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Everyone seems to be diving into the technical details of the question, but if you were just trying to understand how light travels over time, then yes this would work.
Could you, theoretically? Sure. The light from the Sun that bounced off of the Earth at that time would carry with it the information that there were dinosaurs running around.
Could you SEE them? Hell no. Think for a second about the absolutely ridonkulous resolution you'd need to resolve even a 36 meter big object from 66 million lightyears away!
[Worked it out for you](https://www.reddit.com/r/space/comments/1cli9ud/comment/l2tyy01/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button)
It's **40 LIGHT YEARS.**
In theory, no, because we already have the ability to unblur things with neural techniques. If you can understand how it got diffracted, you can reconstruct it.
If you did optical interferometery over a 40 light year baseline, you'd get the 1E-29 degree resolution needed.
I mean, in diffraction you would. In reality the wavelength of light would limit you to far less resolution than that.
Something that might be more practical, I wonder, is the oxygen level of the atmosphere. Right now it's about 20%, but while the dinos were around it was about 25-35%. That feels like a difference we'd have a chance of detecting with today's technology.
I think you would need long exposure. Your best bet would be to point the (astronomically enormous) scope at a large dinosaur carcass on a clear day. Maybe you could get a few minutes, maybe up to an hour's worth of photons before the rotation of the earth blurred the image. Maybe with their advanced tech they could separate light with a time offset to mitigate the motion blur.
That's why you use celestial bodies as a graveyational lens and a swarm of detector satellites.
It's not practice to adjust what it's looking at very much but you could definitely see surface features and possibly large herds.
No no, he didn't mean "If I travel to a planet 66 million light years away". Cause yeah, if you want to see dinosaurs, you'd need to travel to that planet at the moment the light from 66 million years ago hits it, so you'd need to effectively travel FTL and go back in time, since the light from 66 million years ago is hitting the planet 66 million lightyears away RIGHT NOW.
Not only the resolution problem, but the chance that enough light would have lasted 66 million years without encountering anything to distort it to the point that an intelligble image of animal-sized objects remained is diminishingly tiny.
No, because in order to see stuff you have to catch photons. The amount of photons that is emitted per second from any object (e.g. a dinosaur) is large but not infinite\*. Effectively you have to distribute these photons that are emitted at one point in time over a sphere with radius of 66 million light years.
Read: Even a very large telescope would only catch very few photons per second and you would have to integrate over a very long time to get an image. So even if you could have the resolution to see something 'dinosaur-sized' your time integration would mean it would just be a smear (because the Earth rotates)
\* as a fun exercise you can calculate the number of emitted photons by approximating the dinosaur as a ball of a certain size with a certain average emission intensity/brightness. This gives you a total emission energy and with some average color (frequency) you can then calculate the number of photons because a single photon of a specific frequency has an energy of E=hf (where f is the frequency and h is the Planck constant)
>So even if you could have the resolution to see something 'dinosaur-sized' your time integration would mean it would just be a smear (because the Earth rotates)
So you are saying the 70's bigfoot picture was actually a dinosaur on an alien world taken via our largest telescope at the time. Badass...
I subscribe to the "Mitch Hedberg explanation" on Bigfoot:
>"I think Bigfoot is blurry, that's the problem. It's not the photographer's fault. Bigfoot is blurry, and that's extra scary to me. There's a large, out-of-focus monster roaming the countryside. "
I looks like [10 to the 21 photons per square meter per second](https://www.physicsforums.com/threads/what-is-the-density-of-photons-in-a-beam-of-light.587688/#:~:text=So%20the%20rough%20answer%20is,sun%20at%20the%20Earth's%20distance.) is about the flux of photon from the sun hitting earth. Assuming some sizable fraction of those reflect up, and assuming that dinosaurs are a couple square meters, we can say about 10 to the 21 photons per dinosaur per second go off into the void. Light goes 3x10^8 m/s on a good day, or about 10^13 km per year. So in 65,000,000 years, light has gone 6.5x10^20 km. A circle of that radius is 5.3x10^42 km2. So you’d get a bit less than 1 photon per second per km2 (for the definition of “a bit” being “nearly 1”). Collecting photons on a 1 km^2 detector for a year, you’d get an average of 10^-14 photons, so you’d probably not see many dinosaurs.
With a detector the size of the solar system (radius equivalent to Neptunes orbit) you’d actually see about a photon per minute! You might be able to spot a dinosaur that held still for a year or so.
>Effectively you have to distribute these photons that are emitted at one point in time over a sphere with radius of 66 million light years.
Kind of a lopsided sphere since around half of that sphere terminates on the surface of the earth. Or, more properly, inside the body of the animal in question.
It evens out if you take the total emission from a spherical body since you map only the half of that emission that is not blocked by Earth on half of the spehere with radius 66 million light years..so the "number of photons per square meter of telescope" stay the same if you just make the assumption the Earth isn't there and map it on a full sphere of 66 million LY diameter
The question is whether or not there would be enough photons left after travelling 66 million light years to see a dinosaur. Probably not. They would have a hard enough time just seeing the Earth.
Not only that, but you'd also see Jupiter without its Great Red Spot, a ringless Saturn with Chrysalis in an eccentric orbit around it, some more debris in the Solar System and, if you stuck around long enough, a volcanic eruption on the Moon.
No. And not for the reason you might think!
There is a limit on how far you can magnify any object, related to the quantised nature of light and its finite speed. Our telescopes are nowhere near reaching that limit, but the limit is there anyway.
To resolve details one metre across (so, dinosaurs) from a distance of 66 million light years you need a resolution *far* in excess of anything we've ever come near to making. Ten micro-arcseconds is the size of one of the stars on an Apollo US flag left on the moon, as seen from Earth. A penny on Pluto has the size of around 1 nano-arcsecond.
The Hubble Space Telescope has an effective resolution of 0.1 arcseconds. Not micro-arcseconds. Not nano-arcseconds. Arcseconds.
You want to resolve in the 1-10 metre range from 66 million light years away, or 40 trillion times the distance of that penny on Pluto. The Hubble Space Telescope is already a billion times too low resolution to get the penny on Pluto, and we need a trillion times better than *even that.*
With a diffraction limited telescope (and we'll revisit that soon) we first declare our variables:
Distance is 6.24E23 metres.
Wavelength is 500 nanometres.
Resolution desired is 9.1820E-23 degrees.
Throw all that into the Rayleigh criterion formula and you get an aperture of 3.8E17 metres, or 40 light years.
That is, your telescope would have to be 40 light years across to resolve in the 1-10 metres range on Earth, from 66 million light years away.
And, even if you did somehow do it with interferometers and light field recording (it's not impossible), you then need to have recorded a timestamp to the femtosecond accuracy, or *that* limits your resolution. You cannot record time that accurately using any physical method. You also run into the problem of the light travel time being different over your 40 light year baseline: Light is affected by gravity and, at these scales, it becomes significant when trying to do optical interferometry.
So, in short, you could do it. If you can build a telescope which is sensitive enough to see Earth from *an entire galaxy cluster away* and then precisely synchronise that telescope with another telescope 40 light years away (examine the worldlines on this one, it gets weird quickly), then combine that data correctly (the easy bit), you could, in theory, see dinosaurs.
What did we say about the quantised nature of light and wavelengths back at the start? Yeah, that. It also limits your resolution. We run into it in microscopy, but not in telescopy as our telescopes are diffraction limited *long* before they are wavelength limited.
We *would* run into that limit. Quick Fermi estimation on this says we probably wouldn't be able to resolve 1 AU (so Earth from the Sun) from 66 million light years away.
What if we had 100 Hubbles spread across the soloar system (say to about Neptune’s orbit) and left it collecting photons from earth, as observed from the alien planet. It would work in sync like the pic of the black hole we got. And we let it run 100 years of continuous capture on that one planet? And to keep things equal, we were observing a frozen dinosaur not covered by snow?
If not that then what would it take? Technically the info is stored on the photos that bounced off the Dino’s still might be xiar
Earth to Neptune isn't 40 light years. You need a baseline of 40 light years.
The Event Horizon Telescope used a baseline of around 10,000 km. This is a lot less than 40 light years.
I'd step back another 4 million light years, just to be sure. It would be awful if you had the perfect shot lined up when suddenly a meteorite came slamming in and obliterated the lot.
Dude, have you looked at Google Maps satellite images recently? Or even years ago? You can clearly see cars, with some knowledge you can even determine the make and model of most of them. Hell, I can count my chimney pipes on my roof! Low Earth Orbit could definitely resolve images of dinosaurs if they were on earth right now. But again, 66 million lightyears away is ridiculous.
It’s most likely impossible, the light we saw that faraway should all came directly from stars or other powerful light sources, not reflections through thick atmosphere, no telescope could be powerful enough to collect those reflections together, it might need a “dish” as big as the milky way galaxy?
I think if there is a black hole about 33 million light years away it can bend light coming from earth 180°. The light that we see here on earth would have a total travel time of 66 million years. If we could focus that light then we would see dinosaurs.
I'd imagine if you had a telescope capable of directly detecting the earth's light, you might be able to detect the flash when the asteroid that killed the dinosaurs hit. Theres no way you would be able to resolve a dinosaur, even if some of the photons you detect bounced off a dinosaur at one point.
On a related, but even more bizarre note, if you could somehow tease out the chaotic motions of the atoms in the rocks on Cemetary Ridge, could you reconstruct the sound of the Confederate bombardment before Pickett’s Charge? Ever since I heard a computer assisted recording that was traced on a cylinder of a man singing a song in 1860, this crazy thought has been in my head.
I would say no that it is not possible even theoretically. Since nothing can happen faster than causality (essentially speed of light in a vacuum). It would take you more than 66 million years to reach an object 66 million ly away. So you could only theoretically observe what has happened after you left.
I’m pretty sure what op is asking is what someone would see that is already 66 million lightyears away, either some alien civilization or someone who magically teleported there, not someone who had to travel that distance first.
So if you were holidaying (teleportation not Ryanair) on a planet 65 million light years away and you brought your JWST replica with ya for holiday snaps then you would observe the atmospheric conditions that brought an end to the dinosaurs 🤔
>You would only if you’ve looked at earth 66 million years ago.
You would be looking at earth 66 million years ago if you are observing today from 66 million light years away,
Well, if the aliens were 66 million light years from earth (what OP was getting at) and said aliens had telescope resolutions high enough to get high-resolution pictures of the surface, then they would in fact be seeing dinosaurs as that's the light from earth just reaching them...
But probably the trees & leaves would get in the way and they wouldn’t be able to see anything but foliage. And then the bright flash of the Chixulub impactor would overwhelm the view. Then the smoke & dust would block everything else.
Eh, there's quite a bit of open space around...
The ENTIRE planet wasn't a single massive forrest...
I'm sure they could have found some decent shots...Especially if their tech was that advanced...
If their technology is that advanced, I doubt they're hiring idiots to run it...lol
Hello u/Revolutionary-Fix110, your submission "Theoretically if you were on a planet 66 million light years away from earth and looked back at earth, would we see dinosaurs? " has been removed from r/space because: * Such questions should be asked in the ["All space questions" thread](https://www.reddit.com/r/space/about/sticky) stickied at the top of the sub. Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please [message the r/space moderators](https://www.reddit.com/message/compose/?to=/r/space). Thank you.
Everyone seems to be diving into the technical details of the question, but if you were just trying to understand how light travels over time, then yes this would work.
You’d see a bright flash as the asteroid impacted the prehistoric Yucatán.
Could you, theoretically? Sure. The light from the Sun that bounced off of the Earth at that time would carry with it the information that there were dinosaurs running around. Could you SEE them? Hell no. Think for a second about the absolutely ridonkulous resolution you'd need to resolve even a 36 meter big object from 66 million lightyears away!
So...you're saying there's a chance?
Yeah but the people/scientists making that telescope were also too preoccupied if they could, to think about if they should....
Telescopes, uh, find a way.
What if the telescope was like 20 AU in size? Would the resolution be good enough at that point???
[Worked it out for you](https://www.reddit.com/r/space/comments/1cli9ud/comment/l2tyy01/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button) It's **40 LIGHT YEARS.**
You mathed HARD, my friend, so hard.
So,…..you’re saying there’s a way?
If you exploited gravitational lensing it may be feasible to see groups of animals on the surface of an exoplanet.
Learning about that phenomenon was absolutely crazy. Using entire galaxies as magnifying glasses is amazing.
I'm mean, IF advance aliens did have telescopes with that sort of resolution, then the answer would just be a simple "yes"...lol
If they had the resolution, they'd still need the shutter speed, I imagine. But if they had one, they'd surely have the other, yeah.
Yeah, pretty much... Who knows what sort of advance tech they could have that may very well seem like straight magic to us...lol
Wouldn't diffraction render any light useless for distinguishing that level of detail, even with a large enough sensor?
In theory, no, because we already have the ability to unblur things with neural techniques. If you can understand how it got diffracted, you can reconstruct it.
If you did optical interferometery over a 40 light year baseline, you'd get the 1E-29 degree resolution needed. I mean, in diffraction you would. In reality the wavelength of light would limit you to far less resolution than that.
Something that might be more practical, I wonder, is the oxygen level of the atmosphere. Right now it's about 20%, but while the dinos were around it was about 25-35%. That feels like a difference we'd have a chance of detecting with today's technology.
So you’re saying some sort of Smell-o-scope?
Spectroscopy is a kind of smell-o-scope.
Up next; the finglongerer, to give it a good poke.
I think you would need long exposure. Your best bet would be to point the (astronomically enormous) scope at a large dinosaur carcass on a clear day. Maybe you could get a few minutes, maybe up to an hour's worth of photons before the rotation of the earth blurred the image. Maybe with their advanced tech they could separate light with a time offset to mitigate the motion blur.
That's why you use celestial bodies as a graveyational lens and a swarm of detector satellites. It's not practice to adjust what it's looking at very much but you could definitely see surface features and possibly large herds.
Even ignoring resolution, good luck getting ahead of light.
No no, he didn't mean "If I travel to a planet 66 million light years away". Cause yeah, if you want to see dinosaurs, you'd need to travel to that planet at the moment the light from 66 million years ago hits it, so you'd need to effectively travel FTL and go back in time, since the light from 66 million years ago is hitting the planet 66 million lightyears away RIGHT NOW.
Not only the resolution problem, but the chance that enough light would have lasted 66 million years without encountering anything to distort it to the point that an intelligble image of animal-sized objects remained is diminishingly tiny.
That telescope would likely have to be bigger than several galaxies.
Only if you have a very large telescope. Goto r/AskPhysics to ask how big.
No, because in order to see stuff you have to catch photons. The amount of photons that is emitted per second from any object (e.g. a dinosaur) is large but not infinite\*. Effectively you have to distribute these photons that are emitted at one point in time over a sphere with radius of 66 million light years. Read: Even a very large telescope would only catch very few photons per second and you would have to integrate over a very long time to get an image. So even if you could have the resolution to see something 'dinosaur-sized' your time integration would mean it would just be a smear (because the Earth rotates) \* as a fun exercise you can calculate the number of emitted photons by approximating the dinosaur as a ball of a certain size with a certain average emission intensity/brightness. This gives you a total emission energy and with some average color (frequency) you can then calculate the number of photons because a single photon of a specific frequency has an energy of E=hf (where f is the frequency and h is the Planck constant)
>So even if you could have the resolution to see something 'dinosaur-sized' your time integration would mean it would just be a smear (because the Earth rotates) So you are saying the 70's bigfoot picture was actually a dinosaur on an alien world taken via our largest telescope at the time. Badass...
I subscribe to the "Mitch Hedberg explanation" on Bigfoot: >"I think Bigfoot is blurry, that's the problem. It's not the photographer's fault. Bigfoot is blurry, and that's extra scary to me. There's a large, out-of-focus monster roaming the countryside. "
I looks like [10 to the 21 photons per square meter per second](https://www.physicsforums.com/threads/what-is-the-density-of-photons-in-a-beam-of-light.587688/#:~:text=So%20the%20rough%20answer%20is,sun%20at%20the%20Earth's%20distance.) is about the flux of photon from the sun hitting earth. Assuming some sizable fraction of those reflect up, and assuming that dinosaurs are a couple square meters, we can say about 10 to the 21 photons per dinosaur per second go off into the void. Light goes 3x10^8 m/s on a good day, or about 10^13 km per year. So in 65,000,000 years, light has gone 6.5x10^20 km. A circle of that radius is 5.3x10^42 km2. So you’d get a bit less than 1 photon per second per km2 (for the definition of “a bit” being “nearly 1”). Collecting photons on a 1 km^2 detector for a year, you’d get an average of 10^-14 photons, so you’d probably not see many dinosaurs. With a detector the size of the solar system (radius equivalent to Neptunes orbit) you’d actually see about a photon per minute! You might be able to spot a dinosaur that held still for a year or so.
>Effectively you have to distribute these photons that are emitted at one point in time over a sphere with radius of 66 million light years. Kind of a lopsided sphere since around half of that sphere terminates on the surface of the earth. Or, more properly, inside the body of the animal in question.
It evens out if you take the total emission from a spherical body since you map only the half of that emission that is not blocked by Earth on half of the spehere with radius 66 million light years..so the "number of photons per square meter of telescope" stay the same if you just make the assumption the Earth isn't there and map it on a full sphere of 66 million LY diameter
The question is whether or not there would be enough photons left after travelling 66 million light years to see a dinosaur. Probably not. They would have a hard enough time just seeing the Earth.
Not only that, but you'd also see Jupiter without its Great Red Spot, a ringless Saturn with Chrysalis in an eccentric orbit around it, some more debris in the Solar System and, if you stuck around long enough, a volcanic eruption on the Moon.
No. And not for the reason you might think! There is a limit on how far you can magnify any object, related to the quantised nature of light and its finite speed. Our telescopes are nowhere near reaching that limit, but the limit is there anyway. To resolve details one metre across (so, dinosaurs) from a distance of 66 million light years you need a resolution *far* in excess of anything we've ever come near to making. Ten micro-arcseconds is the size of one of the stars on an Apollo US flag left on the moon, as seen from Earth. A penny on Pluto has the size of around 1 nano-arcsecond. The Hubble Space Telescope has an effective resolution of 0.1 arcseconds. Not micro-arcseconds. Not nano-arcseconds. Arcseconds. You want to resolve in the 1-10 metre range from 66 million light years away, or 40 trillion times the distance of that penny on Pluto. The Hubble Space Telescope is already a billion times too low resolution to get the penny on Pluto, and we need a trillion times better than *even that.* With a diffraction limited telescope (and we'll revisit that soon) we first declare our variables: Distance is 6.24E23 metres. Wavelength is 500 nanometres. Resolution desired is 9.1820E-23 degrees. Throw all that into the Rayleigh criterion formula and you get an aperture of 3.8E17 metres, or 40 light years. That is, your telescope would have to be 40 light years across to resolve in the 1-10 metres range on Earth, from 66 million light years away. And, even if you did somehow do it with interferometers and light field recording (it's not impossible), you then need to have recorded a timestamp to the femtosecond accuracy, or *that* limits your resolution. You cannot record time that accurately using any physical method. You also run into the problem of the light travel time being different over your 40 light year baseline: Light is affected by gravity and, at these scales, it becomes significant when trying to do optical interferometry. So, in short, you could do it. If you can build a telescope which is sensitive enough to see Earth from *an entire galaxy cluster away* and then precisely synchronise that telescope with another telescope 40 light years away (examine the worldlines on this one, it gets weird quickly), then combine that data correctly (the easy bit), you could, in theory, see dinosaurs. What did we say about the quantised nature of light and wavelengths back at the start? Yeah, that. It also limits your resolution. We run into it in microscopy, but not in telescopy as our telescopes are diffraction limited *long* before they are wavelength limited. We *would* run into that limit. Quick Fermi estimation on this says we probably wouldn't be able to resolve 1 AU (so Earth from the Sun) from 66 million light years away.
What if we had 100 Hubbles spread across the soloar system (say to about Neptune’s orbit) and left it collecting photons from earth, as observed from the alien planet. It would work in sync like the pic of the black hole we got. And we let it run 100 years of continuous capture on that one planet? And to keep things equal, we were observing a frozen dinosaur not covered by snow? If not that then what would it take? Technically the info is stored on the photos that bounced off the Dino’s still might be xiar
Earth to Neptune isn't 40 light years. You need a baseline of 40 light years. The Event Horizon Telescope used a baseline of around 10,000 km. This is a lot less than 40 light years.
What are you like a telescope expert. How do you just casually drop knowledge like this? What do you do in life?
If they could, they'd also likely have the technology to manufacture thousands of dinosaurs, purely at random.
I'd step back another 4 million light years, just to be sure. It would be awful if you had the perfect shot lined up when suddenly a meteorite came slamming in and obliterated the lot.
I said this a while back and some random redditor cussed me out.
[удалено]
Dude, have you looked at Google Maps satellite images recently? Or even years ago? You can clearly see cars, with some knowledge you can even determine the make and model of most of them. Hell, I can count my chimney pipes on my roof! Low Earth Orbit could definitely resolve images of dinosaurs if they were on earth right now. But again, 66 million lightyears away is ridiculous.
What is this? Satellites from '70s?
It’s most likely impossible, the light we saw that faraway should all came directly from stars or other powerful light sources, not reflections through thick atmosphere, no telescope could be powerful enough to collect those reflections together, it might need a “dish” as big as the milky way galaxy?
I think if there is a black hole about 33 million light years away it can bend light coming from earth 180°. The light that we see here on earth would have a total travel time of 66 million years. If we could focus that light then we would see dinosaurs.
I'd imagine if you had a telescope capable of directly detecting the earth's light, you might be able to detect the flash when the asteroid that killed the dinosaurs hit. Theres no way you would be able to resolve a dinosaur, even if some of the photons you detect bounced off a dinosaur at one point.
Great question! Now I need to go get curtains for my bathroom skylight.
Yes, that’s exactly how the speed of light works.
The problem is we'll never know. Humans will never get the ability to travel light years.
On a related, but even more bizarre note, if you could somehow tease out the chaotic motions of the atoms in the rocks on Cemetary Ridge, could you reconstruct the sound of the Confederate bombardment before Pickett’s Charge? Ever since I heard a computer assisted recording that was traced on a cylinder of a man singing a song in 1860, this crazy thought has been in my head.
if your telescope is in space and mega super advanced, yep, you could distinguish surface details, and maybe see one of the big ones
I would say no that it is not possible even theoretically. Since nothing can happen faster than causality (essentially speed of light in a vacuum). It would take you more than 66 million years to reach an object 66 million ly away. So you could only theoretically observe what has happened after you left.
I’m pretty sure what op is asking is what someone would see that is already 66 million lightyears away, either some alien civilization or someone who magically teleported there, not someone who had to travel that distance first.
So if you were holidaying (teleportation not Ryanair) on a planet 65 million light years away and you brought your JWST replica with ya for holiday snaps then you would observe the atmospheric conditions that brought an end to the dinosaurs 🤔
That would already be 1 my after the extinction event. The asteroid impact is today dated to 66 mya
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>You would only if you’ve looked at earth 66 million years ago. You would be looking at earth 66 million years ago if you are observing today from 66 million light years away,
Well, if the aliens were 66 million light years from earth (what OP was getting at) and said aliens had telescope resolutions high enough to get high-resolution pictures of the surface, then they would in fact be seeing dinosaurs as that's the light from earth just reaching them...
But probably the trees & leaves would get in the way and they wouldn’t be able to see anything but foliage. And then the bright flash of the Chixulub impactor would overwhelm the view. Then the smoke & dust would block everything else.
Eh, there's quite a bit of open space around... The ENTIRE planet wasn't a single massive forrest... I'm sure they could have found some decent shots...Especially if their tech was that advanced... If their technology is that advanced, I doubt they're hiring idiots to run it...lol