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!
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!
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!
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?
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"
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!