Origin of the Moon

kujosHeist · 16-03-2009 4:19pm #1

read the rewiew of an interestin book there lately with the same title as this thread which speculates on the origin of the moon, some of the facts given quite strange, like the distant between the moon and earth is 1/400 of the distant between earth and the sun, and also the moon is 1/400 the diametre of the sun or somthing like that.
also its quite a large moon for a relativlely small planet, and given that life on earth had far of a less chance of existing with out the old lunar sheild it makes ya wonder was there ever any intervention in the past

Biro · 16-03-2009 5:31pm

The size and relative distance between Earth/Moon and Earth/Sun is a funny co-incidence alright. But it's size relative to the Earth isn't as impressive as Pluto's moon!
Speaking of Pluto, I wonder did any scientist investigate the possibility that it was the culprit who hit Uranus, which knocked that planet effectively on it's side, and itself possibly splitting in two and going skew-ways with it's orbit?

Flukey · 16-03-2009 5:45pm

The size and distance fact is also why the moon almost perfectly covers the sun during a solar eclipse.

Saruman · 16-03-2009 5:49pm

The moon was thought to have been the result of a massive mars size object hitting the earth Billions of years ago and the resulting debris formed the moon.

Glico Man · 16-03-2009 5:55pm

I have a question..

Why are all planets and moons spherical? why are there no cube shaped planets or moons??

seamus · 16-03-2009 5:59pm

aaronh007 wrote: »

I have a question..

Why are all planets and moons spherical? why are there no cube shaped planets or moons??

For the same reason why the vortex in water going down a plughole is circular and not square or triangular.

OK, it's conical, but at its entrance it's circular.

kujosHeist · 16-03-2009 6:02pm

a sphere is the most effient shape, like a soap bubble (thank you kevin spacey!) it wouldnt be able to support itself if it were any other shape

seamus · 16-03-2009 6:06pm

Actually I imagine it's nothing to do with efficiency and more to do with the gravitational effect when the planet is cooling/forming. In a sphere, every point on the outside is equidistant from the centre of gravity, so it wouldn't make sense to have obvious "points", if every part is under equal gravity.

Though it's worth noting that the earth is more ovalish (squashed at the poles), which probably has something to do with the fact that the points at the equator are rotating faster.

Beeker · 17-03-2009 8:34am

Flukey wrote: »

The size and distance fact is also why the moon almost perfectly covers the sun during a solar eclipse.

This is just co-incidence. Depending on its orbit sometimes it will not cover it perfectly as it is too far from the Earth. This is a Annual eclipse {or something like that}. The moon is moving away from the Earth aswell so years ago it was a lot closer so not covering the sun perfectly and in the future it will be farther away so again it will be too small to cover the sun perfectly.

Lets get a grip here there are no Gods or spooky beings messing around with us.

Joey the lips · 17-03-2009 8:44am

aaronh007 wrote: »

I have a question..

Why are all planets and moons spherical? why are there no cube shaped planets or moons??

Its app got to do with rotation. In theory if you take a square pce of whatever and spin it long enough it "rounds itself" You can read about it if you google I am sure!

Stick to the cheese idea I was getting hungry there!

Beeker · 17-03-2009 2:11pm

Joey the lips wrote: »

Its app got to do with rotation. In theory if you take a square pce of whatever and spin it long enough it "rounds itself" You can read about it if you google I am sure!

Stick to the cheese idea I was getting hungry there!

I think its gravity not rotation. If you have enough mass therefore gravity it will naturally pull everything towards trhe center and smooth out the surface into a sphere. Asteroids do not have enough mass for their gravity to pull everything into a sphere so they have all kinds of shapes.

Joey the lips · 17-03-2009 3:13pm

Beeker wrote: »

I think its gravity not rotation. If you have enough mass therefore gravity it will naturally pull everything towards trhe center and smooth out the surface into a sphere. Asteroids do not have enough mass for their gravity to pull everything into a sphere so they have all kinds of shapes.

There is always one! Now look up how gravity is formed. It results from the rotation amounst other things. Asteroids do actually have a gravational pull believe it or not none more famous than haleys commet!

Biro · 17-03-2009 8:31pm

Beeker wrote: »

This is just co-incidence. Depending on its orbit sometimes it will not cover it perfectly as it is too far from the Earth. This is a Annual eclipse {or something like that}. The moon is moving away from the Earth aswell so years ago it was a lot closer so not covering the sun perfectly and in the future it will be farther away so again it will be too small to cover the sun perfectly.

Lets get a grip here there are no gods or spooky beings messing around with us.

The moon is moving away from us by a matter of centimetres every year, so the phrase "years ago" there should be explained that we're talking a long, long time. And it is close enough to almost block it completely, with just a narrow ring around it during a total eclipse.

Spear · 17-03-2009 8:50pm

Joey the lips wrote: »

There is always one! Now look up how gravity is formed. It results from the rotation amounst other things. Asteroids do actually have a gravational pull believe it or not none more famous than haleys commet!

Planets are spherical due to their own gravity upon themselves leading to a state of hydrostatic equilibrium.

http://en.wikipedia.org/wiki/List_of_Solar_System_objects_in_hydrostatic_equilibrium

Beeker · 18-03-2009 8:55am

Joey the lips wrote: »

There is always one! Now look up how gravity is formed. It results from the rotation amounst other things. Asteroids do actually have a gravational pull believe it or not none more famous than haleys commet!

Gravity is a result of mass not rotation. Even if the earth did not rotate it would have the same gravity.
Yes asteroids do have gravity, I never said they did not. They just dont have enough gravity to cause the body to colapse into a sphere.
Small point by Haleys comet is as you said a comet not an asteroid.

Joey the lips · 18-03-2009 9:05am

Beeker wrote: »

Gravity is a result of mass not rotation. Even if the earth did not rotate it would have the same gravity.
Yes asteroids do have gravity, I never said they did not. They just dont have enough gravity to cause the body to colapse into a sphere.
Small point by Haleys comet is as you said a comet not an asteroid.

Its to do with both rotation and the size of the object. Not strictly newtons theory. LOL Apologies on the comet thing it was just ment to demonstrate all bodies have a gravatational pull.

Beeker · 18-03-2009 10:29am

Joey the lips wrote: »

Its to do with both rotation and the size of the object. Not strictly newtons theory. LOL Apologies on the comet thing it was just ment to demonstrate all bodies have a gravatational pull.

Fair enough but my understanding is that rotation has no effect on gravity. A still Earth would have the same gravity as a spinning one. At least that is my understanding

Spear · 18-03-2009 1:41pm

Beeker wrote: »

Fair enough but my understanding is that rotation has no effect on gravity. A still Earth would have the same gravity as a spinning one. At least that is my understanding

There is an effect called frame dragging, but this won't impact the shape of a body.

http://en.wikipedia.org/wiki/Frame_dragging

Capt'n Midnight · 18-03-2009 10:52pm

the 400 ratio of distance / diameter is just a coincidence , as the moon recedes at a few cm per year we will get fewer full eclipses

in ancient times there were 400 days in a year and the moon was closer too with far greater tides than today

eventually the moon will slow down the earths rotation so that the moon only be visible from one side of the earth, and then the moon will come back in towards us. not sure if it will give us a set of rings but it will break up and bombard the earth with metorites and stuff

Ping Chow Chi · 19-03-2009 12:48pm

If it starts to come back towards us, how comes it will break up rather than just smash into the earth?

Capt'n Midnight · 19-03-2009 12:53pm

Ping Chow Chi wrote: »

If it starts to come back towards us, how comes it will break up rather than just smash into the earth?

http://en.wikipedia.org/wiki/Roche_limit

MooseJam · 19-03-2009 9:04pm

Because of gravity - all matter is attracted to all matter by gravity - the shape that results is a sphere

AtomicHorror · 22-03-2009 9:36pm

Joey the lips wrote: »

There is always one! Now look up how gravity is formed. It results from the rotation amounst other things.

No it doesn't... Rotation results in a force that works outwards perpendicular to the axis of rotation, not inwards. Objects that form by accretion tend to rotate in response to gravity, but that rotation if anything acts against the formation of perfect spheres (you can see that in Jupiter). Planets and large moons are spherical because of their mass. Large mass equals large gravity equals hydrostatic equilibrium equals sphere shape and differentiation of layers of material in the body.

professore wrote: »

C'mon guys we all know It's a giant spaceship. See here :
http://www.theforbiddenknowledge.com/hardtruth/moon_spaceship.htm

"HYPOTHESIS I. The Moon was once a part of the Earth and broke away from it.

This has now been refuted by the evidence."

That's funny and depressingly misinformed at the same time. Last I checked, the Thea hypothesis was the leading hypothesis on the formation of the moon, the best supported by the evidence, and certainly not "refuted by the evidence".

kujosHeist · 23-03-2009 1:27am

unsubstantiated claim here but wasn't the moons rocks brought back by US and Russian missions made up of a different composition than earth rocks making it inpossible for the moon to have been formed from an impact with earth

Spear · 23-03-2009 2:27am

kujosHeist wrote: »

unsubstantiated claim here but wasn't the moons rocks brought back by US and Russian missions made up of a different composition than earth rocks making it inpossible for the moon to have been formed from an impact with earth

Giant impact theory is the received wisdom.

http://en.wikipedia.org/wiki/Moon#Formation

The moon rocks returned to earth showed some of the same isotope patterns as the Earth's crust.

Redshift · 09-05-2009 3:04pm

This thread has been tidied up and renamed, no more rubbish posts or conspiracy stuff please. We have other forums for that!

kujosHeist · 10-05-2009 10:39pm

nice one redshift its good to see censorship is alive and well on the internet today

A7X · 10-05-2009 11:49pm

kujosHeist wrote: »

nice one redshift its good to see censorship is alive and well on the internet today

FYI there is a a few threads on this in the conspiracy theory forum so no censorship.

usemyillusion12 · 11-05-2009 12:29am

is it not possible that the moon just formed in the usual way to all other planets' moons ? , why do people seem to think ours is an acception ?, we are near to the sun like most small planets perhaps it formed just like the rest of our planets but just didnt grow into a small size planet , but instead a moon

also the whole rotation idea to form a sphere is obviously not right considering the way our galaxy is a disc shape due to its rotation , related to conservation of angular momentum

Redshift · 11-05-2009 2:00am

kujosHeist wrote: »

nice one redshift its good to see censorship is alive and well on the internet today

Yes, I am here to opress and censor you! it is a conspiracy:pac:

Capt'n Midnight · 11-05-2009 3:02am

usemyillusion12 wrote: »

is it not possible that the moon just formed in the usual way to all other planets' moons ?

all things are possible but that does not mean the probabilities are the same
The universe may have been sneezed out of the nose of the great green arklesizure but that theory isn't as widely accepted as say the big-bang theory.

Theories can be disproven,

I haven't looked it up but the chances of a moon the size of ours being captured stably without hitting us are probably low (anyone ?)

, why do people seem to think ours is an acception ?

LOL
thought you wrote accretion

, we are near to the sun like most small planets perhaps it formed just like the rest of our planets but just didnt grow into a small size planet , but instead a moon

well the theory is that a mars sized object hit an earth sized one, both grew..

also the whole rotation idea to form a sphere is obviously not right considering the way our galaxy is a disc shape due to its rotation , related to conservation of angular momentum

mountains can only be so tall , this depends on what they are made of and how strong gravity is. so for most panetoids a limit of about 400 miles means you get a spherical body. try to imagine why the tallest mountains on our planet are only 8Km high instead of 8,000Km like you would expect on a non spherical body

Origin of the Moon

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