Lecture 1

Question 1

Scientific method

Answer 1

The scientific method is a procedure for formulating hypotheses about the universe.
These are tested by observation
or experimentation in order to build consistent models or theories that accurately describe phenomena in nature

gather facts –> guess an explanation –> test hypothesis –> modify hypothesis

Question 2

What is the closest star to Earth ?

Answer 2

the sun

Question 3

What is the second closest star in the sky ?

Answer 3

Proxima Centauri

Question 4

What is the brightest star in the sky ?

Answer 4

sun

star sirius is the second brightest star

Question 5

How long does it take Earth to rotate once on its axis ?

Answer 5

24 hours

Question 6

How long does it take Earth to orbit once around the Sun?

Answer 6

1 year (365 days)

Question 7

Does the moon move? If so, how?

Answer 7

Yes!
- Moon orbits earth once every 28 days
Moon also rotates on its axis

Question 8

Why do we have Day and Night

Answer 8

The side facing the sun has daylight

The other side has darkness (night-time)

Question 9

Astronomy is the study of…

Answer 9

the Universe:
the totality of all of space, time, matter and energy.

It is a subject like no other – we need to change our perspective of size, scales and times unfamiliar to us

The universe is HUGE! So we must think BIG!

Question 10

Astronomers measure length in

Answer 10

meters, astronomical units and light years

Question 11

what is a astronomical unit

Answer 11

Its  the distance from the earth to sun 
1 astronimcal unit (AU) 
= 1.5x10^11 meters 
or 
= 150 million kilometers

Question 12

What is a lightyear

Answer 12

Distance traveled by light in one year . 
Its a measure of length not time 
1 light year (ly) 
= 9.5 x10^15 
or 
=63,000 AU

Question 13

Astronomers measure time in

Answer 13

seconds and years

Question 14

Astronomers measure mass in

Answer 14

kilograms

Question 15

what is a star

Answer 15

– large burning ball of gas

Question 16

what is a planet?

Answer 16

orbits a star

Question 17

what’s a moon ?

Answer 17

orbits a planet (sometimes called satellite)

Question 18

What’s a asteroid ?

Answer 18

relatively small rocky object orbiting a star

Question 19

what’s a comet ?

Answer 19

relatively small icy object orbiting a star

Question 20

what’s a galaxy ?

Answer 20

a group of stars clumped together (by gravity)

Question 21

what is the organization of the universe ?

Answer 21

Universe –> superclusters of galaxies –> groups of galaxies –> galaxies –> solar system –> moons

Question 22

what are superclusters of galaxies

Answer 22

thousands of galaxies held together by gravity

Question 23

what are groups of galaxies ?

Answer 23

smaller amount of galaxies

held together by gravity

Question 24

what are galaxies

Answer 24

groups of stars (~100 billion stars in each)

Question 25

solar system ?

Answer 25

planets, asteroids, comets revolving (orbiting) around one star

Question 26

moons ?

Answer 26

revolving (orbiting) around planets

Question 27

where is earth in the universe ?

Answer 27

in the local supercluster --> in the local cluster --> in the milky way --> in the solar system containing the sun as the star --> 3rd planet from the sun

Question 28

Big bang | time 0

Answer 28

Everything in the universe was confined to a single point That point then “exploded” and expanded into the universe we know today (Big Bang) Note: There was nothing before the big bang ( i.e., no space – the Big Bang created space)

Question 29

big bang | time 10^-6 s

Answer 29

Earliest matter was created in the form of Plasma (resembles both gas and liquid)

Question 30

big bang | time 10^-3 s

Answer 30

Plasma expanded and cooled forming the building blocks of matter: protons, electrons, and neutrons

Question 31

big bang | 300000 years

Answer 31

Universe cooled considerably creating hydrogen and helium (gases involved in star formation)

Question 32

big bang | 400 million years

Answer 32

First stars began to form and shine

Question 33

big bang | 800 million years

Answer 33

Gravity began to hold groups of stars together which formed galaxies

Question 34

big bang | 2 billion years

Answer 34

Half of the stars we see today were formed organizing themselves into galaxies

Question 35

big bang | 9 billion years

Answer 35

Our solar system | forms, including Earth

Question 36

big bang | 13.7 billion years

Answer 36

Present day Universe is still expanding from the initial expansion Universe contains ~ 100 billion galaxies each having ~ 100 billion stars!

Question 37

According to modern ideas and observations, what can be said about the location of the center of our expanding universe? A) Earth is at the center. B) The Sun is at the center. C) The Milky Way Galaxy is at the center. D) The universe does not have a center

Answer 37

answer: D

Question 38

If our universe is expanding, what are the implications for the separation between two stars within our galaxy? A) The two stars are moving farther apart. B) The two stars are moving closer together. C) The distance between the two stars is unaffected.

Answer 38

Answer : C

Question 39

at the scale of solar system, which length measurement do we use ?

Answer 39

AU or Astronomical unit | avg distance from earth to sun

Question 40

At the scale of Galaxies, distances are described in terms of

Answer 40

Light-years

Question 41

Speed of light ?

Answer 41

Light has a finite speed. So it takes time for light to travel great distances. The speed of light is : 300,000 km/second.

Question 42

which one is faster : Light or sound ?

Answer 42

Light

Question 43

how much time does it take light to travel from sun to earth ?

Answer 43

Therefore it takes light about 8 minutes to travel from Sun to Earth. Thus we see the Sun as it was 8 minutes ago…back in time!

Question 44

how long does it take for light to travel to the nearest star ?

Answer 44

It takes light 4 years to travel from the nearest star system, Alpha Centauri, to us. So when we see Alpha Centauri, we see it as it was 4 years ago!