ASTRONOMY 210 a survey of astronomy Office Hours: Paul Coleman: MWF (10:30-11:30;12:30-13:30) Watanabe 423 pcoleman@ifa.hawaii.edu Grad St. Course details and notes: http://www.ifa.hawaii.edu/users/gruff/default/Coleman.html http://www.ifa.hawaii.edu/users/gruff/default/Astro 210/astro210.html

Cellphones on vibrate!! and phasers on stun!

Weekly quizzes…. If you will miss it contact me in advance… Makeups will be held on the Monday following One question on the weekly homework problem One question on the material in the readings

Spaceship Earth Describe the basic motions of “spaceship Earth.” How do we know that the Universe is expanding?

and Shakers… Movers… “We never get to go anywhere” “It costs too much to go anywhere” Nothing could be further from the truth… During this one hour lecture, all of us will have traveled some 48,600 miles through space as our planet sails around the sun at 18 miles per second! During the half-minute we’ve been looking at this slide, we have traveled ~400 miles. We are whizzing through space in at least four different directions! Why don’t we feel the motion?

Motion I Face the rising sun in the morning. That's our first direction of celestial movement. Let's begin our fantastic cosmic voyage and see what is really going on. We are going to investigate four directions that we are moving, all at the same time.

r Circumference = 2pr

Motion I 1042 mph !!!! Circumference = 2pr ~ 25000 miles Time = 24 hours 1042 mph !!!!

Motion II r = 1 AU = 1.5 x 1011 meters

Motion II We are zooming around the sun at 64,800 mph!!!

West N

r 226 million years to make one revolution around the Milky Way. The last time we were here, dinosaurs ruled the earth. Our orbital speed around the galaxy is an astonishing 135 miles per second Our Sun is but one of some 100 billion stars that makes up our home galaxy, the Milky Way. It takes our sun about 226 million years to circle the Milky Way. Motion III

Motion III With the measured distance to the Galactic Center we calculate a speed of about 486,000 mph. Look a little above the horizon about 20 degrees west of directly south – you are traveling in that direction! The center of the Galaxy is located between the two constellations Scorpius and Sagittarius. 90 degrees away from this direction (toward Dorado) is the direction we are going as we orbit the galaxy at 135 miles per second.

Motion IV Look South around midnight in june, you'll see the beautiful Southern Cross low on the horizon. Right above it is the constellation Centaurus. That's the direction our solar system and galaxy is headed at more than a million miles per hour!

Take your pick: Earth’s rotational speed = 1042 mph Earth’s orbital speed = 64,800 mph Sun’s orbital speed = 486,000 mph Milky Way’s speed = 1,000,000 mph (Not to mention the expansion of the universe!) In the ~20 minutes so far for this talk, we have moved about 350 miles east and about 21,600 miles around the sun. Our solar system has moved 162,000 miles around the galaxy and we've moved about 340,000 miles closer to Hercules. For a grand total of about 420,000 miles traveled! Too bad we don't get frequent flyer miles for this.

How large is the Solar System? Let’s view it to scale say the Sun is the size of a CD (~12 cm) then: Earth – 15 m Mars – 23 m Jupiter – 78 m Saturn –143 m Uranus – 287 m

Math and Physics (so far) geometry speed / velocity Ratios:

Vector sums: