Evidence for the Big Bang Topic 3: Photons and Hydrogen in the Universe Big Bang, Black Holes, No...

Evidence for the Big BangTopic 3: Photons and Hydrogen in the

Universe

Big Bang, Black Holes, No Math

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ASTR/PHYS 109

Dr. David TobackLectures 16 & 17


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Was due Today – L16• Reading:

– Unit 3• Pre-Lecture Reading Questions:

– Unit 3 Revision in CPR (if desired): Stage 1 due Wed before class

• End-of-Chapter Quizzes:– Chapter 10 & 11

• Papers: – Paper 1: Revision (if desired):

• Stage 2 due Monday March 17 by 11:55PM

– Paper 2: • Stage 2 due Monday March 17 by

11:55PM


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Was due Today – L17•Reading:– Unit 4

•Pre-Lecture Reading Questions:– Unit 3 Revision in CPR (if desired):

Stage 1– Unit 4: Stage 1

• End-of-Chapter Quizzes:– Chapter 11

•Papers: – Paper 1 Revision (if desired): Stage

2– Paper 2: Stage 1 due Monday


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Paper 3: The Assignment

•Abbreviated Description: What is the evidence for the Big Bang?–Explain it to someone who isn’t taking the class (no jargon)

•Make sure you read ALL the instructions in CPR

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Overview

Evidence for the Big Bang?•Finished: –The Exploding Universe–Expanding Space-Time

•This Time:–More evidence for a hot early Universe? –Photons and Hydrogen in the Universe


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Before we begin…

•The Cosmic Background Radiation provides, perhaps, the most compelling piece of evidence for the story of the Big Bang

•Unfortunately, it’s the hardest to explain to the non-scientist–Radiation = Photons


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Two Different Pieces of Evidence

When we look at the stuff in the Universe we see that

1. ~90% of the atoms are hydrogen, ~10% are helium and there are very little of everything else– The Earth is very different than

the rest of the Universe in many ways

2. Lots of photons uniformly distributed with a Temperature of 2.7 Kelvin– Cosmic Background Radiation


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Prelude to the Story

To understand why the photons and amount of hydrogen in the universe are important, we need to understand a little about the evolution of the Universe


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Outline

•A ridiculously brief history of time

•The Early Universe and its Particles in Thermal Equilibrium

•Nuclei and atoms and their reactions in the Early Universe

•The stuff in the Early Universe

•As the Universe expands and cools


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The Early Universe

If there was a Big Bang, what would the Universe look like a second after the Big Bang?

•Very small•All the particles would have

high energies•Lots of fundamental particlesLet’s address each of these

issues one at a time


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Big Question We are Trying to answer

How did the universe get from to?

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Will say why we think it started like this in a

bit

Early Universe Today


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Why Small?

If the universe has been expanding for billions of years, it would have been smaller billions of years ago

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Why High Energy Particles?

• If the universe has been expanding and stretching the wavelengths of the particles, this makes them low energy now

•But back then, when they were less-stretched, they must have been higher energy

•Long wavelength Low energy•Short wavelength High

energy

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Why Fundamental Particles in The Early Universe instead of Composite Particles like Atoms?

•This one is harder to understand•Need to learn more about what happens when high energy particles interact 14


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Fundamental particles in the Early Universe

Many things COULD happen if we just had lots of fundamental particles

Start by describing how they combine

• Quarks could combine to form protons and neutrons

• Protons/neutrons could combine to form nuclei

• Nuclei and electrons could combine to form atoms


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Forming Protons

Quark

Quark

ProtonNuclear Reaction

Quark

qqq Proton


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Proton + Proton Deuterium + Anti-Electron + Neutrino

Forming Heavy Nuclei

Proton

Proton

DeuteriumNuclear Reaction

Anti-Electron

Neutrino


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Forming Atoms

Proton

Electron

HydrogenAtom

ElectroMagnetic Reaction

Proton + electron Hydrogen Atom +

photon


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The Story

This is great… you can see that IF there were lots of fundamental particles in the early Universe, they could combine to create the things we see today, like stars and galaxies

Universe just slowly assembled over time

Lots of atoms combine to form stars, then galaxies, then us! (more on this in later chapters, since it’s not that simple)


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Collisions in the Early Universe

Could the Universe have started with lots of fully formed galaxies that just have been moving away from each other since?

What if there was a big bang that produced lots of lots of fully formed, heavy atoms? Photons?

Wouldn’t stay that way! Why not?• High energy Collisions break apart

atoms and nuclei… we’d end up with fundamental particles


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Atoms in the Early Universe

Proton

Electron

HydrogenAtom


High Energy Photon Breaks up Atoms

quickly Free electrons and

protons

High Energy Photon


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Nuclei in the Early Universe

Proton

Proton


Photon Breaks up Nucleus before it

can find an electron to create an Atom

or find another nucleon to form a

bigger nucleus Free protons and

neutrons

High Energy Photon


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Heavy Atoms in the Early Universe

Proton

Deuterium

High Energy Photon


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Bottom line:Early Universe has Fundamental

Particles with Really High Energies

• In the early Universe we have many different types of fundamental particles because high energy collisions can create all the different types

• Composite particles could get formed, but other high energy particles would bust them apart we end up with only fundamental particles 24


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What else happens in collisions in the Early

Universe?High energy photons lower energy photons

Low energy photons higher energy photons


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Thermal Equilibrium

•All these high energy particles are quickly colliding in a small space

•Eventually all the particles will (roughly) have the same energy–Said better: The same Temperature

–Said even better: The universe will come into Thermal Equilibrium


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Particles in Thermal Equilibrium

Because of the way particles interact at high energies we get lots of photons, protons, neutrons and electrons

Even if the universe didn’t start with lots of each of these particles, eventually there would be lots of them– Produced in collisions or in

the decay of other particles


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Electron

PositronPhoton

Electron pairs and photon pairs interact and annihilate electron and photon Soup

Electron-Photon Soup in the Early Universe


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Then what happens?

What will happen later? The Universe Expands and stretches the wavelengths of the particles

Universe cools… energies drop


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Expanding Space Part 1

Photons in Thermal Equilibrium

Early Times High Temperature, high energy

particles


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Later Time Space gets Bigger

Wavelength gets Longer

Temperature is Cooler, lower energy particles


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Even later Red Shifted

Even cooler, even lower energies


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Bottom Line

•As time progresses all the particles, including the photons, will have lower energies–Lower temperatures

•The interactions between the particles are very different at different energies


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Later Times: Atoms and Low Energy Photons

Proton

Electron

HydrogenAtom


Low energy photons typically only “bump” atoms or excite them

Low Energy Photon


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Nuclei and Low Energy Photons

Deuterium

Low Energy Photon

Low energy photons only “bump” nuclei


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Proton + Deuterium Helium3 + Photon

Can Now Build Up Heavier Heavy Nuclei

Deuterium

Proton

Helium3

Nuclear Reaction

Photon


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Helium3 + Helium3 Helium4 + 2 Protons

Creating Stable Helium

Helium3

Helium3

Helium4

Nuclear Reaction

Proton

Proton

This is why we have ~90% hydrogen and ~10% helium. More on this later…


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Hot Early Universe

The high-energy particles in a hot, small Universe would break apart heavy atoms and nuclei, and explains two pieces of experimental data

1. So much hydrogen and so little of other types of atoms except Helium

2. Lots of photons with the same temperature in all directions


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What happens to the photons?

Particles in the Universe

•Early times: Protons, Neutrons, Electrons, Positrons and Photons

•Later times: Photons and atoms

•Much later: Atoms combine to form stars and galaxies•More on this later


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Life as a Photon in the Universe

• If a photon is high enough energy to break a part an atom it will

• Any photon that isn’t high energy enough won’t interact again and will thus just travel forever

• Thus, the last thing a typical photon in the universe interacts with is an atom

• Why does that matter? Essentially, they are unchanged since the time of “last interaction” except to be stretched– Tells us about the Universe when they

last interacted 40


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What happens to

the Photons?The photons simply “cool”

as space expands

Lower Temperature

Longer WavelengthsThen

Now


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Why should we believe this Story?

Should be able to observe this “remnant” of the Big Bang

Any evidence for photons with energies that look like a low temperature?


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A Great Experiment

Arno Penzias and Robert Wilson in 1964 were doing high precision measurements of photons for radio waves

Noticed “noise” in their system that turned out to be photons with a temperature of about 3 degrees above absolute zero

Not looking for these photons… but won the Nobel Prize

anyway


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The same Temperature in all directions?

Look at the full sky in a single

map

Stretch out a sphere onto a

flat page

Temperature Map (i.e, different colors

correspond to different temperatures)

Incredibly Uniform!

2.78 degrees Kelvin


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Conclusion from the data?

•Data is exactly consistent with a Universe that was small and hot a long time ago… what we would expect with a Big Bang!

•No other reasonable explanation for where lots of photons with a specific temperature would come from, and be the same in all directions


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Summary1. We observe galaxies moving

away from us in a manner that is consistent with an expansion of space-time

2. Most of the atoms in the universe are hydrogen and helium and not much else

3. We observe photons (the cosmic background radiation) uniformly distributed in all directions that have a temperature consistent with cooling for ~13.7 billion years


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Fun Way to think about things

• Look at things “far away” in space Backward in time• Can see stars from millions of years ago

– Look like stars today• Look at galaxies from billions of years ago

– Look like galaxies today• Look at galaxies from about 13 billion years ago

– Look like baby galaxies forming• Look even “farther back”

– No galaxies at all since they haven’t even formed• Look further still… See the “white noise” of the cosmic

background radiation and no evidence of any galaxies– Looking back at the earliest times we can “see”

without the photons going through the “fog” of the early universe… Can’t see through the fog to earlier times… Then again, there isn’t much time before that anyway

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How far can we look back in time?

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All we can see is back a certain distance in TIMEWe can’t see anything “past” the background

radiation


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What’s Next?

Unit 4: Evolution of the Universe•The Early Universe•After the First Three Minutes


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Paper 3: The Assignment

•Abbreviated Description: What is the evidence for the Big Bang?–Explain it to someone who isn’t taking the class (no jargon)

•Make sure you read ALL the instructions

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For Next Time – L16• Reading:

– Unit 4• Pre-Lecture Reading Questions:

– Unit 3 Revision in CPR (if desired): Stage 1– Unit 4: Stage 1

• End-of-Chapter Quizzes:– If we finished Chapter 12, then Chapter 12 (if not,

Chapter 11)• Papers:

– Paper 1 Revision (if desired), Stage 2 due Wednesday before class• (Text needs to be in turnitin on eCampus)

– Paper 2 Revision (if desired), Stage 1 due Monday before class • (Text needs to be in turnitin on eCampus)

– Paper 3: If we finished Chapter 12, Stage 1 due Monday before class

• Honors Paper:– Stage 1 must be approved explicitly. Revisions due by

Monday


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For Next Time – L17• Reading:

– (Unit 4)• Pre-Lecture Reading Questions:

– Unit 3 Revision in CPR (if desired): Stage 2– Unit 4: Stage 2

• End-of-Chapter Quizzes:– If we finished Chapter 12, then Chapter 12

(if not, Chapter 11)• Papers:

– Paper 2 Revision (if desired), Stage 1– Paper 3: Stage 1 due Wednesday before

class• Honors Paper:

– Stage 1 must be approved explicitly. Revisions due by Monday


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Full set of Readings So Far•Required:–BBBHNM: Chaps. 1-13

•Recommended:–TFTM: Chaps. 1-5–BHOT: Chaps. 1-7, 8 (68-76), 9 and 11 (117-122)–SHU: Chaps. 1-3, 4(77-86), 5(95-114), 6, 7 (up-to-page 159) –TOE: Chaps. 1 & 2

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Clicker Question

Let’s say you were the person observing the galaxies, but each other person in the room were a galaxy. Which person in the room is moving away from you most quickly?

a)Back leftb)Back rightc)Front leftd)Front right 55


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Clicker QuestionWhich of the following is the best ranking

for the speeds (from fastest to slowest) at which galaxies A, C, and D would be moving away from an observer in galaxy B?

a)A > C > Db)D > A > Cc)C > D > Ad)D > C > A

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Clicker QuestionAre the Earth and Sun moving away from

each other since space-time is expanding?

a)Yes. It is just a matter of time before the Earth will leave the Sun's orbit.

b)Yes, but the gravitational attraction between the two keeps them at the same distance

c)No, because the Sun is big enough to prevent space-time from expanding locally

d)No, because the only thing that matters is that the Earth is attracted to the Sun

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Clicker QuestionLet's say I have two galaxies in space

and they are exactly stationary relative to each other. What will happen next?

a)Since they are so massive that they will attract each other by gravity and start moving towards each other.

b)Since space-time is expanding, the distance between them will grow as space-time expands so they will start moving away from each other.

c)It depends on the overall distance between them. 58


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Clicker QuestionIf space-time is expanding, is our galaxy

expanding?a)Yes. Everything in the universe is

moving away from everything else. b)No. It isn't expanding because the

gravitational attraction of masses pulls the galaxy back together again

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Clicker Question

If space-time is expanding, are atoms expanding?

a)Yes. Everything in the universe is moving away from everything else.

b)No, they aren't expanding because the electric charge attraction and quantum mechanics keep the atoms the same size in space

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Clicker QuestionFor the most distant

galaxies, which is true?

a)Most of the red-shift of their spectral lines is because they are moving very fast through space

b)Most of the red-shift of their spectral lines is because space is expanding 61


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Clicker Question

Why is hydrogen the most abundant element in the universe?

a)It is the lightest elementb)Other elements were broken

apart by high energy photons in the early universe

c)Both of these contribute62


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Clicker Question

What was the last thing a typical photon in the universe (part of the Cosmic Background Radiation) did before we detected it?

a)Broke apart a hydrogen atom

b)Broke apart a helium nucleic)Broke apart a Proton

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Clicker Question

Why do the photons in the universe appear to be in thermal equilibrium?

a)Because they all have exactly the same energy

b)They are in thermal equilibriumc)The universe was in thermal

equilibrium, and the photons are just one of the particles in the Universe

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Clicker QuestionIf the universe stated contracting, which

of the following would be evidence for it?

a)Distant galaxies would be less red-shifted

b)The CMB would have a lower temperature

c)We would start seeing distant galaxies have blue shifts

d)The Earth would start getting closer to the Sun

e)Atoms would start shrinking 65


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Clicker QuestionQ: Which of the following statements is

MOST correct?a)The photons in the cosmic background

radiation are there because the Universe has been expanding for ~13 billion years

b)The photons in the cosmic background radiation are there because the universe was in thermal equilibrium

c)The photons in the cosmic background radiation are there because photons can exist forever 66


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1 Paragraph Essay Question

Why are there so many more hydrogen and helium atoms in the universe than any other type of atom?

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Clicker QuestionWhy do we think that the Universe is an

expansion of space-time and not an explosion? Fix me.

a)Because distant galaxies are moving away from us.

b)Because the farther away a galaxy is, the faster it is moving away

c)Because hydrogen and helium are most of the atoms in the universe

d)Because of the Cosmic Background Radiation

e)Not great... 68


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Clicker QuestionWhich of the following statements is MOST correct? • The photons in the cosmic background radiation are there because the Universe has been

expanding for ~13 billion years• The photons in the cosmic background radiation are there because the universe was in thermal

equilibrium• The photons in the cosmic background radiation are there because photons can exist forever

The Universe needed to be in thermal equilibrium for atomic hydrogen to keep accumulating in the early universe

• True• False• • • Is the CMB in thermal equilibrium?• • CMB cold and getting hotter or cold and getting colder?

What happens to the energy of photons as the universe expands?• They energy of the photons don’t actually change because photons always move at the speed

of light. It’s just an optical illusion. • The energy of the photons is converted to the potential energy of the universe• The energy of the photons is converted to mass• Need other good options… that could be correct and test students conceptual understand.

What do they THINK happens to the photon energy?

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Clicker QuestionAre the Earth and Sun moving away from

each other since space-time is expanding?

a)Yes. It is just a matter of time before the Earth will leave the Sun's orbit.

b)Yes, but the gravitational attraction between the two keeps them at the same distance

c)No, because the Sun is big enough to prevent space-time from expanding locally

d)No, because the only thing that matters is that the Earth is attracted to the Sun

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Clicker QuestionLet's say I have two galaxies in space

and they are exactly stationary relative to each other. What will happen next?

a)Since they are so massive that they will attract each other by gravity and start moving towards each other.

b)Since space-time is expanding, the distance between them will grow as space-time expands so they will start moving away from each other.

c)It depends on the overall distance between them


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Clicker Question

If space-time is expanding, is our galaxy expanding?


b)No. It isn't expanding because the gravitational attraction of masses pulls the galaxy back together again


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Clicker Question

If space-time is expanding, are atoms expanding?


b)No, they aren't expanding because the electric charge attraction and quantum mechanics keep the atoms the same size in space

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For Next Time– L18• Reading:

– BBBHNM: 14• Pre-Lecture Reading Questions:

– Chapter 14• End of Chapter Quizzes:

– Chapter 11• Papers:

– Paper 0 Revision: Was due before class. Let us know if you think you were mis-graded. Still working on re-grades.

– Paper 1: Still working on re-grades. – Paper 1 Revision: Was due before class if you

wanted to submit. If you want an extension let me know in email ASAP

– Paper 2: Was due before class. Let me know if you think you were misgraded

– Paper 2 Revision: If you want to do a revision, text is due one week from today before class


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For Next Time– L18• Reading:



– If we finished Chapter 12, then 12, (if not, then just Chapter 11)

• Papers:– Paper 0 Revision: Was due before class. Let us know

if you think you were mis-graded. Still working on re-grades.





– Paper 3: If we finished Chapter 12, then due 1 week from today


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Was due for Today – L18• Reading:




– Paper 0 Revision: Was due before class. Let us know if you think you were mis-graded. Still working on re-grades.






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Was due for Today – L19• Reading:




– Paper 0 Revision: Still working on re-grades. – Paper 1: Still working on re-grades. – Paper 1 Revision: Text was due already.

Calibrations/Reviews/Self-assessment due before class on Wed

– Paper 2: Working on re-grades– Paper 2 Revision: Will be posted soon, checking the

calibrations/rubrics for potential problems


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Prep For Next Time – L8•Reading:–BBBHNM: All reading through Chapter 14

•Reading Questions:–All reading questions through 14

•eLearning Quizzes:–End-of-chapter quiz 12

•Papers:–Paper 2 text due in CPR and turnitin.com by Tuesday at Midnight –Paper 2 calibrations, reviews and self-assessment due Monday before class–Paper 3 text due in CPR and turnitin.com before next Wednesday!


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Prep for Today (Is now due) – L16

• Reading:–BBBHNM 13

• Reading questions:–Chapter 13

• End-of-Chapter Quizzes:–Chapter 11

• Paper Stuff–Paper 2: Was due Monday–Paper 3: Will be assigned after

we finish Chapter 12


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Prep for Today (Is now due) – L17

• Reading:– BBBHNM 13

• Reading questions:– Chapter 13

• End-of-Chapter Quizzes:– Chapter 11

• Paper Stuff– Paper 2 Revision: Due 1 week from

day (same time as paper 3)•Need to do text, calibrations and reviews

– Paper 3: Due 1 week from today


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Prep For Next Time – L8•Note: May change depending on how far we

get in lecture•Reading:–BBBHNM: All reading through Chapter 14

•Reading Questions:–All reading questions through 14

•eLearning Quizzes:–If we finished Chapter 12 then end-of-chapter quiz 12 (else just through Chapter 11)

•Papers:–Paper 3 text due in CPR and turnitin.com before Wednesday!


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Prep for Next Time – P15

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• Reading– BBBHNM 13– Recommended:

• TFTM: 4 & 5• SHU: 5 (104-114), 7 (154-159) • BHOT: 8 (68-76)

• Reading questions– Chapter 13

• End-of-Chapter Quizzes– If we finished Chapter 12 then end-of-chapter quiz

12 (else just 11) • Papers

– Paper 2: Calibrations and Reviews due tonight– Paper 3: If we finished Chapter 12, then paper 3 is

due 1 week from today


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Prep for Next Time – P16

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• Reading– BBBHNM 13

• Reading questions– Chapter 13

• End-of-Chapter Quizzes– If we finished Chapter 12 then end-

of-chapter quiz 12 (else just 11) • Papers

– Paper 2: Was due on Monday– Paper 3: If we finished Chapter 12,

then paper 3 is due 1 week from today


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Paper 3 Organization Stuff• Due 1 week after we finish Chapter 12• Want feedback before turning it in?

– Post it in eLearning in .doc (or .pdf) for comments by the TA

– Make sure you polish it•If you have lots of grammar and spelling mistakes we’ll just make you try again

• Will be due in CPR and turnitin.com at the same time

• Calibrations will be due 1 week after submission date

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Big Bang Produces Fundamental Particles


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What are the Fundamental Particles?

The Big Bang Produces lots of particles

•Electrons and anti-electrons•Photons•Quarks and anti-quarks–Others… More on this later


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Back then… and Today

•What would the objects in Thermal Equilibrium in the Early Universe look like today after space has expanded?

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The Reading So Far and For Unit 4

Reading for next time:• BBBHNM 13• TFTM: 4 & 5• SHU: 5 (104-114), 7 (154-159) • BHOT: 8 (68-76)Full reading so far:• BBBHNM: Chaps. 1-14• TFTM: Chaps. 1-5• BHOT: Chaps. 1-7, 8 (68-76), 9 and 11 (117-

122)• SHU: Chaps. 1-3, 4(77-86), 5(95-114), 6, 7 (up-

to-page 159) • TOE: Chaps. 1 & 2Lecture prep: Turn in on eLearning

Two questions from Chapter 13


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Paper 1 Stuff• Done with grades for both original and

Revision – Graded unfairly? Let us know!

• Passing score: Need ALL of the following– Text score: more than 21 points (70%)– Calibrations: more than 15 points– Reviews: more than 15 points– Overall score: more than 70 points

• Revision CPR– Do full CPR grading

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Papers 2 and 3 and Other Stuff

• Paper 2:–Text was due last Friday at noon–CPR grading due Friday at Noon

• Paper 3: –Due March 24th before class–1 week after we finish Chapter

12–Now open

• Elearning:–Unit 3 in progress 90


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Electron

Positron

Low Energy photon

Electron pairs

annihilate, but photon pairs don’t

create more

electrons!Not enough

Energy E=MC2

Electron Photon Soup


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Writing Assignments1. Short Assignment 1 did not go

well•Revise your submissions and

resubmit by 5PM on Friday2. Short Assignment 2 is posted

•Currently Due Thursday Oct 29th which is one week after we finish Chapter 12

eLearning:Unit 2 due before the beginning of next classNeed to be working on Unit 3


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Paper 1 FeedbackI must have been unclear on what I was looking for in

Paper 1• Your job was to explain the evidence for stars being

made of atoms, not convince people that its an interesting question or that scientists did something important– Think lawyer, not lobbyist

• The best papers had 5 paragraphs with an introduction that made it clear what question was being answered, then outlined the main pieces of evidence. Then each paragraph gave a different piece of evidence. The conclusion told how all the pieces tied together

• The common problems were: 1. Using humorous “getting started” words to motivate

why the question is important or interesting. 2. No structure, just started giving pieces of evidence

and stopped when all the pieces had been given3. Didn’t give all the different arguments needed to

make the case (like nuclear physics to explain atomic fingerprints)

4. Used words like “Spectral lines” but didn’t define them

5. Had a conclusion which essentially praises scientists for figuring it out


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Papers AFTER Paper 2

Two options1. Research Paper

• If you want to do the research paper option you must complete Stage 0 by Thurs Oct 29th

•Stage 1 due Thurs Nov 5th •Final paper due the last day of

class, Tuesday Dec 8th

2. Two short papers like the first one•One on Black Holes (due mid

Nov)•One on Dark Matter (due last

day of class)


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Soup

So our early Universe is a soup of:

•Protons•Neutrons•Electrons (and positrons)•Photons–Others… later

What happens to our soup?


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Two Hypotheses

1. No high energy photons protons “cook” into heavy elements Lots of heavy elements in the universe today

2. Lots of high energy photons protons can’t “cook” into heavy elements mostly hydrogen in the universe today

Because of Thermal Equilibrium and the way particles interact at high energies even if we didn’t have lots of photons, we’d eventually get a lot of photons


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Lots of High Energy Collisions

In the early Universe there must have been lots of high energy collisions

If there weren’t lots of high energy collisions then all the hydrogen would have been "cooked" into heavier elements–More oxygen, Nitrogen and Iron,

less HydrogenNot what we observe!

The Universe is ~75% hydrogen


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Big Toys

Properties of the noise:

•Point at the earth? Not coming from there

•The plane of the milky way? Nope

•From a nearby galaxy? Nope


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Other Possibilities?

Other things in the “horn”?

Noise appears to be the same and coming equally from ALL DIRECTIONS


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What happens to our Soup of Photons?

The photons simply “cool” as space-time expands Lower

Temperature

http://bigbang.physics.tamu.edu/Figures/StolenAnimations/CMB.swf


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Paper 1 Notes•Class Average: 63•Good Things:

– Most people got the structure and main topics for the paper (atomic model, spectral lines, etc…)

• If you want to improve your grade you may resubmit your paper 1 by March 25th– Again on WebCT by the new link

Paper1Redo


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Resubmitting? Things to work on

• You must explain these topics fully to a lay-person, not just make statements

• For example this is not an explanation:– “The atomic model explained by

quantum mechanics is responsible for the spectral lines we see.”

• Andy will stay after class if you want to talk about your paper


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Lots of High Energy Photons

In the early Universe there must have been LOTS of high energy photons

Why? Ask differently… What if this weren’t true?

Nuclear reactions would have proceeded so rapidly that a large fraction of the hydrogen would have been "cooked" into heavier elements

Not what we observe!The Universe is ~75% hydrogen


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Nuclear Cooking

This rapid nuclear cooking could only have been prevented only if the universe was filled with photons having high energyrequires high temperature


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Nuclei in the Early Universe

Proton

Proton


No high energy photons protons “cook” into heavy

elements

High Energy Photon

A high energy photon can break apart the Nucleus before it can find an electron to create an Atom or find another nucleon to form a bigger nucleus


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• Slide 29 Maps based on 53 GHz (5.7 mm wavelength) observations made with the DMR over the entire 4-year mission (top) on a scale from 0 - 4 K, showing the near-uniformity of the CMB brightness, (middle) on a scale intended to enhance the contrast due to the dipole described in the slide 19 caption, and (bottom) following subtraction of the dipole component. Emission from the Milky Way Galaxy is evident in the bottom image.


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Fix this with the flat background from COBE!


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TFTM 3: Cont…

• Equilibrium? • Like economics: if demand exceeds

supply, then the price will rise (cutting the effective demand) and encouraging production. If supply exceeds demand prices will drop (increasing the effective demand) and discouraging production.

• Electron and photon soup: If too many electrons, they will interact until there are more photons and the two come into equilibrium. I.e., the market clears.


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•Need WMAP pictures of uniformity

•With Doppler Shift•Have after Doppler Shift


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What are the Fundamental Particles?

•Electrons•Positrons (anti-electrons•Photons•Neutrinos•Proton•Neutrons•Hydrogen•Helium


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PHOTON BREAKING A NUCLEUS

PHOTON (γ)

HELIUM (He)


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PHOTON (γ)

HELIUM (He)


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PHOTON (γ)

HELIUM (He)


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PHOTON (γ)

HYDROGEN

(H)

HYDROGEN

(H)


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•This is some text…


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•Distribution


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•How the horn works…


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•What if in the early Universe it WASN’T in Thermal Equilibrium?

•How would the world look today?

•What would that predict?


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Need this part of the story?

•Video with lots of proton and neutrons forming lots of different nuclei–This is the “without” photon radiation picture

–Creates LOTS of non-hydrogen

•Version where the photons are constantly breaking it up–Left with most hydrogen


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BHOT 7 cont…

•Since energy is conserved, back when the Universe was small we had the same amount of heat but in a smaller amount of space

•As we saw before, this would be what we call a high temperature!

•The early universe should be very hot and dense, glowing white hot


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•This is some text…


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The Cosmic Background Radiation (2)

After recombination, photons can travel freely through space.

Their wavelength is only stretched (red shifted) by cosmic expansion.

Recombination:

z = 1000; T = 3000 K

This is what we can observe today as the cosmic background radiation!


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The Cosmic Background Radiation

R. Wilson & A. Penzias

The radiation from the very early phase of the universe should still be detectable today

Was, in fact, discovered in mid-1960s as the Cosmic Microwave Background:

Blackbody radiation with a temperature of T = 2.73 K


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Looking Back Towards the Early Universe

The more distant the objects we observe, the further back into the past of the universe we are looking


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Evolution of the Universe

Before After


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•Diffuse background of radio static


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The Cosmic Background Radiation

R. Wilson & A. Penzias

The radiation from the very early phase of the universe should still be detectable today

Was, in fact, discovered in mid-1960s as the Cosmic Microwave Background:

Blackbody radiation with a temperature of T = 2.73 K

Evidence for the Big Bang Topic 3: Photons and Hydrogen in the Universe Big Bang, Black Holes, No...

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Transcript of Evidence for the Big Bang Topic 3: Photons and Hydrogen in the Universe Big Bang, Black Holes, No...