What’s in it for me? A possible theory of everything
String theory is one of the most complex and puzzling ideas in modern physics.
It’s intriguing, but hard for most of us to grasp.
Here, however, you’ll find a summary of string theory that’s easy to follow.
The author of Hyperspace, Michio Kaku, is a professor of theoretical physics, renowned for making the subject more accessible.
In this Blink, we’ll be exploring the possibility of additional dimensions beyond our familiar three-dimensional world.
According to one theory, there may be a fifth dimension, while string theory posits the existence of ten dimensions.
These hidden dimensions could hold the key to unifying the forces of nature, and may explain the very fabric of reality.
Hyperspace invites us to consider a universe far more intricate and fascinating than we ever imagined.
How many dimensions are there?
We tend to think of the universe as being three-dimensional.
Welcome to hyperspace
There are three spatial dimensions – length, width, and breadth.
Counting time as a dimension, there are four in total.
However, some theoretical physicists believe there may actually be ten dimensions.
That might sound incredible – impossible to imagine, let alone believe.
And indeed, for many years, the notion of higher dimensions seemed to be the stuff of science fiction.
But these days, many physicists are intrigued by the theory of hyperspace.
Put simply, even if we aren’t yet able to perceive them, other dimensions probably exist.
But you’re probably wondering why physicists are looking for additional dimensions in the first place.
Aren’t three or four enough?
Well, not really.
Many scientists believe that the known dimensions aren’t enough to adequately describe the forces in our universe.
The laws of nature, such as light and gravity, are expressed with greater simplicity and elegance in higher dimensions – their natural element.
Here’s a helpful analogy.
Imagine a cheetah – a sleek, elegant animal that can run at incredible speeds.
In its natural habitat – the African savannah – it’s a truly magnificent creature.
Now, imagine that cheetah in a cage.
In this setting, it may now seem less awe-inspiring, and even rather sad – it’s reduced, somehow.
The cheetah is like the laws of physics – impressive in its natural habitat, but much less so in a different setting.
At the moment, we’re only capable of measuring the laws of physics in three dimensions.
But ideally, we should be examining these laws in their full glory, in their natural habitat – higher-dimensional space-time, or hyperspace.
For many physicists, the idea of hyperspace is thrilling.
It opens up all kinds of possibilities, some of which we’ll explore shortly.
Significantly, hyperspace could also resolve the key challenge of theoretical physics – the quest for unification.
Everything in our universe can be reduced to four forces – the electromagnetic, the strong nuclear, the weak nuclear, and the gravitational force.
The problem is, these forces seem completely dissimilar, or even fragmented.
Starting with Einstein, some of the greatest geniuses of physics have looked for something that would unify the four forces – something to bring them all together.
Could hyperspace be the answer?
A theory that would explain all the forces in nature, light and gravity included … that was Einstein’s dream.
The Kaluza-Klein theory
But frustratingly, for all his attempts, he just couldn’t find a theory that worked.
In 1919, however, Einstein received a letter from an obscure mathematician named Theodor Kaluza.
Kaluza had a solution – something that combined Einstein’s theory of gravity and Maxwell’s theory of light.
The solution was simple and elegant.
Kaluza showed that Einstein’s field equations for gravity could be expressed in five dimensions, rather than the usual four.
Then he showed how these equations contained Einstein’s four-dimensional theory, plus an additional piece.
Amazingly, this additional piece was Maxwell’s theory of light.
It seemed like Kaluza was using a brilliant mathematical trick to put together the pieces of the puzzle.
Still, although Einstein was impressed, he wasn’t completely convinced by the idea of the fifth dimension.
And once Kaluza’s idea went public, other physicists were skeptical, too.
First, the obvious question: Where was the fifth dimension?
All the evidence was for a universe of just four dimensions.
True, said Kaluza.
The fifth dimension cannot be observed by experiment.
For a start, it’s different from other physical dimensions – it’s curled up in the shape of a circle.
Because of this shape, according to the rules of physics, anyone who moved toward the fifth dimension would end up back where they started.
And because the fifth dimension is so incredibly miniscule – a size known as the Planck length – its existence can’t be tested scientifically.
We don’t have machines powerful enough to prove the theory.
It would require more than a thousand billion electron volts – an unfathomable amount of energy.
Kaluza’s theory, which later came to be known as the Kaluza-Klein theory, was appealing in many ways.
But unfortunately, it was impossible to prove.
By the 1930s, many physicists had lost interest, and were turning their attention to an exciting new theory known as quantum mechanics.
And for a while, the Kaluza-Klein theory and the fifth dimension were all but forgotten.
By the 1980s, scientists were becoming frustrated by their unsuccessful attempts to unify gravity with quantum forces.
Perhaps, they thought, the Kaluza-Klein theory might be helpful after all.
String theory
A new iteration of the theory, known as supergravity, began to cause some excitement.
Essentially, it was an abstract equation that seemed to unify everything.
Unfortunately though, it was flawed.
When physicists tried to calculate numbers using the theories of supergravity, they came up with infinities – meaningless numbers.
Supergravity wasn’t the ultimate solution physicists had been looking for, but more of a stepping stone in the right direction.
Then, another exciting new theory emerged – string theory.
This theory originated from the research of Gabriel Veneziano and Mahiko Suzuki in 1968.
But it was only in the ‘80s that string theory really began to take off, with contributions from physicists like Edward Witten.
Many of us have heard of string theory, but don’t quite understand it.
So let’s break it down.
String theory changes the way we look at particles.
According to the theory, if we could magnify particles sufficiently, we wouldn’t find a point.
Instead, we would find a tiny loop of vibrating string.
Think of a violin string, which can vibrate at countless different frequencies.
If particles are also formed of strings, that explains the infinite forms of matter in the universe – the infinite variety.
So the universe is made up of all these tiny vibrating strings.
You could compare it to a symphony.
Another interesting thing about string theory is that it explains not just particles, but the nature of space-time.
The movements of strings, known as quantum corrections or loop diagrams, are finite, and they can be calculated.
That wasn’t the case for other quantum theories of gravity, such as Kaluza-Klein.
What makes string theory so important is that it brings everything together.
Einstein’s equations can be derived from string theory.
And other theories can be extracted, too – Kaluza-Klein, supergravity, the Standard Model, and the Grand Unified Theory, or GUT.
So, string theory seems to be the missing link.
It incorporates both the theory of relativity and quantum mechanics.
And it could, some physicists believe, be that elusive “theory of everything.
” Now, remember Kaluza-Klein and the fifth dimension?
With string theory, we have not just five dimensions but ten.
In order for the theory to work – for the math to work – the dimensions of space-time have to be fixed at this very specific number.
Why?
Well, we don’t quite know.
Physicists are at a loss to explain it.
When they delve into the mathematics of string theory, they keep encountering unusual modular functions.
And for some reason, the number ten keeps popping up.
For all its potential, there are still a lot of unknowns in string theory.
This is part of what makes it so fascinating – but, inevitably, it’s also led to criticism.
Problems with string theory
There are two main issues with string theory.
One is that at the moment, no one is capable of solving it.
String theorists argue that the fault lies not with the theory, but rather with our primitive mathematics.
The main tool used for calculations – a method called perturbation theory – provides answers.
But it provides too many answers – millions and millions of them.
Physicists need to identify the one that accurately describes our universe, and they haven’t been able to find it yet.
Imagine a nineteenth century physicist being given a laptop.
They could learn how to use it.
But if they opened it up and looked at all the transistors and microprocessors, they’d be stumped … and more than a little frustrated.
That’s what it’s like for physicists at the moment.
They’re waiting for mathematics to evolve, and hoping that one day we’ll be smart enough to understand string theory properly.
Another major problem – and a reason why string theory is often criticized – is that currently, it can’t be tested.
To test string theory, we’d need to be able to generate an extraordinary amount of energy – an amount that’s one quadrillion times larger than what’s currently available.
Simply put, we don’t have the technology, and we don’t have the money.
In the words of one physicist, David Gross, “There is not enough money in the treasuries of all the countries in the world put together.
” In the early ‘90s, there was a proposal to build a particle accelerator known as a Superconducting Super Collider, or SSC.
This technology might have provided some answers for string theorists.
However, the SSC was expected to cost $11 billion, and after political opposition, the project was canceled.
Another potential way to test string theory would be to measure the energy of cosmic rays.
But unfortunately, even the most powerful cosmic ray detected on Earth wasn’t nearly powerful enough.
It was 100 million times smaller than the energy required to test string theory.
As well, cosmic rays are unpredictable and challenging to detect.
Nonetheless, string theory experts remain optimistic.
We don’t know exactly what the future holds.
One day, perhaps our civilization will be capable of generating incredible energies – trillions of times larger than we’re currently able to produce.
Of course, we’re in for a long wait.
In the meantime, though, who knows?
Perhaps we’ll receive a signal from the tenth dimension – communication from extraterrestrial civilizations that have learned how to manipulate hyperspace.
It may seem like we’re now entering the realms of science fiction.
But remember: string theory isn’t fiction – it’s based in theoretical physics and mathematics.
So let’s keep an open mind, and allow ourselves to consider the possibilities as we head into outer space.
When we think of space in multi-dimensional terms, black holes become truly intriguing – potential gateways to other universes.
Wormholes
Now, before we get ahead of ourselves, let’s take a moment to define black holes.
They’re sometimes formed during the last stage in the death of a collapsed star.
When the nuclear fuel of the star is exhausted, the powerful force of gravity causes it to collapse.
The star then becomes so dense that light is unable to escape from its gravitational field.
It’s now a black hole.
Now, Michio Kaku says that, according to the Einsteinian perspective, a light beam that enters a black hole can be bent into a full circle.
And that’s only possible if space itself has also been bent into a full circle.
So that means a piece of space-time has become disconnected from the surrounding space-time.
There’s a rip.
Let’s say you fell into a black hole, and somehow survived.
Theoretically, you would be aware of a “mirror universe,” which exists on the other side of space-time.
But because of various factors – such as the crushing force of an infinite gravitational field – you wouldn’t be able to access this mirror universe.
Still, according to the physicist Karl Schwarzchild, the mathematical theory of black holes means that the mirror universe has to exist.
And so does a bridge between the two universes.
They’re connected by something known as the Einstein-Rosen bridge.
For decades, this idea was more or less ignored.
If it was impossible to reach the mirror universe, did the bridge matter?
But in the 1960s, the mathematician Roy Kerr found an alternative solution for Einstein’s equations.
According to Kerr, a collapsing star would not be stationary, but spinning, and thus accelerating.
This would give a space probe a chance at survival.
Theoretically, it could pass safely through the spinning black hole by traveling along its axis of rotation, and reach the mirror universe on the other side.
So essentially, the Einstein-Rosen bridge could become a kind of tunnel, connecting two different parts of space-time.
It’s a wormhole – or a gateway to another universe.
And in theory, if wormholes exist, we could build a time machine.
Parallel universes may exist, too.
Perhaps our universe is just one of an infinite number.
Imagine all these parallel universes, like billions of bubbles floating in the air.
Although they’re separate from each other, perhaps they could be connected to each other via wormholes.
Of course, it’s important to remember that we’re still just speculating.
Wormholes, the feasibility of constructing time machines, and the existence of parallel universes haven't yet been proven.
But they're no longer such far-fetched ideas.
They’re things scientists are taking seriously.
String theory and hyperspace have opened up an exciting new world of possibilities.
Or rather, new dimensions, and even new universes.
Final summary
In this Blink to Hyperspace by Michio Kaku, you’ve learned that the universe is commonly thought of as having four dimensions: three of space, and one of time.
However, according to string theory, there may actually be ten dimensions.
These higher dimensions could offer a more elegant understanding of the universe, unifying all the forces of nature.
Some hope that string theory could prove to be the much sought-after “theory of everything.
” String theory hasn’t yet been solved, because it requires an extremely advanced understanding of mathematics.
It also hasn’t been tested, because experiments would require incredible amounts of energy – far beyond our current capabilities.
Nonetheless, some physicists believe that string theory could unlock new understanding of the universe.
Wormholes, time travel, and parallel universes are all possible – not just the stuff of science fiction.
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