May 12

The Speed of Time

Speaker: Sandip


Sandip P3Good evening, toastmaster of the evening, fellow toastmasters and distinguished guests. I am Sandip and I’ll be embarking on my Project 3 with a speech titled – The speed of time. Before I begin, I’d like to have a show of hands on how many here have watched the movie, Interstellar? How many understand the concepts that were shown in the movie?

The purpose of my speech today will be to introduce a theory called Time Dilation, so that when you either watch or re-watch it, you can appreciate how scientifically sound the movie really is! For those who have not watched Interstellar, it is about space explorers looking for a new planet to inhabit as the Earth is near death. And for those who have no background in astrophysics, fear not, I will be staying away from the complicated mathematics that’s needed to explain the theory. I’ll try to introduce Time Dilation with 3 simplified concepts.

Concept 1: Space and Time are related.


We always think of space and time as independent but it’s not. For example tomorrow, I’m going to meet my friends at Dhoby Ghaut MRT (space) at 730pm (time). Space and time always go together – one is meaningless without the other. Same in astrophysics, space and time are treated as one and it is represented as Space-Time. Space-time is an imaginary rubbery fabric where astronomical events take place. Having introduced this seemingly simple concept, now we move on to bigger things!

Concept 2: Objects bend Space-Time.


Our Sun, the stars, planets everything exists and interacts on the fabric of Space-time. And what happens when we put a planet like our Earth on the rubbery fabric? The surface of Space-Time bends! What happens if we replace the Earth with the Sun? Space-Time bends more – simply because the Sun is more massive. Now we put our Sun and our Earth into our space time fabric. Something interesting happens.


Both of them bend space time proportional to their masses – but due to the Sun’s larger effect, the Earth, rolls in towards it. This phenomenon is called – Gravity – and it depends on the mass of objects. Simply put, the more massive the object, the more it warps space-time and the greater its gravitational pull. Now it’s no wonder we are all attracted towards Clement so much because he can bend Space-Time so much more! Anyway, now things are getting more complicated but let’s get a little bit deeper into the rabbit hole and take a look at an extreme case scenario with concept number 3.

Concept Number 3. Speed of time is not constant.

Who agrees with me that we reach our destination earlier if we drive faster? So does time slow down as we go faster? Yes, but in the millionth of the billionth of a second – makes no difference to us. But time slows down measurably only when you are about to reach a critical speed – the speed of light. This phenomenon is predicted near Black Holes.


A black hole is simply a dead star. When a star 20 times the mass of the Sun dies and is compressed to the size of a pin head, it forms a black hole, essentially a pit of infinite gravitational pull. The force of gravity is so strong that not even light can escape – thus giving it the color and the name – a Black Hole. But how does our Space-time fabric look like near a black hole? Not only there is a curving of space-time but it is stretched beyond recognition. Now if we have a planet A which is near a Black Hole, what happens?


It’s the same as what happens when you drop a ball into an infinitely deep hole; it picks up speed towards the speed of light. And what happens to time on the planet? It slows down! This effect is called Time Dilation. So, we see that an incredible amount of gravity can actually slow time down.


In Interstellar, when the space explorers went to an alien planet which was under the gravitational pull of the nearby Black Hole, it was in their best interest to get in, do what they needed to and get out as soon as possible – because 1 hour of the time in the alien world, was equivalent to 7 years on Earth. Now try to imagine yourself spending one hour at work to go home to realize that your family has grown by older by 7 years! I shall leave this here so as not to spoil the movie for those who intend to watch it!

In summary, I have introduced 3 concepts that are needed to get an inkling of how Time Dilation happens near Black Holes – just like what happens in Interstellar. The concepts, to recap, are, Space and Time are always related, gravity bends Space-Time and the speed of time is never constant. Putting these 3 together, we saw that higher the force of gravity, slower the speed of time. So if you want to slow time down to beat that timer’s bell in your next toastmasters’ speech and you had a choice to either give your speech either on Earth or Mars, it’s always do it on Earth because time runs slower here! Thank you!

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