I have seen roger Penrose video https://www.youtube.com/watch?v=sM47acQ7pEQ. In it explains that time origins are related to the rise of mass in the early universe. In the video it relates mass from Enstein E=MC^2 to planks equation E= HF (F stands for frequency). As there was no mass in the very early universe time did not exist. So time is a consequence of the rise of energy=MASS=Frequency.

However although particles would have no mass at rest their (kinetic) momentum must have provided mass (as it happens to the photon) in the very hot early universe (prior to the highs effect) thus time must have existed as well prior and must have risen with the development of zero mass at rest particles having momentum.

When looking at very short lived particles or virtual particles as per quantum mechanical uncertainty, any object or process that exists for a limited time or in a limited volume cannot have a precisely defined energy or momentum. So a certain volume of space is necesary for particles to become real via their momentum, prior to this, time does not exist as there is no certainty about momentum or energy within the smaller than required space (smaller than that of the wavelenght of the particle).

Could you please let me know if the reasoning is correct

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    $\begingroup$ "As there was no mass in the very early universe time did not exist." I've read Penrose's book on CCC and, in the book, he does not claim that time didn't exist in the early universe; he claims that no clocks existed, i.e., there's no way to 'build a clock' from massless entities. But time must exist since it is a dimension in spacetime. $\endgroup$ – Alfred Centauri Feb 8 '15 at 3:39
  • $\begingroup$ From a paper on CCC: "With such conformal invariance holding in the very early universe, the universe has no way of “building a clock”. So it loses track of the scaling which determines the full space-time metric, while retaining its conformal geometry." accelconf.web.cern.ch/accelconf/e06/PAPERS/THESPA01.PDF $\endgroup$ – Alfred Centauri Feb 8 '15 at 3:44
  • $\begingroup$ thanks for your answer. Space seems to exist prior to any clock being build as space dimensión or property of time is provided by particles with positive mass at rest. (mass=Clock) not by momentu energy particles such us photons. $\endgroup$ – Barnaby Feb 8 '15 at 12:08

As there was no mass in the very early universe time did not exist.

The notion of "very early" requires the existence of time; without the existence of time, what meaning does the phrase "very early" have?

Of course, time existed in the very early universe if that phrase is to have any meaning. Put circularly, there has never been a time in which time did not exist.

As I understand Penrose's argument, if all particles are massless then there is nothing with which to 'build a clock'; nothing with which to measure time.

However, in that case, there are no rulers either.

If it is the case that no mass implies time does not exist, then it must also be the case that no mass implies space does not exist.

But this is absurd.


Penrose's Conformal Cyclic Cosmology has absolutely no experimental or observational evidence. In fact he and his coauthor claimed there was some evidence in the CMB and it was disproven by 3 other independent analysis. Penrose's is a great mathematical physicist, but is prone to these kinds of speculations. His conformal model simply sets the conformal scale at conformal infinity to be matched to the zero scale at the Big Bang, really not a big deal since there is only the scale factor involved. The rest is speculation.

As for time when there is no mass, photons have energy, and that defines frequencies, and thus time. They also travel in spacetime, which still must exist to have general or special covariance. Time does not need mass. @Alfred Centauri is right.

Even in the early universe with only radiation the radiation's temperature decreased over time (the cosmological time defined by the Robertson Walker metric), and the models for that match the theory. Yes, I know, that was during inflation (and then after till matter dominance) with no mass, which was due to an Inflaton (or some other such theory), took some time. If it had not been that the universe would not be homogeneous nor would we see the kind of CMB we see.

Fact is, we don't know what could possibly mean there is no time.

  • $\begingroup$ a parallel comment :In a quantum mechanical soup at the beginning of the universe the four vectors of zero mass particles added would generate an invariant mass, locally, no? $\endgroup$ – anna v Jan 29 '17 at 7:09
  • $\begingroup$ That invariant mass is the rest mass, which is zero. Or did I misunderstand your question? $\endgroup$ – Bob Bee Jan 29 '17 at 9:04
  • $\begingroup$ It is zero for individual particles , but by more than one, the fourvectors will not in general be collinear and so an invariant mass for the sum appears. Similar to the quark gluon soup within the bag of the photon which make up most of the mass. $\endgroup$ – anna v Jan 29 '17 at 9:16

As there was no mass in the very early universe time did not exist.

It is strongly probable that this statement is true. As Alfred Centauri points out citing Penrose in his comment, without mass there would be no clock. But when he concludes that in spite of this fact time must exist because time is a dimension of spacetimes he forgets to ask the essential question: "in whose spacetime?"

Spacetime is relative, that means each mass particle has its own Minkowski diagram. There is no absolute spacetime. If there is no mass particle, there can be no Minkowski diagram.

There may be only one doubt: We could imagine that besides mass particles there are other phenomena in the (early) universe having a clock. In this case time could have existed without mass particles. But we have no knowledge about time without mass. By consequence, it is strongly probable that the a.m. statement is true.

However although particles would have no mass at rest their (kinetic) momentum must have provided mass (as it happens to the photon)

Photons have momentum energy but no mass. They have no meaningful spacetime diagram because their proper time is zero. They cannot have any clock, for photons all time is reduced to zero.

So time is a consequence of the rise of energy=MASS=Frequency.

As photons are showing, not every type of energy is providing time, but only mass energy. I do not know how exactly mass is providing time, but its frequency may play a role within this mechanism.

  • $\begingroup$ In a universe without clocks (mass is the clock as per the reference in the comment of -Alfred Centauri-) frequency in plank´s equation is in reference to vacum which is as per the equation treated having the properties of a particle (so for him vacum has the same properties tan that of a particle, spin, momentum etc) I am unsure vacum can be treated as such becasuse virtual particles as per the last paragraph of my question $\endgroup$ – Barnaby Feb 8 '15 at 11:46
  • $\begingroup$ If energ of momentum does not create time in photons. I guess implies that only real particles mass=energy momentum equates to a clock. $\endgroup$ – Barnaby Feb 8 '15 at 11:59
  • $\begingroup$ I would distinguish. If there is a movement of less than light speed c there should be time. Mass particles are moving at less than light speed. If virtual particles do so, they should have a clock. $\endgroup$ – Moonraker Feb 8 '15 at 12:06
  • $\begingroup$ There is time regardless - the massless particles have light-like world lines in spacetime. $\endgroup$ – Alfred Centauri Feb 8 '15 at 15:25
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    $\begingroup$ You did not ask me that question. Regardless, events are invariant, not relative. Interval is invariant, not relative. The geodesics of the spacetime are either time-like, light-like, or space-like, not relatively time-like, relatively light-like, or relatively space-like. $\endgroup$ – Alfred Centauri Feb 8 '15 at 19:04

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