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Hollow Moon


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There does seem to be more geological activity happening on the Moon that once believed.

 

Relatively young thrust faults have been found on the Moon and their is evidence that the Moon is shrinking. The mechanism for this, as far as I know is not understood but could be due to the core cooling and contracting. Have a look at the Lunar Reconnaissance Orbiter news release here.

 

I don't know if this was the motivation for the opening question?

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The reason I ask is when of the moon missions landed it hit the moon fairly hard and made an echo noise. Now I find the prospect that the moon could be hollow is quite interesting. I just asked in case it was true.

 

I haven't heard about this echo noise. Where did you learn about this?

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The reason I ask is when of the moon missions landed it hit the moon fairly hard and made an echo noise. Now I find the prospect that the moon could be hollow is quite interesting. I just asked in case it was true.

 

You are most likely thinking about the seismic "ringing" produced by the discarded lunar module and third stage that ended up impacting on the Moon (not the landings themselves). Despite the claims of a number of crackpots, this is not indicative of the Moon being hollow.

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In order for something the size and mass of the moon to be hollow, it would have to be made of some material far stronger than anything known, or else it would collapse into a solid ball like everything else of large mass.

 

Luckily, though, we don't have to explain such a material or come up with some way such a structure might form, because the moon is solid.

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"Neal and a team of 15 other planetary geologists have reexamined data from seismometers placed by Apollo astronauts at lunar landing sites from 1969 to 1972. They found that instruments from Apollo missions 12, 14, 15 and 16 consistently radioed back seismic data to Earth until they were turned off in 1977 in a NASA cost-cutting measure."

 

"Neal points out that vibrations from most earthquakes cease in less than a minute. The biggest earthquakes stop shaking in less than two minutes. The shallow quakes on the moon produced movement that continued for more than 10 minutes."

 

http://www.physorg.com/news63645811.html

 

Thus one of the reasons for the comparison to a bell and the idea that the moon is hollow.

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The moonquakes were classified as

 

1) due to impacts, including 1000's of meteorites as well as due to the landings themselves.

 

2) thermal due to the heating and cooling as the Sun rises and falls. These are weak and near the surface.

 

3) shallow believed to be tectonic in origin and originate from bellow the crust.

 

4) deep which are the most common and are due to tidal forces between the Moon, Earth and Sun. These can be periodic and quite predictable.

 

Anyone interested should google "moonquakes".

 

Is the idea of a hollow moon due to H.G. Wells?

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  • 3 weeks later...

Interesting Question

 

Given what I understand about gravity.

 

1. If you were in a room in the center of the moon then you would be weightless. Your body would be gravitationally attracted to the moon mass to your right and left equally and the forces would cancel each other out. This would happen in all directions and the net gravitational force would be "0". True?

 

2. If you were 10 miles away from the center of the moon then you would be attracted up to the surface by the mass above you and down to the center by the larger mass of the moon below. Right and left of you would cancel each other out again and you would only have up and down forces to contend with. Your weight would be increasing as you approach the surface. True?

 

3. Once you get to the surface of the moon then you would have your maximum weight because all moon mass would be pulling you down.

 

4. As you proceed up above the moon surface your gravitational attraction would decrease the further away you moved from the moon. True?

 

OK lets just say that the moon has a 300 mile hollow sphere inside it. (just for the sake of argument) If you were standing against the inside surface of this sphere then would you not be attracted to the mass away from the center more than the mass toward the center. You would be closer to the overhead mass and its gravity would have a stronger influence on you. The remaining moon away from you would have more mass but it would also be further away and your net gravity would be toward the surface. Is this possible?

 

Then just maybe it is possible for a hollow sphere to exist.

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1. If you were in a room in the center of the moon then you would be weightless. Your body would be gravitationally attracted to the moon mass to your right and left equally and the forces would cancel each other out. This would happen in all directions and the net gravitational force would be "0". True?

True, assuming the moon's density is uniform.

 

2. If you were 10 miles away from the center of the moon then you would be attracted up to the surface by the mass above you and down to the center by the larger mass of the moon below. Right and left of you would cancel each other out again and you would only have up and down forces to contend with. Your weight would be increasing as you approach the surface. True?

True, if we're not talking about a hollow moon. If you have a hollow shell and you move around inside the hollow space, there will be 0 net gravitational force anywhere. Once you start traveling through the solid parts, you will begin feeling gravity as you described.

 

3. Once you get to the surface of the moon then you would have your maximum weight because all moon mass would be pulling you down.

 

4. As you proceed up above the moon surface your gravitational attraction would decrease the further away you moved from the moon. True?

Yup.

 

OK lets just say that the moon has a 300 mile hollow sphere inside it. (just for the sake of argument) If you were standing against the inside surface of this sphere then would you not be attracted to the mass away from the center more than the mass toward the center. You would be closer to the overhead mass and its gravity would have a stronger influence on you. The remaining moon away from you would have more mass but it would also be further away and your net gravity would be toward the surface. Is this possible?

Not quite, as I described above. See the shell theorem:

 

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

 

If the body is a spherically symmetric shell (i.e. a hollow ball), no gravitational force is exerted by the shell on any object inside, regardless of the object's location within the shell.
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