00:00Bang, or should I say Big Bang, the Big Bang, ahem.
00:05So after the Big Bang, the universe resembled a hot soup of protons, neutrons, and electrons.
00:12After it started to cool down, the protons and neutrons began to combine, first forming
00:17ionized atoms of hydrogen and later some helium.
00:22These ionized atoms of helium and hydrogen attracted electrons, turning them into neutral
00:27atoms.
00:28As a result, the light was able to travel freely for the first time ever, since it was
00:33no longer scattering off free electrons.
00:36What does it mean?
00:37The universe was no longer dark.
00:40At the same time, it was still about a few hundred million years after the Big Bang before
00:44the very first sources of light started to appear.
00:48That's when the cosmic dark ages came to an end.
00:51We don't know for sure what this universe's first light looked like or how the first stars
00:56formed.
00:57Luckily, we have the James Webb Space Telescope to help us find the answers.
01:02How come?
01:03All because this is an infrared telescope.
01:06Why is it important?
01:08Let's figure it out.
01:12Imagine a star.
01:13It's a very, very old star, maybe the first star out there.
01:17Light leaves this star 13.6 billion years ago and settles off on an incredible journey
01:22through space and time.
01:25It needs to get to our telescopes.
01:28By the time this light reaches us, its color, or wavelength, shifts towards red.
01:33That's something we call a redshift.
01:37It happens because when we talk about very distant objects, Einstein's theory of general
01:42relativity comes into play.
01:44According to it, the expansion of the universe also means that the space between objects
01:49stretches, making them move away from one another.
01:53But that's not all.
01:54Light stretches too, which shifts it to longer wavelengths.
01:58Eventually, this light reaches us as infrared.
02:03In other words, redshift means that light that is originally emitted by the first stars
02:08or galaxies as ultraviolet or visible light gets shifted to redder wavelengths by the
02:13time we catch a glimpse of it here and now.
02:17For the farthest objects with very high redshift, that bare minimum of visible light is shifted
02:22into the near and mid-infrared part of the electromagnetic spectrum.
02:28That's why to see those space objects, we need a super powerful telescope.
02:33And if we talk about the Webb telescope, it can see back to about 100 million to 250 million
02:40years after the Big Bang, which is incredibly awesome!
02:45So by observing the universe at infrared wavelength, James Webb lets us see things no other telescope
02:51has ever shown before.
02:54The primary goal of this incredible piece of equipment is to study the formation of
02:59galaxies and stars that formed in the early universe.
03:03To look that far back in time, we need to look deeper into space.
03:08All because it takes light time to travel back from there to us.
03:13So the farther we look, the further we glimpse back in time.
03:17To find the first galaxies, James Webb is going to make an ultra-deep near-infrared
03:22survey of the universe.
03:24Then it'll follow it up with a few other methods of research.
03:29Now as you remember, the gas between stars and galaxies in the early universe was opaque
03:35and energetic starlight couldn't penetrate it.
03:38But then, about 1 billion years after the Big Bang, it suddenly became completely transparent.
03:44Why?
03:45The James Webb Telescope might have found the reason.
03:49At one point in the past, the first galaxies' stars emitted enough light to ionize and heat
03:55the gas around them.
03:57This helped clear the view over hundreds of millions of years.
04:01The newest insights scientists got were about a time period called the Era of Reionization.
04:07That's when the universe underwent some dramatic changes.
04:12After the Big Bang, gas in the universe was unbelievably hot and dense.
04:17Hundreds of millions of years passed, and it cooled down.
04:20But then something baffling happened.
04:22It was as if the universe hit the repeat button, and the gas became ionized and hot once again.
04:29It could have happened because of the formation of early stars.
04:33After that, millions of years later, this concoction became transparent.
04:38For a long time, researchers have been hoping to find definite evidence that could explain
04:44these changes.
04:45And now, the telescope has finally shown that those transparent regions are located around
04:51galaxies.
04:53Astronomers have seen these galaxies reionize the gas surrounding them.
04:57Even better, they've managed to measure how large these transparent regions are.
05:03They're ginormous compared to the galaxies themselves.
05:07Imagine a hot air balloon, and now imagine a pea floating inside.
05:12You've got it, and guess what?
05:14These tiny galaxies drove the entire reionization process, clearing huge regions of space around
05:21them.
05:22These transparent bubbles kept growing until they merged and caused the entire universe
05:27to become transparent.
05:30The research team chose to target a period of time before the end of the era of reionization.
05:37At that time, the universe was not quite opaque, but not quite clear either.
05:42It was a patchwork of regions of gas in different states.
05:46To find out this cool fact, the astronomers aimed the James Webb Telescope in the direction
05:52of a quasar, an incredibly bright space object.
05:56It acted as a giant flashlight, traveling towards us through different regions of gas.
06:01It was either absorbed by the patches of near opaque, or moved freely through the areas
06:06where the gas was transparent.
06:10The scientists then used Webb to examine galaxies in that region of space.
06:15They found out that these galaxies were usually surrounded by transparent regions with a radius
06:21of about 2 million light years.
06:24For comparison, the area the galaxies cleared was almost the same distance as the space
06:29between our home Milky Way galaxy and our nearest neighbor, the Andromeda galaxy.
06:35And the telescope witnessed those galaxies in the process of clearing the space around
06:39them.
06:40It was the end of the era of reionization.
06:43Until then, no one had evidence of what caused reionization.
06:49The team is planning to dive into research about other galaxies in five additional fields.
06:56The Webb Telescope's results from the first field have been overwhelmingly clear.
07:01And even though the astronomers had expected to identify a few dozen galaxies existing
07:06during the era of reionization, they actually managed to spot 117!
07:14Now let's talk a bit about the main hero of today's show, the James Webb Space Telescope.
07:20It's an absolutely stunning piece of equipment which is around 100 times more powerful than
07:25the Hubble Space Telescope.
07:27And the latter has observed places that are 13.4 billion light years away!
07:32The James Webb Telescope is also on the pricey side, to put it mildly.
07:37Even though originally the cost of the telescope was estimated to be just 1 to 3.5 billion
07:44The whole development process cost around 10 billion dollars.
07:48For comparison, it cost NASA 4.7 billion dollars to build and launch the Hubble Telescope.
07:55And it was another 1.1 billion dollars to fix it in orbit.
08:01Even though the James Webb Telescope itself is three stories high and the size of a tennis
08:06court, its mirrors are the lightest large telescope mirrors of all time.
08:11During the manufacturing process, they underwent a 92% reduction in weight.
08:17When you look at them, the telescope's mirrors seem to be gold, but in reality, they're
08:21made of beryllium.
08:23This is a steel gray, lightweight and brittle metal.
08:27A gold coating is applied to each mirror, that's true.
08:30But they can't be produced entirely out of gold, since this precious metal tends to
08:34expand and contract, even with small temperature changes.
08:40So the total amount of gold in the James Webb Space Telescope is less than 2 ounces.
08:45That's a golf ball sized piece of gold.
08:48And the gold plates covering the mirror are less than 1,000 atoms thick.
08:53As for the telescope's abilities, it would be able to clearly see a US penny from 24
08:58miles away and a football from 340 miles away.
09:03James Webb's telescope side is cooling itself down, and its temperature doesn't rise higher
09:08than minus 370 degrees Fahrenheit.
09:12That's cool enough to make liquid nitrogen.
09:15A truly enormous five-layered sun shield surrounds the telescope and reflects away as much sunlight
09:21as possible, letting the telescope stay cool.
09:25That's it for today!
09:28So hey, if you pacified your curiosity, then give the video a like and share it with your
09:32friends.
09:33Or if you want more, just click on these videos and stay on the Bright Side!
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