The time we have is never enough for us. Whether we want it to flow faster or slower, we have to live in the present. When it comes to big philosophical questions, the concept of time and related ideas such as past, present and future are among the most interesting. Whether the future is definite or not, what the concept of “now” means and whether the past really exists are some of the interesting questions in this field.
The most basic question: What is time?
From a physics point of view, the concept of time has the same level of difficulties, but the reasons here are much different. Time is used almost everywhere, but in physics it is not clear why it has a particular aspect. Time is the progression of events from the past to the future through the present. Together with the three dimensions of space, it forms the space-time continuum as the fourth dimension in our universe.
The space-time continuum is a theoretical construct that helps explain the fabric of our being. Three of these four-dimensional structures consist of the terms length, width, height (or up/down, left/right, and forward/backward) that we are familiar with and can define with relative ease, while the fourth is time.
Developing special and general theories of relativity, Albert Einstein studied the laws of physics in relation to the speed of light, and eventually suggested that nothing could travel faster than the speed of light in vacuum. For Einstein, space and time were not separate and unrelated phenomena, but were intertwined in a single continuum: the space-time continuum. Nothing containing energy was located outside of time.
We experience time as something that inevitably passes, moving in a very specific direction that we think of as forward. Many laws of physics don’t seem to have a preference for whether time flows forward or backward, so scientists are looking for an explanation for these laws of physics that seem to work only in one direction. The most famous of these is the second law of thermodynamics.
second law of thermodynamics
According to this law, in an isolated system like our universe that is left to evolve, entropy (the idea that physical systems experience an increase in randomness, going from order to disorder) always increases. So we can distinguish the past from the future by looking at entropy. This is one of the ways scientists describe the passage of time as the “arrow of time”: the more disordered a system is, the less it can restore order and the stronger the arrow of time.
But time may pass differently. Einstein’s relativity proposes that gravity isn’t just an invisible force pulling objects, it’s a warping of space-time, the larger an object, the more it bends space-time around it. Therefore, time is not constant everywhere, as gravity and acceleration can change the way time travels. This can be most clearly seen in the Earth’s core, which is about 2.5 times younger than the surface, which, thanks to gravity, has slowed the clock for 4.5 billion years.
Is the past real?
Using Einstein’s special relativity also helps answer another question about time: Is the past real? How can we say that the past is real if we live only in the present and the past is unattainable for us? Einstein’s famous theory has the answer for the “now” concept. As mentioned above, the concept of “now” is dependent on the observer, since time moves differently in different environments.
The concept of “now” depends on where you are, where you’re going, and how fast you got there. Two events that occur simultaneously for one observer may occur at different times for another observer. So what appears to one person now is the past for another. The past is still there and inaccessible to us, but quite real.
Is the future pre-written?
The question of whether the future is pre-written is a question that has puzzled people for ages. All humanity on Earth is responding to this with many different concepts such as destiny, destiny or free will. Relativity defined the existence of an unchanging past and challenged the idea that there is a definite present. What kind of future could there be in this situation? Now, past and future must coexist. This is the “block universe” Einstein thought of in his theory of relativity. Past, present, and future are just slices of time, like snapshots of coexisting reality.
However, not everyone is happy with this deterministic view of the universe. For example, quantum mechanics is not very deterministic, contrary to what Einstein said. But the idea of a block universe need not have a predetermined future. Physicist George Ellis actually came up with a neat formula for Einstein’s idea that the block preserves the universe, but does not extend it into the future: While the “now” is subjective, there is a universal present, the boundary of the future (which may be different from the local arrow of time) continues to expand in the direction of time.
While we currently have some answers about time, we cannot say that all of these answers are conclusive or satisfactory. We still do not fully understand this dimension, and only time will tell if we can reach a definitive answer.
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