Imagine if you knew that there is a possible way to travel to another universe or that you could sit in a time machine and be transported to another time, preferably right before Sholay was about to be released and you were among the first ones to watch it!

Sounds like a bad Science Fiction plot, right? But what if you were told that though improbable, it is not impossible? Only because of these elusive secretive dark and strange things that exist in our universe, called black holes!

So what is a black hole? 

We generally tend to think of gravity as that thing that made for Newton's apple of the day. In his lazy afternoon slumber under a tree, he discovered why we tend to remain down to earth and not spontaneously fly away unless punched hard 'Bhai' style. And, so, we got to learn that earth has well-defined gravity, say G, which acts upon us, our neighbor and everything and everyone around us. And because the moon is lighter than the earth, its gravity is smaller than ours. On the flip side, there is also a possibility that there is something out there which is a million times gravitationally stronger than earth. That's when things start getting all funky. Why? Because if earth's gravity is already strong enough to stop the heaviest of heavies from floating, think what something a million times stronger could do. It could pull in everything around it. Literally everything, including light! And when light cannot escape, whatever it cannot escape from becomes the blackest of black pits – a black hole.

When it is time for stars to die, they don't usually take the RIP thing seriously. Instead they go through a dramatic prolonged approach to death, much like any beloved Bollywood hero, on his deathbed. The star begins to collapse and collapse, and collapse some more, falling into its core to become this extremely dense and massive object. With a body so dense and heavy that even light gets sucked in, you can easily think of the grisly situation of what will happen if you or a rather attractive scenario that your noisy neighbor, say Pappu, gets close to one. You can imagine one of three things that could happen to you, or Pappu. 

A) Pappu's obituary appears the next day – annihilated by the heat of radiation coming from all the material getting sucked in the black hole.

B) The gravitational pull from Pappu's head to toe may differ so vastly that he may just be torn into two pieces, excuse the image, like string cheese.

C)  The ever wondrous possibility that Pappu falls into the bottomless pit, only to emerge in another parallel universe – the perfect recipe for a Sci-Fi thriller. 

So taking the non-violent route of exploring the wonders of a black hole, let's look into possibility C!

Can a black hole take us to another time or another universe?

Before we explore the possibilities, we might need to understand why we are asking this question.

You see, you might have to unlearn a few things here. Remember Newton's concept of two massive bodies attracting each other due to gravity? It is all good as long as the strength of gravity is not huge. Because Newton's concept basically finds itself nowhere when the strength becomes large, and certainly not in an infinitely large gravity like in a black hole. So how does one treat objects in and around a massive black hole like gravity? Well, Einstein's General Relativity (GR) comes to rescue. According to GR, imagine the entire universe is sitting on a rubber sheet and as you walk around it, you move in both space and time. But when you put something massive, it warps the rubber sheet. And when there is enough of a warp, other objects roll towards the warp and find themselves orbiting around the warp.

That warp you see in the image starts getting deeper and deeper as the mass increases, leading to a never ending pit if a massive black hole sits on the sheet. With such exotic distortions to the otherwise benign space-time mesh, a few even more exotic outcomes are possible.