What Signals Would An Alien Civilization Detect?

We’ve been listening for alien signals for several decades, though the silence has led as many to wonder if we are listening for the right things as those wondering if there are any aliens at all. What many fail to understand is how many signals a civilization like ours produces that are lost to the background noise before anyone outside our system would hear it, much less what they might learn if they were able to pick up our signals?
What signals would an alien civilization detect? And what could they learn about Earth from what they could receive from human transmissions?

What Won’t Aliens Pick Up

Aliens won’t be watching standard television broadcasts. After all, these signals are lost over a hundred miles away unless they are satellite TV signals. And satellite signals …show more content…
These are military radar and satellite uplinks. Let’s look at why aliens could detect these signals and what aliens would learn from each.

Military radar (and traffic control radar) has several advantages over other types of signals. First, it is put out by massive transmitters to look for threats and aircraft – that’s enough power to actually cross the distance when combined with other signals. Second, these frequencies aren’t competing with RF output created by the solar and Jovian electromagnetic fields. So the military radar signals from the Cold War looking for incoming ICBMs are still traveling through space and stand out to any aliens listening on those frequencies.
Air traffic radar, military radar and similar applications are still using these frequencies, too, so our planet continues to radiate them. Take this in contrast to the shift to internet communications from television, causing demand for TV broadcasts to go down, and satellite radio and internet radio potentially killing the radio transmissions we once thought would cause aliens to discover Earth by listening to old rock