As you sit on your bed, legs comfortably stretched out, you notice the clock on the opposite wall. Not that there’s anything special about it, you’re just drawn by the rhythmic sound of the clock’s hand as it ticks by. It’s a constant reminder that time never stops. Or does it? Well, the clock would stop ticking if its battery died, but not time. Nope. To bring time to a standstill, we would have to stand next to something really really…. really LARGE – something that is larger than anything you have ever seen in your life. Larger than the Earth, larger than the sun, Perhaps even thousands of times the size of our Sun. This supermassive object would then have a gravitational pull so strong that nothing would be able to escape its clutches; not you, not your bed, not your watery planet. AND NOT EVEN TIME. Yes, you read that right. Gravity not only affects objects like you and me, but also affects time. The stronger is the gravitational pull, the slower would be the flow of time. Confused? We got you covered.
Imagine this. Two rivers are flowing parallelly. One has a bunch of large rocks placed in its path (with some space to navigate beyond the rocks) and the other has nothing obstructing its path. You and your friend decide to have a boat race. The rules are simple – rowing is not allowed. Thus, the boat can only travel as fast as the river flows. You position yourself on the river without the rocks as your friend positions himself on the one with the rocks. The race begins and surely enough, you’re in the lead. Why? Because the rocks obstructing the path of the other river actually have an impact of slowing down the flow of water. Thus, your river is flowing faster than your friend’s river, resulting in you winning the race. Simple isn’t it?
Now let’s play a game of substitution. Replace the flow of the river with the flow of time, since time also flows in one direction (from the past to the present to the future). Also, let us replace the large rocks obstructing the path of the other river with a supermassive object. Something so big that it has a strong enough gravitational pull that can slow down the flow of time. Everything else stays the same – the rules of the game don’t change, and you are still competing with your friend in a boat race. Why are we doing this you ask? Just for analogy sake. You see, time is like a river whose flow can only be slowed down by a super massive object, which can be compared to rocks placed in the river’s path. As you rightly inferred from our little game of substitution, time (water) flows slower when that supermassive object (large rocks) is placed in its path, compared to when it’s not. Hence, in the context of the race, your time has flown faster than your friend’s, resulting in you aging faster than him (since your friend’s time flows slower than yours, and hence he has more time).
The important thing to note here is that all this is relative. You know that you aged faster because you saw your friend’s time (river) slow down. If you weren’t racing against him, you would never have known! That’s why, relative. If you understand this, you understand the Theory of Relativity that was postulated by Albert Einstein – one of the greatest Scientists to have ever lived. Einstein’s revelation was that gravitational time dilation (the difference in elapsed time as measured by two clocks) occurs whenever there is difference in the strength of gravity, no matter how small that difference is. Why does this happen? Because that’s just how gravity works. We already know that gravity attracts all objects. Well, it also attracts time; slows it down, to be more precise. In fact, gravity has a role to play not only on our planet, but throughout the vast Universe. Gravity makes the moon go around the Earth, the Earth around the Sun, and our Sun around the Milky Way galaxy. In addition to this, it also makes time flow the way it does. Thus, without Gravity, everything would fall apart, down to the last atom.
The effects of Relativity can be observed on Earth as well, but not with the naked eye. We would need to roam around with highly sophisticated clocks in our pockets, if we wanted to see how fast or slow time has flowed for us, relative to somebody else. These highly sensitive clocks would be able to measure very minute differences in gravitational fields and report the corresponding reading. It works like this: the further we move away from the Earth’s surface, the weaker is the gravitational force on us, and faster would be the passage of time. But then again, we wouldn’t notice this on our own; we would have to compare our clock’s reading with that of our friend’s, assuming that our friend is closer to the surface than we are.
Humanity has been obsessed with the concept of immortality for time immemorial. Can GRAVITY provide us with a solution? Of course, it wouldn’t exactly be feasible for us to travel all the way to outer space and spend some time next to a supermassive object (or a blackhole for that matter). Not to mention the operational challenge of escaping from the gravitational pull of that supermassive object when you want to get back to Earth and meet your friends, who would have aged several decades by the time you’re back. YOU WOULD RETURN TO THE FUTURE. Yes, the future, because you would have aged much slower than your friends back on Earth. Sounds right out of a Sci-Fi movie? Well, it’s true. In fact, you actually age slower than someone who lives one floor above you and faster than someone who lives a floor below you. So, if you want to be immortal, try moving into a ground floor flat 😉
That could be a starting point… till our Scientists figure out an alternative!
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