3 ms·
There's around 512 G-type stars in 100 light years radius around us. That's not many. Milky Way radius is 100 000 light years. If our galaxy had lots of civil
by ajuc 9y ago
There's around 512 G-type stars in 100 light years radius around us. That's not many.
Milky Way radius is 100 000 light years.
If our galaxy had lots of civilizations that just learned radio in last 100 years - odds are quite high that we wouldn't be able to detect them YET, even if we had the technology to do so.
- davedx 9y agoI understand the probabilities involved. The OP made a rather extreme claim that 'the universe could full of earth-level societies and we wouldn't know'. If all 512 G-type stars in 100 light years had earth-level societies, we would be able to detect their higher powered radio transmissions. Right?
- KineticLensman 9y agoOnly those transmissions that were timed (travelling at the speed of light) to arrive in the small number of decades where we have been listening. Other constraints may also apply
- joe_the_user 9y agoEven Seven light years is a vast, vast distance. The limit isn't 100 light years, it's something like one or less light years. Any ordinary radio transmission dissipates the square of the distance involved. At a certain level, transmissions become so faint they are indistinguishable from quantum noise. You can find the math done on Quora (apologies for semi-walled-garden link). Remember, there's difference between getting a signal whose properties one knows and getting arbitrary signal - if there a strong GPS transmitter or something we knew, we could wait long enough and get micro-data. But arbitrary signal, no, information theory says no. (read all the answers together). https://www.quora.com/How-far-can-radio-transmissions-from-Earth-travel-toward-other-stars-before-they-are-so-weak-as-to-be-practically-undetectable https://www.quora.com/How-far-can-radio-transmissions-from-E...