Mounting mirrors on the Moon and using them to signal across space could let ET know we Earthlings are here.
Ever since radio broadcasts began we鈥檝e been trumpeting our presence to nearby parts of the galaxy, so far without reply. To improve the chances of being found, Shawn Domagal-Goldman and Jacob Haqq-Misra of Pennsylvania State University in State College reckon we should cover half of the Moon with mirrors.
When angled to catch the Sun鈥檚 rays, the mirrors would increase the amount of light the Earth-moon system reflects by 20%, they say, more than enough to catch the eye of a vigilant alien astronomer. Domagal-Goldman proposes using a code of prime number flashes 鈥� just as aliens used to get in touch in Carl Sagan鈥檚 book Contact. This will ensure the flashes aren鈥檛 mistaken for natural variations in brightness.
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As a bonus, the underside of the mirrors could be covered with photovoltaic cells. When the mirrors aren鈥檛 busy flashing they could be flipped to allow the cells to make electricity, which would be beamed by microwaves back to Earth. 鈥淵ou could help solve the climate crisis, too,鈥� says Domagal-Goldman, who presented his idea last week at the 2008 Astrobiology Science Conference in Santa Clara, California, US.
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