h a l f b a k e r y"My only concern is that it wouldn't work, which I see as a problem."
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This carefully prepared time capsule would be launched
tangentially across the galaxy, intended to reach earth in a
hundred million years on the other side.
Obviously
careful planning and great expense would be required to let
it
maintain course for that long, and that's kind of the
point.
Chord of a circle
http://www.mathopenref.com/chord.html
As mentioned in an annotation [Vernon, Feb 20 2013]
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When you say 'tangentially', do you mean
'tangentially'? And if so, in which direction (ie, in
the same direction that we are travelling, or
directly opposite to that)? |
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If you are launching it tangentially forward (ie, in
the same direction as we are going), then it will
have to travel with the same velocity as we are,
which means it'll be right next to us for the next
100 million years, and therefore not much of a
surprise. |
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If you are launching it tangentially backward (ie,
opposite to the direction we are going), then it'll
have to be given an equal and opposite velocity to
us. Sadly, that means we will encounter it on the
opposite side of the galaxy with a closing speed of
about 972,000 miles per hour. We're gonna need a
bigger catcher's mitten. |
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I believe Voice means to launch it directly, straight across the galaxy on the same plane as our solar system's orbit around the galaxy. That presents a few problems, but mostly that it would take quite a bit of thrust. |
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There seems to be a large mass in the way of that
route. |
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Given current technology, in both propulsion and the science of knowing where things are that we cannot see in any way, I suspect that 100 million years, even 100 million tries over 100 million years might still fail to result in a singe successful return using this technique.
I'm going to go out on a limb here and suggest that even if we mined the earth into as many pieces as we could and fired them out at a rate of one hundred million a year for as many years as we could sustain that, that not even one piece would end up passing through the galaxy again by the "across to the far side and back, path". That even if you scattershot the entire galaxy in the form of small high speed pellets not a one of them would return to pass through the galactic orbit. |
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//I believe Voice means to launch it directly,
straight across the galaxy//
Ah, so he means
"tangentially" in the sense of "in
the direction as different from being tangential as
it
is possible to get". Silly me. |
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//even if we mined the earth into as many pieces
as we could and fired them out at a rate of one
hundred million a year for as many years as we
could sustain that, that not even one piece would
end up passing through the galaxy again//
Well,
perhaps we could start with Wales and see how it
works out. |
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You are all quibbling over details related to the just the trajectory. |
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More feasible would be to send it on a path that did a close fly-by near the 2 or 3 nearest stars such that it eventually returned home after 100 million years. This also resolves problems related to fast interstellar travel, like impossible propulsion issues and erosion caused by relativistic interstellar micrometeorites and gasses. |
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Of course, then the technology in it might be used to humanities detriment by the damned dirty apes. |
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//What the hell is with all the Welsh bashing ?//
Your honour, I may I call my first witness, [8th of
7] to the stand. |
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//a close fly-by near the 2 or 3 nearest stars such
that it eventually returned home after 100 million
years// |
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Wouldn't it just be simpler to hide it behind the
sofa
for the 100 million years? Or, if it contained cash,
pop it in a building society? |
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//What the hell is with all the Welsh bashing ?// |
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Well, it's not like they're going to be bothered by it,
seeing as they haven't got the Internet there yet. |
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//they haven't got the Internet there yet.// |
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That's a little harsh. A printout of the internet is
sent by mail train to Wales twice a week. |
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Well, what good is /that/ going to do them? Or is it
accompanied by someone to read it out loud? |
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I do believe the appropriate descriptive word is "chord", not "tangent". |
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You could consider sending the capsule across the galactic disk slightly differently than exactly through it. There is always "over the disk" or "under the disk". And in terms of parabolic trajectories, what with there being quite a significant attracting mass in the middle of the disk, it seems to me to be quite theoretically feasible. |
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In practice, of course, you still have to deal with the fact that the Sun is going around the galactic center at a speed/direction combination that you don't want to include in the capsule's proposed parabolic passage. Quite a bit of energy will be needed to get that capsule on the correct course. |
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And at the end of the trip, the same amount of energy will be needed to make the capsule match course and velocity with the solar system.... |
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"Wouldn't it just be simpler to hide it behind the sofa for the 100 million years? Or, if it contained cash, pop it in a building society?
— MaxwellBuchanan, Feb 20 2013" |
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As an outsider to the UK's current dynamic of internal
geopolitical disdain, my opinion may not be valid, but I
would stand behind a campaign to eliminate Welsh-bashing
by promoting strong dislike of the French, or failing that
then at least having a good sneer at residents of the Inner
Hebrides. |
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I'm trying to think of an analogy.... no earthly scale is appropriate. Imagine however that we consider just the fate of our most elegant and rapid projectile, the photon of light. No other projectile has better chances, none is cheaper or faster, none can be launched in greater numbers, and yet even so, given a beam of them lased into space we could not expect to hit the mark, the distance and interference in such a journey is impossible to overcome. The echos of our radiation never return to us from the other side even though by the merits of the properties of space they should. |
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// The echos of our radiation never return to us from the
other side even though by the merits of the properties of
space they should. // |
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You've got it on backwards: 'by the merits of the properties
of
space', which I assume means 'according to the laws of
physics', the reflection of our own radiation obviously
_shouldn't_ return to us, because it doesn't. |
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If we sent the probe on the best trajectory we could calculate, then in 90 million years we could start transmitting a homing signal from earth and the probe could guide itself in. If you could make the probe go fast enough it would only need to have a power source that lasted about 12 years, not 100 million, due to relativistic effects. Again, the thrust required for this would be considerable (like an antimatter drive firing continuously for decades). |
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If it was going that fast, it would be beyond escape velocity and not come back. |
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Well, maybe... if you set it up to do a very tight slingshot around the black hole at the center of the galaxy. But it's going to be downright un-neighborly if your device pashes into somebody's home planet along the way. |
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But - more to the idea - what would we want to communicate to someone that far in the future? Or, to look at it the other way - say our progenitors of, say, a million years ago had found a way to send us a message, would we be impressed? Interested? Amused? |
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"by geometry, yes, but by all other sciences, no." |
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In the incredibly bad movie _Starship_Troopers_, the bad aliens were sending asteroids clear across the galaxy and hitting targets. And somehow having the asteroids drift in very slowly. |
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That wasn't the worst thing about the movie. Sadly. |
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The worst thing about the movie was handing one of
Heinlein's most interesting and original novels to the
director of 'Showgirls'. |
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There could have been way more toplessness for one
thing. |
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//If it was going that fast, it would be beyond escape velocity and not come back.// The idea isn't for it to loop around, the idea is for it to meet Earth on the other side of the galaxy when our solar system finally makes its way over there. The speed of the probe would need to average about 1/4 of the speed of our solar system in order to meet it there. |
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There actually WAS a little toplessness in that movie, probably not included in the original book. Probably the best thing about the whole movie, aside from the mercy of Heinlein dying before the movie was made. |
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The 'toplessness' in the book came in the form of an
advanced and (in some ways) more enlightened human
soceity free from hidebound prudery and openness to
sexuality. In the film this was interpreted as a free ticket
to a gratuitous communal shower scene. |
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Considering that the average species lasts about 4
million years, and that we've been around for around
40,000-100,000 years (of which we've only been able
to send and receive radio signals for about 100 years)
I would think it highly unlikely anyone would be
around in 100,000 years to read our ancient Digital
Age messages, let alone 100M years from now. |
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My sofa just got launched tangentially to Earth's orbit at exactly Earth's speed. I guess that's why it just sits there in my living room. I blame Newton. |
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Actually, if it were launched tangentially to Earth's
orbit, it would not be staying put. However, you
would re-encounter it 24hrs later. |
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This might be a bit difficult, how about just
launching a time capsule that travels alongside
Haley's comet (or some other comet) then splits off
and lands at some pre-determined spot when it
returns? |
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Anyway, brilliant concept. [+] |
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