Why Worry about ET, Stephen Hawking?

Famous astrophysicist, Stephen Hawking, made the news recently when he called for us to stop attempting to contact ET.  No offense to Dr. Hawking and other scientists who have similar points of view, but I find the whole argument about dangerous ET’s, to use a Vulcan phrase, “highly illogical.”

First of all, there is the whole issue around the ability to contact ET.  As I showed in my post “Could Gliesians be Watching Baywatch“, it is virtually impossible to communicate with any extraterrestrial civilization beyond our solar system without significant power and antenna gain.  The world’s most powerful radio astronomy dish at Arecibo has a gain of 60 dB, which means that it could barely detect a 100 kilowatt non-directional signal generated from a planet 20 light years away, such as Gliese 581g, but only if it were pointed right at it.  More to the point, what are the odds that such a civilization would be at the right level of technology to be communicating with us, using a technique that overlaps what we know?

Using the famous Drake equation, N=R*·fp·ne·fl·fi·fc·L, with the following best estimates for parameters: R*= 10/year, fp= .5, ne= 2, fl= .5, fi= .001 (highly speculative), fc= .01, L=50 (duration in years of the radio transmitting period of a civilization), we get .0025 overlapping radio wave civilizations per galaxy.  But if you then factor in the (im)probabilities of reaching those star systems (I used a megawatt of power into an Arecibo-sized radio telescope), the likelihood of another “advanced technology” civilization even developing radio waves, the odds that we happen to be  pointing our radio telescope arrays at each other at the same time, and the odds that we are using the same frequency, we get a probability of 1.25E-22.  For those who don’t like scientific notation, how about .0000000000000000000000125.  (Details will be in a forthcoming paper that I will post on this site.  I’ll replace this text with the link once it is up)

So why is Stephen Hawking worried about us sending a message that gets intercepted by ET?  Didn’t anyone do the math?

But there is a second science/sci-fi meme that I also find highly illogical.  And that is that malevolent ETs may want to mine our dear old earth for some sort of mineral.  Really?  Are we to believe that ET has figured out how to transcend relativity, exceed the speed of light, power a ship across the galaxy using technology far beyond our understanding, but still have an inability to master the control of the elements?  We have been transmuting elements for 70 years.  Even gold was artificially created by bombarding mercury atoms with neutrons as far back as 1941.  Gold could be created in an accelerator or nuclear reactor at any time, although to be practical from an economic standpoint, we may need a few years.  However, if gold, or any particular element, was important enough to be willing to fly across the galaxy and repress another civilization for, then economics should not be an issue.  Simple nuclear technology can create gold far easier than it can power a spaceship at near light speeds through space.

Even if our space traveling friends need something on Earth that can’t possibly be obtained through technology, would they really be likely to be so imperialistic as to invade and steal our resources?  From the viewpoint of human evolution, as technology and knowledge has developed, so have our ethical sensibilities and social behavior.  Of course, there is still “Jersey Shore” and “Jackass,” but by and large we have advanced our ethical values along with our technological advances and there is no reason to think that these wouldn’t also go hand in hand with any other civilization.

So while I get that science fiction needs to have a compelling rationale for ET invasion because it is a good story, I fail to understand the fear that some scientists have that extraterrestrials will actually get all Genghis Khan on us.

 

Could Gliesians be Watching Baywatch?

[Note: Click here for a more thorough treament of the viability of SETI and the (high) likelihood of extraterrestrial intelligence]

Gliese 581g is an earthlike planet orbiting the star Gliese 581, 20.3 light years away from us.  Discovered just last week by astronomer Steven Vogt, he announced that the odds of life on this exosolar planet are 100%.  That’s a pretty bold statement, even for a planet thought to be in a habitable zone of a star a little smaller and cooler than our sun.  Most astronomers are attributing his statement to being a little overexcited with his discovery.  But it got me wondering – if there were technologically advanced lifeforms on this planet, is it possible that they would be able to receive our radio or TV transmissions?  And, remember that when Gliese 581g might be receiving from us today is what we broadcast 20.3 years ago, such as episodes of Baywatch.  Alternatively, can we hear them, as SETI has been attempting to do for the past 30 or so years?

As it turns out, there isn’t much to worry about, unless we decide to send a very high-powered narrow directional message to a planet that just happens to be at the perfect level of technology which also just happens to have outpaced their social evolution dramatically.  Not likely there either, for reasons that I will discuss in an upcoming post (sorry, Stephen Hawking).

Here’s the deal.  Let’s take a typical TV broadcasting station operating 50000 watts on Channel 2.  Because radio waves attenuate proportional to the square of the distance from the transmitter, this signal will be pretty miniscule by the time it gets to the edge of our solar system.  In fact, by the time this 6 MHz wide signal at 60 MHz gets about 1.4E+11 km away, its power density will be at the same level as the corresponding power density of the cosmic microwave background (CMB) radiation in that frequency band (feel free to check my math – it’s a little rusty).  In addition, the signal will be an indecipherable mess because it will be intermixed with all of the other TV stations broadcasting on Channel 2.  So how far out exactly is 1.4E+11 km?  Turns out this is past Pluto, but barely the beginning of the Oort cloud in our own Solar system, or .015 light years.  That is .00075 of the distance to Gliese 581, across which distance the signal will be attenuated by a further factor of 1.8 million and CMB background noise will completely swamp out the signal.

So, zero chance of Gliesians kicking back and enjoying an interstellar episode of Baywatch.  And not much chance of us hearing accidental radio waves generated from their planet, even assuming they followed a similar technological evolution at the exact same time as us.  Sorry, SETI.
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