The Fermi paradox, the Drake Equation, and the search for ET life, are all related closely to each other. The Fermi paradox states that given the amount of alien life forms that should be looking for us, (given by the Drake Equation explained below) this should mean we have had an extra terrestrial visit by now. We have not had such a visit (this point is of coure debatable) so therefore we have a paradox. To explore this, let us take a look at the Drake Equation. The amount of said civilisations is predicted by:
N = R x F(p) x F(e) x F(l) x F(i) x F(c) x L
which is …
The number of civilisations =
(rate of star formation)
(fraction of those stars with planets)
(fraction of those planets with an environment suitable for life)
(fraction of those planets with environments that actually does develop life)
(fraction of those lifeforms that develop suitable intelligence)
(fraction of those intelligent lifeforms that develop technology capable of interstellar communication)
(the length of time these civilisations spend trying to communicate)
You are probably wondering what sort of answer N comes out as. There simple answer is there isn’t a real value for N, as the parameters in the Drake Equation are far too variable and unkown to give reliable results. Estimates for N come out from N= < 1 to N = > 1,000,000. In otherwords there could be anywhere from no one else but ourselves in the galaxy, to over a million other civilisations. Let us then, for a moment, consider the implications of the higher end estimates, as it is these that give the rise to the Fermi Paradox (as if we are the only ones in the galaxy then it is obvious that we won’t see anyone else so there would be no paradox in the first place).
There have been many solution to the Fermi Paradox put forward over history. They range from sensible to outragous, but as with any theory, we must explore all the possibilities, even those that are unlikely. So here is a sample of some of the more interesting solutions.
1. We are alone
This perhaps is the most obvious conclusion to jump to, however it differs from the N= <1 estimate, in that the Drake Equation predicts other life forms, however there just plainly isnt any. We are alone in the universe. Many people are keen to point out that the chances of life arising at all, let alone to thrive as it has on Earth, is highly improbable. This leads to some interesting questions, such as, if life is so improbable, then why are we here? This is where those whole follow theism will cry out God, but many (perhaps most) scientists, including myself, are dissatisfied with using a deity as an answer to scientific problems. Instead many follow the idea of the Anthropic Principle, found in its weak and strong forms. We see the ‘miraculous’ conditions for life fullfilled only because we exist to observe them. This is the Weak Anthropic Principle.
2. We have had extra terrestrial visits, in the form of UFOs and abductions
For many decades, especially so since the 1950s, the world has been abuzz with UFO sightings. Many people associate UFOs with ETs, however these people must remember that UFO merely stands for Unidentified Flying Object, and does not neccessarily imply alien spaceships. In fact ask any skeptic and they will point out the vast numbers of UFO sightings related to government test crafts and astronomical phenomena. Now while the vast percentage of UFO sightings are likely down to either government projects (such as the stealth aircraft, which anyone could be forgiven for thinking is an alien spaceship), astronomical phenomena (such as Iridium Satellies and meteors), or the bane of telescope users everywhere- the infamous Chinese lantern, it is perhaps also likely that at least 1% of these sightings cannot be explained by such mundane events. So here perhaps we have another answer to the Fermi Paradox- a small percentage of UFO sightings are genuine aliens.
To discuss every UFO sighting since the 50s would be a vast deviation from topic here, not to mention be an impossibility. Likewise we cannot possibly hope to explain the hundreds of sightings every year, so we must come to a descision, as scientists, on whether one single unexplained light in the sky = proof of alien life, or whether we must leave it until we have solid proof, either in the form of a crash landing, or, fingers crossed against this one, an alien invasion. The vast majority of science is proved or disproved on theories. Either a theory is proved right, in which case it must both agree with previous observations and predict new observations, or it is proved wrong, in which case it does not stand up to the test. This last case is even true if it fails just one test or observation. A theory stands only if it is true everytime. Therefore if we apply this to the case of UFOs, then we can say that the 1% of UFO sightings per year that are unexplainable most certainly do not prove the existance of alien life, nor do they solve the Fermi Paradox. And in any case, unless the UFO became an IFO (Identified Flying Object), how would we know what it was in the first place? The whole point is that it is unidentified, and science does not like things it cannot identify.
3. We live within a false reality created by another alien race
This theory is rather more philosophical than scientific, as there really is no way of knowing the answer to this. Like with UFO sightings, it is not very scientific to say something is true just because you haven’t seen otherwise- we don’t really know what’s on the inside of a black hole, but to quote Dr Sheldon Cooper, it most certainly isn’t a ‘man with a flashlight looking for a circuit breaker.’ Therefore saying that we live in a false reality created by aliens isn’t a very good theory, in fact it isn’t a theory at all, it’s just speculation. If we cast this aside for the moment however, what would be the motivation for such an action? Are we merely an entertainment system created by an advanced alien race, much like the episode of South Park Cancelled? More to the point, is there actually any way of knowing otherwise?
This last question, if any, is the one to ask ourselves, as it is the one that can bring us closest to proving or disproving the ‘theory.’ If we were to attempt to find the outside of the reality, how far would one have to look to break out? In otherwords where are the ‘big screens’ placed? One way of supporting (i say supporting as it would hardly prove the theory) is if we found an area of space where the laws of physics suddenly changed or broke down. An area where Pi does not = Pi, an area where elements have completely different properties than we observe at any other time. This is an unlikely situation indeed. Through the electromagnetic spectrum we can observe many millions of light years away from us, and what we observe agrees with what we see on our own earth. For this ‘layer’ of false reality to be real, it would have to ecompass the entire observable universe. Not only this, but it would have to be expanding along with the universe, the energy to do which would have to be equal to infinity. This is impossible. No matter what your technological prowess, it is impossible to control an infinite amount of anything. Of course you could argue that we are basing all of our previous scientific knowledge on false information, fed to us by our game masters. Doing this however takes us back to our starting point of speculation, and as i stated at the beginning, there is little point in dwelling on speculation.
4. We live in a ‘protected planetary zoo’ – we have been put here for study by another alien race
If we do not live in a completely created reality, do we then live in a protected site, away from the prying eyes of other races? Perhaps we are an interstellar zoo, put here by an alien race to be studied, perhaps even protected for our own good? These are the thoughts of those who have mused on the possibilty of Earth being within an interstellar zoo. We don’t have to look far to see examples of these within our own existance. We as humans have (finally) discovered the importance of protecting certain species from the wear and tear of the modern and expanding world around them. To stop these species from becoming extinct through actions such as deforestation and illegal hunting, we have created ‘safe zones’ for them, synthetic habitats where they can be both monitored and protected. The main point here is that those animals, if the park managers are doing their jobs well, will not be aware of their homes being within a bounded and protected environment. It doesn’t take much imagination to figure up reasons why an alien race would want to keep us within an interstellar zoo. Space wars, advanced civilizations battling for galactic supremecy, it’s all the stuff of cheap sci-fi novels, but could it be real?
Perhaps. It is very unlikely of course. As i’ve pointed out, If we take a giant leap from scientific reasoning, we can propose just about anything. However unlike the false reality theory, we don’t have any obvious disproving features that can help us out. Just as the Tigers aren’t aware of the cameras, we presumably wouldn’t be aware of whatever technology we are being observed by. Perhaps we could go even further into sci-fi territory and link UFO sightings as proof of our park rangers, here to check up on us and make sure we havn’t done anything silly, like destroy the planet in a nuclear war. But again such speculation belongs to novelists, not scientists, so we can forget about this theory until we see the cameras.
5. Science prevents cross-stellar communication at this point in time
Bringing us quickly back to scientific reasoning, can we apply our current knowledge to shed any light on the Fermi Paradox? The answer, you will be pleased to hear, is yes. Below i shall give some of the more scientific answers put forward.
Light Speed Travel is not possible
In the early part of the 20th century, Albert Einstein stunned the world with his twin theories of Special and General Relativity. These theories have since revolutionised the way we think about the Universe and its physics, and has shown us some wacky outcomes along with it. One of these outcomes, shown by Einstein’s famous E=mc^2, is that nothing can travel faster than the speed of light. In fact nothing but electromagnetic radiation can actually match the speed of light, making it the fastest phenomenon in the Universe. Let me take a moment to explain how this relates to the Fermi Paradox.
As E=mc^2 shows us, energy is = to mass X the speed of light (C) squared. If we rearrange this equation we can also see that as speed increases, so does our mass. This is surprising enough, but we can go further than this to say that as our mass increases, so does our need for energy to push our imaginary spacecraft to ever faster speeds. So in order to propel our spacecraft to the speed of light (C), we would thus need an infinite amount of energy, which is of course an impossibility.
Now let me state the distance to our nearest stellar neighbour – Proxima Centauri. This star lies at a distance of 4.26 lightyears. In other words it takes over 4 years just for the light of Proxima Centauri to reach our eyes, and similarly, if we could achieve the impossible and travel at lightspeed, it would take our spacecraft 4 years to get there. But we cannot reach lightspeed. In fact it is incredibly difficult to travel at even a few percent of the speed of light, and well beyond our current capabilites. The Voyager spacecraft, currently on its way through the very edges of the solar system, will take many thousands of years to reach the next star on its path. The end result of all of this is that firstly, unless an alien race was vastly superior to the human race (which perhaps isn’t as great a possibility as you think. See the next heading), any would-be space travelllers would take an incredible amount of time to reach us. The (developed) human race is only several thousand years old. Let us assume that as our race was dawning, another alien race, situated at the other side of the galaxy, was setting off on its journey to Earth. These travellers have been on their long road for as long as the advanced human race has existed, and yet they have only travelled a mere fraction of the complete distance required.
Perhaps then, we as intelligent humans just haven’t been around for long enough to encounter any ETs.
The Galaxy has been ‘sterilised‘
Space is a dangerous place. As human’s we are incredibly fortunate to live under a protective atmosphere which filters out most of the lethal radiation coming from our Sun. It is ironic that the very thing that gives us life, could just as easily fry us had the development of the Earth been a little different. This however is a rather pointless statement to make. Those whole follow the Weak Anthropic Principle would be quick to point out that the reason we are lucky enough to live on a world that can support us, is because if the conditions were any different, we wouldn’t be alive to observe it. There has been much debate whether the extreme odds that led to our watery earth can be found elsewhere in the galaxy. Even considering the ‘miraculous’ events, our world still lies on a knife edge, with danger at every turn.
We live in what is called a Habitable Zone, or sometimes referred to as the ‘Goldilocks Zone.’ If you imagine a circular band, enclosing the Sun and lying at a certain distance, with a certain width, this band is the Habitable Zone. The width of the band depends on the conditions found within it. Too close to the Sun will lead to conditions being too hot for liquid water, and likewise too far from the Sun and it will be too cold for it to exist in its liquid state. The area within these two extremes is the Habitable Zone, lying at the ‘sweet spot’ in the Solar System. As you would expect, the Earth lies in this zone, which extends outwards almost to Mars, and inwardsd not quite to Venus. If we look at the conditions on Mars we see that it averages freezing cold temperatures of around -50 degrees celsius. Turning to Venus we see temperatures over 450 degrees celsius, much to hot for liquid water to exist.
You may think, living in the sweet spot, that humans have the future safe. This unfortunatly however, is not the truth. Stars evolve with time, getting brighter and hotter with age. This means that areas on the near side of the Habitable Zone will leave the band, becoming too hot, and likewise areas on the far side will enter the band, and warm up. This gives rise to the band moving outwards with time, which is referred to as the Continuous Habitable Zone. This will then lead to the Earth leaving the Habitable Zone, which will lie in the ‘hot’ area between the zone and the Sun. This is bad news for humans (though don’t worry, this won’t happen from many millions of years) as the Earth will loose its habitability, at least in the form that we are aware of.
The Continuous Habitable Zone is a nice example of the ‘dangerous existance’ answer to the Fermi Paradox. The conditions needed for life will not last forever with the same area. Civilisations are then left with two options- colonize, or die. But as previously shown, the technology needed to move large populations to other solar systems is incredibly difficult to develop, perhaps even impossible. If an alien civilization, on the brink of extincton by an increasingly hot star, has not developed the required level of technology to move them to even the nearest star, then they will cease to exist. This race for technology is something that we as humans must consider if we are to survive the destruction of our home planet.
There is of course the possibility that an alien race, sufficiently developed, will have the means to move their civilization and colonize the next world or rocky moon out in the solar system, if they were lucky to have such a candidate. This way they are not escaping their ultimate fate, but are instead ‘buying time.’ The downside to this is the next world will inexorably suffer the same fate as its inner companion. Perhaps we can go further then into speculation and consider a race so advanced that it can continue to move outwards, colonizing further and further rocky bodies. Or perhaps this race has the means the live under sweltering heat or freezing cold as they please. Assuming this to be true will still not remove such a race from danger. There are plenty of other dangers lying in space that could destroy this civilization.
Stars of high mass end their lives in a powerful explosion called a supernova. Supernovae release similar energy in mere seconds than our Sun will release in its entire lifetime. It is not hard to see how this could affect the parameters of the Drake Equation. Any civilization, no matter how advanced, living on a planet within the supernova’s system, would be instantly destroyed, as would any beings living around other stars unfortunate to be caught in the wave of lethel radiation. Supernovae are an important part of the Universe. High mass stars create what are called Metals, which are elements heavier than Helium (not to be confused with our usual term for metal). These metals are flung out into the cosmos to be recycled into new generations of stars, enriching the metalicity of the Universe with time. It is these metals that give rise to the likes of Carbon, an extremely important element for life. However just like Supernovae are essential for life, yet again like our Sun, they can just as easily make life extinct.
Death of extremely high mass stars can give rise to a Hypernova, leading to what is referred to as a Gamm Ray Burst. Gamma Ray Bursts are the most powerful phenomena in the galaxy, dwarfing standard supernovae by comparision. If such a burst happened within our area of the Galaxy, all life within its beam of radiation would be destroyed. Around 2 of these are seen per day within the Universe using the Compton Gamma-Ray Observatory. Could these lethal events be another reason for an empty Galaxy? Again we do not know for sure. Certainly they will be responsible for ‘steralising’ the area within their beams of radiation. Another interesting outcome could be that Gamma Ray Bursts force out a ‘level playing field’ for galactic civilisations. Perhaps, if mass extinctions happen on regular basis, there are no other civilizations more advanced than humans? Perhaps we represent a new generation of advancement, born anew after the demise of older, more unfortunate races, wiped out by GRBs?
There are many many answers to the Fermi Paradox, and entire books could be written about them (which they have, and here would be a good time to give credit to Mr Stephen Webb who wrote the excellent Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life where i researched a lot of my ideas), however i shall conclude with a statement i have used severel times throughout this article.
Science does not like speculation, and the Drake Equation, despite looking scientific, is far too speculative to be useful. Answers with a variation of a million are far to wide for us to even say whether the Fermi Paradox exists or not, and many would point out that a paradox based on a ‘grey area’ topic such as extra terrestrial life isn’t a paradox at all, it is just a hole in our knowledge.
Despite this, fans of the Drake Equation need not dismay. With our ever increasing array of scientific methods and technology, we are whittling down the unkowns of the equation. Exoplanets are being discovered in their hundreds, and through spectroscopic measurments, we can discern the composition of their atmosphere. Probes are being sent to ocean bearing candidates such as Titan, Europa and Ganymede. SETI radio astronomers are keeping a vigilant watch for any suspect transmissions, and soon the Voyager spacecrafts will be the first human probes to leave the Solar System.
The more we look the better chance we have of finding what we seek. I think it will only be a matter of time before the Fermi Paradox is resolved.
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