A central problem of astronomy from the very beginning has been how to measure astronomical distances.

The Copernican system provides a straightforward geometric means to measure planetary distances in terms of the size of the Earth's orbit, or in units of Astronomical Units (AU).

Nothing could be simpler, except for one, minor detail...

Just how big is an AU, anyway?

Anyone..... 

piece a cake, about 149millions kilometers

It can be 1 Astronomical unit(1 AU) Earth to Sun(149,598,000 kilometers).But,the right distance is 1 miles(160.000.000 kilometers)