TIME

(Source: BBC/The Open University)

Imagine how different one’s life would be if that person could manipulate and control time. That would be the strongest weapon ever made, granting that person an idea of how the universe works, immortality, and never-diminished consciousness. There have been many discoveries and inventions on macroscopic and microscopic levels made in the 21st century that holds immense value in understanding and studying the universe. From building small nano techs to higher-altitude satellites that can sense complicated space phenomena, we’ve progressed very far as a species. One of the greatest inventions of the human race, which I consider to be the camera, might not sound that fascinating to think of the camera as the greatest invention instead of missiles, satellites, or other scientific gadgets. But a simple camera has certain powers that other high-tech devices don’t have. It can capture time. 

Physicists believe that time had a beginning. It is argued to have begun with the Big Bang around 13.8 billion years ago. We don’t know what existed before the Big Bang, so knowing the answers is not quite relevant. All we know is that the very existence and fate of the universe were decided only after the Big Bang. Generally, in common science, we view time as a measurement. We have an idealistic view of time that is based on what the clock tells us. But in physics, the definition of time is extremely vast and complicated, and it is viewed on relativistic grounds. Does time have a beginning or an end? Is time moving in a straight line or a circle? Can time be controlled? All these questions don’t have a proper answer, as we only have models and hypotheses to answer them, not a proper law that is true in every aspect of physics. 

Time has been the subject of several ancient and contemporary philosophical ideas, but the scientific investigation into it didn't start until Galileo Galilei's work in the 16th century, and Sir Isaac Newton carried it on in the 17th. He believed that time was an unchanging concept, unaffected by any outside forces operating in the cosmos. In Newton's own words, "absolute, true, and mathematical time flows equably without relation to anything external, from its nature." Except for Einstein's Theory of Relativity, which saw time as relative rather than absolute, Newton's notion of time was mostly adhered to. Notably, the Newtonian interpretation of time is still a relatively accurate estimate of time. Non-relativistic physics is extremely relevant, just as it is in everyday life and speed.

The understanding of time changed drastically after the publication of the Theory of Relativity by Einstein( the Special Theory in 1905, and the General Theory in 1916). Although much of his works on Relativity are considered to be controversial and difficult, they have been proved mathematically and also in astronomical experiments and observations. Einstein proved the speed of light to be invariable and constant irrespective of the medium and any external factors. In his theory of relativity, time is an integral part of the fabric of the universe, so he realized if the speed of light is invariable and constant everywhere, time and space must be flexible and variable to support this. This concept later on also gave an idea of a fourth dimension, i.e time. 

With the General Theory of Relativity, the concept of space-time was further refined, when Einstein realized that perhaps gravity is not a field or force on top of space-time, but a feature of space-time itself. Thus, the space-time continuum is warped and curved by mass and energy, a warping that we think of as gravity, resulting in a dynamically curved space-time. In regions of very large masses, such as stars and black holes, space-time is bent or warped substantially by the extreme gravity of the masses, an idea often illustrated by the image of a rubber sheet distorted by the weight of a bowling ball.

The work of Einstein in his theory of relativity gave rise to the very intriguing and interesting concept of time dilation. Relative to the speed and the frame of reference, the time will differ in each observer’s case. This concept is called time dilation. Suppose, hypothetically, that we observe a spaceship that is moving at 99 percent of the speed of light; the clock will seem to be twice as slow as normal, and the astronauts will seem to be moving in slow motion. At 99.9999 percent of the speed of light, the factor becomes around 707 times larger, increasing exponentially. Were we at the speed of light, would time freeze? Well, it is a great question without any true scientific answer right now.

The possibility of Time Travel came on the rise after Einstein’s relativity theory. One needs to know that even if we were to travel close at the speed of light, it would take 100,000 years to reach a distant star 100,000 light years away as judged by the earth’s clock but during the travel, the astronaut may hardly age which generates the possibility of time travel. There are several paradoxes and hypotheses on time travel but it is a matter of time before people prove it. We still don’t have any physical evidence of time travel, although the concept is not logically and mathematically wrong. 

When Einstein published his General theory of relativity, he proposed a deep theory about gravity and how it affects time. This is also called Gravitational time dilation which means, if we were to be pulled towards a strong gravitational pull, the time will become slower for us according to the gravitational intensity. Again these theories are not relevant in daily life, as it is very hard to observe and make very less difference. Technically, a person living in a ground-floor apartment ages slower than their twin who lives in a top-floor apartment of the same building (due to the difference in gravity they experience), the effect might amount to maybe a microsecond over a full lifetime. There is, however, one aspect of modern everyday life where we do experience the effects of gravitational time dilation: it has a noticeable impact on the Global Positioning System(GPS), which many of us now rely on for navigation. The orbiting satellites used by the GPS experience significantly less gravity than the Earth’s surface, and are also moving very fast so that the time distortion effects of about 38 microseconds a day. 

(Earth's mass warps space and time so that time actually runs slower the closer you are to earth's surface. Although this is a very weak effect, the time difference can be measured on the scale of meters using atomic clocks. Public Domain Image, source: NASA.)

A black hole spins at close to the speed of light, dragging anything in the vicinity around it, and the huge gravitational pull of a black hole can bend and warp space-time to a substantial degree. If we were to go near it over the “event horizon” of a black hole, a hypothetical clock on a spaceship (and indeed the progress of the spaceship itself) would appear from the outside to stop completely due to the infinite time dilation effect. At the gravitational singularity at the center of a black hole, gravity and density are infinite, and all the normal rules of physics just break down.

In the 20th century, a new theory of physics came into existence which surpassed classical physics as well as Einstein’s relativity theory. Quantum physics is now regarded as the most correct and accurate theory by physicists which is particularly based at sub-atomic levels. A discrete implication of quantum mechanics states that a lot of properties in this universe are quantized. Is time quantized? The answer is No as per today’s findings and conclusions were drawn by quantum physicists. But there are certain paradoxes even in quantum physics, that tell time is quantized. The physics that we’ve right now is quite incomplete. The mystery of time still lives on and yet there are a lot of findings that people have to discover to understand the universe better.