It has been asked frequently -- how come only the past is present in our memories and not the future? Why time travel is not an actuality and the process of aging is irreversible? Why is entropy a definitive constant? What came before the Big Bang? Was time existent before the Big Bang? These are the Questions you should be asking your Prof.! But..
The answers to these complex questions can be potentially traced to the moment of the Big Bang. Sean Carroll, theoretical physicist of California Institute of Technology whose research focuses on theoretical physics, astrophysics and issues in cosmology, gravitation and field theory addresses this question below.
Time definitively infuses our lives for it is constantly measured. It’s tracked, put to use, machines employ time and others are built to keep track of its passage and measure it just as a ruler measures distances. There is a stark difference between the ruler and the clock-- time doesn’t necessarily employ distances but it does take use of direction pointing past from future.
Sean Carroll’s book, “From Eternity to Here,” analyzes the arrow of time that is observed in the space surrounding us. In the early stages, the universe was hot and dense, but what is observed now is a drastic change-- it is now cool, empty, and expanding rapidly. This particular difference is observed in all of nature--melted ice cubes to the evolution of different species-- time moves forward and cannot be reversed.
Despite the perception of this “arrow” being easy and obvious, the understanding of its innerworkings does not come with ease.
An explanation that most physicists appeal to is the presence of entropy that according to the Second Law of Thermodynamics tends to increase and constantly move forward and increase. This poses a question: why was entropy ever small to begin with? Many physicists such as Stephen Hawking, Ludwig Boltzmann, Roger Penrose, Richard Feynman, Alan Guth and many others all the way back to the time of Lucretius in ancient Rome have tackled this question and despite all of this, the answer to this question remains enigmatic and unknown.
To fully understand entropy and why it was small to begin with, the origin of the universe is to be understood first. The book “From Eternity to Here” also addresses this question and also how entropy is relative to black holes, cosmology, information theory and the existence of life, beginning with a story in which eggs are cooked into omelets, and then moves on to take the reader to the edges of the universe.
Here, modern discoveries in cosmology such as the accelerating universe and dark energy, quantum gravity and the possibility of time before the Big Bang, intertwine together to build a hypothesis of a multiverse in which the “arrow” of time emerges with ease from the many laws of physics.
Another perspective of time that employs a more human-centric ideal has been presented by physicist Menas Kafatos and a bestselling author, Deepak Chopra, a fellow of the American College of Physicians, Clinical Professor UCSD Medical School, researcher, Neurology and Psychiatry at Massachusetts General Hospital (MGH.) In their book, “You are the Universe,” the two come together to cover the subject of time in great detail and pose an argument: if one asks a simple question, such as, “What came before the Big Bang?” a paradox is posed.
However, Danish physicist spoke about this theory to one of his colleagues saying: “Your theory is crazy but it’s not crazy enough to be true.
The terms “before” and “after” pose a meaning only in time and in the kind that is linear. Currently, there is no evidence that time existed before the Big Bang. Atop all of that, the time that we typically think about is dependent on the human nervous system. In his theory of relativity, Einstein did not use this model when he introduced his ideas.
Einstein laid down the pillars stating that the speeding up or slowing down of time is dependent on the observer's frame of reference, proving that time is not universal. For example, if a moving observer were to travel at the speed of light, in their travels, less time would pass than it would for someone who is not moving at that speed. Time also slows down when an observer moves towards a black hole, as seen by a distant observer. These elements display that gravity has an effect on time.
If another perspective were to be adopted, it would be concluded that time is a social and human construct, especially through our experiences. If time seems linear, that is only because we have made it out to be in accord with the operatives of our nervous system (witnessing it with our eyes, which in turn stimulates the optic nerve, the occipital lobe begins working, etc.) . It is our perception of reality.
If every model were to be forgotten, an interesting event takes place. A conclusion is made that none of the proposed theories and models of time are necessary. A way to implement this idea is to think of the happenings of your life always in the present. No future, no past. This type of moment is not a clock phenomenon for clocks measure intervals (seconds, minutes, and hours) whereas present sees no interval.
It is a constant. However, reality-- the present-- is always fleeting, endlessly renewing itself which implies that the “now” is actually an “outside time.” This “outside time” can be defined as either instantaneous or eternal and both are valid verbal descriptions but fundamentally invalid since time and its vocabulary aren’t applicable to the timeless.
This idea is true of the Big Bang or to the potential end of the universe, since time doesn’t have an absolute beginning or end as we know it.
Since time proves itself to be a construct, it is a human concept that is applicable to various physical models. No matter how prominent its origin is in metaphysics, it also is in physics as well.
There is another element of time known as eternity that has its own concept. Colloquially, eternity is defined as “a long time” but that’s not necessarily true -- to this model -- because what is eternal must be outside time, or one possessing a dimension of inconceivable time. This is the type of time that can be drawn to experiences in the human consciousness. Whatever we experience determines the nature of time.
None of these conclusions are definite -- they’re dealt with cosmologists and quantum physicists and the theories behind both subject matters. In conclusion, there are many understandings and models of time.
However, the key concept is that there is no such thing as “real time” except for that constructed in human consciousness and perception.