If you were on the outside looking in; an extraterrestrial out seeking life in the universe, what would you see? Would life be evident?
We all are so worried about the answer to does life exist in the universe that we seem to have overlooked the possibility that right now someother race is debating the exact same thing - the existence of anyone else in the universe.
Right now “we” are seeking other life by looking for lights on other planets, why? Because the Earth puts off a glow, shouldn’t they?Unfortunately as good as our technology (and telescopes are more and more amazing), most are so far away that they appear as a tinylight to start with.
Assumming that an extraterrestrial is as advanced as we are, if they don’t live too far than they have likely already found us. Our signature from space is too obvious. AND if they are more advanced and a tad farther, well there are clues. As a matter of fact we should and do take clues from what we are leaving for others to understand what we need to look for.
OKAY, so specifics. If junior stole the ‘rents’ spaceship for a joyride and he is just on the edge of our atmosphere, maybe he takes a few snapshots to show his buddies back home of our lights and then they laugh at the pollution and basically all the stuff we had done to make our planet less habitable.
Of course, suppose they are a bit further and a bit more advanced. To us the distant worlds are but dots but perhaps their telescopes or some other device we have yet to invent is able to see us as not a dot with the reflection of the Sun, but see into our atmosphere, see the colors of the gases. Otherwise they’re stuck with the ‘usual methods’.
When so far away that Earth appears as a tiny point of light there are really very few possibilities to work out if life exists here or not. In order to examine an Earth size planet from afar the first consideration is to check out the atmosphere.
One Method is to examine the shadow of the Earth during a lunar eclipse. First of all a lunar eclipse doesn’t place ones eyes at risk in the way a solar eclipse does, now does it require as many additional extras in order to view.
A lunar eclipse occurs when the Earth passes between the Moon and the Sun and basically is visible anywhere the sky is dark and obviously unobstructed or clear. So during this time if one were to focus a the High Resolution Spectrograph (which any society similar to ours would have access to) onto the Moon the Moon inherit high reflectability will allow the Earth’s spectrum to be seen as if in a mirror. The spectrum is a band of colors that make up visible light (think rainbow). Certain elements will emit different wavelengths of light and absorb others – basically each element has a signature. By using the spectrograph and examining another planet as it makes transit across the face of its parent star ET can find out about our atmosphere or we can find out about theirs. (In the case of Earth, comparing elements found in the Earth’s shadow when the Moon was clear of it.)
SO what else can ‘they’ find out about us? After eliminating some effects generated by the ocal atmosphere, ‘they’ can then examine the spectrum of colors that was produced and see what molecules are visible. Of course all that comes up as present doesn’t necessarily mean that is the atmosphere of the planet. Running this exact experiment of our own spectral signatures during a lunar eclipse shows a lot of nitrous oxide and that was due to a volcano (in the Antartica-Mount Erabus) which while not active was a major contributor.
Now as stated looking for lights on a planet that is reflecting light or hanging in the shadows and is the size of a speck of dust probably will reveal little to nothing. How different the light appears wil vary at different wavelengths – sometimes muted by certain atmospheric conditions or phenomenom and other dominating the appearance of the Earth. Also if ‘they’ had looked during the crescent Moon that too would change it; it’s appearance would be twice as bright. (Clouds have a tendency to reflect better during the crescent Moon than other time, and polar ice reflect in much the same way.)
Honestly, I have no idea what ET hopes to find though I suspect ozone would be good no matter what. Since it’s apearance is often shown by an ultraviolet light, perhaps that is the aliens guide.
So what is ET really thinking when he reviews our atmosphere thanks to the spectral signatures? He/She was thinking that this third rock from the Sun can’t harbor life – what with all that Oxygen and Nitrogen and only a trace amount of many others. There is no way anyone could survive with out Methane! We look for different signatures to represent possible life then perhaps ‘they’ would. Could be that’s a good thing!