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Wednesday, 5 February 2020

What is reality

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What is Reality
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This is one of two interesting articles on Reality published in the New Scientist of February 1st. I (there is no I anyway) consider Reality to be an illusion created by people (sathva in general) .

What is reality? Why we still don't understand the world's true nature

It’s the ultimate scientific quest – to understand everything that there is. But the closer we get, the further away it seems. Can we ever get to grips with the true nature of reality?

Physics 29 January 2020

Chess pieces


We humans have a bit of a problem with reality. We experience it all the time, but struggle to define it, let alone understand it.

It seems so solid and yet, when we examine it closely, it melts away like a mirage. We don’t know when it began, how big it is, where it came from and where it is going, and we certainly have no clue why it exists.

Nonetheless, the desire to understand reality seems part of our nature, and we have come a long way. What was once explained in terms of divine creation is now in the purview of science. Over the past 200 years or so, we have peeled back the layers of reality, even if we are still not entirely sure what we have revealed. 

If anything, the mystery has only deepened. We are now at a point where it is equally credible to claim that reality is entirely dependent on subjective experience, or entirely independent of it. Reality has never felt so unreal.

Lets delve into the latest ideas about reality, from our own everyday experience to the fundamental physics that seeks to describe the true nature of the cosmos. The ideas can be dizzying, but there is no greater intellectual challenge than trying to grasp the meaning of everything.

What is reality anyway?

IT IS a big and bewildering concept, reality. An abstract way of saying “everything that there is”. That is a lot to take in: space, time, matter, energy, forces, consciousness, even abstract ideas. How to even start?

Nobel-prizewinning physicist Richard Feynman once described the quest to understand reality as a bit like watching a game of chess without knowing the rules. By observing the game, we slowly get to grips with what the pieces are and how they are allowed to move and interact.

By roughly the middle of the 20th century, physicists thought they had at least identified the fundamentals of the game: particles and quantum fields. The particles made up the matter and energy around us, and the quantum fields were responsible for forces, like electromagnetism, which governed how they interact. The rules of the game were set by quantum theory.

This standard model has broadly stood the test of time. The discovery of its final missing piece, the Higgs boson, was confirmation that it is at least on the right track.

And it arguably fulfils at least one philosophical definition of reality: what exists and what does it do? According to philosopher of science Tim Maudlin of New York University, if you have answered both these questions, then you have essentially cracked the problem of reality.

But the standard model is nowhere near a complete answer. It leaves out many things that physicists are pretty sure are real even if they have yet to be characterised, including dark matter and dark energy. And it can’t account for the force that substantially defines our experience of reality, gravity. 

Despite high hopes that the Large Hadron Collider would follow the discovery of the Higgs with at least some hints about a more complete theory, none has yet been forthcoming.

It isn’t that we don’t understand gravity. General relativity elegantly paints it as a consequence of the deformation of the fabric of space-time. The problem is that quantum theory and general relativity don’t play by the same rules. If one is chess, the other is backgammon. Quantum theory is predicated on reality existing in tiny, indivisible chunks, relativity on it being smooth and continuous. This means we can’t understand situations where both gravity and quantum theory are in play, such as in black holes, the big bang, or tiny particles in gravitational fields.

The most pressing challenge for the study of reality today, then, is to find a way of unifying quantum theory and relativity in one game. “Each of these pieces is contradicted by the other,” says Carlo Rovelli at Aix-Marseille University in France. “So what’s needed is more than sticking the pieces together. We are searching for a coherent way of thinking in light of what we know.”

“If you want a theory of everything where it all fits, I see no hint that we’re close – zero”

There are options on the table, not least the one Rovelli has pioneered, loop quantum gravity, which holds that space-time isn’t smooth but made of tiny loops. There is also the old stalwart, string theory. This says all particles and forces are points on one-dimensional strings that extend through seven or more invisible extra dimensions. Both loop quantum gravity and string theory purport to solve some of the incompatibilities between explanations of gravity and quantum effects, but both also have their problems. String theory in particular can lead to some pretty outlandish interpretations of reality, such as multiverses (see “Is reality the same everywhere?”) and the “holographic principle”, which holds that three-dimensional space is actually a kind of projection onto a two-dimensional surface.

Where to find answers?

A more recent avenue being explored by theoretical physicists is entanglement, a quantum phenomenon whereby two particles can influence one another even when they are separated by huge distances. This approach has recently shown that entanglement can define the geometry of space: the stronger the entanglement, the more warped space is. Some physicists suggest this means that space-time emerges from quantum mechanics. In which case, quantum theory is the more fundamental description of reality, and should be where we find answers to the questions of what exists and what it does.

A successful unification of quantum theory and relativity would still be glaringly incomplete, however, unless it also straightens out another must-have feature of reality: time. In general relativity, time is central. Quantum theory near enough ignores it. Neither can provide an explanation for why time always appears to tick in one direction.

It may be that time isn’t a fundamental ingredient of reality at all, but what physicists call an emergent phenomenon. One way to think about this is to imagine warming your hands by a fire. Energetic molecules in the air are bouncing against your skin, warming it up. But we don’t need to explain what’s happening in terms of the particles: a rise in temperature adequately captures the phenomenon. Temperature is a perfectly good way of thinking about an aspect of reality as long as we don’t assume that it is a fundamental thing. The same may apply to time, says theoretical physicist Claudia de Rham of Imperial College London.

This way of thinking may even lead to an entirely different perspective on reality. Perhaps the reductionist approach, of drilling down ever deeper to seek even more fundamental layers, has hit a limit. Some physicists say we need to stop fixating on the elusive “true” nature of reality and focus on building a set of models that describe the various physical phenomena we observe.

“What we do is modelling,” says de Rham. “Our way to interpret what’s going on doesn’t necessarily need to be what in reality happens.”

One seldom considered question, however, is how exactly models ought to seek to explain reality. Some, such as general relativity, take some known quantities about nature – the position of a planet, say – and predict what will happen next. Quantum theory takes a different philosophical approach, assigning probabilities to future outcomes we might see.

But these aren’t the only methods of explaining reality. Consider a much older branch of physics: thermodynamics, the science of heat, work and power. It doesn’t seek to describe the fundamental nature of things, but instead rules what can and cannot happen. For example, it tells us that a scrambled egg cannot be unscrambled and that energy cannot be created or destroyed.

Some physicists are now exploring whether a similar approach can help us make headway. For example, constructor theory starts from the idea that the essence of reality is information, and then sets out what kinds of things are possible and impossible. It is early days, but it has already made predictions in circumstances that defeat other theories, such as the behaviour of quantum particles in a gravitational field.

The next level

Where does that leave us? Our understanding of the game is in a state of flux, but we are making progress, even if it isn’t exactly what we hoped for. “If the question is, do we have a chance to see the next clear level of understanding, then, yeah, I think we can get it,” says Rovelli. Even this is unlikely to be the last word, however. Rovelli thinks it will just reveal more holes in our understanding. “If you want a theory of everything where it all fits, I see no hint that we’re close – zero,” he says.

It isn’t even clear that our brains are actually capable of comprehending reality (see “Can we perceive reality?”). Chimpanzees are intelligent but could never grasp quantum theory, or see why it is necessary. Similarly, there may be some fundamental limit to human cognition that prevents us from getting the big picture – though maybe superintelligent machines could one day do so.

From a human perspective, a more fundamental description of reality only promises to shift the true nature of reality yet further from our everyday experiences of it – quite a feat, given the extent to which quantum theory and relativity have already done so. “When I wake up in the morning, for sure, that’s my reality,” says de Rham. “But there is definitely something more fundamental that I will never be able to experience.” For all our efforts to pin it down, reality just keeps on getting bigger and more bewildering.


How did reality get started?

Even though we don’t fully understand what reality is – and may never do so – that doesn’t stop us from asking where it came from. It will come as no surprise that answering this question is far from easy. Just ask the people whose day job it is. They don’t agree on much, except that it is a tough gig. “We are in a difficult situation,” says Daniele Oriti at the Max Planck Institute for Gravitational Physics in Germany. “We are fishes in the pond and trying to infer the situation of our pond.”

The conventional origin story of the pond is the big bang. In this account, the universe simply popped into existence out of nothingness 13.8 billion years ago, triggering an expansion that has continued without pause ever since. It is a picture that aligns well with the available evidence – such as the ongoing expansion of the universe – but hasn’t yet been definitively accepted.

Perhaps that is no surprise given the unfathomable core of the big bang theory: how nothingness can give rise to an entire universe. Another major stumbling block is the moment just after the universe popped into existence, when its entirety would have been concentrated into a point of infinite density and temperature. “We do not have any theory that describes the universe at ultra-high temperatures and ultra-high densities,” says Anna Ijjas, also at the Max Planck Institute for Gravitational Physics. That means our knowledge of these first few instants remains fundamentally incomplete.

Better theories might yet fill these gaps. Or they might render them obsolete by showing that there was no beginning for space and time. That is the explanation Ijjas favours. She says that our universe’s beginning coincided with a previous universe’s end. Think of it as an hourglass, with two halves connected by an incredibly narrow neck. In this model, the universe would once have had a radius of 10-25 centimetres, more than a billion times smaller than the radius of an electron. That is vanishingly small, but infinitely bigger than the nothingness required for the big bang.

This hourglass model is known as the big bounce, and it has dramatic consequences for reality. Because theoretical calculations dictate that the preceding universe must have been similar to our own, its origin must also be similar. That means it, too, would have begun from the collapse of a preceding universe, and so on throughout eternity. “In our model, space-time never vanishes,” says Ijjas. In other words, reality has always existed and there was no beginning.

That seems difficult to imagine. “It’s somewhat counter-intuitive,” concedes Ijjas. But the alternative – the total absence of reality before space and time came into existence – is more difficult. “It’s infinitely more difficult,” she says.

What came before?

Oriti favours another alternative. For him, the big bang represents not the birth of the universe, but the moment the universe assumed its current form, with intelligible properties such as space and time. He compares it to a phase transition such as the moment steam condenses to liquid water. “All sorts of notions that you apply as a fish in the water simply do not apply to a gas,” he says.

Before this phase transition, notions of space and time are meaningless, and reality itself becomes fundamentally indescribable. Even the word “before” is inaccurate, says Oriti. “The notion of time ceases to apply.” What’s more, because all phase transitions are, at least in theory, reversible, the universe could return to this timeless state again at some point in the future, presumably with dire consequences for us. If “future” is even the right word.

This inability to talk about reality in everyday terms seems incredibly frustrating. “We get frustrated as well,” says Oriti. “I sympathise, but get used to it.” Reality, it seems, is truly beyond words.

Reality Artwork

Is reality the same everywhere?

TRAVEL anywhere in the known universe and, like Coca-Cola, the laws of nature always taste the same. That is a basic tenet of physics called the cosmological principle, which holds that our patch of the universe is a representative sample of the rest.

This, as far as we can tell, is true. Certainly in the bits of the universe that we can see, the laws of physics are “uncannily the same”, says Richard Bower at Durham University in the UK. But an important caveat here is “the bits we can see”. What about those we can’t?

There are bits of the universe that are out of sight. Forever. These aren’t the exotic parallel universes conjured up by string theory or quantum mechanics, but an unavoidable consequence of workaday cosmology. Because the universe is expanding at breakneck speed yet the speed of light is finite, the outer reaches of the universe have disappeared over the cosmic horizon, forever out of contact as light from them could never reach us. The known universe inside the horizon stretches about 46 billion light years in all directions. How much there is beyond that isn’t known, but it is possible that there are places beyond the horizon where the laws of physics are different.

One reason for thinking this may be true is that our laws are bizarrely and arbitrarily conducive to life. Cosmologists call this fine-tuning. If any of the laws of physics were slightly different, we couldn’t exist. As just one example, if the strong nuclear force, which holds protons and neutrons together inside atoms, were slightly stronger, the sun would have exploded long before life got started on Earth. There are many other examples of fine-tuning, collectively known as the “Goldilocks paradox” because so many of the laws are just right. And paradoxical it is. “There’s no explanation for why they are the value they are,” says Bower. “You’ve just got to go, ‘That’s the way it is’.”

The odds of a universe with the exact specifications that can sustain life are so low that many physicists argue that there must be other places where the laws are different. It just so happens that we live in a life-friendly patch of universe because, well, it couldn’t be any other way.

And that’s just in our universe. There are almost certainly others. Multiverses are a consequence of many theories, including black hole physics and string theory. Not all produce different laws of physics, but some do. String theory, for instance, conjures up 10500 universes, all with different laws of physics.

Could we ever know if any of this is true? The reality is that other universes, if they exist, are probably forever inaccessible to us. “Multiverse theories must in principle be taken quite seriously, but proposals to test them don’t get very far,” says Simon Friederich at the University of Groningen in the Netherlands.

For now, we have to study what we can see. But there is an upside to this: it makes reality tractable. “If there is just one universe, then we might have a good chance of discovering basically everything about physics,” says Tim Blackwell at Goldsmiths, University of London. Unfortunately, that would be like assuming you understood all of biodiversity by cataloguing life on a small island. Reality may well be different elsewhere, but the cosmos is too big for us to know for sure.

Join six expert speakers for a mind-melting trip through the science of reality at our live event in London on 28 March

  1. New coronavirus may be much more contagious than initially thought
  2. What are the symptoms of the new coronavirus and how deadly is it?
  3. Can an N95 face mask protect you from catching the new coronavirus?
  4. One in 16 US women were forced into having sex for the first time
  5. Albatrosses strapped with sensors help spy on illegal fishing boats
  1. Watch this fish hop across the surface of water and climb on land
  2. We can’t let Boris Johnson politicise crucial COP26 climate talks
  3. Will the coronavirus become a pandemic - and what happens if it does?
  4. We need nuclear power to fight climate change, but is it doomed?
  5. Who invented the alphabet? The untold story of a linguistic revolution
  1. The genetic revolution: Can we predict school performance from DNA?
  2. How to be superhuman: The science behind extraordinary abilities
  3. When will we hear from aliens? We may already have done so
  4. The problem with plastic - and how science can solve it
  5. How I made the world’s most accurate thermometer – using sound
  1. We can’t let Boris Johnson politicise crucial COP26 climate talks
  2. California has huge environmental inequality – here's how to fix it
  3. Art prints made using rain, fog and snow reveal the nature of water
  4. Tackling air pollution may accidentally trigger serious health issues
  5. Legal action could be used to stop Starlink affecting telescope images

Magazine issue 3267 , published 1 February 2020