Living on Two Levels: Special Relativity and the Buddhist Doctrine of Two Truths

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The Train and the Tunnel

One of the postulates of Special Relativity is the following: the laws of physics are the same in all non-accelerating frames of reference. If I’m driving a train at a constant velocity of 30km/h towards a tunnel — the laws of physics are the same from both the perspective of the train at rest, and the tunnel at rest. From the perspective of the train— it’s perfectly valid to say that the tunnel is moving towards it at a speed of 30km/h, while the train remains stationary. Similarly, taking the tunnel’s perspective, we can say the train is what’s moving. These are both valid viewpoints, and almost trivial things to consider.

The situation because non-trivial once we consider relativistic speeds — velocities that approach the speed of light (3,000,000,000 m/s).

Suppose the following:

The tunnel is fit exactly for the train — both ends can be inside at the same time

The tunnel has metal doors that open and close on either end

There is an observer on a hilltop nearby

Relativistic speeds are now involved — and we have 3 perspectives to consider. The…