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EXAM #1 - PHYSICS chapter 1
Terms in this set (60)
is a science.
Science comes from latin "scientia" meaning knowledge
Hierarchy structure f
planet, solar system, milky way, local group, local supercluster
INFO on Earth
2500 years ago Earth is a sphere
400 years ago Earth is a planet around the sun
80 years ago milky way is the galaxy
a large, glowing ball of gas that generated heat and light through nuclear fusion
large object that orbits a star
shines by reflected light from a star
may be rocky, icy or gaseous in composition
an object that orbits a planet
ex: ganymade orbits jupiter
small and rocky object that orbits a star
relatively small and icy objects that orbits a star
they have tails only when they come close to the sun, not far apart
little lander that could
a star and all material that orbits it, including its planets and moons
an interstellar cloud of gas and or dust
a great island of stars in space, all held together by gravity and orbiting a common center
milky way galaxy is
a disk shaped collection of more than 100 billion stars, including the sun
sum total of all matter and energy; that is everything within and between all galaxies
finite speed 300,000 km/s
moon= 1 second
sun= 8 minutes
sirius = 8 years
andromeda galaxy= 2.5 million years
- the father away we look in distance, the further back we look in time
distance light can travel in 1 year
about 10 trillion kilometers - 6 trillion miles
unit of distance not time
1 light year= speed of light x 1 year
at great distances
we see objects as they were when the universe was much younger
why cant we see a galaxy 15 billion light years away?
looking 15 billion light years away means looking at a time before the universe existed
earth-sun distance an astronomical unit
1 AU is about 150 million kilometers (93 million miles)
On our 1 AU = 1 meter scale, it's just a few minutes' walk to Pluto (~40 yards).
How far would you have to walk to reach Alpha Centauri? (268,144 m)
how big is the universe?
milky way is one about 100 billion galaxies
1011 stars/galaxy x 1011 galaxies = 1022 stars
It has as many stars as grains of (dry) sand on all Earth's beaches.
what is the observable universe?
A)The sum total of all matter and energy.
B) All of the stars and planets that can be observed with the naked eye.
C)Everything out to a distance of about 14 billion light-years from Earth.
D)The Milky Way Galaxy and its neighboring galaxies.
C: everything out to a distance of about 14 billion light years from Earth
When we look at the most distant observable objects in the universe, we see them:
A) as they were about 4.5 billion years ago.
B) as they were about 14 billion years ago.
C) as they are now.
D) as they were at some time in the past, depending on which direction we are looking.
How did we come to be? #1
EARTH OF THE UNIVERSE:
began with hot and dense big bang.
, based on the observed rate of expansion, we conclude that the universe is about 14 billion years old.
#2: galaxies as cosmic recycling plants
the early universe combined only 2 chemical elements: hydrogen and helium
All other elements were made by stars and recycled from one stellar generation to the next within galaxies
#3: life cycles of stars
many generations of stars have lived and died in the Milky Way
#4: Earth and Life
by the time our solar system was born, 4 1/2 billion years ago about 2% of the original hydrogen and helium had been converted into heavier elements. we are therefore the star stuff because we and our planet are made from elements manufactured in stars that lived and died a long time ago
How do our lifetimes compare to the age of the universe?
cosmic calendar: a scale on which we compress history of the universe into 1 year
Since we are compressing the 14-billion-year history of the universe into one calendar year, 1 month represents about 1.2 billion real years, 1 day represents about 40 million years; 1 second represents about 440 years.
Jan 1: Big Bang
FEB: milky way forms
september 3: Earth forms
September 22: Early life on Earth
Dec 17: Cambrian explosion
Dec 26: Rise of the dinosaurs
Dec 30: Extinction of the dinosaurs
Dec 31 @ 9 pm : Early hominids evolve
DEC 31 @ 11:58 modern humans evolve
25 seconds ago agriculture arises
11 seances ago pyramid built
1 second ago kepler and Galileo show the earth orbits the sun
You and I were born about 0.05 seconds before midnight, Dec. 31.
How is Earth moving through space?
earth rotates on its axis once a day
Point out that most of us are moving in circles around the axis at speeds far faster than commercial jets travel, which is why jets cannot keep up with the Sun when going opposite Earth's rotation...
Does your position on Earth affect the speed you are moving through space due to the Earth's rotation?
Earth orbits the Sun (revolves) once every year...
at an average distance of 1 AU ≈ 150 million km.
with Earth's axis tilted by 23.5º (pointing to Polaris).
and rotates in the same direction it orbits,
counter-clockwise as viewed from above the North Pole
Our second motion is ORBIT. Point out the surprisingly high speed of over 100,000 km/hr.
our sun moves
randomly relative to the other stars in the local solar neighborhood...
at typical relative speeds of more than 70,000 km/hr...
but stars are so far away that we cannot easily notice their motion...
and it orbits the galaxy every 230 million years.
Our third and fourth motions are MOTION WITH THE LOCAL SOLAR NEIGHBORHOOD and ROTATION OF THE MILKY WAY GALAXY.
how do galaxies move within the universe ?
Hubble discovered that
all galaxies outside our Local Group are moving away from us.
the more distant the galaxy, the faster it is racing away.
Conclusion: We live in an expanding universe.
how is Earth moving in our solar system?
It rotates on its axis once a day and orbits the Sun at a distance of 1 AU ≈ 150 million km.
Stars in the local neighborhood move randomly relative to one another and orbit the center of the Milky Way in about 230 million years.
how do galaxies move within the universe?
All galaxies beyond the Local Group are moving away from us with expansion of the universe: the more distant they are, the faster they're moving.
How has the study of astronomy affected human history?
The Copernican revolution showed that Earth was not the center of the universe (Chapter 3).
Most ancestors believed that the heavens revolved around the Earth.
Sun, Moon, planets and stars
appear around our sky each day.
We cannot feel the constant
motion of the Earth as it rotates
on its axis around the sun.
Earth-centered, or geocentric,
View of the universe.
We now know that Earth is a planet
orbiting a rather average star in a
Which of the following lies in the ecliptic plane?
Earth's orbital path around the sun
In January, Earth's rotation axis points in the direction of the star Polaris. Where does it point in July?
toward the star of polaris
rRegarding the history of the universe, which of the following is true?
All the chemical elements were created during the Big Bang, but some have been modified since that time as a result of radioactive decay.
All the current stars in our galaxy formed about the same time billions of years ago.
Key elements of which Earth and life are made, including carbon, oxygen, and iron, did not exist when the universe was born and were created later in stars.
The Earth formed quickly after the Big Bang.
Which of the following are real motions of our "spaceship Earth"?
Earth and our solar system moves with the Milky Way galaxy relative to other galaxies in our Local Group.
Earth orbits the Sun.
Earth moves with the Sun on an orbit around the center of the Milky Way galaxy.
The term observable universe refers to _________.
that portion of the universe that we can see in principle, given the current age of the universe
On a scale where the Sun is about the size of a grapefruit and the Earth is about 15 meters away, how far away are the nearest stars besides the Sun?
about the distance across the United States
What is the "Raisin Cake model" intended to explain?
that every raisin in a raisin cake moves farther away from every other raisin: there is no special central raisin (and no special central galaxy)
What do astronomers mean by the Big Bang?
he event that marked the beginning of the expansion of the universe
Rank the galaxies from left to right based on the amount of time it has taken their light to travel to Earth, from the longest time to the shortest time.
10 billion light years
5 billion light years
2 billion light years
800 million light years
230 million light years
70 million light years
This time, rank them from left to right based on the age of the universe at the time these galaxies emitted the light we receive from them today, from oldest (closest to today) to youngest (furthest back in time).
70 million light years
2 billion LY
5 Billion LY
What do we mean when we say that the universe is expanding
average distances btw galaxies are increasing with time
All objects in the universe, including Earth and everything on it, are gradually growing in size.
The average distance between galaxies is increasing with time.
The average distance between stars in the Milky Way Galaxy is increasing with time.
The universe itself is not growing, but our knowledge of the universe is increasing with time.
The observable universe is growing larger in radius at a rate of one light-year per year.
Note that an observer located at the Local Raisin would see Raisins 1, 2, and 3 all move away from her during the video. What would an observer located at Raisin 2 see?
staying in same place
As the cake expands, the separation between Raisin 1 and Raisin 2
The raisins stay roughly the same size as the cake expands, just as galaxies stay roughly the same size as the universe expands.
The average distance increases with time both between raisins in the cake and between galaxies in the universe
An observer at any raisin sees more distant raisins moving away faster, just as an observer in any galaxy sees more distant galaxies moving away faster.
Based on what you've learned from the raisin cake analogy, which two properties of distant galaxies do astronomers have to measure to show that we live in an expanding universe?
their distances and speeds
The Andromeda Galaxy is faintly visible to the naked eye. When you look at the Andromeda Galaxy, the retina of your eye is absorbing light that has traveled through space for ______ to reach you.
2.5 million years
Which of the following is a general difference between a planet and a star?
Stars glow in infrared and visible light, while planets glow only in the infrared.
The fact that nearly all galaxies are moving away from us, with more distant ones moving faster, helped us to conclude that:
universe is expanding
1 astronomical unit (AU)
Earth's average distance from the Sunabout 150 million kilometersJupiter lies about 5.2 of these from the Sun
1 light year
the distance light travels in 1 yearabout 10 trillion kilometersthe star Sirius lies about 8 of these from the Sun
if starts existed but galaxies did not
bc we are made of material that required recycling in galaxies
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