Independence Day Special 2011:
Governments and Individual Rights
Internet Freedom VS On-line Piracy
Laws Must be Specific to Preserve Freedom
Checking Premises Statements and My Position
Date: Tue, 29 Jun 1999
Simultaneity
Thomas M. Miovas, Jr.
The problem of simultaneity seems to be the biggest barrier most
people have in understanding the ideas of Relativity. I think
I've come up with an example that might help to clarify this issue.
Have you ever watched workers putting on a new roof (or a
similar situation)? If you are some distance away from the
action, you may have noticed that the sound of the hammering
occurs in a manner that is disjointed from the hitting of the
nails. That is, you see the hammer coming down, but you don't
hear the sound of the bang until the hammer is up, making it
appear as if the hammer is hitting the air on the upswing and
making the noise. This occurs because light travels much more
quickly than sound, so you can see the hammer hitting the nails
(almost) instantly (say if you are only a block away), whereas
the sound travels much more slowly giving a time delay in the
hearing of the sound relative to the seeing of the hammer
hitting the nails.
Now, one may ask the philosophic question: Is the hammering of
the nails and the visual / auditory perceptions resulting from
this action occurring simultaneously? I think if one takes
perception seriously, as giving us evidence of reality as it
really is, then one would have to conclude that an observer some
distance from the action is *not* observing the sight and the
sound occurring simultaneously -- that these events (light
reflecting off the hammer and sound being generated by the
hammer) are not occurring at the same time *to that observer*.
To the person doing the work, the sight and the sound occur
simultaneously, but to a more distance observer, there is a
significant (noticeable) gap between the downswing and the sound
generated. To say otherwise is to assert that the worker
observes reality the way it really is, but the more distance
observer is not observing reality the way it really is. In fact,
both observers are perceiving reality the way it really is, but
if they compared notes as to when the hammer hit the nail and
when the sound was heard, there would be a disagreement.
Using a knowledge of physics -- i.e. the speed of sound, the
speed of light, and the distance between the worker and the
observer -- one could translate one observation to the other,
and that's what the equations of Relativity do for different
frames of reference. The significant difference between
Relativity and my example is that there is no way to get
information faster than the speed of light, whereas the
occurrence of the hitting of the nail visually occurs when the
nail is hit, but the sound is delayed (implicitly using the
speed of light as the standard for measuring the occurrence).
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