Re: Chez Watt: There can be no Evolution by natural selection DJT

From: Christopher Denney <christopher.denney@xxxxxxxxx>:
On Oct 29, 2:44 pm, Rusty Sites <SpameYou...@xxxxxxxxxx>
wrote:
Christopher Denney wrote:

<Snip>

The displacement of an object depends only on how much volume
is enclosed by it's surface.

Here's your mistake, the displacement is how much of the volume is
actually in the water, which depends on the weight.

The part that is above the waterline isn't actually displacing any
water, because there was no water there to be displaced! (just air!)

If the object is floating, it depends only on the weight of the
object. If it is submerged, then the displacement only depends on
its volume.

If an object floats in water it's because it's density is less
than that of the water it's floating in.

Your experiment is both changing the density of the object, and
it's total volume.

And their effects on the displacement cancel out.

Yes, but the point was that adding air to the iceberg does
not change the amount of water is displaces.

Actually it does,

Not.

the iceberg is bigger because of the trapped
air, than it would be if it had no trapped air.

Yes but (apart from the effects of compression) that increase in
size is _above_ the waterline (as you say, it rides higher in the
water) so it displaces more _air_ not more water.

The trapped
air displaces ice that would otherwise occupy it's volume.
Thus the density of the iceberg is less than just ice. (i.e.
it's bigger for the same mass of ice)

Right.

Thus the amount of
water, per unit mass, displaced is increased.

Decreased!
Same displacement divided by increased mass makes a decrease.

That means that
for every unit of mass of ice, the iceberg with air trapped
will ride higher in the water than the same mass of ice with
no air trapped, because it is less dense.

Right, and by shear coincidence (NOT!) it will ride enough higher
that it displaces the same amount of water as before (ignoring
compression)

A real good demonstration, imagine a solid lead ball, will is
sink or float in water? Now form that solid ball into a sphere
that is hollow, using the same mass of lead. Amazingly it
floats, why? Because the mass of the water it displaces
is more than the mass of then lead(and air).

It would be more if you held it underwater, but it wouldn't be
floating then would it?

The system is
less dense because it has air trapped inside, the hollow
sphere is bigger than the solid one.

What is this supposed to demonstrate?

Eric




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