In his final book, published just before he died in 2018, legendary physicist Stephen Hawking sought to answer some of humanity's greatest scientific questions concisely yet insightfully. True to its title, the book provides short but informative responses to 10 fundamental queries about our universe and existence. The first six questions are rooted in Hawking’s scientific background, and the remaining four display his wisdom and creativity.

While the answers are inevitably simplified discussions of enormously broad subjects, Hawking conveys a sense of the current scientific understanding in a way that maintains interest. Perhaps a by-product of his illness, Hawking has always chosen his words concisely for his electronic voice to deliver maximum impact, and his dry humour (an outcome of his British upbringing, I suspect) brings a spark to the at times mundane, indecipherable talk of science. His ability to distil profound scientific concepts into thought-provoking discussions displays a remarkable curiosity for exploring the vastness of cosmology, unwavering but never egotistical.

“When we see the Earth from space, we see ourselves as a whole. We see the unity, and not the divisions. It is such a simple image with a compelling message; one planet, one human race.”

Each topic is limited to a few pages, and the book maintains a brisk pace that stops it from becoming dry or repetitive. Mind you, although the book starts off easy and intuitive, it does escalate to a technical point where I had to reread the chapter multiple times for anything to make sense. But then it reminds me of why physics was my favourite elective back in high school and brings to mind popular notions that many sci-fi series scratch the surface of, like the “Grandfather Paradox” from Umbrella Academy (still one of my favourite Netflix series ever). It’s a revelation when you realise that much of science is conceptual, requiring a tinge of imagination and creativity, as you would expect for anything invisible to make sense.

Unless mathematics is your thing, you may, at one point, struggle to finish or understand the book, but I took solace knowing our universe is governed by rational laws that at least the elite of the science community will discover and understand. The book is a perfect introduction to contemplate humanity's storied yet ongoing effort to comprehend our place in the grand tale of the universe.

The Big Questions summarised:

1. Is there a God?

No. The laws of nature are fixed. Science provides better and more consistent answers, but people will always cling to religion for comfort. Saying the laws are the work of God is more a definition of God than a proof of his existence. Time didn’t exist before the Big Bang, so God had no time to make the universe.

2. How did it all begin?

The universe was scrunched 10 to 15 billion years ago into a single point of infinite density, a space-time singularity, i.e., the Big Bang.

But the universe has many possible histories, each with its probability. It will probably end in a Big Crunch (the reverse where everything falls together) or in a less dramatic way when gravity is too weak to stop the galaxies from flying apart forever, and the universe gets emptier and colder.

3. Is there other intelligent life in the universe?

Possibly, but if so, we have yet to encounter it.

Possibility 1: There was a reasonable probability of forming self-reproducing systems, but most of these life forms did not evolve intelligence.
Possibility 2: Earth has not had any significant collisions in the last 66 million years (since dinosaurs were wiped out). Other planets in the galaxy on which life has developed may not have had a long enough collision-free period to evolve intelligent beings.
Possibility 3: Life may have formed and evolved into intelligent beings, but the system becomes unstable, and the intelligent life destroys itself.
Possibility 4: Other forms of intelligent life are out there, but we have been overlooked.

4. Can we predict the future?

No, and yes. The laws allow us to predict the future in principle. But in practice, the calculations are often too complex.

Laplace’s classical view was that the future motion of particles was determined entirely if one knew their positions and speeds at one time. This view was modified when Heisenberg put forward his Uncertainty Principle, which said that one could not accurately know both the position and the speed, though it was still possible to predict one combination of position and speed. A limited predictability that might disappear once black holes are considered.

5. What is inside a black hole?

One can’t tell from the outside what is inside a black hole, apart from its mass, electric charge and rotation outside the event horizon, which means it contains much information hidden from the outside world.

However, there is a limit to the amount of information one can pack into a region of space; if there’s too much information, it will collapse into a black hole, the size of which will reflect the amount of information.

Information is stored on the horizon, the surface of the black hole, which indicates that what has fallen into the black hole goes beyond these three characteristics, though it is unclear what exactly. This paradox has yet to be solved.

6. Is time travel possible?

Rapid space travel and travel back in time can’t be ruled out. But they wouldn’t be possible if general relativity is correct and energy density is positive.

Time travel requires a spaceship to travel faster than light, and Einstein showed that it would take infinite rocket power to accelerate one beyond the speed of light. The question is whether we can make space-time so warped that one can return to the past. Ordinary matter curves space-time back on itself, like the surface of the Earth. To create a wormhole, one needs matter with negative mass and energy density to warp space-time in the opposite way, like the surface of a saddle.

If time travel were possible, why hasn’t someone come back from the future to tell us how to do it? Not to mention the tremendous logical problems that it would cause. Unless space-time can only be warped to allow time travel in the future, we have yet to observe its effects.

7. Will we survive on Earth?

One of the below threats will inevitably cripple the Earth at some point, including asteroid collisions (the last one killed the dinosaurs 66 million years ago), running out of space, climate change and nuclear war.

If we remain on Earth, we risk being annihilated. It is time to explore other solar systems.

8. Should we colonise space?

Yes, even though most planets and moons in our galaxy are uninhabitable, and interstellar travel is impossible under current technology. Investing in space travel is expensive but a small cost relative to the world’s GDP; the alternative would be to remain on Earth until humanity fizzles out.

The space race may also rekindle a fascination with science that will continue accelerating our technological progress in disciplines beyond space travel.

9. Will artificial intelligence outsmart us?

If computers continue to obey Moore’s Law, they will overtake humans in intelligence at some point in the next hundred years. The key is ensuring they remain in control with goals aligned with ours and cultivating the wisdom in us to use technology for good.

10. How do we shape the future?

The future depends on science and technology to deal with our current problems and revolutionise every area of life. Most notably, we need to explore space for alternative planets on which to live and make a positive use of artificial intelligence to improve our world.