The arrow of time

“Daddy, why does time go forward? Why can’t time go backwards?”

I got asked a very simple question by my six-year-old that got the rusty gears, pulleys, and levels cranking in my head.

It’s not an easy question to answer. There is a lot to unpack here.

We take for granted that the arrow of time moves forward because of causality, but the actual physics behind this is a bit more complicated. What if you could actually run time in the reverse direction like playing a tape backward? (Millennials: look up tape; it is real).

Of course, we can observe the past locally and right now- light from stars that exploded billions of years ago is still reaching us now: what we are observing in the past is being experienced in the present. But generally we think of time going forward.

So what’s the answer?

“Time moves forward because, that’s how nature is” or “God made it that way” or “Rules are rules:” But none of these are satisfactory answers to me. So I invoked entropy.

I said “when you break an egg and the yolk spills out, you can’t unbreak it.” It’s a poor way of trying to refer to the second law of thermodynamics. Entropy, which roughly translates to chaos, has been increasing since the universe was created; time moves forward because it is linked and so also unidirectional.

But after the kid went away unsatisfied, my brain went into overdrive. No one actually knows if “time” was created with the universe or if time exists as an entity independent of the universe. Because there’s no way to know. Newton believed that time was absolute and independent of the universe and the universe was simply the stage on which events played out. Clocks were clocks everywhere and counted the same time. This concept has not aged well after Einstein and quantum physics.

As an aside, there’s nothing sacred about our clocks or how we measure time. An hour has 60 minutes because 60 was the favorite number of the ancient Babylonians. They didn’t have fractions and 60 is good for commerce since it can be divided by merchants by 1,2,3,4,5,6… Our clocks move in the direction we call clockwise because they followed from sundials and the people who developed them lived in the Northern Hemisphere. Had civilizations come up in the Southern Hemisphere they’d be invented to run in the opposite direction.

But I digress: back to the concept of time. Einstein changed our views. He made the huge observation that time isn’t absolute or independent and that time and space and linked completely: the curvature in this spacetime is what we call gravity.

Einstein imagined time as another dimension, as another direction like “length” outside of the three that physical objects embody. And this is where it gets weird. Einstein thought we can’t physically observe the time dimension because our brains are three-dimensional.

Einstein also believed that all times coexist– the past, no less than the present or the future. It is only human consciousness and imagination that constructs the physical passage of time. We made this up. So according to Einstein, time does not go forward at all!

And here’s why this works mathematically. If you try to solve the big equations of physics with a negative value of time, they still work. Theoretically, there’s no reason for time to be unidirectional.

For the longest time, a number of physicists thought the universe would expand to a maximum and contract. Time would then play in reverse. Even Hawking wrote the possibility of flipping time after a maximum expansion of the universe. But how? Don’t as me about this one. I find it far-fetched.

Of course, after Einstein came quantum physics which he quarreled with– On the quantum scale, time might not exist as we know it. Most quantum physicists don’t think time is a fundamental property but an emergent one- a secondary result of the universe.

Finally, there are a number of physicists who believe that time does not exist at all. Events are a bunch of “Nows” which we piece together like torn pages of a book or frames of a movie to make a coherent story. Thankfully, this theory is not mainstream, but it is still possible.


A simple iron dagger

After the ancient Egyptian King Tutankhamen died, an iron-blade dagger with a gold sheath was placed in his sarcophagus. This was rediscovered in 1925 after thousands of years.


Nowadays, the gold sheath attracts our attention, but in ancient times, the iron would’ve been much more valuable.

I never thought about this before now.

You might recall the news stories two years ago about this particular iron dagger. There was a scientific article that showed that it was likely of meteoric origin- that it literally fell out of the sky!


Iron is the most abundant element on earth. Why would it be so valuable in ancient times?

And then it dawned on me. The answer, quite simply is that is very little free iron on the earth’s crust. Most of the iron is in ores. Before the iron age, or more accurately before iron smelting was developed, the only way to get iron metal would be from falling meteorites.

The oldest discovered iron, also in Egypt, was of decorative iron beads. And yes, you guessed right- these are also of meteoric origin. They had to be.

For most of humanity iron was this abundant, versatile metal in the ground but no one knew how to extract it or use it!



#MeToo: what should men do?

Friends, I think it is time to address the elephant in the room- #MeToo. Women in India (and elsewhere) are rising in massive numbers to report cases of sexual harassment and assault.

What should men do? How should they react?

To decent men who are wondering what they should do at this moment: speak out against systemic sexual harassment and support the survivors. Just as people who have never experienced racism should speak out against it, men who’ve never been sexually abused should speak out too.

Check your privilege. Listen with humility. There are so many stories.

Introspect. What can you do to make the workplace or neighborhood safer? Racism will not be destroyed only by people of color. The patriarchy will not be dismantled only by women.

I’m learning everyday just how difficult it is for women to come forward in a toxic culture of shaming, victim-blaming, mob threatening and violence, and male impunity. Have an honest conversation with your loved ones. Be respectful: you do not have the right to invalidate anyone else’s experience.

There’s a very basic, low bar for being a decent human being, and men (in the collective) have failed to reach it. If you’ve never sexually harassed or assaulted anyone, congratulations. Here is your prize: you get to start at the very bottom rung on the ladder. And the rest of you? The rest of you, you deserve the lava pit.

Lastly, do not normalize violence as “everything goes”. I do not watch Salman Khan movies. I will not watch Ronaldo in any football match. I will not patronize any comic or journalist who abused or tolerated abuse, regardless of “talent”. If that means I’m sitting at home arranging and rearranging books on my shelf all day, so be it.

Talent or skill is simply the worst excuse: the world will survive and be much better without men who lack humanity.


One of the greatest archaeological discoveries in modern times is the library of Ashurbanipal in the Assyrian city of Nineveh, where there were tens of thousands of tablets with gorgeous Akkadian cuneiform text.

This is an image of a portion of the epic of Gilgamesh from Nineveh, now at the British Museum. I hope to visit the British Museum someday.

Assyrians imported Babylonian culture much in the same way the Romans imported Greek, and Japanese imported Chinese culture. It is said that when Assyrians enslaved Babylonians, they chained their scholars and made them write everything they knew to take their knowledge. All of this was captured on clay tablets.

The entire library of Nineveh burned down, but unlike the destruction of the library of Alexandria centuries later, the books were not completely lost. Because the writing was on clay, each tablet was baked in the fire and became hardened and preserved.

Before I go to the grocery store

What is our place in the universe? To know this, it is important to know who we are and where we came from. Anthropologists believe that modern humans have existed on earth for roughly 300,000 years. If I used my calculator correctly that translates to 0.008% of the time all life has existed on this planet. Indeed, we are not even a blip on the radar of time!

What were our ancestors like? As I mentioned, modern humans evolved 300,000 years ago from an earlier species. We know from bones that at least 150,000 years ago, humans had the same anatomy- the same brain size and capacity for thought that we have today. Did they have history and art and culture like we do? Did they express love and hope and sorrow? We do not know because their lives are lost to us. All of modern human is confined to the last 10,000 years. Written history is even shorter, around half that time. Our collective memory is short.

We know that modern humans came out of Africa 50,000 years ago. Then, there were two catastrophic bottleneck events that nearly wiped us out, and reduced modern human populations to a few thousand people (from whom we are all descendants). That was the closest that our ancestors came to extinction and because they survived we can watch IPL cricket matches today on flat-screen TVs.

But though all of our history is 10,000 years old, a few of our Paleolithic ancestors left us some of our finest art. Let me end on an upbeat note before I go to the grocery store to pick up cashews for pulao that is being cooked today.

This cave painting at Chauvet-Pont d’Arc from 36,000 is one of the OLDEST works of art that humans created that we have found. Isn’t it gorgeous?


(The paintings of these lions at Chauvet-Pont d’Arc are twice as old as the bison paintings at Altamira mentioned in “Agantuk,” which are ~16,000 years old)

Tea time

No one could have predicted in 1690 that in 50 years tea would become the national drink of England. Tea was perhaps the first truly global commodity. The East India Company had a wildly successful marketing campaign to popularize tea in its early years, but all of it came from China. Along with tea, came all the paraphernalia, cups and plates, colloquially still referred to as “china”.

Back then, the well-known tea merchant, Twining’s opened both a coffee-shop and a tea-shop, and was more convinced that coffee would pick up sooner.

It is fascinating how tea, an ancient Chinese drink (that they still drink without sugar or milk) took off in England at the same time that sugarcane became widely available. The English were the first to popularize and widely consume tea with milk and sugar.

A few years later, tea cultivation was introduced in India to break the trade imbalance with China caused by tea importation. Tea in India has never looked back since.

Hokusai and the pursuit of perfection

Hokusai is by far the most famous Japanese artist in the world. The Great Wave off Kanagawa from “36 Views of Mount Fuji” is well known everywhere.

Hokusai was a creative genius but he was very humble. He painted all his life and was famous, but is known to have said- “I didn’t do anything worthwhile until I was fifty.” He also said, if I can keep painting until I am 110, I will finally learn the true nature of things.

One story about Hokusai demonstrates his genius. He was asked to participate in the drawing competition at the royal court of Shogun Tokugawa Ienari. For his depiction of the Tatsuta River in Japan with red maple trees, he drew a bold, blue curve on a white canvas with his paint brush and then chased a chicken with its feet dipped in red ink across the curve to make the leaves. Needless to say, Hokusai was the winner!