http://www.youtube.com/watch?v=OtaWkLFfevc

The Universe

Where are we?

Metric System: 1000m = 1km

Astronomical Unit (AU): Earth to sun = 1 AU (1.496 x 1011 m)

***Light Year***: Distance Light travels in ONE year! (9.46 x 1012 km)

Parsec: parallax-second (3.08 × 1016 m)

Distances of the Universe

• Measure of DISTANCE!!

• Distance light travels in one year through space

• Light travels at a speed of 3x108m/s

• If a planet is 4 light years away, it takes all light waves 4 years to get to that planet.

• If it takes light 10 years to get from one star to Earth, that star is 10 light years away.

• If satellite is put on a planet located 1 light year away, a radio signal would take 2 years to be sent, reflected, and returned to Earth.

A Light Year

A.433.8 yrs

B.433.8 days

C.433.8 hrs

Superman can fly at light speed! The planet Krypton orbits the star Polaris which is 433.8 Light years from Earth, How long would it take superman to fly home?

Everything we see in the sky is in the past! Why?

Looking into the past

Object Light travel timeMoon 1.3 secondsSun 8 min 19 secondsSirius 8.5 years (meaning what?)Andromeda Galaxy 2.3 million years

A picture of the Andromeda galaxy reveals what it looked like 2.3 million years ago. How long would we have to wait to see what the galaxy looks like right now?

A: 5 ly

B: 10 ly

C: 20 ly

D: 15 ly

A spacecraft leaves Earth for a distant planet and is traveling at the speed of light. Upon arrival, the space ship sends a radio signal back to Earth. The signal is received 10 years after the DEPARTURE of the space craft from Earth. How far away is the other planet?

Imagine that you simultaneously receive satellitetransmissions of two pictures of two aliens orbitingtwo different stars at different distances from Earth. Both aliens are celebrating their 14th birthdays in the pictures. Which of the following situations is possible at the moment you receive the pictures?

A. Both aliens are the same age but at different distances.B. The aliens are different ages but at the same distance.C. The alien closer to Earth is actually the older of the two.D. The alien farther from Earth is actually the older of the two.