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New Telescope Array Goes Live For SETI
The Skinny writes "Today is a historic day for the SETI program. The New York Times reports that astronomers are flipping the switch today on the Allen Telescope Array — 350 antennas, each 20 feet in diameter — which will, among other things, extend the search for extraterrestrial life a thousandfold. From the article: ' There are some 200 billion stars in the galaxy, and a significant fraction of them have planets. Estimates of the number of intelligent civilizations in the galaxy have ranged from one (or none, if you are particularly discouraged about human affairs) into the millions. Dr. Shostak calculated that the full Allen array would be able to detect a signal from as far as 500 light years that is only a few times more powerful than what can now be sent by the Arecibo radio telescope, a 1,000-foot-diameter dish in Puerto Rico that is the world's largest (although it is in danger of being shut down to save money). That translates to about a million stars, which he said was getting into a promising number. Dr. Shostak described the expanded search as looking for the needle in the proverbial haystack with a shovel instead of a spoon.'"
Only 42 installed so far. They are looking for donations to complete the array.
wot no sig
I think the better metaphor would be "trying to move a mountain with a spoon instead of a pen cap." Seriously, taking into account the number of stars, the number of planets orbiting the stars, and the span of time that they're likely to be spewing radio waves, the task is monumental compared to any resources that SETI may get. The work is still important, but let's not underestimate the task.
With 200 billion stars in OUR galaxy alone, and billions of other galaxies in our universe, anybody that thinks we are unique (usually religious type folks) are seriously fooled.
There has to be hundreds of thousands of life forms out there (at least). The sooner science finds it, the better.
Seth Shostak ( http://en.wikipedia.org/wiki/Seth_Shostak ) is a very entertaining and informative speaker of SETI topcis. See/hear him if you get a chance. He's a fun combo of dry, acerbic, and self-deprecating.
Two wrongs don't make a right, but three lefts do.
I wonder if this new publicised technology is better than seti@home, which was eclipsed by the jarvard META array, before it was even launched (the META array could do the job of SETI@home, in real time, and was retired in 1995 for the BETA, which has orders of magnitude more power). As long as SETI is dominated by PR stunts like seti@home, however, it'll never go anywhere
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...welcome our new alien overlords.
It's so nice when that meme fits without having to be stretched. This certainly is exciting news (about the telescopes too).
"That's no space station, Qfitzglb, that's a moon!"
I always find it amusing when people say money is "wasted". If I took a stack of bill and burned them, or buried them never to be seen again, that would be wasting them.
If they spent $100mill on a telescope array, where did the money go? It went to some firms who do that, who in turn paid their employees and their suppliers, who paid their employees, etc. Those employees bought groceries, sent their kid to the dentist, sent their kid to college, bought a new car.. the money flowed through the economy. Assuming a large percentage of the firms and suppliers are in this country, then the money stayed in the national economy.
When the economy is flowing actively, more of those people downstream will be willing to donate their time and money to what you'd probably classify as "good things". When it slows down, or the Government is taking a big chunk at every step as taxes, then they'll be less inclined to do so.
42. Why would they need more?
I keep tellin em but they never listen. Aliens gave up on radio eons ago. Poor range, prone to interference, and a host of other disadvantages. If you want to eavesdrop on what's being said about us in the universe, you gots to gets your hands on one of them newfangled SHF gravity wave radios.
If I didn't have absolutely NOTHING to do, I wouldn't be here.
Although I agree with the rest of your comment, I don't think burning money is wasting it. If you destroy currency you are removing it from circulation, which will cause prices to go down due to deflation.
If you truly want to waste money, you should buy something of value to others and destroy that thing. The grandfather post would be right, if one assumes that scientific research has no value. However, that is very seldom the case. Research is almost always valuable, even if it turns up nothing. Negative results are also knowledge. If we find no sign of extraterrestrial intelligence in our search we will know more than we did before about the abundance or scarcity of intelligence in our galaxy.
with a spoon, you could easily see the needle... with a shovel of a hay, the needle becomes a little more hard to see.
Did I mention its not backwards wednesday?
The first is that there is a concept of 'best-use'. That is, there are some projects (such as SETI) that some people feel are less worthwhile than other projects. Some people believe that the man-hours and capital used on SETI is wasted because nothing of value is produced by SETI (in their opinion) -- so yes, the money flows through the economy, but on a more worthwhile project, that money would flow through the economy while producing something of value. The money is in effect hoarded, which means that the opportunity to use it for growth is wasted.
The second point has to do with your remark about taxes.
Money paid as taxes also flows through the economy, for the same reason that money put into erstwhile "wasteful" projects flows through the economy. It's a bit of a double-standard to say that money that goes to taxes inhibits downstream spending, since that money is, in a very real way, redistributed to others, whether by government contract, to government employees, or otherwise. The exceptions would be foreign spending, which generally has benefit to the US as well, if less tangible.
If anything, with today's government, money taken out as taxes actually produces more money in circulation, since the US government runs a deficit budget with a cap on borrowing based loosely on government receipts. Every $1.00 given to the federal government returns $1.00 * [1 + (annual debt)/(annual receipts) -- of course, that's financed at an as-yet-undetermined final cost, since who knows what interest rate we'll have to pay on it when we refinance through new debt offerings...
"Trolls they were, but filled with the evil will of their master: a fell race..." -- J.R.R. Tolkien on Olog-hai
I dont mean to flame but...
I'm in the EE field, specifically wireless/radio communications.
The calculation for path loss is:
Loss dB = 32.44 + 20 log (dist in km) + 20 log (freq in MHz)
Lets take absolute optimal conditions..proxima centauri is roughly 4 light years away. This is roughly 3.78x10^13 km away. One of the most common frequencies monitored is the "hydrogen line" (1420.40575 MHz) since this is the resonant frequency of hydrogen and is more likely to be used by aliens since we'd most likely be looking there.
So, lets fill in the equation:
32.44+ 20log(3.78x10^13)+20log(1420.41)= 367.038 db of loss...
So lets say they are transmitting with a million watts(90dBm), and there is a 60db dish on both ends(huuge dish)...This gives us a receive level of -157.038dBm. This is a good bit below what any normal radio will receive at. The noise floor is certainly higher than this. Now keep in mind this is the very closest star, which I don't think even has any livable planets.
Our galaxy is 70-100 thousand light years across and we are right near the edge. So if you take a star not even close to that distance, say 500 light years (still somewhat close on a galactic scale) then the calculations work out to a receive signal of -198dBm. The equipment doesn't exist to pick the signal out of the noise at levels like that.
God forbid trying to pick the signal out of another galaxy, the nearest being Andromeda. some 2.5 million light years away. Giving Rx signal levels of ~ -273dBm. Safe to say the noise floor is MUCH MUCH higher than this.
I think SETI is a hopeless pipe dream. That being said, I DO think there is intelligent life out there, probably in our galaxy. There are just too many stars with too many planets to think otherwise.
It's easier to fight for one's principles than to live up to them.
Spoons, shovels? I always thought it would be easier to search for a needle in a haystack with a magnet, but what do I know?
"I'm so moist I'm sticking to the leather." -Kermit the Frog on The Late Late Show
It's called Baseline interferometry. You combine the signals from multiple scopes, to get a scope with the effective size of the distance between them. There have been plans for years to put some in Earth's solar orbit, at various points ahead and behind. this would give a dish that, parallel to the plane of the ecliptic, has an effective size of about 1AU (8 light minutes) radius.
There are other mutli-telescope arrays, apart from the VLA in New Mexico (made famous by films like Contact) although few are grouped together. One of them is MERLIN (http://www.jb.man.ac.uk/booklet/Merlin.html) which was established in 1980.
Now, if only I can finish my designs for a fairly cheap BLI capable road-mobile telescope of sufficient size, we might get even more data.
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Hardly. SETI@home is not 'SETI' - it is one small subgroup of it. If anything, it's more of a publicity stunt than serious science. As i've posted elsewhere, the processing power of SETI@home is dwarfed by a system Harvard retired in 1995, for a more powerfull system. The other problem is that the Aracebo telescope is not the best scope to be using for SETI work. It's not very steerable, it's a fixed dish in a depresion in Puerto Rico - the only aiming that can be done is by moving the receiver (the bit they fought on in GoldenEye)
If Berkley was really serious about SETI, they'd have fitted a META (MillionChannel, Extra-Terrestrial Array - http://seti.harvard.edu/seti/meta.html) or a BETA (BillionChannel Extra-Terrestrial Array - http://seti.harvard.edu/seti/setihist.html) to process it. It actually takes about as much hardware for a META as is needed for the backend of the BOINC client.
If you really want to help space exploration, and science, and communication, you'd be better off with a project like the Muon1 DPAD (http://stephenbrooks.org/muon1/ ), working on the Neutreno, which may be a viable communicative method when understood, as it appears to not generally interact with matter. imagine Europe-Japan communication direct, beamed through the earth, rather than via satelites, or cables run on the surface/ocean floor.
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It's not "a bunch of little telescopes". It is one large phased array. The signals from all the antenna are added in phase. By controlling the delay from each antenna before adding the signals they can point the beam around in the sky. By building more "adders" they can have multiple simultainious beams.
Think of each dish antenna as an element of a single larger antennta
They are NOT listening for random signals like the type that are leaked out from Earth. The array is not sensitive enough for that. What they are hoping to find as a beacon. A huge transmitter beamed right at us. If they find such a thing then we might reasonably guess there is a signal on it. We would not have to wait for 2-way communication to learn a lot. Heck even if all we got was a "Hello Earth" greeting that in itself would be one of the greatest discoveries in all of history.
I doubt there are any huge microwave beacons. If we do discover anyone out there it will only be after our arrays become powerfull enough to hear the "leakage" signals that only escape by chance, like the signals we are currently sending. But we could get lucky. It's like buying a lottery ticket.
The SETI Institute is an organization that employs many scientists. A few of the scientists there do SETI (i.e. they search for extraterrestrial intelligence). The vast majority do not. The SETI Institute, in collaboration with the University of California Berkeley, are building a telescope called the Allen Telescope Array. Some of the scientists at the SETI Institute will use it for SETI. Other astronomers will use it for non-SETI related projects.
SETI@home is a project at the University of California Berkeley. It is neither funded by nor affiliated with the SETI Institute. In fact, some SETI scientists at the SETI Institute, dislike SETI@home because it directs attention (and therefore funding) away from SETI Institute projects. Competing projects also have some at the institute worried that someone else may be the first to detect extraterrestrial intelligence. For those reasons it is unlikely that SETI@home will ever be allowed to utilize data from the Allen Telescope Array.
From my vantage point, it appears that this confusion is promulgated by the SETI Institute. They would like the world to think that they are in control of all SETI related projects, and they would very much like to control all SETI related funding. At this point they feel that there is no advantage to preventing this confusion. In fact, scientists at the SETI Institute often drop the word "Institute" when they mention their affiliation, and just say they are "from SETI" or "with SETI".
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"I think SETI is a hopeless pipe dream."
.211m. The brightness temperature of the galaxy as viewed from Earth's surface is around 5-10 Kelvin at that wavelength.
.211) = 4.63*10^18 meters
I assume you think your erroneous application of signal theory leads to that conclusion. More studious and clever people than you have already illustrated the viability of signal reception at these distances, and your analysis is quite simply wrong. Your "EE" expertise has led you astray: when you ask someone who only knows about whales a question about ducks, he talks about whales anyway. Radio astronomy has had these things down for more than 50 years, and you're a day late and a dollar short.
We're interested in obtaining a signal against a background. The antenna temperature, Ta, determines this:
Ta = [(pi^2)/16k] * (W/r^2) * (D1^2 * D2^2) / lambda^2
where
k is Boltzmann's constant
W is the power per unit of bandwidth of the source
D1 and D2 are the diameters of the receiving antenna and (hypothetical) transmitter antenna
lambda is the wavelength
The signal, per the common example, is 1420.4GHz => 21.1cm =
What about the noise temperature of the receiver? A receiver must have sufficiently low Tn, otherwise it's louder than the signal it tries to measure:
Tn-rms = Tn / sqrt(t * Bw)
where
Tn-rms is the root-mean-square value in question
Tn is the noise temperature of the receiver in question
t is the integration time (how long we keep the lid off the photon bucket)
Bw is the receiver's bandwidth
The noise temperature of modern low-noise amplifiers is much lower. A rule of thumb for present-day: 1 Kelvin per GHz, plus 1 Kelvin, so 2~3 Kelvin for this LNA, and there are lower noise devices available for a price, but only to a point. The cosmic background noise is larger than the receiver noise!
Let's combine them and rearrange, and see just what kinds of power and distance we need:
r = (pi/4) * sqrt(W / k*Tn) * (D1 * D2 / lambda) * (t * Bw)^.25
Suppose we have a 50kW transmitter, use the 300m Arecibo dish to transmit and receive, use a bandpass of 1Hz (this is reasonable), and an integration time of about 20 minutes (1,000s). Go ahead; do the math--
r = (pi/4) * sqrt(50000 / [(1.38e-16)*3] * (300 * 300 /
Which is 489 light years.
Yes, given currently manufactured technology, the Arecibo dish could communicate with an identical dish at exactly the distance in the article, given a modest 50kW transmitter. I picked numbers to contrive the distance in question, but all of them are available with current technology, and most of them are already installed and operational at Arecibo Observatory. What if we chose a MW transmitter (available), or halved the wavelength to 10cm, or used a bigger (perhaps virtual) dish, or a lower noise antenna? All of these things would MASSIVELY improve the resolvable range of the transmission. 5000 light years is well within our current technology-limited broadcast/reception range. The hard part, as discussed by others here, is justifying implementing this much hardware and employment (versus buying ONE SINGLE JET FIGHTER).
If you think the problem with SETI lies in its technical shortcomings, you're sorely mistaken. The SETI program is a long shot for other, more difficult scientific and borderline philosophical reasons, but close examination of the physical problem at hand (which you clearly have not done) illustrates that it's not as long as your cynicism would have you judge in lieu of actual thought. You're welcome to argue your opinions, but don't mis-apply one inapt little corner of signal theory as proof that your perception of the world is, in fact, reality.
+5 Insightful? The mods have been bamboozled by unfamiliar equations. As for my analysis? Go ahead-- verify it with your favorite relevant textbook, for a change; please.
SERENDIP, META, and BETA are essentially simple FFT processors, with BETA essentially being four 80 million channel analyzers. That is proof that to an astronomer 240 million is equal to a billion. SERENDIP IV (the last one deployed) was a 168 million channel analyzer. Both had channel widths of about 0.5 Hz (0.5 Hz for BETA, 0.6 Hz for SERENDIP). The channel width limits the sensitivity. Simple FFT analyzers cannot go to narrower channels without correcting for Doppler drift which will chirp the signal out of the channel in less than the integration time, and because the Doppler drift depends upon the properties of the transmitter in addition to the motion of the Earth, it's not a simple process that can be done on the fly.
SETI@home implements coherent dechirping which allows for channel widths of 0.075 Hz or less. In essence you are changing maximum coherent integration time on a signal from 2 seconds to (in SETI@home) about 13 seconds for simple (single time bin) signals. In addition SETI@home searches at higher sensitivity for multi-time-bin signals with up to 107 seconds integration. SETI@home also searches for repeated (fixed period) pulsed signals, which none of the special purpose instruments can do.
Now add the consideration that SETI@home (and the Berkeley SERENDIP instruments) uses a telescope with a collecting area 140 times as large as the telescope used by BETA.
If you calculate the maximum value of the processing power of BETA, (a 240 million point FFT every 2 seconds) you get 16 GFLOPS. That's an overestimate because a) it's not a floating point processor, but an integer processor, and b) it's implemented as sixty three 4 million point tranforms.
SETI@home, on the other hand, currently cannot handle real-time data from the ALFA instrument because it only has about 1/3 of the 1.2 PFLOPS it needs to process at that rate. In other words to do the same processing as SETI@home does, you need to build 75000 BETAs.
That's not to say BETA (and the SERENDIPs on which it was based) wasn't worth the effort. At the time it was among the best. SERENDIP V will eventually take over where SERENDIP IV left off, so the age of the SETI hardware based spectrometer isn't over.
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No no no, That equation does not work in a vacuum. The air loss needs something else...namely....air ;)
How is it that we can pick up the little tiny signal coming from voyager which went so far beyond us is your equation worked in a vacuum? I guess we would not.