## A Piece of Paper as Thick as the Universe

###### By Anupum Pant

Linear growth is only what we can visualize well. Estimating things that grow exponentially, is something not many of us can do properly.

Here’s what happens when you fold a piece of paper. A paper of thickness 1/10 of a millimetre doubles its thickness. On the second fold it is 4 times the initial thickness and so on. It doesn’t really seem like it would grow a lot after, say, 10 folds, right?

After 10 folds, the paper which was about the thickness of your hair, turns into something that is as thick as your hand.

Without any calculation, how thick do you think would it become if you could fold it 103 times?  (I know, no one has ever folded a paper more than 12 times)

Think about this for a second: How many times do you think would you have to fold a paper to make it 1 kilometre thick? The answer is 23. Yes, it takes just 13 more folds to go from the thickness of a hand to a whole kilometre.

Turns out, if you manage to somehow fold a paper 30 times, it would become 100 km tall. The paper would now reach the space.

For the sake of imagining how exponential growth works, a paper folded 103 times would be about 93 Billion light years thick – which is also the estimated size of the observable universe.

Watch the video below to see one other great example of how exponential growth can mess with you.

## Moving Light Captured on Camera

### The speed of light

In vacuüm, light travels 299,792,458 meters in a single second. In other words, in a single second it travels 186,000 miles. To establish a  perspective, if I could move that fast, I would circumnavigate the world in 0.13 seconds. A hypothetical jet plane would take more than 2 days to do the same. In short, it is fast. It is the fastest – Nothing beats light.

If you try to record moving light on a home camera, you’d fail miserably. That is because normally they can roll only about 30 to 60 frames per second. In fact, you’d not even be able to capture a fast-moving ball without motion blur, forget recording moving light. To record fast things you need fast cameras that can roll several thousands of frames every second.

In the past, high-speed-cameras, rolling film at thousands of frames per second have been able to record bullets moving in slow motion, bubbles bursting, people getting punched and what not! MythBusters use such cameras for almost every experiment they do.

But light travels a million times faster than bullets. Till the year 2011, to capture moving light on film was considered an impossible feat; and then, a team from MIT media lab invented this.

### A 1,000,000,000,000 FPS camera

A camera that can record at a speed equivalent to a theoretical one-trillion-FPS camera was invented by a team at MIT media labs in the year 2011. This camera can record light moving through space, in slow motion! To look at what it can do, you’ll have to watch the video below. In the video, the researcher explains its mechanism in detail.

It is theoretically impossible to craft a mechanical device that can roll film at such extremely high speeds. To tackle this physical limit, these geniuses invented a whole setup containing several cameras sensors that work together to make this feat possible.

Note: In reality, the camera doesn’t record the footage of a trillionth of a second. It is a composite video of lines of different pulses of a laser recorded and stitched together. The time it takes to compile enough data for the video, is more than what it takes the light to travel from one end to another.