Regarding ET's, evidence is a space ship, pieces of a space ship, an ET body, ET bones and DNA, a confirmed radio or other signal from intelligence not of this Earth. Where is this evidence? It does not exist. There is plenty of assumption, and fiction, and conjecture, and anecdotal stories, etc. but no evidence. As much as anyone, I wish we had evidence and/or proof of ET existence! But to date...we have none...
And there are many kinds of evidence. So you need to state which type you mean and then give an example. These are the different types of evidence: Digital evidence Personal experience Scientific evidence Testimonial Physical evidence Trace evidence Relationship evidence https://en.wikipedia.org/wiki/Evidence In the case of UFOs you need to include film evidence along with digital evidence, for older cases.
In the area of ET's...evidence and proof will need to be the same thing. A photograph of an alien space ship won't cut it as evidence of ET's...we will need the actual space ship or pieces of it. Anecdotal stories can't be called evidence or proof since they cannot be verified. We might say that since there are hundreds of billions of galaxies this is evidence of ET's elsewhere...but it's not evidence or proof. Physical possession of an alien space ship or bones of an ET, are going to be both evidence and proof. I understand what you are saying and/or asking, but in the topic of ET's, evidence and proof will be the same things...
That doesn't matter. Even a conjecture that turns out to be true is meaningless - unless it can be tested.
Many conjectures not testable at the time of their emergence, become testable later when new technology provides the opportunity.
When high energy/high technology civilizations make contact with low technology civilizations, the outcome has historically been pretty bad for the latter group. It's a safe bet that the best we could hope for is that they would view us as primitive and endearing "pets" to be studied and manipulated. If we have abundant resources that they need, all bets are off, as "the resource curse" of less developed civilizations usually dooms them. Good to see you here. Cheers, mate
that's been true on earth but I don't think that holds up for aliens and resources, the galaxy has endless resources I doubt we have any resources they can't find closer to home and take it much less effort and with no harm done...
yeah that is a possibility but why? ...protein or labour? ...even we have the technology to make protein now so they likely won't be eating us, and they'll certainly have far more advanced Ai and robotics than we do so our labour will be expensive(feed and shelter)... maybe if they just wanted a new home and merely wanted to evict us, that would be more plausible scenario imo...
To any aliens with decent telescopes, Earth is an interesting planet and has been for a very long time: orbits a main-sequence star in a habitable zone with unique visible bio-signatures. Paranoid/xenophobic/psychotic/my-religion-demands-I-destroy-you/ type aliens would have wiped us out long ago. Therefore, they don't exist near enough to us to worry about.
we've been announcing our technological presence for an extremely short time so even if they do exist I doubt they have detected us as yet...even if they have detected us and they have advanced space travel technology it'll be quite some time before they arrive... with the rate we're destroying our planet we may no longer be here when/if they do arrive, all they may find is a planet devoid of complex higher life forms
Aliens don't need to detect radio signals from us to determine this is a planet with life on it. Any technologically advanced aliens are going to be interested in planets with life on them, if only for reasons of self-preservation.
what bio signatures, CH4 ? CO2 ? H2O, O2... all are found on planets with no life as well, I doubt any alien is going to travel hundreds of light years to investigate solely on the evidence of trace gases that can also have natural non biological origin...early earth had all those and life and the planet was not habitable for any complex species... they're going to need more than that, an electronic signal(intelligent life) is what verifies a viable atmosphere.
I'm going to assume ET's share all the same issues we have in terms of limited technology, limited funding, over-population, depletion of resources, no new physics, duration of existence, no SOL travel, etc. This helps explain to me why we have not yet detected ET's and why we have no ET visitors to date. I think intelligent beings exist 'out there' but all sharing these same issues...
I agree the enormous scale of galaxy will be the same challenge all intelligent life faces...we've only been around for a paltry 160-200K yrs...our galaxy is 13.5 billion years old so I think the odds of other intelligent life in our galaxy over 13.5 billion years is a virtual certainty... if SOL was feasible intelligent life should've expanded across the galaxy by now or we'd have detected evidence of it nearby...that we detect nothing suggests to me the physics of SOL travel can't be overcome and there will most likely never be any contact with other intelligent life forms