2. To us, our Solar System seems HUGE In the vastness (enormousness) of space, its actually very small The Universe contains everything, and within the Universe are billions of galaxies (the USA doesn’t even have 1 billion people) Each galaxy is home to billions of stars Some of those stars have solar systems

3. Universe Billions of Galaxies Milky Way (1 of billions) Our Solar System (1 star out of millions)

4. Our Solar System is just one small part of our galaxy. The most common thing in our galaxy is empty space. We are 4.2 light years from the nearest star All objects in the Universe are spread out over extremely long distances

5. Kilometers are too small to measure distances in space. It would be like measuring the distance to Panama City in inches. Inside of our Solar System, we use Astronomical Units to measure distance

6. Astronomical Units: AU. The distance from the Earth to the Sun.

7. Outside of our Solar System, we measure distances in light years: the distance light travels in a vacuum in one year. Light-second: 299,792,458 meters light would make a round trip from London to New York almost 27,000 times in a single second. In one light year, this trip could happen 850 BILLION times

8. The absolute closest thing to us in the whole Universe is Alpha Centauri, a star in our OWN galaxy, the Milky Way. It is 4.2 light years away. For light, that’s 3570 BILLION round trips between New York and London

9. Gravity The force that causes all matter to move toward other matter. The greater the mass, the greater the gravitational pull. The closer the object, the greater the gravitational pull

10. There was a nebula: a big collection of dust and gas that gives birth to stars.

11. This nebula had areas where there was more dust and gas and areas where there was less. Which area had a greater gravitational pull? The area with the greater mass (more dust and gas)

12. Over time, the dust and gas began to rotate around the area of greater mass, pulling tighter and tighter until it formed the sphere that would be our Sun. 99% of the matter in the nebula formed the beginning of the Sun. The rest rotated around the center This is called a proto –planetary disc

13. The remaining matter revolved around the Sun and began to accumulate in areas of greater mass, just like it did with the Sun. Spheres called planetesimals, baby planets, formed in these areas.

14. The planets migrated to their current positions with extra dust and gas either being pushed away by solar winds or forming other objects in the Solar System. What caused it all? GRAVITY!

16. The Geocentric Model A super complex model of the Solar System used to show the Earth at the center of all the known Universe The stars, planets, and the Sun revolved around Earth

17. Helio= of or relating to the Sun Centric= centered Heliocentric? Sun at the center.

18. Copernicus Theorized the Helio-centric model of the Solar System Made sense mathematically Fit with all observations Kepler: helped develop model Galileo Galilee: made supporting observations Was forced into house arrest by the Vatican for heresy and treason because the Heliocentric model went against the teachings of the Bible The pope pardoned Galileo in 1992, everyone agrees that the Sun is the center of the Solar System now

19. Widely accepted today Sun at the center, planets orbit around it All available evidence supports this model