Will Aliens be able to hear us?
I notice stories like this Alien Hunters story on BBC News. For example:
I Love Lucy signals are more than 50 light years away, and our nearest stars have already received Simpsons broadcasts
I see a problem with this. The way broadcasting has gone in my mind is this:
- 80 odd years of terrestrial analogue broadcast. Lets face it, 80 years in the age of the Universe isn't very long at all.
- Everything going digital - making it very difficult to decode, surely?
Since with digital terrestrial television, high definition is not as easy to do as with satellite, therefore most people switch to satellite and the popularity of digital terrestrial wanes. With satellite, the signal is directed to Earth and I assume not much of it reflects back.
Finally the trend prevails were most people just watch "TV" off the Internet. Making Digital terrestrial television even more irrelevant along with Satellite television.
So if broadcasting is replaced with the Internet how do aliens actually hear us? WIFI signals? I severely doubt they can travel into space and make any sense to decode.
The esteemed Adrian Tiplady from SKA adds over email:
They won't hear anything intelligible, thats for sure (even analogue, which is based on frequency or amplitude modulation schemes)! However, what aliens would 'hear' are the powerful radars (airports, meteorological etc.). That being said, by the time they detect us, many light years away, we would probably have destroyed ourselves so they won't have much to discover :)
If we discover "radar" being used be some far flung civilisation, couldn't it just mean a couple of whale like or bat creatures communicating? I.e. non-intelligent life form...
Yeah, but its fun to imagine though. Listen is the wrong term, but be that as it may, one of the key science programs will be to search for extra-terrestrial life. Although searching for artificial radio signatures (like radar) is one way, its more likely that a detection will come from natural radio signatures emitted from gaseous atmospheres (ala CSI).ie. organic molecules will emit radio signatures at a variety of frequencies - the most basic of elements, neutral hydrogen gas, emits a radio signal at 1421 MHz (just below GPS) There is a way to determine if something is artificial, or natural - although, its not an exact science! So, listening is bad word - think of it as a very sensitive car radio receiver. We are picking up radio emission. Your car radio demodulates the signal to audible wavelengths, but actually receives in the 87.5 - 108 MHz band (definitely not audible)!