If you’re trying to come up with the best game plan for proving the existence of extraterrestrials, you’ve got plenty of options. Naturally, you want a strategy with a high chance of success, simply in the interests of time, money and a shot at the Nobel Prize.
For nearly 70 years the scheme favored by most scientists has been to look for signals — radio transmissions. That’s the classic approach of SETI (the search for extraterrestrial intelligence), and frankly, it makes sense. Radio can easily traverse light-years, and the technology for detecting it is well known and highly sensitive.