ASTRONOMER: We Think We're Close To Finding Life On Another Planet

Don Reid said:

The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence.[1][2] As a 2015 article put it, "If life is so easy, someone from somewhere must have come calling by now."[The following is an essay I wrote for another forum years ago when the subject came up.

When I consider the unlikely chain of events and requirements which made Earth the life friendly habitat that it is my vote goes to the proposition that we are rare. Just consider: It would be amazing if we discovered intelligent extraterrestrial life. It would be a turning point for our species. On the other hand if centuries and then many millennia pass without human beings discovering any sign of extraterrestrial intelligent life that would be more than just amazing. It would be mind boggling in its unlikeliness and the depth and breadth of its implications. However the Fermi Paradox might explained by more mundane though still astronomical considerations. This is just my own take on the subject, but I have thought about it. Our only example of an environment capable of supporting life is Earth. It is fun, and sometimes productive to speculate about silicone based life, life that thrives on airless dry asteroids, living stars or whatever suits our fancy, but the only environment we are certain can sustain life over eons is that of Earth. Examining a few of the factors which has made Earth so well suited for our sorts of life could help explain the Fermi Paradox. A life supporting planet needs to orbit a single star. The planet needs to stay within the Goldlilocks Zone or habitable zone where significant amounts of water remain liquid. If the odds of finding a planet orbiting around a single star and staying within the habitable zone are the same as the odds of an agile kid walking one-half mile along a railroad rail without slipping off then the odds of finding a planet which stays within the habitable zone of a system where two or more stars orbit about each other is about the same as the odds of a tired old man hopping on one leg for two miles on a railroad rail without falling off and breaking his damn hip. Theoretically possible, but very unlikely. The majority of the stars in the universe are binary or multiple star systems. Single star systems make up much less than half of all stars. The star needs to have an output of energy which remains reasonably stable. The luminosity of the sun varies a bit in a cyclical way, but a whole class of stars, Cepheid variables, pulse, doubling then halving their brightness in a as little as one Earth day or longer. A planet having an ice age followed by tropical heat every day might bear life, but I can’t imagine that life evolving enough complexity to support a brain capable of interstellar communication. On Earth itself it is easier to list what is believed to have happened to make our planet so life friendly so that we can factor that into what it would take to make another Earthlike environment. The following is current, peer reviewed, mainstream theory. Early in Earth's existence a Mars sized plantet,Theia, collided with the Earth striking a glancing blow. This speeded up Earth’s spin rate greatly. Earth’s still rapid rate of spin on its axis is vital to the existence of the remarkably strong magnetic field which protects we Earthlings from the ionizing charged particles of the solar wind and other cosmic rays. Venus, Earth’s similar sized sister planet has a dense iron core like Earth, but it takes Venus 234 Earth days to turn once on its axis. The magnetic field of Venus is so weak as to be virtually nonexistent. The mars sized planet’s collision with Earth blasted billions of pieces of both planets away to never return, but it also provided enough mass to enlarge Earth and give us our huge moon. Earth’s moon is the 5th largest in the solar system, but in regards to the relationship of the moon’s mass to the mass of the planet around which it revolves it is the Solar System champion, and this is important. A planet’s precession describes how much it is tilted on its axis and how much it “wobbles” on its axis over time. Earth has an average 23.3 degree tilt of its axis relative to the axis of the Sun. The Earth’s wobble on its axis is only + or - 1.3 degrees over a 41,000 year cycle. That is an incredibly stable, regular axial spin. A planet’s precession is a product of all significant gravitational forces acting on it. Some planets or moons wobble like a child’s spinning top as it is winding down to stop. If Earth did that the coldest places on Earth might at the geographic North and South Poles this year, at Nome, Alaska and a matching antipodal point next year and at San Francisco and a matching point on the opposite side of the world a few years later. I suspect such a world would harbor life, but under those harsh disruptive conditions would intelligent life capable of interstellar broadcasts evolve? The Earth owes its remarkably stable axial rotation to the presence of our huge moon, revolving out there acting like a governor on an old steam engine tied to Earth by gravity as surely as if it were held by God’s own cable. The two planet pile-up described above plus having a huge moon which immediately after being formed was orbiting as closely as twelve or fifteen thousand miles from Earth resulted in almost all of the Earth’s atmosphere being blown away or being stripped away by the big moon and lost forever. That was a very good thing. Again consider Venus, Earth’s sister planet. Venus and Earth have a very similar composition of elements except for their atmospheres. Venus is a bit smaller than Earth so you might expect it to have a bit less atmosphere. Nay, Not so. The atmospheric pressure on Venus at an average surface level is ninety-two times as great as Earth’s atmospheric pressure at sea level. When the wind blows on Venus it moves over the surface with the friction and erosion effects of a heavy liquid instead of what we know as air. Had Earth not been stripped of most of its air by our planet’s history it’s reasonable to believe it would have been even worse here. In a nutshell, without the stable, solo star, the two planet wreck, the glancing blow which speeded up Earth's axial rotation to give us the best magnetic field in the neighborhood, the huge moon and the planetary collision to rid Earth of almost all its atmosphere and again the huge moon to stabilize Earth’s precession, and only Albert Einstein’s smarter little sister knows what else, Earth would be a vastly different planet than the home we know. As previously stated the only natural environment we can be certain is capable of supporting life over eons and evolving intelligent life is Earth. Surely that is also possible in millions of other sorts of environments all over the universe. Surely.... But we don’t know that. What if it takes as unlikely a string of fortuitous happenstance such as those which shaped Earth to create a really good environment for life to exist for billions of years of years and evolve intelligence? If good environments for life are as “special” and dependent on unlikely events as Earth’s appears to be there could still be millions of them among all the stars of the universe, but then it’s a hell of a big universe. It could be a very long time before we encounter extraterrestrial intelligent life and a dreadfully long time before we meet a life form we really like and want to hang out with.

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Nicely written however in order for us to meet these extraterrestrials the only way that can happen is if either or both of us find a way to exceed the speed of light. Short of that perhaps there are worm holes and beyond that we have the thought of not one universe but rather metaverses. And then once we consider that we have to consider the fact that there are multiple dimensions beyond the few of which we know. I think it is something that makes for many PhD dissertations because to me it is naive to think that as we look out to the depths of and fringe of the universe as we see it that extraterrestrial doesn’t exist. Plus we only know of life as we understand it it. To wit, life cannot exist without the presence of water.Bottom line is that this is the fodder that merely fuels speculation because as you said we are but a blue marble in this huge cosmos. Intergalactic travel as we know it makes the thought impossible to conjure. To me it is not a matter of if but rather when we discover it. It has to happen before the earth is chewed up by a black hole or destroyed by an asteroid. And then there is the theory of the big bounce which if you believe should arrive once the universe begins to contract.However before the force of gravity causes contraction all life will be gone wherever in the cosmos it existed. Fascinating to me as well. Is it the Big Bang or is it the Big Bounce ?