Goddard Space Flight Center, Greenbelt, Maryland 20771


Monday, March 21, 2011 / 3:30 PM, Building 3 Auditorium

John Ashmead

"Temporal Paradoxes"

ABSTRACT -- Einstein's general relativity is the leading theory of gravity. Simple and elegant, it has passed all available experimental tests including: deflection of light by gravity, precession of orbital apsides, gravitational time dilation (used in GPS), and frame-dragging.

However, general relativity makes a number of counter-intuitive predictions. In particular, trajectories looping around massive, rapidly rotating stars or passing through a wormhole can close on themselves in time, creating closed timelike curves (CTCs).

This creates the possibility of "grandfather" and "bootstrap" paradoxes. Recent work by Greenberger & Svozil, and others, however, questions this conclusion. That work suggests that when quantum mechanical effects are included, the paradoxes become self-canceling, eliminated by destructive interference within the wave function. If the paradoxes are self-canceling, then closed time-like curves are possible. If they are possible, can we create or detect them?

Several authors have suggested that we look for evanescent wormholes with the Large Hadron Collider. If we find them, we may be at the edge of temporal paradox. While the only safe prediction in this area is that there are no safe predictions, we look at the implications of this for general relativity, quantum mechanics, & causality.

SPEAKER -- John Ashmead summarizes his career to date this way:

I have a BA in physics from Harvard, summa cum laude and a masters in physics from Princeton. I've just finished a clean cut on a physics dissertation, Quantum Time, on how to quantize time using the same rules as we use for space. Curiously enough, this line of attack doesn't appear to have been tried before. I use path integrals but add paths that vary in time to the usual paths varying in space. Doesn't seem to break anything & is testable so I am hoping to persuade some experimentalists to have a go.

I presented a poster on the dissertation at the Third International Conference on the Nature and Ontology of Spacetime last year, and I recently did a short talk on the dissertation at the 4th Feynman Festival in Olomouc. I'm planning a followup paper on experimental tests of quantum time, hopefully for delivery at the 5th Feynman Festival.

Next Week: "Critter Cam", Greg Marshall, National Geographic Society
Engineering Colloquium home page: https://ecolloq.gsfc.nasa.gov