Gravitational Lensing to Observe Ancient Earth

http://rein.pk/gravitational-lensing-to-observe-ancient-earth/

by pinko • 11 years ago

137 45 11 years ago

3327• 11 years 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• 11 years ago

For the digital-network analogue, see pingfs: http://www.shysecurity.com/posts/PingFS

tbrownaw• 11 years ago

http://en.wikipedia.org/wiki/Delay_line_memory

rcthompson2• 11 years 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

pdonis4• 11 years 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).

rcthompson2• 11 years 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_rel...

jkot• 11 years ago

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

privong• 11 years 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

[1] http://arxiv.org/abs/astro-ph/9512103

[2] http://www.aps.org/publications/apsnews/199507/macho.cfm

ComputerGuru• 11 years 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• 11 years 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.

sixQuarks2• 11 years 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.

jcoffland6• 11 years 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__• 11 years 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.

thanatosmin• 11 years ago

Yes, there are many ways in which cutting edge science seems indistinguishable from limitless magic. As a scientist though, this perspective requires ignoring that nearly all my time requires attempts to overcome physical limitations. Sure, these things may be possible, but they require overcoming many currently impossible limits.

kiba• 11 years ago

As long it is logically possible, we can make it happen.

But you won't violate the laws of thermodynamic no matter how hard you try.

sixQuarks2• 11 years ago

Never say never. There's speculation of a multi-verse, and in some universes, nature's laws are random and different from this one. There could be a universe where the laws of thermodynamics is different, and there may be a way to tap into that universe.

intrasight• 11 years 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• 11 years ago

Godel Escher Bach has a chapter riffing on the acoustics version of this idea: 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• 11 years ago

Reminds me of this http://newsoffice.mit.edu/2014/algorithm-recovers-speech-fro...

pdonis4• 11 years 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• 11 years ago

There was an X-Files episode with this idea. Something Jesus said ("Talitha cumi") was recorded in a piece of pottery.

jimmcslim• 11 years 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• 11 years 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• 11 years 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!

Intermernet2• 11 years ago

Using the GP's figure of 65 years ago, you could check out Elron's claims. Scientology was founded in 1952. Dianetics was going crazy for a few years before that.

Other than that we need to find some MACHOs between ~700 and ~1800 lightyears away in order to check the claims of the more popular religions.

But, considering the data would be coming from the scientific (and in particular the atrophysics) community, it would be ignored by those who found it inconvenient.

Religion and Astronomy have a very checkered past.

scarygliders• 11 years 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...

jcoffland6• 11 years ago

"Light of Other Days" is a great book but it was written by Stephen Baxter and Arthur C. Clarke.

jcoffland6• 11 years 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• 11 years 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• 11 years 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...

We can see a supernova 4 different times using gravitational lensing.

dghughes• 11 years 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• 11 years ago

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

Intermernet2• 11 years 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• 11 years 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• 11 years ago

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

cake93• 11 years 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• 11 years ago

Coincidentally, something like this was asked on reddit.com/r/askscience recently.

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.

Gravitational Lensing to Observe Ancient Earth

Related Stories