Cosmic Connections
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Lindau Nobel Laureate Meetings284 / 340
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00:00
Big Bang
00:27
Smoot, GeorgeParticle physicsSteckverbinderBig Bang nucleosynthesisLecture/Conference
00:59
DrehmasseBahnelementStalkingUniverseAstronomerLecture/Conference
01:24
BahnelementFaxNucleonBahnelementOrder and disorder (physics)Lecture/Conference
02:12
ElectronAtomic nucleusNeutronAtomEmission nebulaParticle physicsTypesettingNuclear transmutationRadioactive decayCurie, MarieProzessleittechnikRestkernNuclear fissionFusion powerNuclear fusionNuclear reactorBahnelementLiterary fragmentStarBookbindingIsotopeMassSource (album)SpaceflightBügeleisenNucleonParticleWasserwiderstandCrystal twinningNucleosynthesisReaction (physics)StagecoachRestkernScale (map)Gamow, GeorgeNeutronAtomic nucleusAmmeterPaperHoyle, FredBahnelementMassNuclear fusionGradientNuclear reactorH-alphaTiefgangNuclear fissionFusion powerHydrogen atomMeasuring instrumentNoise figureRRS DiscoveryGamma rayWoodturningBuick CenturyParticle physicsNucleosynthesisAlephElectronDampfbügeleisenRadioactive decayHourBeta particleScoutingAlpha particleNucleonOrbitBig Bang nucleosynthesisCurie, MarieProzessleittechnikRadiationBookbindingMotion captureRulerSpare partCamel (cigarette)HyperbelnavigationWolkengattungCoalSchwache LokalisationGreyUran-238PhotonicsMetreDayYearPositronOrbital periodSunlightGroup delay and phase delayRail profileMeasurement
07:37
Particle physicsAtomic nucleusCosmic distance ladderNuclear reactorHull (watercraft)Noise figureNeutronCoulomb's lawMoonBahnelementPunt (boat)LaserschweißenHydrogen atomRadiationHeatLightCash registerPhotonAutumnNuclear fusionMeasurementTemperatureMassSource (album)UltraBell LaboratoriesAstronomerFunkgerätDoorbellTelephoneMicrowaveCosmic microwave background radiationNucleosynthesisForceMembrane potentialNeutronOrder and disorder (physics)StarCosmic microwave background radiationCartridge (firearms)Perturbation theoryHalf-lifeSunlightFACTS (newspaper)Noise (electronics)Hydrogen atomBahnelementUniverseAtomic nucleusBeta particleRelative datingAutumnMinuteHot workingGround (electricity)ParticleTiefgangWoodturningMassPaperElectronRail transport operationsShort circuitAlcohol proofAudio feedbackLadungstrennungTemperatureDrehmassePhotonicsBending (metalworking)H-alphaRadioactive decayDensityRestkernEffects unitAlpha particleRadiationCogenerationNucleonMeasuring instrumentLecture/Conference
13:02
Big Bang nucleosynthesisUniverseNucleosynthesisSpare partStar clusterRadiationCrystal structureNuclear reactorPerturbation theoryGalaxyCosmic microwave background radiationSource (album)Atomic nucleusGround (electricity)Solar SystemMeeting/Interview
13:40
NeutronSource (album)Nyquist stability criterionMassNuclear fusionDensityTemperatureBig Bang nucleosynthesisBahnelementAir coolingQuarkGluonUniversePlasma (physics)NucleosynthesisBridge (nautical)RadioteletypeProzessleittechnikFormation flyingStarGalaxyParticleReaction (physics)UniversePerturbation theoryHose couplingStellar windTemperatureMinuteStarRoll formingNuclear reactorFuelBig Bang nucleosynthesisInterstellar mediumMassAtmospheric pressureForceDensityAtomismNuclear reactionGalaxyBand gapTypesettingBahnelementGround (electricity)MonthLastNucleosynthesisStar formationHydrogen atomBe starBird vocalizationCollision
15:47
Hydrogen atomHot isostatic pressingStarNuclear reactorNuclear fusionAlcohol proofDirect currentPositronSunlightBasis (linear algebra)Magnetic coreKette <Zugmittel>TypesettingYearAlcohol proof
16:29
MassStarSunlightFuelLuminosityStarHydrogen atomAtmospheric pressureMassYearNuclear reactionWhite dwarfRoter RiesePenPower (physics)Mechanical fanPlanetary nebula
17:22
StarFormation flyingBig Bang nucleosynthesisBahnelementStagecoachNucleonAtomic nucleusHoyle, FredResonance (chemistry)Field-effect transistorHydrogen atomSunlightResonance (chemistry)TemperatureRestkernStarAtmospheric pressureAngeregter ZustandComputer animation
18:17
StarHoyle, FredFormation flyingBig Bang nucleosynthesisBahnelementAtomic nucleusResonance (chemistry)Sauerstoff-16Reaction (physics)CannonMassNuclear fusionNuclear reactorNeon lampSiliconBügeleisenNucleosynthesisMassereicher SternCrystal structureRestkernNeutronCougarQuarryHull (watercraft)AmplitudeAmmunitionAdsorptionPlane (tool)Zeitdiskretes SignalAngeregter ZustandIsotopeGiant starProzessleittechnikYearAir coolingKontraktionMotion captureSupernovaMassRestkernDampfbügeleisenBeta particlePerturbation theoryMagnetic coreHydrogen atomRoter RieseBig Bang nucleosynthesisRemotely operated underwater vehicleStarTypesettingGamma raySauerstoff-16Nuclear fissionNuclear reactionIsotopeReaction (physics)BahnelementNeutronK-EinfangRadioactive decayNeon lampElektrostatische AufladungProzessleittechnikPaperGround stateFusion powerAfternoonThursdayNyquist stability criterionHose couplingBlack holeKugelhaufenEnergy levelSiliconTrajectoryElectronZeitdiskretes SignalSundayH-alphaGroup delay and phase delayNuclear reactorResonance (chemistry)Thrust reversalNeutroneneinfangNeutron starBridge (nautical)MonthAtomhülleUran-238SaturdayDensityContinuous trackAngeregter ZustandTemperatureStagecoachKontraktionCartridge (firearms)MorningRefractive indexFinger protocolLecture/ConferenceMeeting/Interview
23:39
StarNuclear fusionBahnelementNucleosynthesisMotion captureSupernovaNeutronExtra-vehicular activityLocal Interconnect NetworkKoaleszenzNuclear reactorThermodynamic equilibriumGround (electricity)MoonOrder and disorder (physics)MassPrintingFinger protocolBig Bang nucleosynthesisBahnelementProzessleittechnikEnergy levelThermodynamic equilibriumStellaratorNucleosynthesisDampfbügeleisenAtomic nucleusMaterialStarCosmic rayMassEffects unitDashboardGalaxyDensityYearTypesettingSpallationSolar SystemIsotopeFACTS (newspaper)Motion capturePrintingMoving walkwayLiterary fragmentSpantKopfstützeCross section (physics)VideoMagnetarHochbahnNatürliche RadioaktivitätHydrogen atomr-ProzessHot workingProgressive lensSauerstoff-16NeutronNuclear physicsAmplitudeSupernovaGradientGameNuclear reactorAmateur radio repeaterBerlin (carriage)Packaging and labelingLecture/ConferenceEngineering drawing
27:56
Planetary nebulaSchwefelatomHydrogen atomGasWolkengattungTypesettingCylinder blockPlanetary nebulaPackaging and labelingStarVisible spectrumStellar windComputer animationLecture/Conference
28:42
Ford OrionObservatoryBrightnessSupernovaBahnelementSupernovaSkyGenerationRelative articulationJupitermondSatelliteFinger protocolMagnetic coreWolkengattungVideoStarOrder and disorder (physics)BahnelementPlanetGasWater vaporX-ray
29:40
RadiationSupernovaUniverseRadioactive decaySatelliteSemi-finished casting productsHalf-lifeScale (map)SupernovaGamma rayNuclear explosionLight curveSkyPower (physics)Plane (tool)YearGalaxyGround (electricity)Impact eventRemotely operated underwater vehicleCosmic rayEisengießerei
30:41
Atomic nucleusGalaxySunriseCell (biology)Sedan (automobile)Sauerstoff-16Swimming (sport)MoonHydrogen atomQuasarSeries and parallel circuitsPhase (matter)QuarkFormation flyingAtomKilogramCosmic rayGalaxyAtomismScale (map)Order and disorder (physics)MinuteBig Bang nucleosynthesisDampfbügeleisenSeries and parallel circuitsNeutronFACTS (newspaper)Impact eventTheodoliteYearBahnelementTurningAngle of attack
31:42
Dark matterNeutrinoStarHydrogen atomUniverseMassBahnelementDark matterUniverseSteckverbinderHydrogen atomStarSpare partFinishing (textiles)Computer animation
32:20
McDonnell F-101 VoodooVideoNanotechnologyElectric power distributionCommercial vehicleMaterialLecture/ConferenceComputer animation
Transcript: English(auto-generated)
00:37
So in that opening scene for the Big Bang Theory, there are implied cosmic connections.
00:43
There's the Big Bang, and then suddenly all of history happens. And so I thought that was a reasonable opening. Also, it's my favorite TV show. But anyway, so I'm going to talk about the cosmos, nuclei, the elements, chemistry, and life.
01:03
And they're all intimately connected, and we'll see why that is. And so the main points I'm trying to get across to you is the answers to some big questions. Where do the elements come from? No elements, no chemistry. So what can we learn from telescopes about chemistry?
01:21
And about the origin of the elements? And how do the heavy elements form? That was sort of a question. Now to an astronomer, heavy elements are anything heavier than helium. They call them metals in astronomy. Okay, I was going to title this talk alchemy of the universe, or just alchemy.
01:42
But somehow I'm on chemist's alchemy has a bad name. I'm going to try and convince you that was from medieval times and the modern times we actually think about alchemy as a serious things. And there's a chart here of the elements, which I happen to have. We make this in Berkeley. I happen to have one of these as a placemat, or two of these as a placemat.
02:03
I eat breakfast or dinner on it sometimes in order to keep the table clean. And I like it because they have a picture of what the real elements look like. Okay, so just to remind you, when you're doing ordinary chemistry, you usually think about an atom, which has a nucleus you don't worry about for
02:22
the most part, and then there's orbitals of electrons shown here as circles, but we know they're clouds, and that's on the scale of 10 to the minus 10 meters. Whereas when we talk about the nuclei, that is what the things that make up the elements, the number of protons, or the number of protons and neutrons for each of the isotopes, that's on the scale of 10 to the minus 14 meters. And this is one of the things we see happen in physics.
02:42
Things are in very different scale, so that you can actually just work at one scale and know pretty much just worry about that scale and not worry about high energy scales or lower energy scales. This is the scales you have to worry about. Okay, so modern alchemy starts the turn of the last century with the discovery of radioactivity, and particularly Pierre and Marie Curie.
03:06
She happened to be one of my scientific heroes when I was young. And if I get the chance to live down the road from her laboratory, I got to know a prize immediately after that. I got invited to her lab, and I got to sit on her desk, and
03:20
then they told me it was radioactive. And it was, because there were instruments here, you could see it. So during that early time period, they discovered alpha, beta, and gamma radiation. The alpha radiation turns out to be helium nuclei, and you'll see that's a common thing when you're actually doing alchemy.
03:42
The beta radiation was actually electrons or sometimes positrons, and the gamma radiations are energetic photons at the energy scale. And Marie Curie, by the way, got two Nobel Prizes, so one in physics, one in chemistry, so she did well, okay? All right, so the big issues in modern alchemy,
04:01
we call them nuclear fusion and nuclear fission. And fission is when you take a very heavy nucleus, and it splits apart into lighter nuclei and usually some residual parts, because you have more neutrons than you need for the lighter elements. Fusion is the opposite process when you take light nuclei and merge them together to get a heavier nuclei, okay?
04:22
So the thing that's critical here, it's a typical kind of thing in physics or chemistry kind of thing, is the binding energy of the per nucleon as a function of the mass number of the nucleus. And you can see it starts out with hydrogen being very low, because hydrogen has either one proton or a proton and a neutron.
04:41
It's quite low, and if you merge hydrogens together, four hydrogens together to make a helium, you get a tremendous amount of energy, because helium is tightly bound, right, at the binding. So that's the yield we get from nuclear fusion. If you go to very heavy elements like uranium-238, right, there is the repulsion of all those protons being held close together.
05:03
And that makes it so that by breaking it into lighter elements, typically around 120 mass units, 118 mass units, you can get amount of energy that's shown there. And so that's what fission is famous for. The important thing to note here is that the iron group,
05:22
which is iron and nickel and so forth, those nuclei, the even-even nuclei, they're the most tightly bound nuclei. And that means we have to break up nuclear synthesis or alchemy into four different criteria when I'll go through those. Okay, just for the people who are going to the discussion section or
05:41
what I would do if I had an hour talk, I have quizzes, right? You just saw that one. Now you gotta figure out which reasons a fission happened and so forth. You should remember that it's very good. You'll notice it. I have some of my other things, but we won't have the quizzes. Okay, so let's get down to the first big question. What's the origin of the elements?
06:01
And there were two competing theories, just like there were two competing people. George Gamow and Fred Hoyle had debates with each other, and they had a long running fight about how the elements came into existence. And so Gamow had a grad student named Alpha, and he started to work them on this problem for his thesis in late 47, early 48.
06:25
And they started putting together a paper that says we're gonna make all the elements in the Big Bang. And we're gonna do it by having a cold Big Bang, and we're going to just have a sea of protons and neutrons, and they will capture each other and start building up the elements, and
06:42
there's some beta decay. And so Gamow not only did like the fight with Hoyle, he had a sense of humor, and he realized the alpha and gamma paper would be much better if it was alpha, beta, gamma paper, just like the radiation. So they invited Hans Bethe to be a co-author in this paper,
07:02
once they had the first draft. Now Alpha wasn't so happy about it, he was a grad student. He was afraid that having two famous authors on him, he would be overlooked. However, the interesting thing about Bethe is that he lived to 90, and he published papers for 70 years, and
07:21
he had at least one important paper every decade for seven decades. However, when he was young and in Germany, he once went out on a date, a hike up in the Alps for the picnic. And they had their picnic lunch out in the meadow, and they lay down in the sun, and were saying romantic things or something like that. And Bethe is looking up at the sun, and he sits up and
07:42
he says, I know what makes the sun shine, I know what makes the stars work, right? His date was not impressed, but he ended up writing some papers, and that's the things that really led to what's going on. And he actually contributed to the paper in the second draft and so forth, and pushed on this kind of stuff.
08:02
Now that, you'll see in a moment, fails, we'll see why. But it was an interesting way, and it took Hoyle a long time to come up with a competing thing. And Burbage, Fowler, and Hoyle put out a paper that was very substantial and complete in 1957, where they tried to make all the elements in
08:25
the stars, where they were originally trying to make all the elements in the stars, they ended up making all the heavier elements in stars. And so, Gamow still gave Hoyle trouble. He said, we get a 99 on our paper, because 99% of the mass in the universe we've explained, and you've only explained 1%, right?
08:43
That's a very important 1%, though. Okay, so how are we gonna distinguish between which of these theories was right? The answer is, we've got to do some nuclear properties experiments. So the first thing is, just look at the nuclear potential, right? The electrostatic potential, the thing that does most of the chemistry,
09:01
holding electrons on, has a 1 over r squared force. And you have that, if you have a proton or a charged nuclei you're trying to hit another nuclei with, you have a potential barrier of the conclusion. So in order to get there, you have to tunnel through that barrier, or you have to have enough energy to get over that barrier, and somehow lose energy and fall in the potential well of the nucleus.
09:22
The nucleus, the nuclear force is a short range force. It is essentially a local force with an exponential tail, right? A very short exponential tail. However, if you send in a neutron, right? So that's coming in from the other side. The neutron has no electric charge. So the neutron just goes along till it gets near the nucleus, and
09:44
it gets sucked in, and then it can just adhere. And if the right thing to do is to emit a beta neutrino and turn into a proton, that's how you go up in z and get the heavy elements, right? And that was Gamow's original idea, and
10:00
that's what he was sending Alpha to start calculating into. And he was so excited about it, he wrote that first paper. However, as soon as they did the studies, they realized that didn't work. And so, but this just tells you why when you make heavier elements than helium, you have to be hot, and in fact, in stars, you have to have a hot
10:21
dense situation in order to get the protons together to be nuclear bound, or to get them into another nucleus. Oops, okay, so there's lots of details on the left. You can see that in the replay. What it turns out is if you realize when you do the calculation, that doesn't work.
10:41
The universe is expanding, and you need to put some protons together because the neutrons decay with a half life of about ten minutes. So you've gotta get all this chemistry, alchemistry done early. And so what they figured out, eventually there's feedback back and forth. The one thing that sort of agrees with the observation we have today is if
11:03
that the universe was hot enough to smash protons together or to smash nuclei together, then in order to explain what you see in protons, helium-4, deuterium, helium-3, and lithium-7, you need to have left over now essentially a few billion photons for every nucleon.
11:26
So that's a ratio that they predicted. They didn't predict it so accurately back in 48, but they did do a first case. And they did first predict there would be a radiation at 20 Kelvin, then they predicted there would be a 5 Kelvin. As you will know, we later on showed it was at around 3 Kelvin.
11:44
Okay, and so here's the plot when you put that information in. On the top is the number of minutes since the beginning of the universe. On the bottom is the temperature and billions of Kelvin. And what you see is the hydrogen doesn't change very much until you get close to three minutes.
12:01
Then some of the hydrogen gets turned into helium. And a little bit of leftover stuff is turned into the somewhat, the other light elements and so forth. And you see you first make some deuterium, and that deuterium gets eaten up, turned into alpha particles and so on to helium.
12:20
And so this is a calculation. It's all over in a very short time. Okay, well, this led to people eventually to looking for this relic radiation. Although it turns out, Fincus and Wilson were doing another experience. They saw this effect. They follow the advice. They pre-follow the advice of some of the Nobel laureates that preceded us. And they looked very carefully at this,
12:41
and they realized it was fundamental something coming from the universe. And then the people from Princeton explained where it was. And so that's the point of being a careful experimenter and then understanding what this unusual result was that you got. Several other people had seen this, but sort of wrote it off as instrument noise or something. But Fincus and Wilson did the right job.
13:02
Okay, so they found that relic radiation from the hut, from the early Big Bang nuclear synthesis. That was followed up. As mentioned, John Mather and I shared the Nobel Prize in 2006. And we shared it for two parts. Showing that radiation truly came from the beginning of the universe and then showing that radiation was extremely uniform to a part in 10,000.
13:26
But at the part in 10,000, related to part in 100,000, there were small perturbations that are later on gonna be the source of structures in the universe, that is, galaxies and clusters of galaxies, but also stars and planets, which turned out to be interesting to us.
13:41
Okay, so what about Big Bang nuclear synthesis? How does it look? Well, it occurred doing approximately the first three minutes. You saw it was all done by five minutes. It was just tailing off, right? And it stopped because the universe keeps expanding, the density goes down, and the universe is cooling. So no longer do you have the energy to actually, things to do.
14:01
So it correctly explains the 75% of the mass being helium and 23%, I mean, being hydrogen, 24% being helium, and some trace elements. The other 1%, that turns out that Hoyle was pretty close to right about. And so you have these sort of chemistry charts,
14:20
and what you have here is a couple set of differential equations in an expanding universe. They're first order differential equations, straightforward, you could do the calculations. And the other thing that you find out is there's a blockage of building things up quickly because there's a mass gap at atomic number, not atomic number, mass number of five
14:41
and a mass number of eight. And that actually slows you down from getting any higher. So even though they got a 99, they missed the 1% that's really critical. The 1% is essentially, everything in this room is made out of the 1%. Okay, so after that primordial nuclear synthesis, nothing happened for a long time
15:01
because the temperature and the density of the universe was too small to make new elements, right? You need high density to make the collisions, you need high temperature to overcome the Coulomb force. So we had to have the galaxy and star formation, right? We had to have the coalescence, we had to get the gravitational pressure
15:21
to be so high as to make the temperature hot in the center of stars, and then we can start to have nuclear reactions. Okay, so the stellar cycle is pretty straightforward. You have some interstellar gas that collapses, forms a hot star, gets hot enough in the center, you get thermonuclear ignition,
15:40
and that goes on until the fuel's burned up and the star explodes. Meantime, it also sends some stuff out in stellar winds. So here's our sun. It operates on the core at about 16 million degrees, and here's two little protons having a good time for about a billion years, and then they happen to run into each other finally,
16:01
and they form H2 by emitting a positron and a neutrino, and that gives you deuterium, and another proton gives you, well, either tritium or helium-3, depending on which directions you go, and the helium-3 then merges to make helium-4.
16:21
There's a whole set of chains here that you can figure out, and this is the basis of what keeps our sun burning. It keeps our sun burning for quite some time. Here's the life cycle of the sun, right? It was born four and a half billion years ago. We're a long way away. It's gonna be gradually warming over the next four billion years
16:41
and will turn into a red giant, and then the planetary nebula, that is, it'll throw out these stellar winds, and then it'll turn into a white dwarf, right? So until the hydrogen fuel is depleted, the lifetime of our sun depends strictly on nuclear reaction rates, and that's just set by the mass of the sun and the pressure and so forth. The lifetime of stars depends on their masses,
17:02
and the larger masses burn more quickly, so we're lucky, or it's not an accident we're in a star that's gonna last a long time. If the mass of the sun was 10 times larger, it would be over in 10 million years instead of 10 billion years, right? Because it goes to the cube, right? It actually, the luminosity goes to the fourth power, the math, therefore the lifetime goes to the cube.
17:23
Okay, so what about the star that's bigger than the sun? When it burns up the helium, it eventually poisons, burns up the hydrogen helium, eventually poisons the center of the star, and then the nuclear burn doesn't go so well, but if the pressure and the temperature is high enough on a more massive star, you can actually burn carbon,
17:41
but this is tricky because you try and run two helium nuclei together to make carbon, and what happens is that's beryllium-8. Beryllium-8 has a lifetime of 10 to the minus 16 seconds that falls apart before the next helium can come to make carbon-12, right? So how do we make carbon-12? Well, Fred Hoyle, a hero, anti-hero in the last thing,
18:03
he was thinking about the problem because he was so motivated to beat Gamow. He realized that you needed to have three bodies come together, that is, the three heliums had to come together essentially simultaneously, and there had to be a resonance in carbon-12, an excited state of carbon-12, that was the three helium nuclei mass
18:23
plus a little bit of kinetic energy, and then it could emit a gamma ray and decay into the thing, and so he flew from England to visit at Caltech. He arrived overnight on a Thursday morning, gave a talk Thursday afternoon. Willy Fowler's group, I heard this from a postdoc, Willy Fowler's group put together an experiment.
18:41
They had run it by Saturday, and Sunday they were writing the paper that they found the resonance inside, so it was amazing, and that was the key step to allow the Burbage, Burbage, Hoyle and Fowle kind of thing, and it set Willy Fowler on the trajectory that caused him to get the Nobel Prize because he realized that doing nuclear reactions
19:01
for cosmology and astrophysics was important. Okay, so the next kind of thing that happens in stars is helium burning, and that's important to get the continued helium burning, a helium, it's called the alpha cycle. If you add the carbon-12, the helium-4, you get oxygen-16 plus a gamma ray. You actually burn up some of the carbon,
19:20
so fortunately the reaction rate's relatively slow, so some carbon is left so we can have life. So here's a chart of helium plus carbon-12, making oxygen, oxygen plus helium, making neon, neon making magnesium, and so forth. That's how we build up, and you have to know that just like electron levels,
19:41
they're nuclear levels that way, even-even nuclei are more tightly bound than odd-even nuclei or odd-odd nuclei. And there are other reactions where you can burn carbon plus oxygen and get silicon-26. You can burn oxygen and oxygen and get sulfur-31. You can burn the silicon together and make the iron.
20:02
And then you're kinda done, right? But so if you look at a star as it burns along the way, it was made mostly of hydrogen and some helium, but it gets a set of shells, like an onion, where the heavier elements are in the center because the electrostatic repulsion requires that, but they also burn faster. They require higher density, higher temperature,
20:22
but they also get there more quickly, okay? So how do we get the heavier elements, right? Once we get the iron, it costs us energy to make heavier elements, right? And so the fusion normally would stop in a star. And so what happens is the star's gotta die. It has to have a core collapse. Generally, you form a black hole
20:41
or perhaps a neutron star, but you get a big outflux of neutrons and you get neutron capture, right? And so this is number of neutrons that way, number of protons that, sorry, neutrons that way, protons that way. And the only other stable thing is neutron stars that are way off to the right, right? And so how do you get there?
21:01
Well, the answer is you have to blow the core of the star up and send out a huge slug of neutrons and a little bit of protons and start capturing those neutrons and beta decay them and walk up the valley of stability to make the heavier elements. And so here is one of the early papers saying, here's what happens.
21:20
You have this path that you follow as you keep absorbing neutrons because you get neutron heavy and then you beta decay and there's some bottlenecks for it last a half a second or in one case, two seconds and so forth, but you're getting back over by decays over to the valley of stability. And this is pretty complicated, but this is the original idea that gamma had of how to make all the elements, right?
21:42
So you're putting together big bang nuclear censuses, you know, fusion and then neutron capture to get to the heavier elements. Okay, and here's an example from Germany of one of the red giants at the later stage, starting with iron and capturing neutrons and you see how it walks up and there's multiple paths. So again, you have this first order
22:03
differential equation, couple set and do that. But the other thing is to remember, just like in chemistry, they're discrete states, right? We, there are only certain isotopes that exist that stay there, right? You may have some temporarily, but generally very quickly, you end up in one of the stable ones.
22:20
And so here's a chart of why it's that way. This is the energy state, the ground state energy as a function of the isotope. And you can see up here at the far end where you're up at the uranium, it's quasi stable. It will decay by fission or by other processes, right? So this is the kind of thing you're,
22:41
this is the reverse of the binding curve. This is thinking about the potential energy and thinking what things can castate down. Okay, and here's from the original Burbage, Burbage, Fowler and Hoyle paper. Here's a chart of saying, what does it take to make the elements in the stars? You spend 10 billion to nine, you know, to 100 million years, hydrogen burning.
23:02
Then you have the core contraction, you do helium burning. And then you have the slow process of capturing protons or other things. Then you have the alpha burning process. And then you have the electron capture or decay. And then you have the fast or the slow process of capturing neutrons as they go out. And it's a crescendo and then it collapses
23:22
and the star starts cooling because it's exploded and it's allowed to do that. Now this is very close to correct, right? That 57 paper got all of them broad strokes right. So the elements are now created in three ways that I'll explain in one more way that I will try to explain. That is the light elements are made
23:42
in the primordial cosmological big bang nucleosynthesis. Stellar nucleosynthesis makes the elements up to iron as we'll see. It actually makes them in what we call statistical nuclear equilibrium. That is, if you just know the energy levels and you know the process, you can,
24:00
if you know the statistical factors and the E to the minus E or KT factor, the Wilson factor, you just put them all together and you predict what the things are and you get pretty close to the correct answer. Then you have to have the destruction of a star, the explosive nucleus elements where you have capture of neutrons primarily but occasionally protons
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and these happen generally in supernova. And there's one more process that I'll talk about briefly here because when I was the age of most of the young scholars here, it was one of the experiments that I did. And it's galactic nucleosynthesis of elements by cosmic ray spallation. So it takes a huge set of, it's a long complicated problem, it takes a huge set of things.
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So here is the solar system abundance. And you can see it goes many orders of magnitude. You'll notice lithium, beryllium and boron are very rare. It's because they're fragile elements and they get burned up in stars and not so much was made in the Big Bang and so you have to be making them and you will notice the odd even
25:02
but the odds are a little more populated than you would have expected from the calculations of what goes in stars and the explosions of stars. And that's due to the effect of cosmic rays on the galaxy. So one of the experiments I did was to measure the element of abundance in galactic cosmic ray when I was a young postdoc
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and you'll notice that the abundance I showed you before is the dash line and above what you see in cosmic rays. Now cosmic rays travel through the galaxy and they go through the hydrogen and a little bit of helium gas that's in the galaxy and occasionally they have an interaction and they fragment. And they therefore fill in, see below iron peak,
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they fill in those elements because they fragmented. And again, carbon nitrogen and oxygen get fragmented. Well, some oxygen gets fragmented to nitrogen but some nitrogen gets fragmented down to the lithium, beryllium and boron range and that's how it goes. So we can measure that by measuring the cosmic rays
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and in fact, one of the experiments I did was to measure the ratio of beryllium 10 to beryllium nine. Beryllium 10, when it's completely stripped, has a lifetime of 1.5 million years. If you leave special relativity, as you increase its energy, the time that's in its rest frame is 1.5 million, that's time dilation will allow you then
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to look at that ratio and see how it changes with energy and what we see, it's about 10 million years is the typical travel time for the cosmic rays. And so therefore we know roughly the density and so forth. So what this does is tell you the cross section but in fact, it's not coming from the cosmic rays, they're a small fraction of the total mass
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but the fact is those cosmic rays are all going around through all the material in the galaxy and since it doesn't matter if the proton is at rest and you're hitting it or the proton's going fast and hitting the stuff at rest, it's gonna fragment things roughly the same way and so you can predict what the fragmentation is and that's how you get the slightly elevated versions
27:01
and that's how we get the elements that are normally destroyed in stars when we also fill in some of the things in between. Okay, so up to the iron peak, we have the nuclear cyclical equilibrium, beyond that we have the R process and for some reason somebody labeled gold on here,
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apparently alchemists like gold, that's how we got a bad name. But it turns out the abundance of elements of isotopes or unique femur prints of all the various processes is you see the effect of big magnet consensus, you see the effect of stars, you see the effect of supernova, you see the effect of the galactic cosmic rays
27:41
that show up in various ways and to interpret and understand this, you need to follow the nuclear physics and the process very well. It's not a fully solved problem but a lot of progress has been made, work continues on it and observations are beginning to help us and so what do we learn from telescopes? Well, I have quizzes on the side
28:00
but we're not gonna go through this. Here's a nice picture of the Orion Nebula and superimposed on it is the spectrum and on the spectrum we'll label some of the chemical elements that are seen there and one of the things you will notice is in this particular set, there's a lot of things we think of as organic chemicals, right? There's methanol, there's sulfur,
28:21
well, sulfur dioxide, I didn't think, the dimethyl ether, formaldehyde, right? I can remember as these observations are being made, we eventually saw, we saw all the building blocks of DNA and we saw almost all the amino acids, right? They exist in gas clouds around stars that have blown up or had big stellar winds and ejected
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and have big planetary nebula. So here's another example where you see other things. Now, turns out carbon and carbon monoxide are important for cooling of clouds to make the second generation of stars but you need those heavier elements to make the rocky cores in order to have planets. So first generation of stars had to make some of the elements so that you could have the next generation of stars
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that would actually have planets. So we have a rocky planet, Jupiter also has a rocky core in this planet and then it's outside the frost line so it can freeze water and then it can hold the gases, right? So the biggest one should be just outside the frost line and so on, that's not very, oops. Here's another example showing some molecules.
29:23
Here's another example. I'm running out of time so I'm going through it more quickly. Here's Tycho's supernova and you can see the x-rays and you can see the various elements, lines from the elements showing up and you can see these exist in the clouds around supernova but even more than that,
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we now have experiments, satellites that have gone up and look at the gamma rays and they're looking at particular gamma rays from radioactive isotopes. So the top one is a plot of the whole sky and you can see the galactic plane across the center and you see that where the supernova have been, there's a lot of aluminum-26
30:01
whose half-life is just under a million years, right? So the life scale of the universe is billions of years so these things have to be being produced on that kind of time scale but on the bottom right, you see the Cas-A supernova and you see titanium-44 which has half-life of 60 years.
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So there was a supernova there, that titanium is still left. A lot of the light curve of the supernova is actually radioactive materials decaying and producing energy during the thing. So there's a first big billet from the nuclear explosion and then there's more power coming from the radioactive decay and nickel-56 is one of those, okay?
30:42
So it turns out, I'm gonna run over slightly, galaxies looking back at time, looking at fossils is looking back at time. We can go back to see the beginning of the Earth, we can see when the life starts forming, we can also see the impact of cosmic rays and other things but the thing that I haven't talked to you about but exist is the fact
31:01
there's a lot of chemical fractionation that makes certain chemicals available to life because you don't say homogeneous, the iron goes to the center and so on but there are places where chemicals get concentrated and therefore life is able to do it. So let me try and finish up. So the other issue is the Big Bang is a series of phase transitions.
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So I just talked to you about one here in three minutes where we make the elements. In 300,000 years, six orders of energy lower in energy, we make the actual atoms and back before that, we make the protons into neutron. Each one of those is a different energy scale and we don't worry about the other energy scale, okay?
31:43
So now we know the chemistry of the universe in a somewhat different way. The heavy elements, that is the carbon-nitrogen and heavier, they're only 0.03% of the stuff in the universe, it's less than the amount of energy in the universe. Stars, which are mostly hydrogen and helium and free hydrogen and helium are four and a half percent of the universe.
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The dark matter, and who knows what the chemistry of dark matter is, and the dark energy represent 95, 96% of the energy in the universe. So these are all part of a, there's cosmic connections, all these guys link together but they're all certainly separate. So I think I will finish at this point
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and save the opportunity for questions and discussion from my discussion this afternoon. So thank you very much.