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  • For as long as humans have looked at the stars,

  • we have wondered how they got there -

  • and what lies beyond them.

  • Scientists have long searched for a simple theory

  • that explains how the universe works,

  • a theory of everything.

  • Many theories have been tested

  • and so far, every one of them has failed to fully explain

  • what we see in our universe.

  • But there is one particularly enticing idea

  • that some theoretical physicists think might just be 'it',

  • String Theory.

  • String theory is finite.

  • It doesn't blow up.

  • It doesn't collapse on itself.

  • That's why we believe in it.

  • Other theories do collapse. Other theories do blow up.

  • But string theory does not.

  • Dr Michio Kaku has spent decades

  • grappling with - and attempting to answer -

  • some of life's biggest questions.

  • What happened before the Big Bang?

  • Are there other universes?

  • What lies on the other side of creation?

  • The other side of a black hole?

  • Are gateways possible?

  • Wormholes? Higher dimensions?

  • Do we live in a multiverse?

  • All these questions cannot be answered

  • using our present-day understanding.

  • When Dr Kaku talks about our present-day understanding,

  • he means our current best theories about the way the universe works.

  • In truth, they contradict each other.

  • And sometimes even give conflicting results -

  • Albert Einstein's general theory of relativity works perfectly well

  • for predictions about the movements of stars and galaxies,

  • but doesn't work when applied to the behaviour of subatomic particles.

  • Conversely, quantum theory is great with atoms

  • but predicts the whole universe should collapse into a black hole,

  • which it clearly doesn't because we're all still here!

  • So, will we ever find a single theory that explains everything?

  • Two thousand years ago, Pythagoras asked himself that question.

  • The great Greek mathematician

  • said that there must be a unifying principle,

  • a paradigm by which to summarise the vast creation

  • that we see all around us of the universe that we know.

  • And he looked around and saw a lyra string.

  • You pluck a lyra string and you get a note,

  • you pluck another one, you get another note.

  • And then he said, aha, the mathematics of music is rich enough

  • to explain the diversity of everything we see around us.

  • And only recently have we come up with a new idea

  • based on the Pythagorean idea of music.

  • In other words, string theory.

  • So how do we go from Pythagoras' musical musings to proper physics?

  • The first port of call would be a particle accelerator

  • like the Large Hadron Collider at CERN in Switzerland,

  • where tiny particles are smashed to pieces in high energy collisions

  • and then closely studied.

  • These experiments are our best way of testing theories

  • about how the universe works.

  • So what does string theory predict we would see?

  • We now believe that all these subatomic particles,

  • hundreds of subatomic particles

  • that we get by smashing protons at the Large Hadron Collider,

  • they're nothing but musical notes as Pythagoras believed.

  • If I had a super microscope

  • and I could peer into an electron,

  • what would I see?

  • I would see a rubber band,

  • a vibrating rubber band.

  • Of course, Dr Kaku doesn't mean an actual rubber band.

  • But rather something rubber-band-like.

  • Or to put it another way - the strings in string theory.

  • And just like the strings on a musical instrument,

  • if you put some energy into them, they vibrate.

  • It vibrates one way, we call it an electron.

  • We vibrate it another way, it's called a neutrino.

  • We vibrate it another way, it's called a quark.

  • But it's the same rubber band.

  • So, string theory offers a tantalising possibility -

  • an explanation for the vast variety we see in the universe,

  • from the collisions of stars to the collisions of atoms.

  • Of course, string theory is just that - a theory.

  • Its critics point out that many of its predictions are untestable -

  • something Dr Kaku himself acknowledges.

  • Its proponents though, consider it to be

  • the best hope of unifying physics.

  • Dr Kaku believes string theory

  • could even explain the mystery that is dark matter.

  • Dark matter makes up most of the matter of the universe.

  • It is invisible and it holds the galaxies together,

  • but how do we prove it?

  • We think that dark matter could be the next octave of the string.

  • If you could magnify all the particles you see around us,

  • we would see a lot of rubber bands,

  • a lot of rubber bands vibrating at different frequencies.

  • But the rubber band has higher octaves.

  • That, we think, is dark matter.

  • If Dr Kaku is right, the huge complexity of the entire universe

  • could be reduced to the simple and elegant vibration of strings.

  • I think the one thing that people should realise

  • is that physics, at the fundamental level,

  • gets simpler and simpler the deeper we go,

  • but becomes more powerful, the deeper we go.

  • The universe is simpler than we thought.

For as long as humans have looked at the stars,

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String theory - a simple way to understand the universe | BBC Ideas

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    Summer posted on 2021/10/07
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