by neufer » Fri Sep 30, 2016 2:57 am
Boomer12k wrote:
You are an extraterrestrial... you are overseeing Earth... you are from Light Years away... you really going to use....Radio????? Our radio signals dissipate about 1.5-2 light years out, before it blends in with the background radiation....NOBODY is watching Lucy....
Our radio signals dissipate about 1.5-2 light years out, before it blends in with the background radiation for the resolution of Low-Frequency Array (LOFAR). Double the receiving antenna size/resolution and the signal to noise improves by a factor of 4. (The signal could be further improved by watching all the reruns.)
http://www.space.com/2533-listening-ets-television.html wrote:
Click to play embedded YouTube video.
<<The first episode of "I Love Lucy" was broadcast sometime on October 15, 1951. Given that stars in our galactic neighborhood are separated by about 4 light-years, it's easy to figure that roughly 10 thousand star systems have been exposed to "I Love Lucy" in the past five decades.
This possibility was evidently on the mind of Abraham Loeb at Harvard University, who recently noted in the New Scientist that a radio telescope being built to study distant galaxies might also be able to pick up ET's TV. The so-called Low-Frequency Array (LOFAR), a telescope consisting of 25 thousand tent-shaped antennas spread across Holland and Germany, can be tuned to frequencies under 250 megahertz. This is a spectral range far below what's usually searched by SETI, but it's the band in which much of your local television is broadcast. And maybe theirs, as well.
So how realistic is this? Could LOFAR really pick up "I Love Zork"? To answer that question requires doing some numbers. First, we reverse the situation, just to see if tuning in remote TV makes sense.
Imagine that there are alien couch potatoes 55 light-years away who, bored with their own Fall lineup, have constructed a LOFAR-style antenna in hopes of picking up "I Love Lucy's" debut. Hunky TV transmitters on Earth belch out a few hundred thousand watts of power. That energy is not beamed in all directions equally; most of it is aimed around the horizon (which, of course, is where the audience is). Because of this slight beaming, the effective transmitter power is a bit more: let's say a million watts, to keep the math simple.
OK, how strong is that signal by the time it reaches our putative alien audience at 55 light-years distance? Not very. The megawatt broadcast washes over ET's world with a power density of about 0.3 million million million million millionths of a watt per square meter, which is not exactly a scorching signal. Actually, only about a third of that transmission power is in the "carrier" - the part of the broadcast that's very narrow in frequency and easily detected. So knock that piddling power density down by another factor of three if you want to know the strength of the easily detectable part of the transmission. (Of course, if they only find the carrier, they won't get the picture and sound. But Lucy's jokes might not appeal to aliens anyway.)
Could their LOFAR-style antenna find that carrier, thereby indicating that a program was on the air? Well, engineers have computed that at the frequency of VHF television, LOFAR will have an effective collecting area similar to that of the 305-meter diameter Arecibo antenna in Puerto Rico.
That's big. That's brawny. But not brawny enough. In our SETI experiments at Arecibo, we could find a signal if it were about 0.1 million million million millionths of a watt per square meter. That number, you will notice if you count up the words, is a million times bigger than the "I Love Lucy" carrier at 55 light-years. The aliens' LOFAR would be inadequate to detect the broadcast by a factor of a million, a not entirely negligible amount. Simply stated: LOFAR couldn't hear it.>>
[quote="Boomer12k"]
You are an extraterrestrial... you are overseeing Earth... you are from Light Years away... you really going to use....Radio????? Our radio signals dissipate about 1.5-2 light years out, before it blends in with the background radiation....NOBODY is watching Lucy....[/quote]
Our radio signals dissipate about 1.5-2 light years out, before it blends in with the background radiation for the resolution of Low-Frequency Array (LOFAR). Double the receiving antenna size/resolution and the signal to noise improves by a factor of 4. (The signal could be further improved by watching all the reruns.)
[quote=" http://www.space.com/2533-listening-ets-television.html"]
[float=right][youtube]https://www.youtube.com/watch?v=MrbJ7_Am7GA[/youtube][/float]<<The first episode of "I Love Lucy" was broadcast sometime on October 15, 1951. Given that stars in our galactic neighborhood are separated by about 4 light-years, it's easy to figure that roughly 10 thousand star systems have been exposed to "I Love Lucy" in the past five decades.
This possibility was evidently on the mind of Abraham Loeb at Harvard University, who recently noted in the New Scientist that a radio telescope being built to study distant galaxies might also be able to pick up ET's TV. The so-called Low-Frequency Array (LOFAR), a telescope consisting of 25 thousand tent-shaped antennas spread across Holland and Germany, can be tuned to frequencies under 250 megahertz. This is a spectral range far below what's usually searched by SETI, but it's the band in which much of your local television is broadcast. And maybe theirs, as well.
So how realistic is this? Could LOFAR really pick up "I Love Zork"? To answer that question requires doing some numbers. First, we reverse the situation, just to see if tuning in remote TV makes sense.
Imagine that there are alien couch potatoes 55 light-years away who, bored with their own Fall lineup, have constructed a LOFAR-style antenna in hopes of picking up "I Love Lucy's" debut. Hunky TV transmitters on Earth belch out a few hundred thousand watts of power. That energy is not beamed in all directions equally; most of it is aimed around the horizon (which, of course, is where the audience is). Because of this slight beaming, the effective transmitter power is a bit more: let's say a million watts, to keep the math simple.
OK, how strong is that signal by the time it reaches our putative alien audience at 55 light-years distance? Not very. The megawatt broadcast washes over ET's world with a power density of about 0.3 million million million million millionths of a watt per square meter, which is not exactly a scorching signal. Actually, only about a third of that transmission power is in the "carrier" - the part of the broadcast that's very narrow in frequency and easily detected. So knock that piddling power density down by another factor of three if you want to know the strength of the easily detectable part of the transmission. (Of course, if they only find the carrier, they won't get the picture and sound. But Lucy's jokes might not appeal to aliens anyway.)
Could their LOFAR-style antenna find that carrier, thereby indicating that a program was on the air? Well, engineers have computed that at the frequency of VHF television, LOFAR will have an effective collecting area similar to that of the 305-meter diameter Arecibo antenna in Puerto Rico.
That's big. That's brawny. But not brawny enough. In our SETI experiments at Arecibo, we could find a signal if it were about 0.1 million million million millionths of a watt per square meter. That number, you will notice if you count up the words, is a million times bigger than the "I Love Lucy" carrier at 55 light-years. The aliens' LOFAR would be inadequate to detect the broadcast by a factor of a million, a not entirely negligible amount. Simply stated: LOFAR couldn't hear it.>>[/quote]