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Gravity Time Mirror

Seeing our past using the sling-shot effect of a black hole's gravitational pull on light.
  (+17, -3)(+17, -3)
(+17, -3)
  [vote for,
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Using a very powerful telescope, we could look right at the very edge of a black hole where a light path made it 180degrees around the black hole due to the slingshot effect of gravitation. If the black hole were, say, 1000 light years distance from us, we would be looking back at ourselves 2000 years ago, a gravitational mirror to the past.
BruceRH90, Dec 03 2004

TimeCube! http://www.timecube.com/
Utterly unlike the above: "There's no human entity, only corner Cubics, rotating life's 4 corner stage metamorphosis." [Trout, Dec 03 2004]

Black holes are dark energy stars http://www.nature.c.../full/050328-8.html
[JesusHChrist, Apr 05 2005]

[link]






       Okay.   

       Here it goes.   

       Are you saying that we could look at the light that goes into a black hole at a such angle that the gravity(it didn't get inside the event horizon, just barely) pulls it around and heads it back in the direction it came?   

       Could work with extremely highly advance stuff, but you'd need filters for all of the other light heading towards you, and the light has to head to where the black hole will be in 1000 years, and then return to where the earth would be in 2000 years.   

       Yes, light could actually do this, but no, we would have to wait milleniums and millions of years before we have sufficient technology to do this.
DesertFox, Dec 03 2004
  

       More to the point, it wouldn't be possible to view anything with any detail - keep in mind that intensity decreases as a function of the square of the distance from earth to the black hole, divided by two...the light would be very dim, and in poor resolution.   

       It would be possible to view our position and the positions of heavenly bodies, but that's about all we'd get out of it.   

       (+-)
shapu, Dec 03 2004
  

       Actually, the place to look for a 180 degree photon is not at the edge of the event horizon, but somewhat further out (3/2 radii). A + for the idea.
ldischler, Dec 03 2004
  

       If you took a number of massive bodies (or found a suitable arrangement of them) you might be able to provide better resolution and focus.   

       The relative movements of ourselves and the gravity lens would be very difficult to take into consideration, assuming you wanted a magnified image (which you'd need to since things 1000 light-years away are mere specks of light anyway, even under the largest magnification available to us now)
zen_tom, Dec 03 2004
  

       [+] for you! Especially because when I saw the title I was expecting something more like TimeCube (q.v.).
Trout, Dec 03 2004
  

       That link scares me.   

       Everybody's gotta have a hobby......I'm glad his [the link] isn't halfbaking.
normzone, Dec 04 2004
  

       WOW! - Top Link [Trout]. The Man, he scare me with Jesus Sun Up, Clinton Mid Day.
Human form is a Personified Pyramid.
gnomethang, Dec 04 2004
  

       Wouldn't this work for any mass? This should be happening to whatever miniscule degree around even the moon, shouldn't it? If you could coordinate information coming back from lots of different sources you could have a sort of time machine.
JesusHChrist, Mar 26 2005
  

       The complete slingshot effect only occurs near, as [ldischler] points out, a distance 3/2 times the Schwarschild radius from the centre of the mass. If the Schwarschild radius (or, rather, 3/2 of it) is "inside" the spatial extent of the object - as it is with the moon - then it doesn't really describe anything physically interesting and you won't see this.
Detly, Mar 26 2005
  

       I will wager $10,000 that the Cubic Creation is a load of old cobblers.   

       And I thought [Detly] was unhinged.
wagster, Mar 26 2005
  

       [Detly] I'm not sure I understand. I thought things like the Eyeinstiyne's cross happen when there in something very heavy between us and them - but that for us to see the doubling the light has to sort of give the heavy object a reasonably wide berth, on either side, so that it can be bent in our direction and look like two things -- so some light must be getting bent not at the Swartzchild radius but further out. So wouldn't that mean that any mass at all bends light a little bit?
JesusHChrist, Mar 26 2005
  

       Pssssstttt. JHC, it's Einstein, not Einstine.
DesertFox, Mar 26 2005
  

       Brilliant! I wonder also if you couldn't use reflected light from a regular object? Given that reflective objects (dust, planets) are presumably more abundant than black holes, there should be more earth-originating light returning to earth by reflection than by gravitational back-bending. You'd have to do all kinds of weird stuff to correct for the angle and distance of the reflecting surface at the time the photon hit it (and also its radial velocity, I guess - redshifts an' all), but I think the problems you'd have to solve are in principle no different from those in the black-hole-slingshot idea. Basically, you need a technology that can collect incoming photons and figure out which direction their coming from and how long they took. A starting point would be to reconstruct an image of earth a few seconds old, from light reflected from the surface of the moon. Some WIBNIsh elements, but no more than many halfbaked ideas. Bun.
Basepair, Mar 26 2005
  

       [JHC] any mass deflects light, but not by 180 degrees until you get closer in - maybe I didn't understand what you meant in your original anno.
Detly, Mar 29 2005
  

       [Detly] I guess I'm thinking that, since all mass bends light a little bit, the moon is really bending all the light in the sky a little bit (from my perspective) towards it -- even the light coming almost straight at the back of my head -- and that the bendingness gets stronger the closer you get to the moon (from my perspective, and since this sets up a curve that increases increasiingly toward the moon, that that curve must go up asymptotically at some really microscopically close degree to the edge of the moon. I guess another way to say it would be that the moon must be bending the already bent light the closer you get to it so by the time you get really really close it is bending the bent light that was already bent to the nth degree sort of. Ok now I'm going to hit OK and read this and it is not going to make any sense.
JesusHChrist, Mar 29 2005
  

       //that that curve must go up asymptotically at some really microscopically close degree to the edge of the moon//   

       No - it would simply reach some finite value, because the spatial extent of the moon is larger than the magic radius.
Detly, Mar 29 2005
  

       damn
JesusHChrist, Mar 29 2005
  

       How do you know there isn't one?   

       (+)
moomintroll, Mar 30 2005
  

       It may be that the gravity of local bodies is not enough to pull the light in the full 180 degrees. It might be necessary to bank the light around several large objects to get the correct amount of bend. This would require some fancy math. Alternatively, it could be done empirically, with a powerful laser pulsing a recognizable pattern. You could fire your pulses with the calculated angle / alignment of stars and planets, then watch for the return pulse, which should be detectable by telescope.   

       The same laser theory could be used with a black hole. In fact, just spraying the black hole with the laser then watching for the return would be the quick and dirty way to do this. Although this would be sloppy pool - really you should have to call your shots.
bungston, Mar 30 2005
  

       Or you could look near a black hole for the bent light from a known nova -- which would be easier to find than light coming right back from you, and calibrate first using that.
JesusHChrist, Mar 31 2005
  

       Would you still know it once it had been bent? Will you still love it in the morning?
bungston, Mar 31 2005
  

       [Bungston] The problems with calibrating the system in the ways you describe are (a) if you want to calibrate a system that's giving you 5000-year- old images, you're going to have to wait 5000 years for the calibration data to return and (b) things move; your calibration would have to be dynamic.
Basepair, Mar 31 2005
  

       Thats why to look for a nova that you know occurred longer ago than the number of lightyears to the black hole but less than twice that long.
JesusHChrist, Mar 31 2005
  

       Not sure I follow, JHC, but I may be being dim here. But you're going to need a continuous succession of supernovas (if you use them for calibration), since all the components of the system will be moving. The calibration you apply at one instant won't work a few moments later.
Basepair, Mar 31 2005
  

       [Detly] //No - it would simply reach some finite value, because the spatial extent of the moon is larger than the magic radius.//   

       When you look at the edge of the moon you see all the light that has been bent by the moon. This includes light coming directly from objects and also light that has been bent by the gravity of those objects. Within the light that has been bent by those objects will be light that has been bent by objects behind them and so on. The bent light includes light that originally came from you. All you need is a powerful telescope and a sorting algorithm.
JesusHChrist, Apr 03 2005
  

       Theoretically true, but the bending would be so weak, and the light so scattered, any signal would be incredibly weak and swamped with noise.
Detly, Apr 04 2005
  

       If there were a black hole that lay between a pulsar and earth, one should be able to detect a bent pulsar signal coming from the black hole as a result of bending.
bungston, Apr 04 2005
  

       It is strange how light has no mass, yet travels at superspeeds, can be affected by gravity (even though it has no mass!!), and doesn't even deliver it's inertia to an object when it comes in contact with it. But you can't have inertia unless you have mass. Yet it is still affected by gravity.
EvilPickels, Apr 05 2005
  

       “Mass grips space by telling it how to curve, space grips mass by telling it how to move.” - John Wheeler.   

       "Light just zips around looking good". - Bungston.
bungston, Apr 05 2005
  

       Very interesting idea and annos and extremely half baked. Which got me thinking.....   

       Theoretically, with good enough resolution, and assuming it wasn't cloudy that day, and that the earth was facing the black hole at the time, we could look back and see JesusHCrist (the original) on the sermon on the mount, and even see what he had to say if we can lip read from the top of the head. That might settle a few things, and stir up a lot more.
sophocles, Apr 05 2005
  

       Presumably, he'd be saying something like "Gee, Dad told me about the heavens and the earth bit, but who the hell made that black hole?"
Basepair, Apr 05 2005
  

       Ok, call me totally insane but here's my theory. All you have to do to see this effect is... squint... really patiently for a long time, and look for patterns in the rainbows in your eyelashes. I saw this one day while I was playing around with a jewlers loupe and a toy microscope, pressing them up to my eye and looking at the rainbows in the refracted light for a really long time -- I saw a scene that looked like it was from a movie, except that I could make it go forward or backward in time by moving my hands incrementally. It was sort of unsettling because it told me that what I was seeing was something my head was doing to the light and not something out there in the real world.   

       So, one completely halfbaked explanation for this would be that, if all light includes information that has been bent back to its origin by all the local massive objects in the sky, that information can be extracted by a really powerful telescope (your eyelashes, a jewlers loupe and a toy microscope working together), and sorted by a really powerful computer (your brain).
JesusHChrist, Apr 06 2005
  

       JHC: Sounds like you're now totally baked.... :)
sophocles, Apr 06 2005
  

       [EvilPickels] - light carries momentum and energy. Any distribution of energy - whether it be in the form of rest mass or otherwise - and momentum is affected by the curvature of space; this curvature of space is produced by the distribution of energy and momentum.   

       Light does deliver momentum upon being absorbed by matter. It is not that light has no (rest) mass; it is that the concept of rest mass does not make sense when applied to a photon, as there is no reference frame, inertial or otherwise, in which it appears at rest. The rest mass can therefore not be measured.
Detly, Apr 06 2005
  

       [JHC]//Ok, call me totally insane//

You are totally insane.
Basepair, Apr 06 2005
  

       That the powers of resolution and computation to retrieve any intelligible amount of infomation from the flattened focused waves of light whipping around a black hole are out of the reach of all but god is not my concern. I want it bad, this black hole capitalism.
daseva, Apr 07 2005
  

       I fought the space-time continuum, and the space-time continuum woo o o o o o... .. .
Detly, Apr 08 2005
  

       I was pondering a more plausible variation on this idea, which may actually be partially baked. Consider an optical telescope lens: it pulls divergent rays of light together to form a large image of something far away.   

       A black hole could be used for this. Divergent light from an object on the far side of the black hole should be pulled together to converge into an image. Different gravitational strengths would have different effective focal lengths. The image produced might overlap with the black hole, and so it is good that they do not radiate themselves. This could be used to find distant planets.
bungston, Apr 19 2006
  
      
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