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Skills of Backyard Astronomy:

3) Distance Relationships:   A Question of Scale:

The Universe is both a BIG place and a SMALL place.  Much bigger and smaller than our normal experience.  Hence our mass & distance systems are taxed to keep up, and we often will resort to using scientific notation.

An Example:

What does 6.55 x 105 mean?

This looks confusing but it isn't - it's all about powers of 10.

The exponent simply tells you how many time you multiply 10 by itself to get the real number.

105 = 10 x 10 x 10 x 10 x 10 = 100 x 10 x 10 x10 x 10 = 1000 x 10 x 10 = 10000 x 10 = 100,000

So 6.55 x 105 is actually 655,000!

This technique has its inverse.

What does 6.55 x 10-5 mean?

This time the technique is telling you to divide by 10 to get the real number.

10-5 = 1 / (10 x 10 x 10 x 10 x 10) = 0.1 / (10 x 10 x 10 x 10) = 0.01 / (10 x 10 x 10) = 0.001 / (10 x 10) = 0.0001 / (10) = 0.00001!

And 6.55 x 10-5 = 0.0000655

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