Make a pinhole camera by putting a pinhole in your piece of cardboard. Hold a piece of paper one meter away from the cardboard. Your pin-hole camera will cast an image of the sun on your paper. Measure the diameter of the image cast on your paper. The ratio of the sun's actual diameter to its distance from the earth is the same as the ratio of the diameter of the sun's image to the distance between the cardboard and the image. In other words, the diameter of the sun (X) divided by the distance from the earth to the sun is equal to the diameter of your image divided by the distance from the pinhole to the image. Good luck.
Clouds and the atmosphere.
Beyond the UniverseThat's the question that mankind has been trying to resolve for centuries and that's why they go to the moon and are trying to discover what is on other planets. They call space "the last frontier", but that's simply not true. The ocean has vast secrets to give up yet. There are many things still on this earth or out in space we haven't even conceived yet. Just because we haven't seen it doesn't mean it isn't so. We don't know if there is water on other planets, plant life, etc. Space to humans is a void ... no beginning, no end.
New TheoryThere is a new theory that our universe is one of billions in membrane-like structures. Each time these membranes collide it creates energy and an explosion like the big bang. If that's true there could be billions of other universes with planets in them just like ours.
Note:It's important to note that the "multi-verse" of Membrane Theory does not refer to universes that we could visit by spaceship, no matter how fast or powerful they become. The idea is that these universes are right "here", all over the place, and could be accessed, if at all, by somehow accessing the multi-dimensional world that generates them, or maybe by accessing worm holes.
A Child's Point of View:
From my point of view, as a 12 year old in the seventh grade, I really like astronomy but there are so many things I don't know about it. I really want to go up into space someday and find out all of these unknown secrets. I want to be the hero on the magazines, being payed and content. But I know there is no chance of that happening. I really do want this though. You know, sometimes they say "Adults don't know some things that kids do know" and i'd like to prove that. They say were just a kid. They say we don't do much, but their wrong.
The sun is a very close approximation of an ideal blackbody (it's been called a "real" blackbody), since its actual solar radiation/emission curve is very similar to that of an ideal blackbody emission curve. Ie, with fluctuation, it very nearly absorbs and emits all radiative energy received.