Quantum physics and time

From Wikipedia: Vlatko Vedral is a Serbian-born (and naturalised British citizen) physicist and Professor of Physics at the University of Oxford and CQT (Centre for Quantum Technologies) at the National University of Singapore and a Fellow of Wolfson College. He is known for his research on the theory of Entanglement and Quantum Information Theory. As of 2017 he has published over 280 research papers in quantum mechanics and quantum information and was awarded the Royal Society Wolfson Research Merit Award in 2007. He has held a Lectureship and Readership at Imperial College, a Professorship at Leeds and visiting professorships in Vienna, Singapore (NUS) and at Perimeter Institute in Canada. As of 2017, there were over 18,000 citations to Vlatko Vedral’s research papers. He is the author of several books, including Decoding Reality.

Watch this movie “Living in a quantum world” from Vlatko Vedral on YouTube: https://youtu.be/vaUfZak8Ug4. At the end of his presentation a question from the audience about time and quantum physics is asked (at about 1: 10) and in his answer he describes the behavior of a super-accurate clock and what happens to the last digits when you lift that clock half a meter in the gravitational field. And then he wonders what it means when you imagine that clock to be in a quantum superposition at the two different heights in the gravitational field. A superposition of two different timelines. Fascinating.

By the way, the first part of his presentation – about 45 minutes – is actually a very compact version of my quantum physics book. Everything is presented in an almost blazing speed: interference, the Mach-Zehnder interferometer, Schrödinger’s cat, the Copenhagen interpretation against the multiverse interpretation, delayed choice experiments, interference with very large molecules shot through double slits, the orientation of our robin on the earth’s magnetic field in its annual migration, the 100% efficiency of chlorophyll. Highly recommended.

Mass and energy, time and and space, the misconceptions

Quanta Magazine, a web service which often brings interesting articles, published shortly an interesting article where relativity, quantum physics and black holes played an important role. However, in reading it I did hit upon a very common misconception, about which I like to comment here.

Quote from: Einstein, Symmetry and the Future of Physics | Quanta Magazine

Solar energy arrives on Earth and becomes mass in the form of green leaves, creating food we can eat and use as fuel for thought.
Symmetry, the simplifying idea behind the great discoveries of physics ..

The misconception is that mass and energy are different things and that energy is somehow mysteriously converted into mass and vice versa. However, that’s not the message of E=mc2. Energy and mass are, in the opinion of almost all physicists, more like the two sides of the same coin. They are identical. This can be understood by considering what happens when an object is accelerated up to the speed of light.

According to the special relativity, all the energy that you spend into that acceleration is converted into inertial mass. It will cost you more and more energy to keep accelerating it. That is why we can never reach the speed of light itself in this way, the inertial mass would become infinite. This effect has been convincingly demonstrated when accelerating protons in the Large Hadron Collider at CERN. The faster they go, the more mass they get and the stronger the magnetic fields must be to keep them neatly in their circulair loop.

In general relativity, the central basic assumption is that inertial mass and heavy mass are identical or that the acceleration force due to gravity is identical to the acceleration force that you encounter in, for example, a merry-go-round. The implication therefore is that inertial mass, heavy mass and energy are really all the same fundamental thing. This means for instance that a charged battery must also be slightly heavier than when discharged. However, the energy released by nuclear fusion is often explained in popular terms as follows:

The mass of the two fused atomic nuclei is smaller than that of the original fused nuclei together. That mass deficit has become energy and that mass is gone.

Thus it seems as if mass alone is not conserved, mass plus energy should be the conserved property. However, Wikipedia says otherwise: “Mass and energy can be seen as two names (and two measurement units) for the same underlying, conserved physical quantity.[18] Thus, the laws of conservation of energy and conservation of (total) mass are equivalent and both hold true”.

Ponder this. The fused atomic nucleus has received an enormous amount of kinetic energy during the fusion, and that is speed. That kinetic energy is exactly having the same mass as the ‘disappeared’ mass. So, that mass has not disappeared at all. Due to the speed with which the fused core now moves, which means kinetic energy, it also has more mass. That is the message of special relativity. If you could have this fusion taking place in a thermally completely sealed box balanced on a pair of scales, you would find zero difference in weight – and therefore in mass.

Another but related topic. That every observer always observes the same speed of light is a physical observation but goes against our so-called common sense which tells us how adding up speeds normally works. Elsewhere on this website I say something about that in ‘What is light‘.