#CarlSagan covers a wide range of scientific subjects, including the origin of life and a #perspective of our place in the universe...
A 13-part #documentary #series that covers a wide range of #scientific #subjects, including the #origin of #life and a #perspective of our place in the universe narrated by famous American #Scientist – #Carl #Sagan.
A 13-part #documentary #series that covers a wide range of #scientific #subjects, including the #origin of #life and a #perspective of our place in the universe narrated by famous American #Scientist – #Carl #Sagan.
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LearningTranscript
02:59Invent the universe.
03:02Thank you very much.
03:05Suppose I cut a piece out of this apple pie.
03:10Crumbly, but good.
03:25And now suppose we cut this piece in half, or more or less, and then cut this piece in half.
03:38And keep going.
03:39And keep going.
03:40How many cuts before we get down to an individual atom?
03:45The answer is about 90 successive cuts.
03:51Of course, this knife isn't sharp enough, the pie is too crumbly, and an atom is too small to see in any case.
04:01But there is a way to do it.
04:05It was here at Cambridge University in England that the nature of the atom was first understood, in part by shooting pieces of atoms at atoms and seeing how they bounce off.
04:23A typical atom is surrounded by a kind of electrons.
04:32The electrons are electrically charged, as the name suggests, and they determine the chemical properties of the atom.
04:38For example, the glitter of gold, or the transparency of the solid that's made from the atom of silicon and oxygen.
04:50But deep inside the atom, hidden far beneath the outer electron cloud, is the nucleus, composed chiefly of protons and neutrons.
05:04Atoms are very small.
05:06A hundred million of them, end to end, would be about so big.
05:11And the nucleus is a hundred thousand times smaller still.
05:15Nevertheless, most of the mass in an atom is in the nucleus.
05:20The electrons are, by comparison, just bits of moving fluff.
05:27Atoms are mainly empty space.
05:30Matter is composed chiefly of nothing.
05:36When we consider cutting this apple pie, but down beyond a single atom,
05:43we confront an infinity of the very small.
05:48And when we look up at the night sky, we confront an infinity of the very large.
05:56These infinities are among the most awesome of human ideas.
06:01They represent an unending regress, which goes on not just very far, but forever.
06:09Have you ever stood between two parallel mirrors, in a barbershop, say, and seen a very large number of you?
06:20Or you could use two flat mirrors and candle flame.
06:29You would see a large number of images, each the reflection of another image.
06:38You can't really see an infinity of images, because the mirrors are not perfectly flat and aligned,
06:46and there's a candle or a candle flame, at least, in the way, and light doesn't travel infinitely fast.
06:51When we talk of real infinities, we're talking about a quantity larger than any number.
06:59No matter what number you have in mind, infinity is larger.
07:03There is a nice way to write large numbers.
07:11You can write the number 1,000 as 10 to the power 3, meaning a 1 followed by 3 zeros.
07:23Or a million is written as 10 to the power 6, meaning a 1 followed by 6 zeros.
07:34There's no largest number.
07:36If anybody gives you a candidate largest number, you can always add the number 1 to it.
07:41But there certainly are very big numbers.
07:43The American mathematician Edward Kasner once asked his young nephew to invent a name for an extremely large number,
07:5310 to the power 100, which I can't write out all the zeros on this page for, because there isn't room on the page.
08:02The boy called it a Google.
08:05If you think a Google is large, consider a Googleplex.
08:13It's 10 to the power of a Google.
08:16That is, a 1 followed not by 100 zeros, but by a Google zeros.
08:23Now, by comparison with these enormous numbers, the total number of atoms in that apple pie is only about 10 to the 26th.
08:36Tiny compared to a Google and, of course, much, much less than a Googleplex.
08:41The total number of elementary particles, protons, neutrons, and electrons, in the accessible universe is of the order of 10 to the 80th,
08:51a 1 followed by 80 zeros, still much, much less than a Google and vastly less than a Googleplex.
08:59And yet, these numbers, the Google and the Googleplex, do not approach.
09:05They come nowhere near infinity.
09:08In fact, a Googleplex is precisely as far from infinity as is the number 1.
09:17We started to write out a Googleplex, but it wasn't easy.
09:24It's a very big number.
09:38Writing out a Googleplex is a spectacularly futile exercise.
09:51A piece of paper large enough to contain all the zeros in a Googleplex couldn't be stuffed into the known universe.
09:59Fortunately, there's a much simpler and more concise way to write a Googleplex.
10:14Like this.
10:25And infinity
10:26can be represented
10:31like this.
10:33This is the Cavendish Laboratory
10:35at Cambridge University,
10:37where the constituents of the atom
10:39were first discovered.
10:41the realm
10:42of the very small.
10:46From the time of Democritus
10:48in the 5th century B.C.,
10:51people have speculated
10:52about the existence of atoms.
10:55For the last few hundred years,
10:57there have been persuasive but indirect arguments
10:59that all matter is made of atoms.
11:02But only in our time
11:04have we actually been able to see them.
11:06Here, the red blobs
11:09are the random,
11:11throbbing motions
11:12of uranium atoms
11:14magnified a hundred million times.
11:18How Democritus of Abdura
11:20would have enjoyed this movie.
11:22We pretty much take atoms for granted.
11:33And yet,
11:34there are so many different kinds.
11:37Lovely and useful
11:38at the same time.
11:41Look.
11:41There are some
12:1192 chemically distinct kinds of atoms naturally found on Earth.
12:16They're called the chemical elements.
12:35Virtually everything we see and know,
12:38all the beauty of the natural world is made of these few kinds of atoms
12:44arranged in harmonious chemical patterns.
12:48Here we've represented all 92 of them.
12:54Here we've represented all 92 of them.
13:09At room temperature, many of them are solids,
13:14a few are gases,
13:16and two of them, bromine and mercury,
13:19are liquids.
13:22They're arranged in order of complexity.
13:27Hydrogen, the simplest element, is element number one,
13:31and uranium, the most complex,
13:35is element 92.
13:37Some elements are very familiar.
13:44For example, silicon, oxygen, magnesium, aluminum, iron,
13:50the elements that make up the Earth.
13:51Or hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur,
13:56the elements that are essential for life.
13:58Other elements are spectacularly unfamiliar.
14:03For example,
14:05hafnium,
14:07erbium,
14:08diprosium,
14:10praseodymium.
14:13Elements we're not in the habit of bumping into in everyday life.
14:17By and large,
14:18the more familiar an element is,
14:20the more abundant it is.
14:22There's a great deal of iron on the Earth.
14:25Not all that much yttrium.
14:29The fact that atoms are composed of only three kinds of elementary particles,
14:34protons, neutrons, and electrons,
14:36is a comparatively recent finding.
14:39The neutron was not discovered until 1932.
14:42And it, like the electron and the proton,
14:45were discovered here,
14:46at Cambridge University.
14:47Modern physics and chemistry have reduced the complexity of the sensible world
14:54to an astonishing simplicity.
14:58Three units put together in different patterns
15:01make, essentially, everything.
15:11A neutron is electrically neutral,
15:15as its name suggests.
15:17A proton
15:19has a positive electrical charge,
15:23and an electron,
15:24an equal negative electrical charge.
15:27Since every atom is electrically neutral,
15:30the number of protons in the nucleus
15:32must equal the number of electrons
15:34far away in the electron club.
15:37The protons and neutrons together
15:39make up the nucleus of the atom.
15:41Now, the chemistry of an atom,
15:44the nature of a chemical element,
15:46depends only on the number of electrons,
15:49which equals the number of protons,
15:51which is called the atomic number.
15:53Chemistry is just numbers,
15:55an idea which would have appealed to Pythagoras.
15:58If you're an atom,
16:00and you have just one proton,
16:03you're hydrogen.
16:05Two protons, helium,
16:08three lithium,
16:10four beryllium,
16:11five protons,
16:12boron,
16:13six carbon,
16:14seven nitrogen,
16:16eight oxygen,
16:17and so on,
16:17all the way to 92 protons,
16:21in which case,
16:22your name is uranium.
16:24Protons have positive electrical charges,
16:27but like charges repel each other.
16:31So, why does the nucleus hold together?
16:34Why don't the electrical repulsion of the protons
16:36make the nucleus fly to pieces?
16:39Because there's another force in nature,
16:42not electricity,
16:43not gravity,
16:45the nuclear force.
16:47We can think of it as short-range hooks,
16:51which start working
16:52when protons or neutrons
16:54are brought very close together.
16:56The nuclear force
16:57can overcome
16:59the electrical repulsion of the protons.
17:02Since the neutrons exert nuclear forces,
17:05but not electrical forces,
17:08they are a kind of glue
17:09which holds the atomic nucleus together.
17:13A lump of two protons
17:17and two neutrons
17:18is the nucleus of the helium atom
17:20and is very stable.
17:23Three helium nuclei
17:25stuck together by nuclear forces
17:27makes carbon.
17:30Four helium nuclei
17:31makes oxygen.
17:34There is no difference
17:35between four helium nuclei
17:36stuck together by nuclear forces
17:38and the oxygen nucleus.
17:39They're the same thing.
17:41Five helium nuclei
17:43makes neon.
17:45Six makes magnesium.
17:47Seven makes silicon.
17:51Eight makes sulfur.
17:53And so on,
17:54increasing the atomic numbers by two
17:56and always making
17:58some familiar element.
17:59Every time
18:00we add or subtract
18:03one proton
18:04and enough neutrons
18:05to keep the nucleus together,
18:07we make a new chemical element.
18:09Consider
18:10mercury.
18:12If we subtract
18:14one proton from mercury
18:16and three neutrons,
18:18we convert it
18:19into gold,
18:21the dream
18:21of the ancient alchemists.
18:23beyond element 92,
18:28beyond uranium,
18:30there are
18:31other elements.
18:32They don't occur
18:34naturally on the earth.
18:35They're synthesized
18:36by human beings
18:37and fall to pieces
18:38pretty rapidly.
18:40One of them,
18:41element 94,
18:42is called plutonium
18:44and is one of the most
18:45toxic substances
18:46known.
18:48Where do the
18:49naturally occurring
18:50chemical elements
18:51come from?
18:52Perhaps
18:53a separate creation
18:55for each element?
18:57But all the elements
18:58are made
18:59of the same
18:59elementary particles.
19:01The universe,
19:02all of it,
19:02everywhere,
19:04is 99.9%
19:06hydrogen and helium,
19:07the two simplest elements.
19:09In fact,
19:10helium
19:10was detected
19:12on the sun
19:13before it was ever
19:13found on the earth.
19:15Might the other
19:16chemical elements
19:17have somehow
19:19evolved
19:20from hydrogen
19:21and helium?
19:22to avoid
19:25the electrical
19:25repulsion,
19:27protons and neutrons
19:28must be brought
19:29very close together
19:29so the hooks,
19:31which represent
19:32nuclear forces,
19:33are engaged.
19:35This can happen
19:35only at very high
19:36temperatures,
19:37where particles
19:37are moving so fast
19:39that there isn't time
19:40for electrical
19:41repulsion
19:42to act.
19:43Temperatures
19:44of tens
19:45of millions
19:46of millions
19:46of degrees.
19:48Such high temperatures
19:49are common
19:50in nature.
19:52Where?
19:53In the insides
19:54of the stars.
19:56atoms are made
20:13in the insides
20:14of stars.
20:15In most of the stars
20:16we see hydrogen nuclei
20:18are being jammed together
20:20to form helium nuclei.
20:21Every time a nucleus
20:23of helium is made
20:24a photon of light
20:25is generated.
20:27This is why
20:29the stars shine.
20:38Stars are born
20:40in great clouds
20:41of gas and dust
20:43like the Orion Nebula
20:441,500 light years away.
20:47Parts of which
20:48are collapsing
20:49under gravity.
20:58Collisions among the atoms
21:00heat the cloud
21:00until,
21:02in its interior,
21:03hydrogen begins
21:04to fuse into helium
21:05and the stars
21:07turn on.
21:14Stars are born
21:16in batches.
21:18Later,
21:18they wander
21:19out of the nursery
21:20to pursue their destiny
21:22in the Milky Way.
21:23Adolescent stars,
21:25like the Pleiades,
21:26are still surrounded
21:27by gas and dust.
21:29Eventually,
21:31they journey
21:31far from home.
21:37Somewhere,
21:39there are stars
21:39formed from
21:40the same cloud complex
21:42as the sun
21:42five billion years ago.
21:44But we do not know
21:46which stars they are.
21:48The siblings of the sun
21:49may,
21:51for all we know,
21:52be on the other side
21:53of the galaxy.
21:56Perhaps,
21:57they also
21:58warm nearby planets
21:59as the sun does.
22:04Perhaps,
22:05they too
22:05have presided
22:07over the evolution
22:08of life
22:09and intelligence.
22:14The sun
22:33is the nearest star,
22:36a glowing sphere
22:37of gas
22:37shining because
22:39of its heat,
22:40like a red-hot poker.
22:41the surface
22:47we see
22:47in ordinary
22:48visible light
22:49is at 6,000 degrees
22:50centigrade.
22:51But,
22:52in its hidden interior,
22:54in the nuclear furnace
22:55where sunlight
22:56is ultimately generated,
22:58its temperature
22:58is 20 million degrees.
23:00in x-rays,
23:11we see a part
23:12of the sun
23:12that is ordinarily
23:14invisible,
23:15its million-degree
23:16halo of gas,
23:18the solar corona.
23:20In ordinary visible light,
23:21these cooler,
23:22darker regions
23:23are the sunspots.
23:24They are associated
23:29with great surges
23:31of flaming gas,
23:33tongues of fire,
23:34which would engulf
23:35the earth
23:35if it were this close.
23:37These prominences
23:38are guided
23:39into paths
23:40determined
23:41by the sun's
23:43magnetic field.
23:44The dark regions
23:57of the x-ray sun
23:58are holes
24:00in the solar corona
24:01through which
24:02stream the protons
24:03and electrons
24:04of the solar wind
24:05on their way
24:06past the planets
24:07to interstellar space.
24:09All this churning power
24:14is driven
24:15by the sun's interior,
24:17which is converting
24:18400 million tons
24:20of hydrogen
24:20into helium
24:21every second.
24:23The sun
24:24is a great
24:25fusion reactor
24:26into which
24:28a million earths
24:28would fit.
24:30Luckily for us,
24:31it's safely placed
24:32150 million
24:34kilometers away.
24:39It is the destiny
24:54of stars
24:55to collapse.
24:58Of the thousands
24:59of stars you see
25:00when you look up
25:00at the night sky,
25:02every one of them
25:03is living
25:03in an interval
25:05between two collapses,
25:07an initial collapse
25:08of a dark interstellar
25:09gas cloud
25:10to form the star
25:11and a final collapse
25:13of the luminous star
25:14on the way
25:15to its ultimate fate.
25:17Gravity
25:17makes stars contract
25:19unless some other
25:20force intervenes.
25:22The sun is an immense
25:23ball of radiating hydrogen.
25:25The hot gas
25:26in its interior
25:27tries to make
25:28the sun expand.
25:30The gravity
25:30tries to make
25:31the sun contract.
25:33And the present state
25:34of the sun
25:35is the balance
25:36of these two forces
25:37an equilibrium
25:37between gravity
25:39and nuclear fire.
25:42In this long
25:43middle age
25:43between collapses,
25:45the stars
25:46steadily shine.
25:48But when
25:48the nuclear fuel
25:50is exhausted,
25:51the interior cools,
25:52the pressure
25:52is no longer enough
25:53to support its outer layers,
25:55and the initial collapse
25:56resumes.
25:58There are three ways
25:59that stars die.
26:00Their fates
26:01are predestined.
26:03Everything depends
26:04on their initial mass.
26:05A typical star
26:06star with a mass
26:07like the sun
26:08will one day
26:09continue its collapse
26:10until its density
26:12becomes very high.
26:14And then the contraction
26:15is stopped
26:15by the mutual repulsion
26:17of the overcrowded electrons
26:19in its interior.
26:21A collapsing star
26:22twice as massive
26:23as the sun
26:24isn't stopped
26:25by the electron pressure,
26:27and it goes on
26:28falling in on itself
26:29until nuclear forces
26:31come into play,
26:32and they hold up
26:33the weight of the star.
26:36But a collapsing star
26:37three times as massive
26:38as the sun
26:38isn't stopped
26:39even by nuclear forces.
26:42There's no force
26:43known that can withstand
26:44this enormous compression,
26:46and such a star
26:47has an astonishing destiny.
26:50It continues to collapse
26:51until it vanishes
26:53utterly.
26:54So every star
26:57is characterized
26:58by the force
26:59that holds it up
27:00against gravity.
27:00A star
27:01that's supported
27:02by the gas pressure
27:04is a normal
27:05run-of-the-mill star
27:06like the sun.
27:08A collapsed star
27:09that's held up
27:10by electron forces
27:11is called
27:12a white dwarf.
27:14It's a sun
27:15shrunk
27:16to the size
27:16of the earth.
27:18A collapsed star
27:19supported by nuclear forces
27:21is called
27:22a neutron star.
27:24It's a sun
27:24shrunk
27:25to the size
27:26of a city.
27:27And a star
27:28so massive
27:29that in its final
27:29collapse
27:30it disappears
27:31altogether
27:31is called
27:33a black hole.
27:34It's a sun
27:35with no size
27:36at all.
27:38But on their ways
27:39to their separate
27:40fates,
27:41all stars
27:41experience
27:42a
27:43reminiscence
27:44of death.
27:46Before the final
27:46gravitational collapse,
27:48the star
27:49shudders
27:50briefly swells
27:52into some
27:53grotesque
27:54parody of itself.
27:56With its last
27:57gasp,
27:58it becomes
27:59a red giant.
28:04Some five billion
28:05years from now,
28:07there will be
28:07a last
28:08perfect day
28:09on earth.
28:14Then,
28:15the sun
28:16will slowly change
28:17and the earth
28:19will die.
28:24There is only
28:25so much hydrogen
28:26fuel in the sun.
28:27When it's almost
28:28all converted
28:29to helium,
28:30the solar interior
28:31will continue
28:32its original
28:33collapse.
28:34The higher temperatures
28:35in its core
28:36will make the outside
28:37of the sun
28:38expand
28:38and the earth
28:39will become
28:40slowly warmer.
28:41eventually,
28:43life will be
28:44extinguished,
28:46the oceans
28:47will evaporate
28:47and boil,
28:49and our atmosphere
28:50will gutch away
28:51to space.
28:56The sun
28:57will become
28:57a bloated
28:58red giant star
28:59filling the sky,
29:02enveloping
29:03and devouring
29:04the planets
29:04Mercury and Venus
29:05and probably
29:07the earth
29:08as well.
29:09The inner
29:10solar system
29:11will reside
29:12inside the sun.
29:17But perhaps
29:18by then,
29:19our descendants
29:20will have ventured
29:21somewhere else.
29:27In its final
29:28agonies,
29:29the sun
29:30will slowly
29:30pulsate.
29:32By then,
29:33its core
29:33will have become
29:34so hot
29:35that it temporarily
29:36converts helium
29:37into carbon.
29:39The ash
29:39from today's
29:40nuclear fusion
29:41will become
29:42the fuel
29:42to power the sun
29:44near the end
29:44of its life
29:45in its red giant
29:46stage.
29:49Then,
29:50the sun
29:51will lose
29:51great shells
29:52of its outer
29:53atmosphere
29:54to space,
29:55filling the solar
29:56system with
29:57eerily glowing
29:58gas,
29:59the ghost
29:59of a star
30:00outward bound.
30:02Perhaps
30:03half the mass
30:03of the sun
30:04will be lost
30:04in this way.
30:07Viewed from
30:08elsewhere,
30:09our system
30:10will then resemble
30:11the ring nebula
30:12in Lyra,
30:13the atmosphere
30:14of the sun
30:15expanding outward
30:16like a soap bubble.
30:19And at the very
30:20center
30:20will be a white dwarf,
30:22the hot,
30:23exposed core
30:24of the sun,
30:25its nuclear fuel
30:26now exhausted,
30:28slowly cooling
30:29to become
30:29from a cold,
30:30dead star.
30:35Such is the life
30:36of an ordinary star,
30:38born in a gas cloud,
30:40maturing as a yellow sun,
30:42decaying as a red giant,
30:44and dying as a white dwarf
30:45enveloped
30:46in its shroud of gas.
30:48suppose as we traveled
30:59through interstellar space
31:01in our ship
31:02of the imagination,
31:03we could sample
31:04the cold,
31:05thin gas
31:06between the stars.
31:07We would find
31:08a great preponderance
31:10of hydrogen,
31:11an element
31:11as old
31:12as the universe.
31:13We would find
31:14carbon,
31:15oxygen,
31:15silicon,
31:16the most abundant
31:17atoms in the cosmos,
31:18apart from hydrogen,
31:20are those most easily
31:21made in the stars.
31:23But we would also
31:24find a small proportion
31:25of rare elements,
31:27praseodymium, say,
31:28or gold.
31:30They are not made
31:31in red giants.
31:32Such elements
31:33are manufactured
31:34in one of the most
31:35dramatic gestures
31:36of which a star
31:38is capable.
31:41A star more than
31:42about one and a half
31:43times the mass
31:43of the sun
31:44cannot be a white dwarf.
31:46It may end its life
31:47by blowing itself up
31:49in a titanic stellar explosion
31:51called a supernova.
31:55There has been
31:56no supernova explosion
31:57in our province
31:58of the galaxy
31:59since the invention
32:00of the telescope,
32:01and our sun
32:02will not become
32:03a supernova.
32:04But in our imagination,
32:07we can fulfill
32:08the dream
32:08of many earthbound astronomers
32:10and safely witness,
32:12close up,
32:13a supernova explosion.
32:14most of stellar evolution
32:21takes millions
32:21or billions of years,
32:23but the interior collapse
32:25that triggers
32:26a supernova explosion
32:27takes only seconds.
32:29Suddenly,
32:30the star becomes brighter
32:31than all the other stars
32:33in the galaxy
32:33put together.
32:34and if you are
32:38a supernova
32:38and you are
32:39into the sky
32:40and you are
32:41like,
32:41and you are
32:42of the stars
32:42and you are
32:42going to be
32:43a supernova
32:44on the galaxy.
32:44If the nearby star became a supernova,
33:13it would be calamity enough for the inhabitants of this alien system.
33:18But if their own sun went supernova,
33:20it would be an unprecedented catastrophe.
33:24Worlds would be charred and vaporized.
33:27Life, even on the outer planets, would be extinguished.
33:31In our ship of the imagination, we are now backing away from the star.
33:36But the explosion fragments, traveling almost at the speed of light,
33:39are overtaking us.
33:41Individual atomic nuclei, accelerated to high speeds in the explosion,
33:46become cosmic rays.
33:48This is another way that stars return the atoms they've synthesized back into space.
33:55The shockwave of expanding gases heats and compresses the interstellar gas,
34:01triggering a later generation of stars to form.
34:03In this sense also, stars are phoenixes, rising from their own ashes.
34:09The cosmos was originally all hydrogen and helium.
34:18Heavier elements were made in red giants and in supernovas,
34:22and then blown off to space,
34:24where they were available for subsequent generations of stars and planets.
34:28Our sun is probably a third-generation star.
34:33Except for hydrogen and helium,
34:35every atom in the sun and the earth was synthesized in other stars.
34:40The silicon in the rocks, the oxygen in the air,
34:43the carbon in our DNA, the gold in our banks,
34:46the uranium in our arsenals were all made thousands of light years away
34:52and billions of years ago.
34:54Our planet, our society, and we ourselves are built of star stuff.
35:02We're in a lava tube,
35:11a cave carved through the earth
35:14by a river of molten rock.
35:19To do a little experiment,
35:21we've brought a Geiger counter
35:25and a piece of uranium ore.
35:32Now, the Geiger counter is sensitive to
35:36high-energy charged particles, protons, helium nuclei, gamma rays.
35:42If we bring it close to the uranium ore,
35:45the count rate, the number of clicks, increases dramatically.
35:53We also have a lead canister here,
35:56and if I drop the uranium ore into the canister,
36:00which absorbs the radiation can cover it up.
36:04I then find the count rate goes down substantially,
36:09but it doesn't go down to zero.
36:13What's the source of the remaining counts?
36:15Well, some of them come from radioactivity in the walls of the cave,
36:21but there's more to it than that.
36:24Some of the counts we're hearing right now
36:25are due to high-energy charged particles
36:27which are penetrating the roof of the cave.
36:30Every second they are penetrating my body and yours.
36:41They don't do much damage.
36:43Cosmic rays have bombarded the Earth
36:45for the entire history of life on our planet,
36:48but they do cause some mutations,
36:51and they do affect life on the Earth.
36:53The cosmic rays, mainly protons,
36:59are penetrating through the meters of rock in the cave above me.
37:04To do this, they have to be very energetic,
37:07and in fact, they are traveling almost at the speed of light.
37:11Think of it.
37:12A star blows up thousands of light-years away in space
37:19and produces cosmic rays
37:20which spiral through the Milky Way galaxy
37:24for millions of years
37:26until, quite by accident,
37:29some of them strike the Earth,
37:32penetrate this cave,
37:33reach this Geiger counter,
37:35and us.
37:37The evolution of life on Earth
37:39is driven in part through mutations,
37:42by the depths of distant stars.
37:46We are, in a very deep sense,
37:49tied to the cosmos.
37:54Our ancestors knew this well.
37:57The movements of the sun, the moon, and the stars
38:00could be used by those skilled in such arts
38:03to foretell the seasons.
38:05So the ancient astronomers all over the world
38:08studied the night sky with care,
38:10memorizing and recording the position of every visible star.
38:15To them, the appearance of any new star
38:17would have been significant.
38:19What would they have made
38:21of the apparition of a supernova
38:23brighter than every other star in the sky?
38:27On July 4th, in the year 1054,
38:39Chinese astronomers recorded what they called
38:41a guest star
38:43in the constellation of Taurus, the bull.
38:46A star never before seen burst into radiance,
38:49became almost as bright as the full moon.
38:53Halfway around the world,
38:55here in the American Southwest,
38:59there was then a high culture,
39:01rich in astronomical tradition.
39:04They, too, must have seen this brilliant new star.
39:08From carbon-14 dating
39:11of the remains of a charcoal fire,
39:13we know that in this very spot,
39:15there were people living in the 11th century.
39:20The people were the Anasazi,
39:23the antecedents of the Hopi of today.
39:26And one of them seems to have drawn
39:28on this overhang protected from the weather
39:32a picture of the new star.
39:35Its position near the crescent moon
39:37would have been just what we see here.
39:39And the handprint is perhaps the artist's signature.
39:46This remarkable star
39:48is now called the Crab Supernova.
39:51Nova from the Latin word for new,
39:53and crab because that's what an astronomer
39:56centuries later was reminded of
39:57when looking at this explosion remnant
40:00through the telescope.
40:01The Crab is a star
40:03that blew itself up.
40:06The explosion was seen for three months,
40:08it was easily visible in broad daylight,
40:13and you could read by it at night.
40:17Imagine the night
40:19when that colossal stellar explosion
40:22first burst forth.
40:34A thousand years ago,
40:36people gazed up in amazement
40:38and looked at the brilliant new star
40:40and wondered what it was.
40:46We are the first generation
40:48privileged to know the answer.
40:50Through the telescope,
40:51we have seen what lies today
40:53at the spot in the sky
40:55noted by the ancient astronomers.
40:57A great luminous cloud,
41:00the remains of a star
41:01the star violently unraveling itself
41:03back into interstellar space.
41:11Only the massive red giants
41:13become supernovas,
41:15but every supernova
41:16was once a red giant.
41:18In the history of the galaxy,
41:20hundreds of millions of red giants
41:21have become supernovas.
41:23The bit of the star
41:27that isn't blown away
41:29collapses under gravity,
41:30spinning ever faster
41:32like a pirouetting ice skater
41:33bringing in her arms.
41:35The star becomes
41:36a single massive atomic nucleus,
41:39a neutron star.
41:41The one in the Crab Nebula
41:42is spinning 30 times a second.
41:44It emits a beamed pattern of light
41:46and seems to us
41:47to be blinking on and off
41:48with astonishing regularity.
41:50Such neutron stars
41:52are called pulsars.
41:56Neutron star matter
41:57weighs about a mountain
42:00per teaspoonful.
42:02So much that if I had
42:03a piece of it here
42:04and let it go,
42:06and I could hardly
42:06prevent it from falling,
42:08it would effortlessly
42:09pass through the Earth
42:10like a knife
42:12through warm butter.
42:14It would carve a hole
42:15for itself
42:16completely through the Earth,
42:18emerging out the other side,
42:19perhaps in China.
42:22The people there
42:23might be walking along
42:24minding their own business
42:25when a tiny lump
42:27of neutron star matter
42:28comes booming
42:29out of the ground
42:30and then falls back again.
42:32The incident might
42:33make an agreeable break
42:36in the routine of the day.
42:38The neutron star matter,
42:40pulled back
42:40by the Earth's gravity,
42:42would plunge again
42:43through the rotating Earth,
42:45eventually punching
42:46hundreds of thousands
42:47of holes before friction
42:50with the interior
42:50of our planet
42:51stopped the motion.
42:54By the time it's at rest
42:55at the center of the Earth,
42:56the inside of our world
42:57would look a little bit
42:59like a Swiss cheese.
43:01There are places
43:17in the galaxy
43:18where a neutron star
43:20and a red giant
43:21are locked
43:22in a mutual
43:23gravitational embrace.
43:26Tendrils of red giant star stuff
43:28spiral into a disk
43:30of accreting matter
43:31centered
43:32on the hot neutron star.
43:44Every star exists
43:46in a state of tension
43:48between the force
43:49that holds it up
43:50and gravity,
43:51the force
43:51that would pull it down.
43:53If gravity were to prevail,
43:55a stellar madness
43:56would ensue
43:57more bizarre
43:58than anything
43:59in Wonderland.
44:03Alice and her colleagues
44:04feel more or less
44:06at home
44:07in the gravitational
44:07pull of the Earth
44:08called 1G,
44:10G for Earth gravity.
44:12What would happen
44:13if we made the gravity
44:13less or more?
44:16At lower gravity,
44:17things get lighter.
44:18Near zero G,
44:19the slightest motion
44:20sends our friends
44:21floating and tumbling
44:22in the air.
44:23little blobs
44:24of liquid tea
44:25are everywhere.
44:26Curious.
44:28If we now return
44:29the gravity
44:30to 1G,
44:31it's raining tea
44:33and our friends
44:34fall back to Earth.
44:37I've been to a couple
44:38of parties like that
44:39myself.
44:42At higher gravities,
44:442 or 3Gs say,
44:45things get
44:46really laid back.
44:49Everyone feels
44:50heavy and leaden.
44:55Except by special dispensation,
44:59the Cheshire Cat.
45:01As a kindness,
45:03we remove them.
45:05At thousands of Gs,
45:07trees become squashed.
45:09At 100,000 Gs,
45:10rocks become crushed
45:12by their own weight.
45:13At all these gravities,
45:14a beam of light
45:15remains unaffected,
45:17continuing up
45:18in a straight line.
45:19But at billions of Gs,
45:21even a beam of light
45:22feels the gravity
45:23and begins to bend
45:24back on itself,
45:26curiouser
45:27and curiouser.
45:30Such a place
45:31where the gravity
45:31is so large
45:32that even light
45:33can't get out
45:34is called
45:35a black hole.
45:37It's a star
45:37in which light itself
45:38is imprisoned.
45:40Black holes
45:41were theoretical constructs
45:43speculated about
45:44since 1783.
45:46But in our time,
45:47we've verified
45:48the invisible.
45:50This bright star
45:51has a massive
45:52unseen companion.
45:54Satellite observatories
45:55find the companion
45:56to be an intense
45:57X-ray source
45:58called
45:59Cygnus X-1.
46:02These X-rays
46:02are like the footprints
46:04of an invisible man
46:06walking
46:07in the snow.
46:14The X-rays
46:15are thought
46:16to be generated
46:16by friction
46:17in the accretion disk
46:19surrounding the black hole.
46:21The matter in the disk
46:22slowly disappears
46:24down the black hole.
46:29Massive black holes
46:30produced by the collapse
46:32of a billion suns
46:33may be sitting
46:34at the centers
46:35of other galaxies,
46:36curiously producing
46:38great jets
46:39of radiation
46:40pouring out
46:41into space.
46:45At high enough density,
46:47the star
46:48winks out
46:49and vanishes
46:50from our universe,
46:52leaving only
46:52its gravity behind.
46:54It slips through
46:55a self-generated crack
46:56in the space-time continuum.
46:59A black hole
46:59is a place
47:00where a star
47:01once was.
47:03Here we have
47:04a flat
47:05two-dimensional surface
47:06with grid lines
47:08on it,
47:09something like
47:09a piece of
47:10graph paper.
47:12Suppose we take
47:13a small mass,
47:15drop it
47:16on the surface,
47:17and watch
47:17how the surface
47:18distorts
47:19or puckers
47:20into the third
47:22physical dimension.
47:27Gravity
47:28can be understood
47:29as a curvature
47:30of space.
47:33If our moving ball
47:35approaches
47:35a stationary distortion,
47:37it rolls around it
47:38like a planet
47:39orbiting the sun.
47:40In this interpretation,
47:42due to Einstein,
47:43gravity is only
47:44a pucker
47:45in the fabric
47:46of space
47:46which moving objects
47:48encounter.
47:49Space is warped
47:50by mass
47:51into an additional
47:52physical dimension.
47:56The larger
47:57the local mass,
47:58the greater
47:59is the local
48:00gravity,
48:01and the more
48:01intense
48:02is the distortion
48:04or pucker
48:05or warp
48:07of space.
48:08So,
48:09by this analogy,
48:10a black hole
48:11is a kind of
48:12bottomless pit.
48:15What would happen
48:16if you fell in?
48:17Well,
48:18assuming you could
48:18survive the
48:19gravitational tides
48:21and the intense
48:21radiation flux,
48:23it is just
48:24barely possible
48:25that by plunging
48:27into a black hole
48:28you might emerge
48:30in another part
48:31of space-time,
48:33somewhere else
48:34in space,
48:35somewhere else
48:36in time.
48:38In this view,
48:39space is
48:40filled
48:41with a network
48:42of wormholes,
48:44something like
48:44the wormholes
48:45in an apple,
48:46although by no means
48:47is this point
48:48demonstrated.
48:49It is merely
48:50an exciting suggestion.
48:52If it is true,
48:54then perhaps
48:56there exist
48:56gravity tunnels,
48:58a kind of
48:59interstellar
49:00or intergalactic
49:01subway,
49:02which would permit
49:03you to get
49:03from here to there
49:05in much less
49:05than the usual
49:06time,
49:07a kind of
49:07cosmic
49:08rapid transit
49:10system.
49:13We cannot
49:14generate black holes.
49:16Our technology
49:17is far too feeble
49:18to move such
49:19massive amounts
49:20of matter around.
49:22But perhaps
49:22someday,
49:23it will be possible
49:24to voyage
49:24hundreds or
49:25thousands of
49:26light years
49:26to a black hole
49:27like Cygnus X-1.
49:29We would plunge
49:30down to emerge
49:31in some
49:32unimaginably exotic
49:33time and place,
49:35our common sense
49:36notions of reality
49:37severely challenged.
49:41Perhaps the cosmos
49:42is infested
49:43with wormholes,
49:44every one of them
49:45a tunnel to somewhere.
49:47Perhaps other
49:48civilizations
49:48with vastly
49:49more advanced
49:50technologies
49:51are today
49:52riding the
49:54Gravity Express.
49:58It's even
49:59possible
49:59that a black hole
50:00is a gate
50:01to another
50:03and quite
50:03different universe.
50:04the
50:07sea
50:11has
50:13been
50:14to another
50:15and quite
50:16a bit
50:17of a
50:18picture
50:18.
50:18There
50:19is a
50:19far
50:20and
50:20there
50:20is a
50:21lot
50:22of
50:22other
50:23people
50:23who
50:23have
50:23to
50:24in
50:24the
50:25way
50:25to
50:26the
50:27world
50:28and
50:28you
50:28and
50:30the
50:31and
50:31have
50:31to
50:32the
50:32The lives and deaths of the stars seem impossibly remote from human experience,
50:49and yet we're related in the most intimate way to their life cycles.
50:54The very matter that makes us up was generated long ago and far away in red giant stars.
51:02A blade of grass, as Walt Whitman said, is the journey work of the stars.
51:08The formation of the solar system may have been triggered by a nearby supernova explosion.
51:13After the sun turned on, its ultraviolet light poured into our atmosphere, its warmth generated lightning,
51:20and these energy sources sparked the origin of life.
51:24Plants harvest sunlight, converting solar into chemical energy.
51:30We and the other animals are parasites on the plants, so we are, all of us, solar powered.
51:37The evolution of life is driven by mutations.
51:41They're caused partly by natural radioactivity and cosmic rays, but they are both generated
51:46in the spectacular deaths of massive stars thousands of light years distant.
51:51Think of the sun's heat on your upturned face on a cloudless summer's day.
51:59From 150 million kilometers away, we recognize its power.
52:05What would we feel on its seething, self-luminous surface or immersed in its heart of nuclear fire?
52:12And yet, the sun is an ordinary, even a mediocre star.
52:18Our ancestors worshiped the sun and they were far from foolish.
52:22It makes good sense to revere the sun and the stars.
52:25Because we are their children.
52:33We have witnessed the life cycles of the stars.
52:37They are born, they mature, and then they die.
52:42As time goes on, there are more white dwarfs, more neutron stars, more black holes.
52:47The remains of the stars accumulate as the eons pass.
52:52But interstellar space also becomes progressively enriched in heavy elements, out of which form
52:57new generations of stars and planets, life and intelligence.
53:03The events in one star can influence a world halfway across the galaxy and a billion years in the future.
53:17The vast interstellar clouds of gas and dust are stellar nurseries.
53:22Here first begins the inexorable gravitational collapse, which dominates the lives of the stars.
53:30Five suns may evolve through the red giant stage in only millions of years, dying young, never
53:36leaving the cloud in which they were born.
53:41Other suns, long-alived, wander out of the nursery.
53:45Our sun is such a star, as are most of the stars in the sky.
54:00Most stars are members of double or multiple star systems and live to process their nuclear
54:08fuel over billions of years.
54:11The galaxy is 10 billion years old, old enough to have spawned only a few generations of ordinary stars.
54:19The objects we encounter in a voyage through the Milky Way are stages in the life cycle of the stars.
54:33Some are bright and new, and others are as ancient as the galaxy itself.
54:38Surrounding the Milky Way is a halo of matter, which includes the globular clusters, each containing up to a million elderly stars.
55:01At the centers of globular clusters, and at the core of the galaxy, there may be massive black holes, ticking and purring, the subject of future exploration.
55:12We on Earth marvel, and rightly so, at the daily return of our single sun.
55:37But from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits.
55:44Not a sunrise, but a galaxy rise.
55:48A morning filled with 400 billion suns, the rising of the Milky Way.
55:54An enormous spiral form, with collapsing gas clouds, condensing planetary systems, luminous supergiants,
56:02stable middle-aged stars, red giants, white dwarfs, planetary nebulas, supernovas, neutron stars, pulsars, black holes,
56:13and, there is every reason to think, other exotic objects that we have not yet discovered.
56:19From such a world high above the disk of the Milky Way, it would be clear, as it is beginning to be clear on our world,
56:30that we are made by the atoms and the stars, that our matter and our form are determined by the cosmos of which we are a part.
56:41I only have a moment, but I wanted you to see a picture of Betelgeuse, that's what it's called,
56:54in the constellation Orion, the first image of the surface of another star.
57:00But the most exciting recent stellar discovery has been of a nearby supernova in a companion galaxy to the Milky Way.
57:07We are here witnessing chemical elements in the process of synthesis,
57:11and have had our first glimpse of the supernova through a brand new field, neutrino astronomy.
57:18And we're now seeing, around neighboring stars,
57:22disks of gas and dust just like those needed to explain the origin of the planets in our solar system.
57:29Worlds may be forming here.
57:32It's like a snapshot of our solar system's past.
57:36And there are so many such disks being found these days,
57:39that planets may be very common among the stars of the Milky Way.
57:44We are also seeing this pattern behind the stars of the planet to design this year.
57:49Let's see these photos, indeed.
57:52We're now seeing some amenities that we might be open for now.
57:54We're missing here, and first see, today docking people passage.
57:56We're wanting to see some fishes that will be generous for us.
57:59We're 1990 to do multiple distances.
58:01We're neiwiniwiniwiniwiniwiniwiniwiusa has been phenomenal.
58:03Hopefully if the Earth has been city buffaloes and the asteroid cap only visit me,
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