Let's hear it for the sun. Yes, the sun -- that great glowing orb that moves across the sky every day, lighting up our world. And providing so many things necessary for life, everything from making forests and gardens grow to manufacturing vitamin D in our skin. Just into the new year, as days start getting longer here in the Northern Hemisphere, it seems a good time to pause and appreciate the great big star we rotate around.

The sun isn't the largest star in our part of the Milky Way galaxy, but it's in the top five per cent, mostly because so many other stars are red dwarfs and relatively small. Like stars we see in the night sky, the sun is composed mainly of hydrogen and helium. Deep in its core, at unimaginably high temperatures, nuclear fusion is going on: four hydrogen atoms combining into one helium atom, with a tiny loss of mass that results in a huge release of energy. As Einstein discovered, energy equals mass times the speed of light squared.

Over millions of years, all that energy slowly makes its way to the surface of the huge gaseous ball that is the sun, each gamma ray in the core being converted into several million photons of visible light that are finally released into space. Other forms of radiation also escape in the solar winds that continually sweep outward from the sun's broiling surface.

Because earth is on average 150 million km away and light travels at about 300,000 km per second, it takes approximately 8 minutes 20 seconds for those photons to reach us and start doing their magic.

Earth is just far enough from the sun that water can remain liquid here much of the time, instead of frozen solid or boiled away. That fact makes life on earth possible. Water is such a versatile, adaptable, miraculous substance, and we humans are 60 per cent water.

Energy from sunlight supports almost all life here via photosynthesis. The food chain depends on vegetation absorbing light and making it usable. Our oil, natural gas and coal reserves all result from photosynthesis in ages past.

The sun not only warms and nourishes us, it creates great beauty: glorious sunrises and sunsets, rainbows, coloured sparkles on snow crystals in winter. The haunting northern lights are caused by ionized solar particles hitting our upper atmosphere and causing atoms there to glow. Earth's geomagnetic field usually deflects these ions to the poles.

Sunlight scattered through the atmosphere makes the sky appear blue, and the sun, which is white, a warm yellow. Sunlight glinting on the feathers of a hummingbird turns them into jewels, and refracted in those of a bluebird creates the most beautiful hue in the world.

Nature queries: 905-725-2116 or mcarney@interlinks.net.