How to Communicate With Aliens
If we want to send out a signal that aliens would understand and interpret as coming from a fellow intelligence, we need to speak a universal language; math and chemistry are going to be the same no matter where in the universe you go, so they will be the buildings blocks of our signal.
The Hydrogen Line is “the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms.” In extremely basic layman terms, this means a hydrogen atom jiggles up and down at a fixed rate, a frequency of 1420405751.7667 hertz (1.42 billion times per second). Now, aliens won’t share our definition of a “second,” but that doesn’t change how long it takes for the atom to oscillate once; for us, we define it as 1/1420405751.7667 of a second, but whatever you call it, it’s the same length of time.
Our signal should be sent out in pulses that last exactly 7.040241838 seconds each, because that works out to exactly 10,000,000,000 oscillations of a hydrogen atom. That’s 10^10 oscillations. Aliens may not measure time in the same units as we do, but they’d be able to infer from the length of each pulse that whatever intelligence sent out this signal understands physics and uses a base-10 counting system.
The full signal should last exactly 11 minutes 44.02418376 seconds, which is 100 of our 10^10 pulses. The pulses are in binary, either on or off, listing out the prime numbers from 1 to 100.
0110101000101000101000100000101000001000101000100000100000101000001000101000001000100000100000001000
And then the signal repeats itself. This is a non-random sequence; if aliens understand math, they know about prime numbers and would be able to recognize them. The fact that there are 100 pulses reiterates that whatever created the signal is using base-10, so the 10^10 pulses weren’t just a fluke. An intelligence chose a specific integer and is using universal constants to repeat it; there’s no way this is just background noise, this has to be intentional.
We don’t know where our target is, so we need to send it out as frequently and to as many potentially habitable stars as possible. We don’t want them to miss it, so we need to make it a regular occurrence, give them as high a possibility of discovering it as we can. This would be the most demanding part of the process, requiring a constant stream of data be sent out by facilities all around the world at all times, indefinitely, which is not an efficient use of time or resources. A project like this would require a lot of dedicated infrastructure, with no guarantee for results; this makes it next to impossible to hook investors. If we scale it back a little, maybe crowdsource it out so any private entity with a dish could send it out on their own time, that would make it more cost effective while only sacrificing continuity. Considering we’re doing nothing right now, even an unreliable/intermittent signal would be an improvement. Baby steps.
This signal wouldn’t tell them a lot about us, but it would let them know where we are and what we’re capable of. It stands to reason that a sufficiently advanced civilization would be scanning their skies for electromagnetic radiation; I mean, that’s what we do. They’re certainly going to want to understand the universe, so it’s not outrageous to assume that they’d be studying the cosmic background radiation and the spectra of their nearest stellar neighbors. The alien version of SETI or the James Webb Space Telescope may not be actively looking for us, but if they passively glanced in our direction, we want to make ourselves known. If they picked up a spike in low-frequency radio waves coming from a medium-sized yellow star, a spike with a definitive pattern, they’d figure out that something intelligent is calling out to them.
We want to let them know that they’re not alone.
