Quite simply, we can’t. At least not at the power levels we are using. Radio signals will drop well below the noise floor before they’ll get to the nearest star. The only signals we detect originated as cosmic level events and had a proportional amount of transmit of power. Even if we sent a powerful message in a specific narrow band concentrated in a tight area such as our closest star proxima centauri, any residents there would have to have a receiver selective enough to receive it, pointed in our exact location at the exact time it arrives. That’s if the signal can still be detected after 4.5 light years. It’s a fool’s errand IMO.

There really is no “bubble” of radio waves expanding from earth, not detectable ones anyway.

I’m sure @Blackwater_Park is correct on the physics. As far as the encoding, I would think we could try to mimic the output of a pulsar or something but instead of pulsing a constant signal, we could output pulses that correspond to the prime numbers up to 1000 and then repeat. The message is essentially “Something intelligent is here.”

There are two issues here.

One, as described above, is the purely technical piece of sending messages over a certain wavelength at a certain amount of power and hoping that something out there is listening.

But the second, equally important piece, is comprehension. Even if the other end is physically able to receive the signal, will the content of it be comprehensible to the aliens at the other end?

I know that the US spent a ton on those golden laser disks that they sent into space a long time ago, and various other things that showed how humans look. And some basic mathematical stuff as well. But our best guess is no guarantee that the creatures at the other end are going to be able read, much less comprehend, what we are saying.

What did Marshall McLuhan say – the medium IS the message.

I am ignorant of the physics of light. Could we use a laser to send pulses of light? Is it strong enough?

@Hawaii_Jake I’m not an expert, so this could be wrong but there are a few problems with your suggestion. Lasers have an extremely narrow beam, so the only thing that could see the pulse would have to happen to be in the path of the beam. It would be like trying to paint a barn with a paintball gun instead of a paint sprayer. Also with all of the dust and stuff in interstellar/intergalactic space even an extremely powerful laser would quickly become undetectable.

^Thanks.

There’s also the question of whether it’s wise to attract attention. They could be evil.

@Hawaii_Jake: That’s what the late, great Stephen Hawking said. He said we should stop sending out signals that we are here because we don’t know what’s out there.

We may be like a bug under the shoe of some invaders. Scary.

If the otherwordly beings are out to destroy us, and they’re technologically advanced enough to get our signals and travel through space, they’re going to destroy us no matter what – whether we call attention to ourselves or not.

If there really are intelligent alien civilizations out there, they already know about us.

@elbanditoroso: You and Stephen disagree. Here’s one of the articles that details his thoughts: https://www.newsweek.com/stephen-hawking-death-alien-contact-aliens-theory-ufo-search-breakthrough-844920

@Hawaii_Jake It is a concern that in the (unlikely) event that some message sent were to attract the attention of some other form of intelligent life, we make the mistake of assuming them to be benign. We may just be, to them, like some form of vermin to be eradicated.

@NovDel Correct. We’ve watched too much TV and believe that technological advancements accompany advancements in compassion.

There is a big difference between being able to transmit messages and being able to transport an army a distance of at least several hundred lightyears. That would be quite an advanced civilization.

@Hawaii_Jake More Independence Day than ‘live long and prosper’, perhaps.

Math and Music is the way to do it.
Both contain identifiable patterns.
Morse code would be one way to send math. Music is obvious. Unless the species cannot hear audio, which is possible.
The odds of extra-dimensional entities being contacted is probably greater than the odds of extre-terrestrial entities being contacted. But I say that with an obvious human 3D bias.