Sunday, January 10, 2010

Range of Interstellar Radio

SETI has been in my news feed recently, which behooved me to track down my favourite discussion about picking up alien transmissions. I've never seen the actual physics all mathed out anywhere else, and the reason for this dearth seems obvious from the results. The analysis is basically complete, so I just have a few disjointed comments.

They simply use the word 'detect,' which I take it to mean something like 'differentiate from background noise,' which is backed up by comments like, "In keeping with the estimates of Aburto and Woolley, the Signal to Noise Ratio for all calculations was taken to be 25 since this is between the SNR of SETI@home (SNR=22) and the maximum SNR used by Project META (SNR=33). "

Especially striking is the graph showing how large your dish needs to be to pick up human TV signals from Alpha Centauri or Vega. A little extrapolation shows that at nearly all of the stars in the galaxy you require an effective dish well over a billion metres wide. Billion's a nice big round number, don't you think?

If I were a journalist I would now have to decry this outrageous waste of tax dollars. Presumably, this is supposed to stop outrageous wastes of tax dollars. I find it to just be a waste of outrage. The kind of people who fund SETI, if forced to stop, are not likely to suddenly wake up, find their heads, and screw them back on. They'll just make the exact same mistake in some new and interesting way. In short, that cash was effectively flushed down the drain the moment it left the taxpayer's hand.

I'd also like to highlight:

"beacon signals- These non-leaked signals would be intentionally designed to attract the attention of observers in the direction of Earth. If there are advance civilizations that choose to make themselves known in this way, then it is possible that present SETI efforts may one day produce a positive detection. However, these beams must be aimed at Earth at a time when we are listening for a positive detection to occur."

Aiming a signal at Earth from most of the galaxy would be difficult, especially if they're not already aware we're here and looking for it. This alternative stacks unlikelihood upon unlikelihood.


Anonymous said...

Daniel: Never thought to make such simple estimations, of course, now that you told me it is obvious: we need a billion meters antenna to listen to Alien Jazz. Hum... Nice number, Billion.

Personally I always thought SETI was a complete waste. Taxing is wasting as the taxer values the money much less then the taxed as Austrian Economics puts it, a complete crime. If they valued money that much, they would work to earn it, not force someone to give it to them.

And I am almost sure there is no other life in the Universe. Much like the Eden Garden was surrounded by a volcanic wasteland, the Earth, surround by forsaken solar system, hoter than hell or colder than winter on eternally frozen Antartica.

On another topic, loved your comments on black hole formation, I thought it myself long time ago, and it is wonderful to see corroboration.

Alrenous said...

Hello, Daniel.

Independent corroboration is indeed nice.

A nitpick; you can't exactly say it's a crime, as the standard is for criminal codes to define these things so badly that they don't even need a specific exception for taxes. Immoral, sure, but not a crime.

Daniel said...

Dear Alrenous,
Dont commit the crime of letting politicians dicting the meaning of words. That is absolutely frightening.

Alrenous said...

Being immoral is worse than being a crime, precisely because I must define 'crime' as a breach of the actual written codes of law.