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  • Sometimes when I'm on a long plane flight,

  • I gaze out at all those mountains and deserts

  • and try to get my head around how vast our Earth is.

  • And then I remember that there's an object we see every day

  • that would literally fit one million Earths inside it.

  • The sun seems impossibly big,

  • but in the great scheme of things, it's a pinprick,

  • one of about 400 billion stars in the Milky Way galaxy,

  • which you can see on a clear night as a pale, white mist stretched across the sky.

  • And it gets worse.

  • There are maybe 100 billion galaxies detectable by our telescopes,

  • so if each star was the size of a single grain of sand,

  • just the Milky Way has enough stars to fill

  • a 30 foot by 30 foot stretch of beach three feet deep with sand.

  • And the entire Earth doesn't have enough beaches

  • to represent the stars in the overall universe.

  • Such a beach would continue for literally hundreds of millions of miles.

  • Holy Stephen Hawking, that is a lot of stars.

  • But he and other physicists now believe in

  • a reality that is unimaginably bigger still.

  • First of all, the 100 billion galaxies within range of our telescopes

  • are probably a minuscule fraction of the total.

  • Space itself is expanding

  • at an accelerating pace. The vast majority of the galaxies

  • are separating from us so fast

  • that light from them may never reach us.

  • Still, our physical reality here on Earth

  • is intimately connected to those distant, invisible galaxies.

  • We can think of them as part of our universe.

  • They make up a single, giant edifice,

  • obeying the same physical laws and all made from the same types of atoms, electrons,

  • protons, quarks, neutrinos that make up you and me.

  • However, recent theories in physics,

  • including one called string theory,

  • are now telling us there could be countless other universes,

  • built on different types of particles,

  • with different properties, obeying different laws.

  • Most of these universes could never support life,

  • and might flash in and out of existence in a nanosecond,

  • but nonetheless, combined

  • they make up a vast multiverse of possible universes.

  • in up to 11 dimensions, featuring wonders beyond our wildest imagination.

  • And the leading version of string theory

  • predicts a multiverse made of up to 10 to the 500 universes.

  • That's a one followed by 500 zeroes,

  • a number so vast that if every atom in our observable universe

  • had its own universe

  • and all of the atoms in all of those universes

  • each had their own universe,

  • and you repeated that for two more cycles,

  • you'd still be at a tiny fraction of the total --

  • namely, one trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillionth.

  • But even that number is minuscule compared to

  • another number: infinity.

  • Some physicists think the space-time continuum

  • is literally infinite, and that it contains an infinite number

  • of so-called pocket universes with varying properties.

  • How's your brain doing?

  • But quantum theory adds a whole new wrinkle.

  • I mean, the theory's been proven true beyond all doubt,

  • but interpreting it is baffling.

  • And some physicists think you can only un-baffle it

  • if you imagine that huge numbers of parallel universes

  • are being spawned every moment,

  • and many of these universes would actually be very like the world we're in,

  • would include multiple copies of you.

  • In one such universe, you'd graduate with honors and marry the person of your dreams.

  • In another, not so much.

  • There are still some scientists who would say, hogwash.

  • The only meaningful answer to the question of how many universes there are is one,

  • only one universe.

  • And a few philosophers and mystics

  • might argue that even our own universe is an illusion.

  • So, as you can see,

  • right now there is no agreement on this question,

  • not even close.

  • All we know is, the answer is somewhere between zero and infinity.

  • Well, I guess we know one other thing:

  • This is a pretty cool time to be studying physics.

  • We just might be undergoing

  • the biggest paradigm shift in knowledge that humanity has ever seen.

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B2 TED-Ed universe vast theory minuscule multiverse

【TED-Ed】How many universes are there? - Chris Anderson

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    VoiceTube posted on 2013/03/20
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