Solar Projection
Solar projection is a way to view the sun by letting light pass through a small hole onto a screen.
A colander sits over a white tray. Sunlight shines through one small hole and makes a bright circle on the tray below. The hole lets only a thin beam pass through, so the light forms a clear spot. Move the tray farther away and the circle grows larger but stays safe to look at.
Explaining solar projection by grade level
A tiny hole in a card lets sunlight through. The light makes a round spot on the ground. That spot is a small picture of the sun. You can see dark marks on it too.
Projects that explore solar projection
When sunlight passes through a tiny pinhole, it forms a real image of the sun on a surface beyond. To measure the sun's actual diameter, you tape aluminum foil with a pinhole to one cardboard box and a card with two parallel lines 8 mm apart to the other. Both boxes slide onto a meter stick. Aim the pinhole at the sun and a bright image appears on the far card. Slide the second card until the image fills the gap between the lines. That distance, combined with a simple ratio, gives you the sun's diameter — which you then compare to the accepted value of 1,391,000 km.
Sunlight passing through a small opening projects a sharp image of the sun onto a nearby surface. Aim a telescope at the sun and hold white paper near the eyepiece — the sun's disk appears on the paper. Adjust the focus until the image is sharp, and dark spots become visible on the projected disk. These are sunspots, cooler patches on the sun's surface that show up as small dark specks. No telescope? Poke a small hole in a shoebox with a pin and aim it at the sun. The sun's image projects onto the inside of the box, revealing the same details without ever looking directly at it.