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Gravitational Slingshots
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Chalky
Apr 1, 2013, 3:15:13 PM4/1/13
to
It is well known that projectiles (eg spacecraft) can have their
trajectories substantially altered via gravitational slingshot effects.
It thus strikes me as possible, via sufficiently accurate planning and
timing (or blind chance), to arrange for such a projectile to have its
direction reversed via multiple such slingshot effects. It is, of
course, even better known, that planets and comets achieve 2 such
direction reversals per orbit, as a matter of course. However, in this
latter case, such projectiles are gravitationally bound to the body
around which they orbit, by definition. Consequently, my question is as
follows:
Would it be possible, in principle, to fire a projectile from
interstellar space, such that it is returned from whence it came, via
multiple gravitational slingshot effects?
I suspect that such a conclusion, in the affirmative, might be
inconsistent with standard GR. However, I do not see, as yet, how any
such an inconsistency could completely rule out the engineering of such
a possibility.
I can be contacted direct as chalky at accelerators dot co dot uk, in
email format.
[Moderator's note: Superfluous "=" removed. Please try to figure out
how to post non-encoded plain text. -P.H.]
trajectories substantially altered via gravitational slingshot effects.
It thus strikes me as possible, via sufficiently accurate planning and
timing (or blind chance), to arrange for such a projectile to have its
direction reversed via multiple such slingshot effects. It is, of
course, even better known, that planets and comets achieve 2 such
direction reversals per orbit, as a matter of course. However, in this
latter case, such projectiles are gravitationally bound to the body
around which they orbit, by definition. Consequently, my question is as
follows:
Would it be possible, in principle, to fire a projectile from
interstellar space, such that it is returned from whence it came, via
multiple gravitational slingshot effects?
I suspect that such a conclusion, in the affirmative, might be
inconsistent with standard GR. However, I do not see, as yet, how any
such an inconsistency could completely rule out the engineering of such
a possibility.
I can be contacted direct as chalky at accelerators dot co dot uk, in
email format.
[Moderator's note: Superfluous "=" removed. Please try to figure out
how to post non-encoded plain text. -P.H.]
Phillip Helbig---undress to reply
Apr 1, 2013, 3:45:33 PM4/1/13
to
In article <28fa035b-4591-43e3...@googlegroups.com>,
principle.
> I suspect that such a conclusion, in the affirmative, might be
> inconsistent with standard GR.
Why?
> However, I do not see, as yet, how any
> such an inconsistency could completely rule out the engineering of such
> a possibility.
So you are saying that if the possibility cannot be ruled out, then GR
would be wrong if this is inconsistent with GR. The weak point is your
claim (you have presented no evidence) that this might be inconsistent
with GR. Why do you think so?
> I can be contacted direct as chalky at accelerators dot co dot uk, in
> email format.
While OK in some cases, normally questions should be answered in the
group.
Chalky <chalk...@bleachboys.co.uk> writes:
> Would it be possible, in principle, to fire a projectile from
> interstellar space, such that it is returned from whence it came, via
> multiple gravitational slingshot effects?
There is no obvious reason why this could not work, at least in
> Would it be possible, in principle, to fire a projectile from
> interstellar space, such that it is returned from whence it came, via
> multiple gravitational slingshot effects?
principle.
> I suspect that such a conclusion, in the affirmative, might be
> inconsistent with standard GR.
> However, I do not see, as yet, how any
> such an inconsistency could completely rule out the engineering of such
> a possibility.
would be wrong if this is inconsistent with GR. The weak point is your
claim (you have presented no evidence) that this might be inconsistent
with GR. Why do you think so?
> I can be contacted direct as chalky at accelerators dot co dot uk, in
> email format.
group.
Gerry Quinn
Apr 2, 2013, 3:09:35 AM4/2/13
to
In article <kjcml8$gn9$1...@online.de>, hel...@astro.multiCLOTHESvax.de
says...
of its previous velocity. So if you can turn it through any angle, you
should be able eventually to turn it right around.
It's no more a violation of GR (or anything else) than would be a car
powered by a windmill managing to make progress against the wind.
- Gerry Quinn
says...
> In article <28fa035b-4591-43e3...@googlegroups.com>,
> Chalky <chalk...@bleachboys.co.uk> writes:
>
> > Would it be possible, in principle, to fire a projectile from
> > interstellar space, such that it is returned from whence it came, via
> > multiple gravitational slingshot effects?
>
> There is no obvious reason why this could not work, at least in
> principle.
I agree. Every time the velocity is changed, the object has no memory
> Chalky <chalk...@bleachboys.co.uk> writes:
>
> > Would it be possible, in principle, to fire a projectile from
> > interstellar space, such that it is returned from whence it came, via
> > multiple gravitational slingshot effects?
>
> There is no obvious reason why this could not work, at least in
> principle.
of its previous velocity. So if you can turn it through any angle, you
should be able eventually to turn it right around.
It's no more a violation of GR (or anything else) than would be a car
powered by a windmill managing to make progress against the wind.
- Gerry Quinn
J. J. Lodder
Apr 2, 2013, 10:49:31 AM4/2/13
to
Chalky <chalk...@bleachboys.co.uk> wrote:
> It is well known that projectiles (eg spacecraft) can have their
> trajectories substantially altered via gravitational slingshot effects.
> It thus strikes me as possible, via sufficiently accurate planning and
> timing (or blind chance), to arrange for such a projectile to have its
> direction reversed via multiple such slingshot effects. It is, of
> course, even better known, that planets and comets achieve 2 such
> direction reversals per orbit, as a matter of course. However, in this
> latter case, such projectiles are gravitationally bound to the body
> around which they orbit, by definition. Consequently, my question is as
> follows:
>
> Would it be possible, in principle, to fire a projectile from
> interstellar space, such that it is returned from whence it came, via
> multiple gravitational slingshot effects?
In general, no.
> It is well known that projectiles (eg spacecraft) can have their
> trajectories substantially altered via gravitational slingshot effects.
> It thus strikes me as possible, via sufficiently accurate planning and
> timing (or blind chance), to arrange for such a projectile to have its
> direction reversed via multiple such slingshot effects. It is, of
> course, even better known, that planets and comets achieve 2 such
> direction reversals per orbit, as a matter of course. However, in this
> latter case, such projectiles are gravitationally bound to the body
> around which they orbit, by definition. Consequently, my question is as
> follows:
>
> Would it be possible, in principle, to fire a projectile from
> interstellar space, such that it is returned from whence it came, via
> multiple gravitational slingshot effects?
Coming in from an arbitrary direction you will not meet any planets,
Jan
[Moderator's note: I think the response is based on a misunderstanding.
Note above "sufficiently accurate planning and timing (or blind
chance)"; in other words, the original poster was imagining this to be
an exception, not the rule. The question is whether it is possible at
all, not whether it is possible coming in from an arbitrary direction.
-P.H.]
Rich L.
Apr 2, 2013, 10:49:53 AM4/2/13
to
On Monday, April 1, 2013 2:15:13 PM UTC-5, Chalky wrote:
> It is well known that projectiles (eg spacecraft) can have their
> trajectories substantially altered via gravitational slingshot effects.
> It thus strikes me as possible, via sufficiently accurate planning and
> timing (or blind chance), to arrange for such a projectile to have its
> direction reversed via multiple such slingshot effects. It is, of
> course, even better known, that planets and comets achieve 2 such
> direction reversals per orbit, as a matter of course. However, in this
> latter case, such projectiles are gravitationally bound to the body
> around which they orbit, by definition. Consequently, my question is as
> follows:
>
> Would it be possible, in principle, to fire a projectile from
> interstellar space, such that it is returned from whence it came, via
> multiple gravitational slingshot effects?
Don't non-periodic comets do this all the time?
> It is well known that projectiles (eg spacecraft) can have their
> trajectories substantially altered via gravitational slingshot effects.
> It thus strikes me as possible, via sufficiently accurate planning and
> timing (or blind chance), to arrange for such a projectile to have its
> direction reversed via multiple such slingshot effects. It is, of
> course, even better known, that planets and comets achieve 2 such
> direction reversals per orbit, as a matter of course. However, in this
> latter case, such projectiles are gravitationally bound to the body
> around which they orbit, by definition. Consequently, my question is as
> follows:
>
> Would it be possible, in principle, to fire a projectile from
> interstellar space, such that it is returned from whence it came, via
> multiple gravitational slingshot effects?
> I suspect that such a conclusion, in the affirmative, might be
> inconsistent with standard GR. However, I do not see, as yet, how any
> such an inconsistency could completely rule out the engineering of such
> a possibility.
non-periodic comet (one that is on a parabolic orbit) exits going back
in the direction it came, but with a lateral offset. Taking advantage
of the non-inverse square gravitational field of GR one can find an
orbit that would return the comet to it's exact starting point.
Rich L.
b...@birdband.net
Apr 2, 2013, 5:36:31 PM4/2/13
to
On Monday, April 1, 2013 2:15:13 PM UTC-5, Chalky wrote:
> Would it be possible, in principle, to fire a projectile from
> interstellar space, such that it is returned from whence it came, via
> multiple gravitational slingshot effects?
>
this type of maneuver was used to put the cassini probe in orbit with saturn.
> interstellar space, such that it is returned from whence it came, via
> multiple gravitational slingshot effects?
>
it is called gravity assist and it's nothing new and totally consistent with GR.
the probe was first sent to the suns direction to gain speed and then the optimum
angular position for gravitational insertion.
r.y
robert bristow-johnson
Apr 2, 2013, 5:36:42 PM4/2/13
to
On 4/1/13 3:15 PM, Chalky wrote:
>
>
> Would it be possible, in principle, to fire a projectile from
> interstellar space, such that it is returned from whence it came, via
> multiple gravitational slingshot effects?
>
i'm just an electrical engineer, but i understand Newtonian mechanics
>
>
> Would it be possible, in principle, to fire a projectile from
> interstellar space, such that it is returned from whence it came, via
> multiple gravitational slingshot effects?
>
reasonably well for a physics imbecile.
if you consider all of the massive bodies (planets, Sun) to be point
masses, you should always (with enough initial energy and direction and
proper timing) be able to create an elliptical orbit where the current
(launch) position of the projectile lies on that elliptical orbit. you
will have to sacrifice any specs regarding time, the object might return
in 100 years or 500 years or much longer.
but some of the slingshotting might have to hug some particular point
mass pretty tightly. add some non-zero radii to that planetary or solar
body and the path might bring it into the atmosphere or even below the
planet surface.
--
r b-j r...@audioimagination.com
"Imagination is more important than knowledge."
Nicolaas Vroom
Apr 2, 2013, 5:39:40 PM4/2/13
to
[[Mod. note -- I strongly concur with the author's recommendation of
http://en.wikipedia.org/wiki/Gravity_assist
as a good place to learn more about "gravitational slingshots".
-- jt]]
Op maandag 1 april 2013 21:15:13 UTC+2 schreef Chalky het volgende:
See for details: http://en.wikipedia.org/wiki/Gravity_assist
The answer on your question is yes, but only in principle.
The issue is you want to fire a rocket and then the rocket
should return all by itself to the point where it came from.
This is different than in the case of a space ship because
often additional power is used to get the spaceship
back home and that is not what you want.
I do not know if it is actual possible to have the planets
in such a position that you can visit a certain number
of planets and return back home only by using the mass of
the planets as described by Newton's Law or GR (if required)
without the use of extra power because the speed you get
should not be too large. A very tricky simulation !
However there is a subtle problem. During this whole
exercise the sun will also move in our Galaxy that means
you will not return to the point in space where you came
from.
I will not continue further in this thought experiment.
(You could also use blackholes)
However there is room for some extra thoughts.
You could also use laser light and point it towards a star
that light will be bended and can point to an other star
etc etc. finally it can hit in principle the laser gun
where it came from.
Nicolaas Vroom
http://users.pandora.be/nicvroom/
http://en.wikipedia.org/wiki/Gravity_assist
as a good place to learn more about "gravitational slingshots".
-- jt]]
Op maandag 1 april 2013 21:15:13 UTC+2 schreef Chalky het volgende:
>
> Would it be possible, in principle, to fire a projectile from
> interstellar space, such that it is returned from whence it came,
> via multiple gravitational slingshot effects?
>
The question you are asking has to do with gravity assist.
> Would it be possible, in principle, to fire a projectile from
> interstellar space, such that it is returned from whence it came,
> via multiple gravitational slingshot effects?
>
See for details: http://en.wikipedia.org/wiki/Gravity_assist
The answer on your question is yes, but only in principle.
The issue is you want to fire a rocket and then the rocket
should return all by itself to the point where it came from.
This is different than in the case of a space ship because
often additional power is used to get the spaceship
back home and that is not what you want.
I do not know if it is actual possible to have the planets
in such a position that you can visit a certain number
of planets and return back home only by using the mass of
the planets as described by Newton's Law or GR (if required)
without the use of extra power because the speed you get
should not be too large. A very tricky simulation !
However there is a subtle problem. During this whole
exercise the sun will also move in our Galaxy that means
you will not return to the point in space where you came
from.
I will not continue further in this thought experiment.
(You could also use blackholes)
However there is room for some extra thoughts.
You could also use laser light and point it towards a star
that light will be bended and can point to an other star
etc etc. finally it can hit in principle the laser gun
where it came from.
Nicolaas Vroom
http://users.pandora.be/nicvroom/
Dr J R Stockton
Apr 4, 2013, 3:15:40 AM4/4/13
to
In sci.physics.research message <28fa035b-4591-43e3-be69-cd7587907493@go
oglegroups.com>, Mon, 1 Apr 2013 20:15:13, Chalky
<chalk...@bleachboys.co.uk> posted:
>
>Would it be possible, in principle, to fire a projectile from
>interstellar space, such that it is returned from whence it came, via
>multiple gravitational slingshot effects?
>
You need to consider where from whence it came might have got to when it
comes back. In other words, its trajectory does not need to be a truly
closed curve.
The return is in principle possible in a classical Universe, but ISTM
likely that the initial aiming might have to be more accurate than
Heisenberg uncertainly would allow.
For a Galaxy approximated by randomly-placed stars of a typical
distribution of sizes, whatever that might mean, it could be of interest
to consider how the best return time might vary with the initial speed.
A faster projectile would meet stars more often, but would be deflected
less each time (those effects cancelling?); but with less possible
deflection there would be less choice of the next star.
--
(c) John Stockton, nr London, UK. Mail via homepage. Turnpike v6.05 MIME.
Web <http://www.merlyn.demon.co.uk/> - FAQqish topics, acronyms and links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.
oglegroups.com>, Mon, 1 Apr 2013 20:15:13, Chalky
<chalk...@bleachboys.co.uk> posted:
>
>Would it be possible, in principle, to fire a projectile from
>interstellar space, such that it is returned from whence it came, via
>multiple gravitational slingshot effects?
>
comes back. In other words, its trajectory does not need to be a truly
closed curve.
The return is in principle possible in a classical Universe, but ISTM
likely that the initial aiming might have to be more accurate than
Heisenberg uncertainly would allow.
For a Galaxy approximated by randomly-placed stars of a typical
distribution of sizes, whatever that might mean, it could be of interest
to consider how the best return time might vary with the initial speed.
A faster projectile would meet stars more often, but would be deflected
less each time (those effects cancelling?); but with less possible
deflection there would be less choice of the next star.
--
(c) John Stockton, nr London, UK. Mail via homepage. Turnpike v6.05 MIME.
Web <http://www.merlyn.demon.co.uk/> - FAQqish topics, acronyms and links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.
Jos Bergervoet
Apr 4, 2013, 10:42:29 AM4/4/13
to
maneuver! It did not return to where it came from
but had to stay in orbit. This is in fact more
difficult, I'd think, because it must have arrived
with about the escape velocity of Saturn's gravity.
So it had to get rid of kinetic energy.
Any encounter with a much heavier object would
change its direction, but to slow it down you need
more! You need an encounter with a heavy object
that has the right speed by itself (something in
the same order of magnitude as the probe). I assume
they used the fast moving moons of Saturn for this.
--
Jos
>
> r.y
>
Chalky
Apr 5, 2013, 1:18:17 PM4/5/13
to
On Monday, 1 April 2013 20:45:33 UTC+1, Phillip Helbig---undress to reply wrote:
> In article <28fa035b-4591-43e3...@googlegroups.com>,
>
> Chalky <chalk...@bleachboys.co.uk> writes:
>
>
>
>> Would it be possible, in principle, to fire a projectile from
>
>> interstellar space, such that it is returned from whence it came, via
>
>> multiple gravitational slingshot effects?
>
>
>
> There is no obvious reason why this could not work, at least in
>
> principle.
Firstly, I would like to thank everyone responding in this thread for
> In article <28fa035b-4591-43e3...@googlegroups.com>,
>
> Chalky <chalk...@bleachboys.co.uk> writes:
>
>
>
>> Would it be possible, in principle, to fire a projectile from
>
>> interstellar space, such that it is returned from whence it came, via
>
>> multiple gravitational slingshot effects?
>
>
>
> There is no obvious reason why this could not work, at least in
>
> principle.
appearing to confirm that my "intuitive" understanding of the physics is
correct.
>> I suspect that such a conclusion, in the affirmative, might be
>
>> inconsistent with standard GR.
>
> Why?
>> However, I do not see, as yet, how any
>
>> such an inconsistency could completely rule out the engineering of such
>
>> a possibility.
>
>
>
> So you are saying that if the possibility cannot be ruled out, then GR
>
> would be wrong if this is inconsistent with GR.
> The weak point is your
>
> claim (you have presented no evidence) that this might be inconsistent
>
> with GR. Why do you think so?
ago, but have not published (yet). This was a variant on the well known
"twin paradox" experiment. (AFAICT, my own method has not yet been
published by anyone else either, yet). Common to many such analyses is a
special relativistic outward journey, and a special relativistic return
journey, with the discrepancies between the two resolved in a general
relativistic period of subjective acceleration of the more general
twin. However, I reasoned that such direction reversal could potentially
be achieved equally well via that twin eventually encountering a series
of massive bodies, as in my aforementioned scenario.
>> I can be contacted direct as chalky at accelerators dot co dot uk, in
>
>> email format.
>
>
>
> While OK in some cases, normally questions should be answered in the
>
> group.
the moderators, as anyone else.
b...@birdband.net
Apr 5, 2013, 1:18:20 PM4/5/13
to
>
yes, they did and continue to use Titan for most maneuvers and sometimes the other moons.
gravity assist is a useful way to navigate preserving the fuel onboard.
looking for optimal ORBITAL insertion into Saturn, the scientist required this procedure
that takes longer than just sending it directly to fall into the planet.
[OT] Huygens then made a historic entry into Titan but it only survived for a blink when
it touched the surface to send the best picture EVER of another moon. some of
the scientist where impress that the probe did survive all the way down.
r.y
Tom Roberts
Apr 5, 2013, 1:18:21 PM4/5/13
to
On 4/4/13 4/4/13 9:42 AM, Jos Bergervoet wrote:
> On 4/2/2013 11:36 PM, b...@birdband.net wrote:
>> On Monday, April 1, 2013 2:15:13 PM UTC-5, Chalky wrote:
>>> Would it be possible, in principle, to fire a projectile from
>>> interstellar space, such that it is returned from whence it came, via
>>> multiple gravitational slingshot effects?
Nobody has mentioned the obvious: if you just drop it, and are close enough so
> On 4/2/2013 11:36 PM, b...@birdband.net wrote:
>> On Monday, April 1, 2013 2:15:13 PM UTC-5, Chalky wrote:
>>> Would it be possible, in principle, to fire a projectile from
>>> interstellar space, such that it is returned from whence it came, via
>>> multiple gravitational slingshot effects?
it is gravitationally bound to some star system, this will happen naturally as
it orbits. Sort of a single "gravitational slingshot". It may, of course, take a
long time to come back....
>> this type of maneuver was used to put the cassini probe in orbit with saturn.
I believe that the key maneuver is to fire thrusters near the closest approach
to the moon or planet giving gravitational assist. This gives the biggest effect
for a given amount of fuel expended. It also gives a lot more freedom to choose
where the spacecraft ends up.
Tom Roberts
Chalky
Apr 6, 2013, 5:41:54 PM4/6/13
to
[[Mod. note -- I think there may be a confusion between
(a) having a projectile depart the solar system in an outbound
*direction* (asymptotic velocity vector far from the sun)
exactly opposite to its inbound direction, versus
(b) having a projectile return to a (the same) *position* on its outbound
trajectory that it passed through on its inbound trajectory
-- jt]]
On Friday, 5 April 2013 18:18:21 UTC+1, Tom Roberts wrote:
> On 4/4/13 4/4/13 9:42 AM, Jos Bergervoet wrote:
>
> > On 4/2/2013 11:36 PM, b...@birdband.net wrote:
>
> >> On Monday, April 1, 2013 2:15:13 PM UTC-5, Chalky wrote:
>
> >>> Would it be possible, in principle, to fire a projectile from
>
> >>> interstellar space, such that it is returned from whence it came, via
>
> >>> multiple gravitational slingshot effects?
>
>
>
> Nobody has mentioned the obvious: if you just drop it, and are close enough so
>
> it is gravitationally bound to some star system, this will happen naturally as
>
> it orbits. Sort of a single "gravitational slingshot". It may, of course, take a
>
> long time to come back....
I believe I did cover this, in effect, in the third sentence of the OP.
(a) having a projectile depart the solar system in an outbound
*direction* (asymptotic velocity vector far from the sun)
exactly opposite to its inbound direction, versus
(b) having a projectile return to a (the same) *position* on its outbound
trajectory that it passed through on its inbound trajectory
-- jt]]
On Friday, 5 April 2013 18:18:21 UTC+1, Tom Roberts wrote:
> On 4/4/13 4/4/13 9:42 AM, Jos Bergervoet wrote:
>
> > On 4/2/2013 11:36 PM, b...@birdband.net wrote:
>
> >> On Monday, April 1, 2013 2:15:13 PM UTC-5, Chalky wrote:
>
> >>> Would it be possible, in principle, to fire a projectile from
>
> >>> interstellar space, such that it is returned from whence it came, via
>
> >>> multiple gravitational slingshot effects?
>
>
>
> Nobody has mentioned the obvious: if you just drop it, and are close enough so
>
> it is gravitationally bound to some star system, this will happen naturally as
>
> it orbits. Sort of a single "gravitational slingshot". It may, of course, take a
>
> long time to come back....
Nicolaas Vroom
Apr 6, 2013, 5:42:11 PM4/6/13
to
Op donderdag 4 april 2013 09:15:40 UTC+2 schreef Dr J R Stockton het volgende:
implying a truly closed curve
> The return is in principle possible in a classical Universe, but ISTM
> likely that the initial aiming might have to be more accurate than
> Heisenberg uncertainly would allow.
There is not something what is called a clasical Universe.
In this problem the Heisenberg uncertainty principle does not apply.
> For a Galaxy approximated by randomly-placed stars of a typical
> distribution of sizes, whatever that might mean, it could be of interest
> to consider how the best return time might vary with the initial speed.
> A faster projectile would meet stars more often, but would be deflected
> less each time (those effects cancelling?); but with less possible
> deflection there would be less choice of the next star.
In order to do this exercise using stars you should consider
binary stars.
Have a look at http://users.telenet.be/nicvroom/
goto the selection page and select:
Hypervelocity stars and BH's (Black Holes)
Select question 2 where Binary Stars are discussed.
Try the VB program supplied.
The reason why you should use binary stars is that the
approaching object will go to the center of the binary pair
and has a "50 %" chance of colliding with one of the stars
and a "50 %" of being ejected. (numbers arbitrary)
Is this ejected angle is 90 degrees you need 4 binary stars pairs
to return back to the origin. Those 4 pairs are positioned
at the corner of a square table.
If the initial direction is North then after the first meeting
you will go east after the second south, third west and fourth
north (if you are lucky).
The point I want to make is that starting from a random
configuration of stars does not make much sense.
(assuming only gravity is at stake)
If you want to perform the same using laser light you
should position the objects involved in a circle.
Nicolaas Vroom
http://users.pandora.be/nicvroom/
> In sci.physics.research message <28fa035b-4591-43e3-be69-cd7587907493@go
> oglegroups.com>, Mon, 1 Apr 2013 20:15:13, Chalky
> <chalk...@bleachboys.co.uk> posted:
>
> oglegroups.com>, Mon, 1 Apr 2013 20:15:13, Chalky
> <chalk...@bleachboys.co.uk> posted:
>
> You need to consider where from whence it came might have got to when it
> comes back. In other words, its trajectory does not need to be a truly
> closed curve.
The original question assumes that you return where you came from,
> comes back. In other words, its trajectory does not need to be a truly
> closed curve.
implying a truly closed curve
> The return is in principle possible in a classical Universe, but ISTM
> likely that the initial aiming might have to be more accurate than
> Heisenberg uncertainly would allow.
In this problem the Heisenberg uncertainty principle does not apply.
> For a Galaxy approximated by randomly-placed stars of a typical
> distribution of sizes, whatever that might mean, it could be of interest
> to consider how the best return time might vary with the initial speed.
> A faster projectile would meet stars more often, but would be deflected
> less each time (those effects cancelling?); but with less possible
> deflection there would be less choice of the next star.
binary stars.
Have a look at http://users.telenet.be/nicvroom/
goto the selection page and select:
Hypervelocity stars and BH's (Black Holes)
Select question 2 where Binary Stars are discussed.
Try the VB program supplied.
The reason why you should use binary stars is that the
approaching object will go to the center of the binary pair
and has a "50 %" chance of colliding with one of the stars
and a "50 %" of being ejected. (numbers arbitrary)
Is this ejected angle is 90 degrees you need 4 binary stars pairs
to return back to the origin. Those 4 pairs are positioned
at the corner of a square table.
If the initial direction is North then after the first meeting
you will go east after the second south, third west and fourth
north (if you are lucky).
The point I want to make is that starting from a random
configuration of stars does not make much sense.
(assuming only gravity is at stake)
If you want to perform the same using laser light you
should position the objects involved in a circle.
Nicolaas Vroom
http://users.pandora.be/nicvroom/
Chalky
Apr 8, 2013, 5:33:51 AM4/8/13
to
[Moderator's Note: I've reformatted this posting. Please make sure to
post in plain ASCII and with about 72 characters per line. HvH]
On Saturday, 6 April 2013 22:42:11 UTC+1, Nicolaas Vroom wrote:
>
> The original question assumes that you return where you came from,
>
> implying a truly closed curve.
No.
I describe "firing" a projectile from interstellar space. This implies
significant velocity, relative to the greneral background, in a given
direction. If I am assuming anything, it is that the projectile might
subsequently return with opposite velocity, in that direction. For
example via anticlockwise rotations through more than 180 degrees,
followed by a clockwise rotation around the last massive body.
post in plain ASCII and with about 72 characters per line. HvH]
On Saturday, 6 April 2013 22:42:11 UTC+1, Nicolaas Vroom wrote:
>
> The original question assumes that you return where you came from,
>
No.
I describe "firing" a projectile from interstellar space. This implies
significant velocity, relative to the greneral background, in a given
direction. If I am assuming anything, it is that the projectile might
subsequently return with opposite velocity, in that direction. For
example via anticlockwise rotations through more than 180 degrees,
followed by a clockwise rotation around the last massive body.
Richard D. Saam
May 1, 2013, 6:46:56 PM5/1/13
to
On 4/2/13 2:09 AM, Gerry Quinn wrote:
>
> It's no more a violation of GR (or anything else) than would be a car
> powered by a windmill managing to make progress against the wind.
>
> - Gerry Quinn
>
By itself:
>
> It's no more a violation of GR (or anything else) than would be a car
> powered by a windmill managing to make progress against the wind.
>
> - Gerry Quinn
>
"A windmill managing to make progress against the wind"
is not a valid assumption for the observed phenomenon
unless there is consideration of heat engine thermodynamics
remembering that at mid-day,
the sun provides about 1 kilowatt
on every square meter of ground
and that power may be transformed into
heat, pressure, mechanical energy, electrical
or any other form of useful energy by a suitable apparatus.
"A windmill managing to make progress against the wind"
does not work at night
just like the sun powered car.
Richard D Saam
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