This line of reasoning normally results in wild fantasies. Yes it
is true that there may be other means of communication that we have
not discovered, but except for including an unquantifiable term for
percentage of communicating civilisation using EM transmissions into the
Drake equation, we cannot make even as good guesses about such alternatives
than the fundamental physicists whose profession includes finding any
that may exist.
A particularly bad example of this is the reasoning that, because light
travel time is an impediment to long distance communications, aliens
must be using faster than light means. The reality is that our best
current estimate is that such means cannot exist, and the fact that the
universe is a difficult place without them is not a reason why they must
exist; it may mean that there is not much communication, because it is
fundamentally too difficult.
Now, if someone discovers FTL communication tomorrow, those advocating
FTL communication will claim they were right all along, but in reality
they will still have been using false reasoning. The one case in which
it would be wrong to dismiss the possibility would be if real evidence,
or an elegant mathematical model made it possible, and experiments were
not carried out to confirm this.
> electromagnetic waves. What about anti-matter waves? What I'm getting at
We already have a reasonable understanding of anti-matter waves, which
are actually just a sub set of matter waves, which in turn are just
material objects! (A problem, of course, with anti-matter is that its
life expectancy in the local part of the universe is rather small!)
To me, anti-matter waves, as used here, seems more like the use of a
> is extremely limited in total spectrum when compared to the other possible
> ways of transmission. Who says aliens will be broadcasting anyways? Why
You are assuming that there are other possible means. This is unproven.
> would they care about broadcsating to us. We're assuming the aliens are
This factor, is I think, already in the Drake equation, and, although it
is a social science question, rather than a physical science question, is
almost as difficult to answer. The one thing here is that we are in a
soft science area and there are no fundamental laws, as far as we can tell,
that would prevent someone wanting to communicate and then one just relies
on chance that they happen to be within range.
Science fiction writers can invent solutions to problems for their own
convenience (the Star Trek transporter is a solution to the problem that
filming a miniature shuttle craft is was more expensive than filming a
transporter effect!), but in the real world we have to live with the
possibility that we might actually know the absolute limits in some
areas of physics. We may be wrong, but so is wishful thinking, when it
diverts too many resources.
We look in the EM spectrum because we know it is possible. We don't look
for chronon particles++, because, as well as having no evidence for their
existence, we don't know how to look for them. We can only use them when
and if another part of man's search for knowledge, fundamental physics,
PS People answering threads like this need to be aware that many people
do not feel constrained to work within known science, so the response
about optical SETI clearly showed a misunderstanding of the question.
(On the other hand, it is sometimes possible to assume someone is wildly
off track when they simply haven't explained themselves well.)
++ A fictional type of radiation in Star Trek.