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Consider SETI – Where Is Everybody?

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Should we consider SETI a failure? Is radio astronomy our best tool for discovering intelligent life in the vast universe?

We have been searching for extra terrestrial intelligence for a long time. A few “wow” moments but no hits. Our main search tool for a century has been radio, and massive SETI efforts really ramped up over the past few decades. Still nothing, however.

If you study the work of Drake and Sagan, you can estimate a reasonably strong probability that life is out there. But then there’s the Fermi Paradox: if the probabilities are high, where is everybody? Truth is we really have no idea. SETI is a neat intellectual and technological exercise, the ultimate needle in a time-space haystack.

SETI has mainly focused on radio astronomy in the “water hole“, a region of electromagnetic spectrum around 1.42 GHz selected based on assumptions about what an alien civilization would do. They would select a radio frequency based on a well known source (emissions from universal common elements like hydrogen and hydroxyl, the components of water). By coincidence, these emissions occur in a part of the spectrum very low in atmospheric, galactic and cosmic background noise. So, we have good reasons to focus SETI in this radio band.

Our biggest challenge in doing SETI is the same as for most ham radio operators: radio frequency interference, or what scientists call anthropogenic RFI. A typical SET listening session of four hours will record 25 million signals or candidates. Automated analysis classifies 99.8% of these signals as RFI. You then have remaining 50,000 signals to analyze for ET by hand. Turns out these are all RFI, as well, or a few natural sources.

Perhaps our problem is we spend too much time listening for ET and not enough transmitting. If everyone is assuming everyone else is sending an intentional signal, and no one actually sends one, well you get the idea. But active SETI poses its own risks and of course, huge time delays waiting for a response.

Consider SETI – DIY Radio Astronomy

SET@home is discontinued. But radio astronomy at home is getting easier. Receivers and dishes are no problem. You can easily repurpose an old satellite television parabolic antenna, ideally in the 3-5 meter diameter range. A lot of SDR receivers cover microwaves including 1.42 GHz. Some are really inexpensive like the RTL-SDR or SDRplay RSP units. You will need to buy or build a feed horn and low noise amplifier – not that hard or expensive.

Here’s a quick look at how to build your own radio telescope. Probably the hardest part is building the rotator.

Something to consider in 2021.

One comment

  1. Randy Hollingsworth says:

    John – Interesting take on SETI. I think the biggest fallacy with SETI is the assumption that an advanced civilization are using radio waves to communicate with. We assume that they will because we are. But what if radio is just another communications technology that will be surpassed in the future by something better – like radio eliminated smoke signals, flags, telegraph, etc. If radio is only used for a couple of hundred years and then discarded, the chance of us picking up a signal from that short a time frame is nearly nil.

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