Unit 1 Lesson 1

1. All matter in the universe began moving together to a single point.
2. At that time the universe was small, hot and dense.
3. 10-15 billion years ago there was an enormous explosion that sent all matter moving outward.
4. Since then all matter in the universe has continued expanding outward.

Evidence for the Big Bang
Red Shift/Blue shift
• Redshift and blueshift describe how light changes as objects in space (such as stars or galaxies) move closer or farther away from us.
The concept is key to charting the universe's expansion.

Visible light is a spectrum of colors, which is clear to anyone who has looked at a rainbow.
When an object moves away from us, the light is shifted to the red end of the spectrum, as its wavelengths get longer. If an object moves closer, the light moves to the blue end of the spectrum, as its wavelengths get shorter.

Everyone has heard the increased pitch of an approaching train and the sharp decrease in pitch as the train passes by and recedes. The effect arises because the sound waves arrive at the listener's ear closer together as the source approaches, and further apart as it recedes.

This sound effect was first described by Christian
Andreas Doppler and is called the Doppler
effect. Since light also travels in wavelengths, this means that the wavelengths can stretch or crunch together depending on the relative position of objects.

In the universe scientists have found that the galaxies are moving away (redshift) from a central point (where the explosion originated).
The universe is still expanding.

The Universe - All space, energy and matter
• What is in the Universe?
1. Earth
* Water in all 3 states
* If no water, no evaporation, no clouds, no oxygen, no plants, no animals, no humans
* Has the right combination of gases in the atmosphere that animals need to breathe.
* Has ozone that absorbs harmful radiation.

2. Solar systems
* A collection of large and small bodies that orbit a central star.
* Our solar system has one star, the sun and 8 planets.
* Planet – spherical body that orbits a star
*Terrestrial planets – rocky, dense and relatively small bodies
* Mercury, Venus, Earth, Mars
*Gas giant planets – large planets with thick , gaseous atmospheres
*Jupiter, Saturn, Neptune, Uranus
* Natural satellites (moons) – smaller bodies that orbit planets
* Smaller objects – meteoroids, comets, asteroids

3. Stars
* Star - is a large celestial body that is composed of gas and emits light
*Most stars are mainly composed of hydrogen and helium.
*Nuclear fusion – stars fuse lighter elements into heavier elements (ex.
Hydrogen into helium)
*Fusion takes place in the center of the star and energy leaves the core and moves outward giving of radiation

3. Galaxies
* Galaxy is a large collection of stars, gas and dust held together by gravity
* Dwarf galaxies – small galaxies containing 100 million stars
*Giant galaxies – contain hundreds of billions of stars
*3 types of galaxies
*Spiral – our galaxy the Milky Way
*Elliptical galaxy
*Irregular galaxy

How are distances in the universe measured?
• Light-year – the distance that light travels in one year going at the speed of light
• Speed of light – 300,000 km/second
• Speed of light – 186, 000 miles/second
• 9.5 trillion km in one year
• Closest star (other that sun) is Proxima Centauri is 4.3 light years away
• It would take 4.3 year to get there traveling at the speed of light.
• Sun is 8 light-minutes from Earth
• Fastest inter-planetary spacecraft moves
58,000km/hour
• At that speed it would take 75,000 years to reach nearest star

What is the structure of the Universe?
*Clusters or Superclusters – areas of densely concentrated galaxies
• Voids – large areas where very little matter exists
* Between galaxies are huge voids. Most of the universe is made of voids.