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bunny
2004-Nov-03, 11:51 AM
How big can a hollow object be before its mass in the shell collapses? Put another way how big can can my honeycomb crunchie/aero choccy bar be before it gets crushed by its own weight?

Is there a correlation between an objects density and the mass it can support?

gavwvin
2004-Nov-03, 12:37 PM
that would depend on the thickness/density of the shell... and your definition of hollow- if the moon had a bubble of space at it's center 1cm^3 in volume, is it hollow?

bunny
2004-Nov-03, 01:00 PM
9. The moon's mean density is 3.34 gm/cm3 (3.34 times an equal volume of water) whereas the Earth's is 5.5. What does this mean? In 1962, NASA scientist Dr. Gordon MacDonald stated, "If the astronomical data are reduced, it is found that the data require that the interior of the moon is more like a hollow than a homogeneous sphere." Nobel chemist Dr. Harold Urey suggested the moon's reduced density is because of large areas inside the moon where is "simply a cavity." MIT's Dr. Sean C. Solomon wrote, "the Lunar Orbiter experiments vastly improved our knowledge of the moon's gravitational field . . . indicating the frightening possibility that the moon might be hollow." In Carl Sagan's treatise, Intelligent Life in the Universe, the famous astronomer stated, "A natural satellite cannot be a hollow object."



This is the crux. The difference between mean density, cavities and hollowness need to be better defined. A lower mean density does not necessarily mean a hollow centre, nor cavities which might allude to a lower mean density.

dictionary term Hollow: having a hole or space within, not being solid.

By this definition an aero/crunchie is hollow. How big could it be before its own mass collapsed to make it solid? This is obviously applicable to a hollow moon as well.

Betelgeuse
2004-Nov-03, 08:41 PM
Originally posted by bunny@Nov 3 2004, 01:00 PM

9. The moon's mean density is 3.34 gm/cm3 (3.34 times an equal volume of water) whereas the Earth's is 5.5. What does this mean? In 1962, NASA scientist Dr. Gordon MacDonald stated, "If the astronomical data are reduced, it is found that the data require that the interior of the moon is more like a hollow than a homogeneous sphere." Nobel chemist Dr. Harold Urey suggested the moon's reduced density is because of large areas inside the moon where is "simply a cavity." MIT's Dr. Sean C. Solomon wrote, "the Lunar Orbiter experiments vastly improved our knowledge of the moon's gravitational field . . . indicating the frightening possibility that the moon might be hollow." In Carl Sagan's treatise, Intelligent Life in the Universe, the famous astronomer stated, "A natural satellite cannot be a hollow object."




Here you show the density of the moon - the great density of the moon proves that it cannot be hollow.

We've had things orbiting the moon - this gravity tells us about the mas of the moon.

Regards
Rigel

astromark
2004-Nov-04, 12:32 AM
:rolleyes: If the cell structure is strong and the materials used are of the density requiered. your sphear could be made very large. It is of some note that bodies like the moon which have a lesser density than the earth, also have less mass,. there for less gravaty. less gravaty,less mass. lighter.
If we were to build your amagined structure with modern kevlar materials and specialist metals. Yes it could saport its own structure. As long as the maths is done right. Nothing is imposable, just more costly.

GOURDHEAD
2004-Nov-04, 03:21 AM
My guess is that the moon has few empty cavities, but it could have a few. Due to the large amount of water known to be present in this section of the MW, it would not be surprising to discover that much of what would otherwise be empty cavities may be water filled cavities and there may be quite a bit of it...real handy for human colonies. There are a large number of combinations of material that could result in the moon's density; if there's lotsa water, there may be an iron core. We need that excavator up there so we can get a more accurate assesment.

Matthew
2004-Nov-04, 08:49 AM
Theoretically a natural object such as the moon cannot be completely "hollow", its formation would not allow it.

Betelgeuse
2004-Nov-04, 07:32 PM
Something I found on the net supporting the hollow moon theory:

In "Moongate: Suppressed findings of The US Space Program" (1982), Nuclear Engineer and researcher/writer William L. Brian II presents evidence proving that the moon, as any hollow sphere would, "rings" when hit by asteroids or heavy space junk. And that's not all. According to Dr. Brian, "the evidence provided by Apollo seismic experiments also points to the conclusion that the moon is hollow and relatively rigid."

antoniseb
2004-Nov-04, 08:22 PM
Originally posted by Rigel@Nov 4 2004, 07:32 PM
"the evidence provided by Apollo seismic experiments also points to the conclusion that the moon is hollow and relatively rigid."
Actually, the way I heard the seismic data described it did say the moon was rigid, but that it is a solid all the way to the center with large vertical faults. The structure of the interior of the moon is seen to be solid, which, by the way, is also capable of 'ringing' in a seismic sense.

Betelgeuse
2004-Nov-05, 04:19 PM
I appologize! However, the two theory's are discussed in the evidence.

Today, I spoke to a physician about this specific topic and I was assured that my theory is correct - the moon orbits us - we work out the distance and the force and can then determine the moon's mass which is great enough for it to be solid and sturdy.

mass of the moon = 7.36 1022 kilograms

The radius of the moon is about 1740 km