What Is Time, And How Do We Know It Exists?


Time. There isn't enough of it for us. Even though we are always being taught to live in the now, we desperately want it to move faster or slower. The idea of time and associated concepts like past, present, and future are among the major philosophical issues. Has the future been predetermined? Why do we use the term "present"? Existence of the past?


Time is problematic from a physics standpoint, but for different reasons. Almost everybody uses time, although it's unclear in physics why it has a certain direction. Events move forward through time as they pass from the past into the future. Together with the other three dimensions that make up the space-time continuum, it constitutes the fourth dimension in our universe.


The flow of space-time

A theoretical idea that helps explain the basic foundation of our existence is the space-time continuum. The four dimensions are length, width, height, often known as up, down, left, and forward, and time.

Albert Einstein studied the relationship between the rules of physics and the speed of light when formulating his theories of special and general relativity, and he came to the conclusion that nothing can move faster than the speed of light in a vacuum. Einstein believed that time and space were not two distinct phenomena that were unrelated to one another but rather were intertwined to form the space-time continuum.

Time has no meaning for anything that possesses energy.


How does time pass?

We perceive time as something that necessarily moves forward in a manner that we feel to be in our favour. Scientists have been looking for an explanation for those physical rules that only appear to operate in one direction because many physical laws do not appear to care whether time moves forward or backward. The second law of thermodynamics is the most well-known of them.


This law states that entropy, the notion that physical systems increase in unpredictability, going from order to disorder, always increases in an isolated system (like our cosmos) left to evolve. So, by examining the entropy, we can tell the past from the future. One method that scientists explain the passage of time is through the so-called "arrow of time," which is said to get stronger as a system becomes more disorganised and less able to reestablish order.


But time might pass in several ways. According to Einstein's theory of relativity, gravity is a warping of space-time as well as an unseen force that attracts objects; the more massive an object is, the more it warps space-time around it. As a result, time is not constant everywhere since acceleration and gravity can alter how time moves. This is most obvious because Earth's core is roughly 2.5 times younger than the surface, thanks to gravity delaying the clock over 4.5 billion years.


What is history?

Another concern about time that is addressed by using Einstein's special relativity is whether or not the past is actual. How can we claim that the past is real if we just exist in the present and have no access to it?


Einstein's well-known theory about the concept of "now" provides the solution. The concept of now is observer-dependent because, as was already mentioned, clocks function differently in various situations.


Where you are, where you're going, and how quickly you're moving all affect how you define "now." For some observers, two events may occur simultaneously, whereas for others, they may occur at distinct times. So, what is currently apparent to one individual is actually the past to another. Although it is out of our reach, the past is nevertheless very much present.


Is the future already written?

Now, that is a question for the ages. Call it destiny, fate, or free will, humanity across the world has tackled this question. Relativity has set the past in stone and challenges the idea that there is a specific now. So how can there be a future? Present, past, and future must co-exist. This is the "block universe" that Einstein envisions in relativity. Past, present, and future are just slices of time, like snapshots of reality all co-existing.


But not everyone is happy with this deterministic view of the universe. Quantum mechanics, for example, is not very deterministic, despite what Einstein said. But the block universe idea doesn’t have to have a predetermined future. Physicist George Ellis actually came up with a neat formulation of Einstein’s idea that preserves the block universe but doesn’t extend it into the future. While "now" is subjective there is a universal present, the boundary of the future that continues to expand in the direction of time (which may be different from the local arrow of time).


So, the past is written and the future is up for grabs. But carpe diem, seize the day and trust very little in tomorrow. We do have some answers about time but not all of them are satisfactory; we still lack a full understanding of this dimension. If we’ll ever get one, well, only time will tell.

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