“When we are comfortably seated in the railway car,” his uncle replied, “without any effort on our part to go forward, how can we judge of our motion except by the position we occupy in relation to the objects that surround us? We are aware of the way we are going by the continual changing of the objects in sight, and not by any feeling of fatigue, since we do not move our legs. But the objects and people nearest to us and always before our eyes, our traveling companions and the furnishings of the car, remain for us in the same position. The left-hand neighbor is always at the left, the one in front is always in front. This apparent immobility of everything in the car makes us lose consciousness of our own movement; then we think ourselves immobile and fancy we see flying in an opposite direction exterior objects, which are always changing as we look at them. Let the train stop, and immediately trees and houses cease moving, because we no longer have a shifting point of view. A simple carriage drawn by horses, a boat borne along by the current, lend themselves to this same curious illusion. Every time we ourselves are gently moved along, we tend, more or less, to lose consciousness of this movement, and surrounding objects, in reality immobile, seem to us to move in a contrary direction.” “Without being able to explain it to myself well,” returned Emile, “I see that it is so. We move and we think we see the other things moving. The faster we go, the faster the other things seem to go.” “You hardly suspect, my little friends, that Emile’s naïve observation leads us straight to one of the truths that science has had the most trouble in getting accepted, not on account of its difficulty, but because of an illusion that has always deceived most people. “If men passed their whole life on a railroad, without ever getting out of the car, stopping, or changing speed, they would firmly believe trees and houses to be in motion. Except by profound reflection, of which not everybody is capable, how could it be otherwise, since none would have seen the testimony of their eyes contradicted by experience? Of those that have been convinced, one sharper than the others rises and says this: ‘You imagine that the mountains and houses move while you remain at rest. Well, it is just the opposite: we move and the mountains, houses, and trees stand still.’ Do you think many would agree with him? Why! they would laugh at him, for each one sees, with his own eyes, mountains running, houses traveling. I tell you, my children, they would laugh at him.” “But, Uncle—” began Claire. “There is no _but_. It has been done. They have done worse than laugh; they have become red with anger. You would have been the first to laugh, my girl.” “I should laugh at somebody asserting that the car moves and not the houses and mountains?” “Yes, for an error that accompanies us all through life and that every one shares, is not so easily removed from the mind.”