If we are alone, why? If we are not alone, where is everyone?
There should be well over 11 billion planets in our galaxy with a potential to host life, yet all our searches have not found anybody out there.
Yet all evidence so far, seems to suggest life emerging may be a rare event. This is an exploration of the possible explanations for these seemingly contradictory positions.
- Either We are alone: The only intelligent life in the galaxy?
- Or We Are Looking In The Wrong Places?
Either We Are Alone: The only intelligent life in the galaxy?
The Thought experiment: How Can We Explain the Odds?
The Fermi Paradox is the contradiction between lack of evidence for alien civilizations, and it seemingly mathematically so probably there would be many alien civilizations. One explanation is that the odds against life resulting in an advanced are incredibly high, resulting in us being alone. But how can the chances be so low, but us be the lucky ones? Do we need to have done something right, or could it just be luck?
For this experiment, consider ‘Russian Roulette‘, which is a model for any potentially fatal process. Consider 5 billion (200,000,000,000) people all locked in individual rooms unable to observe outside their own room, who each play 100 rounds of Russian Roulette with a single bullet in a 6 chamber gun.
For each round of playing Russian Roulette, there is a 1 in 6 chance or dying, which means a 5 in 6 chance of surviving. So raise 5/6 to the power 100, and multiply by the number of people and you get the number of expected survivors as (5/6)^100*5e9 = 60.
The only people alive to consider their experience have found the game of Russian Roulette has been harmless. They have tried 100 times with no ill effects, and could be expected to regard another round as nothing to worry about. “This Russian roulette nothing to worry about”. If they do find some evidence of all other rooms existing, but having no sign of life, do the decide ‘our gun must have been different!’, or does it dawn on them that statistics says be very afraid?
Now consider that our galaxy has around 200 billion (200,000,000,000 or 200e9) stars which could have habitable planets, with current estimates of around 11billion sun like stars with planets in the habitable zone. Statistically, half of those stars would be older than the sun, as the sun is less than 50% through its life-cycle. So if life began on these habitable planets around each of these sun like stars, it would take a risk to a planet remaining habitable, of an equivalent of risk to the 100 tries of our imagined Russian Roulette to reduce this to only 60 planets where life survives long enough to evolve intelligence.
Does this thought experiment provide an sensible answer to the Fermi Paradox that we have not seen signs of life elsewhere in the universe? It is necessary to examine what we know about planets in the habitable zone, and them actually being habitable, and staying habitable. Review our information about exoplanets, and what evidence do we have for life having survived long periods. Then try to look at realistic conclusions.
Habitable Zone Planets: Life Rarely Lasts In Our Solar System.
I recommend the series ‘The Planets‘ although I have only see the version hosted by Professor Brian Cox, but assume the US version hosted by Zachary Quinto contains the same material. All relevant information about the four rocky planets of our solar system are provided in the first episode of this series.
Ok, it is not a planet, but the sun containing over 99.8% of the mass of the entire solar system, the sun has a huge impact on the planets. The faint young sun would have been providing all the planets with only 70% of the energy they currently receive, back at the time life started on Earth. The entire time the heat from the sun has gradually been increasing and will continue to increase until around 6 billion years from now, when the sun will ‘explode’ and then ‘die’.
The messenger probe provided significant information about the planet Mercury, that allows the following two conclusions:
- the planet originally formed in the ‘habitable’ or ‘Goldilocks zone‘ of the solar system
- Mercury had a suffered a significant impact very early in the life of the planet, stripping away the out layers of the planet, most likely any atmosphere it had at that time, and resulting in the planet being moved to its current position, too close to the sun for comfort.
The ‘Planets’ documentary points out that had this collision never taken place, Mercury could have at one time supported life. But the collision did take place, and before the planet ever could have supported life, so Mercury was never in a situation to support life.
Venus went from potentially hosting life as recently as one billion years ago, to being the hottest planet in the solar system.
When the first spacecraft was sent to Venus, it was prepared for a splash landing, because give the distance from the sun, liquid water seemed likely. In turns out Venus has huge atmospheric pressure, and is the hottest planet in the solar system, even hotter than closer-to-the-sun Mercury. Venus is the same size as the Earth, around the same composition, and back when life started on Earth with the sun only 70% of current strength, Venus at a distance 70% of distance the Earth is from the sun, is thought to have had similar temperatures to Earth today. In fact it seems likely that Venus at an early time, could have been even more suitable for life than Earth. Professor Brian Cox states in the planets documentary, that the temperatures on Venus were once like a spring day on Earth. It is believed Venus had rivers and oceans of water and should have been suitable for life. However, sometime in the first 3 billion years, a runaway greenhouse effect heated the planet well beyond temperatures where life can survive. Climate change turned a ‘spring day’ warmth (the planets documentary) into a furnace at that would melt lead (467C or 872F), and if there ever was life on Venus, it would be most unlikely even evidence there once was life survived.
We are not sure exactly how an Earth receiving only 70% of today’s level of warmth from the sun, had the liquid water to support the origin of life. One thing is clear, a level of greenhouse effect much higher than we see today played a role. The Earth’s climate has managed to largely compensate as the sun warmed, and has dealt with climate changing events such as volcanoes thousands of times more powerful than the Pompeii eruption, asteroid impacts that created massive extinction events, and most likely even times the Earth froze to become ‘snowball Earth’. In fact the most major impact change of climate to impact life, was the change around 500 million years ago that enabled Earth to support life actually on Earth, as opposed on only underwater. For around 90% of the life of the Earth, both surface radiation levels and lack of Oxygen in the air meant the planet was certainly impossible for any life on land. Earth became a planet we could exist on under 500 million years ago.
Despite being around 50% further from the Sun than Earth, Mars originally had at atmosphere rich in greenhouse gasses, and as documented in ‘the planets’, had rivers flowing across its surface for hundreds of millions of years (and we can still see the evidence of that today). 3.5 billion years ago, Mars was a very hospitable environment for life. But the climate of Mars changed as a consequence of losing its magnetic field, and as a result a change (and significant loss) of atmosphere. The greenhouse effect was reduced, and Mars became cold and desolate.
Conclusion: Three Initially Habitable Planets?
It seems most likely our planet has had three habitable planets, even though only one of them is habitable today. The other two fell victim to events triggering climate change, with Mars becoming too cold due to loss of greenhouse gas and Venus becoming far too hot due to too much greenhouse gas. “The story of the solar system is the story of instability and constant change, at least for the four rocky planets” – Brian Cox in the Planets.
The Fragile Balance.
Greenhouse gasses can be seen as the enemy. We need greenhouse gasses, just in a quite precise amount. Without CO2, plants could not ‘breath’. Without greenhouse gasses, the Earth would have an average surface temperate of -18c ( -0.4 F) – reference Brian Cox ‘the planets’ Episode 1, at around 30 minutes.
Yet CO2 in the atmosphere is only 405 parts per million. Less than half of 1%. This is sufficient for plants to breath and for greenhouse gasses to lift temperatures for that -18C to 14.9 degrees Celsius (58.62 F).
That 405 parts per million is a very low level, yet already too much to prevent rising temperatures given the current sun’s temperature. That we have had the exact correct amount seems like a very lucky roll of the dice already – or more likely a balance achieved with feedback, as in something in nature has maintained the balance. However the balance is now down at a very very low limit. Even if we stop some thermal run-away at this time, with an ever warming sun we are clearly running out of time.
The balance we have reached is a very fine line. It does seem amazing we have made it this far when you consider how fragile the balance has become.
Analysis, Unknowns and Risks.
All we know, points to our solar system being unremarkable, and yet our existence is perhaps 1 in a billion. It is human nature to look for assume reasons other than chance for rare outcomes, but we do know it makes no sense to research looking for the special characteristics that enables lottery winners. It is just that statistically these winner will exist. A key way of creating lotteries is the use of a sequence of numbers, each number being similar to a round of the Russian roulette thought experiment.
In nature, not every ’round’ (or roll of the survival dice) has equal probability, and one perspective is that the outcome of many ‘rolls of the nature dice’ are predetermined before the actual ‘roll of the dice’. For example, it can seem that Mars always too small to retain the liquid core needed retain the magnetic field to protect its own atmosphere, so that climate change would result in a loss of atmosphere was not chance, but an inevitability. The counter argument to this would be that even the size and internal heat of Mars was itself a product of choice, as other outcomes such as Mars and Mercury possibly having joined into the one planet would have been possible if a few small early collisions in the solar system had been different. Perhaps if intelligent Martians had developed in time they could have taken steps to protect their atmosphere? Perhaps intelligent Venusians could have taken steps to prevent greenhouse gas runaway on Venus?
It could also be said that the asteroid that hit the Earth around 66 Million years ago, would have been an event predetermined by the exact orbits of all the bodies of the solar system. In the end, with either perspective, there is a chain of probabilities, all multiplied together to give the chances of life surviving long enough to result in intelligent life.
Having the right elements and temperature for life to start seems to not only have happened on Earth, but also on the ‘out of the Goldilocks zone’ Mars and Venus. In fact, most scientists believe we will find that life did exist on Mars in the past if not still today. Life could have existed at one time on Venus, but the planet now is so inhospitable that even traces of early life could not survive.
But despite life starting so early on Earth it took a very long time to reach early evolutionary milestones, and that time was fraught with danger. Throughout evolution there have been extinction events large and small, as change events drove climate change that resulted in extinctions. The most recent famous extinction event, when the meteor hit that ‘wiped out the dinosaurs’ (either with or without the aid of the Deccan traps), resulted in the loss of 75% of species on Earth, and previous events have been even worse. There is evidence each roll of the climate dice carries some risk, but like the survivors of the thought experiment, we do wonder if our copy of the gun simply isn’t working and we are safe, even though probability suggests we should not be confident.
On the best data we have, the final probability of climate remaining stable long enough for intelligent life seems extremely low. Also on the best data we have, appropriate conditions for life on planets in the Goldilocks zone is not rare, since it also appears to have happened on Venus and Mars, the only other candidate planets we have been able to study.
The analysis suggests, the longer the climate is to remain suitable for life, the lower the probability.
We don’t know how often life will start when given the right conditions. We would love to know, and it one of the reasons we search for either some life still being on Mars or concrete evidence of life in the past on Mars. Out current assumption is that given how early life started on Earth, given the right conditions, life will start. But we are not certain.
We could be missing something about how intelligent Aliens would communicate. It could be argued that our lack of discovering intelligent aliens is all due to poor strategy in searching, but again all we know suggests there should be some non-random radio emissions from some alien civilisations, even if they also have another way to communicate.
Perhaps Our Sun Really is Different? All we have learnt so far, suggest with greater and greater certainty the sun is just like other similar stars. Perhaps we are missing something? Somehow Jupiter is unique in lowering the number of asteroids coming our way? (We believe it could be rare- but far from sufficiently rare). Perhaps the sun will not continue to heat up during its life time as is the case with all other stars we have observed?
A Supervolcano? A super-volcanic eruption such as those of the past at Yellowstone could create a volcanic winter, that would remove all concerns about heating related climate change. However while the risk of such an eruption is low, the consequences for humanity could genuinely be as severe as in film. To solve anything, some magic event of an eruption capable of reversing climate change, but not large enough to result in a collapse of civilisation would be required.
While the unknowns should provide solace that catastrophe may not await, there are also risks which reinforce a need for concern. Unfortunately, some of the risks are definitely real. The risks mostly consist of ‘tipping points’, where a rise in temperature triggers an event that leads to a further rise in temperature. Many of these tipping points are listed on the wikipedia page. But here are some that have caught my attention:
- the Eaths albedo, or reflectivity, decreases as we lose surface ice. This means the warmer it gets, the more heat from the sun will be absorbed driving it ever warmer
- There are significant amounts of methane under the arctic permafrost. Melt the permafrost and even more greenhouse gas is released.
- Water vapour is a very effective greenhouse gas, and we do have lots of water. Every degree rise in temperature sees more water held in the air as vapour, magnifying the original rise. There is a point where this process ‘runs away’ as the increase from more water vapour just keeps creating more vapour. This is what is believed brought Venus to its surface temperature of ‘a spring day on Earth’ before greenhouse gases to the current 462 °C; 863 °F .
Or We Are Looking In the Wrong Places?
Over 11 Billion Habitable Exoplanets in our Galaxy?
The other explanation for the Fermi paradox, is that we are simply not seeing the evidence.
As the graph of number of discovered planets around other starts shows, almost all planets we know of were found recently. Clearly, we are early on that voyage of discovery. However, even with only the data we have, we can estimate that there would be 11 billion stars similar to our sun with potentially habitable planets in the Goldilocks zone.
All we can predict is potentially habitable, as we have learnt that planets initially habitable such as Mars and Venus, need not remain habitable. The original definition of the of the habitable zone was too narrow to even include Venus or Mars, but we have learnt more and while we now know the zone is for planets is broader, we also know events can occur which can be ‘end of habitable zone’ for a planet. Analogous to one round of the Russian roulette thought experiment, which ends the wrong way.
We also know that moons can have their own habitable zone, although we have yet to confirm life on moons in our own solar system.
Evidence Suggests Emergence of Life is Not Rare.
This is a question that does not yet have a definitive answer, despite our searches. There are suggestions life may have even started multiple times on earth, either after having first died off, or simply in parallel.
However we are still to confirm the was or even is life on Mars or Venus, despite our suspicions.
Data From SETI
Analysing data from SETI (the search for extra terrestrial intelligence) would appear simple: nothing conclusive. However, a look how well organised SETI are, and the depth of qualifications of the researchers, and the fact that nothing conclusive has been found is in itself conclusive. Either:
- almost no other planet in our galaxy has ever reached a level of technology matching our level of communications
- aliens that have reached a level of technology using our level of communications have only existed for short times
- alien intelligence all use communication unknown to us, and not a single one of them still makes use of radio communication
The Fermi Paradox. They either aliens have never been out there, or are no longer there, of we just can’t see any of them.
Are Photons Misleading Us?
Since soon after the invention of radio in the late 19th century, humans have been creating radio signals and sending them off into space. In theory, with sensitive radio telescopes, we could detect if someone on another planet was doing the same thing, sending radio visible light signals with a patterns that are not found in nature. We have not found anything. However, on Earth, we have been using photons, mostly in the radio frequencies, for just over one hundred years, which is quite a short period of time. We do assume that we will continue to general such signals in the future, but what if discover a better method of communication? More specifically, what if better methods of communication are soon discovered by every civilization within a few hundreds years of discovering radio?
The key fact is, we are primarily looking for radio frequency, or other frequency photons, in order to detect life. But for all we know, this could be a complete misdirection, and we will soon discover that no civilization as ever spent a long time sending out photons.
Carl Sagan estimated that is civilizations were not exceedingly rare, it would be reasonable to expect as many as 1 million civilizations in our galaxy. We have been sending out radio waves for far less that one one millionth of the time Earth has been around, so unless it is normal to keep sending radio waves, chances could be against even one in a million civilizations sending radio waves right now, which would be one million civilizations, and we are the only one sending radio waves. It is definitely possible we are looking using a flawed technique.
Evidence Of Aliens
UFOs/UAPs and the Alien Technology Paradox.
For aliens traveling to Earth to produce the phenomena observed as UAPs, requires the aliens to have technology that used principle of physics we do not understand. Yet almost all analysis of the logistics required for aliens to travel, is based on our current understanding of physics, and the nature of any visit is based on the assumption that our understanding of physics, which we have had for 100 years or 1/40,000,000th of the life of Earth would be common in amongst alien civilizations.Me: The Alien Technology Paradox.
There is an underlying assumption that our current understanding of the physics of the universe is basically complete, despite this understanding only being introduced around 100 years ago by Albert Einstein, and us having no explanation for dark matter, dark energy and how to resolve gravity with quantum mechanics.
It seems we are confident this level of knowledge is quite complete despite that we recognise that 95% of the universe is totally unknown to us and we do not fully understand the 5% we know something about. Are we really certain that our knowledge will remain at this current level for a significant time?
The ‘tidal pool excursion’ hypothesis.
Consider what I call the ‘tidal pool excursion’ hypothesis. Consider some fish in a costal tidal pool. “I have seen another sighting of an alien face floating above the surface of the pool”, says fish1. “Those phenomena are not real”, replies fish2. “If they were real aliens, and they made it all the way to our pool, they would want to meet our leaders and communicate with us. Besides, it is not possible for a face to just float above the surface”.
Aliens who possess the technology to travel to Earth, may be able to do so for something as simple as a school excursion, to study alien life. The idea of trying to communicate with that alien life (us) could seem pointless, as we are seen by them as we see the fish in the pond. There is no suggestion this hypothetical example is what is really happening, but it does provide an example of one of countless possibilities.
Extraordinary claims: The requirement for extraordinary proof.
Carl Sagan is credited with the quote: “Extraordinary claims require extraordinary evidence“.
This reflects the reality that although there is arguably a lot of evidence of aliens, none of the evidence is unambiguous or sufficiently extraordinary to meet the criteria required. If compelling evidence is found, then we may look back at current evidence in a different light, since the claims will no longer be extraordinary. People may say, “It should have been obvious”. But right now, it is not obvious. No evidence so far is sufficiently compelling, but that does not mean it is definitely not evidence. We just don’t know.
Carl Sagan is also famous for Sagan’s Paradox.
To argue that the Earth was being chosen for regular visitations, Sagan said, one would have to assume that the planet is somehow unique, and that assumption “goes exactly against the idea that there are lots of civilizations around. Because if there are then our sort of civilization must be pretty common. And if we’re not pretty common then there aren’t going to be many civilizations advanced enough to send visitors”.Sagan’s Paradox
However, Sagan’s paradox itself exhibits the Alien Technology Paradox, in the assumption that a society such as our current society, despite having existed for less than 1 millionth of the life of the earth, would be commonly found within his estimated 1 million societies. Further the assumption is that interstellar travel is based on principles of requiring the energy interstellar travel would require using our current technology.
This section being discussed in WTF, UFO/UAPs are real?
If you search ‘Oumuamua‘ you will find multiple theories on this visitor from outside the solar system. Is it a rock, or as Avi Loeb, chairman of Harvard University’s astronomy department has suggested, an alien spaceship? The reality is this object was already too distance when we realised the puzzle it presented. Again, while it is rather odd, there is no ‘extraordinary proof’ this strange object is alien.
Years from now, we may look back and think, “we should have realised, it was obvious!”. But what we will feel we should have realised is still ambiguous.
If we are alone?
It seems being alone is only likely, if life almost always comes to an end before intelligence arises. From the data we have so far, a suitable climate lasting long enough is most likely limit to civilizations developing and reaching the level we have on Earth. We are proof that it is possible to reach the level where radio signals will be produced. If the reason we don’t find any is because we are alone, then that suggests nowhere else has anyone managed to find a solution to outlasting the natural span of stable climate on their home planet. Either this challenge is mastered often, or almost never.
If we alone have survived this far, the answer is ‘almost never’, and it would seem we are running against the odds, and eventually there will come a roll of the climate dice where tipping points kick in and take earth of the ‘inhabitable’ category. We should have time to solve this problem, as we may be able to maintain the fragile balance until the sun heats a little more. Or it could be soon as we have started a roll of the climate dice ourselves. We have started climate change, and we may not be able to stop it, but we can change how risky the roll of dice becomes. Do we really want to roll that dice ourselves? In the words of the famous philosopher, Clint Eastwood: “Are you feeling lucky?”
If there are aliens?
If there are aliens, then at least least there is a precedent for survival. The fact that we have not seen them so far means we must be ‘looking in the wrong place’ and photons are not the path forward in terms of communication.
What can we be sure of?
There are not lots of societies out there, who reached our current stage of development, and then remained at that level. Either societies progress and stopped sending our radio waves, or they died, possibly before even reaching our level.
this section still to being updated.