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ALIENS: WHERE ARE THEY?

With regard to possible extraterrestrial life in the universe, physicists Enrico Fermi and Michael H. Hart raised the question, “Where is everybody?” [Ref. 1].

This is known as the Fermi paradox.

THE FERMI PARADOX

The Fermi paradox begins with basic astronomical observations:

• Our sun is an average star. The Milky Way galaxy in which we live is a spiral galaxy consisting of over one hundred billion (100,000,000,000) stars [Ref. 2].
• Our galaxy is just an average-sized spiral galaxy. Astronomers estimate that there are over a hundred billion galaxies, with approximately a septillion (1,000,000,000,000,000,000,000,000; that’s 24 zeroes!) in the universe.
• Our sun is relatively young. It’s about 5 billion years old. Scientists believe our universe to be about 14 billions years old.

It seems like there are too many stars in the universe for intelligent life not to form on many other planets. Even if the speed of interstellar travel is small compared to the speed of light, and even with the several millions of years needed for intelligent life to develop in a favorable solar system, it has been estimated that a galaxy can be colonized in a timescale on the order of tens of millions of years (which pales in comparison to the age of the universe).

But if aliens have colonized the galaxy, where are they?

That’s the Fermi paradox:

• Statistically, it seems likely that extraterrestrial life should have colonized the galaxy, including visits to earth.
• But there is no clear sign of alien life on earth. (Or is there?)

SOLUTIONS TO FERMI’S PARADOX

Several possible solutions to Fermi’s paradox have been proposed.

Most of these fall into one of two categories:

• The conditions by which life developed on earth are extremely rare, so much so that extraterrestrials have not yet colonized our galaxy.
• Aliens have indeed visited earth, but either our governments or the extraterrestrials themselves have prevented this from becoming widespread knowledge.

INTELLIGENT LIFE IS VERY RARE

One possibility is that intelligent life is so rare that despite the huge number of stars in the universe, intelligent life is unique to earth or at least extremely rare.

Here are a couple of possible explanations which have been suggested to explain this:

• The Great Filter [Ref. 5]. Perhaps intelligent life tends to be very short-lived, running out of needed resources, suffering from overpopulation, meeting with natural disasters or diseases, or destroying itself through wars or apocalyptic weapons.
• Rare Earth Hypothesis [Ref. 6]. This hypothesis rejects the mediocrity principle, stating that the conditions for life on earth are quite atypical. Earth has a significant axis tilt (23.5º), a very large moon, a favorable distance to the sun, a favorable atmosphere, a moon the right distance from earth to produce significant tidal effects, etc. On top of the astronomical and geological requirements, the conditions also need to be favorable for the biology, and even under favorable conditions it might be rare for life to begin and for intelligent life to develop.

ALIENS HAVE VISITED EARTH

Another possibility is that aliens have indeed visited planet earth, but this knowledge hasn’t become widely publicized.

Following are some possible explanations which may explain why it hasn’t become public knowledge:

• Zoo hypothesis. The earth might be a galactic zoo or park, for example. Just as we have national parks to preserve wildlife, the earth might be such a planetary reservation. This might be to allow earth the opportunity to continue its natural development.
• Government cover-up. Perhaps governments are either aware of extraterrestrial visitors to earth or are actually in contact with aliens, but have covered this up from the general public.
• Lack of interest. They may be too busy with other affairs, or too different from us, to have any interest in contacting humans on earth.
• Too advanced. Aliens who can visit earth may be so far advanced in comparison to humans that they don’t consider it worthwhile to establish contact with us, or perhaps they fear that sharing technology at this stage in human development could threaten life on earth (we might not be ready for a sudden improvement in technology). They might be as far advanced compared to humans as humans are advanced compared to monkeys, for example.
• Irreconcilable differences. They may be drastically different from us, making communication very challenging or not worth the effort. Even on earth, we see great diversity in life forms. Intelligent extraterrestrial life that may be able to visit earth or at least communicate via long distance may be as different to us as a giraffe is to a fish.
• Here undetected. Aliens may be visiting earth, or even present on earth, but keeping themselves fairly undetected.

ANCIENT ASTRONAUT THEORY

The Ancient Aliens series on the History Channel has recently popularized ancient astronaut theory.

Ancient astronaut theory and its growing popularity can be traced back to Erich von Däniken, author of Chariots of the Gods? [Ref. 7] which raises several questions about ancient civilizations, for which mainstream science may not have a convincing explanation.

Maybe aliens have visited earth in the distant past, and maybe there is evidence to show this.

Ancient astronaut theory even raises the question of whether or not modern day humans may be in some way extraterrestrial, e.g. perhaps ancient aliens had a hand in genetic development.

This idea intrigues me. In future articles, I will be searching for possible evidence of ancient aliens here on earth.

REFERENCES

1. “Where is everybody?” An account of Fermi’s question. Jones, E.M., 1985.
2. “How many stars are in the Milky Way?” Howell, Elizabeth, 2014.
3. “How many stars are there in the universe?” Cane, Fraser, 2013.
4. “Looking back to the cradle of our universe,” JPL, 2014.
5. “The Great Filter—are we almost past it?” Hanson, Robin, 1998.
6. Rare Earth: Why Complex Life is Uncommon in the Universe, Ward, Peter D. and Brownlee, Donald, 2003.
7. Chariots of the Gods, Däniken, Erich von, 1999.

CHRIS MCMULLEN, PH.D.

Author of:

• A Visual Guide to Extra Dimensions
• An Introduction to Basic Astronomy Concepts
• The Improve Your Math Fluency series of workbooks

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