The space program SETI is the Search for Extra-Terrestrial Intelligence. Mostly, it consists of massive radio telescopes pointed at the sky, and computers combing through massive amounts of data.

It has been commented, though, that radio technology might not be the communication medium of choice for some other technological civilization. One other possibility is that if anybody else was out there, they would be using laser beams, possibly attached to their heads.

In 2006, the Optical Seti Telescope was inaugurated at Harvard, and the search for sharks with frickin’ laser beams attached to their heads began in earnest.

The search criteria to differentiate signal from noise was that the signal would be very short pulses of light coming from stars that are like our sun and nearby. This would make sense if civilizations were pinging us, directing intense lasers in our direction with the intent of getting our attention. Perhaps if a civilization was doing this, aiming very powerful lasers at every star in the sky in an attempt to communicate, this telescope could detect such a signal. No such signal was observed by this telescope, but SETI scientist Ragbir Bhathal at the University of Western Sydney tentatively says he saw what might have been a laser once, and has been carefully watching for it to show up again. Even if he does see it again, though, it might only mean the discovery of a laser-like natural phenomena of certain types of stars.

Now a bit about light. The bluer the light, the more energy it has, the redder the light, the less energy it has. Light is composed of particles called photons, and is produced by atoms, which are composed of protons and neutrons in a dense central nucleus, orbited by electrons. The electrons move in paths, called orbitals, about the nucleus. Much like blowing over the lip of a bottle creates the same note no matter how hard you blow, until you blow really hard and the air passes over the opening fast enough to jump the bottle up to the next higher octave, electrons orbit the nucleus in set orbitals, and abruptly jump up from one orbital to the next when the atom takes in enough energy. And then when the electron calms down, it lowers to the original orbital, releasing a photon. The wavelength of the photon corresponds to how much difference in energy there is for that particular atom between those two electron orbitals.

So different elements produce different colors of light when they get excited by things like heat or electricity. This is how we can tell what elemental composition stars have. We split up the light coming from the star into spectral lines with a prism tool called a spectrograph. Those lines tell us what elements are emitting light, and their relative intensities tell us how much, relatively, there is of each one in that star.

A laser is a light amplification of a stimulated emission of radiation. In a laser, a purified substance is excited with energy, typically electricity or heat, until it shines. What colors it shines depends on its element, as I explained above. The trick with a laser is to get all these atoms of some element shining one particular color, over a critical threshold past which more atoms are putting out the color than absorbing it. The light shines into an optical cavity, which absorbs and re-emits this wavelength of light, where it gains power and only has a single avenue of escape. What comes out is a laser beam.

Lasers come in all the colors that atoms can emit. All the spectral lines of the elements on the periodic table are all the colors of lasers that we have ever made. And they’re all the colors that we have seen in spectroscopes when observing the biggest, brightest things in the sky, stars.

But there might be other colors, because there might be other elements.

Avast Ye!

Avast Ye! Heavy Elements Ahoy!

It has been theorized since the 60′s that there might be more stable elements than we know about. For example, the element with an atomic number of 160, unhexnilium, might be stable. But making such an element would be very difficult. You couldn’t just smash two mercury ions together to create it, because they wouldn’t hold nearly enough neutrons. That isotope would undergo radioactive decay and come apart as soon as it was made. Something clever would have to be done.

But if it were to be done, and a significant amount of this element unhexnilium was synthesized, it might just be an ideal substance to use for a laser beam. Why? Because it could produce unique colors. A spectrograph could pick it out from natural sources of other light like stars with absolute certainty, since this element is unlikely to occur naturally in the universe at all.

I have read that these elements’ orbitals beyond the super-actinides can be derived using the Dirac equation.

The Dirac Equation

I don’t exactly know how to do that, but if it can be done, then could perhaps this telescope at Harvard filter for these spectral lines rather than just look for lasers aimed directly at us? It seems possible to me in my somewhat uninformed opinion that such a search might be better able to detect communiques meant to talk amongst themselves rather than just attempts by other civilizations to contact alien life. Such transmissions would be expected to be more typical, right? These telescopes have been called photon buckets, and they are really looking for a drop in the bucket. So it seems to me that it might be fruitful to look for a drop that is almost certainly not natural in origin.