There is an expectation that we will someday receive a message that originated outside of our solar
system. One cannot expect that the ETs (extraterrestrials) clock will have a time base that is exactly the
same as we use.
The way we define our basic unit of time (the second) is by making each "second" equal to 1/86,400 of the
earth's rotation, at least we did it that way before it was decided by the higher powers that an atomic
standard should be used. Various ETs may use different methodologies to establish their unit of time. If we
are not using a common time unit certain types of communication become difficult.
If it was established that all galactic communication should be at an offset of 3.1415 MHz above the
frequency of neutral hydrogen (1420.4 MHz), we wouldn't be at the same frequency unless we used the
time unit established by the ETs.
The wavelength of neutral hydrogen is absolute throughout the galaxy, but when we convert it to frequency
we are using the wavelength formula. The wavelength formula uses the speed of light, and in our case the
speed of light defined in meters per second. In the formula, the length, in meters or feet or whatever,
cancels and the resullt are in cycles/second (Hz in our case). If ET uses a time unit that has a different
length than the second the frequency will be different. Thus if they add 3.1415 to their value for the
frequency of neutral hydrogen it will not be the same as when we add 3.1415 to our frequency value.
An absolute natural time base can be defined mathematically and an advanced ET civilization will have
found the same mathematical solution. It is natural because it is closely linked to the basic rotation
characteristics of habitable planets. It is natural because its basic form uses a simple right triangle and
the wavelength of neutral hydrogen as one of its legs. Any ET that can communicate using electomagnetic
waves will know the wavelength formula and the characteristics of what we call a transverse wave. I am
sure they know geometry. If we and ET(s) used the same time unit, 0.6255... less than the second, for
defining galactic frequencies we have a chance for communications if specific offsets are reserved for
intergalactic messages.
A couple of years ago I wrote a small article (18k pdf) about the time issue and it may be of interest to
readers of this forum.
http://www.vip.ocsnet.net/~ancient/TimeBase.pdf