This question always fascinates physicists and curious minds like us.On a very basic level, time is something we measure through a gadget called Clock. Among physicists, there is no real doubt that time does really, truly exist. It’s a measurable, observable phenomenon. Physicists are just divided a bit on what causes this existence, and what it means to say that it exists. Indeed, this question borders the realm of metaphysics and ontology (the philosophy of existence) as much as it does on the strictly empirical questions about time that physics is well-equipped to address.If I define it in a general way with respect to reality then time is nothing but the passage of moments we call our past, present and future which cannot be reversed or skipped, at least within the same timeline.
Till now time is quoted in frames of hours,minutes and seconds,But if we take this simple concept of time to the level of the universe then things get way more complicated than our level of understanding. How? And why? Let’s try to get a better and simple understanding.
Think of a situation where you have to meet someone, maybe your date XD(just kidding). So For a perfect meeting you should be knowing answers to a few questions like where?(location as latitudes longitudes, means a three dimensional information) and when? You will notice that even though we are living in a 3D world, we are still using time as the answer of our question to ‘when?’ And this is the explanation why scientists do believe in time as another dimension. Which implies at what time particle needs to be where, is a dimensional explanation. Therefore, while travelling through space-time fabric exact measurement of time is must.
Scientists like Albert Einstein and Stephen Hawking have suggested various ideas related to time which give rise to many other factors and theories which we generally see in movies and documentaries. Before any further explanation let us simplify what Physics has to say about the same.
Arrow of Time
The explanation that is usually given as to why we don’t see broken cups jumping back onto the table is that it is forbidden by the second law of thermodynamics. This says that disorder of or entropy always increases with time. In other words, it is Murphy’s law –things get worse.
An intact cup on the floor is a disordered state. One can therefore go from the whole cup on the table in the past to the broken cup on the floor in the future, but not the other way around. The increase of disorder or entropy with time is one example of what is called an Arrow of Time, something that gives a direction to time and distinguishes the past from the future. There are at least three different arrows of time,something that gives a direction to time and distinguishes the past from the future.
- Thermodynamic arrow– the direction of time in which disorder or entropy increases,
- Psychological arrow- the direction in which we feel time passes, the direction of time in which we remember the past but not the future,
- Cosmological arrow-the direction of time in which the universe is expanding rather than contracting.
We are still believing in the fact that our universe, in which we are existing, is bounded and designed with certain laws of physics which aint’t very clear to us whenever it comes to atomic level. So for instance, consider another universe with opposite laws of physics as ours, let’s understand it in terms of the opposite second law of thermodynamics, where entropy is actually decreasing unlike us. So it could be like ageing younger, and not remembering the past but future of their timeline…..damn it is really unusual and even harder to imagine. But as per our laws where the universe is considered to be an isolated system, it can never move backward to the point it was ever before.
And this explanation leads us to Einstein’s theory about time which states that time is relative -that cannot move backwards and is something which depends on speed of frame of reference. Which gives a concept of time dilation.
A yt video (7) Time Dilation Explained in 6 Minutes – YouTube for reference
Time Dilation
You must have heard of this event where a space traveller returns back on earth after spending a few days in space is barely aged but the person of the same age as the traveller on earth has grown way older already. And it happened because of Time Dilation. When the spaceship was moving very fast through space,time started moving slowly for them. Or maybe they were orbiting way heavier celestial body around which time wraps intensely and again starts passing slower for travellers in comparison to time passing on Earth.
According to me this is the simplest way of getting started and understanding the concept of time dilation and for more you can refer to this link.
And because of this time dilation here enters a concept of Time travel, if moving through time is really possible? Or can we move into the future or travel to the past? We would like to hear your thoughts about this concept in the comment section below. According to your understanding of this blog, share your POVs.
[1] By Shagun Thakur
shagunth@gmail.com
