I'm a believer. Not a believer in life among us on Earth, but a believer in life out there, somewhere in the cosmos. It seems like a certain amount of stigma is attached to saying you believe in alien life, but it makes perfect sense. In actual fact, it's more ridiculous to think that life DOESN'T exist elsewhere in the universe. Here is my reasoning, I hope you enjoy it.
Our solar system is home to millions of species of life. Our planet is perfectly placed around our sun to be just the right temperature for life to form, the planet core is made of the right materials and our planet spins at just the right speed to produce a magnetosphere to guard us from radiation from the sun, our planet is just the right size for gravity to keep a hold on our atmosphere while allowing us to walk around freely. Disregarding the life present on our planet itself, our situation is remarkable and surely unique in the universe... or so most people would think.
The fact is, our solar system is one of 300 billion within our Galaxy. In our Galaxy itself, there are 300 Billion suns for planets to orbit, and within our universe there are close to 500 billion galaxies. Some galaxies are smaller than ours, some much much larger, and the number vary greatly. The figure of 500 billion galaxies comes from a recent computer simulation by scientists in Germany using images collected from the Hubble deep field.
The most important thing is none of these. The most important thing comes from a very important equation outlined by Frank Drake in 1961, known as the Drake Equation, and it isn't a number. The Drake equation is used to find the number of active extraterrestrial civilisations in the Milky Way galaxy that are able to communicate with earth. The journey of finding the variables and calculating this equation leads to many places, and many answers, but in my opinion, only one real conclusion.
The parameters of the equation are as follows:
R* = the average rate of star formation in our galaxy = 7
This number changes dramatically over a great length of time, but we are talking millions of years. Within the past few million years, this number has stayed fairly stable. Current estimates from NASA come back at around 7 per year.
fp = the fraction of those stars that have planets = 1+
Due to the way in which Stars form, there is usually a great amount of debris left orbiting stars afterwards. This is how planets form; accumulation of debris in space crushed together into a sphere... a new planet. Microlensing surveys performed in 2012 estimate that every star will have at least 1 planet as a rule.
ne = the average number of planets (satellites may perhaps sometimes be just as good candidates) that can potentially support life per star that has planets = Minuscule
This one is a fairly complicated one, and it incredibly difficult to measure. We can deduce based on the Kepler space mission in 2013 that as many as 40 billion earth-sized planets could be orbiting within the habitable zones of stars the size of our sun. 11 billion will be orbiting stars almost exactly the size of our own. As the minimum number of stars is our galaxy stands around 100 billion, the value of fp*ne is around 0.4. On it's own the value of "ne" would be tiny. The value depends greatly on the balance of resources on the planet itself, which is very difficult to measure over such a great distance. It also doesn't take into account any Moons of larger planets which may support life.
fl = the fraction of the above that actually go on to develop life = 0.13
Again, incredibly difficult to measure, but this number should be very high. Life on earth began very shortly after the earth became capable of supporting it. Clearly, we are biased, as we are basing our knowledge of life purely on one planet that we know sustains it; our own, but in 2002 a team of scientists at the University of New South Wales estimated the value to be greater than 0.13, based on knowledge of planets older that one billion years, and the time it took for life to form on Earth.
fc = the fraction of the above that release detectable signs of their existence into space = 0.1
This one is another complicated one as you would think it relies on the extraterrestrials purposefully trying to communicate with other life in the universe. This is not the case. A great amount of earth communications via EM waves leak into space, and may be detectable by other life. We have no estimate for this one, but the original hypothesis in the 60's was around 0.1, meaning 10% of intelligent life will be capable of communication with others in the universe.
L = the expected lifetime of such a civilisation for the period that it can communicate across interstellar space = 304
This was estimated first to be 420 years, but was re-calculated by Michael Shermer as 304 years by basing the result purely on 28 civilisations of humans that have lived since the Roman Empire. The problem here is that we do not take into account that as each civilisation falls, their technology may be passed to the next (some areas of Italy still use sewage systems created by the Romans, for example). As a minimum, we will use 304.
The Result
This is where things get really complicated. So far we have made so many assumptions that our value will be far from accurate. In actual fact, the real result for the Drake equation goes from results close to zero (which makes no sense, as the value should be greater than 1 as we count ourselves as being part of the result) all the way up to 36 million.
The Drake equation was never meant to be a serious equation used to gauge the number of possible life sources in our universe, it was simply an equation to garner more interest in the subject itself, but the results show something far more interesting.
The fact is that despite the assumptions we made while trying to find an answer to the equation, the assumptions were based on real experiments, and real data that we didn't just pull out of a hat. The numbers are there, and they speak of a universe that could range from sustaining very little life, to a universe teeming with it. The fact is, the answer we get is not relevant next to the way that we get to the value - each part of this equation tells a different story that extends beyond scientists simply looking for an answer. The huge number of possibilities, the history of our own planet, and the fact that this equation only takes into account life within our own galaxy...
I'm a believer because i believe that the numbers show something which is undeniable. I believe that the numbers show that it is far more likely that life does exist, and the probability is calculated using real observations, models and close estimates. This is the way in which science works, and considering how our civilisation has grown and evolved in the relatively short time we have spent on this planet thanks to advances in science, that should be enough. There may still be a chance that we are alone in the universe, but that chance is small... almost meaningless.
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