some virtually instantaneous method of getting a message
from somewhere to anywhere. Any time lag, no matter how
small it seems at first, has a way of becoming major as longer
and longer distances are involved. Sooner or later we must
have this instantaneous method, or we won’t be able to get
messages from one system to another fast enough to hold
our jurisdiction over outlying regions of space.”
“Wait a minute,” Dana said. “I’d always understood that
ultrawave is faster than light.”
“Effectively it is; physically it isn’t. You don’t understand
that?”
She shook her dark head.
“In a nutshell,” Weinbaum said, “ultrawave is radiation,
and all radiation in free space is limited to the speed of light.
The way we hype up ultrawave is to use an old application
of wave-guide theory, whereby the real transmission of
energy is at light speed, but an imaginary thing called “phase
velocity” is going faster. But the gain in speed of transmis-
sion isn’t largeby ultrawave, for instance, we get a message
to Alpha Centauri in one year instead of nearly four. Over
long distances, that’s not nearly enough extra speed.”
“Can’t it be speeded further?” she said, frowning.
“No. Think of the ultrawave beam between here and
Centaurus III as a caterpillar. The caterpillar himself is
moving quite slowly, just at the speed of light. But the pulses
which pass along his body are going forward faster than he
isand if you’ve ever watched a caterpillar, you’ll know that
that’s true. But there’s a physical limit to the number of
pulses you can travel along that caterpillar, and we’ve already