The Intergalactic Stick

A longheld drawback for any element of humankind looking towards a
possible wormhole-free future of space travel and other-world
settlement has always been a restriction upon communication speed
between worlds.

Just as the speed of light has always been a speed limit on the
travel of matter (spaceships, etc) through space, so it might have
been assumed to be a speed limit on travel of information through
space. Faster-than-light space flight is restricted by einsteinian
physics, requiring something so far beyond our layman ken such as a
'hyperdrive system' or a 'wormhole'. Similarly, faster-than-light
information relay, for communications over the gulfs of interstellar
space, would seem to require going beyond our current paradigm of
physics, with, say, instantaneous telepathic thought transfer, as one
science fiction get-out method.

Generally the beyond-current-science ideas of science fiction do
indeed then become science fact soon enough after their birth in the
imagination, science trailing in their wake. However,
faster-than-light information transfer, allowing quick interstellar
communication, can be done without telepathy or wormholes. A good
old fashioned building project is enough.

Suppose that we established a colony in our nearest star system of
alpha centauri. Sending messages between systems by radio waves or
other electro-magnetic radiation, at light speed, it would take three
and a half years for a message to reach the other system. In the
event of, say, a catastrophe on one world requiring aid, those three
and a half years might be the difference between life and death for
thousands, with a rescue mission being years slower in coming than if
the call for help was recieved quicker.

So for the solution:
All that is required is the construction of a long interstellar
stick. With this, one world can poke at the other, The sending and
receiving of the 'poke' totally bipassing the problem light waves
etc. have of slowly crossing the gulf of space. As one end moves,
so, to all intents and purposes, does the other.

Unused outer planets and planetessimals in each system could be
utilized as the material for self-replicating Von Neumann machines to
build more of themselves exponentially. These machines would then
construct, out of themselves and out of further planetary material, a
long, thin, stick, from the outer rim of one solar system to the
outer rim of the other solar system. The project could begin at each
end and meet in the middle, maybe being completable in, say, twenty
years(?), if pressing. I have done the sums, you will be heartened
to know, and there should be plenty of material to make a
sufficiently long stick of a suitable width to be strong enough. The
next job is to send messages, in morse or other such code, by
prodding the stick at the other star system. Calculations show that
the amount of energy required to push the stick are not too vast, in
the region of gigawatts, if I recall correctly.

Thus, by pushing one end of the stick, a message can be sent to the
other end, three and a half light years away, which (if the stick is
designed to be rigidly brittle, with negligible contraction along its
length) will arrive by all intents and purposes instantly. In this
manner faster-than-light interstellar communication can be achieved.