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After 35 Years, Another Message Sent From Arecibo
0xdeadbeef writes "Two weeks ago, MIT artist-in-residence Joe Davis used the Arecibo radio telescope to send a message to three stars in honor of the 35th anniversary of the famous Drake-Sagan transmission to M13 in 1974. It was apparently allowed but not endorsed by the director of the facility, and used a jury-rigged signal source on what will now be known as the 'coolest iPhone in the world.' The message encoded a DNA sequence, but no word yet on whether it disabled any alien shields. You can get the low-down on Centauri Dreams: Part 1, Part 2."
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If this transmission stimulates even one young person to do that calculation for themselves, or to otherwise conclude that it's a foolish waste of money, it will have been money well spent.
We are very tasty snacks! Here, have our DNA, and grow some appetizers for the long journey!
I suffer from attention surplus disorder.
Without any context --- e.g., our biochemistry, amino acid structure, nature of DNA --- this message amounts to about the worst practical joke in the history of interstellar communication. It has a relatively non-random structure, so clearly must mean something, and yet they'll never figure it out.
But if they do figure it out, we'll get a message a century from now: "Delicious! Do you have any other recipes?"
Dear citizens of Centauri. I have a large sum of gold, 300 metric tons, I need to move off planet. If you'll deposit a small transfer fee, 3 metric tons of gold, in a local bank I will make arrangements to ship the gold to you. Signed crowned prince of Iowa.
These guys must be loaded. Would you believe the rates they're charging for interstellar calls?
Oddly, we just solved this problem in E&M class. If you had antennas with 80 dBi gain at both ends and a megawatt of power, that would be sufficient to transmit 10^5 bits per second over a lightyear gap with a received power level above the thermal noise floor (e.g. the antenna does enough work on the receiver to flip a bit). Raise the distance to 100 lightyears and reduce the gain to 73 dBi (e.g. Arecibo) and you lose 5.5 orders of magnitude in bit rate. Up the power to three megawatts (not hard to imagine) and you get back half an order of magnitude. So the achievable rate over 100ly using only current Earth technology at both ends is about a bit per second. Useless, perhaps, but not technically impossible.
This just in - they got a response:
Dear Earthling,
Hello! I am a creature from a galaxy far away, visiting your planet.
I have transformed myself into this text file. As you are reading it, I
am having sex with your eyeballs. I know you like it because you are
smiling. Please pass me on to someone else because I'm really horny.
You have no idea about what you are talking about. It is true that omni directional radio sources are subject to inverse square law, but directional signals degrade less slowly. Scientists have calculated that using the Arecibo dish at one megawatt the signal could be received by a similarly sized dish 10000 lightyears away. I think I trust calculations done by people with PhDs in astronomy more than calculations done by you and your friend
I'ma let you finish, but we already got a reply to the original message!
--
"Open source is good." - Steve Jobs
"Open source is evil." - Microsoft
We could have rickrolled them so they could get a taste of our culture!
As it is a linear partial differential equation, all solutions to the wave equation and equations of its type are governed by what is known as the "fundamental solution" or "Green's function" of the equation. In the case of wave type equations(in 3 or more dimensions), this solution will be a delta function type solution which decreases inversely with distance from the source. Squaring its amplitude to obtain energy gives an inverse square energy decrease.
It must be stressed that all solutions of the wave equation, no matter what the sources, or boundary or initial conditions, must all be functions derived, more or less, from convolutions of the fundamental solution with the source terms. You cannot escape the inverse square behaviour of wave propagation over long distances with finite wave sources. The fundamental solution characterises all waves because of the linearity of the wave equation.
Now, there is a second fundamental solution for the wave equation; the so called "acausal" Green's function, which represents an inwardly collapsing wave, or by some conventions, a wave travelling backwards through time. Naturally, these waves are not considered in the context of the transmission of signals. Even if they were, these waves also display and inverse square relation for signal strength( going backwards in time of course).
This has been your daily mathematical public service announcement. Complaints to be directed to the Dean.
May the Maths Be with you!