The Powers of Ten

andAstronomical units

http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html

Astronomical Unit: au, unit of distance adopted by the General Assembly of the International Astronomical Union in 2012: 1 au = 149,597,870,700 m (exactly)The Earth – Sun distance is 1 au. Parsec: unit of distance (pc) 1 pc = 3.086 x 1016 m

Parsec: corresponds to the distance at which the mean radius of the earth’s orbit subtends an angle of one second of arc.

Parsec: unit of distance (pc) 1 pc = 3.086 x 1016 m

1 pc = 3.261633 lt-yr

Light-year: A unit of DISTANCE not time. It is the distance that light travels in a year.

1 lt-yr = 9.460530 x 1015 m

1 lt-yr = 6.324 x 104 au

Consider this situation:

Seems plausible but: Nothing can travel faster than the speed of light. So is this leap correct?

Need a hint?

The Solution:

http://www.sciencelet.com/2012/10/light-year-long-rod-to-beat-speed-of-light.html

In our hypothetical example, lets say the rod is made of steel. Speed of sound in steel is 6100 m/s and the speed of light is 299792458 m/s. So the pressure wave (that travels at the speed of sound in steel) would take 49146 times more duration to reach the other end. Thus in our example, Person B would feel the nudge after nearly 49000 years. So much for their attempt to beat the speed of light.

Other interesting data:

What will we study this semester?

Main Points:1. Light1. Optics

1. Our Solar System 2. planets and their satellites 3. orbits 3. inner small and rocky 3. outer large and mainly gas 2. Asteroid belt between Mars and Jupiter 2. Comets 3. Oort Cloud 2. Meteors 2. Sun

And a focus on “How did they find that, How did they do that?”

Your address in Galactical terms:

Street:Town: Indiana 4630?USAEarthSolar SystemMilky WayLocal GroupUniverse

What about Constellations, Galaxies, Clusters of Galaxies, Dwarf Stars, Super Novas and all of that? Second Semester. But for now:

Galaxies are large collections of stars held together by their mutual gravity.

Dwarf Galaxies might have only a few million stars, many galaxies have hundreds of billions.

The Universe has around 100 billion galaxies.

Constellations hold groups of stars like the little dipper. This is called an asterism.

Constellations like Orion are patterns of stars that remain the same from night to night over the span of life-times.

Orion’s Belt

They do not appear in the same place in the night sky. Why?

The constellations visible also depends on the time of the year. Why?

What you see depends on where you are. Why?

The stars in a constellation are not flat but three dimensional. Some are farther back than others.

The stars in a constellation are not flat but three dimensional. Some are farther back than others.

How do Astronomers study what cannot be touched?1. Use the spectrum (from Radio waves to Gamma rays)

2. Bigger and Better telescopes everywhere including space. (Hubble telescope is only one example.)

BHR 71 Nebula in visiblelight.

BHR 71 Nebula in infrared light.

Taken with NASA Spitzer Space telescope/Very Large Telescope in Chile.