well from what i know, they use radio signals or somethin and send them out in to space and wait for a reply... but i mean, is that really i good way, is there no better and faster way? becuase i heard even at the speed of light the signals are traveling at, it takes years for it to even get to the end of our solar system.. seems like a waste of time, and we have found nothing in the last like 30 years or how ever long SETI has been running for :|
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Chis

At the present time Mankind cannot share information faster than the speed of light.

So however, we look at this problem of vast distances, at present patients is going to be the only answer.

Best
Barry

*shruggs*

oh well :P
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Chis

was invented (British)prior to WW-II we didnt have high enough frequencies to penetrate the F-2 layer.

I seriously doubt if there is enough signal strength being emitted by TV to be intercepted by another planet, considering the signals are horizontally polarized to maximize groundwave coverage.

However, can you imagine some alien watching Sesamee Street?

Really strange creatures on that blue planet

communications instead of simply picking up sites that agree with your theory.

LF (30Khz to 300 Khz) is groundwave ONLY. HF (3 Mhz to 30 Mhz) is also pretty much groundwave until you get above 7 Mhz when skywave (F-2) kicks in (better know as "skip" to CB'ers).

In theory, if there were some "leakage" in those bands, it would be so small as to be un-detectable.

Design criteria for antennas in those spectrums is horizontal polarization for the most part to maximize either the surfacewave or skywave.

Broadcast (radio) stations are vertical polarized, since they want maximum signal in their licensed area. Still, under certain conditions (particularly at the high end of the band); broadcast stations can be heard hundreds if not thousands of miles from their intended coverage areas.

The F-2 layer is a highly efficient reflector for mid to upper HF frequencies, which is why you can hear transmitters with 5 watts or less many thousands of miles away under certain conditions (like Solar Max).

One early experiment had an HF transmitter on one of the earlier satellites (circa 1960's). It couldnt penetrate the F-2 from orbit. Ergo, why would anyone theorize that going the other way works either.

Once you get above 75 Mhz, you CAN penetrate the F-2. In fact the NOAA weather satellites broadcast mapping data at 137 Mhz with a paltry 5 watt transmitter that gives it global coverage.

In case your interested in unusual communications systems; go lookup Meteorburst or Meteorscatter.

Rather you study the very boring book titled Ionospheric radio Propogation, by the US Dept of Commerce, National Bureau of Standards (Library of Congress number 64-60061)or its successor.

Review "absorption" for E, Sporadic-E, F-1, and F-2 layers. You will see that the likeleyhood of ANY HF signal leaving these layers and going into space is nearly impossible.

I also note that the SETI guy refers to TV and Radar signals further down in the article, and leaves out HF entirely. That is a bit more credible.

He also says such signals were "accidental". Not !! We radar mapped the moon in the 60's, and nearly every satellite launched is/was tracked by the TPQ-18 "million mile radar" which would obviously "bleed over" into space.

A more likely emitter of signals would be TDRS or any of the S-Band transmitters on orbiting satellites which are constantly sending data, or digital voice.

I would pity the poor alien who accidently intercepted that purple singing dinosaur "Barney". Would probably terrify them

AM broadcasts started in the 1920's, which infers that Medium Wave signals could be sent into space; which they cant.

FYI: the first broadcast station was KDKA in Philadelphia.

The "Prof" is incorrect on his comment about TV broadcasts only being started in the 1950's. In fact Bell Labs had been transmitting since the late 30's, and regularly scheduled TV broadcasts started in the late 40's (after WW-II). But only on low-band VHF.

UHF-TV could indeed "bleed" into space. Pity the poor alien being subjected to PBS

There are also numerous optical SETI searches. The drawbacks with this is that searches must be directional, and diffraction limit of optical observatories produce a very narrow search width.

Another technique that was recently tried analyzed the atmosphere of a distance planet for signatures of life. The best current technique for discovering planets, spectral analysis using an Iodine cell, works best when the planetary orbital plane is close to parallel to our line of sight. This results in a high probability that at least one planet will occult (pass between its star and us) its star.

When this happens, some light passes through the atmosphere of the planet. We analyze the spectrum before the planet occults, resulting in a baseline signature of the star. Then, we analyze the spectrum when the planet occults its star. The difference of the two results in an absorption spectrum of the planetary atmosphere.