Charles Hakes Fort Lewis College1. Charles Hakes Fort Lewis College2 Outline Final next Monday...

Charles HakesFort Lewis College 1


Outline

• Final next Monday (9:45).• bring a scantron; good eraser, or extra

scantron; sharp pencils• calculator

• Dark Energy • Review


Probable Job Opportunity

• The Academic Success Program regularly funds Astronomy Tutors/ Study Group leaders. If you might be interested in this for next fall, please let me know via email.


Test Topics (recent/new)

• Chapter 13 - Neutron Stars and Black Holes• Shwarzschild radius

• Chapter 14 - The Milky way• Size and Shape• Spectroscopic parallax• Cepheid variables• Mass and dark matter



• Chapter 15 - Normal and Active Galaxies• Standard Candles• Tully-Fisher relationship• Type I supernova• Quasars

• Chapter 16 - Hubble’s Law and Dark Matter• Hubble’s law• Distance ladder• Large scale structure



• Chapter 17 - Cosmology• Big Bang• Age of the universe• Critical density & fate of universe


Chapter 17

Cosmology


Chapter 17Ultra Deep Field - more than 1000 galaxies are in this picture. Total estimate for the universe - ~40,000,000,000.


Cosmology

• How big is the universe?• How long has it been here?• How did it start?• How long will it last?


The Fate of the Universe

• Will it keep expanding forever?• Will gravity cause it to collapse?


Figure 17.5Escape Velocity

• With enough initial velocity, a spacecraft will “escape” from the Earth

• With insufficient velocity, gravity will bring it back to Earth.


Figure 17.6Model Universes



• A high density universe will collapse again into a Big Crunch.

• A low density universe will continue to expand forever.

• Critical density - boundary between the two cases. (9x10-27 kg/m3 = ~5 atoms/m3)

• The ratio of the actual density to the critical density is called o, the critical density parameter.



• If you can determine the density of the universe, you can determine if there will be a Big Crunch or not.




• However - most of the matter in the universe is dark!




• However - most of the matter in the universe is dark!

• Even with dark matter estimates, it appears that o < 1.0, if that is all you look at...


The Accelerating Universe


Figure 17.7Accelerating Universe

• If the universe is “slowing down” because of gravity, distant objects (as seen in the past) should be moving faster.

• Recent measurements show this is not the case - something is accelerating everything.

• That “something” is called Dark Energy.

• This “dark energy” is not understood at all.


Discovery 17-1The Cosmological Constant


Figure 17.8Cosmic Age


http://www.newgrounds.com/portal/view/525347




Current Status of the Universe

• Expanding (and accelerating!) - looks like no big crunch for us.

• Composition - looks like o=1, the critical density parameter.• Normal Matter ~ 4%

• Mostly H and He• Dark Matter ~23%• Dark Energy ~73%


Big Bang Events• Inflation - needed to get a uniform density in the

universe. (<~10-32s!) • Nucleosynthesis - most of the He (~25% of normal

matter) formed in the first 15 minutes of the universe. The rest was left as H.

• Microwave Decoupling (atom formation) - once electrons joined the nuclei, then photons were no longer scattered and the universe became transparent. After a few 10,000s of years.

• Large Scale Structure - normal matter “clumps” around the dark matter.

• Finally acceleration by dark energy.


The concept that on the grandest of scales, the universe is similar in appearance everywhere is:

A) general relativity.

B) special relativity.

C) homogeneity.

D) isotropy.

E) universality.


ADT


How confident were you about your answers on the Astronomy Diagnostic Test

A) very confident.

B) somewhat confident.

C) not very confident.

D) just guessing.


Why is it cold at the North Pole, even during northern hemisphere summer?

1 - Because the “pole” itself doesn’t point very close to the direction of the Sun

2 - Because there are fewer daylight hours at the pole than at lower latitudes (e.g., Durango)

3 - Because of the high altitude at the pole

4 - Because the pole is further away from the Sun than lower latitudes are (e.g., Durango)


Star A has a parallax shift of 0.4 arc second Star B has a parallax shift of 0.6 arc seconds

1: B is 1.5 times as far away as A

2: Star A is at a distance of 4 parsecs (pc)

3: Star B is at a distance of 1.66 parsecs (pc)

4: Star A is 0.4 times as far away as B


Which is correct?

1 - The new moon rises at noon.

2 - The first quarter moon rises at noon.

3 - The full moon rises at noon.

4 - The third quarter moon rises at noon.


In Paris, France (50 degrees north latitude), what is the longest day of the year?

1: March 21

2: June 21

3: September 21

4: December 21


Where along the horizon does the Sun rise on June 21 in Paris, France?

1: Due east

2: North of east

3: South of east

4: Can’t tell with information given


Where along the horizon does the Sun rise on June 21 in Paris, France?

1: Due east

2: North of east

3: South of east



Where along the horizon does the Sun rise on June 21 in Sydney, Australia?

1: Due east

2: North of east

3: South of east



On December 21, in Durango, if there is a full moon, where does it rise?

1: Due east

2: Almost due east (within 5 degrees)

3: South of east (by more than 5 degrees)

4: North of east (by more than 5 degrees)


On December 21, in Durango, if there is a full moon, where does it rise?

1: Due east





On December 21, in Australia, if there is a full moon, where does it rise?

1: Due east





A 5 meter (diameter) telescope

1 : gathers 5 times as much light as a 1 m telescope

2 : gathers 1/2 as much light as a 10 m telescope

3 : gathers 4 times as much light as a 2.5 m telescope



A 5 meter (diameter) telescope

1 : gathers 5 times as much light as a 1 m telescope


3 : gathers 4 times as much light as a 2.5 m telescope



Which statement about planetary orbits is incorrect?

A) All planets orbit the Sun counterclockwise.

B) Most stay close to the earth's equator in the sky.

C) Most orbits are almost circular, with low eccentricities.

D) All have the Sun at one focus of their elliptical orbits.

E) Most also rotate counterclockwise on their axes as well.


Iron meteorites are believed to come from:

A) the core of a differentiated asteroid, now broken up.

B) the crust of a differentiated asteroid, now broken up.

C) a broken up cometary nucleus.

D) debris from the Kuiper Belt.

E) interstellar space.


Long-period comets are believed to originally come from:

A) the asteroid belt.

B) the Kuiper belt.

C) the Oort cloud.

D) the satellite system of Jupiter.

E) the interstellar medium.


The impact of a fragile body in June 1908 produced a huge explosion over:

A) northern Canada.

B) Alaska.

C) Siberia.

D) Mars.

E) the Moon.


In what part of the atmosphere does life occur?

A) exosphere

B) stratosphere

C) mesosphere

D) ionosphere

E) troposphere


Which planet shows the widest range of surface temperatures between day and night?

A) Mercury

B) Venus

C) Earth

D) Mars

E) Uranus


Which body has the densest atmosphere?

A) Mercury

B) Venus

C) Earth

D) Mars

E) our Moon


Which of these gets brightest; so bright as to be seen during daylight at times?

A) Mercury

B) Venus

C) Mars

D) Jupiter

E) Saturn


Assume a planet orbits exactly three times as far from the Sun as the Earth.

1 - It’s period is 3 years exactly.

2 - It’s period is between 3 and 5 years


4 - It’s period is 7 years or more.


Assume a planet orbits exactly three times as far from the Sun as the Earth.

1 - It’s period is 3 years exactly.



4 - It’s period is 7 years or more.


Two planets have orbits with the same sized semi-major axis. Which is true?

1 - The planet with the most eccentric orbit moves faster all the time.

2 - The planet with the most eccentric orbit moves faster some of the time.

3 - The planet with the most eccentric orbit never moves faster.

4 - Not enough information to answer.


A fast moving freight train hits a car. The car is destroyed and the train isn’t, so…

1 - the magnitude of the force of the train on the car is greater than the magnitude of the force of the car on the train

2 - the magnitude of the force of the train on the car is smaller than the magnitude of the force of the car on the train

3 - the magnitude of the force of the train on the car is equal to the magnitude of the force of the car on the train

4 - none of the preceding


Which has the most kinetic energy?

1: A 1 kg Mass with velocity 4 m/s.





Which has the most kinetic energy?






Which mass pair has the greatest gravitational force between them?

1: A 5Msolar mass and a 4Msolar mass separated by 4 AU.





Which mass pair has the greatest gravitational force between them?






Two planets have orbits with the same periods. Which is true?

1 - Their velocities must be the same.

2 - They must have the same eccentricity.

3 - They must have the same semi-major axis.

4 - They must collide with each other.


Temperature

Which feels hotter?

1: 300° F 2: 300° C 3: 300° K


Temperature

Which feels hotter?

1: 300° F 2: 300° C 3: 300° K

(Fahrenheit ) (Celsius) (Kelvin)


Assume that the Sun rises at 6:00 A.M. What time does the third quarter Moon rise?

1: 9:00 A.M.

2: 12:00 noon

3: 9:00 P.M.

4: 12:00 midnight


You are in Paris, France (50 degrees north latitude), on June 21.

What is the highest angle above the horizon that the Sun achieves?

1: 16.5° above the Southern horizon





You are in Paris, France (50 degrees north latitude), on June 21.

What is the highest angle above the horizon that the Sun achieves?






Observing from a latitude of 25° North

1 - The star Polaris appears about 65° above the horizon.

2 - The celestial equator has a maximum height of 65° above the horizon.

3 - The star Polaris appears about 25° north of the zenith point.



Observing from a latitude of 25° North

1 - The star Polaris appears about 65° above the horizon.


3 - The star Polaris appears about 25° north of the zenith point.



The universe became transparent to radiation during:

A) NucleosynthesisB) DecouplingC) Structure FormationD) Cosmic Acceleration


According to standard Big Bang theory, if Ho=50km/s/Mpc, the maximum universe age is:

A) 12 billion yearsB) 14 billion yearsC) 17 billion yearsD) 20 billion years

Charles Hakes Fort Lewis College1. Charles Hakes Fort Lewis College2 Outline Final next Monday...

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