Nick wrote:

Jesse Mazer wrote:


Nick wrote:



No. The spaceship is not at rest if it is moving through space
to werever its going Jesse.





But my scenario was that it's *not* moving, that it started off


moving


but then decelerated until it was at rest relative to absolute


space.


Isn't anything that's at rest relative to absolute space "not


moving",


by definition?

Jesse



The problem is everything has aquired motion through space at
creation. That is what forces are about.

Call it original motion or the starting gate so to speak.

Look at gravity; it is everywhere and it moves objects through
space-time; and there's space's motion of expansion which is like
anti-gravity.




OK, but if you've "acquired motion" relative to absolute space, why
can't you cancel out this motion by accelerating in the opposite
direction until you are at rest relative to absolute space? If I hit the
gas pedal to accelerate in one direction, I acquire motion relative to
the road, but if I hit the brake to decelerate (ie accelerate in the
opposite direction), I can come back to a halt relative to the road. Why
wouldn't it be possible to do the same sort of thing in order to come to
a halt relative to absolute space?

Jesse

Jesse Mazer wrote:
Nick wrote:

Jesse Mazer wrote:


Nick wrote:



No. The spaceship is not at rest if it is moving through space
to werever its going Jesse.





But my scenario was that it's *not* moving, that it started off


moving


but then decelerated until it was at rest relative to absolute


space.


Isn't anything that's at rest relative to absolute space "not


moving",


by definition?

Jesse



The problem is everything has aquired motion through space at
creation. That is what forces are about.

Call it original motion or the starting gate so to speak.

Look at gravity; it is everywhere and it moves objects through
space-time; and there's space's motion of expansion which is like
anti-gravity.




OK, but if you've "acquired motion" relative to absolute space, why
can't you cancel out this motion by accelerating in the opposite
direction until you are at rest relative to absolute space? If I hit
the
gas pedal to accelerate in one direction, I acquire motion relative
to
the road, but if I hit the brake to decelerate (ie accelerate in the
opposite direction), I can come back to a halt relative to the road.
Why
wouldn't it be possible to do the same sort of thing in order to come
to
a halt relative to absolute space?

Jesse

Yes I follow you. That make's sense.

But "space" moves and shares its motion with matter.
This can be seen by the expansion of space carrying the
galaxies away from one another.
I believe in absolute space but I also believe space can move.

Nick wrote:
Randy Poe wrote:

You don't think the earth is moving?
Not toward the spaceship Randy!!!

No? If I were plotting an Earth to Mars trip, I would
definitely take advantage of the Earth's motion so that
I would make sure that the earth WAS traveling toward
the ship.

It's a journey of months. The earth moves in its orbit
about 78 million km per month. You'd be an idiot
not to plan things to take advantage of that motion,
so that the earth is moving toward the spaceship.

Get it straight Ninkumpoop.

That's nimcompoop. Don't use big words if you don't know
how to spell them.

- Randy

Franz Heymann wrote:
"Androcles" wrote in message
k...

[snip]

Poe snips any questions I have and imagines he can teach
that way. He knows nothing about frames and is making a
complete fool of himself.

Not so. The general perceptionis that he is making a valiant, but
doomed, effort to conduct a discourse with a monkey.
The monkey won.

- Randy

"Randy Poe" wrote in message oups.com...

Franz Heymann wrote:
"Androcles" wrote in message
k...

[snip]

Poe snips any questions I have and imagines he can teach
that way. He knows nothing about frames and is making a
complete fool of himself.

Not so. The general perceptionis that he is making a valiant, but
doomed, effort to conduct a discourse with a monkey.

The monkey won.

They always win, for the simple reason that you play
by rules and they don't.
There is one remaining option: don't play with them,
but either ignore them or smack them in the face :-)

You made a remarkably heroic effort though.

Cheers,
Dirk Vdm

Randy Poe wrote:
Nick wrote:
Randy Poe wrote:

You don't think the earth is moving?
Not toward the spaceship Randy!!!

No? If I were plotting an Earth to Mars trip, I would
definitely take advantage of the Earth's motion so that
I would make sure that the earth WAS traveling toward
the ship.

It occurs to me that perhaps Nick/Mitch thinks of
a Mars-Earth or Earth-Mars trip as being radially
in or out from the sun.

Not so. It is a spiral, taking much more distance
laterally than radially. See this for instance:

http://www.spaceref.com/tools/vi.htm...=mediumimag e

Same link: http://tinyurl.com/5hysu

Notice on this journey from earth to mars that mars
is moving toward the spacecraft.

- Randy

Nick wrote:

Jesse Mazer wrote:


Nick wrote:



Jesse Mazer wrote:




Nick wrote:





No. The spaceship is not at rest if it is moving through space
to werever its going Jesse.







But my scenario was that it's *not* moving, that it started off




moving




but then decelerated until it was at rest relative to absolute




space.




Isn't anything that's at rest relative to absolute space "not




moving",




by definition?

Jesse




The problem is everything has aquired motion through space at
creation. That is what forces are about.

Call it original motion or the starting gate so to speak.

Look at gravity; it is everywhere and it moves objects through
space-time; and there's space's motion of expansion which is like
anti-gravity.





OK, but if you've "acquired motion" relative to absolute space, why
can't you cancel out this motion by accelerating in the opposite
direction until you are at rest relative to absolute space? If I hit


the


gas pedal to accelerate in one direction, I acquire motion relative


to


the road, but if I hit the brake to decelerate (ie accelerate in the
opposite direction), I can come back to a halt relative to the road.


Why


wouldn't it be possible to do the same sort of thing in order to come


to


a halt relative to absolute space?

Jesse



Yes I follow you. That make's sense.

But "space" moves and shares its motion with matter.
This can be seen by the expansion of space carrying the
galaxies away from one another.
I believe in absolute space but I also believe space can move.




OK, but imagine a situation where space is not expanding, or the rate of
expansion is minimal compared to the movement of the objects we're
looking at. Now suppose we have two planets moving in the same direction
and at the same velocity through absolute space, say, 10 km/sec. Now a
rocket on one of the planets fires in the opposite direction, causing it
to decelerate with respect to absolute space, until it is at rest
relative to absolute space, at which point the rocket stops firing. Now
the rocket will be standing still in absolute space, while the planet it
took off from will still be moving away from it at 10 km/sec, while the
other planet will be moving towards it at 10 km/sec. In this case,
although from the point of view of observers on each planet it *looks*
like the rocket is moving from one planet to the other at 10 km/sec,
from the point of view of absolute space it's actually the planets that
are moving and the rocket that is standing still. Do you agree that this
is possible, if absolute space exists?

Jesse

"Randy Poe" wrote in message
ups.com...

Notice on this journey from earth to mars that mars
is moving toward the spacecraft.

Huh? You sure of that? Wasn't Joe walking away
from the mosquito, yet the distance between them
still closed?
Androcles.

In article . com, "Randy Poe" writes:
It occurs to me that perhaps Nick/Mitch thinks of
a Mars-Earth or Earth-Mars trip as being radially
in or out from the sun.

Not so. It is a spiral, taking much more distance
laterally than radially. See this for instance:

I thought that a Hohman transfer orbit from Earth to Marse is
just an ellipse tangent to the Earth's orbit at perigee and tangent
to Mars' orbit at apogee. You launch from Earth and do a burn to
accelerate into the transfer orbit. Then you coast. When you hit the
orbit of Mars (180 degrees away on the opposide side of the sun from the
launch point, if we were using a pure Hohman transfer from one circular
orbit to another) you do another burn to accelerate to keep up with Mars.
And you time the original launch so that when you arrive in Mars orbit,
Mars is there.

I believe the Hohman transfer orbit is the minimum energy solution.

Roughly speaking, it will take (one earth year + one mars year ) / 4
to get there. If that's unacceptable, you can trade increased energy
requirements to buy decreased transit time.


http://www.spaceref.com/tools/vi.htm...=mediumimag e

Same link: http://tinyurl.com/5hysu

Yup. Looks tolerably like a Hohman. Exploiting the fact that Mars orbit
is elliptical and squeezing things a little so that the launch and
arrival points are only 150 degrees apart instead of 180.

John Briggs

Androcles wrote:
"Randy Poe" wrote in message
ups.com...

Notice on this journey from earth to mars that mars
is moving toward the spacecraft.

Huh? You sure of that?

No. I deleted the message a couple of minutes after
posting it. I misread that particular diagram, in which
the rocket is playing catchup with Mars.

Thinking about this a little more, I realize that this
does make sense since the orbital velocity you start with
from Earth is faster than that of Mars.

Actually (further reading on "Hohman transfer") it appears
that the Hohman transfer orbit is in the SAME direction as
orbits of earth and mars in BOTH directions, and
if I understand it what you're doing is putting yourself
into an ellipse around the sun which closely matches
the velocities of both earth and mars. The orbital mechanics
do the velocity matching for you. On the way home, you
catch up with earth's speed just from the KE you gain
by falling toward the sun.

This is all from considerations of minimum energy. I
was thinking of minimum time, where I'm pretty sure
that you'd want to go TOWARD the body you're trying
to reach.

Wasn't Joe walking away
from the mosquito, yet the distance between them
still closed?

Yes. The question is why you'd want to play catch
up instead of going the other way. The answer is that
this minimizes the energy you have to expend.

In either direction, the description of a rocket moving
while the planet sits still is not a very useful
description.

- Randy