Measuring Distances in Space

Have you ever wondered how long it will take your family to drive from Lehi to Disneyland?  Or are you the person that just plugs in your head phones to your iPhone or iPod and listens to music while staring out the window and there's not a care in the world in your head? 

It's pretty easy to measure distances on Earth because there is a whole bunch of satellites circling the planet with GPS capabilities. But what about the distance to Mars, or Pluto, or the Sun?  How is that figured out?  I mean the numbers going past Pluto have got to get HUGE!

There isn't a ruler long enough to measure the distances in space, but scientists have a name for the tool they use...it's called the "cosmic distance ladder".

Scientists use different methods and MATH to find out how far things go in space.  A safe standard to use is "the speed of light".  This never changes, and nothing on Earth, natural or man made has gone faster than light. 

The speed of light is 300,000 km/sec.  Using that fact scientists take distance = velocity x the time it takes to get there.  Using this simple formula we know the distance from the Earth to the Sun, the Earth to the Moon, and all the other planets! 

The average distance of the Earth from the Sun is 93 million miles.  Scientists said, "Let's make that the base of our "cosmic ladder"... so the distance from Earth to the Sun is 1 Astronomical Unit.  The distance from the Sun to Pluto is 40 Astronomical Units.  See? That's not so bad.  Scientists can make calculations and measurements using Astronomical Units. 

Sometimes, the distances using Astronomical Units gets hard, so scientists developed the "light year".

Earth is about 8 light minutes from the Sun, where as the center of the Milky Way Galaxy is 26,000 light years away. 

Using "light years"  is much more comfortable to measure distances when we are talking about objects found in deep space.