“Space is big—really big,” said Douglas Adams. It is so mind-bogglingly huge that we poor little humans are actually incapable of grasping its size. To demonstrate this, I want you to take a minute out of your busy life to look at this relatively recent video from the Sloan Digital Sky Survey. But before you go… There are three important points about it that you ought to understand before you see it.

  • First: Each one of those points of light you see is a galaxy— not an individual star—not even a solar system—but an entire galaxy with between 100 billion and half a trillion stars. Travelling at the speed of light it would take you 30,000-60,000 years to cross from one side to the other of each individual dot.
  • Second: This is not the entire universe. What is shown is an accurate depiction of the nearest 400,000 galaxies to our own. Our current understanding of the universe places the number of galaxies on the order of 100 billion galaxies.
  • Third: we have every reason to believe that this map is accurate but it is small compared to the total; in fact this represents only 1/250000th of the Universe. According to our current understanding that means there are 70 sextillion stars in the Universe, and that can be written as 7 x 1022, or 70,000,000,000,000,000,000,000 stars.

With that in mind, now click on that link above and go and look at quarter millionth of the Universe. I’ll be waiting here for you once you have had your mind blown.

Silence. Perfect. No sweeping violins, crying guitars, or thudding electronica—just silence so you can appreciate the sheer scope. As Deforest Kelly once observed, in all that vastness, there is still only one of each of us. But out there, amongst all those stars and their attendant planets, it is literally impossible that there are not millions and millions of other living beings.

Even with our seven billion fellow humans on this little speck of dust, it is still possible to gaze longingly at the stars and wish for a friend. Wolves cry out over vast territories to communicate with others. Whales speak to each other over transoceanic distances. We had no problem speaking to fellow humans over 400,000 kilometers away on the Moon.

It’s certainly not difficult to imagine that an ancient and advanced civilization could send a radio signal which could reach this far. That’s why we humans spend so much time down at the ol’ watering hole.

The Water Hole

Interactions in our upper atmosphere, and impingement by solar winds, generate a great deal of radio noise. Just about every galactic phenomenon is radio-noisy. So how do we pick out the interesting bits? To answer that we ask ourselves how would we send a signal and how we would expect one to be received.

While most other forms of electromagnetic radiation, like gamma rays, UV, infrared, and x-rays are absorbed and scattered by the interstellar medium, radio waves cross the abyss relatively unimpeded. This is particularly so in the Water Hole, an area in the microwave frequency from 21 centimeters (1420 MHz) and upwards to 17.4 cm (1720 MHz). Hydrogen oscillates and emits at 21 cm, and when it combines with an oxygen atom, the hydroxyl (OH) molecule’s frequency is just a tiny bit shorter. If the hydroxyl molecule combines with another Hydrogen atom, it makes water (H2O) and resonates at four distinct frequencies within the range delimited by 1420 MHz to 1720 MHz, hence the name Water Hole.

SETI@Home does most of its work between 1418.75 and 1421.25 MHz, as discussed previously in this space. That is not merely because it is quiet in this area (relatively speaking) but because, as far as we know, water is essential for all life processes (as we understand them) and other “people” out there in the galaxy will probably recognize this as well.

SETI@Home is a distributed computing project. By clicking the link above you can download a screen saver which will grab a segment of the data collected by the Arecibo telescope in Puerto Rico, and whenever your computer is not busy, the programme will “borrow” your idle/wasted CPU-cycles and search for intelligent extraterrestrial civilizations.

The result

There is so much information to analyze, especially since the telescope gathers 35 GB of new scans every day. Each 340 kB segment requires 30 to 50 hours of analysis, including trillions of operations. You can do your part in one of the most important quests mankind has ever undertaken.

You might be the lucky one who grabs the segment that finally identifies the first intelligent signal from another race. Your name would go down in history as a co-discoverer! It’s worth a shot!