big bang, black holes, no math

Big Bang, Black Holes, No Math

Physics We NeedTopic 2: Gravity

1


ASTR/PHYS 109Dr. David TobackLectures 8-11



Prep For Today (is now due) – L11• Reading:

– BBBHNM Unit 2 (Chapters 5-9): Was due already– Recommended Reading:

• See P3 of http://people.physics.tamu.edu/toback/109/Syllabus.pdf• Warm-up Quizzes

– Warm-up Quiz Part 4 (Peerceptiv): Was due already• Pre-Lecture Reading Questions:

– Unit 2 Written Assignment: • Changed from Pass/Revise to just requiring a 5/10 to pass, but it will count as part of your

grade. • Everyone has their first attempt graded. Will continue to work grading revisions

– Unit 2 Quiz: Was due before class• You can start as soon as you Pass Written Assignment Stage (now only 5/10)• Also requires Unit 1 and EOC 3

• End-of-Chapter Quizzes– Chapter 5a&b: Was due already

• Paper 1:– Feel free to use the optional Feedback Assignment in Peerceptiv– Will assign when we finish Chapter 6, and text is due one week later. Submit to Peerceptiv and

TurnItIn, and do Reviews directly after– Extra credit for all students who complete all potions within the 72 hour window (see instructions)

• Honors Section:– “Stage 1 Rough Draft”: Was due before Monday’s class– “Stage 1 Final Draft”: Due before next Monday’s class– Need to hear from you at least once every 7 days 4



The Data

50



Does this work for Stars?

Simulation without Dark Matter

Simulation with lots of Dark Matter particles in

the galaxy

http://bigbang.physics.tamu.edu/Figures/StolenAnimations/galrot_anim.gif

Watch how fast a star rotates around the center of the galaxy…

Data looks like this 51



Data well explained by lots of “Dark Matter” (Dark matter fills our galaxy kinda like a gas

that fills a balloon with the latex being provided by gravity)

This is where it gets its nameIn some sense, the name is a statement of

almost all we know about it: It doesn’t interact with light or atoms very much (if at all), and it

has mass like all other matter

52



53

Another Experiment

Maybe there isn’t dark matter and General Relativity is

wrong? Look at the gravitational impacton light that travels through

the Universe, through a galaxy, and towards us



Einstein Ring’s?

54



Have observed LOTS of Einstein rings (most just

not this pretty)

Fact: We observe Einstein RingsThe “near” galaxy

The light from the “far” galaxy spread out into a ring

55



Observe and Measure the Amount of Dark Matter from Einstein Rings

56

Measure the amount of lensingTwo hypotheses:1. Small lensing effect if

there is only atomic matter (the amount of light tells us how much atomic matter there is)

2. Large lensing effect if there is atomic matter + Dark Matter

Observation: Large lensing… use this to measure the amount of dark matter



57

Winner: General Relativity + Dark Matter

• Many observations indicate that General Relativity correctly describes the motion of light, galaxies and stars in the Universe we live in space and time are related

• Space can curve, stretch, change etc. • Curved space-time will be very important in

later chapters when we talk about the expansion of the Universe

• Strong evidence that dark matter exists and has been an important part of the evolution of our universe since the early moments after the bang



Lecture on Chapter 6 now complete

58



Paper 1

59

• Abbreviated description: What is the evidence for Dark Matter? – More detail on Peerceptiv, you REALLY need to read ALL the instructions and

hints– Explain it to someone who isn’t taking the class (no jargon) using the

REQUIRED format– Do Warmup Quizzes, Part 4

• Each paper is usually 5 paragraphs: – Introduction paragraph that gives the “answer” up front and outlines the

evidence• Lawyer’s opening statement

– Body paragraphs where you “make the case”• Make the case using evidence• 1 paragraph per piece of evidence (often, but not always, three… see

Peerceptiv instructions and EOC quizzes)– Conclusion paragraph that ties it together

• Lawyer’s closing arguments• Not just restating the evidence

• Help:– Example of good paper

http://tobackgroup.physics.tamu.edu/toback/109/WritingAssignments/samplepaper.shtml



60

Taken from Peerceptiv for Paper 1

Physics We NeedTopic 3: Quantum Mechanics and Atoms


The Training Wheels are now off

• I’m happy to help, but you are expected to know what to do for all assignments

• If you have done the work diligently, you should be able to concentrate on just the science from here on out

2



9

So FarTopics1.Light and Doppler Shifts Done2.Gravity, General Relativity and Dark Matter Done

3.Atomic Physics and Quantum Mechanics Now

4.Nuclear Physics and Chemistry5.Temperature and Thermal Equilibrium



Where We Are Going NextIn Chapter 3 we learned a little about how the stuff of the Universe is put together

• Big things are made from LOTS of small things

• Small things: The Fundamental Building Blocks of Nature–What is the “stuff” in atoms? 10



The Largest Stuff•Most of the light we see from space comes from stars

•What are stars made of?–Stars are lots of atoms interacting

–The ways they interact creates light we can see

–Can study the distant stars by looking at the light from them

–Can study atoms here on Earth. Are they the same? 11



12

How do Atoms work?• ElectroMagnetism (electric charge)

– What holds electrons and protons together

• Quantum Mechanics– The way atoms form and do the funny things they do (which allows us to exist)

– Electrons in orbits– Atoms absorbing and emitting photons (light) Chapter 7



13

Chapter 8

Different Types of Atoms• The Strong Force

– Keeps protons and neutrons together in the atomic nucleus

– Different types of nuclei different types of atoms

– Different atoms Different light…•Nuclear Physics and Chemistry

• Studying the Stars using their light– Spectral lines of the atoms – Atomic “fingerprints”– The light we see from the stars



Overview of the story• Big things are made from LOTS of small things • Small things: The Fundamental Building Blocks of Nature

– What is the “stuff” in atoms• ElectroMagnetism (electric charge)

– What holds electrons and protons together• Quantum Mechanics

– Why atoms form the way they do– Electron in orbits– Atoms absorbing and emitting photons (light)

• The Strong Force– Keeps protons and neutrons together– Different types of nuclei different types of atoms– Different atoms Different light…

• Nuclear Physics and Chemistry Different TYPES of Atoms• Studying the Stars using their light

– Spectral lines of the atoms – Atomic “fingerprints”– The light we see from the stars

ThisLecture

NextLecture

14



15

The Fundamental Building BlocksOur best understanding:

The very BIG stuff is made up of LOTS of very small stuff

Need to understand:1. What are the

fundamental building blocks of nature

2. How it’s all held together

3. How they “create” the light we see



16

The experiment gives results like #2!

Early Evidence for the Atomic Model(before we knew it was electrons orbiting a nucleus)

Shoot atoms at a “target”

Bag stuffed with cotton and a few small rocks

The positive charge in an atom and most of its mass is concentrated in a tiny, very dense center: The Nucleus

Bag stuffed with cotton

Theory:

1?

2?

Experiment (1910’s):



17

The Building Blocks of NatureIn the 19-teens and 20’s experiments determined:

• Atoms are made of a nucleus surrounded by electrons– Many types of nuclei

– Only one kind of electron



Nuclear PhysicsMany years later (using many of the same methods):

• Nucleus is composed of neutrons and protons

• Number of protons and neutrons in the nucleus determines the atom type–Explains the periodic table 18



19

The Fundamental Building Blocks of Atoms

• Electrons• Neutrons• Protons–Neutrons and Protons are really made of quarks•Discovered in the 1970’s •We’ll talk more about this in the next chapter

Talked about this in Chapter 3

More in Chapter 8



20

Putting Them Together

Why do the fundamental

building blocks stick together to

form atoms?



21

Overview of the story• Big things are made from LOTS of small things • Small things: The Fundamental Building Blocks of Nature

– What is the “stuff” in atoms• ElectroMagnetism (electric charge)

– What holds electrons and protons together• Quantum Mechanics

– Why atoms form the way they do– Electron in orbits– Atoms absorbing and emitting photons (light)

• The Strong Force– Keeping protons and neutrons together– Different kinds of nuclei

• Nuclear Physics and Chemistry different atoms• Spectral lines of the atoms

– Atomic “fingerprints”– The light we see from the stars

ThisLecture

NextLecture



22

ElectroMagnetism• You probably already know that protons and electrons have “electric” charges

• Positive charge and negative charge attract each other

• Call this ElectroMagnetism

+

-



23

Weirdness…You probably never thought about it this way but in many ways the way things with electric charge attract is very similar to gravity

+

-



Gravity vs. ElectroMagnetismElectroMagnetism

• Every charged object in the universe “attracts” every other charged object in the universe

• The bigger the charge, the bigger the attraction

• The further the distance between the objects, the smaller the attraction

Physics 202Physics 207

Gravity• Every object in the universe attracts every other object in the universe

• The bigger the mass, the bigger the attraction

• The further the distance between the objects, the smaller the attraction

Physics 201Physics 206 24



25

•Gravity: –All objects attract no matter what – (As far as we know…)

•ElectroMagnetism:

–Ignores neutral particles

What’s different?



Prep For Next Time – L11• Reading:

– BBBHNM Unit 2 (Chapters 5-9): Was due already– Recommended Reading:

• See P3 of http://people.physics.tamu.edu/toback/109/Syllabus.pdf• Warm-up Quizzes

– Warm-up Quiz Part 4 (Peerceptiv): Was due already– Warm-up Quiz Part 5 – Feynman Diagrams: Assigned next time (figures being fixed)

• Pre-Lecture Reading Questions:– Unit 2 Written Assignment:

• Changed from Pass/Revise to just requiring a 5/10 to pass, but it will count as part of your grade

• Everyone has their first attempt graded. Will continue to work grading revisions– Unit 2 Quiz: Was due before class

• You can start as soon as you Pass Written Assignment Stage (now only 5/10)• Also requires Unit 1 and EOC 3

• End-of-Chapter Quizzes– If we finished Chapter 7 then End-of-Chapter Quiz 7a & 7b (else, just through Chapter 6)

• Paper 1:– Feel free to use the optional Feedback Assignment in Peerceptiv– Text of Paper 1 is due 1 week from today, submit to Peerceptiv and TurnItIn– Do Reviews directly after submission– Extra credit for all students who complete all potions within the 72 hour window (see instructions)

• Honors Section:– “Stage 1 Rough Draft”: Was due before Monday’s class– “Stage 1 Final Draft”: Due before next Monday’s class– Need to hear from you at least once every 7 days

75

big bang, black holes, no math

Documents