What if the time part of the space- time continuum equation was literally running out? Perhaps evidence suggests that time is slowly disappearing from our universe, and will one day vanish completely (Or, is it Timeless?) --a radical theory may explain a cosmological mystery that has puzzled scientists for years.
Scientists previously have measured the light from distant exploding stars to show that the universe is expanding at an accelerating rate. They assumed that these supernovae are spreading apart faster as the universe ages. Physicists also assumed that a kind of anti-gravitational force must be driving the galaxies apart, and started to call this unidentified force "dark energy".
The idea that time itself could cease to be in billions of years - and everything will grind to a halt - was proposed in 2009 by Professor José Senovilla, Marc Mars and Raül Vera of the University of the Basque Country, Bilbao, and University of Salamanca, Spain. The corollary to this radical end to time itself is an alternative explanation for "dark energy" - the mysterious antigravitational force that has been suggested to explain a cosmic phenomenon that has baffled scientists.
However, to this day no one actually knows what dark energy is, or where it comes from. Professor Senovilla, and colleagues have proposed a mind-bending alternative. They propose that there is no such thing as dark energy at all, and we’re looking at things backwards. Senovilla proposes that we have been fooled into thinking the expansion of the universe is accelerating, when in reality, time itself is slowing down. At an everyday level, the change would not be perceptible. However, it would be obvious from cosmic scale measurements tracking the course of the universe over billions of years. The change would be infinitesimally slow from a human perspective, but in terms of the vast perspective of cosmology, the study of ancient light from suns that shone billions of years ago, it could easily be measured.
The team's proposal, published in the journal Physical Review D, dismisses dark energy as fiction. Instead, Senovilla says, the appearance of acceleration is caused by time itself gradually slowing down, like a clock with a run-down battery.
“We do not say that the expansion of the universe itself is an illusion," he explains. "What we say it may be an illusion is the acceleration of this expansion - that is, the possibility that the expansion is, and has been, increasing its rate."
If time gradually slows "but we naively kept using our equations to derive the changes of the expansion with respect of 'a standard flow of time', then the simple models that we have constructed in our paper show that an "effective accelerated rate of the expansion" takes place."
Currently, astronomers are able to discern the expansion speed of the universe using the so-called "red shift" technique. This technique relies on the understanding that stars moving away appear redder in color than ones moving towards us. Scientists look for supernovae of certain types that provide a sort of benchmark. However, the accuracy of these measurements depends on time remaining invariable throughout the universe. If time is slowing down, according to this new theory, our solitary time dimension is slowly turning into a new space dimension. Therefore the far-distant, ancient stars seen by cosmologists would from our perspective, look as though they were accelerating.
"Our calculations show that we would think that the expansion of the universe is accelerating," says Prof Senovilla. The theory bases its idea on one particular variant of superstring theory, in which our universe is confined to the surface of a membrane, or brane, floating in a higher-dimensional space, known as the "bulk". In billions of years, time would cease to be time altogether.
"Then everything will be frozen, like a snapshot of one instant, forever," Senovilla told New Scientist magazine. "Our planet will be long gone by then."
Though radical and in many way unprecedented, these ideas are not without support. Gary Gibbons, a cosmologist at Cambridge University, say the concept has merit. "We believe that time emerged during the Big Bang, and if time can emerge, it can also disappear - that's just the reverse effect."
In 2011, scientists at the Scientific Research Centre Bistra in Ptuj, Slovenia, theorized that the Newtonian idea of time as an absolute quantity that flows on its own, along with the idea that time is the fourth dimension of spacetime, are incorrect. They propose to replace these concepts of time with a view that corresponds more accurately to the physical world: time as a measure of the numerical order of change.
In two papers in Physics Essays, Amrit Sorli, Davide Fiscaletti, and Dusan Klinar, begins by explaining how we usually assume that time is an absolute physical quantity that plays the role of the independent variable (time, t, is often the x-axis on graphs that show the evolution of a physical system). But, as they note, we never really measure t. What we do measure is an object’s frequency and speed. But, by itself, t has only a mathematical value, and no primary physical existence.
This view doesn’t mean that time does not exist, but that time has more to do with space than with the idea of an absolute time. So while 4D spacetime is usually considered to consist of three dimensions of space and one dimension of time, the researchers’ view suggests that it’s more correct to imagine spacetime as four dimensions of space. In other words, as they say, the Universe is “timeless.”
“Minkowski space is not 3D + T, it is 4D,” the scientists write in their most recent paper. “The point of view which considers time to be a physical entity in which material changes occur is here replaced with a more convenient view of time being merely the numerical order of material change. This view corresponds better to the physical world and has more explanatory power in describing immediate physical phenomena: gravity, electrostatic interaction, information transfer by EPR experiment are physical phenomena carried directly by the space in which physical phenomena occur.”
“The idea of time being the fourth dimension of space did not bring much progress in physics and is in contradiction with the formalism of special relativity,” he said. “We are now developing a formalism of 3D quantum space based on Planck's work. It seems that the Universe is 3D from the macro to the micro level to the Planck volume, which per formalism is 3D. In this 3D space there is no ‘length contraction,’ there is no ‘time dilation.’ What really exists is that the velocity of material change is ‘relative’ in the Einstein sense.”
The researchers give an example of this concept of time by imagining a photon that is moving between two points in space. The distance between these two points is composed of Planck distances, each of which is the smallest distance that the photon can move. (The fundamental unit of this motion is Planck time.) When the photon moves a Planck distance, it is moving exclusively in space and not in absolute time, the researchers explain. The photon can be thought of as moving from point 1 to point 2, and its position at point 1 is “before” its position at point 2 in the sense that the number 1 comes before the number 2 in the numerical order. Numerical order is not equivalent to temporal order, i.e., the number 1 does not exist before the number 2 in time, only numerically.
Without using time as the fourth dimension of spacetime, the physical world can be described more accurately. As physicist Enrico Prati noted in a recent study, Hamiltonian dynamics (equations in classical mechanics) is robustly well-defined without the concept of absolute time.
Other scientists have pointed out that the mathematical model of spacetime does not correspond to physical reality, and propose that a timeless “state space” provides a more accurate framework. The scientists also investigated the falsifiability of the two notions of time.
The concept of time as the fourth dimension of space -- as a fundamental physical entity in which an experiment occurs -- can be falsified by an experiment in which time does not exist, according to the scientists.
An example of an experiment in which time is not present as a fundamental entity is the Coulomb experiment; mathematically, this experiment takes place only in space. On the other hand, in the concept of time as a numerical order of change taking place in space, space is the fundamental physical entity in which a given experiment occurs. Although this concept could be falsified by an experiment in which time (measured by clocks) is not the numerical order of material change, such an experiment is not yet known.
“Newton theory on absolute time is not falsifiable; you cannot prove it or disprove it -- you have to believe in it,” Sorli said. “The theory of time as the fourth dimension of space is falsifiable and in our last article we prove there are strong indications that it might be wrong. On the basis of experimental data, time is what we measure with clocks: with clocks we measure the numerical order of material change, i.e., motion in space.”
In addition to providing a more accurate description of the nature of physical reality, the concept of time as a numerical order of change can also resolve Zeno’s paradox of Achilles and the Tortoise. In this paradox, the faster Achilles gives the Tortoise a head start in the race. But although Achilles can run 10 times faster than the Tortoise, he can never surpass the Tortoise because, for every distance unit that Achilles runs, the Tortoise also runs 1/10 that distance. So whenever Achilles reaches a point where the Tortoise has been, the Tortoise has also moved slightly ahead. Although the conclusion that Achilles can never surpass the Tortoise is obviously false, there are many different proposed explanations for why the argument is flawed.
The paradox can be resolved by redefining velocity, so that the velocity of both runners is derived from the numerical order of their motion, rather than their displacement and direction in time. From this perspective, Achilles and the Tortoise move through space only, and Achilles can surpass Tortoise in space, though not in absolute time.
Some recent studies have challenged the theory that the brain represents time with an internal “clock” that emits neural ticks (the “pacemaker-accumulator” model) and suggest that the brain represents time in a spatially distributed way, by detecting the activation of different neural populations. Although we perceive events as occurring in the past, present, or future, these concepts may just be part of a psychological frame in which we experience material changes in space
A new theory of time by a trio of physicists in 2014, proposes that nearly all systems have a moment of “lowest complexity,” which they identify as a unique “past” from which two “futures” emerge. The trio is proposing a new direction for understanding the concept of time. In their paper published in the journal 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."
The image below shows the configuration of masses evolving under Newtonian gravity.
The proposal by the trio though phrased in a way as to suggest it's a solution to the arrow of time problem, it's more likely to be considered as yet another theory that works mathematically, yet still can't answer the basic question: what is time?
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)
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