13 ms·

Gravitational Lensing to Observe Ancient Earth

137 points by pinko 12y ago

3327 12y ago
I've spent a good amount of engineering hours doing research on this thought when I had it in the shower a few years back. My thought was a little different in that : " perhaps we could beam a laser with encoded information on a loop journey, that is meant to return to earth in X million years." Such a trajectory might also depend on the position of earth and other objects and have a very narrow windows. As if watching a pond on a windy day and the wind eases off for a second or two yielding a glimpse of your own reflection and then to pick up again leaving a blurry pond.
- gue5t 12y ago
  For the digital-network analogue, see pingfs: http://www.shysecurity.com/posts/PingFS http://www.shysecurity.com/posts/PingFS
  - tbrownaw 12y ago
    http://en.wikipedia.org/wiki/Delay_line_memory http://en.wikipedia.org/wiki/Delay_line_memory
rcthompson 12y ago
So it's possible for a beam of light to wrap around a black hole and intersect its own path. This must mean that light doesn't follow Kepler orbits[1] in general relativity? [1] i.e. ellipse, parabola, or hyperbola: http://en.wikipedia.org/wiki/Kepler_orbit http://en.wikipedia.org/wiki/Kepler_orbit
- pdonis 12y ago
  > This must mean that light doesn't follow Kepler orbits[1] in general relativity? That's right. This is true even in the weak field limit: the orbits of planets in the Solar System are not exact ellipses when GR is taken into account. This is called "perihelion precession", and was observed with Mercury even in the 19th century; it was one of the "classic tests" that Einstein calculated to satisfy himself that GR was correct. With modern observations I believe this effect has been observed for at least all of the inner planets (Mercury, Venus, Earth, and Mars).
  - rcthompson 12y ago
    I see, so GR causes all orbits to precess, and actually nothing follows classical Kepler orbits exactly. Even the simple two-body problem doesn't result in elliptical orbits. http://en.wikipedia.org/wiki/Two-body_problem_in_general_relativity http://en.wikipedia.org/wiki/Two-body_problem_in_general_rel...
    - pdonis 12y ago
      Yes. (Strictly speaking, a perfectly circular orbit would qualify as a "classical Kepler orbit", and is still possible in GR, but this is an idealized case.)
jkot 12y ago
There is a lot of exiting stuff: observing Einstein cross visually, GAI mapping mission, MACHO detection... Perhaps we could start with that...
- privong 12y ago
  > There is a lot of exiting stuff: observing Einstein cross visually, GAI mapping mission, MACHO detection... Perhaps we could start with that... I am not sure what you mean. We have had optical observations of at least one Einsten cross since the late 80s / early 90s[0, 1]. Signs of MACHOs were detected in 1995[2]. I don't know what a "GAI mapping mission" is, so I cannot comment on that. [0] http://adsabs.harvard.edu/abs/1993BCFHT..29...22H http://adsabs.harvard.edu/abs/1993BCFHT..29...22H [1] http://arxiv.org/abs/astro-ph/9512103 http://arxiv.org/abs/astro-ph/9512103 [2] http://www.aps.org/publications/apsnews/199507/macho.cfm http://www.aps.org/publications/apsnews/199507/macho.cfm
ComputerGuru 12y ago
Reminds me of one of my favorite books (well, not really. The premise was incredible and the writing was impeccable but it was part one of a trilogy that never materialized): Pastwatch: The Redemption of Christopher Columbus It was basically a brilliant alternative historical fiction novel based around the premise of being able to rewatch the past.
- hawkice 12y ago
  I consider it the best science fiction book for people who are interested in historical fiction and speculative historical fiction. Longest list of citations for a fiction book I've ever seen. And as you say, excellent premise.
sixQuarks 12y ago
This is what's so crazy about technology. Whatever we can imagine, we can make happen, no matter how crazy it sounds. Our descendants 1,000 years from now will probably be able to observe everything we are doing today. If you asked me how yesterday, I wouldn't have a clue. But today, this article shows me one way to do it. Imagine the other possibilities yet to be discovered.
- deleted 12y ago
  [deleted]
- jcoffland 12y ago
  This is a common view point which kind of irritates me. It leads to a lot of false assumptions and gullibility with regards to pop science. What about time travel, teleportation or travel to the nearest star system? All things well with in reach of our imagination and far from our ability.
  - k__ 12y ago
    I don't think it is impossible per se, but we put our time and resources in other things, so it won't happen.
    - jcoffland 12y ago
      We will see none of these things in our lifetime nor is it likely to happen in the next 1000 years. I challenge you to read up on what it would take to reach Proxima Centauri. Small amounts of time travel happen all the time. Significant forward time travel is physically possible, as is interstellar travel, but unobtainable by humans. Pop science has tried to make us think teleportation is possible through quantum entanglement but that has been proven false. I would love it if we could do any of these things but it's just not reasonable to think it will happen. I believe this sort of gullibility stems from not really understanding what we have achieved. If our current achievements seem like magic then anything seems possible. Mankind's achievements are impressive to mankind but we're also a bunch of self-aggrandizing egotists. Hopefully no one else is watching. http://earthsky.org/space/alpha-centauri-travel-time http://earthsky.org/space/alpha-centauri-travel-time
intrasight 12y ago
I've a different idea. Rather than try to recover old photons that left earth long ago, can recover and collate the remnants of these photons. This might be possible if these photons left a holographic imprint on matter which is still present – buildings, old trees, rock formations. I envision that in the future there will be a field of "photonic archaeology" where scientists will reconstruct past images from these trace holographic signatures. Same thing could theoretically be done for acoustics.
- davmre 12y ago
  Godel Escher Bach has a chapter riffing on the acoustics version of this idea: http://www.facstaff.bucknell.edu/jvt002/BrainMind/Readings/Prelude.pdf http://www.facstaff.bucknell.edu/jvt002/BrainMind/Readings/P.... Though the discussion there is about recovering sound waves that are still propagating in the air, which seems orders of magnitude more difficult than recovering sound from impressions on solid objects (which already feels likely impossible in most interesting cases).
  - adamio 12y ago
    Reminds me of this http://newsoffice.mit.edu/2014/algorithm-recovers-speech-from-vibrations-0804 http://newsoffice.mit.edu/2014/algorithm-recovers-speech-fro...
- pdonis 12y ago
  > This might be possible if these photons left a holographic imprint on matter which is still present How would that happen? Holographic imprints aren't left on just any old material; you need special film to make a hologram.
- dubya 12y ago
  There was an X-Files episode with this idea. Something Jesus said ("Talitha cumi") was recorded in a piece of pottery.
jimmcslim 12y ago
Assuming we could overcome the technological/scientific/physical limitations and we did have a 'realtime' video feed from a Google Earth-like perspective of events happening 65 years ago (picking the final example)... I wonder what the societal impacts of that would be?
- chernevik 12y ago
  For one thing we might be able to measure the polar ice caps -- I don't know how far back our current data go, but I don't think they go back to 1950. Maybe spectronomy (?) could tell us something about the proportion of greenhouse gases. If the telescopes had adequate resolution, we might be able to measure the size of cities over time. Images from 1950 forward might give us data on the progress of city growth and electrification by observing the spread of night-time illumination. It's fantastic to imagine similar data going back centuries or millenia. It would be remarkable to chart the growth of Rome, London, Delhi, Beijing over time, or perhaps gather demographic data on the spread of the "barbarians". Or track the agricultural and demographic history of Egypt by watching the spread of cultivated land around the Nile delta. Or gather data on the history of trade routes like the Silk Road by observing the growth of towns along them. We might track the history of the Black Plague by observing the shrinkage of cultivated land, and the pause in the growth of urban centers. We might learn a lot of climate science by gathering data on the explosion of Krakatoa and the subsequent effects on the polar ice caps. We might gather data on the emergence and spread of agriculture from pre-history by observing transformation of forest land into farmland, and the appearance of greenery in places supportable only by irrigation. You might tell the story of the Tigris and the Euphrates that way. Of course, all of that depends on spectacular levels of resolution. And those would have to grow as we looked back further in time, because the lensed light would appear that much further away. I suppose most of what I've listed here could easily be outside any plausible resolution. I guess I imagine that some of climate science stuff might be dreamt of. But what a thing to think of!
- EGreg 12y ago
  I would first of all want to check if any religion's historical claims are true. That would help a lot of people with their beliefs!
scarygliders 12y ago
This reminded me of a short story I read, called Light Of Other Days, written by Bob Shaw. Instead of black holes or other massive objects, he used a concept called "slow glass" - glass in which light takes years to pass. Obviously, though, you'd had to have panes of slow glass in front of the scenes from life 6000 years ago...
- jcoffland 12y ago
  "Light of Other Days" is a great book but it was written by Stephen Baxter and Arthur C. Clarke.
  - jcoffland 12y ago
    Wait, sorry. There are two books with similar titles. "The Light of Other Days" is by Stephen Baxter and Arthur C. Clarke. "Light of Other Days" is indeed by Bob Shaw. I have not read the latter. The former deals with a new technology which allows people to see in to the past via microscopic "wormholes".
- davyjones 12y ago
  This was one of the first works I read that changed my perspective to focus on the human elements in science fiction as opposed to the bells and whistles.
mulligan 12y ago
This article from berkeley is super relevant, it was published just a few days ago: https://newscenter.berkeley.edu/2015/03/05/distant-supernova-split-four-ways-by-gravitational-lens/ https://newscenter.berkeley.edu/2015/03/05/distant-supernova... We can see a supernova 4 different times using gravitational lensing.
dghughes 12y ago
Imagine if everything in the Universe was just the light from our solar system refracted billions of ways making it seem like there were galaxies but really we are all alone.
chrischen 12y ago
I am not a lawyer, but maybe if multiple MACHOs in the right positions could make this work.
Intermernet 12y ago
>In 2002 Daniel Holz and John Wheeler investigated this idea and ran all the calculations in their paper Retro-MACHOs: Pi in the Sky? That's one of the best paper names I've come across. From the introduction: >The bending power of a black hole is not limited, however, to small angles but reaches π and odd multiples of π. Illuminated by a powerful point source of light, the black hole will therefore shine back with a series of concentric rings (we call this retrolensing). Does anyone know if this sort of research is on the agenda for the James Webb Space Telescope? Our space imaging has progressed dramatically in the last couple of decades, so it wouldn't surprise me to see many more MACHOs (maybe even Retro-MACHOs!) being discovered, in the same way our understanding of the vast number of galaxies in the universe was increased by the Hubble Space Telescope.
mehwoot 12y ago
Is there any calculation on what resolution would be even theoretically possible? There are only a finite number of photons being emitted by the surface of the earth and so at a certain distance there wouldn't be enough to show detail past some level.
nether 12y ago
Would we ever be able to collect enough photons to form any kind of image though?
cake93 12y ago
How would the calculations play out for near-earth MACHOs and radio frequencies instead of visible light? I can imagine that the construction of a suitable antenna is more feasible than for a visible-light telescope?
bsurmanski 12y ago
Coincidentally, something like this was asked on reddit.com/r/askscience recently. http://www.reddit.com/r/askscience/comments/2y93cz/if_we_were_far_enough_from_earth_could_we_see_the/ http://www.reddit.com/r/askscience/comments/2y93cz/if_we_wer... (if we were far enough from the earth, could we see the dinosaurs) One comment claimed that the lens would be the limiting factor. If using traditional glass lens, they calculated that it would need a diameter of 4 light years to be able to see the dinosaurs. They furthermore claimed that a lens of this size would gravitationally collapse, and thus would not be feasible. I don't believe gravitational lensing was mentioned as of my reading.

137 points by pinko 12y ago

3327 12y ago

I've spent a good amount of engineering hours doing research on this thought when I had it in the shower a few years back. My thought was a little different in that : " perhaps we could beam a laser with encoded information on a loop journey, that is meant to return to earth in X million years." Such a trajectory might also depend on the position of earth and other objects and have a very narrow windows. As if watching a pond on a windy day and the wind eases off for a second or two yielding a glimpse of your own reflection and then to pick up again leaving a blurry pond.

gue5t 12y ago
For the digital-network analogue, see pingfs: http://www.shysecurity.com/posts/PingFS http://www.shysecurity.com/posts/PingFS
- tbrownaw 12y ago
  http://en.wikipedia.org/wiki/Delay_line_memory http://en.wikipedia.org/wiki/Delay_line_memory

rcthompson 12y ago

So it's possible for a beam of light to wrap around a black hole and intersect its own path. This must mean that light doesn't follow Kepler orbits[1] in general relativity? [1] i.e. ellipse, parabola, or hyperbola: http://en.wikipedia.org/wiki/Kepler_orbit http://en.wikipedia.org/wiki/Kepler_orbit

pdonis 12y ago
> This must mean that light doesn't follow Kepler orbits[1] in general relativity? That's right. This is true even in the weak field limit: the orbits of planets in the Solar System are not exact ellipses when GR is taken into account. This is called "perihelion precession", and was observed with Mercury even in the 19th century; it was one of the "classic tests" that Einstein calculated to satisfy himself that GR was correct. With modern observations I believe this effect has been observed for at least all of the inner planets (Mercury, Venus, Earth, and Mars).
- rcthompson 12y ago
  I see, so GR causes all orbits to precess, and actually nothing follows classical Kepler orbits exactly. Even the simple two-body problem doesn't result in elliptical orbits. http://en.wikipedia.org/wiki/Two-body_problem_in_general_relativity http://en.wikipedia.org/wiki/Two-body_problem_in_general_rel...
  - pdonis 12y ago
    Yes. (Strictly speaking, a perfectly circular orbit would qualify as a "classical Kepler orbit", and is still possible in GR, but this is an idealized case.)

jkot 12y ago

There is a lot of exiting stuff: observing Einstein cross visually, GAI mapping mission, MACHO detection... Perhaps we could start with that...

privong 12y ago
> There is a lot of exiting stuff: observing Einstein cross visually, GAI mapping mission, MACHO detection... Perhaps we could start with that... I am not sure what you mean. We have had optical observations of at least one Einsten cross since the late 80s / early 90s[0, 1]. Signs of MACHOs were detected in 1995[2]. I don't know what a "GAI mapping mission" is, so I cannot comment on that. [0] http://adsabs.harvard.edu/abs/1993BCFHT..29...22H http://adsabs.harvard.edu/abs/1993BCFHT..29...22H [1] http://arxiv.org/abs/astro-ph/9512103 http://arxiv.org/abs/astro-ph/9512103 [2] http://www.aps.org/publications/apsnews/199507/macho.cfm http://www.aps.org/publications/apsnews/199507/macho.cfm

ComputerGuru 12y ago

Reminds me of one of my favorite books (well, not really. The premise was incredible and the writing was impeccable but it was part one of a trilogy that never materialized): Pastwatch: The Redemption of Christopher Columbus It was basically a brilliant alternative historical fiction novel based around the premise of being able to rewatch the past.

hawkice 12y ago
I consider it the best science fiction book for people who are interested in historical fiction and speculative historical fiction. Longest list of citations for a fiction book I've ever seen. And as you say, excellent premise.

sixQuarks 12y ago

This is what's so crazy about technology. Whatever we can imagine, we can make happen, no matter how crazy it sounds. Our descendants 1,000 years from now will probably be able to observe everything we are doing today. If you asked me how yesterday, I wouldn't have a clue. But today, this article shows me one way to do it. Imagine the other possibilities yet to be discovered.

deleted 12y ago
[deleted]
jcoffland 12y ago
This is a common view point which kind of irritates me. It leads to a lot of false assumptions and gullibility with regards to pop science. What about time travel, teleportation or travel to the nearest star system? All things well with in reach of our imagination and far from our ability.
- k__ 12y ago
  I don't think it is impossible per se, but we put our time and resources in other things, so it won't happen.
  - jcoffland 12y ago
    We will see none of these things in our lifetime nor is it likely to happen in the next 1000 years. I challenge you to read up on what it would take to reach Proxima Centauri. Small amounts of time travel happen all the time. Significant forward time travel is physically possible, as is interstellar travel, but unobtainable by humans. Pop science has tried to make us think teleportation is possible through quantum entanglement but that has been proven false. I would love it if we could do any of these things but it's just not reasonable to think it will happen. I believe this sort of gullibility stems from not really understanding what we have achieved. If our current achievements seem like magic then anything seems possible. Mankind's achievements are impressive to mankind but we're also a bunch of self-aggrandizing egotists. Hopefully no one else is watching. http://earthsky.org/space/alpha-centauri-travel-time http://earthsky.org/space/alpha-centauri-travel-time

intrasight 12y ago

I've a different idea. Rather than try to recover old photons that left earth long ago, can recover and collate the remnants of these photons. This might be possible if these photons left a holographic imprint on matter which is still present – buildings, old trees, rock formations. I envision that in the future there will be a field of "photonic archaeology" where scientists will reconstruct past images from these trace holographic signatures. Same thing could theoretically be done for acoustics.

davmre 12y ago
Godel Escher Bach has a chapter riffing on the acoustics version of this idea: http://www.facstaff.bucknell.edu/jvt002/BrainMind/Readings/Prelude.pdf http://www.facstaff.bucknell.edu/jvt002/BrainMind/Readings/P.... Though the discussion there is about recovering sound waves that are still propagating in the air, which seems orders of magnitude more difficult than recovering sound from impressions on solid objects (which already feels likely impossible in most interesting cases).
- adamio 12y ago
  Reminds me of this http://newsoffice.mit.edu/2014/algorithm-recovers-speech-from-vibrations-0804 http://newsoffice.mit.edu/2014/algorithm-recovers-speech-fro...
pdonis 12y ago
> This might be possible if these photons left a holographic imprint on matter which is still present How would that happen? Holographic imprints aren't left on just any old material; you need special film to make a hologram.
dubya 12y ago
There was an X-Files episode with this idea. Something Jesus said ("Talitha cumi") was recorded in a piece of pottery.

jimmcslim 12y ago

Assuming we could overcome the technological/scientific/physical limitations and we did have a 'realtime' video feed from a Google Earth-like perspective of events happening 65 years ago (picking the final example)... I wonder what the societal impacts of that would be?

chernevik 12y ago
For one thing we might be able to measure the polar ice caps -- I don't know how far back our current data go, but I don't think they go back to 1950. Maybe spectronomy (?) could tell us something about the proportion of greenhouse gases. If the telescopes had adequate resolution, we might be able to measure the size of cities over time. Images from 1950 forward might give us data on the progress of city growth and electrification by observing the spread of night-time illumination. It's fantastic to imagine similar data going back centuries or millenia. It would be remarkable to chart the growth of Rome, London, Delhi, Beijing over time, or perhaps gather demographic data on the spread of the "barbarians". Or track the agricultural and demographic history of Egypt by watching the spread of cultivated land around the Nile delta. Or gather data on the history of trade routes like the Silk Road by observing the growth of towns along them. We might track the history of the Black Plague by observing the shrinkage of cultivated land, and the pause in the growth of urban centers. We might learn a lot of climate science by gathering data on the explosion of Krakatoa and the subsequent effects on the polar ice caps. We might gather data on the emergence and spread of agriculture from pre-history by observing transformation of forest land into farmland, and the appearance of greenery in places supportable only by irrigation. You might tell the story of the Tigris and the Euphrates that way. Of course, all of that depends on spectacular levels of resolution. And those would have to grow as we looked back further in time, because the lensed light would appear that much further away. I suppose most of what I've listed here could easily be outside any plausible resolution. I guess I imagine that some of climate science stuff might be dreamt of. But what a thing to think of!
EGreg 12y ago
I would first of all want to check if any religion's historical claims are true. That would help a lot of people with their beliefs!

scarygliders 12y ago

This reminded me of a short story I read, called Light Of Other Days, written by Bob Shaw. Instead of black holes or other massive objects, he used a concept called "slow glass" - glass in which light takes years to pass. Obviously, though, you'd had to have panes of slow glass in front of the scenes from life 6000 years ago...

jcoffland 12y ago
"Light of Other Days" is a great book but it was written by Stephen Baxter and Arthur C. Clarke.
- jcoffland 12y ago
  Wait, sorry. There are two books with similar titles. "The Light of Other Days" is by Stephen Baxter and Arthur C. Clarke. "Light of Other Days" is indeed by Bob Shaw. I have not read the latter. The former deals with a new technology which allows people to see in to the past via microscopic "wormholes".
davyjones 12y ago
This was one of the first works I read that changed my perspective to focus on the human elements in science fiction as opposed to the bells and whistles.

mulligan 12y ago

This article from berkeley is super relevant, it was published just a few days ago: https://newscenter.berkeley.edu/2015/03/05/distant-supernova-split-four-ways-by-gravitational-lens/ https://newscenter.berkeley.edu/2015/03/05/distant-supernova... We can see a supernova 4 different times using gravitational lensing.

dghughes 12y ago

Imagine if everything in the Universe was just the light from our solar system refracted billions of ways making it seem like there were galaxies but really we are all alone.

chrischen 12y ago

I am not a lawyer, but maybe if multiple MACHOs in the right positions could make this work.

Intermernet 12y ago

>In 2002 Daniel Holz and John Wheeler investigated this idea and ran all the calculations in their paper Retro-MACHOs: Pi in the Sky? That's one of the best paper names I've come across. From the introduction: >The bending power of a black hole is not limited, however, to small angles but reaches π and odd multiples of π. Illuminated by a powerful point source of light, the black hole will therefore shine back with a series of concentric rings (we call this retrolensing). Does anyone know if this sort of research is on the agenda for the James Webb Space Telescope? Our space imaging has progressed dramatically in the last couple of decades, so it wouldn't surprise me to see many more MACHOs (maybe even Retro-MACHOs!) being discovered, in the same way our understanding of the vast number of galaxies in the universe was increased by the Hubble Space Telescope.

mehwoot 12y ago

Is there any calculation on what resolution would be even theoretically possible? There are only a finite number of photons being emitted by the surface of the earth and so at a certain distance there wouldn't be enough to show detail past some level.

nether 12y ago

Would we ever be able to collect enough photons to form any kind of image though?

cake93 12y ago

How would the calculations play out for near-earth MACHOs and radio frequencies instead of visible light? I can imagine that the construction of a suitable antenna is more feasible than for a visible-light telescope?

bsurmanski 12y ago

Coincidentally, something like this was asked on reddit.com/r/askscience recently. http://www.reddit.com/r/askscience/comments/2y93cz/if_we_were_far_enough_from_earth_could_we_see_the/ http://www.reddit.com/r/askscience/comments/2y93cz/if_we_wer... (if we were far enough from the earth, could we see the dinosaurs) One comment claimed that the lens would be the limiting factor. If using traditional glass lens, they calculated that it would need a diameter of 4 light years to be able to see the dinosaurs. They furthermore claimed that a lens of this size would gravitationally collapse, and thus would not be feasible. I don't believe gravitational lensing was mentioned as of my reading.