WEBVTT

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How is gravity like
nature's magnifying glass?

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To find out what the universe
was like in the beginning,

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we need to study the
most distant galaxies

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whose light has been traveling
to us for billions of years.

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But the farther away a galaxy
is, the fainter it appears.

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That makes distant
galaxies very hard

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to see, even for the
most powerful telescopes

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because they can only
collect so much light.

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Fortunately, nature can
provide a helping hand.

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According to Einstein, the
gravity of massive objects

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can be so intense that it can
warp the fabric of space time.

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Light which normally travels in
a straight line through space

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can show us where this
distortion occurs.

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A very massive object
will warp space and bend

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to the path of the light.

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In a sense, warp space acts
like a magnifying glass.

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A magnifying glass collects and
bends light, making light bulb,

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for example, appear
bigger and brighter.

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Warped space can do the same
thing to light from a galaxy.

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So what acts like the biggest
magnifying glass in space?

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Galaxy clusters are
the most massive things

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in the universe with
the most gravity.

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When light from a
very distant galaxy

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passes through a cluster, it
is amplified and distorted

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with the cluster acting like
an imperfect magnifying glass.

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Light that would have gone.

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In other directions gets
bent toward our telescope

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that lets us see the very
distant galaxy in more detail.

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This effect is called
gravitational lensing.

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Without this natural
boost from gravity,

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it would be impossible
for our telescopes

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to see far away enough
in space and time

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to study galaxies in
the early universe.

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The Hubble Space
Telescope has made

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use of gravitational lensing
to see many distant galaxies.

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And the larger James
Webb Space Telescope

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will be able to find galaxies
even fainter and farther

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than we've ever seen.

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With Webb, we will look
for the very first galaxies

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to form and really learn
about the early universe.

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