Could An ExtraTerrestrial Find Earth with a Telescope?

Active Seti writes "If aliens were hunting life outside their own planet, could they peer through the vastness of space and lock onto Earth as a likely home for life? Researchers say with a roughly Hubble-sized array observers could measure Earth's 24-hour rotation period, possibly leading to observations of oceans and the chance of life. 'They would only be able to see Earth as a single pixel, rather than resolving it to take a picture,' said Astronomer Eric Ford. 'But that could be enough for them to identify our planet as one that likely contains clouds and oceans of liquid water.' The research will be useful to astronomers designing the next generation of space telescopes on our planet, because it provides an outline of the capabilities required for studying the surfaces of Earth-like worlds."

Comments

I've got an idea

[ILuvRamen]

We should totally arrange some stars into a smiley face or big arrow pointing at us then (yes I know that would only look right from certain angles, it's a joke). But you've got to wonder why some other super advanced civilization didn't move some stars around to circle themselves or something and make it really obvious where they lived.

Re:I've got an idea

[edwardpickman]

They probably did it's just their smiley face has five eyes and no mouth. The stars spelling out "We Are Here" are tough to read given the language differences and they use a pentagon to point instead of an arrow given they never developed archery. Celapods have trouble with bows. There is hope of translating the "Free Beer" part of the sign if we can only figure out the translation for beer. We do know there's an exclamation mark like symbol at the end of what's thought to be the word Beer. We know it as Orion's Belt.

Re:I've got an idea

[AKAImBatman]

But you've got to wonder why some other super advanced civilization didn't move some stars around to circle themselves or something and make it really obvious where they lived.

Impracticality? I mean, moving a star takes a tremendous amount of energy. Either that, or a massive gravitational mass that can be moved through more conventional means. (One of the drawbacks of stars is that you can't exactly setup thrusters on the surface of a flaming, gaseous body.) If they were even close to such technology, it would actually be easier to send out explorers than to muck around with the position of stars.

Assuming that such a civilization could even exist. Which is (unfortunately) somewhat doubtful. Everything we know so far suggests that life is exceedingly rare in the universe. Rare enough to make it difficult to find another civilization that used to exist, much less one that you can actually contact. (Don't even get me started on the incredible time scales by which the older civilization would be long dead before we could even see each other.)

Re:I've got an idea

[AKAImBatman]

Um, they told you that in bible school, right?

No, basic scientific principles told me this. While the Drake Equation is not accepted by all scientists as a valid computation, the Fermi Paradox is still a difficult problem to solve.

We are not so special. There are 10^21 stars out there - there must be many civilizations out there.

To throw an equally unfounded accusation back at you, you're a fan of Carl Sagan, right?

Let me put this in simple terms: The size of the universe is known to be at least 93 billion light years across, and is estimated to be ~13.7 billion years old. In a universe that big and that old, there is a strong chance that any other civilization(s) that may have formed are extremely far apart from one another. So far apart that there is a good chance that the civilization(s) will "miss" each other's existence.

Like it or not, if there was a civilization coexisting in our neck of our galaxy, we'd have some inkling of it already. Unnatural radio transmissions would stand out against the background radiation and give us a sense that another civilization is there. We have been scanning the skies with powerful equipment and so far have come up with little to no evidence of such transmissions.

The long and short of it is that from what we know today, there's an infinitesimal chance that we humans will ever meet another civilization. The best we can hope for is that we find planets that support more basic forms of life.

Too many assumptions?

[RobertM1968]

The article makes a lot of assumptions such as:
(1) Life on other planets has the same requirements for existence as us (Class M
        planet, water, air like ours, gravity like ours, etc)
(2) Extra-terrestrials will be using technology similar to ours (as opposed to more advanced tech)
(3) (Basing off #1 being true as they did) there are planets suitable for life such as ours that
        we haven't yet discovered that are looking in our direction.

Re:Too many assumptions?

[Liquidrage]

There's a lot to that discussion. We tend to assume that the laws of physics will work pretty much all over the galaxy. And in places where our current understandings break down, life isn't likely to exist (black holes, Planck scales, etc...).

Given this assumption, there aren't a lot of options for different types of life. The chemistry just doesn't work. Biology is chemistry, chemistry is physics, and physics is mathematics. It basically puts in some ground rules for life. There's a decent little wiki on this: http://en.wikipedia.org/wiki/Alternative_biochemistry

As you can see in that wiki (there are pro's and con's for each of the alternates), based on our understanding life either does need most of the same things we do, or at least our biochemistry should be the most common in the universe. The math just makes it that way. There are some variables sure. And some alternatives. But for the most part, looking for stuff life us seems to most likely scenario.

Now, given this, #1 and #2 should fall somewhat in line with what they're thinking. Sure, the minutia of evolution could lead to exotic live from our perspective. Something other then DNA based life even. But they (the aliens) should still come up with e=mc And their biochemistry should, at least, be something comparable to ours.

oxygen, man

[Quadraginta]

Phoo, once you've detected O2 in the atmosphere, you're done. Only life could produce that much free oxidizer in a strongly reducing universe.

And then there is the possibility

[elgee]

That ET will find us with a microscope.

Lightspeed is slow

[GeneralCC]

Well, if extraterrestrials were able to see earth using electromagnetic radiation (ie light, radio waves, ect) depending on their distance they would not see a modern earth. If they were over 5 billion light years away then if they looked at this solar system the Sun and the Earth would just be forming. This is because light speed is too slow. By the time the light reaches the extraterrestrials a large amount of time would have passed. They would have to use something other than a telescope to see a modern life sustaining Earth.

Intergalactic quarantine symbol

[Hognoxious]

Rings around a gas giant means "keep the hell away from this system and don't, whatever you do, let the inhabitants get out".

Re:pixelization

[imsabbel]

I see your humor, but...

A single pixel can provide a hell of a lot of information: Do spectroscopy, and you can get the typical absorption lines (O2 for example should be easy to detect, and be a sure way for _anybody_ who detects it to tell something is odd about that planet).
Track the intensity over time, and you can get the rotation period.

We've Already Been Discovered

[DavidD_CA]

We've already been discovered, twice.

The first time: they discussed us using irrelevant analogies, took a senseless poll, said things like "imagine a Beowulf cluster of these" and "itsatrap!", and one alien remarked "I, for one, welcome our new Earthling overlords."

The second time: they just shouted "DUPE!" and moved on.