Say that there are intelligent people on a planet orbiting Alpha Centauri, not only that, say that they have a S.E.T.I. program virtually identical to ours listening to the stars for radio broadcasts.
What was the oldest broadcast from Earth, whose broadcast was strong enough, that would could be taken as signs of intelligence by the Alpha Centaurians?
In other words, were the first radio broadcasts strong enough that they wouldn’t dissipate and die out after 4 light years of travelling through space?
“say that they have a S.E.T.I. program virtually identical to ours”
So, if they have an equal sensitivity to our S.E.T.I. program, what will be the first message that they will be able to interpret as signs of intelligence?
Some of the earliest commercial radio and television broadcasts in the late 20’s and early 30’s would have been easily strong enough to be detectable by an Arecibo-type radio telescope from 4.3 LY.
something to think about for this question is nasa used transmiting equipment on the viking landers no more powerfull then a walkie talkie. it was actually cheaper to build powerfully senstive equipment on earth then to spend the money on rocket power to send more powerfull transmitters. however nasa knew what signal to look for on what frequency.
My hazy memory of the numbers is at odds with what Q.E.D. says there… I seem to recall hearing that no human transmission to date could be detected with current human technology four lightyears away. I’ll see if I can find numbers.
Sorry, I meant that our SETI program is not a single thing, it’s a bunch of different receivers scanning different bands at different sensitivities, and a whole bunch more variables. I just think you needed to provide more information to properly answer this.
I’d like more information on QED’s claim as well. What wattage are you assuming for these radio broadcasts? 50,000 watt clear channel stations did exist by the 1930s (I’d have to check on the 1920s). A few 500,000 watt experimental stations were created - I believe there was one in Cincinnati, and Mexico had fewer restrictions on power than the US - but I’m not sure that the timing for these is right.
I realize that our spacecraft use extremely low wattage signals, but the signals are directed and their positions are known, and even so we lose the signal a good ways short of Alpha Centauri.
I’d also dispute that commercial television broadcasts from the 1920s or 30s would be receivable. All the attempts I’m familiar with were fairly low power. Also remember that most tv at the time used scanning disk technology that would be difficult if not impossible to reproduce without knowledge of the source. Electronic scanning did exist, but was barely viable until the late 1930s.
I read that topic, and the first thing that I thought of was, why was Mork only referencing very recent stuff. I mean, even if the sitcom assumed an audience unfamiliar with a lot of old-time stuff, you’d think Robin Williams’ character would have thrown in more references to past Earth stuff they’d received on Ork, more than I recall him doing anyway.
Then again, maybe they were more accurate than I thought - perhaps their SETI system could only receive certain stuff. It would dissipate after a while, after all.
(Dollars to donuts a similar thread gets starts in Cafe Society now
That site doesn’t really answer the OP’s question, though. That we send out a major signal today doesn’t say anything about when that signal became major.
The “levels of our own radio/TV” are given here:
We certainly didn’t transmit anything like that in the 1920s or 30s. FM and TV signals were essentially negligible until after WWII.
Although they mention Marconi, they don’t get into the issue of how much of AM leaks through the atmosphere. Nor do they talk about short-wave transmissions, which were a major part of radio from an early date.
I said FM and TV signals were negligable. And in previous posts I already noted that Cincinnati had a 500,000 watt AM station, but wondered how leaky AM signals were because if the signals didn’t penetrate the atmosphere they wouldn’t be much good on the next star.
Depends largely on atmospheric conditions. There are conditions under which the atmosphere becomes largely transparent to longwave EM. Of course, I don’t know, and probably can’t prove one way or the other, if such conditions ever occurred at during the time the station was operational.
Yes, I’ll grant the question is still open, but I believe we’re getting closer to a concrete answer. Anyone want to take a quick trip to Alpha Centauri?
Turning the question around (having not yet ploughed through the SETI site), are we therefore certain that:[ul][]nobody within 5 LY is broadcasting TV (or indeed anything more advanced/efficient)[]nobody within 40-50 LY is broadcasting military radar or better nobody in the galaxy has swept the heavens with a Gigawatt beam continuously for the last 100,000 years?[/ul]How depressing.
That’s cause we’re still the only savages left in the universe still using radio, for heaven’s sake. I mean come on, it’s just a step up from beating on freaking drums!
Carl Sagan had the aliens seeing first Hitler broadcasts (in his book Contact), but he missed a much better “first”
Long before Hitler’s broadcasts, Hugo Gernsback (seminal publisher of science fiction, after whom the “Hugo” awards are named) used to broadcast TV signals out of New York. Back in the 1920s.
Don’t know if any of them were powerful enough to survive noise-free enough to be received by aliens.
Nikola Tesla made several extremely high-power CW, AM broadcasts into space. These started in the 1890’s…and I don’t know how they were modulated. I have read that Tesla tried to signal Admiral Peary’s 1909 North Polar expedition-again I don’t know the details. So perhaps, the bug-eyed monsters are this very minute, puzzle dby the rantings of a long-dead serbian genius!
Tesla did some very-low-frequency experiments in the early 20th century that traveled long distances, but I don’t know how well these would be propagated outside the atmosphere.
He also claimed to receive interstellar signals in 1899, presumably the same type of noise that would plague later radio astronomers. Nobody believed him then, and it’s hard now to know what if anything he heard. Somebody may be conflating this with sending signals, I suppose.
You have to be very careful with claims about Tesla. All too many of them are in the same league with his building a death ray that caused the Tunguska explosion.
