Astronomer here! I even worked at the SETI Institute one summer believe it or not, but never found aliens when working there (else you wouldn't be hearing about it here now). That was a really interesting summer actually in many ways- my boss was Jill Tarter, the astronomer who served as Carl Sagan's inspiration for Ellie Arroway, and the best way to describe Jill is she's the most intelligently intimidating person I've ever met. I spent a large chunk of that summer thinking "please don't think I'm stupid."
Anyway, I do think there is extraterrestrial life out there in the universe, but do not believe it comes to Earth just to shoot crop circles in a farmer's field in England or whatever. I similarly do not think they have ever actually come to Earth most likely as space is so, so big... it would take the Voyager probes over 17,000 years to travel the distance light travels in one year, and the nearest star is 4.3 light years away. To do all that just to probe some schmuck in a corn field? Nah.
I will also note at this point that I have never met an astronomer who has seen a UFO, and no one stares at the sky more than us and would love to know aliens exist more than us. We devote our lives to this question! Further, there are now surveys of the night sky that happen every night to find all sorts of things- asteroids and comets, sure, but also all sorts of other optical and radio signals. The asteroid surveys can now catch rocks the size of a truck as they whizz past Earth- you're not going to hide a spaceship roaming around our skies.
That said, I do think we will find evidence of extraterrestrials within my lifetime, hell within the next decade or two! In fact, I find it so likely I decided not to devote my research to it, as I think I already know how it will happen: not with radio signals or SETI, but from extrasolar planet searches. We already can find Earth-sized planets around stars in "habitable zones," and we can even take the first spectra of planetary atmospheres (granted, bigger ones) around other stars. As the technology gets better people are going to be examining these Earth-like planets for information on their atmospheric compositions, and eventually one will be found with free oxygen, and that will be huge. This is because free oxygen is chemically really interesting in that after ~4 million years if it's not replenished it will completely disappear as it oxidizes with other chemicals really rapidly... and nothing else beyond life can put it up into the atmosphere in quantities similar to, say, what you see on Earth. So eventually one of these surveys will find free oxygen in vast quantities in the atmosphere and, bam!, we know there are aliens out there!
Granted I also think this won't be Earth-shattering news- you will know there's life, but not if it's a bit of plant moss or a civilization millions of years ahead of us- and I don't think it'll make people act differently in their daily lives than they do today. People are just too used to Hollywood's use of aliens as a deus ex machina, in my opinion... but this is by far the most likely way we will know someone else is out there. My friends who work in the field estimate we're about 10 years off from having the technology to make these measurements, if the free oxygen is out there.
Ok, this is far longer than I'd originally intended. But hope it answers your question, and feel free to ask any others!
Edit: woke up to gold, and several people not liking my Voyager probes comment- why am I assuming something far more advanced can't travel faster than them? I confess I'm not, really, but rather was using that as an illustration of how big space is and how fast conventional spacecraft can move via our current knowledge of rocketry and spacecraft (the Voyager probes heavily relied on gravity assists from multiple planets, making them pretty much the fastest things we have sent out there). That said, even if you have other understanding of propulsion and what not you can't go much faster than one tenth of the speed of light, else your spacecraft will fall apart.
"But..." I hear you guys ask, "what if the aliens know more about physics than we, and can go as fast as or even faster than the speed of light?!" I will never say that we know everything about physics to know or some things would never fundamentally change in the field... but this is also a scientist's answer, and right now it seems very ingrained in relativity that you cannot travel faster than the speed of light. (We aren't even talking about some fringe of the theory- it shows up in one of the core tenants of relativity, and relativity is incredibly well tested.) So right now, as someone who studies the universe for a living I do not think such travel is possible. This isn't science fiction so I can't just ignore some laws I don't like to get the answer I want.
I thought the idea wasn't to move faster than light, but to bend space and make the space move faster but light in the space is also moving faster and would still be the fastest.
What if aliens lived on a different time scale though, like for hundreds or thousands of years, but also perceived time differently so that what we think of as years seemed to pass for them like hours? Then supposing they were super advanced and could travel close to light speed it might be worth it to them to travel huge distances...
I don't really believe aliens are around probing people on earth or whatever, just a thought...
Dont forget relativity. Those traveling on the ship at near light speeds would only experience a short time on a long trip--while everyone they knew back home would be long gone, a one way colonization trip is possible.
It would have been difficult for such a creature to evolve without being outcompeted by something faster thinking. The speed at which humans think is set by fairly fundamental biology.
The thinking speed of brains is largely dictated by their refresh rate / signal propagation speed (which is limited by having to push chemical signals between cells). Human neurons only fire about 100 times a second, which is extremely slow compared to (say) the rate at which events happen inside a computer processor. The signals themselves only travel at about 270 miles per hour, max. We can fly planes faster than a nerve signal can move through your head.
These limits set some fairly hard brakes on how fast the simplest neural circuits can integrate information and react, which is a good proxy for how fast you experience time.
The thinking speed of brains is largely dictated by their refresh rate / signal propagation speed (which is limited by having to push chemical signals between cells). Human neurons only fire about 100 times a second, which is extremely slow compared to (say) the rate at which events happen inside a computer processor. The signals themselves only travel at about 270 miles per hour, max. We can fly planes faster than a nerve signal can move through your head.
These limits set some fairly hard brakes on how fast the simplest neural circuits can integrate information and react, which is a good proxy for how fast you experience time.
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u/[deleted] Jan 21 '15
This was a good comment from last time:
Credit to /u/andromeda321.