240 
The N.Z. Journal of Science and Technology. 
[Jan. 
a result which is arrived at by rather abstruse but cogent reasoning, and 
see where it leads. And the result I ask you to accept is that time, like 
length, depends upon our motion through the ether, and in a not very 
different way. An interval of time measured upon a body moving through 
the ether, as compared with one that is at rest with regard to it, is given 
by the relation 
where u is the velocity of the body through the ether and v is the velocity 
of light. This means several things ; and first it means that the duration 
of an event, the same event—the Grand National Steeplechase, for example 
—is lengthened out upon an earth fixed as regards the ether as compared 
with what it would be if run on an earth moving through the ether with 
considerable speed—considerable, that is to say, as compared with the 
velocity of light. Well, but that is just what the “ conspiracy in nature ” 
prevents us forming any opinion upon. We have tried to find out—we 
have tried hard to find out—and we have come up against a blank wall 
every time. And if we are up against a blank wall in deciding how quickly 
the earth moves through the ether, neither can we say that the Grand 
National was run in so-many seconds. To us it appears to have been so. 
To the observer upon the back of an electron whose speed with regard to 
the earth is about 120,000 miles a second the race would seem to have 
occupied only about eight-tenths of the time. And who is to say which is 
right ? We are certainly not riding upon the back of an electron, but as 
regards the ether the electron may be at rest, and the earth may be moving 
through the ether with this great speed. We cannot tell which is moving. 
We have no knowledge whether the earth is at rest with regard to the 
ether, or whether it is moving through it with a stupendous speed ; and so, 
while to us the interval is what the racing calendars say it is, to an observer 
upon another world it might be either greater or smaller, as the case may 
be. Thus time as well as length depend upon our speed relatively to this 
all-important and yet illusive medium. 
Looking at our equation again, we see that if we move through the 
ether with the velocity of light, so that u and v become the same, time 
disappears altogether, and also distances shrink up into nothingness. 
Thus, as Eddington has pointed out, “If a man wishes to achieve 
immortality and eternal youth, all he has to do is to cruise about space 
with the velocity of light. He will return to the earth, after what seems 
to him to be an instant of time, to find that many centuries have passed 
away.” How this comes about may perhaps be made a little more concrete 
and intelligible by pointing out that, to such a one, a man striking a match 
to light a pipe would always be doing just the same thing, and the pipe 
would never get lighted until he stopped, when he would find that he had 
smoked it several hundred years ago, and was himself, and had been for 
a similar time, dead and buried—a fact which, judging from his remarkable 
experiences, might not, after all, surprise him. 
This is one of the many paradoxes which one comes up against in this 
peculiar subject—paradoxes which are only paradoxes because, as yet, 
we are not at the end of out groping. 
I have said that time and space are both conditioned by the velocity 
we may assign to the earth’s motion through the ether, but they are so 
conditioned that whether we be moving through the ether or not, and 
with whatever velocity we may choose to imagine we are moving though 
