Re: How the comet flies

In article <ggdp0398sjudfpii1cue6223n6g11ub6so@xxxxxxx>,
Ye Old One <usenet@xxxxxxxxx> wrote:

On Thu, 29 Mar 2007 20:37:45 -0700, Timberwoof
<timberwoof.spam@xxxxxxxxxxxxxxxxxxxxx> enriched this group when s/he
wrote:

In article <g60p03lrj8pjssvcimlqjhfth10j9g4b6o@xxxxxxx>,
Desertphile <desertphile@xxxxxxxxxx> wrote:

On 28 Mar 2007 23:05:24 -0700, "nando_ronteltap@xxxxxxxxx"
<nando_ronteltap@xxxxxxxxx> wrote:

There is one way to regard the future which we know is correct, and
that is the way we know by experience. In the present we decide from
alternatives that we know are in the future and by that decision we
determine our past.

Your way of past, present, future simply does not work. You are always
stuck in the past. Your kind of future is not the actual future, but a
later past. You always look to the past, because that is where you
have all the information.

WTF? Humans do indeed make decisions; comets, planets, asteroids,
and satellites do not. Earth's satellite, the moon, will always be
exactly where humans compute it will be, baring natural forces
such as the close passage of a currently unforseen mass sufficient
to perturb the Earth-Luna barycenter. This means Luna will never
deviate from its claculated orbit even when projected hundreds of
thousands of years into the future.

If you have any evidence to the contrary, what haven't you
produced it yet?

A few years ago I read of an astronomer who built a computer
specifically to compute orbits over billions of years ("Digital
orrery"). He calculated the model backwards for four billion years. Then
he moved Pluto by the least significant bit in its position and ran it
forward again for four billion years. Pluto ended up on the other side
of the solar system. The conclusion is that a planetary system is
chaotic (in the technical sense, of course): it is sensitive to initial
conditions.

In fact a web site that has been referred to in this discussion lists
specifically the margins of error in the calculations. So it is only
fair to say "exactly, within limits imposed by our accuracy of
measurement and calculation."

There is only one variable that is unknown in the Sun/Earth/Moon
system which _MAY_ produce a notable effect over a period of 100
million years. This variable relates to the possible effect caused by
plate tectonic movement which may change the value of tidal drag.

For example, if the Antarctic was to drift north and collide with
Africa tidal drag would increase by a factor which would very slightly
increase the slowing of Earth rotation. Over the time scale we are
talking about that would add a few seconds difference to the moment of
totality.

Without an external influence, this is the only variable that could
have an effect in the 100 million year time frame.

Sure, maybe. I bet that the different rotation rates of the Earth's
crust/mantle and inner core will also affect things. But that's beside
my point, which you seem to be missing You may be able to identify all
the parameters that affect planetary orbits, but you can know their
values only to some limited accuracy. Hence the result about Pluto from
the digital orrery.

--
Timberwoof <me at timberwoof dot com> http://www.timberwoof.com
Level 1 Linux technical support: Read The Fscking Manual!
Level 2 Linux technical support: Write The Fscking Code Yourself!

.

Relevant Pages

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