*Physical Review Letters*, Julian Barbour, of College Farm in the U.K., Tim Koslowski of the University of New Brunswick in Canada and Flavio Mercati of the Perimeter Institute for Theoretical Physics also in Canada, describe their new ideas beginning with the suggestion that initial conditions don't necessarily need to be imposed on time-symmetric law when attempting to describe solutions to behaviors that define an "arrow of time."

For all the advances made in understanding the world around us, there are still two very basic fundamental concepts that have defied explanation: time and gravity. Though we have progressed greatly in measuring both and using both to understand other concepts, we still today are no closer to understanding either than we were when we first conceptualized them. Such an acknowledgment suggests that we likely have a major flaw in our understanding of the universe. In considering such a possibility, the three physicists with this new effort suggest we might look at time in a completely new way—by dividing a dynamically closed universe (ala the Newtonian N-body problem) into two halves with shape complexity growing from a single point—each solution to the problem can then be considered as having one past but two distinctly futures. In such a scenario, an observer would of necessity have to exist on one side or the other, and thus would only ever have that perspective. Critical to this idea is that the all of the energy and angular momentum in such a system would have to be zero.

In essence, the team has removed time from mathematical functions that describe the energy of the universe—that's what allows for splitting the equations that have been created to describe the evolution of the universe into two parts, with both having initial low complexity moving to higher complexity (similar in some respects to theories of time based on entropy).

The proposal by the trio though phrased in a way as to suggest it's a solution to the arrow of time problem, is not likely to be addressed as such by the physics community—it's more likely to be considered as yet another theory that works mathematically, yet still can't answer the basic question of what is time.

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**More information:**
Identification of a Gravitational Arrow of Time, *Phys. Rev. Lett*. 113, 181101 – Published 29 October 2014 http://dx.doi.org/10.1103/PhysRevLett.113.181101 (free PDF)

**ABSTRACT**

It is widely believed that special initial conditions must be imposed on any time-symmetric law if its solutions are to exhibit behavior of any kind that defines an "arrow of time." We show that this is not so. The simplest nontrivial time-symmetric law that can be used to model a dynamically closed universe is the Newtonian N-body problem with vanishing total energy and angular momentum. Because of special properties of this system (likely to be shared by any law of the Universe), its typical solutions all divide at a uniquely defined point into two halves. In each, a well-defined measure of shape complexity fluctuates but grows irreversibly between rising bounds from that point. Structures that store dynamical information are created as the complexity grows and act as "records." Each solution can be viewed as having a single past and two distinct futures emerging from it. Any internal observer must be in one half of the solution and will only be aware of the records of one branch and deduce a unique past and future direction from inspection of the available records.

## justindadswell

https://answers.y...8AA6lL6n

Under J, from 5 years ago.

Multi-verse, mirror universe, 2D, 1D, and nothing. All of it is true. All of it touches.

The fact that 5 years ago this type of thought was plain stupid and today it's given real consideration - well let's just say it's a good feeling. I personally think this is the right direction.

## MrVibrating

Much like those propositions that "time is the metric of rate of change"; the proponents don't seem to grasp that the problem is merely restated by their putative 'solution' - it's still dependent upon a more fundamental time-like dimension that preceding states evolve into. What is this substrate these ever-branching bifurcations are spread upon?

Precisely...

## ichisan

Barbour, Koslowski and Mercati are setting themselves up to be the three stooges of physics.

## AmritSorli

## AmritSorli

"Physical Review Letters"

Dear Editors

recent article on time "Identification of Gravitational arrow of Time"

http://phys.org/n...row.html

published in your journal has wrong conclusions because time we

measure with clocks has only a mathematical existence. In the universe

there is no such a thing as "arrow of time" which exists only as a

mathematical direction of numerical order of change which run in

quantum vacuum, see our paper published in

FOOP http://link.sprin...4-9840-y

More than that: gravity is immediate, that's why in Newton formalism

for gravity there is no symbol t and in GR time t is only a parameter

of stress-energy tensor.

From this point of view relating time with gravity is pure mistake.

Yours Sincerely Amrit Srecko Sorli, Foundations of Physics Institute www.fopi.info

## Uncle Ira

Dear Skippy,

don't forget to leave your silly looking pointy cap at the door so the next couyon doesn't have to do without his hard earned privilege of wearing one.

And P.S. for you Ami-Skippy. You don't need to seen us anymore letters telling us the conclusions are wrong no. We use professional scientist-Skippys to check that and don't need any help from the amateurs no. And don't forget about the silly looking pointy cap.

## RealAlaskanMan

Remember though that Einsteins law E=MC2 in that time is always relative to the observer hence the appearance of the arrow of time where time for one observer moves faster and the other it moves slower. This means that if I am on the rocket ship watching you on the Earth I will see your time passing quickly and you will see my time passing slowly; if in fact we are in a position to observe each others time. (see part 2)

## RealAlaskanMan

The equation of "Time" or how time is measure is done in respect to the speed of light. In that speed of light is the universal constant; we measure our speed through space as it appears to the observer. Move faster through space ie catch up with light and the result is less time, conversely move slower than your present speed say by coming to close to a black hole and your observed "Time" will accelerate.

Thus "Time" can be considered as a body's motion through space in respect to the speed of light.

## tadchem

Entropy cannot decrease with time - it can only increase.

Computer simulations are Cartesian (deterministic) systems, and have zero entropy.

The Second Law of Thermodynamics does not apply to closed, deterministic systems.

The 'researchers' are using the wrong tools.

## michaelboyd

## michaelboyd

[1]EINSTEIN, A. Zur Elektrodynamik bewegter Korper. Annalen der Physik 17: 891-921, 1905.

[2]EINSTEIN, A.; GROSSMANN, M. Entwurf einer verallgemeinerten Relativitatstheorie und einer Theorie der Gravitation. Zeitschrift fur Mathematik und Physik 62: 225-261, 1913.

[3]EINSTEIN, A. Die Grundlage der allgemeinen Relativitatstheorie. Annalen der Physik, 49, 1916.

[4] HILBERT, D., Die Grundlagen der Physik. Mathematische Annalen, 92, 1924.

## Da Schneib

This is incorrect. Laser experiments have verified that over a small enough number of particles, and a short enough time, the particles can be made to behave so as to decrease their entropy. See also Bose-Einstein Condensates. The 2LOT does not apply to quantum systems. See also the Fluctuation Theorem.

Non sequitur. Prove they have zero entropy. That they are deterministic makes no difference; so is classical mechanics, which has non-zero entropy.

## Da Schneib

## Da Schneib

This hasn't been done in the lab, but we've checked it by observation both in our galaxy and in other galaxies. In fact, we've done it very precisely by observing Jupiter, and the results are that if it's not the same speed of light, it's very close. The first such measurement was made a decade ago: http://www.nrao.e...gravity/

## AstroDwarf

Entropy can also decrease locally....

## krydan2167

Mechanical time is often confused with actual time among celebrity scientist: Einsteins general relativity applies to mechanical time: not being able to measure a particles position, or relative to the observer says nothing about actual time. Perception of time or mechanical clocks may be relative. but "Time itself" the thing that keep everything from happening at once is not relative!

## Da Schneib

## joe martins

## tritace

Nov 04, 2014## Da Schneib

See "Michelson-Morley Experiment."

## tritace

Nov 04, 2014## Captain Stumpy

continuing to post about aw/daw is simply promoting pseudoscience and trying to con decent people who might be scientifically illiterate into believing a falsified and debunked conjecture

and you, apparently, have missed out on hundreds of experiments which falsified and debunked your faith/religion/debunked pseudoscience

http://arxiv.org/...1284.pdf

given your complete inability to provide ANY reputable science supporting your conjecture or even supporting the possibility of feasibility of your conjecture, you should consider seeking medical/psychiatric attention

troll elsewhere

## tritace

Nov 04, 2014## PhysicsPolice

## TimLong2001

## TimLong2001

## holographic_singularity

## techieatwork

https://www.faceb...?fref=nf

## Da Schneib

## ryggesogn2

What is it?

The paper reminds me of a theory in the book "Stalking the Wild Pendulum".

## outside

I think there are a lot questions without answer, we do not have a complete definition of time, every time I ask what it is your definition of time on your theory people do not have to answer.