm not sure if I understand what is meant by this - does this imply that the moon is not really 'orbiting' around the Earth? I'm a bit confused now.
It depends on your frame of reference. From a geocentric POV, the Moon definitely orbits the Earth. The Moon's orbit around the sun is, at all times, concave to the Sun. The Sun has a greater gravitational effect on the Earth and Moon than either does on the other.

Hope I didn't confuse the issue even more.

mallen
2002-Sep-20, 02:48 AM
On 2002-09-19 12:58, Kaptain K wrote:
The Moon's orbit around the sun is, at all times, concave to the Sun. The Sun has a greater gravitational effect on the Earth and Moon than either does on the other.

Hope I didn't confuse the issue even more.



You're logic escapes me. The Moon's orbit is at all times also concave to the Earth as well, so what does that mean?

Anyway, your conclusion is correct, even if your reasoning is kinda off:

Sun mass = 1.989e+30 kg
Earth mass = 5.972e24 kg
Sun distance to moon = 1.496e+08 km
Earth distance to moon = 3.844e+05 km

So, if we calculate from these numbers, the ratio of gravity felt from the Sun and Earth, we find that:

<pre>
Gs 1.989e+30 / (1.496e+08)^2
-- = ------------------------- = 2.199
Ge 5.972e+24 / (3.844e+05)^2
</pre>

Or, the Sun pulls on the moon about twice as hard as the Earth.

<font size=-1>[ This Message was edited by: mallen on 2002-09-19 22:49 ]</font>

xriso
2002-Sep-20, 03:59 AM
On 2002-09-19 12:34, Bad Engineer wrote:


If I recall correctly, the strongest gravitational influence on the moon is not the earth, it's the sun. The earth and the moon share more or less the same orbit around the sun, passing each other as they go.

I'm not sure if I understand what is meant by this - does this imply that the moon is not really 'orbiting' around the Earth? I'm a bit confused now


The sun accelerates the Earth and the Moon about equally, so they essentially move with each-other. Now, Earth also has a strong pull on the Moon, so the Moon whizzes around Earth while Earth flies around the sun.

It's kind of like travelling in a train on a big circular track while swinging an object around you. If you manage to revolve it only a few times per lap, and you're far enough away from the center, then the object and you are basically sharing the same track, but sometimes it's in front, and sometimes you're in front.


<font size=-1>[ This Message was edited by: xriso on 2002-09-20 00:01 ]</font>

Cloudy
2002-Sep-22, 07:07 AM
In effect, no one object orbit arround another.

In a system of two objects, both objects will orbit arround a common, single point.
The central point will be closer to the object with the most mass, in this case, Earth. The more the difference in mass, the closer to the more massive object the central point will be.

In the Earth-moon system, the central point is pretty close to earth's core. So, to all appearances, the moon will orbit the Earth. Yet the earth will appear to "wobble" a bit because it orbits a point close to its core.

This is one method of detecting extra-solar planets. The star wobbles a tiny bit because it and the planet are both orbiting a point close to the star's center of mass.

This effect is very visible in systems like Pluto-Charon where there is not nearly as much difference in mass. It is easy to see that Pluto and Charon both orbit the same point - albeit a point that is closer to Pluto than Charon.

If you consider Earth and a 100Kg satelite, the central point will be so close to Earth's center of mass that the Earth's motion due to the satelite will not be measurable.

Hope this helps.

Doodler
2002-Sep-25, 09:44 PM
I do not believe any math is needed to verify that the original post on their site is the result of an overactive imagination paranoid about the prospects of corporate moon exploration. For Pete's sake, the Apollo astronauts took several thousand pounds of equipment with them, including booster segments deliberately plowed into the moon, and brought back ton(s) (i do not remember the precise amount) of dirt and rock with them. Aside from some forehead slapping and laughter on our part, I don't think we need to put much gray matter on the line for this loon. /phpBB/images/smiles/icon_smile.gif

_________________
Never discount a possibility, always charge full price - HB Marketing Philosophy

<font size=-1>[ This Message was edited by: Doodler on 2002-09-25 17:45 ]</font>

Rich
2002-Sep-26, 02:44 PM
My God, I'm just happy HBers havev't latched onto this yet. By this logic the transfer of mass during the Apollo missions would have been nearly catastrophic... no catastrophy is evidence of no moon landings...

Singing tune of "If I Were a Rich Man":

If I were a nut-job... la-la-la la-la-la... dee-dee dee-dee-dum