From the nature of the universe (that’s if there is only one) to the purpose of dreams, there are lots of things we still don’t know – but we might do soon. A new book seeks some answers

What’s at the bottom of a black hole? See question 17. Photograph: Alamy

1 What is the universe made of?

Astronomers face an embarrassing conundrum: they don’t know what 95% of the universe is made of. Atoms, which form everything we see around us, only account for a measly 5%. Over the past 80 years it has become clear that the substantial remainder is comprised of two shadowy entities – dark matter and dark energy. The former, first discovered in 1933, acts as an invisible glue, binding galaxies and galaxy clusters together. Unveiled in 1998, the latter is pushing the universe’s expansion to ever greater speeds. Astronomers are closing in on the true identities of these unseen interlopers.

2 How did life begin?

Four billion years ago, something started stirring in the primordial soup. A few simple chemicals got together and made biology – the first molecules capable of replicating themselves appeared. We humans are linked by evolution to those early biological molecules. But how did the basic chemicals present on early Earth spontaneously arrange themselves into something resembling life? How did we get DNA? What did the first cells look like? More than half a century after the chemist Stanley Miller proposed his “primordial soup” theory, we still can’t agree about what happened. Some say life began in hot pools near volcanoes, others that it was kick-started by meteorites hitting the sea.

3 Are we alone in the universe?

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Perhaps not. Astronomers have been scouring the universe for places where water worlds might have given rise to life, from Europa and Mars in our solar system to planets many light years away. Radio telescopes have been eavesdropping on the heavens and in 1977 a signal bearing the potential hallmarks of an alien message was heard. Astronomers are now able to scan the atmospheres of alien worlds for oxygen and water. The next few decades will be an exciting time to be an alien hunter with up to 60bn potentially habitable planets in our Milky Way alone.

4 What makes us human?

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Just looking at your DNA won’t tell you – the human genome is 99% identical to a chimpanzee’s and, for that matter, 50% to a banana’s. We do, however, have bigger brains than most animals – not the biggest, but packed with three times as many neurons as a gorilla (86bn to be exact). A lot of the things we once thought distinguishing about us – language, tool-use, recognising yourself in the mirror – are seen in other animals. Perhaps it’s our culture – and its subsequent effect on our genes (and vice versa) – that makes the difference. Scientists think that cooking and our mastery of fire may have helped us gain big brains. But it’s possible that our capacity for co-operation and skills trade is what really makes this a planet of humans and not apes.

5 What is consciousness?

We’re still not really sure. We do know that it’s to do with different brain regions networked together rather than a single part of the brain. The thinking goes that if we figure out which bits of the brain are involved and how the neural circuitry works, we’ll figure out how consciousness emerges, something that artificial intelligence and attempts to build a brain neuron by neuron may help with. The harder, more philosophical, question is why anything should be conscious in the first place. A good suggestion is that by integrating and processing lots of information, as well as focusing and blocking out rather than reacting to the sensory inputs bombarding us, we can distinguish between what’s real and what’s not and imagine multiple future scenarios that help us adapt and survive.

6 Why do we dream?

We spend around a third of our lives sleeping. Considering how much time we spend doing it, you might think we’d know everything about it. But scientists are still searching for a complete explanation of why we sleep and dream. Subscribers to Sigmund Freud’s views believed dreams were expressions of unfulfilled wishes – often sexual – while others wonder whether dreams are anything but the random firings of a sleeping brain. Animal studies and advances in brain imaging have led us to a more complex understanding that suggests dreaming could play a role in memory, learning and emotions. Rats, for example, have been shown to replay their waking experiences in dreams, apparently helping them to solve complex tasks such as navigating mazes.

7 Why is there stuff?

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You really shouldn’t be here. The “stuff” you’re made of is matter, which has a counterpart called antimatter differing only in electrical charge. When they meet, both disappear in a flash of energy. Our best theories suggest that the big bang created equal amounts of the two, meaning all matter should have since encountered its antimatter counterpart, scuppering them both and leaving the universe awash with only energy. Clearly nature has a subtle bias for matter otherwise you wouldn’t exist. Researchers are sifting data from experiments like the Large Hadron Collider trying to understand why, with supersymmetry and neutrinos the two leading contenders.

8 Are there other universes?

Our universe is a very unlikely place. Alter some of its settings even slightly and life as we know it becomes impossible. In an attempt to unravel this “fine-tuning” problem, physicists are increasingly turning to the notion of other universes. If there is an infinite number of them in a “multiverse” then every combination of settings would be played out somewhere and, of course, you find yourself in the universe where you are able to exist. It may sound crazy, but evidence from cosmology and quantum physics is pointing in that direction.

9 Where do we put all the carbon?

For the past couple of hundred years, we’ve been filling the atmosphere with carbon dioxide – unleashing it by burning fossil fuels that once locked away carbon below the Earth’s surface. Now we have to put all that carbon back, or risk the consequences of a warming climate. But how do we do it? One idea is to bury it in old oil and gas fields. Another is to hide it away at the bottom of the sea. But we don’t know how long it will stay there, or what the risks might be. Meanwhile, we have to protect natural, long-lasting stores of carbon, such as forests and peat bogs, and start making energy in a way that doesn’t belch out even more.

10 How do we get more energy from the sun?

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Dwindling supplies of fossil fuels mean we’re in need of a new way to power our planet. Our nearest star offers more than one possible solution. We’re already harnessing the sun’s energy to produce solar power. Another idea is to use the energy in sunlight to split water into its component parts: oxygen, and hydrogen, which could provide a clean fuel for cars of the future. Scientists are also working on an energy solution that depends on recreating the processes going on inside stars themselves – they’re building a nuclear fusion machine. The hope is that these solutions can meet our energy needs.

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