> J W was thinking of things that travel through space:
> Light -- EMF
> Gamma rays -- EMF
> radio -- emf
> cosmic radiation -- emf
> other radiation -- emf
> Heat -- doesn't travel in space (radiation that produces heat does)
JW, other earlier forms of distance communication were also EMF. smoke signals -- light (EMF) reflected from them is intercepted by our eyes semiphore -- see above sign language -- see above
Other than war drums, I cannot think of *any* long distance communication that does not rely on EMF. The ETIs will grok this, I can assure you. spike