Hawking’s commentaries:
– Cites examples of what happened to Native Americans when Europeans settled.
– Also gives examples of ‘harvesting’ technology that could leave the Earth barren, or crippled.
– A cornerstone of his argument seems to be that advances in technology leave people cold and uncaring… nowhere in his statements does he explore the possibility of benevolent aliens.
– All of this was basically a response to the idea of “METI” — an active broadcast targeting alien civilizations.

Response from Douglas Vakoch @ SETI:
– “Even if they tend to be hateful, awful folks, can they do us any harm at interstellar distances?”
– Vakoch said it would take quite a lot of time and energy for extraterrestrials to come all the way to Earth to wage war or try to extract resources from our planet. The cost of traveling here to collect them, not to mention transporting those resources back to the aliens’ home, would far outweigh the benefit, he said. [The Strangest Extrasolar Planets]
– Seth Shostak @ SETI agreed. “It’s completely analogous to ordering a book from Amazon and paying $60,000 for shipping,”
– Link:  Interview w/ Seth Shostak (audio + transcript)

And furthermore, it’s too late to worry about it anyway:
– Signals used to transmit television and radio have been getting sent off into the cosmos since they were invented (approx. 60 years, now).  If anyone’s listening, and points in the right place, they’ll find us whether we’re telegraphing our presence or not.  It’s too late to turn off the signal.
– The earliest episodes of I Love Lucy have washed over 6000 or so star systems, and are reaching new audiences at the rate of one solar system a day. If there are sentient beings out there, the signals will reach them.

When the Allen Telescope Array comes online in 2015, SETI believes it will be less than 2 dozen years from that point, before the first alien civilization is discovered.
– Based on recalculations of the Drake Equation.
– SETI researches note that it could take an incredibly long time after that though, to actually be capable of interpreting whatever data might be received.

FASTER THAN LIGHT:

https://en.wikipedia.org/wiki/Faster-than-light
To summarize — the currently accepted special theory of relativity states that traveling AT the speed of light, would require an infinite amount of energy.  Going beyond it would require more than infinity.  Which doesn’t exist, so stop trying.

But if Hawking and others are worried about visiting aliens, then there must be a way, right?

So…. what are the leading theories?

1)  Ion Thrusters
– Already in use!
– Not powerful enough to break gravity fields, but incredibly efficient for long-term travel.
– Cannot break the speed of light, but over very long periods of time, can get very close with relatively little expenditure of energy along the way.

2)  Warp Travel (a la Star Trek)
– Most theories state this as a “relatively reasonable” idea of circumventing relativity.
– By creating ‘curves’ or ‘bends’ in space, you can shorten the distance needed to travel from one location to another.
– Would still need to be accompanied by powerful acceleration methods.
– Working theories known as the “Alcubierre Drive” in real life.
PROBLEMS:
– Warping space takes a crap-ton of energy.
– There’s no working model to “stop” the warp wave.

3)  Transversable Wormholes
– Under current physics models, the amount of energy required to punch a hole in space is astronomical, and there is no known way to guarantee where the other end would be located.
– Also would require being held open by a “sphere of exotic matter” which does not currently exist.
– However, perfectly logical if these issues were overcome.  Believe it or not, this could be more likely than other theories, despite the outlandish issues involved.

4)  “Super Force” drives
– According to Big Bang Theory, the universe is currently only about 14billion years old.
– But, it’s more than 150 billion light years across.
– The difference is solved by a theory known as “inflation” — in the universe’s infancy, the forces of Gravity, Magneticism, Strong and Weak Nuclear, were all a single Super Force, which was strong enough to ignore relativity and allow matter to travel faster than light.
– Scientists at the LHC are attempting to discover this Super Force. If harnessed, it could allow FTL travel by circumventing relativity.