Here’s a fascinating web page that lets you zoom in and out with a slider at the bottom to see objects on different scales, starting with the size of a human being and zooming out to see the size of the observable universe or in to see the size of the smallest concepts in physics. Definitely worth a visit!
Note that you can click on objects to see a bit of information about them. Included are the planets and many lesser objects in the Solar System, nebulae and star clusters, galaxies of various sizes, living things from blue whales to bacteria, subatomic particles and such things as the range of the weak force, and so on.
Did you know that that the Great Wall of China stretches farther than the diameter of Pluto?
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Check out a similar site using real pictures: http://cosmicscale.appspot.com/