A parabolic curve reflects light toward a single focal point, concentrating the sun's energy in one spot. When you line that curve with aluminum foil and aim it at the sky, the bright spot at the focal point gets hot enough to cook food. Place a skewer through that focal point and the heat moves from the concentrated sunlight directly into a hot dog — no stove required.

Shiny surfaces reflect light rather than absorbing it, and that property makes them useful for directing sunlight. A parabolic curve lined with aluminum foil, shiny side out, bounces light toward a single focal point. All that reflected light concentrates at one spot instead of being soaked up by the surface.

A parabolic curve sends all its reflected light to one spot. You can find that spot by attaching posterboard to the opening and looking for the bright area where the light concentrates. Place a skewer through that spot and the sun's focused energy is enough to cook a hot dog.

A parabolic curve lined with aluminum foil, shiny side out, reflects light toward a single focal point. You can find that spot by attaching posterboard to the opening and looking for the bright area where the light concentrates. Place a skewer through that spot and the sun's focused energy is enough to cook a hot dog.

Concentrated solar power works by reflecting light toward a single point called the focal point. A parabolic shape lined with foil directs sunlight to that spot. You can test the focal point with sunlight and see a bright spot where the light concentrates.

A parabolic curve lined with aluminum foil reflects light toward a single point called the focal point. All that concentrated sunlight speeds up the tiny particles at that spot, building up heat quickly. The sun's energy focused there makes the particles move fast enough to cook a hot dog placed on a skewer at that point.