Introduction to Reality


Name of the discussion, but what is reality and what is perception

"Howard the Duck" - 5:50 clip at start of film

This isn't designed to be an easy class

Astronomy is an extremely complex topic

Books make many statements as though they are facts, as opposed to theories

Much based on complex mathematical models

It's important to keep in mind that the processes discussed happened...

A long time ago

A long way from us

At a scale we can't comprehend

Or all three!

What we think we know represents theories based on current levels of understanding

Or, what we think we understand

There are no direct methods to observe the formational process of the universe

All methods are essentially indirect and involve some major assumptions

So, let's keep the uncertainty factor in mind while we discuss this topic

This does not mean that we should blow it off

Only that we should keep an open mind and not get cocky

I'd like to start with a brief overview of the universe

Some of this will be covered in more detail later, but not all

Too much material for 10 to 12 weeks!


Study of the sky has always fascinated humans

It's easy to do

Before electric lights and TV, its (almost) all there was to do at night

Not going to spend much of time on the history of astronomy

We get hung up on European history at the expense of the rest of the world

It is clear that many non-European cultures were highly advanced

Stonehenge, Mayas, Incas, Chinese, etc.

Europe during the Middle Ages was about as far behind as one could imagine

Don't want to get into a "science vs. the church" argument

Clear that scientific exploration was discouraged during the middle ages

Galileo had to choose between his work and the stake!


Look into the sky and it is obvious that there are lots of things out there

In our immediate vicinity: Sun, 9 planets, and asteroid belt

In the distance: Countless stars, and clusters

We're part of a large group called the Milky Way (fig. P.7 pp. 5 +) (poster)

Called a galaxy

Ours is of the spiral variety (DESCRIBE) (show poster)

Our sun is an 'average' star: Rather insignificant (fig. P.7, p.5) (overhead)

Way out on a spiral arm - like Luke Skywalker's home planet

Look out along plane of the galaxy: the Milky Way

A minimum of 1011 stars (100,000,000,000)

106 light years across (DEFINE: Light year)

And this is not all (show National Geographic poster)

The "known" universe is truly immense

At least 3 X 1010 galaxies within view of earth with current technology

Islands of stars in the vast void of space

As our instruments get more powerful, we can see farther

And it's still going (like the Energizer Bunny)

As we look out into space we also look back in time

Light speed (3 X 108 meters per second)

We see the universe as it was, not as it is

Even the sun is 8 minutes old news!

And everything is changing position

How fast are you moving?

All speed approximate and in miles per hour (J. Michener: Space, pg. 585)

Rotation of Earth . . . . . . . . . 800
Revolution around sun . . . . . .66,661
Sun moving towards Vega . . . . .31,000
Local group of stars moving . . 700,000
Rotation of Galaxy. . . . . . . 560,000
Movement of Galaxy. . . . . . 1,000,000
Total . . . . . . . . . . . . 2,360,000

And there are surely additional motions to take into account at larger-than-galactic scales!

This can really foul up our perceptions of space, time, and reality!


Do other suns have planets around them?

Nearly impossible to directly observe other planetary systems

Hubble Space Telescope is beginning to supply some convincing photographic evidence of planets associated with several near-by stars

However, indirect evidence exists

Planets are dark bodies - don't emit visible energy

Do have mass and therefore a gravitational effect of their suns

Whoa! What's a Gravitational Effect

Drop book: Did the book fall down or pull the earth up?

Early workers were not sure: Let's take a vote

Newton's "Universal" Law of Gravitation: G=M1M2/D2

Affect (perturb) the motion of the star (which we can measure)

If: all the galaxies are like ours, and all the stars have 10 planets

3 X 1010 galaxies X 1011 stars/galaxy X 101 planets/star = 3 X 1022 planets possible in known universe

Think any of these might have life?


Formation of the Universe

There are two possibilities

1) Everything always existed like it is today, and time has no beginning

2) The universe (and time) began at a specific moment, and has been evolving and changing ever since

Observation indicate that everything is moving away from everything else

Rapid expansion of all matter

Implies that all matter must have started at a common center

Interpretation: "the entire universe was compressed into a single infinitely dense point"

This is where I start to have trouble - no one was there, and we're talking about things which we probably aren't sufficiently advanced to understand

Not saying they're wrong, just skeptical enough to keep an open mind

Anyway, according to the theory, this point exploded

The Big Bang

Marks the beginning of the universe and the start of time

"no ordinary explosion"

More on this later


Formation of the Solar System

The Nebular Hypothesis

Formed by the condensation of a "nebula"

A nebula is a widely dispersed cloud of interstellar gas and dust

Slowly rotating in space

Very cold (-270°C)

Gravitation attraction caused this matter to condense

Condensation resulted in faster rotation

The Law of Conservation of Angular Momentum

Ex. - a spinning ice skater

And an increase in temperature

Most matter accumulated into the center to form the sun

At the same time, the planets were forming

The concentration of the planets along the plane of the ecliptic indicates a similar origin for the entire solar system

Both in a time sense as well as the method of formation

Lots more on this later!