FEATURE: The Drake equation, How many civlised planets are there in the Galaxy

Forty years as an astronomer have not quelled my enthusiasm for lying outside after dark, staring up at the stars. It isn't only the beauty of the night sky that thrills me. It's the sense I have that some of those points of light are the home stars of beings not so different from us, daily cares and all. Who look across space with wonder, just as we do?

Frank Drake

The Drake equation is a famous equation for trying to estimate how many Technological civilisations there might be in the universe, when you look at the size of our galaxy with its billions upon billions of stars around witch many exoplantes orbit the fact is that we simply cannot be alone as the only sentient beings in the cosmos.  However as The Fermi Paradox asks why, given the seemingly endless amount of stars in the night sky, we have not heard from another intelligent race yet.  The simple answer is we don’t know.  Now don’t get me wrong on this I don’t believe that mankind is visited by little green man or even that what happened at Roswell was anything other than a botched military exercise but, I like many better men before me including the grate Carl Sagan himself believe that we are not alone.  The only question is how many other species are out there, and, this is where the drake equation comes in.

The man himself, Frank Drake.

First put forward by Frank Drake in 1961 the equation identifies the specific factors thought to play some role in the development of such civilizations.  There is no unique answer to the equation but it is a generally accepted tool amongst the scientific community to examine these factors.

The equation runs like this:

Where N = the number of civilizations in our galaxy with which communication might be possible.
R* = the average rate of star formation per year in our galaxy.
fp = the fraction of those stars that have planets.
ne = the average number of planets that can potentially support life per star that has planets.
fℓ = the fraction of the above that actually go on to develop life at some point.
fi = the fraction of the above that actually go on to develop intelligent life.
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
L = the length of time such civilizations release detectable signals into space.

to give an answer to this equation I'm going to hand over to a much better man than myself.  the late grate Carl Sagan:

 

 

FEATURE: Did E.T phone home in the 70's

The wow signal

The Fermi Paradox asks why, given the seemingly endless amount of stars in the night sky, we have not heard from another intelligent race yet. And it’s a good point; 55 years of scanning the sky for any signals we have not picked up even the slightest whisper, murmur, or extra-terrestrial hiccough.  Except  for  just once.

On the 15^th of August 1977 a strong narrowband signal was picked up by the aptly named big ear radio observatory  in Delaware, Ohio the signal bore all the hallmarks that one would assume in a signal of intelligent extra-terrestrial origin. 

Now sadly defunct The big ear was, well, big.  A vast, static, Kraus telescope that relied on the rotation of the earth to work. The telescope consisted of vast aluminium ground plate 150 meters by 85 meters (around three times the area of a football pitch) running from north to south, near the middle of its north end there where a pair of receiving horns that pointed south. They where the focus of a huge paraboloidal reflector that was 110 meters by 21 meters standing across the southern end like a massive I-max cinema screen.  This reflector received the signal bouncing off a tilt table reflector spanning the north end, so as the earth rotated the big ear swept the sky in a single line. So the telescope picked up the wow signal for the full 72 seconds it took for the earth to rotate.

The wow signal expressed as a graph.

Since there was no automated computer analysis in 1977 the data had to be read and sorted through by hand.  Jerry Ehman was the SETI volunteer tralling through the data, when he saw a signal some 30 times the strength of normal back ground noise he cricled the data and wrote Wow! In the margin, to this day we call the signal the wow signal.

The big ear.

The signal it’s self was very strong, up to 30 times the background strength of space and formed a perfect bell curve represented by the alpha numerical string of characters 6EQUJ5, witch translates as 6 14 26 30 19 5, times normal. The signal rises with 6EQ and falls with UJ5 all hypreberly aside the wow signal remains the best contender for an alien signal.

The reason that we even consider it to be a signal of extra-terrestrial origin has to do with the wavelength that the signal was received on.  Called the hydrogen line or waterhole by astronomers the frequency of 1420.356 the reason we look to the hydrogen line for alien signals is because hydrogen is the most abundant element in open space it makes sense that any extra-terrestrials would use the frequency to transmit. No earthly transmitter civilian or military is allowed to transmit on this frequency so there is no chance that the signal was deflected from a piece of debris in orbit.  The patch of sky the signal seemed to originate from (the area around Sagittarius) seems to be completely blank sky and indeed after some 100 or more attempts to retrace the same patch of sky we are yet to find the signal again. So we know that the signal can not be of earthly origin. We also know that the signal can not have come from an natural phenomenon like a pulsar because of its perfect bell curve like path when mapped as a graph. Likewise instrument malfunction can be discounted as the equipment was tested and proved to be in working order. Application of Occam’s razor leaves one, amazing, conclusion that mankind was contacted ether on purpose or by accident in the late seventy’s… at least that’s one theory