Is there a nature of time?
I tend to find myself thinking about time once in a while. Although I just can’t wrap my head around the true nature of it, there’s simply no denying that time in particular has one of the most profound and felt effects of them all.
As time goes by we realize that there seems to be only one direction. In our retrospective view of events time moves from past to present to future, and never the other way around.
Then there’s physics and according to the underlying truth in numbers our Universe itself is timeless in a way that the same things will always occur regardless of what direction time is traveling in.
But wait, a new paper by physicists now suggest that gravity isn’t strong enough to force every object in the Universe into a forward-moving direction.
However, this gives rise to the question of how we can be sure that time exists to begin with? After all, if we follow this new scientific lead, time may only exist inside our heads.
That could literally be mind-blowing for mere humans, so let’s step back for a moment to revisit what we think to know about the so-called arrow of time.
British astronomer Arthur Eddington conclusively explained a hundred years ago that thanks to the forward-facing arrow of time, young becomes old and the past becomes the present, which once was the future. That’s why you can’t put your toothpaste back into the tube or unscramble your eggs. Once it’s done, it’s in the past.
But if we try to shift our focus to another perspective, onto a meta level, and look at the Universe as a whole, there are only the zeros and ones of physics governing any kind of behavior.
Almost all of these laws, apart from some tiny exceptions, are considered to be completely time-reversible and the same effects will occur, regardless of whether time is running forwards or backwards.
Even though Lee Billings has some pretty remarkable theories about the big bang not being thebeginning but the start of a universe in a past of a parallel one (yes, he actually said that), he also wrote in an article for the Scientific American, that:
“Whether through Newton’s gravitation, Maxwell’s electrodynamics, Einstein’s special and general relativity, or quantum mechanics, all the equations that best describe our Universe work perfectly if time flows forward or backward,”.
According to the force of gravity and as one of the main examples of a ‘time-reversible’ quality in our Universe – there’s the path of a planet orbiting a star. So whether time runs forwards or backwards doesn’t seem to matter, as planetary orbits follow the exact same paths with the only difference being the direction of the orbit itself.
After all, time might only be observable in a subjective way, right? That’s what Einstein’s special theory of relativity might be saying, wouldn’t it be for the little something called second law of thermodynamics.
A Disorder of Time
There’s something made clear to us in the second law of thermodynamics. As time moves forward, the entropy highlighting the amount of disorder in the Universe will increase as well.
The ingredients you mixed to cook your last meal can’t just be separated again. They are now something different, they are disordered and you can’t go back and lessen the amount of disorder. This, of course, always applies to any particular system.
In the absence of a better way to fix the concept of time, physicists have taken the second law as the source of time’s arrow, albeit reluctantly. An increasing disorder demands time moving in a certain direction and that’s the way it is… To settle for this argument causes a slight feeling of discomfort and inconvenience.
That’s actually one of the reasons why many physicists now suspect that when good old gravity forces enough tiny particles to interact with each other, the forward-facing time arrow emerges, increasing entropy along the way.
This would allow for a more directionless Universe only once these tiny particles start interacting with much larger things.
There needs to be a tweak to make it work, though. Entropy always must have increased, which once again needs the Universe to start off more ordered than it is now. This can’t be explained accurately and is derived from the idea that there are parallel universes where time runs in all directions.
Going back to the idea that gravity is the force behind all this craziness, tests need to be made and fortunate enough, a pair of physicists decided to put the theory to test.
The magic word decoherence
That moment when particle physics merge with classical mechanics is called decoherence. Basically it’s the point at which particles are thought to transition from being governed by the arrow of time to being governed by the directionless laws of the Universe.
The most prominent theory explaining decoherence is the Wheeler-DeWitt equation from 1965. This field equation is part of a theory attempting to mathematically combine the ideas of quantum mechanics and general relativity, taking another step toward a theory of quantum gravity.
But back to the pair of physicists – Dmitry Podolsky, from Harvard University, and Robert Lanza, head of Astellas Global Regenerative Medicine, finally ran their measurements of gravity through the Wheeler-DeWitt equation. What they calculated unexpectedly found that the math didn’t fit and hence, the equation does not explain how time’s forward-moving direction actually emerges. Furthermore, according to their results, gravity’s effects kick in too slowly and can’t account for an universal arrow of time.
In other words, the force is not strong enough with this one and can’t possibly be the factor that pulls particles into the same direction, time-wise.
Robert Lanza wrote on several occasions about the results, stating that
“Our paper shows that time doesn’t just exist ‘out there’ ticking away from past to future, but rather is an emergent property that depends on the observer’s ability to preserve information about experienced events,” [adding that] “In his papers on relativity, Einstein showed that time was relative to the observer […] Our paper takes this one step further, arguing that the observer actually creates it.”
Here we are now. After having problems accepting the fundamental laws that led us to the ‘ongoing mess’ time has created in our Universe, this paper now suggests that time’s arrow is purely subjective and determined by an observer with a certain type of neurological wiring.
The idea definitely is controversial and so it didn’t take long before Yasunori Nomura, a physicist at UC Berkeley, but not involved in the study, criticized the results for failing to include the fabric of space-time altogether. Instead the paper does introduce a quality ‘observer time’ into the equation… and who can really tell, if this one’s even real.
Anyway, we obviously need to look for an answer using mathematical definitions for the concept of time as such, without including us humans in the equation. But may be the results discovered by Lanza and Podolsky suggest just that – that we’re missing out on something totally different.
On thing’s for sure – time remains a mystery, but that can also be said about the fact that some kind ofmissing influence is pushing space apart in an accelerated expansion – it comes as no surprise that in a recent paper, a group of physicists found that in some cases, the proposed dark energy might cause time to go forward…
In the end, the arrow of time might be pushing us forward, but so does the imagination of the people in our attempt to understand what things cause… even if that means that time’s just a construct of our conscious minds.