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The Drake Equation vs. the Fermi Paradox

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Richard S. R.
The Drake Equation vs. the Fermi Paradox


“Sometimes I think we’re alone. Sometimes I think we’re not. In either case, the thought is quite staggering.” —R. Buckminster Fuller

The Nobel-winning physicist Enrico Fermi is best known for his creation of the world’s first nuclear chain reaction during World War 2’s Manhattan Project. During a casual conversation in the summer of 1950 with fellow physicists Edward Teller, Herbert York, and Emil Konopinski, as they were discussing recent UFO reports and the possibility of faster-than-light travel, Fermi asked, “But where is everybody?”

This legitimate question, now known as “Fermi’s Paradox”, was based on the age of the Universe:
• Big Bang ~13.8 billion years ago (BYA)
• First supernovae generating heavy elements ~13.6 BYA
• Sun starts shining ~4.6 BYA
• Liquid water on Earth ~4.4 BYA
• Very primitive life arrives on dry land ~3.5 BYA

So the possibility of life on other worlds had a 10-billion-year head start on life on Earth. Yet, despite all that lead time, we’ve seen absolutely no evidence that it exists. Why not? That’s the paradox.

Astronomer and astrobiologist Frank Drake was fascinated by the question and his inquiries into its possibilities got him known as the father of SETI (search for extra-terrestrial intelligence). In 1960, he originated Project Ozma, which used radio-dish antennae in an attempt to detect the 21-centimeter frequency of hydrogen photon emission around nearby Sun-like stars. Since then, many increasingly powerful projects to detect ET radio signals have been begun, looking at many more stars. None of these lasted more than a couple of years or ever found anything.

In the absence of hard data, Drake wanted to take a stab at the likelihood of intelligent life being within galactic communication range, so in 1961 he developed what has come to be known as the Drake Equation, which considers a variety of factors that might influence such a condition. Here are those factors:
R∗ = the average rate of star formation in the Milky Way Galaxy
fp = the fraction of those stars that have planets
ne = the average number of Earth-like planets per star that has planets
fl = the fraction of planets that could support life that actually develop life
fi = the fraction of planets with life that develops intelligence
fc = the fraction of civilizations that generate detectable signals
L = the length of time for which they generate them

The original estimates plugged into these factors yielded a huge range of numbers, anywhere from 20 to 50 million. More refined estimates since then have generated results ranging from 1 (us) to about 15 million. There are just too many unknowns in all those factors to come up with reliable results. (For comparison, there are about 400 billion stars in the Milky Way Galaxy, so even the high-end estimate represents only 0.004% of the total.)

But have any alien civilizations detected our radio signals? Well, any that might’ve done so would have needed to be within a relatively small sphere, centered on Earth, with a radius of 124 light-years, since we’ve only been transmitting radio since 1900. (124 light-years is small relative to the galactic radius of about 53,000 light-years; there are only about 60,000 stars that close to us.)

Besides, what would they be listening for? During humanity’s short use of radio, we’ve employed 3 different techniques: AM (amplitude modulation), FM (frequency modulation), and XM (digital), each of which sounds like noise to the other 2. And there’s no assurance an advanced civilization would even use the electromagnetic spectrum, as opposed to something like neutrinos, gravity waves, or whatever dark energy might be.

Notice that none of the above says anything at all about actually meeting an intelligent alien race in person, which would require not merely interstellar communication but also interstellar travel, something made horrendously difficult by the limiting speed of light. (“300,000 km/s – not just a good idea, it’s the law!”)

This will be a virtual meeting conducted via Zoom. A link will be sent out at 6 PM on the day of the event to people who’ve RSVPed.

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