Robert Santerre on sun 8 may 11
Hi Wayne,
Your response to Phil is not totally accurate (and I don't want Phil to go
through life in Vegas disillusioned about how gravity can affect him). It's
true that "mass is mass", and from the moon's point of view shrinking the
earth's size by half while maintaining its current mass would not change th=
e
earth's gravitational pull on the moon (assuming the moon stays in its same
orbit). On the other hand, for a person standing on the shrunken earth's
surface the gravitational pull that person feels will be greater because
that person is now closer to the center of the earth's mass. Gravitational
strength is a function of the square of the distance from the "center" of a
mass.
Think of it this way ... black holes are stars that have collapsed to a siz=
e
so small that nothing (light, x-rays, etc.) can escape their gravitational
pull. No light escapes, we can't see them so we call them "black holes".
There's a region of the warpped space around a black hole called the "event
horizon". Any matter particle (a photon for example) that passes through
this event horizon is drawn into the black hole never to escape because the
gravitational pull is too great. Before it collapsed this black hole was a
star and it emitted lots of photons (light). As a star it could emit these
photons because they were being emitted from the surface ... a long way fro=
m
the center of its mass, but when that star burned out and it collapsed to a
black hole the "surface" of that black hole (the surface of that shrunken
mass) is now many, many times closer to the center of its mass and the
gravitational pull at that surface (or at its "event horizon") is many, man=
y
times greater than the gravitational pull was at the surface of the origina=
l
star.
You DEFINITELY don't want to get too close to the center of a black hole ..=
.
and if the earth's mass collapsed to one half its current radius the
gravitational pull you would feel standing on that shrunken surface would b=
e
4 times what you are feeling right now ... what would that be, close to 800
lbs? You'd feel like you ate one GIANT batch of brownies! It would
probably start to get a little crowded too ... even in northern Maine.
On the other hand, if the earth expanded to 2 times its current radius you'=
d
feel like you could fly! You'd weigh 4 times less, approaching 50 lbs (Phi=
l
would probably weigh about 25 lbs ... he'd really be flyin'). That's why
the astronauts are always smiling.
I bet you could throw one heckuva pot!
Had to get this back to clay somehow ... Mel's rule.
Bob
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-----Original Message-----
From: Clayart [mailto:Clayart@LSV.CERAMICS.ORG] On Behalf Of WJ Seidl
Sent: Saturday, May 07, 2011 7:49 AM
To: Clayart@LSV.CERAMICS.ORG
Subject: Re: nils/mel's wheel.
Phil:
For shame! You know better than that, a smart gentleman like yourself!
That's basic science.
Mass is mass, no matter the size. Assuming a vacuum, gravitational pull
of two bodies of equal mass will be the same.
Now if you're talking GRAVITY acting on two objects of differing size
but the same mass, that's something else again.
(In other words, a balloon having a mass of two hundred pounds and a
potter weighing two hundred pounds being tossed at the same time off the
top of a building; which will hit first...)
If in a vacuum, they should both hit at nearly the same time (perfect
vacuums being so hard to come by these days, it's hard to prove)
but in our atmosphere, the object with the most surface area will hit
slower than the other because of friction with the molecules of the air,
smog, birds, airplanes, suicidal lovers, anything that gets in the way
of the falling object....
I'll leave it to you to decide whether a 200 pound balloon or a 200
pound potter has more surface area. )
Best,
Wayne Seidl
On 5/7/2011 4:04 AM, pdp1 wrote:
>
> So...if the Earth were say, one half the diameter it is now, but,
> solid...would Gravity be about the same at it's surfaces as, or different
> from, a condition in which the Earth were about the same mass as ever,
> but,
> were about two times larger in diameter, and, Hollow?
>
>
>
> Phil
> L v
pdp1 on sun 8 may 11
Hi Robert,
Thanks for the mentions.
I believe the Center of Mass for a Hollow Sphere, would still be the
geometric Center, even if there is nothing there otherwise...at least as
long as the walls were of fairly uniform density, anyway.
Yes?
I also imagine, that in the scenario of an Earth which is 'solid' to the
Core, that the Core would not be the heaviest portion, but, that the
heaviest portion ( assuming the ingredients had been able to distribute
themselves at least somewhat, accorging to their specifi Gravity ) would be
mid-way between the surface, and, the center or core, where, the force of
Gravity would be strongest.
I imagine the Center of the Earth, to be a location of weightlessness, and,
hence, a condition where the gravitational forces of the surrounds, in
effect, cancel eachother out.
If in our imaginary exercise, we take the Earth to be the diameter and mass
it is now, only hollow, and, accept
it's diameter to be about 7,900 Miles...and showing the same
measurements of Gravity on it's surface as it does now...
If the Earth were instead, about 1/2 it's present surface area, and solid t=
o
the core, and of
the same mass as it is now...Gravity
then, on the surface, would be...?
And to be candid, I had imagined originally, that Gravity in the two
respective conditions, would not be much different...even though it appears
now that this would be incorrect.
Love,
Phil
Lv
----- Original Message -----
From: "Robert Santerre"
> Hi Wayne,
>
> Your response to Phil is not totally accurate (and I don't want Phil to g=
o
> through life in Vegas disillusioned about how gravity can affect him).
> It's
> true that "mass is mass", and from the moon's point of view shrinking the
> earth's size by half while maintaining its current mass would not change
> the
> earth's gravitational pull on the moon (assuming the moon stays in its
> same
> orbit). On the other hand, for a person standing on the shrunken earth's
> surface the gravitational pull that person feels will be greater because
> that person is now closer to the center of the earth's mass.
> Gravitational
> strength is a function of the square of the distance from the "center" of
> a
> mass.
>
> Think of it this way ... black holes are stars that have collapsed to a
> size
> so small that nothing (light, x-rays, etc.) can escape their gravitationa=
l
> pull. No light escapes, we can't see them so we call them "black holes".
> There's a region of the warpped space around a black hole called the
> "event
> horizon". Any matter particle (a photon for example) that passes through
> this event horizon is drawn into the black hole never to escape because
> the
> gravitational pull is too great. Before it collapsed this black hole was
> a
> star and it emitted lots of photons (light). As a star it could emit
> these
> photons because they were being emitted from the surface ... a long way
> from
> the center of its mass, but when that star burned out and it collapsed to
> a
> black hole the "surface" of that black hole (the surface of that shrunken
> mass) is now many, many times closer to the center of its mass and the
> gravitational pull at that surface (or at its "event horizon") is many,
> many
> times greater than the gravitational pull was at the surface of the
> original
> star.
>
> You DEFINITELY don't want to get too close to the center of a black hole
> ...
> and if the earth's mass collapsed to one half its current radius the
> gravitational pull you would feel standing on that shrunken surface would
> be
> 4 times what you are feeling right now ... what would that be, close to
> 800
> lbs? You'd feel like you ate one GIANT batch of brownies! It would
> probably start to get a little crowded too ... even in northern Maine.
>
> On the other hand, if the earth expanded to 2 times its current radius
> you'd
> feel like you could fly! You'd weigh 4 times less, approaching 50 lbs
> (Phil
> would probably weigh about 25 lbs ... he'd really be flyin'). That's why
> the astronauts are always smiling.
>
> I bet you could throw one heckuva pot!
>
> Had to get this back to clay somehow ... Mel's rule.
>
> Bob
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