Post on 13-Dec-2015
Measuring the Very Large
For distance that is. The Kilometer
What exactly *is* a kilometer? 1000 meters We walk at about 5 km/hr, or 0.0015 km/s
The Moon (closest object), is 400,000 km away How long to walk there?
Lunar
The distance to the *nearest* planet, Venus 38,000,000 km ▪ (at its closest, but it can be up to 228,000,000 km
away) How long to walk that?
From the earth to the sun is 150,000,000 km This is used as a new unit of distance The Astronomical Unit (A.U.)
Solar
In the solar system: Jupiter is 4 A.U. from us Neptune, 30 A.U. Pluto, 50 A.U. Edge of the solar system, 100,000 A.U. Nearest Star (Alpha Centauri), 268,000 A.U.
Clearly, the A.U. quickly loses its usefulness.
oort
Light travels faster than anything else in the universe. 300,000 km/s (186,000 mi/s, or 670,000,000
mi/hr)
In one year, light will travel 10 trillion km
This is called the LIGHT YEAR (ly)
It is the BASIC unit of distance for astronomy
Loca
l Sta
rs
Nearest Star 4.2 light years
Thickness of the milky way galaxy 1,000 ly
To the center of our galaxy 25,000 ly
Diameter of our galaxy 120,000 ly
Distance to the nearest major galaxy (Andromeda) 2,000,000 ly
• Ultra