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Light in the Universe

The different properties of light makes for a very colourful universe - watch this video to find out how.
Royal Greenwich Park at sunset. Glorious pinks and oranges light up the sky. The colours in the park look very different to a bird or a bee. Bees can’t see the colour red, but they can see ultraviolet light. As it gets darker brighter stars reveal their colour, but faint objects, like nebulae and galaxies, look black and white to us. We don’t see colour in very low light. The Soyuz capsule, and soon the Starliner, will take crew to the International Space Station. Sunlight bounces off this huge, white satellite with six people on board. The Moon, the Earth’s natural satellite, reflects sunlight. And if we spread out the light, we see the visible colours from the sun.
The elements in the sun absorb specific colours, leaving behind a dark line. Each element has its own pattern called a spectrum. On a cold day, we may see the reflected spectrum of the sun around the Moon. Small ice crystals in the upper atmosphere disperse light, giving the Moon a rainbow halo. On a dark night, you may see the yellow-orange glow of Saturn from ammonia crystals in its upper atmosphere. The Space Launch System will launch crew and cargo into deep space, and astronauts travelling to Mars would see the rusty red surface due to a mineral called iron oxide in the dust and rock. Through our Great Equatorial Telescope, you could see the farthest planets, Uranus and Neptune.
Both appear blue because methane in their atmosphere absorbs the sun’s red, light leaving the blue light to pass through our telescope. But scientists think there’s an unknown molecule on Neptune which contributes to its deeper blue colour. Beyond our solar system are many stars. On a clear dark night, we can see a pale pink patch called the Orion Nebula. Thousands of baby stars are embedded in this vast region of gas and dust. The fairy tale colours in this cosmic nursery come from different gases that are tens of thousands of degrees hot. Sometimes cameras enhance the colours we see. Nearby, we find a cluster of super hot young stars, called the Pleiades, which appear blue.
The super-giant star, Betelgeuse, is 3,000 degrees cooler than the sun, thus it appears orange red. Betelgeuse is a dying star, and will soon undergo an incredibly powerful supernova explosion, leaving behind a small compact star surrounded by colourful debris, like the Crab Nebula. To bees, and most birds, with their UV sight, the Crab Nebula would look different. Astronomers use telescopes that detect colours beyond what we can see. The universe is filled with microwave light from the Big Bang. We can’t see this light with our eyes, so we use a special space telescope to detect it, and then we use false colours to map it.
A network of satellites collects information from space telescopes and beams signals back to Earth, like NASA’s Tracking and Data Relay Satellites built by Boeing. Billions of years ago, when the universe was much smaller, this Big Bang energy would have been in the visible range, and for a short time the universe would have been filled with colour. It’s a shame we weren’t around to see it.

How things appear to us depends on what happens to light before it reaches our eyes. The universe is a colourful place due to the different properties of light that are at play.

Now that you’ve reviewed some of the properties of light, see if you can identify different scenarios where they play out in the video above. We’d like you to focus on these 4 properties of light, but you might spot some others too:

  1. Dispersion – light is spread or split out.
  2. Reflection – light bounces off a surface
  3. Emission – light given out by an object
  4. Absorption – light is taken in and not reflected, or transmitted back out.

Can you find an example of these 4 properties of light in action, whilst watching the video ‘What makes the Universe Colourful?’

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Physics, Astronomy, and Space: Teaching Secondary Science

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FutureLearn - Learning For Life

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