Download Cosmic Landscape Introduction Study Notes About how

Cosmic Landscape Introduction Study Notes
About how much bigger in radius is the Sun than the Earth?
The ratio of the Sun's radius to the Earth's radius is
1,392,000/12756 = 109.1
How big is an astronomical unit?
Definition of astronomical unit. For general reference, we can say that one astronomical unit (AU)
represents the mean distance between the Earth and our sun. The AU is approximately 150 million
kilometers or 93 million miles. It is approximately 8 light-minutes.
Roughly how big across is the Milky Way Galaxy?
The Milky Way galaxy is the home of the Sun and our solar system. There are 200 billion other stars in
the Milky Way galaxy too. Our galaxy is a spiral galaxy, with a bulged center and arms that start in the
center and form a flat pinwheel shape. The galaxy is about 90,000 light-years across. The Sun is located
about two-thirds of the way out from the center in the Orion Arm.
How is a light-year defined?
A light-year is a unit of distance. It is the distance that light can travel in one year. Light moves at a
velocity of about 300,000 kilometers (km) each second. So in one year, it can travel about 10 trillion km.
More precisely, one light-year is equal to 9,500,000,000,000 kilometers.
What force holds the different astronomical systems described in this section together?
Gravity keeps the crust of the Earth, where we live, attached to the planet. Gravity keeps the planets,
comets, and asteroids of the solar system bound in orbit around the Sun. Gravity keeps the Sun in orbit
around the center of the Milky Way. Gravity keeps the Local Group of galaxies together.
What other forces exist in nature?
Other forces include the electromagnetic force, the strong force, and the weak force.
What particles make up an atom?
The three main subatomic particles that form an atom are protons, neutrons, and electrons.
What force holds the electrons to an atom's nucleus?
The strong forces oppose the electromagnetic force of repulsion between protons. Like ”glue” the
strong force keeps the protons together to form the nucleus. The strong forces and electromagnetic
forces both hold the atom together.
What was the Big Bang? What are dark matter and dark energy?
The Big Bang was the event that, according to many astronomical theories, created the Universe. It
occurred about 13.7 billion years ago and generated the expanding motion that we observe today.
Dark matter is matter that emits no detectable radiation but whose presence can be deduced by its
gravitational attraction on other bodies. Dark energy is a form of energy (or a cosmological constant)
detected by its effect on the expansion of the Universe. It causes the expansion to speed up. The nature
and properties of dark energy are unknown.
What is meant by the scientific method?
The scientific method is the process of observing a phenomenon, proposing a hypothesis on the basis of
the observations, and then testing the hypothesis.
What is the difference between a hypothesis and a theory?
A hypothesis is an explanation proposed to account for some set of observations or facts; a theory is a
set of ideas that have achieved wide acceptance by successful testing.
You write your home address in the order of street, town, state, and so on. Suppose you were writing
your cosmic address in a similar manner. Which of the following is the correct order?
Earth, Solar System, Milky Way, Local Group
Ancients believed the planets to be special compared to stars because ?
over time the planets appear to move against background stars.
The light-year is a unit of ?
Distance
Which of the following astronomical systems is/are held together by gravity?
(a)
The Sun
(b)
(c)
The Milky Way (d)
(e)
All of them are.
The Solar System
The Local Group
What do astronomers mean when they say that the Sun is a fairly typical star?
Some stars are many times more massive and some many times less massive than the Sun.
The Sun orbits the center of the Milky Way at a much higher speed than would be expected based on
the mass of visible stars. What do astronomers think probably explains this discrepancy?
Dark matter.
We humans tend to think of everything in terms of us. For example, how do we define the Astronomical
Unit (AU)?
Average distance between Earth and Sun.
We call it the Solar System because the Sun is immense, relative to any of its planetary satellites. Let's
consider a sense of the scale between us and our star. About how much larger in radius is our Sun than
our Earth?
About a hundred times
Refer to figure 1.7 in your text. The width of a football field is 53 yards, so in the football field model,
which planet has the largest orbit that could fit entirely onto one regulation field?
Mars
What is true of Pluto that is NOT true of any of the 8 major planets?
Pluto's orbit is crossed by a body larger than it.
Most planets also have satellites of their own. Let's consider the scale of their orbits relative to our own
Moon's orbit on the football field model (refer to figure 1.7). For example, Jupiter's large satellite
Callisto has an orbit around Jupiter about 5 times bigger than our Moon’s orbit around the Earth; in the
football field model, which would best describe the size of these orbits around Jupiter?
a dinner plate
Describe the four fundamental forces in the known Universe.
The Strong Force - This force is responsible for binding of nuclei. It is the dominant one in reactions and
decays of most of the fundamental particles. This force is so strong that it binds and stabilize the protons
of similar charges within a nucleus.
The Electromagnetic Force - This is the force which exists between all particles which have an electric
charge.
The Weak Force - This force is responsible for nuclear beta decay and other similar decay processes
involving fundamental particles.
The Gravitational Force - This is the force that holds us onto the Earth. It could be important in our daily
life, but on the scale of atomic world it is of negligible or no importance at all. Gravitational force is
cumulative and extended to infinity. It exists whenever there is matter. Your body is experiencing a
gravitational pull with, say, your computer (or anything close to you or as far away as stars and galaxies)
but the effect is so small you will never sense it.
Smart: specific – measurable – achievable – results focused – time bound goals
Traits of successful students –
The difference between who you are and who you want to be is?
What we do.
Astronomy is?
Astronomy is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and
phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation).
On Earth our nearest neighbor is? What distance is it away from Earth?
The moon is our nearest neighbor. The moon orbits Earth at a mean distance of just over 384,000km
THE MOON IS EARTH'S CLOSEST NEIGHBOR IN SPACE, BUT IT IS STILL FAR AWAY. The Earth-moon
distance is about 250,000 miles (actually 239,000 miles).
Given that an astronomical unit is 1.5×108 kilometers and a lightyear
is about 1013 kilometers, how many AU are in a lightyear?
Amount: 1 light-year (ly) of distance
Equals: 63,241.08 astronomical units (au - ua) in astronomy length