BPHYS 101 Astronomy

1) Our ancestors used to look up at the sky and see the same view as we do today. History shows that humans used to think that we (the earth) were the center on the universe. From earth it appears that the stars, planets, and the sun are revolving around us each day. We used to think we were located at the center because the fact that we cannot feel the constant motion as the earth rotates on its axis and orbits around the sun. This is an ancient idea called geocentric and as time passed this idea was confronted by strong evidence to rethink and evaluate how we really see earth and the universe.
Looking up at the sky on a clear night we see several stars. It is amazing that we can even see the faint dots of light. They are so small that we cannot see specific features of textures of the star. Stars are actually so far away that it takes years for their light to be seen by us. The speed of light is incredibly fast, but even light takes time to travel. When we look up at a star, we aren’t seeing a star that second, but a star from a long time ago. When we look up we are able to see all these stars and put them into shapes and patterns that we are familiar with. The shapes and patterns we put together with the stars have not changed in a long time and are called constellations. The stars and constellations lay on a celestial sphere that is an illusion that acts like a map of the sky seen from earth.
Now, looking at the sky, it would seem like the constellations and the sun would be moving differently, but according to the tutorial Motion, the main point is that the sun and stars travel together. This is shown in the tutorial where the sun and a group of constellations are shown at sunrise then eight hours later the sun and constellation is shifted together. As earth orbits the sun appears to be moving steadily eastwards along the ecliptic, with the stars of different constellation at different times of the year. The sun stays fixed and does not randomly get ahead of itself and move faster than the constellations. From the tutorial Seasonal Stars, during the course of a day there is little change in the position of the Sun with respect to the constellations. This is apparent in the tutorial when both at 6 and 12am, Scorpius would be behind the sun. But, a month later at 12am the constellation would change to Gemini (to see Scorpius you would simply look left). The sun location along the ecliptic determines which constellation we see from earth. From the tutorial Ecliptic, we can understand that the sun moves through the constellation throughout the year. This was incorporated into the celestial model by having the sun loosely fixed to the celestial sphere (slipped a small amount each day). The tutorial shows that suns position on the celestial is facing December so the constellation would be Scorpius. This tutorial shows that the side the sun is facing determines the month/constellation. Similar to the sun, the moon orbits the earth. From earth we see the moon as a big white/yellow circle in the sky when it turns into night. The moons orbit is so small compared to the distance to the sun that sunlight hits the whole thing from the same direction. The moons phases are caused because we see different portions of its day and night side at different times as it orbits around the earth. Half the moon is always bright because of the sun and the other half is dark. The rise, highest point, and set times stay the same depending on your location on earth. So for example rise would be at 6pm, the highest at midnight and set at 6am, it kinda follows a schedule like the sun does when it rises and sets. As an observer on earth, the stars, plants and the sun are truly a beautiful site to see both during the day and night. Taking a closer look we are able to see how they are able to move and function in our universe. 2) It is amazing how over thousands of years we are able to understand how the