The Physics Police

The Physics Police

Tuesday, May 14, 2013

Zeta Rays

I'm going to complain about talk radio for a bit. On the May 10th episode of the NPR show Science Friday, host Ira Flatow offered a hypothetical blank check to Jill Tarter, and this was her reply:
... I'll take your check, but I wouldn't spend huge amounts on [SETI], because we couldn't guarantee success. It might be Zeta Rays that we should be looking for. I don't know what Zeta Rays are. It's a technology we haven't yet invented.
She is grossly overstating scientific ignorance in an attempt to create an interest in the mysterious nature of SETI. Selling science with ignorance defeats the purpose. Why would any alien use Zeta Rays, when Light Rays are already the perfect tool for communicating over interstellar distances?

No other particle can ever be discovered which travels farther on less fuel. No other particle can be discovered which travels faster. No other particle can ever be discovered that is easier to create (if it were easier, we'd have found it by now). Now, let that last parenthetical sink in a while.

Obviously, any message intended for us will, be light. The questions remain:

  • Which frequencies of light?
  • How might information be encoded?
  • Which direction should we look?
  • How long might the signal last?
  • How strong might the signal be?

All of these questions are interesting, unlike Zeta Rays, and have answers that fit into Ira's question.

  • More money means more frequencies. Build new telescopes that are sensitive on a wider range of the electromagnetic spectrum!
  • More money means more processors. It takes lots of computer time to check for different kinds of signals in telescope data. I'm sure SETI could find use for a few dozen petaFLOPS!
  • Why not look at every star? There are techniques for obtaining spectra for multiple stars at a time. The technique is expensive, but it could enable continuous monitoring of tens of thousands of stars. Also, space-based radio telescopes; how come the Russians have one but we don't?
  • With a blank check, we could setup a trust fund to keep SETI going forever. If SETI technology was improved to the point where we could closely examine a thousand star systems per second, it would take a decade to look through them all. SETI is going to take a long time!
  • With a bit of cash, SETI can detect even very faint signals. The Ooty Radio Telescope can detect 1 watt radio station located 10 million km away in space, and it was built in 1970!

Forget about distinguishing sufficiently advanced technology from magic. Communication isn't about magic. It's about common sense. In this case, we're talking about sense common to every responsible member of the galaxy.

It isn't rocket science. It's just optics, at low frequency.


  1. why wouldn't sentient beings use gamma ray pulses, laser communication. i believe the current probe sent to scan the moon (usa, 2013) is transmitting data via laser. also, it seems one can store more data in a gamma ray, also photonic computers, hologram crystals most likely will use these/this.

  2. Laser communication is good for short range because it's directed, and therefore power-efficient. There is a branch called OSETI which searches in the optical spectrum.

    However, dusty regions of interstellar space are transparent to long-wavelength radio and infrared radiation but opaque to shorter-wavelengths, including gamma rays.

    You can see the motivation for preferring radio wavelengths. So can aliens.

    In SETI, getting noticed is the first order of business, bandwidth is an afterthought. You can always have a simple message in radio that refers the receiver to another message on a higher frequency.