Where are they? - The Fermi Paradox
The Fermi Paradox, named after Enrico Fermi, put simply, refers to "Where are they?". To be more precise, the Fermi Paradox is the contradiction between the lack of evidence of extraterrestrials and the high probability values of their existence, such as those given by the Drake equation. The main arguments of this paradox include :
1) There are billions of stars in the Milky Way and trillions of galaxies in the Universe each with billions of stars, most of which consist of planetary systems older than ours. With high probability, a percentage of these planets are in the Goldilocks Zone of their star (put simply, a high percentage of planets are be Earth-like).
2) The extraterrestrial civilisations probably will develop interstellar travel.
3) The Milky Way could be completely travelled over the course of a fe million years, if interstellar travel will be what it is currently imagined to be.
According to the aforementioned statements, Earth should have been visited by extraterrestrial civilisations or at least discovered some concrete evidence.
There has been a lot of speculation surrounding this topic, which has led to attempts to explain this paradox as well as arguments against it.
The Drake equation
The drake equation is an argument used to represent the number of communicative, extraterrestrial civilisations in the Milky Way galaxy. The variable N, the number of civilisations, is given by :
Where
- R* represents the average rate of star formation in the Milky Way
- Fp represents the fraction of stars that have planetary systems
- Ne represents the average number of planets that could support life
- Fl represents the fraction of those planets that develop life
- Fi represents the fraction of planets on which intelligent life such as ours has developed
- Fc represents the fraction of these civilisations that are capable of sending signals into space such as radio waves
1) There are billions of stars in the Milky Way and trillions of galaxies in the Universe each with billions of stars, most of which consist of planetary systems older than ours. With high probability, a percentage of these planets are in the Goldilocks Zone of their star (put simply, a high percentage of planets are be Earth-like).
2) The extraterrestrial civilisations probably will develop interstellar travel.
3) The Milky Way could be completely travelled over the course of a fe million years, if interstellar travel will be what it is currently imagined to be.
According to the aforementioned statements, Earth should have been visited by extraterrestrial civilisations or at least discovered some concrete evidence.
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| Enrico Fermi, physicist |
There has been a lot of speculation surrounding this topic, which has led to attempts to explain this paradox as well as arguments against it.
The Drake equation
The drake equation is an argument used to represent the number of communicative, extraterrestrial civilisations in the Milky Way galaxy. The variable N, the number of civilisations, is given by :
Where
- R* represents the average rate of star formation in the Milky Way
- Fp represents the fraction of stars that have planetary systems
- Ne represents the average number of planets that could support life
- Fl represents the fraction of those planets that develop life
- Fi represents the fraction of planets on which intelligent life such as ours has developed
- Fc represents the fraction of these civilisations that are capable of sending signals into space such as radio waves
- L represents the length of time over which these civilisations release detectable signals
Using values for the above terms, the current value for N turns out to be 156,000,000 civilisations.
Explanations for the paradox
- Extraterrestrial life is non-existent/rare
- Intelligent extraterrestrials do not yet possess the technology to send signals into space
- Civilisations are too fart apart in space
- Human beings have not existed for long enough
- Signals released by extraterrestrials are different than what we can trace/recover/detect
- Earth is left alone to develop naturally, something referred to as the Zoo hypothesis
- Extraterrestrial civilisations travel undetected through space and time
- They exist, but unacknowledged (governments covering up UFO incidents)
- No other intelligent species have arisen yet
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