Invisible <voi### [at] devnull> wrote:
> 1. If the Earth is hollow, wouldn't that *significantly* alter its mass?

  The only claim that I have ever seen to explain that is that the "inner
sun" accounts for the missing mass.

> 2. A hollow Earth-sized structure with a vacuum inside would surely 
> collapse pretty quickly, no matter what you made it of, but if it was 
> filled with an atmosphere of some kind, at absurd pressure, it might 
> work. (Isn't that what a bubble is, after all?)

  No amount of atmosphere would be able to hold the shell under Earth's
gravity. It would just crumble and collapse. The only reason why the
Earth does not collapse is because it's fully made of rock and metal.
(No double entendre intended.)

> 3. It's not quite correct to say that "no force" would hold people's 
> feet onto the anti-ground. There is one: centrifugal force due to the 
> Earth's rotation. Sure, it's a force several orders of magnitude too 
> small to make the slightest shred of difference, but it's real.

  Even at the equator it's over 300 times weaker than g. That means that
if someone were to make a jump at the equator that would normally boost
him 1 meter into the air, would boost him over 300 meters into the air.

  Anyways, the majority of these hollow Earth theories claim that there's
an "inner sun" at the center of the Earth (which explains how the interior
surface of the Earth is habitable). The gravity of that sun would be strong
enough to pull anything on the inner surface of the Earth, which would then
fall into this 'sun'.

> 4. A *star* inside Earth? Um... do these people know how big stars 
> actually are? If you hollowed out the Sun, you could fit one million 
> copies of the Earth inside it - and the Sun isn't a particularly large star!

  A body of eg. the size of the inner core of the Earth could indeed not
have enough mass to cause a fusion reaction, and hence it would not be a
star at all. It would be just a small moon, a lifeless rock. (It could not
be made of gas because it would be too small to maintain its shape.)

  The only "star" that small would be a neutron star, which in turn would
be *so* massive that the Earth would collapse into it in a microsecond.
(Not to talk that a neutron star does not have a fusion reaction going on
either. Also the radiation that a neutron star emits would kill all life
on earth in another microsecond.)

-- 
                                                          - Warp

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