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Q: Grafity, how does it work. ( Answered,   3 Comments )
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 Subject: Grafity, how does it work. Category: Science > Physics Asked by: utrechtsedomtoren-ga List Price: \$10.00 Posted: 30 Nov 2006 04:45 PST Expires: 30 Dec 2006 04:45 PST Question ID: 786955
 ```How can mass see eachother, f.e. how does the moon 'know' that it has less mass then the earth, so it turns around the earth instead of the earth turns around the moon.```
 Subject: Re: Grafity, how does it work. Answered By: justaskscott-ga on 18 Dec 2006 01:52 PST
 ```Hi utrechtsedomtoren, Ian G.'s comment is a good starting point for this answer. As Courtney Seligman, an astronomy professor, observes: "The Earth and Moon are each moving around the center of mass of the Earth-Moon system. Since the Earth is much more massive, it is much closer to the center of mass, which is actually inside the Earth." Prof. Seligman notes that the Earth and the Moon ""each exert[] a force on the other which, according to Newton's Third Law of Motion (the Law of Action and Reaction), is equal and opposite to the force that the other is exerting on it." However, "although the forces are equal, their effects are not, because the more massive Earth is accelerated less by the same force, than the less massive Moon." "Gravitational Interactions of the Earth and Moon" Personal website of Courtney Seligman, Author / Professor of Astronomy http://cseligman.com/text/moons/earthmoongravity.htm For further explanations of the Earth-Moon system, see: "Question #1526" (answered by Louis A. Bloomfield) How Things Work http://howthingswork.virginia.edu/page1.php?QNum=1526 "The Moon's Motion," by Dr. Jamie Love Merlin Science http://www.synapses.co.uk/astro/moon1.html In short, the more massive Earth does not move as much around the barycenter as the less massive Moon. As your question indicates, an orbit is a result of gravity. Gravity is a complex phenomenon, still being studied. However, for purposes of this answer, I think that it suffices to say that a massive object warps space-time, causing other objects to move towards it (rather than, say, continue in a straight line). "Gravity" (27 Dec 1997) The Why Files http://whyfiles.org/052einstein/frame_drag4.html As explained by Dr. Jamie Love in the document cited earlier, the Moon, in orbiting the Earth, is essentially moving toward the Earth but never hitting it. (And likewise, the Earth is moving toward the Moon and never hitting it -- though its movement is not as great, since, as noted before, it is much more massive.) For more information about gravity (and related subjects), see: "Special & General Relativity Questions and Answers," by Dr. Sten Odenwald Gravity Probe B http://einstein.stanford.edu/content/relativity/qanda.html Please let me know if you need any clarification of this answer. - justaskscott Search strategy -- Searched on Google for: "earth orbit the moon" "earth orbits the moon" earth moon barycentre earth moon barycenter gravity gravitation```
 ```Brad Gasrret quipped in his routine from pre-Star Search, "The woman I'm dating is Swedish, six feet two inches. Her name is Inertia. Large lady."```
 ```You want to post this in religion - the concept of assigning thought and feelings to inanimate objects might be best addressed by a Shinto or someone who thinks in terms of dryads or other spirits of plants or mountains or something, perhaps a druid would be a good source of an answer. Although he was a christian philosopher, C.S. Lewis assigned god-like attributes to the planets, perhaps a reading of his "adult" books (not Narnia) would be a help.```
 ```Rather than thinking of the Earth and the Moon as two separate bodies, think of them as a system - they're working together. The Earth and the Moon attract each other, but the Earth's more massive so it pulls harder. It's not quite true to say the Moon orbits the Earth - the Moon and Earth both orbit their centre of mass, called the barycentre. It happens that the barycentre is within the Earth, but the Earth wobbles as the Earth / Moon system revolves. Ian G.```