Artículos con la etiqueta ‘física relativista’

Fundamental Quantum Optics Experiments Conceivable With Satellites Reaching Relativistic Distances And Velocities

Por • 27 jun, 2012 • Category: Leyes

One of the great puzzles of modern science is that the laws that govern the universe on the largest scale are entirely different from the ones that govern on the smallest scale. That’s odd because all our intuition about the universe is that it ought to be internally consistent rather than at odds with itself. This is why physicists are inextricably wedded to the idea that relativity and quantum mechanics must be manifestations of a bigger and better idea that encompasses them both. The differences between general relativity and quantum mechanics are so great that every attempt to reconcile them has so far failed. However, these attempts have been entirely theoretical and that gives them limited utility.For example, physicists routinely measure the quantum phenomenon of entanglement by sending entangled pairs of photons from one location to another. In these experiments, the sender and receiver must both measure the polarisation of the photons, whether vertical or horizontal, for example. But that can only happen if both parties know which direction is up. That’s easy to specify when they are close together. But it becomes much harder if they are separated by distances over which the curvature of spacetime comes into play. The problem here is that the answer is ambiguous and depends on the path that each photon takes through spacetime. The experimenters can work this out by tracing the path of each photon back to their common source, if this is known. But then, how does each photon ‘know’ the path that the other has taken? Theorists can only guess. Another problem arises when these kinds of experiments are done with the sender and receiver travelling at relativistic speeds. This introduces the well known problem of determining the order of events, which Einstein famously showed depends on the observers’ points of view. That’s in stark contrast to the prediction of quantum mechanics. Here the measurement of one entangled photon instantly determines the result of a future measurement on the other, regardless of the distance between them. If special relativity ensures that the order of events is ambiguous, what gives? Once again, theorists are at a loss. Of course, the way to answer these questions is to test them and see.

On the Lorentzian route to Relativity

Por • 28 jul, 2011 • Category: Leyes

We discuss pedagogical problems associated with the conventional approach in teaching relativity and the potential value of “Lorentzian route to relativity” for addressing these pedagogical problems. We think that Lorentzian approach may be valuable part of an introduction to relativity but the historical route should be followed up to its end. It must namely include Einstein’s application of Occam’s razor in reinterpreting Lorentz transformations kinematically and the discussion of the central role of the evolution from Lorentz’s “local time” to relativity of simultaneity. We discuss also what Occam’s razor is not and why it should not cut “too deeply or too permanently”.