1922,] The Ninth Indian Science Congress. [8.C. 5 
explosive flashes is simply a matter of observation. By suit- 
able apparatus one might go on refining the limits of possible 
error, reducing them we will say to from 1/10 second to 1/100 
or even 1/1000 of a second, and so we could say the simul- 
taneity was precise to within that limit of error. But this is a 
taneity, had cut the knot of the trouble by framing an artifi- 
cial simultaneity, making it dependent on the speed of light. 
The next point I will refer to is a statement repeatedly 
met with in Einstein’s exposition of his theories, to the effect 
that, in any system in movement with regard to another, a 
clock will lose time or go permanently slower from the point 
of view of the observer outside that moving system. The 
v . 
ratio = still comes into the argument, for the unit second has 
to be represented by the expression 
1 
Brooklands carrying a good chronometer, or the rim of a 
flywheel with a watch packed away inside it, ought in that 
case to record any such cumulative difference, if the experi- 
does not happen in fact. 
But it is what Einstein nevertheless says does happen, as 
the following references will show. At page 37 he writes :— 
‘*as a consequence of its motion the clock goes more slowly 
than when at rest,” : 
(not, be it understood, lags behind, but loses time conti- 
nuously and therefore cumulatively). : 
Again, with reference to a rotating disc, at page 81 :— 
‘‘as judged from this body [the stationary system K], the 
slock at the centre of the disc has no velocity, whereas the 
clock at the edge of the disc is in motion relative to K in conse- 
