The Moon is getting further away?

[welshlass]

I heard some scientist mention this on one of those Discovery programmes a while back, & i'm sure i heard it mentioned on telly recently. It was today's high winds & heavy rain (which we've been having forever by the feels of it) that got me thinking about this theory. If this is true; what connotations does have for the future of our planet and could this be a part of what's causing some of the freakish weather? I love science but i'm no big- brain so please respond to me as though you were explaining to a 10 yr old.

[enWTFp]

I'd be interested to read more if there is an article in Internet.

I always thought the Moon is in stable orbit around the Earth and even if something hits it (not too hard), as long as the masses of these two objects are not changed, after some time of fluctuations their trajectories should stabilize to the current state. (i.e. the current state is truly stable) Heck... they'll say tomorrow that we are leaving the Sun.

[Mozzes]

I heard some scientist mention this on one of those Discovery programmes a while back, & i'm sure i heard it mentioned on telly recently. It was today's high winds & heavy rain (which we've been having forever by the feels of it) that got me thinking about this theory. If this is true; what connotations does have for the future of our planet and could this be a part of what's causing some of the freakish weather? I love science but i'm no big- brain so please respond to me as though you were explaining to a 10 yr old.

The moon indeed seems to be moving away from the Earth (or is it the Earth moving away from the moon...:thinking: lol) at about a rate of 4cm per year. What this means for the weather nobody probably knows for certain. Another interesting tidbit of information is that Earth's rotation is slowing so that we're loosing something like 0.0002 seconds per day per year.

From what I've read tidal friction is causing both the slowing of Earth's rotation and the moon's retreat from Earth (decaying orbit?)

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[moon]

The moon always had a big impact on earth. In the past moon's distance from the earth was ~138000 km. Now is almost 3 times more distant. It's getting away. Don't know if that could have major aftermaths for us. I watched Discovery's program about moon. "Life on the earth couldn't be possible without moon presence." That was the main theme of the broadcast. It was long time ago and i don't quite remember what's main reasons of moon importance, but i remember that moon is natural earth's shield and in some way conduce natural balance to the earth.

[welshlass]

Thank you for those. I am, however, having difficulty understanding this tidal bulges on Earth making the Moon go further away theory?

[enWTFp]

Oh, thank you for the links and the explanations. This makes perfect sense actually. The idea is: The Earth is turning, but it is covered with oceans which follow its turning ONLY because of friction, hence reduce its speed (*). The rotation speed (the momentum) is connected with the gravitation force. The slower we move, the less "interested" is the Moon to "dance" with us, so she is leaving us slowly. If we "throw away" the oceans, we would turn faster and get the Moon closer. (and die, haha)

(*) to see it better: imagine you are spinning with very loose clothes on and with thick but tight clothes. You can stabilize your speed to higher values with thick tight clothes, whereas with loose clothes they will keep resisting your spinning, reducing your speed.


(ugh.. now I feel embarrassed, I knew this from before and really didn't think about it at all at first)

[welshlass]

Oh, thank you for the links and the explanations. This makes perfect sense actually. The idea is: The Earth is turning, but it is covered with oceans which follow its turning ONLY because of friction, hence reduce its speed (*). The rotation speed (the momentum) is connected with the gravitation force. The slower we move, the less "interested" is the Moon to "dance" with us, so she is leaving us slowly. If we "throw away" the oceans, we would turn faster and get the Moon closer. (and die, haha)

(*) to see it better: imagine you are spinning with very loose clothes on and with thick but tight clothes. You can stabilize your speed to higher values with thick tight clothes, whereas with loose clothes they will keep resisting your spinning, reducing your speed.


Aha thank you that makes perfect sense, now.

[Monte314]

I would explain it a little differently.

The spinning of the Earth is only indirectly related to the loss of angular momentum of the Moon. It is this loss which is causing the Moon to *very* slowly distance itself from Earth. This slowing and recession would occur even if the Earth were not rotating at all; this is not a centripetal effect.

You are correct, however, in mentioning tidal forces, and energy loss due to "friction".

As the Moon revolves, it's gravitational force does work on the Earth (tides, slight deformation/flexing of the Earth, tidal forces in the Earth's interior, etc., all of which eventually show up as environmental heat). The energy supply for this work is the Moon's only reservoir of readily available free energy: its rotational motion.

As this "frictional" work is done, the remaining energy of the Moon decreases (since energy is conserved), which slows the Moon ever so slightly in its orbit. As a result, the Moon's orbital speed drops, so it must move away from the Earth to remain in a stable orbit (since angular momentum is conserved).

The Moon's gravitational work on the Earth is like a "slow leak", gradually draining the Moon's orbital energy, causing it to slow and recede.

[Mozzes]

"slow leak"

That seems to be a pretty apt metaphor for the entire universe.

[Monte314]

That seems to be a pretty apt metaphor for the entire universe.

Apt indeed.

Here we have an excellent example of a large amount of kinetic energy being converted imperceptibly to useless heat with no "physical contact" involved... the "heat death" of the Earth/Moon pair being played out as we watch.

[redbaren]

Well we would not have any tides any more, navigation will be harder since there is no moon.