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Hello! Today you will learn a lot about space. For example, the story about the mysterious connection between Mark Twain and a famous comet, 10 cool things happening on Mars, and 3 ways to hear sound in Space
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00:00Some people, like the Andaman Islanders, that's a community living in the Gulf of Bengal,
00:05see them as burning torches thrown into the air by forest spirits.
00:09Others, like some Australian aborigines, think they're flaming sticks ridden by shamans.
00:16If you ask an astronomer, though, they'll tell you that a comet is a large object made of dust and
00:22ice that orbits the sun.
00:25Arguably one of the most famous space objects of this kind is Halley's Comet.
00:29It has left a great impact on our history and understanding of these mysterious falling stars.
00:35When this comet passed Earth in August of 1835, for example,
00:40it was blamed for the New York City fire that kept going for several nights.
00:44At the same time, the Seminole Indians in Florida saw the comet's long tail
00:49and believed it marked the day they would lose their independence.
00:54This comet came back in 1910, and people yet again saw it as a sign of bad luck.
01:00In Chicago, people bent over backward to secure their windows to protect themselves from the comet's dangerous tail.
01:08Others bought all sorts of gadgets, like umbrellas or masks protecting from comets.
01:15But what's so intriguing about this space body?
01:18How come it just pops up around Earth every once in a while?
01:21And, most importantly, is it really dangerous?
01:26Halley's is what astronomers call a periodic comet.
01:30It visits us every 75 years or so.
01:33On rare occasions, some lucky people get to see it twice in their lifetime.
01:38It last passed Earth in 1986, and it is expected to come back in 2061.
01:44Despite this scheduled return, the comet's orbit can't be predicted with precision.
01:50That's partly because of the chemical processes happening inside the comet.
01:54Halley's orbit may also change due to random interactions with other planets and space objects in our solar system.
02:02Its official title is 1P-slash-Halley, and it's named after English astronomer Edmund Halley.
02:09He was the one who studied the reports of a comet nearing Earth in 1531, 1607, and 1682.
02:17Based on his calculations, he concluded that these three occurrences had been, in fact, the same comet, returning over and
02:25over again.
02:26He also predicted its return in 1758.
02:31Halley's discovery also pointed out that some comets, like this one, orbited the Sun, but their journey was not circular.
02:39If you look at it in 2D, Halley's orbit looks like an elliptical wire dangling from the Sun.
02:45Sadly, Halley didn't live to see the comet's correctly predicted return, but it was named after him.
02:53According to the European Space Agency, the first sighting of Halley's comet dates back to March 30th, 239 BCE.
03:02Asian astronomers noted it down in the Shechi and Wenxian Thung Kao chronicles.
03:07But another study claims that we might have first noticed it even earlier than that, during the times of the
03:13ancient Greeks.
03:16Writings from that period reported a huge meteor that landed in northern Greece, leaving the local population perplexed.
03:24It soon became one of the ancient world's most popular tourist attractions.
03:28But the authors also noticed a comet in the sky at the time the meteor landed.
03:33They also reported the fact that the unusual space object had remained in the sky for about 75 days.
03:42Shakespeare himself seems to have written about this comet in his play Julius Caesar, around the year 1600.
03:49In this work, he included a now-famous phrase speaking of comets as unusual signs, saying,
03:56The heavens themselves blaze forth.
03:59It wasn't the last time famous writers felt a certain connection with this object.
04:04Writer Mark Twain even said in 1909,
04:07I came in with Halley's Comet in 1835.
04:10It is coming again next year, and I expect to go out with it.
04:15Surprisingly, Twain passed away on April 21st, 1910,
04:20one day after Halley's had emerged from behind the far side of the sun.
04:25We got a better look at the comet when it last passed us in 1986.
04:30Several spacecraft were sent toward Halley's to take samples of the comet's composition.
04:35This fleet of spaceships, dubbed the Halley Armada, flew nearby,
04:40one of them taking several pictures of the comet's core for the first time in history.
04:44We also had much better telescopes to look at the comet as it swung by our planet this time.
04:51Based on current studies, there's little to no chance that Halley's Comet could actually pose any danger to our planet.
04:58Most of the bad things associated with the comet were just fabrications.
05:04Even better, comets, in general, may have made life on Earth possible.
05:09Specialists believe that early in our planet's history,
05:12collisions with comets brought a significant amount of water here,
05:16which helped to form our oceans.
05:18These space objects may have also gifted us organic material necessary for the formation of life.
05:26Don't confuse comets with asteroids, though.
05:29Unlike asteroids, which are small rocky space bodies also orbiting the sun,
05:34comets are mostly made up of frozen ammonia, methane, or water.
05:38They contain only small amounts of rocky material.
05:42Because of their composition, comets are sometimes nicknamed dirty snowballs.
05:48Comets are made of four parts.
05:50A nucleus, a coma, a dust tail, and an ion tail.
05:55But their nucleus makes up most of their total mass.
05:58There are over 3,000 comets that we know of.
06:01But astronomers think there may be up to 1 billion of them in our solar system.
06:07A comet that is bright enough to be visible from Earth without the help of a telescope is called a
06:13great comet.
06:14Approximately one great comet can be seen every 10 years or so.
06:20People have noticed other comets for millennia.
06:23However, scientists have concluded that since comets shed a lot of material each time they orbit close to the sun,
06:30their lifespan may be only thousands of years.
06:32If you compare that to the age of the solar system, which is 4.6 billion years, it's a relatively
06:39small number.
06:42Since these space bodies are still present in the solar system today, there must be a source of comets somewhere
06:48out there.
06:49Otherwise, all comets would have disappeared a long time ago.
06:54Another famous comet is named Hale-Bopp.
06:58It came very close to Earth in January 1997.
07:02The last time it was seen near our planet before that was during the Bronze Age, back in 2000 BCE.
07:09This comet is much larger and more spectacular than Halley's.
07:13Its nucleus stretches for up to 24 miles in diameter and can be seen from the surface of our planet
07:19with the unaided eye.
07:22Comet Borelli was the second comet to be studied up close by a spacecraft.
07:27NASA's Deep Space One approached it in 2001 and gave scientists a detailed report of the comet's black core.
07:35This comet is surprisingly lopsided, but the reason for its unusual shape is still up for debate.
07:42Halley's comet appears to have formed in the Oort cloud at the outer edges of the solar system.
07:46But Borelli is said to come from an icy cloud of rocks beyond Neptune, which is called the Kuiper Belt.
07:55Comet Hyakutake gave us quite the show when it passed just 9.3 million miles from Earth in March 1996.
08:03It looked like an ice-blue splash with a faint gas tail.
08:07This comet amazed astronomers, too, as it produced X-rays 100 times more intense than scientists had predicted.
08:15A spaceship called Ulysses passed through Hyakutake's tail in May 1996, reporting that it was at least 350 million miles
08:24long.
08:25That's double the size of any other known comet's tail.
08:30The comet Wild 2 was examined by NASA's Stardust spacecraft back in 2004.
08:37The probe managed to fly within 147 miles of the nucleus of Wild 2, giving us some of the best
08:43comet pictures to date.
08:44It was also the first time we got samples of dust particles from a comet.
08:48The precious cargo came back to Earth in January 2006.
08:53Its aim was to shed light on the conditions under which Wild 2, and the solar system for that matter,
08:59formed those billions of years ago.
09:02Wild 2 is about 3 miles in diameter and covered with craters and cliffs.
09:07Death storms on Mars can really go crazy.
09:10They hurtle through the Red Planet's southern hemisphere, especially during the summer.
09:14These storms can grow and encompass large areas of the planet, as happened in January 2022.
09:21Then, a dust storm covered almost twice the area of the United States.
09:25Could it be something like this that caused one of the robots we sent to Mars to go missing?
09:31The atmosphere and climate are harsh on Mars.
09:34It's mostly a desert with strong winds and average temperatures of minus 81 degrees Fahrenheit.
09:40It drops down to minus 220 at the poles during the winter.
09:43A lander needs to be specifically equipped and very sturdy to withstand such conditions.
09:48But researchers thought the Beagle 2 could handle the difficult trip to the Red Planet.
09:54June 3, 2003.
09:56A team of researchers got one of their pioneering robots they were about to send to space ready.
10:01It was a small and compact lander called the Beagle 2.
10:05Its mission was to touch down on Mars and search for what the world has been actively looking for for
10:10decades now.
10:11Life on the Red Planet.
10:13Now, the touchdown was due on December 25th, but the signal never came.
10:19The team tried to contact the spaceship, but at one point, they had to accept they wouldn't be able to
10:24reach it.
10:25Some thought the landing was too difficult and complex after all.
10:29So, the lander crashed.
10:30But they couldn't find any technical errors.
10:33Others had a theory that the lander may have become entangled in its own parachute and fell down to the
10:39surface of Mars.
10:39Either way, the Beagle 2 was considered missing.
10:43Until 2015, when NASA took pictures of what could be the remains of the lost lander.
10:49They weren't just smashed debris.
10:51The components actually looked to be intact.
10:54The lander's remains were lying with its solar panels partially deployed around three miles away from the site where it
11:01was supposed to land.
11:02Apparently, the Beagle 2 managed to land successfully, but its radio antenna got blocked.
11:08That's why researchers couldn't control it from Earth or communicate with it.
11:12But no one knows exactly why it happened.
11:15Have you heard of a face on Mars?
11:18In the 1970s, one of NASA's spaceships took the iconic images of the Martian surface that showed a face-like
11:25formation, as you can see in the upper part of the picture.
11:28If you have a rich imagination, you can easily see a nose, two eyes, a mouth, and an unusual hairdo.
11:36Some even thought it was a monument built on the Red Planet by another civilization.
11:41How about some other unusual things people have found on Mars?
11:45Like Happy Face Crater.
11:47You can easily see why it has this nickname.
11:50Or rocks in different shapes.
11:52A pancake, brachiosaurus, or a fish.
11:55Mars also has a waffle-shaped island on its surface.
11:59It's a 1.2-mile-wide feature you can see in the area of lava flows.
12:03It might be the result of lava pushing this formation from below.
12:07It seems astronomers have also got some images of blue dunes.
12:12It's a sea of stunning dark dunes that strong winds sculpted into long lines.
12:17They surround the planet's northern polar cap and cover a region as large as Texas.
12:22The red planet is usually known for its brown, sandy dunes.
12:26So these ones certainly came as a surprise.
12:28In reality, though, they're not really blue.
12:31If you could visit Mars right now just to take a look, you'd see that these dunes appear brown and
12:37orange like the rest.
12:38And the picture is a false color image.
12:41Scientists often use false colors to highlight differences in something.
12:45For example, here it's the difference in depth.
12:48Also, the biggest valley on Mars is so large it could eat our Grand Canyon for breakfast.
12:54It's a fascinating system of canyons 2,500 miles long called Valles Marineris.
13:01And it's over 10 times as long as the Grand Canyon.
13:05Now, if you could stretch this Martian canyon, it would go from coast to coast of the entire United States.
13:12Since Mars doesn't have any active plate tectonics, no one knows for sure how this canyon formed.
13:18One theory says a chain of volcanoes located on the other side of Mars, the one that includes Olympus Mons,
13:25bent the crust from the opposite side of the planet.
13:28This powerful force caused cracks in the Martian crust as well as activated enormous amounts of water lying under the
13:35surface.
13:36This water then emerged and carved the rock away.
13:39The force activated glaciers too.
13:41And they possibly created new pathways in this gigantic canyon system.
13:47Volcanoes on the Martian surface could have erupted about 50,000 years ago.
13:51Although the most powerful eruptions happened 2 to 3 billion years ago.
13:56But the planet doesn't have active volcanoes today.
13:59Most of the heat stored in its interior during the planet's formation has been lost.
14:04So now, Mars' outer crust is way too thick for the molten rock to reach the surface.
14:10But a long time ago, eruptions formed giant volcanoes.
14:14And these volcanoes most likely had an important role in melting ice deposits,
14:19which released floods of water onto the Martian surface.
14:23Now, Mars has a thin atmosphere with a volume of gas, mostly carbon dioxide, less than 1% of Earth's.
14:30But 4 billion years ago, it was way warmer and wetter than now.
14:35Its atmosphere must have been thicker back then too.
14:38That's why it could create a powerful greenhouse effect and trap sunlight.
14:41Mars also has a powerful magnetic field.
14:45Similar to Earth's, it formed because of the currents of molten metals in the planet's core.
14:50But unlike our home planet, Mars lost its magnetic field after its core had cooled down.
14:56And without it, the planet didn't have any protection from the solar wind,
15:00which is a stream of charged particles flowing from the Sun.
15:03The solar wind pulled away most of Mars' atmosphere in just a couple hundred million years, give or take.
15:10This is what makes those powerful Martian dust storms even more intense.
15:15Mars has a fascinating history.
15:17Judging by the planet's glaciers, Mars has probably gone through multiple ice ages, just like Earth.
15:22A team of researchers got images of about 60,000 Martian rocks.
15:28Rocks were different in size and distributed randomly, which means they probably formed during different ice ages.
15:34Glaciers hide their own stories too.
15:36Who knows what kinds of gases, rocks, or even microbes could be trapped inside.
15:41Now, if you could get into a time machine and stop it 4 billion years ago, on Mars, of course,
15:47the chances are you'd see spectacular scenes of flooding.
15:51Maybe there would even be some form of life on the planet's surface.
15:55A strong meteorite impact that formed the red planet's gale crater could be something that triggered that mega-flood.
16:02After that collision, the temperatures on the planet got insanely high.
16:06This caused the melting of all that ice that was stored on the Martian surface at that time.
16:12The flooding was so massive, it changed the geological structure of the planet's surface.
16:17It carved out big ripples, as well as waves in the sedimentary rock.
16:21Now, speaking of water, vapor has been noticed escaping the atmosphere of Mars.
16:27Also, researchers have found some evidence of water flowing on the planet's surface.
16:31There are dark streaks in the soil.
16:34They seem to get bigger in the summer and shrink over the winter.
16:38There are numerous dried-out valleys and river channels on the planet.
16:41It's possible that liquid water once flowed there.
16:45Now, most of it could be locked up in ice caps or even hidden under the surface.
16:50More and more things hint that Mars used to be habitable.
16:54Mars is the only planet we know about where only robots live.
16:58Five rovers make up the Martian population.
17:00Those are Perseverance, Opportunity, Spirit, Sojourner, and Curiosity.
17:11These robots are there to take pictures and samples of soil and air, and maybe even find life on the
17:17red planet.
17:17And someday, we may reunite with them on Mars.
17:21Who knows?
17:22Oh, and by the way, if you really could get into a time machine and stop it 4 billion years
17:27ago on Mars, then I'd like to buy you lunch and talk about it.
17:32My treat!
17:33In space, no one can hear you scream.
17:36Or is that, in space, no one can hear ice cream?
17:39Well, either way, we know that no supernovas, crashing asteroids, and burning planets make a sound in space.
17:46Or do they?
17:48What if you actually can hear something out there?
17:51Well, let's see.
17:53Okie dokie, back to middle school.
17:55Ahem.
17:56Sound is a mechanical way of originating from vibration.
17:59Uh, what exactly does that mean?
18:01Well, the simplest example is guitar strings.
18:04Let's pluck one of them.
18:06It starts to vibrate.
18:07The atoms inside the metal string begin to push and beat the atoms of the air around them.
18:12So now, atoms are constantly pushing each other, until they reach our ears.
18:17It's like a wave from a pebble thrown into a pond.
18:20And it happens very quickly, at a speed of about 761 miles per hour.
18:26Then our eardrums begin to vibrate at the same frequency.
18:30And the little bones inside our ears transmit this vibration to the brain.
18:34The brain then does its magic, recognizes the pattern, and turns it into sounds.
18:41Great!
18:42Now we know that we need some particles to create sound.
18:45And we can find these particles in gases, liquids, and solid substances.
18:50And what about space?
18:52Nope, it's almost a perfect vacuum.
18:55And you've probably already heard that there's no sound in space because it's a vacuum.
19:00But what does it actually mean?
19:03Well, a vacuum is a perfect void.
19:06It's an area completely devoid of matter.
19:08It means there's nothing there.
19:10Yeah.
19:11Despite all those celestial bodies in space, there's actually no air in between them.
19:16No atoms, no particles, nothing.
19:18Nada.
19:19Zippo.
19:20Well, almost.
19:21To be honest, the perfect vacuum doesn't really exist.
19:25We can't get rid of atoms for good.
19:27But space is very close to this notion.
19:30On average, there are 15 to 80 atoms per one cubic inch.
19:34This may sound like a big number, but keep in mind that these atoms are tiny.
19:39And the void distance between them is huge.
19:42For comparison, one cubic inch of air contains about 16,000 atoms.
19:47So, of course, with such a low density, these atoms can't push each other.
19:52Even if the vibration is very strong, like, I don't know, a supernova, they still won't
19:57be able to do that.
20:00So, movies have been lying to us.
20:03All these epic space scenes actually take place in an awkward silence.
20:07Who would have guessed?
20:10But don't get upset.
20:11What if I tell you there are, in fact, some ways to hear sound in space?
20:17First of all, there's still sound on other planets.
20:20If there's an atmosphere on a space body, or at least something like gas, water, or a
20:25solid surface, there will be sound.
20:28In our case, the atmosphere becomes completely silent at about 60 miles above the Earth's
20:34surface.
20:35That's where the sky stops being blue, and a black starry veil begins.
20:41In any case, we'd have to land on another planet, or at least get close to its atmosphere
20:46to hear something.
20:48But whatever it is, it would sound very different.
20:51Let's take our favorite Venus as an example.
20:54The atmosphere there is very dense.
20:57Scientists jokingly call it a thick chemical soup.
21:00No thanks.
21:01So, if you somehow managed to stay alive and speak there, your voice would be very different.
21:07It would become much louder, and it would sound deeper.
21:12So, if you want a pleasant baritone, you know what to do.
21:17I wonder what would happen if Earth had a denser atmosphere.
21:20What would we hear then?
21:23Well, you can vaguely imagine that if you've ever been in the water.
21:27Water is very dense.
21:29Sound moves there much faster and better compared to the air, at a speed of almost a mile per
21:35second, depending on the water temperature.
21:38So, if you sit in an empty room with no sound sources, you won't hear much, right?
21:44Now, dip your head in the water and check out how the same silence sounds here.
21:48It's not quiet at all.
21:50Even if you ignore the ever-present sounds of the water itself, you'll immediately notice
21:55how well you can hear your own body, how your blood pulsates in the veins, how your
22:00heart works, the slightest movement of your fingers.
22:03Kind of creepy, isn't it?
22:05This gives us an idea of what would happen to us on a planet with a denser atmosphere.
22:10And that's just crazy.
22:11We would hear everything.
22:14From scurrying animals to the movement of tectonic plates.
22:17Ah, come on, you'd probably say.
22:20It's obvious that there's sound on other planets.
22:22But didn't you say we can hear something in open space?
22:26Actually, yes.
22:27For example, in a cloud of dust.
22:29You can find space dust almost everywhere in space.
22:33It may be the remains of a star or something else.
22:36And in these places, everything is a bit denser than usual.
22:40This means there are probably dust clouds where particles are very close to each other,
22:45which means they can produce sounds.
22:47Of course, those will be very quiet and transmitted over a very short distance.
22:53But it's better than nothing, right?
22:56Plus, we already have one real space sound recorded.
23:00It came from the Perseus galaxy, which is located 250 million light-years away from us.
23:07NASA recorded it in 2003.
23:10Those of us music geeks will want to know that it's a B flag, 57 octaves below middle C on
23:16the piano.
23:17You'd have to add another 660 keys to the left on the keyboard.
23:21But its frequency is so low that the human ear, unfortunately, can't hear it.
23:27But besides that, we can only hear something inside spaceships.
23:31These are small pockets of air, after all.
23:34In a spacesuit, you would hear sounds very well, too, including your breathing or blood circulation in a spacesuit.
23:42But two astronauts, flying side by side, wouldn't hear each other, even if they got very close and shouted very
23:49loudly.
23:49It's quite funny.
23:50If you, being an astronaut, bumped into something, it would be very loud for you, but your friend wouldn't hear
23:56anything.
23:57That's why astronauts use radio devices.
24:03Now, purely theoretically, if you could somehow crawl out of your spacesuit and survive, you'd be able to hear the
24:11chatter and noises going on inside the spaceship.
24:14But how?
24:15So, look, we have some air inside the spaceship, and it transmits sound.
24:20It reaches the metal casing and gets through it.
24:23And then, if you leaned against the ship, preferably touching it with your elbow or knee,
24:28the sound would be transmitted to the brain directly through your bones, ignoring the ears.
24:34Yes, our bones conduct sound.
24:37That's how, for example, deaf people listen to music.
24:40It's called bone conduction.
24:42It's used in some headphones and some other technologies.
24:46You can do a little experiment.
24:48Hold your fingers over your ears.
24:50Shut them properly so that you really don't hear much.
24:53Then try to touch a sound source.
24:55It can be anything vibrating.
24:57For example, a speaker playing music with some part of your body where the bone is close to the skin.
25:03Now, watch the miracle happen.
25:05You can hear the sound not through your ears, but directly in your brain.
25:09But please, don't repeat this experiment in open space.
25:13You know, ice cream?
25:14Ha ha.
25:15Now, you've probably heard about things like the sounds of space, where you can listen, for example, to the sounds
25:22made by the sun or different planets.
25:24How do we record these ones?
25:26Easily.
25:27There is another way to hear sound in space, electromagnetic waves.
25:32In other words, a radio.
25:34Radio is the same form of electromagnetic radiation as light.
25:38These waves can travel in a vacuum without any problems.
25:42Astronauts' transmitters work that way.
25:45An astronaut says something to their friend.
25:48The sound waves turn into radio waves, reach the other person, and are then converted back into sounds.
25:55And this is how we get so-called space sounds.
25:59Our planet is actually very loud in that regard.
26:02We're sending a huge amount of radio waves into the universe, all radio signals we've ever listened to.
26:08It's a pity that they travel only 110 light-years away from us.
26:12But, you know, I think it's good that we don't hear everything that happens in space.
26:17Imagine if sound could easily travel through the universe, we would hear everything, from solar flares to nearby supernovas.
26:26Horrifying, right?
26:27So, maybe we're just lucky.
26:29Hey, remember, in space, you can hear ice cream.
26:33Chocolate!
26:35Vanilla!
26:35Vanilla!
26:36Vanilla!