I recently had the opportunity to attend a lecture by Harvard Professor Paul Horowitz. It’s a name you likely recognize. He is best known for his iconic book the Art of Electronics which is often referred to not by its name but by the last names of the authors: “Horowitz and Hill”.
Beyond that, what do you know about Paul Horowitz? Paul is an electrical engineer and physicist and Paul has spent much of his storied career learning and practicing electronics for the purpose of finding intelligent extra terrestrial life.
Link Budget: How Quietly Can We Hear?
The first thing Prof. Horowitz taught us was that the signal-to-noise ratio (SNR) over 1000 light years with an Arecibo-equivalent antenna at each end is four orders of magnitude above the cosmic background radiation. That is quite good for communications. It is entirely plausible to transmit signals between intelligent extra terrestrial civilizations if they exist and this plausibility motivates the search for extra terrestrial intelligence (SETI).
Paul’s involvement goes way back. On of his earlier contributions to SETI involved the use of conventional dish-based radio telescopes, listening at 1425 MHz, looking for strong narrow band emissions. One example is his ‘suitcase SETI‘ system built from wire-wrap boards and other early 80’s tech. Many such emissions were detected and logged, but unfortunately the duty cycle of observation was so low that they were never able to confirm.
Duty Cycle: How Frequently Can We Listen?
The key to SETI is duty cycle. ‘Pencil beam’ radio telescopes proved to be limited by the fact that they could only look at one signal/direction at any given time. Software was in place to quickly re-visit for several minutes in the event of a narrow band signal detection, but none of the many narrow-band extra terrestrial signals were ever confirmed (observed more than once). Paul chalks this up to duty cycle, the percentage of time and area of the sky searched. In other words, the more area of sky you can search and the more often you can search it, the better your chances for a SETI detection.
With this in mind, Paul is leading the development of a new optical sensor array assuming that ET might be trying to reach other intelligent civilizations via pulses of coherent light. This effort will use two separate arrays that can see the entire sky above their location at the same time. Two arrays are used so that coincidence detection can filter-out spurious signals, where the same pixel on both arrays must trigger a detection at the same time in order for any detection to be logged.
View the lecture for yourself here:
Are We Alone? Are We Alone in Our Own Galaxy?
We are almost certainly not alone. We are probably not even alone in our own galaxy. But according to the Drake Equation it depends on how long an intelligent civilization will last (L) before either destroying itself, its planet, or being wiped out by a celestial event. A large L factor increases the number of overlapping advanced civilizations thereby increasing the likelihood that transmissions will be exchanged. Lets just hope that the average value for L is very high!
What an experience to meet Paul Horowitz and hear first hand his experiences building equipment to listen beyond our civilization. I have been a fan of SETI since early in my engineering journey, and I even built a radio telescope receiver in high school. There are still so many frontiers to explore, and building custom hardware to communicate with sources of unknown origins, using unknown technologies and protocols is a great place to let your skills wander.