If there was a planet/moon/whatever with intelligent life at the exact same technological level as humankind is right now, would we even be able to find them? And if we found them, would we be able to communicate with them in any meaningful time frame? Would it make a difference if they were say on the same side of the galaxy as we are? What if they were on the opposite side of the galaxy, or towards the center of the galaxy? Is the distance just too prohibitive?
Also, if a spaceship were to enter into our solar system, would we notice it right away? Or do we not have the ability to monitor our solar system?
The answer to all your questions is probably no. The current state-of-the-art in RF receiver technology wouldn’t allow us to even detect our own level of television and radio transmissions from the nearest star, about 3.8 LY away, let alone across the galaxy, which is about 100,000 LY in diameter. Unless they deliberately directed a transmission our way, we’d never know they were there. There’s a similar problem with detecting spacecraft. The sky is an absolutely huge place, and a spacecraft would appear so tiny, we’d never see it unless we happed to have a powerful telescope looking right at it. At any given time, we can probably manage to watch less than 1/1000th of a percent of the sky at once, at a WAG, to a resolution sufficient to spot a large spacecraft entering our solar system, and even then we wouldn’t know it WAS a spacecraft until it got close enough to resolve its shape.
If it is under power (i.e. not in a ballistic orbit) then we’d be able to discern from it’s track that it is artificial. But that’s harder than you’d think; assuming it’s heading more or less directly for the Earth, you are going to have a very limited ability to estimate distance or velocity by parallax. If it using some kind of reaction drive (fusion, say) then you should be able to determine that by spectroscopy of the hot exhaust, but again, you need to know where to look and that there’s anything worth looking at, and as Q.E.D. points out, we just don’t have the resources to maintain anything like a comprehensive view of the celestial sphere.
We certainly wouldn’t be able to detect a present-level civilization at any but the closest stars, if that. At best, we might notice a slightly elevated level of radio frequency energy, but it’s doubtful we’d be able to identify it as being artificial. (The actual content of the signals would be so distorted and dispersed that even with some advanced method for detecting the carrier we wouldn’t be able to discern the information within.) As far as detecting anything toward or beyond the core of the galaxy (in the direction of Sagittarius A) there is so much interferring dust, plus extraneous radiation, that we basically can’t see anything in that direction.
Communicating across interstellar distances will effectively be asychronous; you send a signal, and ten, or fiften, or fifty years later, they get it, try to decode it, and send a reply, by which time the original communicators have lost their budget, or have moved on to philately, or have died off. Reaching out to touch someone is all well and good, but the phone bill is enormous.
Here’s a concept to chew on, though: two hundred years ago, we were still reading at night by burning fat; a hundred years ago, air travel was the purview of a few lunatics who were (literally) full of hot air; today, we put people in orbit (though not without risk) and build compact machines that can perform more calculations in a second than a warehouse full of accountants could do in a lifetime. What is the likelyhood that we will have any kind of technological parity with humanity five centuries into the future? Similarly, an intelligent alien race is almost certainly at some differing level of technological (and social, and intellectual) development than we are now. Even for a race but a few millennia advanced from us, we might be like infants, not only not worth talking to but not even capable of communicating on any meaningful level.
Heck, it’s hard enough to find intelligent life next door…especially if you live in Washington, D.C.
It is not just our current level of technology that is the problem. It is a fundamental problem of physics/math. The universe is fairly noisy so it will be very difficult to separate the noise from the signal unless the people transmitting the signal are setting up the power/bandwidth to transmit across the stars. If you are not planning to have a signal recovered at great distances you generally don’t spend the energy or bandwidth needed.
Undoubtedly, it would immediately head for a deserted trailer park in the rural United States, immediately pick up a test subject, perform demeaning medical procedures, and then return him home.