The biggest problem with beaming RF signals in all directions is the inverse square law. Simply put, for each doubling of transmission distance, the signal strength drops by a factor of 4. Visualize a lit flashlight bulb without any reflector in a dark room. The light spreads out in every direction evenly, so the bulb looks very weak. Put that same bulb in front of a mirror and it appears much brighter. Put it in a flashlight with a parabolic reflector and it looks very bright. The tighter the beam, the higher the intensity.
The amount of energy it would take to beam a detectable omnidirectional signal across lightyears would be staggering. That's why I doubt signals from essentially omnidirectional antennas like broadcast radio and TV stations would be detectable across lightyears. However, we have some RF signals that are both powerful and directional, such as BMEWS radars, that would have a much higher signal strength and would perhaps be detectable. Those signals also have characteristics that mark them as artifical, such as narrow bandwidths as well as precise but changeable pulse repetition rates.
Space/Science » in reply to not directly beamed
re: not directly beamed
The whole thread (30 posts)
- Is it time to scrap SETI? Of course not!
- SETI has a foolish perspective
- re: Is it time to scrap SETI? Of course not!