A term coined in 1927 by the British astronomer Arthur Eddington to describe the "one-way direction" or "asymmetry" of time.

For most people, the notion that time passes only in one direction is a given. There are multiple reasons for taking this point of view : cause and effect, ageing etc etc. And on the cosmic scale, extensive and varied measurements have shown that the apparently expanding universe will irrevocably progress in the direction of more disorder. (Therefore, for Big Bang Theoristsplugin-autotooltip__plain plugin-autotooltip_bigBig Bang theory

There is now a large body of evidence (from different sources) to support the Big Bang Theory for the origin of the universe, but the problem remains as to the origin of the material or energy which initialised it.

As the UK’s Astronomer Royal Martin Rees has put it :, imagining backwards in time, the universe was previously more ordered)

But at the atomic and subatomic scale, quantum theory insists that particles can ‘travel’ either forwards or backwards in time with equal probability.

And further, Albert Einstein’s theories of relativity, incorporating Time as another dimension, insist that there is no single and special present - all moments are equally real.

Quote from New Scientist Nov. 1997

The past is gone, remembered perhaps, but unalterable. The future has yet to come into being, and is still open. Only the present moment is truly real. All this seems like common sense. Yet many scientists and philosophers are adamant that we have got it all wrong. They insist that time does not flow at all. "

More reference :Wikipedia

One often overlooked factor is that disorder is (usually) more likely than order. If you drop a large handful of coins, the chance that they will all fall heads up ('ordered') is exactly the same as for any other possible combination. But they probably won't - simply because there are far more 'disordered' possibilities.

Also see : 'Physicists can’t agree on whether the flow of future to past is real or a mental construct' an Atlantic Magazine article July 2016, about the Time in Cosmology conference at the Perimeter Institute for Theoretical Physics in Waterloo, Canada.

Note : Although the effects of gravity can make the universe more ordered, cosmological theory currently insists that in the very very very long term, all matter will eventually evaporate and disintegrate - eventually ending up with all atomic particles having degraded into photons. At which point, according to Prof. Roger Penrose, 3-D space and Time itself will no longer exist ”[…] the universe has no way of 'building a clock' “ See : Conformal cyclic cosmologyplugin-autotooltip__plain plugin-autotooltip_bigConformal cyclic cosmology

unknowable

Conformal Cyclic Cosmology (CCC) is a concept proposed in 2006 by the Nobel Prize winning cosmologist Professor Roger Penrose. It attempts to resolve a paradox associated with (standard) Big Bang theory.

"The issue arises from one of the most fundamental principles of physics: the

Also see :Time travelplugin-autotooltip__plain plugin-autotooltip_bigTime travel

The possibility of being able to travel either forwards or backwards in time has been discussed by philosophers, thinkers and writers for centuries.

More recently, discussions have also featured in the physics community - especially since Albert Einstein's discovery and description of 4-dimensional spacetime.

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