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Books make many statements as though they are facts, as opposed to ideas
Many based on complex mathematical models
It's important to keep in mind that this happened a long time ago
There are no direct methods to observe the formational process of the universe
So, let's keep the uncertainty factor in mind
Study of the sky has always fascinated humans
Before electric lights and TV, its just about all there was to do at night
Look into the sky and it is obvious that there are many objects out there
In our immediate vicinity describe solar system
In the distance
Countless stars, clusters, and galaxies (show poster of M-31)
Milky Way: our galaxy (with >10 billion stars)
Our sun is an 'average' star
Rather insignificant
Way out on a spiral arm - like Luke Skywalker's home planet
The "known" universe is truly immense
Estimate billions of galaxies in universe
Widely spaced islands of stars in the vast void of space
How about other planets?
3 X 1010 galaxies
1X 1011 stars per galaxy
1 X 101 planets per star
...equals a lot of stuff (3 X 1022 planets possible)
Distances measured in Light Years: Light speed (186,000 miles per second)
We look back in time as we look out into the universe
See it 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 . . . . . . . . . . . . 2,360,000And 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!
This is where some of the heavy-duty laws of nature come into effect
Sir Isaac Newton (1642-1727)
Newton's "Universal" Law of Gravitation: G=M1M2/D2
Three Laws of Motion
1st Law: Inertia
"A body continues in its state of rest, or of uniform motion in a straight line, unless it is acted upon by a net external force"
2nd Law: Force = mass X acceleration
"When an unbalanced force acts on a body, the body will be accelerated"
3rd Law: Law of action and reaction
"For every action there is an equal and opposite reaction"
A single force cannot exist. Every force is accompanied by an equal and opposite force
These work well for most of what we have to deal with
Start to break down when we get too big or small, or try to go too fast
Albert Einstein: early 1900's
Matter and energy are interchangeable (E=MC2)
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There are two possibilities
1) Everything always existed like it is today, and time has no beginning, or
2) The universe (and time) began at a specific moment, and has been evolving and changing ever since
Observations indicate that everything is moving away from everything else
Rapid expansion of all matter: Implies a common center for all matter
"The entire universe was compressed into a single infinitely dense point"
This point exploded 15 to 18 billion years ago
The Big Bang
Marks the beginning of the universe and the start of time
"no ordinary explosion"
"This explosion instantly created the universe. Matter, energy, space and even time came into existence with this single event."
One of two possibilities
1) Open Universe
The galaxies will continue to expand "forever"
All stars will eventually use up their fuel and burn out
Universe will then be cold and dead, forever
2) Closed Universe
The expansion will slow until the overall gravitation attraction of the matter will cause the universe to collapse (The Big Crunch)
This could lead to a new Big Bang, and new universe
Were there others in the past?
How long has this been going on, and how could we ever find out
Theoretical stuff like this is a lot like geology
Impossible to prove or disprove, so we are free to speculate all we want
Formed by the condensation of a "nebula"
Slowly rotating in space, and very cold (-270°C)
Gravitation attraction caused this matter to condense
Condensation resulted in faster rotation
The Law of Conservation of Angular Momentum
Most of the matter accumulated into the center
At some point the amount of matter was sufficient to set off nuclear reactions which cause stars to give off energy
Critical mass
At the same time, the planets were forming
The rotational velocity of the nebula increased as it condensed
Caused the nebula to flatten and extend into a disk-shaped form
The planets being formed within the relatively narrow disk arms
Aggregates of material coalesced into larger bodies
Changed from a large number of small pieces to a small number of large chunks
How long did it take for the planets to accumulate
The initial condensation may have happened quickly
But, it's still going on!
Meteorite impacts indicate continued accumulation
How large of pieces can we expect to impact the earth?