The science behind the probability of extraterrestrials

[MrFun]

I have a question -- can the type of extraterrestrial life out there determine the length of time it can take for us to come into contact with them?

For example, would it take shorter or a longer period of time to discover more primitive, non-intelligent extraterrestrial life? It could take shorter time, because more primitive extraterrestrial life is likely to be more common throughout the universe given their greater biological/evolutional simplicity.

On the other hand, it could take longer to discover non-intelligent ex-life because they have no technology to facilitate any kind of communication. Our discovery of them would have to rely solely on our efforts to reach out to them.

And similar line of thoughts in regards to intelligent, more advaced ex-life. It could take shorter time to come into contact with them, because they could have the technology to reach out to us, while we are making the same effort to reach out to them.

On the other hand, it could take longer, because intelligent, advanced ex-life is likely to be less common than more primitive, non-intelligent ex-life.


So what are other people's thoughts on this?

[MichaeltheGreat]

Originally posted by Dr Strangelove
I find that difficult to believe.

Dauphin's likely right - our sun isn't a big radio source. If it was, we'd be screwed from using radio ourselves. (There is a slight indicator for the relative effect of solar radio, and that's the greater range of FM and particularly AM band and shortwave radio signals at night for a given transmitter location and signal strength.)

The total radio transmissions from every piece of radio broadcast equipment on the planet is distributed amongst a broad range of frequencies. If you compressed all of their signals into one band you'd probably have random garbage that would be difficult to distinguish from star noise and other background cosmic radio signals. In order for someone from a distant star to distinguish the signals that we make from the background he's going to have to narrow his reception down to one source or relatively few sources in order to determine that the signal has an orderliness to it imposed by an intelligent broadcaster.

Carrier waves and subcarrier waves are what we look for, and what any radio-discovering intelligent extraterrestrial would look for - the physics are universal, and although they'd undoubtedly pick different bands and carrier characteristics, they'd notice (if they exist and looked) the very non-random nature of our high point source broadcasts. Finding approximately 100 exact steps in carrier frequency in a low-energy band from ~500 to ~1500 kHz ain't random noise, especially when it's in continuous emission at approximately the same signal strength on each step.

The difficulty isn't in understanding the radio signal, it's pointing at the right spot in space with a high enough gain antenna to find it in the first place.

[MichaeltheGreat]

Originally posted by MrFun
I have a question -- can the type of extraterrestrial life out there determine the length of time it can take for us to come into contact with them?

For example, would it take shorter or a longer period of time to discover more primitive, non-intelligent extraterrestrial life? It could take shorter time, because more primitive extraterrestrial life is likely to be more common throughout the universe given their greater biological/evolutional simplicity.

On the other hand, it could take longer to discover non-intelligent ex-life because they have no technology to facilitate any kind of communication. Our discovery of them would have to rely solely on our efforts to reach out to them.

And similar line of thoughts in regards to intelligent, more advaced ex-life. It could take shorter time to come into contact with them, because they could have the technology to reach out to us, while we are making the same effort to reach out to them.

On the other hand, it could take longer, because intelligent, advanced ex-life is likely to be less common than more primitive, non-intelligent ex-life.


So what are other people's thoughts on this?

I think it's entirely possible that there are thousands of versions of intelligent life existing at any given time in the mid-life of this galaxy, and equally possible that none will ever definitively detect any other, due to the daunting physics, biology and engineering issues involved in definitive detection.