Alien Contact

Instead, we’ll slew all the telescopes we can in the direction of the incoming signal. Every observatory that can aim its instruments ET’s way will do so. We’ll quickly know something about the type of star system that houses this newly found society, as well as its distance. In addition, we can hope to measure slow shifts in the frequency of the incoming signal, caused by the Doppler effect as the transmitter moves. Assuming ET is broadcasting from a planetary surface, we’ll be able to compute the length of the alien planet’s day, and its year.

SETI The mesage sent out from the Arecibo Telescope - could you decode it?

Message in a radio wave

All of this information will be exciting, yes, but what would really knock our hosiery off is to know what the aliens are saying. That requires additional work beyond detection. To make them more sensitive, the SETI receivers add up the incoming radio waves over fixed period – the time constant – which is typically a second or so. As a result, any variations in the signal that are faster than once per second are smoothed out and lost. A terrestrial TV signal, for example, varies about five million times per second, so if your home set were to have a one-second time constant, you’d find the telly a bore (or perhaps I should say, more of a bore). The screen would be a slowly changing, gray wash of light.

Simply shortening the receivers’ time constant isn’t the trick, however. That just weakens the signal and makes it noisier. What we need is to boost the signal first, so we can still detect it even with a shorter time constant. In practice, that means SETI researchers will have to build far larger telescopes than they have today - perhaps ten thousand times larger. That’s currently a financial impossibility, but if an alien signal is detected I fully expect that the money will be found to construct this super-instrument.

Suppose it happens. Suppose that we have not only tuned in to ET’s broadcast, but we are happily downloading the bits that constitute the message. These bits will be recorded and distributed for analysis. After years of work, either we will succeed in figuring them out, or we won’t.