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Flashcards in Ch 3 : History of astronomy Deck (46)
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What were the purposes of ancient astronomy?

1. predict weather patterns (seasons and such)
2. To assist travelers


Give two examples of tools ancient astronomers built?

Mayan pyramids, stonehenge


How much do the stones weigh in stonehenge? How far were they transported? What events do the stones align with?

Built over 1700 years ago. (2800BC)
50 tonne stones. 200km.

summer solstice sunrise aligns with the heel stone. alignments for the winter solstice and Equinoxes are also evident.


List three other ancient calendars

wooden circles in UK
Big horn medicine wheel, Wyoming
Chaco Canyon Sun Dagger.


What nation discovered guest stars? what were they?

the guest stars were supernovas, ike SN-1054 (now the crab nebula).
they also made super detailed maps of the stars


Where did the term Zenith and Azimuth come from?
what else did these people name?

Arabic astronomers.
also named stars like Betelguese and Rigel.
in additiion they had a mathimatical understanding of the moon's behavior.


Which of these space objects was NOT catalogued by ancient
A. Planets
B. Asteroids
C. Supernova
D. Stars
E. Comets



What are main accomplishments of ancient Greek astronomers?

distinguished between planets and stars (and the sun and moon. knew they were all diff types of objects)
(planet= wanderers)

also realized planets moved along the ecliptic,, and occasionally moved in retrograde.


What did Plato believe?


PErfection of the heavens.
objects are circles. orbits are circles. I am a circle. perfect circles. wow.

even the stars orbit all together in one big sphere.



who is he?
what did he do?

Plato's student

developed a system of 27 spheres to describe the motion of the heavens mathmatically.
this was accurate for up to five months.


where do his arguments stem from?
what did he actually do?

All of his argeuments stemmed from first principles, which were beliefs that are obviously true. (nat stae of objects is to be at rest, so obvs, the earth is also at rest)
this idiot was considered an authority on a lot of things, and he really set us back.

He modified Euxdoxus's 27 spheres to a 55 sphere model.


what's his deal?

310-230 BCE
propsed the idea that the earth rotated around the sun.
also the first person to wonder how far away the sun is.
he tried to calculate it with triangulation, but was pretty far off.

thanks to Ari prime, he was ignored.



276-195 BCE
calculated the radius of the earth by measuring the angle of the shadow in two different cities.

he was accurate to 10%
hot damn, boi


what did he do?
why was he good?

Made an advanced mathamatical model of geocentric universe.

used deferent (primary path) and epicycles ((an orbit around a point on the deferent).

needed 80 spheres to describe motion

model held for centuries, but was a little off.


Which of these is not explained by Ptolomy’s geocentric model?
a. The noon Sun changes position/height in the sky with the seasons
b. The Earth appears to be flat
c. Sun, Moon and stars follow smooth paths
d. The planets periodically travel in retrograde
e. The Earth feels like it is stationary

b. earth appears to be flat


what was his deal?

was his model superior to Ptolematic model?

HE developed a heliocentric model, that could NOT predict planetary motion.
used 9 spheres.

not superior bc he couldn't predict movements of planets, even though he had a cleaner explaination for retrograde motion (no epicycle).


What are the six principles of the copernician model?

1. Orbits are circular
2.There isn't one common center of orbit.
3. the Earth is centre of all gravity and moon's orbit. the planets orbit the sun and have no gravity.
4. the stars are much much farther away.
5. the motion of the stars and the Sun is due to rotation of earth on it's own axis.
6. the retrograde motion of the planets is due to Earth's orbit.


What were galileo's
revolutionary observations via telescope? (4)

1. Moon had craters
2. Sun had spots
(perfect artisotle? I think not)
3. Saw four of jupiter's moons.
(our moon isn't special, they can orbit things other than earth)
4. venus's phases didnot match up with a geocentric model


Was Galileo imprisoned for heresy?

No. he was buddies with the pope, and got in trouble for breaking a contract in which he stated he would not publish his findings. The church asked him to wait to publish, but galileo waits for no ma!


Tycho Brahe - Actual contributions.

giant sextant

Idiot with a telescope.
Tried to make a new geocentric model in which all other planets orbited the sun

discovered that the celestial sphere was NOT unchanging (FU Ari) through observations of a supernova (gest star, didn't show parallax.)

Spent a lot of time recording positions of celestial objects (wuth date and time).
super accurate.


Kepler (as recruited by Tycho)

The numbers guy.
used Keplers data and triangulation techiniques to find patterns in Tycho's data.
He did this for 29 years.


What were Kepler's key techniques?

!. all distances referenced as multiples of earth's orbit
2. Accounted for sun moving about earth at 360/360 degrees per day. (Tycho's model)


Kepler's Laws

1. the orbits of the planets are ellipses with the Sun at one focus (see slide).

2. As a planet orbits the Sun, it sweeps out equal area wedges in equal
amounts of time. (moves faster when closer to sun.)

3. The SQUARE of a planet's orbital period (T) is equal to the CUBE of it's semimajor axis (a)


what is the eccentricity of a circle?

e=.95 for a very long ellipse

e= FD/major axis

see diagram in notes.


Draw and lable the elliptical orbits for a planet around the sun, and for the orbit of OUR moon around the earth.

state the general terms for any orbit.

Aphelion - Perihelion = Focal Distance
Perihelion + Aphelion = Major Axis


Who finally provided the evidence that finally had geocentric theory rejected? What was it?

Tycho and Kepler.

changing heavens (supernova) via Tycho and Kepler's realization of imperfect orbits.


What data was used to determine Kepler's first and second laws?

How many years did it take to form law three?

Only Mars data.

10 years, with data from other planets to prove T^2w=a^3
Orbital period ^2 =Semi major axis ^3


kelper's laws could be used to calculate orbital distances using only one earth based measurement.

when was a decent measurement first made?



What kind of laws are Keplers?

work for planets, need to be mod for moons.


What is a prescriptive law?

Prescriptive laws explain how and why things work in regards to more than one system.

descriptive laws just explain what's happening.


Which of these statements is true?
a. Kepler’s Laws are the mathematical description of the Copernican
b. Kepler’s Laws are incompatible with Copernicus, because Kepler was
trying to prove geocentricity.
c. Kepler’s Laws are incompatible with Copernicus, because Copernican
orbits were perfect circles.
d. Copernicus was aware of Kepler’s Laws and used them as the
foundation for his revolution



(unimp) who said
“Newton was not the first of the age of
reason, he was the last of the magicians.”

John Maynard Keynes


State Newton's first law

Everything in motion or at rest, continues on in that state until acted upon by an external force.

Things stay the same until a force acts on them.


State Newton's second law


When an object is affected by an unbalanced force, the results an acceleration inversly proportional to the mass of an object.

therefore, twice the mass, half the acceleration

accleration and mass are inversely proportional.


Rule three (newton)

For ever action there's an equal and opposite reactions.

every force occurs in pairs.


Gravitation: what are the two things Newton has to say

1. Any object with mass exerts a gravitational force on any other object with mass.

2. Gravitational FORCES ARE ALWAYS ATTRACTIVE. (it's the only one)


What is inverse square law?

F = G (m1m2)/(r^2)

States force depends on the mass of both objects and the INVERSE of the SQUARE of the DISTANCE between them.

The further away you are, the more the forces decrease.


Newton's laws explain Kepler's laws. Which one turns out to be incorrect?

Explain how the other two relate.

Law three is incorrect.

1. Orbits are elliptical. Y?
Because they continue in a straight line until they are affected by an external force ( the sun's gravity)

2. Orbits sweep equal areas in equal amounts of time. Newton's laws give us the law of conservation of angular momentum.


3. the focus of the elipse is actually the centre of mass, which is affected by the gravity from other planets, so the focal point and eccentricities are always changing.
T^2= a^3/ M(total)


What Langrange Points
What are they?
Draw and lable them (5) (see notes)

L points= locations with the same orbital period but with different locations from an orbiting body


Which of these statements is true about the force of gravity between
the Earth and the Moon?
a. The Earth exerts a larger force of gravity on the Moon than the Moon
exerts on the Earth
b. The Moon exerts a larger force of gravity on the Earth than the Earth
exerts on the Moon.
c. The Moon exerts the same amount of force on the Earth as the Earth
exerts on the Moon.
d. The gravity of the Moon is not comparable to the gravity of the Earth



One of the postulates of special relativity states that the speed of
light, when measured in a vacuum, is constant for all observers.
a. True
b. False


You can't add or subtract the speed of light from other vectors, man.


Stellar parallax. What is it? who discovered it? When?

Star is in different position depending on the time of year.
1728 James Bradley made claim.
1838 Freidrich Bessel confirmed, since the technology was finally good enough to "prove" it.


Einsteins special relativity theory states what?

The light is the maxium possible speed in the universe. The speed of light in a vacuum is the same in all frames of reference.


Einstein's Genera relativity

Gravity doesn't produce a farce, instead if curves/warps space-time, resulting in an acceleration towards the centre of gravity.

This matters because it explains why light (something with no mass) is affected by gravity


What is proof of einstein's theories in astronomy



Which of these is not a part of the geocentric model?
Select one:
a. The Earth feels like it is stationary
b. The planets periodically travel in retrograde
c. Sun, Moon and stars follow smooth paths
d. The noon Sun changes position/height in the sky with the seasons
e. The Earth appears to be flat

earth appears to be flat