Stephen Hawking thinks we should be concerned about aliens.  In a yet to be released documentary series, Hawking speculates about what might happen if our little blue dot where found by an alien civilization.

If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans,

And

Such advanced aliens would perhaps become nomads, looking to conquer and colonise whatever planets they can reach,

Let’s do some science.   Survey all the alien civilizations we know about and work out which are likely to do us in and which are our good friends.  Hmmm…. That’s a sample size of zero to work with I’d say, unless you take seriously all the talk of shape changing lizards and little green men.
Should we be concerned?  The earth has already been advertising its occupation by a civilization capable of radio communication for quite some time.  Marconi’s first reasonably good radio transmission was in 1895.  Trans Atlantic communication first demonstrated in 1902.
From time to time we’ve deliberately beamed radio communication out to the stars.
I’m sure Stephen Hawking knows the alien game is guess work.

The real challenge is to work out what aliens might actually be like.

Some notable skeptical bloggers have also had their say on this topic, such as:
PZ Myers, Phil Plait and the SGU team (listen to episode #250).
Will it be “War of the Worlds” or a friendly robot like C-3PO?  Will it be thousands of Daleks or Ford Prefect (just here to write a book entry)?

Is Stephen Hawking right?
Have your say, comment below.
Mal