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The Philippine Journal of Science 
1921 
in the sense that they are entirely independent of the “frame 
of reference” of the quantity to be measured. The only 
specification is the manner in which quantities shall be measured 
when using these units. 
The question remains as to whether units thus defined would 
be intelligible to an observer on a planet of Sirius if, he did not 
know his relative velocity, and without the use of “light- 
signals.” Certainly, when we have the comets under better 
control we can write the definition in Inter-stellar Esperanto 
and mail it to him. I see no reason why his electrons should 
not have the same apparent properties as ours. If they do 
not it would be necessary for him to remove some of the 
“Earth” electrons from the letter we send and measure their 
apparent properties. The Principle of Relativity tells us that 
these would not have changed in changing the “frame of 
reference.” 
With units independent of “frame” the problem of simul- 
taneity is simple. It is generally admitted that a position- 
time coincidence is a simultaneity. But after this coincidence, 
time keeps “flowing on,” as Newton said, for each particle 
in the same absolute units. Therefore any two particles 
which ever have been together have absolute simultaneity, 
measured by the number of seconds which have elapsed since 
their coincidence. Similarly these particles may impart their 
absolute simultaneity to other particles by coincidences with 
them, and therefore any two bodies possess absolute simul- 
taneity if any connection between them has ever been established 
by coincidences. To suppose that they really do not possess 
this property unless they have been so connected is to assume 
that the smallest particle may have an enormous effect on 
the largest star. 
I would not dwell so minutely on this subject but for the 
pernicious and widespread effect that the “light-signals” 
doctrine has had and is still having. I hope I have been 
able to show that it is in no sense a true representation of the 
Principle of Relativity. There is no necessity for allowing 
our intuitions to prejudice us against the Relativity Principle. 
On the other hand there is no excuse for allowing the Relativity 
Principle to prejudice us against the very valuable concept 
that there are certain fundamental quantities in the Universe 
which we can measure with our somewhat imperfect ideas of 
length, mass, and time. 
