We know how to detect laser / radio transmissions pointed at us.

You can't see a laser transmission off-axis if there aren't any stray photons reaching your detector - that's just physics.

You can't detect a radio signal below the noise floor without some a priori knowledge about the statistics of the signal.

These aren't justifications, these are simply facts about the current limits of our ability to detect far-away signals. These limits suggest that millions of far-away worlds could be extremely chatty between themselves, but unless they decided to point a transmitter at us, we would be none the wiser.

You shouldn't use a measurement that looks identical for case A and case B to decide which one is more likely.

I appreciate seeing your comments. The Fermi paradox and these similar ideas seem the modern equivalent to assumptions the sun revolves around the earth. We need more research and infrastructure in this solar system to really progress on this.

Imagine if we had thousands of microsats in orbit around the various planets that we could triangulate data amongst? We need to be more aware of our solar system before we can even make reasoned arguments about life within it alone.

> before we can even make reasoned arguments about life within it alone.

That's an excellent point, for all we know we have intelligent, non-spacefaring life right in our solar system. It's unlikely, but there's still plenty of oceans, gas giant atmospheres and lava tubes that we haven't looked at yet.

Consider that we have, ourselves, gotten far harder to detect over the last fifty years. Energy spent accidentally sending signals into space is wasted. And we are making much greater use of cryptography and compression schemes, which would make signals look like pure noise.

So, question: how strong does an undirected, random signal need to be to be reasonably detected at 10 light years away?

Even more basic than that, why do we think radio/photons are the most efficient/effective way to communicate for an advanced civilization? Why would they be using them in the first place?

We already know neutrinos can travel through most mass, so modulating those would let you transmit through the Earth and Sun with lower latency and without a repeater constellation routing around the object.

Whatever aliens might be using to transmit information is likely more advanced than we're able to detect.

Yes, that's another example of tuning the parameter-space for a possible answer, just an unlikely one. Yes, maybe the Milky Way is just chock full of highly advanced technological species who have all made themselves very hard to detect and none of whom have any interest in communications with other intelligent life.

But a simpler explanation that has many more paths to being true is "there's nothing out there."

To be clear, I don't think the evidence suggests near-certainty here. I wouldn't say that there's a 99% chance that we're alone in the galaxy. But it's also not a wide open field. There is some evidence, and so far that evidence suggests that we're likely alone.

I think your assumptions about what is hard and what is easy to detect need some recalibrating.

Alien life forms wouldn't need to use technology to make themselves harder to detect. It's extremely difficult by default.

They would need to use technology to deliberately spread a message in a way that is at all likely to be detectable, and even then would still have to get quite lucky.

Encrypted data does not look like noise. It looks very very different from noise. If not, the entire concept of communications engineering wouldn't exist. We're always looking for the next sharply bounded filter.

Well, that should be just temporary before our real mega engineering projects get started. Hard to not notice those, even just by the expected heat signatures.

> Why haven't some of them noticed us?

Maybe they have?

We don't "contact" every pack of deer that we notice.

Deer sure as hell know we exist.

Certain deer do, certain deer dont. Also, feel free to use a lower animal if that abstraction works better for you. My point is that if humans are some out of the way primitive life form it might make sense why aliens may know of us but not contact us (as in, there may be no purpose to explicitly contact us, as humans dont generally try to explicitly contact every deer herd).

It is not that humans are technologically primitive (which we are), it might be we are too intellectually/capacity primitive to be seen as "contact" worthy.

Ants then. Or even bacteria.

Further, think about how powerful a transmission has to be in order to not be drowned out by the power of a star. A laser would have a far higher chance (yet still hugely powerful to cross the distance), but only if aliens found us and pointed a laser directly at us.