15:59 09 August 04
NewScientist.com news service

A pioneer of the search for extraterrestrial intelligence (SETI) has warned that for any intelligent aliens trying to search for us, "the Earth is going to disappear" very soon.

Frank Drake's point, made at a SETI workshop at Harvard University on Friday, is that television services are increasingly being delivered by technologies that do not leak radio frequencies into space.

But he added that in some ways the observation is good news for SETI, as it means that the failure of Earth-based observers to detect aliens so far may be less worrisome than it would otherwise seem.

Most SETI efforts have focused on detecting radio signals that might be emitted by intelligent beings on planets around nearby stars. For humans, such signals "are the strongest signs of our existence", Drake said, thanks to television.

Traditional television broadcast antennas put out one megawatt each, and this radio-wave bubble now extends about 50 light years out from the solar system.


Straight down

But that is changing fast, Drake says. More and more television is now delivered by cable, with no radio-frequency leakage to space, and by direct-broadcast satellites that put out just 20 watts per channel, all efficiently directed straight down the intended areas on the Earth's surface.

So from the point of view of being detected through such inadvertent broadcasts, the longevity of humanity's detectability may be just 100 years.

And longevity may be the most important figure in Drake's famous equation for estimating the number of detectable intelligent civilisations on other worlds. The best estimates show that all the other crucial factors nearly cancel out, so that the number of such civilisations in our Milky Way galaxy is roughly equal to their average longevity of detectability in years.


The full story can be read here.

I do not think so cause this place (Earth) is the Universal Intergalactic Zoo for this quadrant of the Universe.

This 'SPACE' for Rent.

M7

> But that is changing fast, Drake says. More and more television is now
> delivered by cable, with no radio-frequency leakage to space, and by
> direct-broadcast satellites that put out just 20 watts per channel, all
> efficiently directed straight down the intended areas on the Earth's surface.
>
> So from the point of view of being detected through such inadvertent
> broadcasts, the longevity of humanity's detectability may be just 100 years.

I don't buy it. Even assuming that television transmitters disappear, there's still a lot of additional radio transmissions. For example, what about all the 100,000 watt AM and FM radio stations? What about cell phone towers?

I don't know my physics for this, but would one million cell phones with one watt transmitters be equivalent to a 1 Megawatt TV tower for SETI purposes?

If anything, I think the amount of radio transmissions coming from earth have increased greatly in the last few years, with the increase in cell phone and wireless networking usage.


-------
Kevin Lowey - University of Saskatchewan
Life is what happens to you while you're busy making other plans - John Lennon

>
> > But that is changing fast, Drake says. More and more television is now
> > delivered by cable, with no radio-frequency leakage to space, and by
> > direct-broadcast satellites that put out just 20 watts per channel, all
> > efficiently directed straight down the intended areas on the Earth's
> surface.
> >
> > So from the point of view of being detected through such inadvertent
> > broadcasts, the longevity of humanity's detectability may be just 100
> years.
>
> I don't buy it. Even assuming that television transmitters disappear, there's
> still a lot of additional radio transmissions. For example, what about all the
> 100,000 watt AM and FM radio stations? What about cell phone towers?
>
> I don't know my physics for this, but would one million cell phones with one
> watt transmitters be equivalent to a 1 Megawatt TV tower for SETI purposes?
>
> If anything, I think the amount of radio transmissions coming from earth have
> increased greatly in the last few years, with the increase in cell phone and
> wireless networking usage.
>
>
> -------
> Kevin Lowey - University of Saskatchewan
> Life is what happens to you while you're busy making other plans - John Lennon
>Almost every automobile out there has carbon brushes in it running on copper slip rings. This must create an incredible amount of RF noise. Frankly, I'm surprised that we can hear anything in space at all. Unless this world comes to a technological standstill,I don't think that a lack of deliberate radio transmissions will be a problem.
We are a noisy people. Hear us!
NFN, Glenn.