History of the Time Mechine
The medical man's said, starting hard at a coal in the fire. If the time is really only a fourth dimension of space, why is it, and why has it always been, regarded as something different? And why can't we move in time as we move about in the other dimensions of space?
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The time traveller smiled, are you sure we can move freely in space? Right and left we can go, backward and forward freely enough, and men always have done so. I admit we move freely in two dimensions. But how about up and down? Gravitation limits is there.
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Not exactly, the medical man said, There are balloons.
But before the balloons, save for spasmodic jumping and the inequalities of the surface, man had no freedom of vertical movement. Still they could move a little up and down, the medical man said.