Study Points• Give a brief timeline for the formation of the universe from Big Bang to present

day (BB, first atoms, universe becomes transparent, first stars, galaxies, solar system, humans!)

• What four pieces of observable evidence does the Big Bang predict?

• Explain why we can observe the afterglow of the hot, early universe, and what the CMB tells us.

• Is the expansion rate is accelerating? How do we know? What do we call that force?

• Describe open, flat, and curved universes and explain which type of universe is supported by observations

• Know basic properties of the universe including its age and contents (dark matter/dark energy/regular matter)

• Explain why inflation is necessary to explain the universe we see today (Horizon Problem and Flatness Problem).

• Name the four forces that control all physical processes in the universe

Evidence for the Big Bang

“The story so far:

In the beginning the Universe was created. This

has made a lot of people very angry and been

widely regarded as a bad move.”-- Douglas Adams, Hitchhiker’s Guide to the Galaxy

http://www.neverofftopic.com/re-topics/science-year-10-11/the-big-bang-theory/

Big Bang (BB) Timeline*• 10-5 s: universe fills with sea of energy and particles

• 0.0001 s: slight excess of matter over antimatter

• 4 s: protons, neutrons, electrons of today produced

• 3 min: He produced

• 30 min: Universe stops nuclear production 75% H & 25% He*

• 380,000 yrs: Universe cools enough to become transparent*

• 200-400 Myrs: first stars appear (H rich)*

• 1-14 Byrs: Galaxies grow and Milky Way forms (~13 Byrs old)*

• Successive generations of stars enrich the next generation with

heavier elements (massive stars)

• 10 Byrs: Our solar system forms (~5 Byrs old)*

• 14 Byrs: Humans think about the Universe!*

Creating Matter

Energy makes

particles & they

make energy

Universe cools enough

for protons and neutrons

to stick together

Reionization:

particles gain

electrons

BIG BANG plus

380,000 years

BIG BANG

BIG BANG plus

10-43 s

INFLATION

Universe

transparent

Light from first

stars

BIG BANG plus

~200-400 million years

Understand from

here on

Inflation

BIG BANG plus

14 billion years

Stars produce

heavy elements

Makes specific,

testable

predictions after

10-43 s

Approximate Size vs. Age of Universe

The size of the Universe (y-axis, in light years) versus the age of

the Universe (x-axis, in years) on logarithmic scales.

Some size and time milestones are marked.

https://www.forbes.com/sites/startswithabang/2017/03/24/how-big-was-the-universe-at-the-moment-of-its-creation/#41d9e33e4cea

Observable Evidence for BB

1. Redshift/Hubble’s Law – Universe began small and

is expanding*

2. Specific testable results*

a. H to He is 75% to 25% *

b. First stars/galaxies at ~300 million years*

3. BB radiation found – CMB at 2.73 K*

4. CMB is slightly lumpy – Planck Results*

5. Polarization of CMB – still looking

Evidence for BB*

1. Redshift – Universe began small*

Hubble’s Law – Space-time expanding*• expanding at a faster rate → accelerating

Universe Expansion

Acceleration Due to Dark Energy

http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/

http://www.scientificamerican.com/article/expanding-universe-slows-then-speeds/

Tim

e

(~1

4 b

illi

on

ye

ars

)T

ime

(~1

4 b

illi

on

ye

ars

)

~9 Byrs

~5 Byrs

Evidence for BB

2. Specific, testable prediction from Big Bang

model

a. H and He found at predicted 75% to 25% ratio*

BB model predicts H and He fused from

protons and neutrons in the first few minutes

AND at 75% to 25% ratio by mass

Found: 9 H to every 1 He (counting atoms)

75% of

mass is

H→

25% of

mass is

He

Evidence for BB

2. Specific, testable prediction from Big Bang model

b. Early galaxies

BB model predicts:

First star light should appear ~200-400 Myears after BB*

So far:

13.4 Bly distant galaxy

(~400 Myears after BB)

Abell Galaxy Cluster

From 2014

http://news.nationalgeographic.com/news/2014/01/140107-hubble-oldest-frontier-science-space-astronomy/

Evidence for BB

3. Radiation from BB predicted to be at 3K

Is 3K hot or cool?

Evidence for BB

3. Radiation from BB predicted to be at 3K

Is 3K hot or cool?

Cool (-454F)

*Evidence for BB

3. Radiation from BB predicted to be at 3K

Why so cool if universe began hot?

If Universe

began hot,

what type of

EM wave do

we look for?Microwave

Electromagnetic spectrum?

Wavelengths of red and violet?

First, what is

the λ of red

and violet?

*Evidence for BB

3. Radiation from BB predicted to be at 3K

Why so cool if universe began hot?

If Universe

began hot,

what type of

EM wave do

we look for?Microwave

Electromagnetic spectrum?

Wavelengths of red and violet?

λ of red = 700 nm

& blue = 400 nm

*Evidence for BB

3. Radiation from BB predicted to be at 3K

Why so cool if universe began hot?

If Universe

began hot,

what type of

EM wave do

we look for?Microwave

Gamma

rays

Microwave

*Evidence for BB

3. Radiation from BB predicted to be at 3K

Why so cool if universe began hot?

Now what

would we

see?

Universe expands for ~ 380,000 years and cools to ~3000 K

Microwave

*Evidence for BB

3. Radiation from BB predicted to be at 3K

Why so cool if universe began hot?

Would see

Universe expands for ~ 380,000 years and cools to ~3000 K

IR!

*Evidence for BB

3. Radiation from BB predicted to be at 3K

Why so cool if universe began hot?

What EM

type do

we look

for today?

After decoupling (380,000 years after BB),

Universe continues expanding, cooling, stretching the

waves….

Microwave

*Evidence for BB

3. Radiation from BB predicted to be at 3K

Why so cool if universe began hot?After decoupling (380,000 years after BB),

Universe continues expanding, cooling, stretching the

waves….

Microwave

Microwaves

What EM

type do

we look

for today?

*Evidence for BB

3. Radiation from BB predicted to be at 3K

Found!

Cosmic Microwave

Background

(CMB)

Arno Penzias and Robert Wilson in 1964

*Found Cosmic Microwave Background (CMB)

*Universe is filled with radiation at 2.73 K

*Evidence for BB

4. Tiny variations in CMB – Planck

spacecraft results!

• Radiation from the early universe is very

smooth (2.73 K)

• Temperature of early universe does not

vary much

• Therefore density varies very little

*Planck Spacecraft Results*

ESA http://www.esa.int/Our_Activities/Space_Science/Planck/Planck_reveals_an_almost_perfect_Universe

• Tiny variations in CMB (+/- 0.0001K)

• Tiny temperature variations = tiny density

variations in early universe

Evidence for BB: Planck results

And early universe

varied slightly in

density from one

spot to next =>

Seeds of galaxies.

0.9, 3.2, 13.8 billion years after BBhttps://imagine.gsfc.nasa.gov/news/17dec08.html

Evidence for BB

4. Planck results also show which BB model is

correct.

Different BB models predicted different sizes for

these small variations

and

different ages for the universe.

Evidence for BB*4. More Planck Results

Composition of Universe*

• ~5% (4.9%) “normal” matter

– p, n, H, He, you; called baryonic matter

• ~25% (26.8%) dark matter

• ~70% (68.3%) dark energy (more in a bit)

Evidence for BB

4. More Planck Results (not for test)

Data fits the accepted BB model very nicely

except

• Slight asymmetry in temperature variation

from one side of universe to the other

• “Large” “cool” spot (blue area near center)

Evidence for BB

5. Polarization (not on test)

– specifically evidence for inflation

(inflation coming up in a few slides)

• Predicts CMB fluctuations that are tiny but

measurable: polarization of CMB

• Scientists thought they had measured it in

2014 with BICEP2 in Antarctica, but Planck

later proved them incorrect. Story here

• Still looking for proof.

Watch Polarization Demo Video

https://www.youtube.com/watch?v=nCAKQQjfOvk

Evidence for BB

1. Redshift/Hubble’s Law – Universe began small

and is expanding*

2. Specific testable results*

a. H to He is 75% to 25% *

b. First stars/galaxies at ~300 million years*

3. BB radiation found – CMB at 2.73 K*

4. CMB is slightly lumpy – Planck Results*

5. Polarization of CMB – still looking

*Big Bang Model (from last lecture)The Universe (space and time):

• Springs into (tiny) existence ~ 13.8 Byrs ago

• For tiny fraction of a second, inflating rapidly

• For first 9 Byrs, – Expanding, cooling

– Rate of expansion slowing due to gravity

• For last 5 Byrs,– Rate of expansion

increasing due to

dark energy

Universe Expansion is Accelerating*(speeding up)

• *Supernova distances are farther away

than expected (standard candles!) [1998]

• *Rate of expansion of the Universe has

increased over the last 5 Byrs

• *Something is causing the universe to

expand faster now

• *Named Dark Energy

– ~70% of universe

Type 1a Supernovae remnant

Dark Energy Possibilities(not on test)

• NASA: “More is unknown than is known.”

• Property of space?

• Cosmological Constant from Einstein in 1917?

– Opposite of attractive gravity force

– Anti-gravity force

• Quintessence?

– Field

– Vacuum energy from space

– Explains subatomic particle behavior

• Something else?

?https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy

Dark Energy Summary

We don’t know what it is.

We just know what it does.

(Speeds up the expansion of the universe.)

Future of the

UniverseExpanding now.

What is next?

Is the Universe…

Closed? Flat? Open?

Red lines show future of our universe – but

those lines may or may not be flat to start

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Future of the Universe• Closed (sphere)

– density > critical density

– expands and then collapses (Big Crunch)

– greater than 1 angular degree in temp. change

• Flat (sheet)• density = critical density

• expands forever

• 1 angular degree

temperature change

• Open (saddle)• density < critical density

• expands slowly

• less than 1 angular degree

temperature change

http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/Images/Oscillation_lg.jpg

Future of the Universe

http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/Images/Oscillation_lg.jpg

Future of the

UniverseWhat makes a

universe

“closed”?

Mass

Does the universe

have enough?

Not enough mass – even

counting dark matter

and

Increasing Acceleration doesn’t

fit closed expansion

Not a Closed

Universe

http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/Images/Oscillation_lg.jpg

Future of the

UniverseWhat makes a

universe “open”?

Mass

Does the universe

have the right

density?

Too much mass & density to be

open

Not an Open

Universe

http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/Images/Oscillation_lg.jpg

Future of the Universe

• Not closed

• Because of increasing acceleration

• And too small of mass, too low of density

• Not open

• And too much mass, too high of density

Our

Universe is

Flat

http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/Images/Oscillation_lg.jpg

Future of the

UniverseThe density is at

critical density

The temperature

fluctuations are

about one degree

in (angular) size.

Universe is Flat

(expanding indefinitely)

Cosmic Microwave

Background•Small fluctuations in CMB

Fluctuations in the Cosmic

Microwave Background

• Angular size of the CMB fluctuations allows us to

probe the geometry of space-time!

• CMB fluctuations fit the FLAT MODEL universe best

http://wmap.gsfc.nasa.gov/media/060915/060915_CMB_Timeline150.jpg

380,000 years

about 200 million years

13.8 billion years

NASA WMAP confirmed

flatness in 2013

“Over time, gravitational interactions will turn a

mostly uniform, equal-density Universe into one

with large concentrations of matter and huge voids

separating them.” Image credit: Volker Springel.

https://www.forbes.com/sites/startswithabang/2017/02/24/cosmic-superclusters-

the-universes-largest-structures-dont-actually-exist/#1ccf468e15c1

BIG QuestionsWe’ve been dealing with some pretty big questions about the

universe and our fate.

• Form a group & discuss your personal reactions to

discussing questions like the beginning of time and space,

and the ultimate fate of the universe.

• Are you more on the side of “we were not meant to know the

answers” or are humans capable of exploring questions?

• Does it make you nervous to hear about scientists

discussing these issues? Or is it exciting to know that we

can now gather scientific evidence about the origin and fate

of the cosmos?

• In discussing this, you may find that members of your group

strongly disagree; be respectful of others’ points of view.

Standard Big Bang Model leaves some questions

Much of the information after this point has not

been observationally proven.

Scientists answer questions as best we can,

using the information available to us. New

evidence may produce different theories in the

future. This does not mean it’s “just a guess.”

1. Horizon Problem: How is the CMB

the same temperature everywhere

we look?

These areas did not start off close

enough to share a temperature, and

the universe is not old enough for them

to have “mixed” to form one

temperature now.

2. Flatness Problem: Why is the universe flat?

Even a tiny deviation from perfect flatness at the time of the

Big Bang should have been amplified to a huge deviation

today.

Standard Big Bang Model leaves some questions

Solution to Horizon and Flatness Problems*

Inflation: period of sudden expansion during the very early

evolution of the Universe*

--Alan Guth, 1979

Initially tiny (tinier) universe can exchange information so it

looks the same everywhere now (horizon problem)

Also solves

the flatness

problem →

Astronomy, Andrew Fraknoi

Inflation

Four Fundamental Forces –

to understand inflation

Four Fundamental Forces*

• Gravity*

– holding us down

• Electromagnetic*

– magnets, static, electrons in orbit

• Weak*

– radioactive decay (change in P, N, or E)

• Strong*

– holds atomic nuclei together (protons & neutrons)

http://www.astro.upenn.edu/~trilling/teaching/spring2003/lectures/lecture9/s10.html

Inflation Predicts Four Forces Start

as One Force

Forces at the Beginning of Time

Why four forces?• Maxwell united electricity and

magnetism

• Maybe the others used to be united

as well

• High temperature of early universe

could have united them

Gives rise to quantum gravity and

string theory

More Questions About Our Universe

Multiverse? Multi-universes?

Megauniverse?

Extra Dimensions?

Parallel Universe?

No Evidence

– but fun to consider

More Questions About Our Universe

Are we the only ones out there?

Next lecture: Life in the Universe

Homework & Updates• Keep up with Study Points

• D2L Quiz 9-13 available; Quizzes 9-13 for Test 3

• Optional – watch:• Dark Energy, Cosmology part 2: Crash Course Astronomy #43

• Ted Talk: The most mysterious star in the universe by Tabetha Boyajian

• Try out Grade Calculator on class website

• Tutor Oskar available in T bldg. room 3200

• Observations:• Astronomy News Evalution Due Dec. 10 (20 pts) Evaluate astronomy news• Sunset – Part 2 Due Dec. 10 (10 points) Take 2nd picture of sunset in same place

• Take picture about 4pm; sunsets about 4:40pm• Stargazing Due Dec. 17 (20 pts) Go stargazing & write report• Telescope Due Dec. 17 (20 pts) Look through a telescope

• Look at calendar options & weather• Moon Craters Due Dec. 17 (10 pts) Look at magnified moon craters

• Borrow binoculars from Lab room

• Pick up lab notebooks and test today• Let Raquel know if you want to take optional Lab Test 2 on Dec. 10 or 12

Optional – watch:•Dark Energy, Cosmology part 2: Crash Course

Astronomy #43

•Ted Talk: The most mysterious star in the universe by

Tabetha Boyajian

Calendar Summary• Thursday, 12/5: Big Bang & pick up lab notebooks in lecture

• Tuesday, 12/10: Life in the Universe (optional Lab Test 2)

• Thursday, 12/12: Test 3 (60 multiple choice questions)– Based on last 8 lectures & 5 D2L quizzes 9-13

– Some questions from D2L quizzes

– Bring pencil, no calculator needed

– Optional Lab Test 2 during lab time

• Tuesday, 12/17: Final Test today & handback Test 3– Based on all 23 lectures & 13 D2L quizzes (the whole semester)

– Many questions from D2L quizzes

– Bring pencil & calculator if you have one (some in classroom for you)

– Remember lowest of 4 tests is dropped (Test 1, 2, 3, & Final).

– If you took 3 previous tests and are happy with your grade, then you

don’t have to take the Final Test. If you missed a previous test, you

must take the Final Test. If you are trying to increase your grade, take

the final to hopefully drop a different test. No Astronomy on 12/19.