# What does it mean to “convert energy into time”?

In a recent article about creating electron-positron pairs by colliding photons in a laboratory, Andrei Seryi, director of the John Adams Institute at Oxford University, was quoted to said:

It's breathtaking to think that things we thought are not connected, can in fact be converted to each other: matter and energy, particles and light. Would we be able in the future to convert energy into time and vice versa?

Let's ignore for the moment that a physicist is amazed that $\gamma\gamma\rightarrow e^-e^+$ process is possible in a laboratory. But what does he mean by converting energy into time? Is this just a poetic sentence to emphasize his amazement, or is there some deeper meaning behind it?

Only thing that comes up in my mind is that, because our currently best theory of gravity - general relativity - is describing the dynamics of spacetime, "creating time" might mean inducing some change in the metric tensor $g_{\mu\nu}$, so he might be talking about the prospect of converting ordinary Standard Model particles into gravitational waves and vice versa.

However, he might be talking about something else. Am I missing something here?

• sounds to me as science fiction – anna v May 20 '14 at 18:33
• It would be best to ask Mr. Seryi, otherwise we just speculate what he might have had in mind. To me it seems like a rhetorical question that should not be taken literally. He just emphasized that nature can hold a lot of unexpected things (like matter converted into light) and there can be other secrets of physics that today could seem nonsensical. But it does not have to necessarilly be "converting energy into time". That to me seems merely like a figure of speech. But I am only speculating. – mpv May 20 '14 at 19:36
• Quite possibly slips between what the scientist intended to say, what was actually said, what was heard by the journalist, what the journalist thought was said, what the journalist expressed that as, in the article and what the editor thought it should be written as. – Siva Sep 27 '14 at 16:46

You're quoting from a piece of journalism as opposed to a paper, and different standards apply; one should then be prepared to understand what is said with that in mind.

It's breathtaking to think that things we thought are not connected, can in fact be converted to each other: matter and energy, particles and light.

The key word in this statement is breathtaking, he is expressing amazement; in a historical framework, things that were once thought (say in Newton's time) to be entirely separate have been shown to be connected.

Would we be able in the future to convert energy into time and vice versa?

The key word here is future; now he speculates whether in the future, further connections that now seem impossible may be shown to be possible. He isn't offering a theory of how this may come about. It's worth noting though that the connection of time & energy isn't entirely arbitrary, as if I recall correctly it is the time translational symmetry, by Noether's Theorem, that gives the conservation of energy.

It's also worth noting that the utopian end-point of this direction of thought is a species of monism.

Let's ignore for the moment that a physicist is amazed that γγ→e−e+

Well, we should be amazed about that it is possible, with regard to the question about time. Indeed,in this interaction process, look-up the standard Feynman diagram for instance, one of the initial photon is actually coming from the future.

The reason we observe "photons" in our detectors today, that is light energy (taken from the field and therefore not conserving the energy in the field) is because the underlying process of interaction between the field and matter is irreversible. Photons are, if you want, Nambu-Goldstone boson for the spontaneous time-reversal symmetry breaking (see 2008 Nobel Prize in Physics).

Maxwell's equations are time-reversal symmetric equations. When it couples to matter through an interaction that breaks this symmetry, energy from the field is localized into an atom for instance. Example: a discrete atomic energy level coupled to a continuum, has a highly irreversible time evolution, e.g spontaneous emission. Whereas, for Rabi oscillations, the exchange between the field and the atom preserves the time symmetry, no energy is localized in the atom (it actually oscillates) as long as coherence is preserved. In more technical term, one can say that energy is extracted from the field when the vacuum state of the field is not conserved by the interaction.

One can say that we observe light energy because the time-reversal symmetry is broken which implies an arrow of time, time evolution or simply as synonym, time. The ability to convert back this localized energy to repair the broken time-symmetry would be interesting..