Dark-Universe-Transcript.pdf - Dark Universe Transcript...

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1Dark Universe TranscriptNeil deGrasse Tyson (Frederick P. Rose Director, HaydenPlanetarium):Way out here, ten million light years from planet Earth, every pointof light is a galaxy containing billions of stars.And yet we’ve managed to map the visible universe well enoughto chart an accurate course all the way back home.Just within the last hundred years, we humans, inhabitants of asmall planet orbiting this unexceptional star, have learned wherethe galaxies are, what they’re made of, and how they got to bethat way.We’ve discovered that the universe was born in fire—13.8 billionyears ago—and that it’s been expanding and evolving ever since.But with new instruments on Earthand in space, we’ve begun toglimpse how much we stilldon’tknow about the cosmos.
2This is Neil deGrasse Tyson, and I’m here to guide you through acentury of discovery about the past, present, and future of ouruniverse.Our story begins in the nineteen twenties, when astronomersusing what was then the world’s largest telescope—on MountWilson, near Los Angelesbegan piecing together our place inthe cosmos.The astronomers knew that we live in a disk-shaped galaxy calledthe Milky Way, and that the band of light, arching across the sky,is our view of that galaxy from our location inside it.But their observations hadn’t yet revealed whether anyothergalaxies existed.That changed when the astronomers aimed their telescope at afuzzy patch of light in the constellation Andromeda.There, the astronomers identified pulsating stars like those inourgalaxy. By measuring the stars’ distances, they found a galaxy inits own right, far outside the Milky Way.
3The Andromeda Galaxy is more than two million light years fromusso we see it as it looked more than two million years ago,long before humans first walked the Earth.As they probed deeper and located manymoregalaxies, theastronomers were startled to see that the light from distantgalaxies was always stretched out to longer, redder wavelengths,signifying thatthey’re all moving away from us.They found that the moredistanta galaxy, thefasterit’s moving.Cosmic space is constantly stretching, carrying the galaxies withit.But there’s no center to the universe: An observer inthisgalaxywould see the same evidence of cosmic expansion as we do.So would observers in that onethere.Wherever you are, it looksas if you’re at the center and everyoneelse is speeding away.

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