The Physics of Time: Why does it flow?
Richard Muller, Prof. Physics UC Berkeley emeritus, author: Now—the Physics of Time.
Abstract: We know much about time, about its variability with velocity and gravity. Einstein took time to be the fourth dimension. But time is different. We can stand still in space (given any coordinate system) but not in time. Why? What is the meaning of “now”—that ephemeral concept whose meaning changes every moment? I don’t know where you are, but I do know something about you: you are reading the word “now” right now! I will present a new theory for the flow of time, one that links it to the creation of new space through the expansion of the Universe. The old postulated connection between entropy and the arrow of time will be discredited as an untestable theory—or, more precisely, as a theory that has failed multiple tests. Remarkably, the new theory I will present is testable. Events that create new space, such as the collision of two black holes that led to the observation of gravitational waves, create new space at the site of the collision, and according to the theory, they should create a potentially observable level of new time.
Towards Integrated Optical Time Standards and Frequency Synthesizers
Kerry Vahala (Ted and Ginger Jenkins Professor of Information Science and Technology and Professor of Applied Physics, CalTech)
Abstract: Communication systems leverage the respective strengths of optics and electronics to convey high-bandwidth signals over great distances. These systems were enabled by a revolution in low-optical-loss dielectric fiber, complex integrated circuits as well as devices that link together the optical and electrical worlds. Today, another revolution is leveraging the advantages of optics and electronics in new ways. At its center is the laser frequency comb which provides a coherent link between these two worlds. Significantly, because the link is also bidirectional, performance attributes previously unique to electronics and optics can be shared. The end result has been transformative for time keeping, frequency metrology, precision spectroscopy, microwave-generation, ranging and other technologies. Even more recently, low-optical-loss dielectrics, now in the form of high-Q optical resonators, are enabling the miniaturization of frequency combs. These new `microcombs’ can be integrated with electronics and other optical components to potentially create systems on-a-chip. I will briefly overview the history and elements of frequency combs as well as the physics of the new microcombs. Efforts underway to develop integrated optical clocks and integrated optical frequency synthesizers using the microcomb element are also described.
Professor Vahala studies the physics and applications of high-Q optical microcavities. His research group has pioneered resonators that hold the record for highest optical Q on a semiconductor chip and has also launched many of the research topics in the field of optical microcavities. Applications currently under study include micro-gyros with Earth-rotation-rate sensitivity and soliton micro-combs. Vahala was involved in the early effort to develop quantum-well lasers for optical communications and he received the IEEE Sarnoff Medal for his research on quantum-well laser dynamics. He has also received an Alexander von Humboldt Award for work on ultra-high-Q optical microcavities and is a fellow of the IEEE, the IEEE Photonics Society and the Optical Society of America. Vahala is the Jenkins Professor of Information Science and Technology and Professor of Applied Physics and received his B.S., M.S., and Ph.D. degrees from Caltech. He currently serves as the Executive Officer of the Department of Applied Physics and Materials Science and holds over 30 patents in photonics.
Encapsulated MEMS: What’s Good for the Resonator is Good for the Sensor
Tom Kenny (Associate Dean, Professor of Mechanical Engineering, Stanford University)
Abstract: Since the demonstration of the Resonant Gate Transistor by Harvey Nathason and his team more than 50 years ago, we’ve all been interested in the potential application of MicroElectroMechanical Systems (MEMS) for timing applications. Of course, there were obstacles, with the biggest associated with the frequency stability of MEMS resonators. After significant effort, we found that stability in MEMS resonators could be improved by ultra-clean high-temperature encapsulation processes. Today, oscillators based on MEMS resonators are providing stability competitive with the best quartz-based oscillators, with improved size, power, weight, reliability, and cost.
Since the earliest demonstration of MEMS inertial sensors for automotive applications more than 30 years ago, we’ve all be interested in the potential application of these devices for inertial navigation applications. Of course, there were obstacles, with the biggest associated with the stability of MEMS sensors. There has been extensive effort on development of materials, operational schemes and other approaches to overcome stability issues. Our group has been exploring one central question : can we build inertial sensors in an encapsulation process similar to that used for the highest-stability MEMS resonators, and is this a path towards ultra-stable inertial MEMS sensors?