Re: Is my friend full of BS?

On 2006-08-17, srp <srp2@xxxxxxxxxxxxxxxx> wrote:
Ben Newsam a écrit :
On Thu, 17 Aug 2006 13:54:22 GMT, "Sorcerer"
<Headmaster@xxxxxxxxxxxxxxxxxx> wrote:
"Ben Newsam" <ben.newsam@xxxxxxxxxxxxxx> wrote in message
news:q8r8e2lb4fhioveu9b8gghk2bientu6pk4@xxxxxxxxxx
| As I said above, there is no difference between your experience of
| gravity in your chair on earth, and in your chair in a continuously
| accelerating spaceship. The effects are the same.

Can't be, I move in the spacecraft relative to the ground.
I do not move relative to the ground while sitting in my chair and
the Earth is quite definitely not expanding.

I made no mention of what was actually happening, whatever that means
anyway, merely that you cannot tell the difference. Your instruments
will not be able to tell either. You will measure 1g in both cases.

In your spacecraft, the acceleration is a steady 1 g, and if you drop
a ball from shoulder high, the craft will accelerate at a steady 1 g
towards it. But on the ground, at sea level at some locations on the
planets, if you have exactly 1 g at your ground level, an identical
ball dropped from shoulder high will start by being submitted to an
acceleration slightly less than 1 g, that will gradually tend to 1 g
as it reaches the ground.

The final kinetic energy of the ball-ground collision will be slightly
less on the earth and this can be very precisely calculated and measured
by instruments.

If you've got instruments that can "precisely calculate and measure"
the difference between 1/(R_e + R_s)^2 and 1/(R_e)^2, where R_e is the
radius of the earth and R_s is the distance from your feet to your
shoulders, then you've either got some truly amazing instruments whose
working principles I would dearly love to hear about, or else you've
got the highest frigging shoulders I have ever heard of
(i.e. communications satellites flying up your nose is a frequent
problem for you).

Either way, that situation is actually _completely irrelevant_ to a
discussion of the principle of equivalence to which Ben Newsam was
alluding above:

So, even from within your spacecraft you can know that you are not
sitting somewhere on the planet, but are in a steadily accelerating
spacecraft.

The principle of equivalence is concerned with _local_ measurements.
If you've got instruments that can measure deviations in gravitational
field across your "region of interest", then that "region of interest"
is no longer "local" for purposes of discussing the equivalence
principle.

--
Darrin
.

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