Here in the U.S. we are converting all of our tv broadcast signals from analog to digital for the first time since people started broadcasting television signals. It indicates an advancement that is potentially detected far beyond our own blue marble. It prompted a thought about SETI’s search for an alien civilization’s broadcast signal over the years, and how we might be able to detect their rough level of advancement if we listened long enough.
There’s some hypothetical assumptions we have to make to illustrate this idea. First, that we have detected an alien civilization’s broadcast signals and have been listening for a while. Second, that we have been able to get more information from the signal beyond the fact that it exists. It not only has to be strong enough to be detectable, it must still be carrying information we can decode.
A fact that has been widely talked about over the years is that since people started broadcasting radio in the early 20th century, there has been an ever-expanding envelope of radio signals emanating from the earth and into surrounding space. By now, its possible that our earliest radio and tv signals have spread across a volume of space almost 90 light years in all directions. There are thousands of stars in this small region of space, and a sufficiently advanced civilization living out there could have been listening to us for decades.
In our scenario, lets switch roles. We have detected a civilization that isn’t too far away and have been recording their broadcasts for a number of decades. Over the years, we’ve seen their signals get stronger and more sophisticated. If we are able to interpret their broadcasts, we could get a lot more information about their societies that would add to our estimates of their development. Depending on the rate of change over time, we can make rough estimates about their level of technological advancement.
- If the change has been slow, we might assume they have are advancing at a slower rate than we are.
- Alternatively, we might deduce they are advancing more quickly than us.
- If we detect a variable level of complexity in their signals over a long period of time it could indicate a civilization-wide war, natural disaster, or even economic collapse has occurred that set them back.
- Finally, if their signals stop suddenly and never return it might indicate either a complete collapse or it could be an indicator that they have gone through their own Singularity.
Point 4 has some special meaning. If the complexity of another civilization’s signals have steadily increased over the years and then suddenly stopped or drastically altered in a short amount of time, this could be interpreted as a very good indicator of a Singularity event. Depending on the civilization’s distance from our own and how long the delay is between when it was broadcast and when it was received, this could be an early warning indicator that we could be on the receiving end of first contact in a short amount of time. It might be our only warning before we encounter whatever came out the other end of their Singularity. A short review of human history teaches good lessons for what happens to the less-developed in situations like that.
We should look at our own progress over the last 100 years and imagine what another species nearby might be seeing.