Today’s Wonder of the Day was inspired by melia from fayetteville, NC. melia Wonders, “How does the sun make energy?” Thanks for WONDERing with us, melia!

Imagine life on Earth without the Sun! It might be fun for a little while. You could play an awesome game of flashlight tag with your friends and then tell spooky stories around a fire.

But it wouldn’t be fun for long. Soon, you’d need to keep a fire going all the time. Without the Sun’s heat, Earth would become very cold, and plants who require sunlight for photosynthesis wouldn’t grow. This would make it hard to find food.

The Sun’s energy also powers Earth’s weather and water cycle. If we didn’t have these processes, life on Earth wouldn’t last very long. Scientists know that the Sun is essential to life on Earth, but how does it produce all that energy that we use in many different ways? To find out, we need to get to the heart of the matter and travel all the way to the Sun’s core.

Unlike Earth, which is made from mostly iron, rock, water, and many other elements, the Sun is made up mostly of hydrogen gas. Its core is incredibly hot, like Earth’s, and under a lot of pressure.

This pressure causes hydrogen atoms to fuse together, creating a nuclear reaction called fusion. This reaction produces a lot of energy that helps power our solar system.

The Sun’s fusion reaction is similar to a hydrogen bomb, but much more powerful. The Sun doesn’t explode because the outward pressure from the fusion reaction is balanced by the inward pressure of the gases that surround the core.

Earth only gets a tiny fraction of the energy the Sun makes, but it’s enough to power our planet. Some of the energy is reflected back into space, while a little over 40% warms the Earth. About 25% is used by the water cycle. Winds, and ocean currents take about 1%. Plants use a tiny amount of the Sun’s energy for photosynthesis—about 0.023%!

What are your favorite things about the Sun? Do you like to play outside when the Sun is shining? Do you plant a garden and eat yummy vegetables that grow because of the Sun? How would you say “thank you” to the Sun for everything it does?

Wonder What's Next?

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