Earth's journey through the universe is a perilous one; new discoveries reveal that the planet is heading toward a mysterious area of the cosmos.
Thanks for watching. Follow for more videos.
#cosmosspacescience
#howtheuniverseworks
#season8
#episode9
#earthorbit
#cosmology
#astronomy
#nasa
#space
#spacetime
#spacescience
#earthdeathorbit
Thanks for watching. Follow for more videos.
#cosmosspacescience
#howtheuniverseworks
#season8
#episode9
#earthorbit
#cosmology
#astronomy
#nasa
#space
#spacetime
#spacescience
#earthdeathorbit
Category
📚
LearningTranscript
00:00The Earth is taking us on the ride of our lives, hurtling through space in ways we never imagined.
00:12The Earth is extremely dynamic. It is spinning on its axis. It's whirling about the sun. It's corkscrewing throughout this galaxy. It's just never a dull moment.
00:24It's like doing a waltz on top of a carousel that's on top of a high-speed train.
00:30Now, we're unlocking the secrets of our planet's voyage and discovering that Earth's journey affects us all.
00:40We see evidence of this motion everywhere we look, not just in the motions of objects in the sky, but in the land and the seas themselves.
00:51Life on Earth wouldn't be the same if we didn't find ourselves in this dramatic environment in space.
00:56But the ride can be dangerous.
01:05Plunging our planet into the deep freeze.
01:10Putting us in the path of supernovas.
01:15Pulling Earth and the entire galaxy toward the unknown.
01:19The galaxy's traveling through space. Where is it going?
01:24It's an area of really cosmic mystery.
01:26So, strap in for Earth's cosmic journey.
01:30We are Earth's passengers as our home planet travels through the cosmos.
01:54To us, everything seems calm.
02:02Nothing could be further from the truth.
02:06Contrary to what you might think just based on your everyday experience,
02:09the Earth is actually hurtling through space at amazing speeds in a lot of different ways.
02:13Even just the motion of the stars through the sky at night gives you a clue that the Earth is not sitting still.
02:23The Earth is spinning at every moment.
02:26And we can see this most clearly in the fact that we have day and night.
02:31We might not think about it,
02:33but our lives are tuned to Earth's journey
02:36as it spins through space.
02:39There's really nothing more basic to us than that cycle of day and night,
02:46that 24-hour cycle.
02:49All of life on Earth evolved with a day-night cycle.
02:53So, it's ingrained into every organism on this planet.
03:00Life evolved in lockstep with Earth's spinning motion.
03:04But in the ocean, corals take things a step further
03:12by keeping a record of every planetary turn.
03:22They have a daily cycle which creates a deposit almost like a tree ring.
03:26But instead of it being once a year, it's once a day.
03:28So, you look at a bunch of tree rings, you can count the number of years the tree was alive.
03:37Corals record not just the yearly cycle, but the daily cycle of night and day.
03:42These are recorded in these little growth bands in the coral.
03:45By counting the coral's growth bands,
03:48we can work out the number of days in a year.
03:50Sounds simple, but when we look at ancient, fossilized coral,
03:56we discover something strange.
03:59We can look at fossils of corals that are hundreds of million years old,
04:02and if we do that, we find that the year is not 365 days long.
04:08It's more like 420 days long.
04:11When the ancient corals were alive, there were 420 days in one Earth year.
04:23Meaning, a day was just 21 hours long.
04:29To find out how this was possible,
04:31we need to go back to the start of Earth's cosmic journey.
04:354.6 billion years ago,
04:44our planet traveled a dangerous path
04:48through a chaotic and violent solar system.
04:57Collisions were frequent.
05:05One giant impact set our planet spinning rapidly.
05:24And formed the moon.
05:28Going all the way back to the time that the moon formed,
05:32the Earth may have had a day as short as two and a half hours.
05:38As the Earth continued on its path
05:40through the early solar system,
05:42our planet cooled
05:45and the surface became solid.
05:50But the violence wasn't over.
05:54The young Earth
05:56was bombarded
05:57in the early days of the solar system.
06:00And when these rocks
06:02hit the Earth,
06:03they almost never hit directly on.
06:05They'd hit at an angle.
06:16With each collision,
06:18it adds a little bit more momentum
06:20and a little bit more spin
06:21to the Earth.
06:26The added spin that you get
06:27is kind of like a merry-go-round.
06:29You can imagine
06:30with each kid that pushes
06:31and jumps on the merry-go-round,
06:33you have greater spin.
06:38As our planet journeyed on,
06:40asteroid impacts
06:41set the young Earth
06:42spinning 12 times faster
06:45than it does today.
06:48Our planet's rotational speed
06:50has huge consequences for life.
06:53On Earth,
06:55the spin of our planet
06:56actually has an effect
06:58on our weather.
07:00With a shorter day,
07:02one of the effects
07:03that might have been apparent
07:04on Earth at that time
07:05was more storms developing.
07:11A phenomenon still in action today
07:13drove these powerful ancient storms.
07:16We call it
07:20the Coriolis effect.
07:22The Earth's spin
07:23creates phenomena
07:25in Earth's atmosphere
07:26and oceans.
07:27This determines patterns
07:28of circulation
07:29in combination
07:30with the heat energy
07:31from the sun.
07:35The rotation of the Earth
07:36matched with solar heating,
07:38especially at the equator,
07:40causes air to rise up
07:41and then also sort of
07:42to move sideways
07:43and sets up spin.
07:45As the young Earth
07:46continued its journey,
07:48the planet's rotation
07:49whipped up ferocious
07:51planet-wide storms.
07:56The fast spin
07:57would have been disastrous
07:59for any life.
08:01The storms would have been so big,
08:03it's hard to say
08:04if life would have evolved at all.
08:09Fortunately for humankind,
08:12Earth has a traveling
08:13companion,
08:15the Moon.
08:16And it helps slow
08:17our planet's spin.
08:21What happened next
08:22was kind of a wonderful
08:23gravitational dance
08:24between these two bodies.
08:26As they were spinning,
08:27they were also interacting
08:28with each other.
08:29The Moon's gravity
08:31pulled on Earth's oceans,
08:33generating tidal bulges.
08:36Material was moving
08:37in and out of the tidal bulges
08:39as they spun,
08:40and this creates friction
08:41and a kind of drag
08:42that actually slowed down
08:43the rotation.
08:47The tides also helped
08:50create life.
08:51Giant tides swept nutrients
08:53from the land
08:54into the oceans
08:56for the first time.
08:58A primordial soup
09:00began brewing.
09:01and life arose.
09:14As Earth's spin
09:15continued to slow down,
09:18life spread across the planet.
09:22But our planet's spin
09:29is just one part
09:31of our cosmic ride.
09:34Realizing how complicated
09:35our larger environment
09:37in the universe is
09:37is a wonderful thing.
09:39There are so many things
09:40that affect the orbit
09:41of the Earth,
09:41the tilt of the Earth,
09:42things that affect
09:43our climate.
09:46Clues to Earth's
09:47space voyage
09:48are hidden
09:49all across the world.
09:52Could our planet's
09:53wild ride
09:54explain
09:55how one of the driest
09:56places on the planet
09:57was once wet?
09:59The Sahara Desert.
10:18Dry, dusty, desolate.
10:23But hidden deep
10:25in a desert cave
10:26is a clue
10:27that thousands of years ago
10:29the Sahara
10:30was a lush
10:32green paradise.
10:35Archaeologists
10:36have unearthed
10:37rock art
10:38which clearly depicts
10:40humans and animals
10:41swimming in lakes.
10:45And by looking
10:46at satellite images
10:47we can trace out
10:48the outlines
10:49of ancient
10:50river valleys.
10:54The Earth's
10:55fast rotation
10:56influenced our planet's
10:57ancient weather patterns.
10:59could another motion
11:01have changed
11:02the desert climate?
11:04To unravel the mystery
11:06we need to rewind
11:07the clock
11:084.6 billion years
11:10to when the
11:15infant solar system
11:16was a planetary
11:19shooting gallery
11:20and the Earth
11:28spun through the solar system
11:29with a slight tilt.
11:33Earlier on
11:33before the formation
11:34of the moon
11:34the Earth didn't have
11:35much of a tilt
11:36and the impact
11:37knocked us completely
11:38out of whack
11:39to about 80 degrees.
11:40Our planet
11:49might have continued
11:49its journey
11:50tilted right over
11:51but over billions
11:53of years
11:53the moon's gravity
11:55pulled the Earth
11:56upright
11:56just not completely.
11:58The moon is
12:00not quite
12:01in the equatorial plane
12:02of the Earth
12:03it's above
12:04the equatorial plane
12:05and it
12:05pulls the Earth's
12:07axis
12:07into a
12:0823 and a half
12:09degree tilt.
12:12If we didn't
12:13have the tilt
12:13to about 23 degrees
12:14then we wouldn't
12:15have the seasons
12:16and these seasons
12:17drive a lot
12:18of the crops
12:19and the growth
12:19and the ability
12:20to survive
12:21all across the globe.
12:24But the ancient
12:25greening of the Sahara
12:27can't be explained
12:28by the changing seasons.
12:31Another planetary motion
12:32must be in play.
12:35A clue
12:36is found
12:37in the night sky.
12:38The North Star
12:41Right now
12:44the Earth's axis
12:45is pointed
12:46towards a star
12:47in the sky
12:48called the North Star
12:49Polaris.
12:50We've actually
12:51named it
12:51after the fact
12:52that the north pole
12:53of the Earth
12:53points toward it
12:54in the sky.
12:56But Polaris
12:56hasn't always been
12:58the North Star.
13:005,000 years ago
13:01it was a totally
13:02different star.
13:03It was Thuban
13:04which is in Draco
13:05a different constellation.
13:06Sometime in the future
13:07it'll be Vega
13:08the brightest star
13:09in the constellation
13:10Lyra.
13:10So the North Star
13:11actually changes
13:12because the North Pole's
13:14position in the sky
13:15changes.
13:16The changing pole star
13:18is evidence
13:19that Earth
13:20is wobbling
13:21through space.
13:23It's a process
13:23called precession
13:25rotation.
13:26Something that also
13:27affects spinning tops.
13:29If you take a top
13:30and let it spin
13:31really rapidly
13:32and poke it
13:33the axis of rotation
13:35will spin around
13:36like this.
13:37And it's much slower
13:38than the actual
13:38spin of the object.
13:40That is precession
13:41this circle
13:42that the axis
13:43is making.
13:44This happens
13:45to the Earth
13:46as well.
13:50A cosmic poke
13:51caused Earth's
13:52space wobble
13:53but what has
13:55the power
13:56to poke a planet?
14:00Once again
14:01the key
14:02is gravity.
14:04This time
14:04Earth's
14:05gravitational
14:06interactions
14:07with the Moon
14:08and Sun.
14:10These forces
14:12are that poke
14:13on the spinning Earth
14:14and that's what
14:15makes the Earth's
14:15axis spin
14:16in precession
14:17and it takes
14:18about 20,000 years
14:19to make a complete
14:20circle once.
14:22As the Earth
14:23continues its journey
14:24around the Sun
14:25this precession
14:27changes the planet's
14:28climate dramatically.
14:30When the Earth's
14:30North Pole
14:31leans toward the Sun
14:33Northern Hemisphere
14:34summers are sunnier.
14:40With unexpected
14:41consequences
14:42for the Sahara.
14:47It turns out
14:48at times
14:49when the climate
14:50in the Sahara
14:50gets more sunshine.
14:53That warms
14:54the climate up
14:54and the winds
14:56come in
14:56from the ocean.
14:58It's called
14:58the monsoon effect
14:59and brings water
15:00rain into the Sahara
15:02where now
15:03it's dry.
15:07This pattern
15:08of wet and dry
15:09climates
15:10that produce
15:11this 20,000 year cycle
15:12is what we see
15:13in the Sahara
15:14where at times
15:17of strong monsoon
15:18the Sahara
15:20is wetter
15:20a green Sahara.
15:2310,000 years ago
15:25as the Earth
15:25wobbled
15:26around the Sun
15:27monsoons
15:28were unleashed
15:29turning the desert
15:30green.
15:32Humans
15:33migrated
15:33to the newly
15:34lush Sahara
15:35and created
15:36the cave paintings
15:37we see today.
15:38But this
15:41wasn't the first
15:42time
15:42humans
15:43crossed
15:44a green Sahara.
15:48A dry Sahara
15:49would have presented
15:50an insurmountable
15:52barrier
15:52to our ancestors
15:54from migrating
15:55out of Africa.
15:57But during
15:57one of these
15:58cycles
15:59when
15:59the Sahara
16:00was green
16:01it would have
16:02been a corridor
16:03that we could have
16:04migrated
16:05and dispersed
16:05on.
16:05As the Earth
16:08traveled the Cosmos
16:10our planet's
16:11procession
16:11changed the Sahara
16:13and the fate
16:14of humankind.
16:16But
16:16there are more
16:17cosmic forces
16:18affecting our journey
16:19through the Universe.
16:22The Earth's orbit
16:23around the Sun
16:23is another thing
16:24that seems
16:25very, very solid.
16:26We understand
16:26how it works.
16:27But everything
16:28in the Universe
16:29is a delicately tuned
16:30dance of gravity
16:31and things can change
16:32even from tiny
16:33little influences.
16:35As our planet
16:37hurdles through space
16:39other worlds
16:40influence our path.
16:43Could a planetary
16:44bully
16:45push Earth's
16:46climate
16:46to the extreme?
17:00Earth carries us
17:02on a wild journey
17:03through the Cosmos.
17:04and clues
17:08to the effects
17:08of this trip
17:09are hiding
17:10in our own backyard.
17:22In New York City
17:23amongst the buildings
17:24and traffic
17:25we find moraines
17:28rocks left behind
17:31by retreating glaciers.
17:3818,000 years ago
17:39a sheet of ice
17:40taller than any
17:41skyscraper
17:42covered Manhattan.
17:45Ice ages
17:46have struck
17:47regularly
17:48throughout Earth's history
17:49putting our planet
17:53in a deep freeze.
17:54There was a period
17:58in Earth's history
17:59several hundred
18:00million years ago
18:01the snowball Earth
18:02period
18:03we went through
18:04a very extreme
18:05glaciation
18:06if you will
18:06a very extreme
18:07ice age
18:07where we think
18:08perhaps the entire
18:09Earth was covered
18:10in an ice sheet.
18:13The trigger?
18:16Earth's orbital dance
18:17around the sun.
18:18We tend to think
18:22of ourselves
18:23sitting relatively
18:24stationary on the Earth
18:25it's pretty comforting
18:25actually
18:26but we're orbiting
18:27the sun
18:28at about 66,000
18:29miles per hour.
18:32Every day
18:32Earth travels
18:33over 1.6 million
18:35miles
18:36on its journey
18:37around the sun.
18:39This orbit
18:40isn't always
18:41completely round.
18:42Earth is generally
18:48going around the sun
18:49in more or less
18:49a circular orbit
18:50but over time
18:52the massaging
18:54of this orbit
18:55from the sun
18:56from the moon
18:57on the Earth's orbit
18:58causes the orbit
19:00of the Earth
19:00to change
19:01so that sometimes
19:02it's an ellipse
19:03sometimes it's more
19:04of a circle.
19:07Right now
19:08on the Earth
19:09we're in kind of
19:09the most circular
19:10time in the orbit
19:12so that means
19:13the summers
19:14are relatively mild
19:14and the winters
19:15are relatively mild
19:16but imagine
19:17not that long ago
19:18in the past
19:19it could have been
19:19really dramatically
19:20different.
19:22When the Earth
19:23is a little bit
19:23closer to the sun
19:24maybe you have
19:26a really severe summer
19:28and then on the
19:29other side of the orbit
19:29you're a little farther
19:30away from the sun
19:31than normal
19:31so you have
19:32a really severe winter.
19:37Our environment
19:38is very, very
19:39sensitive to these things
19:40and when the Earth's
19:41orbit is stretched out
19:42that can actually
19:43trigger an ice age.
19:48Our planet's
19:49100,000 year
19:50orbital cycle
19:51caused the ice age
19:53that buried New York
19:54and ice ages
19:59have had a big effect
20:01on human history.
20:0415,000 years ago
20:06plunging temperatures
20:07locked water
20:08away in glaciers
20:09and ice caps.
20:11Sea levels dropped
20:13creating land bridges
20:15between continents.
20:17Humans migrated
20:18from Asia
20:19to America
20:20by foot
20:21and for the first time
20:23America
20:24was inhabited.
20:29May, 2018
20:30scientists revealed
20:33a whole new dynamic
20:34to Earth's journey.
20:38Every 405,000 years
20:40our planet's orbital voyage
20:43stretches to the extreme
20:44and Earth's planetary
20:46neighbors are to blame.
20:48because Jupiter
20:51is the most massive planet
20:53in our solar system
20:53it is in many ways
20:55the bully on the playground,
20:56right?
20:57Its dynamics,
20:58its gravity
20:58sculpts a lot of the dynamics
21:00of the solar system.
21:04It actually tugs and pulls
21:06on the orbit
21:06of the Earth itself.
21:08It's responsible
21:08for some of the very changes
21:10that drive our climatic cycle
21:12here on our planet.
21:12Jupiter isn't the only bully
21:17in the playground.
21:21Venus is a fairly big planet
21:22about the size of the Earth
21:23and also comes closest to us
21:25in its orbit.
21:26So these two planets
21:28put just a little tiny elongation
21:30onto our Earth's orbit
21:31and as this cycle continues
21:33the more extreme it gets
21:34we can actually notice
21:35a temperature difference
21:36that happens about
21:37once every 405,000 years.
21:42Jupiter and Venus
21:44gang up on Earth
21:45gravitationally
21:46pulling Earth's orbit
21:48into an even greater ellipse.
21:51Our planet's hot weather
21:53becomes hotter
21:54and its cold weather
21:55gets much colder.
22:02Today we're in a moderate
22:04part of the cycle
22:05but in just 60,000 years time
22:08we could plunge
22:09into another deep freeze.
22:12It's a little bit
22:14like a cosmic butterfly effect.
22:16I mean even the smallest effects
22:17can have, you know,
22:19big influence over time.
22:24Earth's orbit around the sun
22:26is just part
22:27of our far larger
22:28cosmic journey.
22:31The entire solar system
22:33is hurtling around
22:34the Milky Way
22:35taking us places
22:40we don't want to be.
22:42sometimes our planet
22:44might wander
22:45into what's essentially
22:47a bad neighborhood.
22:48What dangers await us
22:50and could these neighborhoods
22:51spell disaster
22:53for life on Earth?
22:54Over the last 3.7 billion years
23:12a series of extinction events
23:16wiped out almost 95%
23:18of all species on Earth.
23:20now research suggests
23:29our planet's orbit
23:30could be partly to blame
23:32but not the Earth's orbit
23:35around the sun
23:36our planet's larger
23:38and longer journey
23:39around the Milky Way.
23:42Our solar system
23:43and our sun
23:44is shooting through
23:45the galaxy
23:45at about 537,000 miles per hour
23:48around the center
23:49of our galaxy.
23:51And that center
23:52of the galaxy
23:52is about 26,000 light years away
23:54so it should take the sun
23:55about 230 million years
23:57to trace out
23:58one full orbit
23:59around the center
24:00of the galaxy.
24:00Despite racing around
24:04the Milky Way
24:05at half a million miles an hour
24:07Earth has completed
24:10less than 20 laps
24:11of the galaxy
24:12in our planet's
24:13entire history
24:14and it turns out
24:18this galactic ride
24:19is more complicated
24:21than it seems.
24:23Now if you look at the Earth
24:23going around the sun
24:24it defines an ellipse
24:26but that's a flat figure
24:28and you'd think
24:29well the sun
24:29probably goes around
24:31in a plane as well
24:32and it turns out
24:33not that simple.
24:37Most of the mass
24:38of the solar system
24:39is concentrated
24:40in the sun
24:41so Earth
24:43and the other planets
24:44smoothly orbit
24:45our star.
24:49But the mass
24:50of the Milky Way
24:51is spread out
24:53unevenly.
24:54That changes
24:56the gravity
24:57of the galaxy
24:57and so it changes
24:58how things move in it
25:00and in fact
25:01if you give something
25:01a little bit of an up
25:02or down motion
25:03it'll bob
25:04up and down
25:05as it goes around.
25:08Riding the Earth
25:08is almost like
25:09riding a carousel.
25:10As the sun
25:11and the Earth
25:12go around the galaxy
25:13the sun also goes
25:14up and down
25:15like you're on one
25:15of those horses
25:16with the pole
25:17and so what this can do
25:18is take us
25:20into different
25:21galactic environments.
25:24This bobbing motion
25:27takes Earth
25:28and the solar system
25:29on a 60,000 year journey
25:31up and down
25:32through the Milky Way's
25:34galactic plane.
25:37Our orbit also takes us
25:39through different
25:40galactic neighborhoods.
25:45Today we're traveling
25:46through a calm suburb
25:48of the galaxy
25:48but sometimes
25:51things get a little bumpy.
25:54sometimes our sun
25:57and our planet
25:58might wander
25:59into what's
25:59essentially
26:00a bad neighborhood.
26:01You know
26:02maybe it's an area
26:02where there's a lot
26:03of star formation
26:04going on
26:05where there's a lot
26:05of young stars
26:06that are very active
26:07or maybe it's a location
26:09where there are
26:10dying stars
26:11and things are about
26:12to get really hot.
26:14The baddest neighborhoods
26:15in the galaxy
26:16may be
26:17the spiral arms.
26:18These gas-filled regions
26:23orbit the galactic center
26:25more slowly
26:26than the Earth.
26:28So our planet
26:30passes through an arm
26:31roughly every
26:32150 million years.
26:34these arms
26:36are where
26:36gas clouds
26:37tend to hang out
26:39and if they get
26:40compressed
26:40they form a lot
26:41of stars.
26:43When they form
26:44a lot of stars
26:45they make bright
26:46blue stars
26:47and they don't
26:49last long
26:49and they blow up
26:50as supernovae.
26:51So it's possible
27:01that as we're
27:01passing through
27:02these regions
27:03these are places
27:04you might not
27:05want to be in.
27:07So in the distant past
27:08this may have
27:09affected the Earth.
27:15When giant stars
27:16go supernova
27:17the stars' outer layers
27:18blast into space.
27:21along with a shockwave
27:25traveling at 25,000 miles
27:27a second
27:27supernovas
27:32also release
27:33cosmic rays
27:34space bullets
27:38that shoot
27:38across the galaxy
27:39at close to
27:40the speed of light.
27:44And you don't
27:45want to be exposed
27:45to too many of them
27:46but in high enough
27:47doses
27:47these things
27:48penetrate our cells
27:49and damage our DNA
27:50and over the long term
27:51can cause really
27:53bad damage
27:54to human bodies.
27:56As we ride
27:57through space
27:58Earth's magnetic field
28:00protects us
28:01from most cosmic rays.
28:04But in 2018
28:06we discovered evidence
28:08that a hail
28:09of space bullets
28:10overwhelmed our planet's
28:12magnetic field
28:13in the past.
28:14in many ways
28:16we really take
28:17for granted
28:17how the Earth
28:18protects us
28:19from space
28:19but there are
28:21records that we've
28:21actually bounced
28:22a little too close
28:23to exploding stars.
28:26Sediments in the ocean
28:27show that about
28:28two million years ago
28:29Iron 60
28:31was deposited
28:31in our oceans.
28:33Iron 60
28:34is a radioactive isotope
28:35of iron
28:36and there's only
28:36one way we know
28:37of it being made
28:38in the universe
28:38and that is
28:39exploding stars.
28:40around 2.8 million
28:47years ago
28:47a supernova
28:48exploded
28:49just 150
28:50light years
28:51from Earth.
28:54A few hundred
28:55years later
28:55a blizzard
28:57of cosmic rays
28:58slammed
28:59into the Earth
28:59tearing through
29:01our magnetic field.
29:06These space bullets
29:07are a prime suspect
29:08in the extinction
29:10of over a third
29:11of all coastal
29:12marine species.
29:15Now this is not
29:17necessarily tied
29:18to the Earth
29:18passing through
29:19one of these
29:20spiral arms
29:20but it shows you
29:21that being close
29:22to a supernova
29:23is not necessarily
29:24a thing you want
29:25to do.
29:28Millions of years
29:29in the future
29:29Earth will pass
29:31through another
29:32spiral arm
29:33as our planet
29:34continues its journey
29:35through the Milky Way
29:37and we will
29:40wander into
29:41harm's way
29:42once again.
29:46But there's
29:47another part
29:47of our journey
29:48through space
29:49that remains
29:49a mystery.
29:51The Earth
29:52is spinning
29:53like a top
29:54on its axis
29:54it's orbiting
29:55around the sun
29:56the sun
29:57itself is orbiting
29:58around the center
29:58of the Milky Way
29:59but that's far
30:01from it.
30:01the Milky Way
30:04is speeding
30:04through the universe
30:05and we are being
30:07dragged along
30:08for the ride.
30:11The problem is
30:12we can't see
30:13where we're going.
30:15Could Earth
30:15be headed
30:16for a galactic crash?
30:31Like the craziest
30:33of theme park rides
30:35we are riding
30:36the Earth
30:37on a wild journey
30:38through the cosmos.
30:46Our planet spins
30:47tilts
30:48and wobbles
30:49around the solar system
30:50while bobbing
30:54like a carousel
30:55through the Milky Way.
30:58The dynamics
31:00of the Earth
31:01moving in the cosmic void
31:02is like
31:03the most
31:04unbelievable journey
31:05you could ever imagine
31:06and as you get
31:07to larger scales
31:08the motions
31:09only become
31:10grander and larger
31:11and more dynamic.
31:15In 1977
31:17we tried to work out
31:19the largest motion
31:20of all.
31:23The movement
31:24of our galaxy
31:25through the universe.
31:28Clues hide
31:28in the cosmic
31:29microwave background
31:30a remnant
31:31from the birth
31:33of the universe.
31:34The cosmic microwave background
31:36is the radiation
31:37that's left over
31:38from the hot Big Bang.
31:40The cosmic microwave background
31:41is shining
31:42in all directions
31:43and sort of
31:43this fixed thing
31:44and if we're moving
31:45through it
31:46with some speed
31:47we will see that
31:48in the light itself.
31:49You can measure that
31:50and by measuring that
31:51you can get a sense
31:52of how fast
31:52we're moving
31:53through that space.
31:55By tracking our movement
31:57through the universe
31:58against a fixed point
31:59we can work out
32:00the Milky Way's
32:01speed and direction.
32:06But in 1977
32:07telescopes
32:08weren't the best tool
32:10for the job.
32:12During the Cold War
32:141977
32:15you have the newly
32:16declassified U-2 spy plane
32:18this very high altitude
32:19reconnaissance aircraft.
32:21NASA retrofitted
32:22one of them
32:22with an upward facing window
32:24and with very sensitive receivers
32:26the spy plane
32:27became the first experiment
32:29to for the first time
32:31definitively measure
32:32the motion
32:32of the galaxy
32:33through the universe.
32:34As the U-2 spy plane
32:36soared above the earth
32:38it measured
32:38the cosmic microwave background
32:40in unprecedented detail.
32:45The data revealed
32:47that our galaxy
32:48races through the universe
32:50at 370 miles a second.
32:54That's over a million miles
32:58an hour.
33:03Think of how big
33:04a galaxy is.
33:06Hundreds of millions
33:07of stars
33:08and we're moving
33:09at hundreds of miles
33:11per second.
33:12That's just a tiny bit
33:14mind-blowing.
33:16The Milky Way's speed
33:18isn't the most alarming
33:19part of our galactic journey.
33:21From earth
33:23we can't even see
33:24in the direction
33:25our galaxy
33:26is taking us.
33:28We're flying blind.
33:29Our view
33:30is blocked
33:31by the Milky Way itself.
33:35So if you are actually
33:37looking through
33:37the plane of the galaxy
33:38through the plane
33:39of the pancake
33:40your view
33:41of the galaxy
33:42is obscured
33:43by curtains
33:44of dust and gas
33:45that envelop
33:45our solar system.
33:46It's very bright
33:48there's a lot of stars
33:49and our view
33:50is blocked
33:51by the galaxy itself.
33:53So there's a zone
33:54directly behind
33:55the galaxy
33:56as we look
33:56towards the galactic center
33:58that's really
33:59an unknown area.
34:00It's a zone
34:01we call
34:01the zone of avoidance
34:02and it's an area
34:03of really cosmic mystery.
34:07Thanks to this
34:08mysterious zone
34:09we thought
34:11we could be headed
34:12for a galactic car crash.
34:14Then
34:20we had a breakthrough.
34:28We used
34:29powerful radio telescopes
34:30to look through
34:32the zone of avoidance
34:33for the first time.
34:41One of the nice things
34:42about using light
34:43that's in the radio
34:45is that this kind of light
34:46actually can go through
34:47pretty dense kinds
34:49of gas
34:49and stars
34:50and allows us
34:51to sort of
34:51look through things.
34:53Using these radio telescopes
34:55has given us a glimpse
34:56into what lies beyond
34:57the zone of avoidance.
35:00Peering through
35:01the zone of avoidance
35:02we found
35:04that the Milky Way's path
35:05is clear
35:06but that's not all.
35:08We also discovered
35:09we are just
35:11one tiny part
35:12of a vast cluster
35:13of galaxies
35:14sailing through
35:15the cosmos
35:16together.
35:18We think that
35:18our galaxy
35:19the Milky Way
35:20is part of a much
35:21grander cosmic flow
35:23of galaxies
35:23and it is part of
35:25what might be
35:26the Laniakea
35:26supercluster of galaxies
35:28this giant
35:29giant cosmic structure
35:31filled with potentially
35:31thousands of galaxies
35:33that is moving together
35:34in this beautiful
35:35like slow-moving river
35:37that is sculpted
35:38and dictated
35:39and dictated
35:39by gravity itself.
35:42Earth voyages
35:44through space
35:45along gravitational rivers
35:46hundreds of millions
35:48of light years long
35:49along with a fleet
35:51of a hundred thousand
35:53other galaxies
35:54all moving toward
35:56a single point
35:57in space
35:57a gravitational drain
36:00known
36:01as the Great Attractor.
36:03The Great Attractor
36:06is the local
36:07region of gravity
36:10of strong gravity
36:11in this patch
36:12of the universe
36:13it's where
36:14all the galaxies
36:15in this chunk
36:16of the universe
36:16are flowing towards.
36:19At the location
36:21of the Great Attractor
36:22is a bunch of material
36:24a bunch of gas
36:24a bunch of galaxies
36:25an extremely
36:27massive cluster
36:28and over time
36:31more and more
36:32galaxies
36:33add themselves
36:34to this cluster
36:35as they continue
36:37to join
36:37the Great Attractor.
36:40It's unlikely
36:41Earth will ever
36:42reach the Great Attractor
36:44It seems
36:46the Milky Way
36:47is headed
36:48for a collision
36:49after all.
36:52Is this
36:53how our cosmic
36:54journey ends?
36:58Earth's voyage
37:07across the cosmos
37:08has lasted
37:09for 4.5 billion years.
37:17The big question
37:18how will our journey
37:20finally end?
37:24A clue comes
37:26from the Milky Way's
37:27traveling companion
37:28another galaxy
37:29Andromeda
37:30filled with up
37:35to a trillion stars
37:37that's charting
37:38a similar path
37:39to us.
37:44The Andromeda galaxy
37:46is another big spiral
37:47galaxy
37:48a lot like our Milky Way
37:49and it turns out
37:50the two of us
37:51are heading
37:52for each other.
37:54Andromeda
37:55and the Milky Way
37:56are currently
37:572.5 million
37:59light years apart
38:00but they're hurtling
38:02towards each other
38:03at over 250,000 miles
38:05an hour.
38:08A collision
38:09is inevitable.
38:12Galaxies colliding
38:13with each other
38:13sounds like science fiction
38:15but the collision
38:16of the Andromeda galaxy
38:18and the Milky Way galaxy
38:19will be a spectacular event.
38:20When the Andromeda
38:23and Milky Way
38:24galaxies collide
38:25it's going to be
38:25a ridiculous
38:26light show.
38:28The stars
38:29don't collide
38:30but the giant
38:31clouds of gas
38:32do
38:32and that's going to
38:33trigger star formation
38:34so we're going to have
38:36what's known
38:36as a starburst galaxy.
38:40When Andromeda
38:41finally merges
38:42with the Milky Way
38:43all bets are off.
38:44all of a sudden
38:46the system
38:46of hundreds
38:47of billions
38:48of stars
38:48will be added
38:49to our own
38:49and there will be
38:50mass chaos.
38:52But one thing
38:53you can guarantee
38:53there is going to be
38:55celestial fireworks.
38:56This could be
39:00the biggest
39:01light show
39:01in history
39:02resulting in
39:03the creation
39:04of a brand new galaxy.
39:07We will have
39:08become
39:09one giant galaxy
39:10call it
39:11Milkdromeda
39:12if you will.
39:14So we will look
39:14very different
39:15our grand design
39:17spiral Milky Way
39:18galaxy
39:18will have probably
39:19transformed itself
39:21into
39:22an entirely
39:23different shape.
39:26The merging galaxies
39:27could create
39:28a giant
39:29elliptical shaped
39:30galaxy
39:31but Earth
39:32might not be
39:33around to see it.
39:35Billions of stars
39:36are going to come
39:36careening into
39:37our galaxy
39:38very very easily
39:40disrupting the
39:40orbit of the Earth.
39:42The sun could be
39:43thrown out of
39:44the galaxy entirely.
39:49As stars,
39:50dust and gas
39:51swirl around
39:52each other
39:53gravitational
39:56interactions
39:57could slingshot
39:58our solar system
39:59out into
40:01intergalactic space.
40:07We will still orbit
40:09the sun
40:09and everything
40:09will be fine
40:10kind of
40:10but it just means
40:12we will see
40:12something very
40:13different in our sky
40:14in 4.6 billion
40:15years than we do
40:16now.
40:17Our planet
40:20could be sent
40:20on a whole
40:21new
40:22intergalactic
40:22ride
40:23shot out
40:26into the cosmos
40:27away
40:28from the new
40:29Milchromeda galaxy.
40:32There's no way
40:33of knowing
40:33exactly what's
40:34going to happen
40:35and in that sense
40:36journeys end
40:37we'll just have
40:42to wait
40:43and see.
40:47we might not
40:52know the final
40:53destination
40:53for Earth's
40:54cosmic journey
40:55but we do
40:57know this
40:57so far
40:58it has been
41:00an incredible
41:01ride.
41:02We've had
41:03a fantastic
41:03journey
41:04over the
41:05history
41:05of Earth's
41:06existence.
41:07We may not
41:08be immediately
41:09aware of our
41:10emotions
41:11through the
41:11universe
41:12but that
41:13doesn't mean
41:13they're not
41:13there.
41:14many people
41:17think of
41:18the Earth
41:18as this
41:19blue
41:19calm
41:20marble
41:20in space
41:20but in reality
41:24it's violently
41:25ripping around
41:25the sun
41:26and the sun
41:27is ripping
41:27about the
41:28galaxy.
41:31There's a lot
41:32of dynamics
41:32happening.
41:33It boggles
41:36the mind
41:36just to think
41:37of what
41:37the Earth
41:38will have
41:39done.
41:41The Earth
41:42will have
41:42actually
41:43orbited the
41:44sun
41:4410 billion
41:45times.
41:46It will have
41:46spun on its
41:47axis like
41:48a trillion
41:49times and
41:49the galaxy
41:50is moving
41:51through space.
41:55Riding the
41:56Earth is
41:56anything but
41:57a boring
41:58trip.
42:03гос
42:04Certbeard
42:05.
42:09.
42:09.
42:15.
42:20.
42:20.
42:20.
42:20.
42:20.
42:21.
42:24.
42:24.
42:24.
42:26.
42:27.
42:27.
42:27.