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.'"

Comments

Shovel instead of a spoon?

[moderatorrater]

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.

Re:Billions or millions, right?

[theguru]

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.

Not just the wrong band, the wrong everything

[Wingsy]

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.

SETI is hopeless

[anethema]

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.