Unit 1 Flashcards
Importance of the Night Sky (Before)
Survival
Timekeeping
led to the development of calendars
Early Observations of the Night Sky
Periodic Motion
Planets (5 points of light) (Dirty mirrors) (Wonders)
5 Early Points of Light (Wonders)
Mercury
Venus
Mars
Jupiter
Saturn
Zenith
Looking Straight Up from where you are
Nadir
Looking Straight Down from where you are
Stars at the North Pole (90 Degrees latitude)
Circles the zenith
Do not rise or set
Stars at the Equator (0 Degrees latitude)
The Stars rise Straight Up and Set Straight Down
Stars at Intermediate Latitude
Stars rise and set at an angle to the horizon
Celestial Sphere
An Imaginary Sphere that surrounds Earth
Divided into 88 Sections
containing all constellations
Constellations
13 of them
the sun passes through them during the year
Ophiuchus 13th one (Early December)
The Celestial Tilt
The Equator is tilted by 23.5 degrees to the ecliptic
Reason for seasons
Sun in the Winter
The sun is lower in the sky
rays spread out over a wider area (less effective at heating)
Winter solstice Dec 21
Rotation of the Moon
Rotates around Earth in ~29.5 days
Rotates around itself
It rotates the same period that it revolves so we always see the same side of the moon
Sun in the Summer
The sun is higher in the sky
hits Earth more directly (Spearding out less)
Summer solstice on June 21
Phases of the moon
New moon, waxing cressent, first quarter, waxing Gibbous, Full, winning Gibbous, Third Quarter, Waning Crescent
Lunar Eclipse
The Moon going through Earth’s Shadow
Takes 2 to 3 hours
Happens twice a year
Blood Moon
During a lunar Eclipse when the moon is fully covered by the Earth’s shadow
Solar Eclipse
The moon casts a shadow on the Earth (100 - 150km wide)
At best 7 min
partial is more common, full is less common
The sun Corona
During a solar Eclipse when the moon is fully covering the sun
we only see the solar atmosphere called corona
only safe time to look at solar eclipse without protection
Geocentric Model
Created by Ptolemy
Earth was the center of the universe
Each planet orbits a small circle called an Epicycle
Each Epicycle orbits a larger circle called a different
Nicolaus Copernicus
Doubted the Geocentric model
Sugested the heilocentric model
Heliocentric Model
The Sun is the center of the universe
orbits were drawn as a circle (Wrong)
Tycho Brahe
Believe Copernicus (Heliocentric model) couldnt prove it
use instruments to very acuretly measure the altitude of celestial objects
Johannes Kepler
German Mathematician and Astronomer
Discovered basic laws, describing the heliocentric cosmology on a a firm mathematical basis
Keplers Laws
1st Law:
Planets orbited the sun in elliptical paths
2nd Law (Law of Equal Areas):
Planets orbit the Sun in elliptical paths, with the Sun at one of the two foci of the ellipse. This means that a planet’s distance from the Sun varies during its orbit.
closer = faster (Perihelion)
further = slower (Aphelion)
3rd Law:
The orbital period of an object is related to its distance from the sun
P^2 = A^3
p = Orbital period (Years)
A = average distance from the sun (Astronomical units)
Galileo Galilei
verified Kepler’s work
Craters on the moon
Phases of Venus
Refracting telescope
phases of Venus
Just like the moon Venus has phases
Takes place over a couple of 100 days
proved the heliocentric model
Scientific Method
- Identify a problem
- gather data
- assert a hypothesis
- test the hypothesis
- compare the results, and iterate.
Laws of Nature
Rules: Scientific laws represent the “rules” that govern the behavior of the natural world.
Universality: These laws are believed to apply consistently throughout the universe.
Changeability: Scientific theories, models, and laws can change based on new evidence or discoveries.
SI units
System international
Time –> Seconds
Distance –> Meters
Mass –> kilograms
Issac Newton
Laws of Motion
gravity
optics
Newton’s Laws of Motion
1st Law (Law of inertia):
An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force
2nd Law (F = ma):
The change of motion of an object is proportional to the direction of the force acting on it
(Force = Mass * Acceleration)
3rd Law: (Action and Reaction):
For every action, there is an equal and opposite reaction
Gravity
The gravitational attraction between two bodies is proportional to their masses
The greater the mass, greater the gravitation pull
F = G * m1 * m2/ R^2
F (N), m (KG), R (m), G the universal gravitational constant
Inverse Square Law
Double the distance from a source, the intercity diminishes,
ex. double the distance intercity decrease by 1/2*2 = 1/4
P^2 = A^3 (Most general form)
P^2 = 4pi^2 a^3 / G (M1 + M2)
Mass
Is Intrinsic
weight is (w = m g)
Challenges of weightlessness
Phycological changes
Motion sickness
Calcium depletion
Eyeballs lose their shapes
Density
Amount of material that exits within a given volume
p(density) = m (Mass) * v (Volume)
water has a density of 1 gm.cm^-3
gold has a density of 19 19 gm.cm^-3
