On the radio

Please consider donating to Behind the Black, by giving either a one-time contribution or a regular subscription, as outlined in the tip jar to the right or below. Your support will allow me to continue covering science and culture as I have for the past twenty years, independent and free from any outside influence.

I probably should have noted this earlier, but I am about to begin another two hour stint on Coast to Coast with George Noory. Should, as always, be a lot of fun.



  • the Boodge

    Listening now!

  • Greg

    Robert, it was a pleasure speaking with you on CTC last night. I was the geologist calling from San Diego County re exoplanet detection. ‘Behind the Black’ is a great resource and I thank you again for your great work following all these topics, from the inspiring (real scientific discoveries and exploration of space) to the downright terrifying (on many PC college campi). I suspect you’ll have no shortage of issues to cover in the next few years.

  • And I thank you for your kind words about my work. You should check out the ebook of Genesis: the Story of Apollo 8. I think you’d like it.

    I imagine the two caves you visited were the commercial caves Kartchner and Colossal. Both worth a visit, though as a caver for me the stuff they have off tour is far more fun to see!

  • J Fincannon

    I liked hearing you on the C2C show.

    At one point you were wondering why we haven’t heard from aliens given we have been broadcasting for 70 years.
    This article makes the point that the limit is not likely to be what you think.
    They say that Earth radio started in 1900 so at the time of the article the theoretical circle of signal travel so far was 110 light years. But they brought up the very important point of the way those signals propagate is not like a laser beam, but radiated as a sphere. Thus the signal energy drops off as the inverse of the square.
    “Another way to think of it, is that the strength of a radio signal will be only 1/4 as great once you are twice the distance from the source. At ten times the distance, the strength of the signal would only be one hundredth as great. Or as they put it….
    “Because of this inverse square law, all of our terrestrial radio signals become indistinguishable from background noise at around a _few light-years_ from earth (!!!). For a civilization only a couple hundred light-years away, trying to listen to our broadcasts would be like trying to detect the small ripple from a pebble dropped in the pacific ocean off the coast of California – from Japan.”

    But while it is possible to focus and amplify the signal, the problem becomes who do you point at? Choose wisely, because there are a lot of stars and we don’t have an infinite amount of energy.

    Also, I like the following old webpage, although I have not checked the numbers. At least he provides the data/calcs for someone to do so. It would be nice if this kind of checking appeared in a more formal paper.

  • J Fincannon

    Also, I recall a question about the concept for the Earth space elevator being raised to you by a caller. The caller made it sound like someone was building a tower. No, that is not how it works. Actually the proposal was to lower a line from some distant point (geosynchronous altitude). Since it is going around in a 24 hour orbit, it will hover over a point on the Earth surface at the equator. Some have proposed to attach it there, maybe on a ship. Problems abound with the concept for Earth, especially avoiding debris (how does one move a massive cable to avoid a fast approaching piece of debris or a satellite). You are right that it is technically too difficult at this time, although perhaps it is reasonable to propose for the Moon. Someone has suggested using a retrieved asteroid in the Earth Moon libration point as the counterweight to support the elevator, although it is still a lot of cable.

Leave a Reply

Your email address will not be published. Required fields are marked *