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The space is getting warmer, what could happen next? What makes a comet different from an asteroid? You will find answers to these and other questions in our space video!
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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,
00:39it 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 Wensien 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.
06:02But 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.
09:07The universe is not static.
09:09It evolves all the time, and grows in all directions.
09:12It's expanding, and scientists found this out almost a century ago.
09:16And it's not at a stable rate.
09:18The more time goes by, the faster the universe expands.
09:22As this happens, stars, planets, and galaxies move farther and farther apart, which leaves more space between them.
09:30If that's the case, the universe is supposed to become colder as it expands, right?
09:35After all, it was a lot denser when the Big Bang happened, and a lot hotter.
09:40As it was expanding, space was cooling down, which created conditions for planets, stars, and other space objects to form.
09:48Yeah, that's not exactly the case now.
09:51Scientists were surprised to hear it, too.
09:53But our universe is actually getting hotter.
09:57They observed the temperature of cosmic gas farther away from our home planet compared to young gases closer to the
10:03Earth.
10:03Since we measure distance in space by light years, farther areas are like going back to the past, and regions
10:10closer to us are like observing the present day.
10:13They found out the temperature of a gas in space has gone up more than 10 times in the last
10:1810 billion years.
10:20Now, the temperature of the cosmic gas that's spread all across the universe can get to around 4 million degrees
10:26Fahrenheit.
10:27Wow!
10:28As the universe expands, gravitational force does its part and pulls gas and dark matter together.
10:34It's doing some pretty hard work there.
10:36It creates galaxies and clusters of galaxies out of them.
10:40And this process is totally chaotic.
10:42It's so messy that more and more gas heats up as all of this is happening.
10:49Space was extremely hot when it was just forming, 13.7 billion years ago.
10:54What if it gets warm like that once again?
10:58Scientists are observing the situation.
11:01They found out the temperature in space increased by measuring cosmic gases using something called redshift.
11:08They generally use this method when they want to see how far away some space objects are.
11:12Those that are closer to us have shorter light wavelengths.
11:16The farther some object is, the longer its light wavelengths are.
11:20And they can now determine the temperature of a certain object from its light.
11:24On average, space is a pretty cold place.
11:27The glow that's left from the Big Bang is called the CMB, which is short for the Cosmic Microwave Background.
11:34It's so powerful and intense, it bathes the entire universe in light.
11:39It's the only thing that significantly heats up matter.
11:43But there are many smaller mechanisms that help to heat up matter in the universe.
11:47And they could go crazy if space warms up.
11:50Like stars, they emit radiation that affects nearby dust and gas.
11:56They radiate throughout the far infrared too.
11:58When a star is at its early stage, the radiation coming from it forms proto-planetary structures that look like
12:05disks.
12:06They primarily form in a single plane.
12:09And a bright central star produces spectacularly illuminated gas.
12:13And there are blue reflections of this gas.
12:16It was like that with our planetary system too.
12:19Strong energy and gravitational forces cause collisions, dust, and gas in an uncontrolled vortex that's forming planets.
12:29That's why most planets in our solar system orbit in the same direction.
12:32That's the direction this giant whirlpool was spinning a long time ago too.
12:38Active stars, colliding galaxies, stellar cataclysms, black holes, neutron stars.
12:43The universe has so many sources of energy.
12:46And when you surround normal matter in space with such an energetic environment, it heats up drastically.
12:53When you heat something up, it radiates that energy away in a certain way.
12:58In most cases, galaxies have just a couple of areas where stars are forming.
13:03At regions where gas is collapsing.
13:05A bubble that surrounds that area contains ionized hydrogen.
13:10Three quarters of our sun is hydrogen.
13:13Thanks to that hydrogen, the sun keeps us warm.
13:15In its core, hydrogen transforms into helium and causes atomic fusion.
13:21Yep, that's how our sun releases its energy.
13:26Radiation heats all that gas to thousands and thousands of degrees.
13:30At the same time, it ionizes a large number of atoms and molecules.
13:34Which basically means it turns them into ions.
13:38Atoms are neutral particles.
13:39And ions are either negatively or positively charged particles.
13:43If the universe heats up, our sun might too.
13:47If its temperature hits 30,000 degrees Kelvin, it could become hot enough to ionize all those materials it had
13:54previously ejected.
13:55And it could create a real planetary nebula.
13:58This would be a nebula in the shape of a ring that forms because of an expanding gas that surrounds
14:04an aging star.
14:05As the temperature goes up all the time, hydrogen ionizes.
14:09At a few thousand degrees, this could turn the nebulae in our solar system pink with emission lines.
14:16Our sun could come to its end if it reaches the temperature of 50,000 degrees Kelvin.
14:21If you could float in space and come closer, you'd see it glow in eerie green tones because of doubly
14:28ionized oxygen.
14:29Higher energy phenomena make more galaxies collide.
14:33This heats gas even more and eventually results in X-ray emissions.
14:38What about black holes and radiating neutron stars?
14:41When they go crazy, they can shape whole galaxies and who knows what more?
14:46Maybe we'd have more masers, too.
14:49Those are natural lasers our universe produces.
14:53They arise when big populations of molecules receive large amounts of energy.
14:57By now, scientists have found the strongest, yet the most distant, maser.
15:02So powerful, it's more luminous than the light 6,000 suns would produce.
15:07And in just one emission line.
15:10Maybe then we'd discover even stronger masers.
15:13That's in the case that we're even going to be here at all.
15:17Because as the universe is getting hotter, cosmic radiation is getting stronger.
15:22Not so good for life on Earth.
15:24Increased cosmic radiation could harm us.
15:27Who knows if life would even be possible on Earth in that case.
15:30Or if the powerful gravitational force would pull our home planet, too.
15:34And crash it into another one.
15:37But maybe, life as we know it wouldn't completely disappear.
15:40Or if that happened, it could possibly somehow find its way once again.
15:46Maybe in the distant future.
15:47There's a possibility our universe could support life at its early stages.
15:52Doesn't look like that when you think of the chaos the Big Bang caused, right?
15:56But that was only in its mere beginnings.
15:59After things had settled down a bit, the dregs of enormous, earliest stars formed rocky planets.
16:05In our solar system, those are Earth, Mars, Mercury, and Venus.
16:10You can't set your foot on the rest of them, since they're gas giants.
16:14Back in that time, radiation was quite intense.
16:18So rocky planets had an adequate environment to form.
16:21Since it takes a lot of energy to whirlpool dust and particles and bake a planet in the end.
16:27This period of time coincides roughly with that when the first stars formed in our universe.
16:33Ancient stars were way bigger than our sun.
16:36They lived shorter, though.
16:37They would have just exploded as supernovas on their end.
16:40And they would leave heavy metals across the space around them.
16:44Those are the particles rocky planets formed from.
16:48Radiation spread around the whole universe back then.
16:51It has changed over time.
16:54Today, it's almost an absolute zero.
16:57400,000 years after the Big Bang, when hydrogen atoms were forming,
17:01CMB was almost as hot as the surface of our sun.
17:05And about 15 million years after the Big Bang,
17:08its temperature was close to room temperature, which is around 80 degrees Fahrenheit.
17:13These things were happening across the universe,
17:16so there were many planets that could potentially hold life.
17:19If we were one of those ancient worlds, we wouldn't need a star to keep us warm.
17:24CMB would be enough to do it.
17:28So, it's possible that life in space is way older than we think it is.
17:32There could have been ancient worlds with liquid water on their surface.
17:36What if there were some primitive forms of organisms, like on our home planet, a long time ago?
17:41Or even more developed ones?
17:43Perhaps we'll find out one day.
17:46Back when Apollo missions were launched, astronauts, returning from the moon,
17:50claimed that moon dust, the gray sand-like dust covering much of the satellite's surface,
17:55smelled and tasted, yes, they actually tasted it, like gunpowder.
18:00But the stuff moon dust is made of is nothing like gunpowder.
18:03About half of its composition is silicon dioxide glass from impacts with meteorites.
18:09They hit the surface of the moon at incredible speeds.
18:12Whoa!
18:12The high temperature makes the topsoil fuse into glass,
18:16and the impact shatters it right afterwards, creating the gray and clingy dust.
18:21The rest of moon dust ingredients are minerals, such as iron, calcium, and magnesium.
18:26While old-fashioned gunpowder consists mainly of saltpeter, charcoal, and sulfur.
18:31In other words, moon dust shouldn't smell like gunpowder.
18:35But it does.
18:37Besides, when astronauts brought samples of it back to Earth, there was no smell left at all.
18:43One explanation could be that the moon is similar, in a way, to Earth's sand deserts, like the Sahara.
18:49It's extremely dry and arid.
18:51When you sniff the air in a desert, you don't smell anything.
18:54But if you get caught in the rain there,
18:56the moisture will raise all kinds of odors from the ground that were previously trapped in the dry sand.
19:02With moon dust, it might be similar.
19:05While on the surface of the moon, it doesn't smell at all.
19:08Not that the astronauts could sniff at it wearing their spacesuits, though.
19:12But when brought back inside the landing module,
19:15the dust came into contact with moisture in the air and started emitting its strange odor.
19:19Another reason for this could be a reaction of moon dust to the solar wind.
19:24Ionized particles from the sun hit the bare surface of the moon and stay there.
19:29There's no thick atmosphere to protect it from those ions,
19:32so they travel freely right to the ground.
19:35They're very lightweight, so they can fly off and sort of evaporate from the slightest of nudges.
19:40And when astronauts took the moon dust samples to the landing module,
19:44those particles could have started moving around and giving off the specific smell.
19:49This might also explain why the samples didn't keep their odor when brought back to Earth.
19:54Since the particles are so light, they might have flown off the samples already in the landing module.
20:00And when they were placed in airtight containers, there were little or no ions left on them.
20:05Another explanation is that those airtight containers weren't so airtight after all.
20:10Moon dust is basically very small crystals with extremely sharp edges.
20:15They unexpectedly made tiny cuts in the seals,
20:18letting in air and moisture, and so the ionized particles leaked out of the containers.
20:23Scientists believe they should study moon dust on the surface of the moon itself
20:27to find out everything about its properties.
20:30Now, there are hundreds of thousands of craters on the surface of the moon
20:33made by falling asteroids, but one of them drew a lot of attention.
20:38It turned out to not be just an impact crater,
20:41but a tube looking most like an entrance to a cave system.
20:45Scientists found a specific echo pattern that suggested there was a hollow area beneath.
20:50They discovered more echo patterns at a couple of places near the hole.
20:54So, there could be more lunar tubes there.
20:57But in this big tube, you could place an entire football field.
21:01Researchers believe there could be an entire geological wonderland under the surface.
21:06It could be a good shelter for astronauts landing on the moon or even be a harbor for a lunar
21:11colony.
21:12No one ever managed to stay on the moon for more than three days because of the conditions on the
21:17satellite.
21:18Wide range of temperatures, low atmosphere, no magnetic field would protect life on the surface
21:23from things like radiation or solar wind.
21:26Astronauts wear spacesuits.
21:28They can't protect them over long periods of time, but a lava tube could.
21:33When a lava flow cools, it gets a hard crust, which later thickens and creates a roof over that same
21:39lava.
21:40It continues to flow, but when it stops, the channel can drain.
21:44And that's how an empty tube appears.
21:46Our planet also has lava tubes, but they're not as big as the one found on the moon.
21:51Back in 1178, I wasn't around then, at least five people in England claimed they had seen the moon split
21:59into two from its upper tip.
22:01It was in the shape of a crescent at the time of the event.
22:04When the crack widened, fire started blazing from it, which the single monk who chronicled it described it as a
22:10flaming torch spraying up,
22:12spewing out fire, hot coals, and sparks.
22:15Then the moon started shifting around and pulsating, but soon stopped and turned a slightly darker shade.
22:22The event didn't receive much attention from scientists, though, until the second half of the 20th century.
22:28Researchers studied the chronicle and figured out there was a huge, 14-mile-wide crater on the surface of the
22:34moon
22:34at about the spot described in the book.
22:37Only a very large asteroid could have left such a scar on the satellite's face.
22:41And when they investigated it more closely, they found out it was pretty recent by astronomical standards.
22:48In fact, it really could have appeared about 800 years ago.
22:52But in that case, millions of fragments from the asteroid and the moon would have hit the Earth as well.
22:58And then people would have seen an incredible meteor shower.
23:02It would have been very bright, and the memories of it would have definitely been in the archives.
23:06But that didn't happen.
23:08In addition, many scientists argue that the crater isn't as young as it might seem.
23:13The most popular and justified theory is that it's about 1 to 10 million years old.
23:18If it had appeared as recently as 800 years ago,
23:22parts of the surface of the moon in and around the crater would still have been warm from the impact.
23:27The most likely explanation of what really happened back in 1178
23:32is that observers were extremely lucky to see an asteroid falling towards the Earth
23:37and burning in our planet's atmosphere.
23:39The spectacle would have been incredible.
23:42And seen from a proper angle,
23:44the burst of the asteroid could have really looked like it was the moon exploding.
23:48That would explain why there were so few witnesses of the phenomenon.
23:51The right spot to see the show, as they did, was only a couple of miles wide.
23:57As for real events on the moon,
23:59water and oxygen were unexpectedly discovered on it not long ago.
24:04Water might have been brought to the satellite by asteroids hitting its surface,
24:08many of them carrying H2O molecules,
24:10and those that are left on the moon in tiny amounts after the impact.
24:14There's precious little water there, though.
24:16By comparison, even the Sahara Desert has more of it than the entire moon.
24:22Oxygen is also present as separate molecules floating around,
24:25so you still can't breathe on the moon.
24:28Solar wind brought them there.
24:29Waves of energy from the sun travel at extremely high speeds through space,
24:34scrape oxygen from the upper parts of our atmosphere,
24:37and carry it further.
24:38Eventually, the wind with the oxygen molecules reaches the moon.
24:42And that's where something incredible happens.
24:45The moon starts rusting.
24:47There's plenty of iron in the lunar soil,
24:49and when it's exposed to oxygen and water, it naturally rusts.
24:53Some parts of the moon have actually already turned slightly reddish.
24:57They're regions where there's the highest concentration of molecules.
25:01If this process goes on long enough,
25:03in the distant future, the moon will look like Mars.
25:06It will turn orange-red.
25:08Yes, the signature color of Mars came exactly from the corrosion
25:12that began there thousands and thousands of years ago.
25:15When there were rivers and seas with water and an atmosphere with oxygen.
25:20Another unusual phenomenon is the blue and red lights on the moon.
25:24They can be seen when it's crescent-shaped.
25:26The flashes come and go very quickly, almost like lightning.
25:30And in fact, that's what they basically are, electric bursts.
25:34Tidal forces are to blame for this.
25:36They cause mechanical stress buildup in the rocks.
25:38This can produce an electric field,
25:41which creates the blue flashes that have surprised many amateur astronomers.
25:45But still, there's so far been no green cheese discovered there.
25:50Or moon pies, for that matter.
25:52Disappointing, I know.
25:53And in the first order of being controlled by Fingering
25:53it to artef which has differed now.
25:54I'll be able to say it's unclear.