Personally, I don’t think there’s enough information to make a statement like “hard to imagine a scenario in which moons like ours are common”. My expertise is not in planetary system formation but my understanding is that in the early days of a protoplanetary disk, many objects may form. Some may collide, some may be ejected.l due to the developing gravitational dynamics at play.
I agree. The problem is that any measurement has a margin of error, no matter how small, so I'm afraid it's impossible to prove with certainty even that space is flat, and in any case, as you wrote, anything far beyond the observable universe cannot be verified or falsified.
For sure; But it's fairly hard for me to imagine such collisions being very common - space is very big, and planets are very few, making them hard targets to hit.
I guess I can’t argue with a hunch.
Sagan's formulation is good for estimating the number of such civilizations that exist, but Drake's original was estimating the number that are detectable.
The thing is when we look deep enough we see an environment very different than our own, one probably unsuitable for life. (Too much wild energy, too little building materials for planets.) This says change over time which says it's not anything like a steady state. Furthermore, gas gets swept up into stars and burned. Some gets thrown back but nothing like all of it, thus it's resource that will in time run out. If it's finite in time why would we think it's finite in space?
40% of the objects in our solar system that could have formed a giant moon from a glancing planetesimal impact possess giant moons. Our moon isn't rare.
In one sense it's a big coincidence. But the coincidence is that we happen to be here at the time that it occurred. Giant moons will either tidally lock or will slowly move away from their planets. Thus a time when they match is likely.
Cancel out is very much a ballpark answer, we could easily be off by a few orders of magnitude. I do agree that L is the critical term, though. The signature of a species will become more and more obvious as technology progresses and thus the detection range will go up. Earth's spectrum in the radio band will look very wonky out to a range of tens of light years (assuming a big enough dish doing the looking.) We have some big emission lines at frequencies that nature isn't going to produce. And doppler will show said emissions are coming from a planetary surface.
You're assuming detecting a signal. But Earth absolutely shines in the radio spectrum for no apparent reason. You don't have to be able to detect individual signals to see that.
I do not find the definition meaningful as a sufficiently advanced civilization should not die with it's planet.
No, Frank Drake is. He defines L as:
No, it really doesn't. Where do you get the idea that it does?
Indeed, no reason why it should is apparent to me.
If we were somehow emitting enough RF radiation to swamp individual signals, radio would be useless to us, as every signal was swamped by the noise.
can you quantify the radio brightness and compare to other sources in the solar system?
