Hi Josh,
Great question. Physics is an experimental science, and we test
our models and hypotheses against observations to check to see if they
are favored or excluded. Observations can take a large variety of
forms. Many observations which can be done with our built-in senses
have been done many times over, and so the discovery of previously
undiscovered physical principles usually involves the use of some kind
of equipment or other. Although you certainly can discover stuff with
your own senses! Like a new comet (telescopes help, but for the most
part it just involves someone looking in the right direction at the
right time), or a new species of plant or animal. Or you can measure
important things, like the length of your shoes, without complicated
equipment.
But some phenomena require apparatus which extends our ability to
perceive stuff. I work in the field of experimental elementary particle
physics, and we require sensitive electronic devices, and sometimes big
piles of steel and lead, all arranged with high voltage and
electronics, to pick up the faint traces that individual particles
leave. If some interaction or phenomenon has any impact at all on
something else, then it can be detected in some way with some piece of
apparatus. Example: even if we cannot see evaporation, we can infer it
by its effect on a glass of water (the effect is easier to see if we
let something sit out and evaporate for a long time). Even though we
cannot see X-rays, we can detect them with photographic film or
electronic detectors. Even though we cannot see neutrinos, and they
only very seldom interact with anything, we can amass a large quantity
of water in a tank and look for individual flashes of light created by
the electrons or muons created during one of the rare neutrino
interactions. Or we can put a whole bunch of gallium together, and
screen it chemically after waiting a while, to see how much of it has
been chemically altered by neutrino interactions.
So -- our ability to perceive stuff is really limited by our
imagination and available technology. If we would like to perceive
something which interacts with something else in any way whatsoever,
all we have to do is put together the right piece of equipment and
devise the right way of interpreting its results.
Tom
p.s. of course it would be cool to directly 'see' things by other
senses, the way bats 'see' things by sound or platypus' 'see' things
electrically. Unfortunately we can't really imagine what those
sensations are like. As for getting information information about some
side of nature that can't be reached by any instruments, that seems
far-fetched. Anything that interacts, directly or indirectly, with
ordinary stuff should someday be detectable by instruments, as Tom
wrote. Now if there were something that had no interaction of any type
with ordinary stuff, it wouldn't make much sense to talk about it. Mike
W.
(published on 10/22/2007)
