feynman

http://www.newscientist.com/news/new...255&lpos=home3

Chances of aliens finding Earth disappearing

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.


Laser beacon

Drake's insight has important implications for search strategies. It means that eavesdropping on unintended alien transmissions is unlikely to succeed and "argues for an emphasis on detecting beacons", i.e. signals intentionally sent our way.

Some SETI strategies have already begun shifting toward that approach, including efforts to find optical beacons based on high-powered lasers deliberately aimed at nearby stars.

While optical communications across interstellar distances was initially thought impractical, military research has led to lasers sufficiently powerful to make such signalling much more efficient than any radio beacon.

Nuclear-powered lasers on the drawing boards could produce pulses that would outshine the sun by a factor of 10,000, said Harvard University physicist Paul Horowitz, who has already been searching for such pulses. He has designed a new telescope that will soon be dedicated full-time to that search.

And other innovative ideas keep coming along. Planet hunter Geoffrey Marcy of the University of California, Berkeley, said someday we may learn to use the sun itself as a gravitational-lens telescope, with a detector parked at its focal length of 500 astronomical units.


David L Chandler

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Confed999

Cool post. A 50 light year, and expanding, bubble is pretty big. If every alien civilization has something similar, detection is only a matter of time. Still, I would rather they concentrate their efforts on our solar system and the objects/conditions that could harm/help us here.

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feynman

Glad ya enjoyed it. Ya 50 ly is pretty big. Would have the surface area of around 10^30 mi^2 (approximating it as a sphere). I think our planet's SA is on the order of 10^8 mi^2. So, ya, just a lil bigger

Horrido

Good....

I, personally, don't want any advanced civilization knowing we're here until we've developed the capabilities of interstellar travel and weapons systems to kick the butts of anything that might want to do us harm. History has taught us that any society aggressive enough to explore, is also typically aggressive enough to dominate, exploit, and eradicate the current inhabitants for its own objectives.

Goodness and light my ass... One name: Cortez.

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griftadan

im not to worried about. i mean think of it this way: if in 500 years, we discover a weaker civilization and have the technology to go over there and conquer them, but we dont, cause a, theres really no need to do that, and b, an advance society like ours usually has a middle class full of liberals who wouldnt put up with that ****. then again, look at halo.. IT COULD HAPPEN! ...(its hard to translate sarcasm into text)

ZFBoxcar

Advanced technology and social advancement are not always bound togethor. Its completely possible that by the time we master space travel Earth will be an oppressive dictatorship. It seems unlikely because technological advancement proceeds more quickly in open societies but even following that, there is no reason to assume that once we achieve technological greatness, some civil war won't plunge us back in to the dark ages socially although not technologically. A good series involving this scenario is the Foundation Series by Isaac Asimov.

Anon

A worldwide socailist state is a very real- and very spooky- longterm possibilty.

The Chap

I concur wholeheartedly. Not the bit about immolating y'bum tho'.

We probably should remember that NS refererred to a shell as opposed to the volume of a sphere, the thickness of the shell, ignoring diffusion and other scattering effects (interstellar medium etc.) only being as "thick" as the "active" spectrum broadcast lifetime of the emmitting civilisation.

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barrowaj

This sounds smart, except when you actually consider the possibilities. First, any alien civilization that has the technology to track and come to us probably has far more advanced technology than us. So if they come with malicious intent there is only a small chance that we could develop a weapon that could defeat them. Second, it wouldn't make economic sense for them to come travelling all the way across the galaxy to come and use our planet for its resources. There are more than likely tons of planets that are much closer for them to use.

Arguing from a different standpoint, I would say that if a race had the ingenuity and curiousity to develop advanced starships, then they would be more interested in learning about us than destroying us. Furthermore, if the alien race managed to prevent its own destruction, it must have learned how to be peaceful. A totalitarian regime could develop spacecraft, but these sorts of regimes are not stable in the long run (at least for us) because they result in individual oppression..

Horrido

One name as a reminder: Hernando Cortez...

Can you think of any occasion in history, where an established "colonizing" force DIDN'T either anihilate or subjugate the native population, and instead coexisted in peace, where the native population wasn't successful in killing a goodly proportion of the invaders, first?

Anon

Yep.

Christian missionaries.

Besides them, it's probably an extremely short list.

Aryan

Sure...Iraqi family that moved into my street a few weeks ago.

barrowaj

Whatever weaponry that the Aztecs or Incas could have developed would not have stopped them from dying from diseases brought to them. Furthermore, even if they killed the fist few expeditions, more would come.

Of course this totally neglects the fact that space travel is much different than travelling by sea simply from one continent to the next. You would have to expend a huge amount of energy just to get here, making any kind of trade economically infeasible. I don't think there is any reason to beleive that our planet is particularly valuable (besides intelligent life) given that there are so many other possibilities around.

It is much better that we spend our money on a way to prevent ourselves from destroying the habitable environment rather than some kind of hyper expesive weaponry that has a purely hypothetical use.

CoyoteNature

I can evision a hundred different possibilities for possible contact and all of them equally realistic. Realistic in the sense of our own preconceptions. I mean if you look at the history of the species, it has been about conflict true, but also about cooperation, its not about war or peace but both. But this applies only to our own species, we are rarely as nice to other species as we are to our own. History has shown our greatest strength to be the quick and efficient annihalation of our competitors on this planet. In effect we are so high up partly because we killed off anything that could hurt us, and amusingly enough we did this cooperatively. I can evision a future when man is reasonably unified however, bear in mind that this does not imply peace with other races, we from our perspective might not countenance a threat to our survival or any threat however small. Especially when one considers the destructive yield any civilization at or above our current own is capable of.

Currently we are capable of within ten minutes of wiping out all of human civilization on the planet, that a most of the larger animals and plants on the planet. However this in the grand scheme of things is not really that big, fact is life has gone through extinction events before it survives, life reevolves new possibilities. But anyway the only way I could think of to really elliminate all life with possible current capabilities or extensions of them would be successive bombardment of multiple directed asteroids at the size of the dinosaurs or more. Other possibilities with a crash program could possibly involve a low C relativistic bombardment of the planet. Or give a few thousand years of concerted effort, it might be possible to construct various technologies which could cause the Sun to go nova, and thats just with current technologies and our current knowledge, assuming nothing new gets developed at all and we just keep on breeding and spreading.

But think about the possibilities of Mass destruction when you get into High C, Antimatter or Nannite replication, all technologies not impossible, such technologies could destroy our system within days with the High C versions, or months with Nannite versions. So given the possibilties of such a threat and given the near impossibility of deflecting such technologies, it would make sense to destroy a up and coming civilization before it demonstrated a capabilty to harm us.

To paraphrase the Colt motto, "All species might not be equal but WMDs make all of them superior."

Or some such pardon the butchery of the saying.

Just giving a possible reason for them not necessarily evil or anything just wishing survival.

From a viewpoint of conquest, that is rather silly, the only species that would care at all is us or possibly our ancestors genegineered species, or A.I. derivatives. Thus we would only worry about conquest from ourselves, you know raping pillaging, stuff like that only applies to humans wanting to take territory resources, etc. from others of our kind, and in general those resources would coincide but be different from true aliens.

But this does not mean simple pest extermination is out of the question for survival's sake.

Not to say they couldn't be equally agressive just that their interests might not necessarily coincide.

I mean we have the capabilty to build starships and we haven't elliminated conflict genoicide, etc., why should we think they have either (Starships is not referring to high C ships, just very low C ships or even generation slowships which we might be capable of building with a crash program).

An aside I think the French were very successful in integrating themselves peacefully into Indian culture, of course it was fairly unique circumstances, the French were outnumbered and thus rather had to resort to other methods more subtle.

From a viewpoint of them conquering us, well it might be rather harder, I mean conquest presumes you wish to keep the realestate in a reasonable condition, it means you couldn't use any of a hundred methods possible for total annihalation because you might damage what you want.

For conquest resistance might be fairly possible, I mean we evolved here, we know the area, we have the technologies adapted to our environments they don't, and technology is always a adaptation to environment, it forms because of environmental needs whatever those are.

To use the Indian analogy again, the Pilgrims would never have been able to survive if not for the help of the Indians with their technologies, their maize products, tilling hunting, knowledge of territory, all of their supposably more advanced technology was of a little help during the winter and the years after.

Actually from a a viewpoint of the entire European invasion, if the Indians had united and had not helped the colonists there was a good chance they could have staved of the invasion long enough to develop other capabilties, I mean the facts are the Europeans at the time were at each others throats and cared little for the Indians themselves as a threat.

Plus at the beginning technolgies were such that it made true conquest very very hard and nearly completely dependent on native help.

Cortez to use another example would have had little success conquering the Aztecs if not for the help of many other rival indian tribes who wanted the Aztecs dead. I mean Cortez wasn't exactly the most competent of leaders, sure he had a few blunderbusses, and heavier armor,but nothing technolgically that could not be corrected a few decades, but his men were limited in number, and to boot were stupidly greedy, so much so there was a tale of how in trying to escape from being killed his men left the city, in the process several of them died drowned from the weight of the gold on them.

The beginning of colonization was very dependent on native help without which it would not have been able to survive at all, facts were the colonists had to live of the land in a entirely new environment all without little hope of fresh resources arriving from home ( a very similar analogy where conquest is involved, except we talk about years or decades before further help could be realized).

Tactically and Stategically the natives, in this case us, would have to kill of the colonists quickly, while at the same time denying them access to information about the environment and without helping at all.



But that said a true invasion would have to be wiped out relatively quickly

Parihaka

I'm reminded of a book by greg bear (forge of god?) in which he suggested that certain races might develop planet killing tendencies and use self replicating robot ships simply to rid themselves of threat and/or competition. keep quiet and keep a sharp lookout I say...