1

IntroductionIntroduction

Lecture 1

2

What is Science?What is Science?

Science is a way of viewing the world based on the guiding principles: Nature is lawful Some of this lawful behavior is universal

The goal of science is to uncover the laws of Nature and use them to satisfy our species profound need to understand what we see around us.

Science also provides the basis of technology

3

Cosmological PrincipleCosmological Principle

There is nothing special about our place in the universe

If this principle is true, then what we learn from studying our neighborhood of the universe will apply to the universe as a whole.

The principle is also known as the Copernican Principle

4

Scientific MethodScientific Method

Based on testing and experimentation Make a model (hypothesis) Test the model

• Observations• Experiments

Modify the model (if necessary) Retest

• Improved techniques: better observations• Better experiments

Based on evidence, not faith. Discard false ideas, however pleasing they may be

5

DistancesDistances

6

Distance UnitsDistance Units

Meters (m) and Kilometers (km) Good for everyday distances

Astronomical Unit (AU) Average distance between the Sun and Earth 150 million kilometer

Lightyear (LY) Distance light travels in 1 year Light travels at 3 x 108 m/s in a vacuum

• About 7 times around the Earth in a second So in a year, how far does light travel?

7

Really Big NumbersReally Big Numbers

Really big numbers are hard to understand… Examples:

• 10,000,000,000, 10,000,000,000,000,000?

We will often use powers of 10 for large• 1,000,000 = 10x10x10x10x10x10 = 106

Each factor of 10 is called one order of magnitude

8

Really Small NumbersReally Small Numbers

Really small numbers are hard to understand also…! Examples:

• 0.00000000000001, 0.0000000000000000000001 Easier to use negative powers of 10

• A million billionth is 10-15

9

LightyearLightyear

There are about 3 x 107 seconds in a year 60 s/min x 60 min/hr x 24 hr/day x 365 days/year ~

3.15 x 107 s/yr

Light travels at 3 x 108 m/s (300 million km/s) So,

3 x 108 m/s x 3 x 107 s= 9 x 1015 m = 9 x 1012 km

10

Whoever can no longer wonder, no longer marvel, is as good as dead…

Albert Einstein

11

12

13

Jupiter and IoJupiter and Io

14

The Eagle NebulaThe Eagle Nebula

15

The Red GiantThe Red Giant

16

AndromedaAndromeda

17

M87M87

Distance: 50 Mly

Length of jets: 5000 ly

Mass ofBlack hole: 3 billion Msun

18

SummarySummary

Astronomy is a science

During this semester you will learn about a wide range of objects such as Planets, the Sun, Neutron Stars, Super-giant Stars,

Supernovas, Black holes, Galaxies etc.

This class should be one of the most interesting courses you take at FSU

See you next time!