constellations and the speed of light

constellations

88 according to astronomers

speed of light

c = 299,792,458 m/s ≈ 3*108 m/s ≈ 186,000 mi/s (around the world 7 times) ○ c is a cosmic speed limit, that is the fastest speed possible ○ light takes ≈ 8.3 minutes for light to travel from Sun to Earth ○ the star Betelgeuse, in the upper left of the Orion constellation is a red giant 500ly away that is at a stage in its life where it could go supernova at any moment ■ meaning it may have already happened as much as 500 years ago, and it won't even be possible to know it happened until the light has had 500 years to reach us ○ sometimes called a "lookback time", because everything you see took a finite, measurable amount of time for the light to reach you ○ makes the concept of "now" essentially meaningless ○ 1905 - A. Einstein couldn't find a university job, so he ended up in the back room of a Swiss patent office ○ 1905 was his "miracle year", he published 5 separate papers in the same volume of the same journal that changed science forever

precession

is like the "wobble" of a top, Earth's precession has a 26,000yr period ● Earth's precession throws off astrology calendars over the course of the thousands of years it's been around ● astrology largely exploits retrofitting and confirmation bias

cosmic speed limit

the fastest speed possible

2 postulates of special relativity

■ the laws of physics are the same in all reference frames (there is no privileged reference frame) ■ light speed is constant ○ if true, there are major implications. As the velocity of an object increases (as measured by us at rest on Earth) ■ mass increases ■ length contracts (the object would shrink, but only in the direction of motion) ■ time slows (time dilation) ○ so, as velocity approaches the speed of light... ■ mass approaches infinity

time dilation

■ we're going to build a perfect clock ■ two "perfect" mirrors placed perfectly parallel, bouncing a beam of (constant speed) light between them ■ synchronized with an identical perfect clock ■ now one is loaded on a space ship which then approaches the speed of light ■ the one on Earth will age much more than the twin on the space ship

asterism

● recognizable star patterns that aren't specific constellations (such as the "Big Dipper")

co-planar

● the "wanderer" planets are confined to a strip of sky 18º wide known as the zodiac ● ancients thought that made them special, it turns out that's just a result of the shape of the solar system