Solar energy

The sun rises in the morning, bringing light and heat to another summer day. You can feel it warm your skin almost immediately yet the effect you are experiencing may have been in the works for as long as 100,000 years!

150 million kilometres away from Earth, at the centre of the Sun, energy and light are released as hydrogen atoms collide. In that nuclear reaction, particles of light, called photons, are created. 

Once a photon is released it bounces from one atom to another, like a ping pong ball, changing direction with every collision. Each step it takes may be only a tenth of a millimeter or even a centimeter before it is sent in a new direction. For tens of thousands of years the photon takes these random tiny steps until it eventually reaches the surface of the Sun, some 700,000 kilometres from the centre where it was created.

At the surface, like a dog let off its leash, the photon takes off at great speed, travelling from Sun to Earth in about eight minutes (at literally the speed of light)!

So after tens of thousands of years and millions of kilometres that photon may end its existence once it touches your skin. At that moment you may feel warmth as the photon interacts with the molecules in your skin. (Because it is simply energy that travels in waves of light particles, sunlight itself isn’t hot). 

Fast fact: Every hour enough solar energy hits this planet to satisfy all of humanity’s energy needs for a whole year.

Solar panels can convert the light of the sun into electricity using photovoltaics. The photovoltaic effect (photo meaning light, voltaic meaning electricity) turns photons into electrons. As photons strike a silicon semiconductor material they bump loose electrons from the silicon’s atoms, freeing them and creating an electric current.

A solar oven does not convert solar energy into electricity but does use photons to produce heat. Photons pass through the transparent top and strike the food or pot placed in the interior of the oven. Whatever material they strike, whether solid or liquid, will make molecules in the matter vibrate, generating heat. As that food or pot becomes warmer than the air around it, the heat tries to move to a cooler space. Trapped by the clear barrier on top of the oven, that heat reflects back on the food making the temperature rise quickly. 

Solar ovens can reach temperatures of about 200 degrees Celsius or 400 degrees Fahrenheit.

In 2020 the European Space Agency launched Solar Orbiter (SolO) to explore the sun. It will get as close as 42 million kilometres from the sun, closer than the planet Mercury, which has a surface temperature of 430 degrees Celsius, hot enough to melt lead.

rticle originally published in Brainspace Magazine Summer 2021

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