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Comment: I was there at the EE Communications Group seminar (Score 1) 686

by Latent Heat (#47223693) Attached to: Aliens and the Fermi Paradox
where this radio search proposal was presented.

A lot is made about how hard it is to detect radio signals and how SETI is pseudoscience because all of the terms in the Drake Equation are wild guesses.

The meat of this proposal was answering the question whether anything like a terrestrial (analog) UHF TV station was "out there" anywhere up to about 400 light years. The search was "all sky" and didn't even involve highly directional (and hence high gain) antennas -- the plan was to use the feed horns, only, from the Big Dish at Goldstone, California.

The detection probability is a concrete formula in terms of factors such as the transmitting antenna gain (omni-directional), receiving antenna gain (low as they were going to use the feed horn), receiver noise figure (low -- at liquid helium temperature), data rate (one bit per observations -- you were trying to detect a beacon in the form of a pilot tone), and source entropy (very, very favorably low -- a crystal controlled carrier wave is a very stable, predictable signat that the JPL people had experience "picking out" from the background, even when needing to correct for Doppler, in "recovering" spacecraft that had lost their high-gain dish antenna).

If this project was ever conducted, they would have been able to rule out the presence of a UHF TV station out to 400 light years. Yeah, yeah, over what portion of life on another planet is there a civilization with UHF analog TV stations, and that question was asked during that seminar with a lot of wisecrack comments that the ET's have switched to fiber optic cable. But Fermi Paradox wise, were there an advanced Asimov-style intergalactic civilization, and were the civilization trying to get our attention, if they had a beacon anywhere near us, we would have found it by now.

That is, if this plan ever got funded. A quick look at Wikipedia suggests that owing to the spotty funding of SETI on account of anti-ET skepticism, maybe this simple search, which just needed some antenna time on the DSN and a digital FFT analyser, never took place.

Comment: Pilot carrier of UHF TV stations (Score 1) 686

by Latent Heat (#47219109) Attached to: Aliens and the Fermi Paradox
Gosh, this is already 30 years ago, but the SETI project at JPL had the idea of an all-sky search for the pilot carriers of (alien) UHF TV stations out to a couple hundred light years. The search would cover large swaths of sky using just the wide aperture feed horns on the Deep Space Network (DSN) antennas.

JPL's DSN was in the business of tracking spacecraft in interplanetary space emitting very low levels of power in crystal-controlled "pilot tones" that could be detected at great distances, doing this front ends with noise temperatures at liquid helium values. The idea is that a terrestrial TV station carrier would be emitting enough narrow-band power to be detected at interstellar distances, even with wide aperture low-gain antennas. If a tone is crystal controlled, it is sufficiently narrow band to be picked out of the background with a FFT filter bank of millions and then later billions of channels.

Does a digital TV station even emit a carrier or a pilot tone signal anymore? 30 years ago when a Caltech seminar speaker was a JPL engineer who had received a Senator Proxmire "Golden Fleece" award for doing SETI, which the Senator from Wisconsin thought was a misuse of public money, his colleague joked about "the aliens switching everything to fiber optic cable", but digital TV was a distant dream then.

Since then, haven't we pretty much ruled out aliens announcing their presence with narrow-band radio emissions at the level of our technology out to a few hundred light years?

Comment: The Golden Age of Programming (Score 5, Interesting) 294

by Latent Heat (#47031007) Attached to: Fixing the Pain of Programming
There is this, what should we call it, a mythology of a Golden Age of Programming?

I don't use mythology in a perjorative sense that this is all pretend or wishful nonsense. I use it in the best Joseph Campbell-Hero-With-Many-Faces sense, of a dim recollection of The Way Stuff Used to Be. This is a way of communicating an Underlying Truth about the Human Condition.

Apparently there was this era of things such as this Smalltalk that you allude to. Another version of this I hear from tales is Common Lisp. And Lisp Machines, specialized hardware and expensive workstations on which these "live images" would reside. So maybe these tales of direct, personal communication with the gods taking place with the Bronze Age Greek heros was not made up?

I guess there was this Barbarian Invasion of Bearded Men from the land called "New Jersey", especially a high place among the rolling plains they called "Murray Hill"? There is this piece of non-canonical scripture that our elders have been trying to supress known as the Unix Hater's Handbook explaining how we came to our present age and how this Golden Age entered into myth. Our elders warn against reading this heretical tract as dangerous to our souls.

As Jerry Pournelle describes the intervening Dark Age between now and that heroic or Golden Age, it isn't so much that people forgot how to develop and maintain a live image programming system such as Smalltalk or Common Lisp, it was that people forgot that such a thing could exist, and we attribute such things to gods or space aliens.

But then again, just as there is talk of ancient creatures in deep lakes in Scotland or in the remote sections of Zaire or Southeast Asia, there are accounts that Smalltalk or Common Lisp are still in use . . .

Comment: That Venus thang . . . (Score 2) 324

You can understand the Greenhouse Effect in terms of compression heating.

Owing to its composition of greenhouse gases, the atmosphere at sea level pressure is mostly opaque to infrared, and heat is transmitted through the air largely through circulation and convection, accounting for weather. The "radiative thermosphere", that altitude where the air temperature is determined by radiative equilibrium with space, occurs when the air gets thin enough. That altitude is a little bit below the "flight levels" where aircraft with pressurized cabins operate.

The warmer temps "down here" are the result of compression heating of air as it circulates in relation to the thinner air at the radiative equilibrium boundary. What CO2 does is it raises the altitude of thermal equilibrium, increasing surface temps through increase compression heating.

The atmospheric pressure at the surface of Venus is very high, but the air pressure diminishes with altitude just like on Earth, and that even with the high CO2 content of its atmosphere, the pressure altitude where Venus is in radiative equilibrium with space isn't that much difference as that for Earth. What makes Venus not simply hot but hellishly hot is not just the CO2 atmosphere or being closer to the sun, but the very thick atmosphere, raising the temps to these high levels at the surface.

That doesn't mean you cannot construct a narrative for a runaway greenhouse on Venus. CO2 plus proximity to the sun could have raised temps to liberate more CO2 from rocks in a positive feedback until the atmosphere became incredibly thick, but it is the thick atmosphere operating through compression heating that accounts of the melts-lead surface temps.

Comment: Obligatory Nuke Snark (Score 3) 152

Is this a geek thing, a Web thing, or our modern age that information is passed on in a scolding?

A post offers reprocessing as a solution to the reactor waste problem, and a proper counter to that argument is that reprocessing has a waste problem all its own. The total amount of long-lived waste may be reduced, but the "hot" shorter lived waste get spread around into corrosive liquid effluents?

Could a a person remind Slashdot readers of this tradeoff without suggesting that the original post was made by an untutored fool? Or is it important to label someone suggesting reprocessing as a foolish person, to offer a (mild) public scolding of their idea because reprocessing is a bad enough policy that shaming is merited?

"Lead us in a few words of silent prayer." -- Bill Peterson, former Houston Oiler football coach

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