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1

Scientific method

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

2

What is the closest star to Earth ?

the sun

3

What is the second closest star in the sky ?

Proxima Centauri

4

What is the brightest star in the sky ?

sun
star sirius is the second brightest star

5

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

24 hours

6

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

1 year (365 days)

7

Does the moon move? If so, how?

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

8

Why do we have Day and Night

The side facing the sun has daylight
The other side has darkness (night-time)

9

Astronomy is the study of...

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!

10

Astronomers measure length in

meters, astronomical units and light years

11

what is a astronomical unit

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

12

What is a lightyear

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

13

Astronomers measure time in

seconds and years

14

Astronomers measure mass in

kilograms

15

what is a star

– large burning ball of gas

16

what is a planet?

orbits a star

17

what's a moon ?

orbits a planet (sometimes called satellite)

18

What's a asteroid ?

relatively small rocky object orbiting a star

19

what's a comet ?

relatively small icy object orbiting a star

20

what's a galaxy ?

a group of stars clumped together (by gravity)

21

what is the organization of the universe ?

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

22

what are superclusters of galaxies

thousands of galaxies held together by gravity

23

what are groups of galaxies ?

smaller amount of galaxies
held together by gravity

24

what are galaxies

groups of stars (~100 billion stars in each)

25

solar system ?

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

26

moons ?

revolving (orbiting) around planets

27

where is earth in the universe ?

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

28

Big bang
time 0

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)

29

big bang
time 10^-6 s

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

30

big bang
time 10^-3 s

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