Comments on: Viewing Earth as an Extra-Solar Planet

By: Alex Jones

Alex Jones — Thu, 15 Jan 2009 01:32:52 +0000

Not so much time ago, some scientist (sorry, I don't remember who and where) said, that the electro-magnetic emissions from radio and TV diffuse completely into the interstellar noise in a distance of a small number of light years. If this is true – and it's plausible for me – any civilization in a distance of, say, 60 to 100 light years wouldn't know about us through these emissions. If there is no signal, then, even by using a very, very advanced technique, "they" cannot recognize it.

By: Bill L.

Bill L. — Wed, 14 Jan 2009 20:44:02 +0000

@ damian

Actually, yes. Well, no. Kind of.

Absolute zero is impossible to achieve, but supercooling telescopes (especially space telescopes) is certainly not a new idea.

For instance, most infrared telescopes have to be kept extraordinarily cool, as heat generated by the telescope itself would overpower any observations.

By: Rod Beaton

Rod Beaton — Wed, 14 Jan 2009 19:13:55 +0000

I think
We should search for life on Earth from Orbit.
We should figure out what to look for,- that says, the planet has possible life on it.
Maybe the 'blue' color- maybe the clear skies here and clouds there. Is there Oxygen
Is there land mass? Also is the planetary temperature ideal for life?
For instance is there life on 'Neptune'?
Neptune is 'blue'..There might be fish
on neptune, though the gravity would make
them very strong fish…

Anyway, that's my amateurish opinion.

By: Howard2

Howard2 — Wed, 14 Jan 2009 18:30:07 +0000

Stop worrying about an alien invasion.

Our atmosphere with 20% poisonous gas is not a very hospitable place unless your species evolved here.

Biological entities are very specific to their environment.

By: Ayti

Ayti — Wed, 14 Jan 2009 17:32:30 +0000

Alien plants yes, but perhaps you'd see a similar, analogous effect at other wave lengths indicating the presence of analogous plants.

If a planet and it's life evolved in the presence of a star of a different color than our own then, looking for a shift in the "red edge" would seem a reasonable line of inquiry. To me at least.

By: BeckyWS

BeckyWS — Wed, 14 Jan 2009 14:00:45 +0000

Ha ha, Dark Gnat got there before me!

By: BeckyWS

BeckyWS — Wed, 14 Jan 2009 13:59:37 +0000

This is very interesting, but it assumes that extra-solar 'vegetation'- by which we mean what, non-intelligent static life?- will use a system of energy gathering involving chlorophyll, or at the least, some system where visible light is absorbed but near-infrared is reflected.
This seems a very narrow view for life signatures to me- how likely is it that something using this precise system will have evolved elsewhere? What about other energy sources like infrared, x-ray or even thermal energy being exploited? How would we look for signatures like that?
I hate to quote Donald Rumsfeld, but there are the known unknowns like looking for a red edge, but there are the unknown unknowns too… we might declare the galaxy lifeless because we haven't found an earth clone, when really we haven't been imaginative enough.

By: Dark Gnat

Dark Gnat — Wed, 14 Jan 2009 13:50:00 +0000

All of this assumes that alien vegetation is like Earths.

Alien plants (if you could even call them plants) may not use chlorophyl or other photosynthesising chemicals. They may not even use visible light as an energy source.

I wonder if it would be possible to predict and find a reflectivity drop in other wavelengths.

We would also have to take into account the atmosphere, cloud cover and how that might affect the results.

By: Mang

Mang — Wed, 14 Jan 2009 13:33:31 +0000

@Neil – I'd always thought it would be difficult given that (1) reflected light from the Earth delivers far more energy than our most powerful transmitters, (2) inverse square law, (3) background noise. The only way I thought it might happen is if the radio/TV was detected as background noise where there shouldn't be any. Forget any idea of reconstructing a signal.

By: Damian

Damian — Wed, 14 Jan 2009 13:12:16 +0000

Has anyone ever tried telescopes frozen to absolute zero? (the lens)

Would there be any advantage? Superconductivity in Telescopes?

Just musing.

By: BlackBolt

BlackBolt — Wed, 14 Jan 2009 12:43:54 +0000

Well, Mang, the "decades" equate to how many LY our radio waves have travelled, the latter supposedly having the speed of light and everything.

By: Neil

Neil — Wed, 14 Jan 2009 12:36:35 +0000

Radio signals would barely leave our solar system, forget them travelling to distant stars, its a myth!

By: Mang

Mang — Wed, 14 Jan 2009 12:15:24 +0000

We've been leaking radio, TV and other signals into space for decades. Has anyone looked at what it would take to identify such signals from planets around stars 60-100 LY away?

By: Mang

Mang — Wed, 14 Jan 2009 10:21:53 +0000

@trux – for exposures of this length a space telescope is needed otherwise there is the small problem of the Earth getting between you an your target for a good chunck of the day.

By: Steve

Steve — Wed, 14 Jan 2009 10:00:18 +0000

Tacitus,
I do agree completely its pointless to hide our emissions.

If another species in our "stellar neighborhood" has seen our little neck of the woods and has any knowledge of our planet, lets just hope the Vogons don't wipe us out for a hyper space bypass

By: fsm

fsm — Wed, 14 Jan 2009 09:24:12 +0000

Nice piece, but :
"The Galileo probe found strong for this evidence in Earth 1990"
A little re-editing needed, maybe?

By: tacitus

tacitus — Wed, 14 Jan 2009 07:57:50 +0000

Dan, think about it. This article explains exactly why it's pointless to worry about alerting aliens on other planets as to our existence.

If they have telescopes large enough and powerful enough, they can see us already! (Well, they can see that there is life on Earth and they can see that there is a technological civilization on Earth too — chemical pollutants and light emissions from the night-side.

We will almost certainly have telescopes big enough to detect these things from light-years away within a century or two, so imagine what an alien civilization with, say, a 5,000 year lead on us in terms of technology. (5,000 years is nothing in galactic historical terms). We have absolutely no hope of hiding our presence from any such advanced civilizations — if they're out there, and if they are close enough (within a few hundred light years) then they've already spotted Earth, and quite likely already know a great deal about the planet we call home.

By: Dan Tillmanns

Dan Tillmanns — Wed, 14 Jan 2009 07:46:54 +0000

Some of the civilizations seen on Star Trek were rather unfriendly and contact with such "people" would be a bad idea.
That's fictional but some are quite possible. Perhaps a bit of caution is called for.

By: trux

trux — Wed, 14 Jan 2009 03:15:39 +0000

I hope that we'll soon see a project similar to SETI@home or other BOINC projects that would link thousands of amateur telescopes into an array, allowing so for hi-resolution observations by amateurs. The number and the quality woud probably not reach those of an array of 150 3m telescopes, but I bet some exciting research could be done anyway.

By: Dave M

Dave M — Wed, 14 Jan 2009 03:14:36 +0000

@alp
The plots show albedo on the Y axis and wavelength from about 300 – 800 nanometers. The plots are based on model output data. The paper explains the model in detail.

You can get a PDF of the paper (which contains the figure at full resolution) at http://arxiv.org/PS_cache/arxiv/pdf/0901/0901.1214v1.pdf

By: Mang

Mang — Wed, 14 Jan 2009 02:08:02 +0000

An 18 week exposure is difficult but I don't think it's impossible. MOST can take 8.5 week exposures

By: alp

alp — Wed, 14 Jan 2009 01:19:37 +0000

Where did the photo of (I assume) Earth and the spectograms come from? I want to see full sized. What is the Y axis of the spectrograms? X axis is wavelength, what is y?

By: Emission Nebula

Emission Nebula — Wed, 14 Jan 2009 00:56:59 +0000

Aaarrrggghhhh!!!! I hate waiting for new awesome telescopes to be made. Being 30 years old I would so love to see continents on an extra solar planet (assuming life goes smoothly for me) before Im dead. Perhaps this is a field I should look into becoming an engineer for.