1. The Formation of The Solar System

2. Nebulas Clouds that are a mixture of gases mainly helium, hydrogen, and dust made of elements such as carbon and iron. Very large Gravity helps a nebula to form It takes gravity and pressure for nebulas to form planets and stars The nearby explosion of a star is most likely to cause a nebula to collapse.

3. Collisions of particles produce pressure. Pressure balances in the inward gravitational pull and keeps the nebula from collapsing. Cold Hot Warm As particles move closer together, pressure increases and works in the opposite direction. Gravity causes the particles in a nebula to be attracted to one another. If the inward force of gravity is balanced by outward pressure, then the nebula becomes stable.

4. 1)The young solar nebula begins to collapse. 2)The solar nebula begins to rotate, flatten, and get warmer near its center. 3) Planetesimals begin to form within the swirling disk. 4)As the largest planetesimals grow in size, their gravity attracts more gas and dust. 5)Smaller planetesimals collide with larger ones, and planets continue to grow. 6)A star is born, blowing the remaining gas and dust out of the new solar system.

5. Planetesimals Are the building blocks of planets

6. Earth’s most unique feature is the presence of water. 3 rd planet from the sun Atmosphere 78% Nitrogen 21% Oxygen and 1% Argon (with a tiny % of other gases)

7. mantle crust core

8. 1) Impact About 4.6 billion years ago, when the Earth was separating into layers, a large object is thought to have collided with the Earth. Because the composition of the moon is similar to the composition of Earth’s mantle, scientists think that the object must have been large enough to blast part of Earth’s mantle into space. 2) Ejection Within a few hours of the impact, the debris began to revolve around the Earth. The debris consisted of mantle material from Earth and the remains of the object that struck Earth. 3)Formation Soon after the impact, the material orbiting Earth began to join together and form the moon. Much later, as the moon cooled, additional impacts created deep basins and fractured the moon’s surface. Lunar lava flowed from those cracks and flooded the basins. These lava flows are the dark patches (called maria) that we see on the moon’s surface today. Formation of the Moon

9. Earth’s had more than one Atmosphere 1 st atmosphere was probably a mixture of gases that were released as the planet cooled… a steamy mixture of carbon dioxide and water vapor. 2 nd atmosphere was probably formed from volcanic gases- chlorine, nitrogen, and sulfur in addition to large amounts of carbon dioxide and water vapor. 3 rd atmosphere it is thought that UV radiation produced the conditions necessary for live. It is thought that the first life forms were very simple and did not need oxygen to live. Today’s atmosphere Photosynthesis most likely played a major role in changing Earth’s atmosphere to become the mixture of gases we breathe today. Photosynthesis is the process of absorbing energy from the sun. Photosynthetic organisms played a major role in changing the Earth’s atmosphere into the air we breathe today.

10. Review items from Section 2 Orbit- path each planet travels around the sun. Revolution-1complete orbit Period of revolution-time it takes a planet to complete a single trip around the sun

11. Kepler’s Laws of Motion 1 st law- planets move around the sun in an elongated circle called an ellipse. Earth’s period of revolution is 365¼ days (1 yr) 2 nd law- the planets seem to move faster when they are close to the sun and slower when they are farther away 3 rd law- explains the relationship between the period of a planets’ revolution and its semimajor axis Based on the time it takes for a planet to revolve around the sun, Kepler was able to calculate the planets’ distance from the sun.

12. Newton’s Law of Universal Gravitation The force of gravity depends on the product of the masses of the two objects divided by the square of the distance between them. If two objects are moved twice as far apart, the gravitational attraction between them will be four times less. The force of gravity pulls the moon toward the Earth. Inertia explains why moving objects tend to travel in a straight line unless acted on by another force Moon’s inertia combined with the pull of Earth’s gravity causes the moon to orbit the Earth and in a curved path