It's useless science Friday in my head - Welcome to the show.

[helosailor]

in theory.

Theoretically.

[Strychnine]

Theoretical question.

Say we develop super high speed space travel. Could we in theory head out into space a determined distance and then turn around and observe the earth from this great distance in order to see the past?

Granted we would have to travel faster than light to get far enough ahead to do this, but in theory I could work, correct?

You'll never travel anywhere near an appreciable fraction of the speed of light because of Special Relativity and that pesky exponent in E=mc^2. So really you'd have to work out that whole wormhole situation to travel any light-year scale distance quickly. Say you do warp space and jump from one point to another you still can't trick the optics.

It's basically the same as asking, "If someone were on a planet 65+ million light years away could they see dinosaurs if they looked at Earth?" and the answer really has to be no. Light reflected from earth (or anything for that matter) is diluted over distance (following the inverse-square law) so by the time you got that far away the lens of your telescope (however large you may decide to build it) could never gather enough photons from Earth to make out anything more than a dot of dim light - the resolution just isn't possible.

[Strychnine]

Not quite as big a deal as detection of Gravity Waves, but...

In the Bernie Sanders' spirit of giving away free shit, download yourself some cool NASA/JPL retro sci-fi space travel posters.

http://www.jpl.nasa.gov/news/news.php?feature=5052

I love those. Someone on Reddit had them printed, framed, and hung in his living room.

[Craizie]

You'll never travel anywhere near an appreciable fraction of the speed of light because of Special Relativity and that pesky exponent in E=mc^2. So really you'd have to work out that whole wormhole situation to travel any light-year scale distance quickly. Say you do warp space and jump from one point to another you still can't trick the optics.

It's basically the same as asking, "If someone were on a planet 65+ million light years away could they see dinosaurs if they looked at Earth?" and the answer really has to be no. Light reflected from earth (or anything for that matter) is diluted over distance (following the inverse-square law) so by the time you got that far away the lens of your telescope (however large you may decide to build it) could never gather enough photons from Earth to make out anything more than a dot of dim light - the resolution just isn't possible yet.

..

[Grimpala]

You'll never travel anywhere near an appreciable fraction of the speed of light because of Special Relativity and that pesky exponent in E=mc^2. So really you'd have to work out that whole wormhole situation to travel any light-year scale distance quickly. Say you do warp space and jump from one point to another you still can't trick the optics.

It's basically the same as asking, "If someone were on a planet 65+ million light years away could they see dinosaurs if they looked at Earth?" and the answer really has to be no. Light reflected from earth (or anything for that matter) is diluted over distance (following the inverse-square law) so by the time you got that far away the lens of your telescope (however large you may decide to build it) could never gather enough photons from Earth to make out anything more than a dot of dim light - the resolution just isn't possible.

Roger

[Grimpala]

..

From what I gather it would never be possible due to the scattering/diffusion of the light particles as they traveled away.

The 1.3 billion year old signals weren't light, they were gravitational, something that can be physically detected, whereas the light would be too diffuse to assemble a discernible picture of dinosaurs.

[Strychnine]

the resolution just isn't possible yet

No, really. Not possible.

Light dims over distance according to the inverse square law: "The energy twice as far from the source is spread over four times the area"




Dimmer light = fewer photons at the viewer, so think about it like this:




I did some math for you. To see dinosaurs you would need to go a minimum of 65 million light years away. Compare the light intensity of the Earth from the surface of the Moon to what you would get on this faraway planet...




At that distance you'll have 0.000000000000000000000000000039125 times fewer protons to capture. That's so far beyond any needle in a haystack situation just to get ONE photon...
Beyond the Earth just reflects light, it doesn't produce it, and it's fairly close to a really bright source of light, so good luck even seeing anything that's not the Sun when you point your impossibly large telescope this way.


FWIW, this is how Hubble sees an entire galaxy from 60 million light years away. It measures 45,000 light years across and is really just a fuzzy glow.

[Craizie]

No, really. Not possible.

Light dims over distance according to the inverse square law: "The energy twice as far from the source is spread over four times the area"




Dimmer light = fewer photons at the viewer, so think about it like this:




I did some math for you. To see dinosaurs you would need to go a minimum of 65 million light years away. Compare the light intensity of the Earth from the surface of the Moon to what you would get on this faraway planet...




At that distance you'll have 0.000000000000000000000000000039125 times fewer protons to capture. That's so far beyond any needle in a haystack situation just to get ONE photon...
Beyond the Earth just reflects light, it doesn't produce it, and it's fairly close to a really bright source of light, so good luck even seeing anything that's not the Sun when you point your impossibly large telescope this way.


FWIW, this is what an entire galaxy looks like from 60 million light years away

That's what it looks like now...I understand it's impossible now.

[slow99]

I concur.

[Grimpala]

That's what it looks like now...I understand it's impossible now.

[line-em-up]

[Strychnine]

LOL get black2002ls in here. He's the one with the damn physics degree.

[mstng86]

This is all cool and stuff but really, I just want to know how to catch a gnarly gravity wave and surf a gravity pipe.

[Strychnine]

Aren't there multiple variables, like light traveling through a vacuum as opposed to an atmosphere, like earth's? Being both a particle and a wave, I'd think that it would.

Variables only make things worse. That is an ideal equation. Can't get any better. In the real world those very few photons over those many billions of miles would battle gravity wells from blackholes, other galaxies, dark matter, etc and get thrown "off course" or they would pass through gas/dust clouds and be diffracted/scattered...


Craizie, I get what you're saying, science is always getting better, but I think this is one of those things where the physics literally can't back it up.

No matter what way you slice it information is lost over distance. One of the most distant exoplanets discovered is ~13,000 light years away, and we've never even seen it. We don't have the ability. The only way we know it's there is to use some pretty baller techniques that involve using gravitational lensing from one star to magnify another star to then study the ever-so-slight blip of light change from a planet around that second star as a planet orbits it. Trying to optically observe, on a surface lifeform level, a planet 845,000,000,000 times farther than that just isn't going to happen.



Side note on the gravity waves thing. This was written by a particle physicist today:

Basically you can think of this experiment as that of detecting a pin drop at the 50 yard line during an NFL game, and your detection equipment is five states over and in the back of a van down by the river. We're watching the game on a little shitty TV in the back of the van, and we've been told by the announcer that a pin was dropped on the 50 yard line, but we have no way of actually seeing it because its obviously too tiny, our TV is too shitty, and the noise is too loud.

[Rick Modena]

I'd like to make a poster of that Galaxy that Hubble took...