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Seeing the invisible

Find out how to explain things we can't see.
Do you ever wish you had superpowers? Maybe you would like to be able to fly or have X-ray vision. Here at the Royal Observatory Greenwich, we would love to be able to see the invisible. And we can– well, sort of. It’s impossible for the human eye to see everything that is going on in the universe. Take this fridge magnet. How does it stay in the fridge? Glue? Tape? No, it’s magnetism– an invisible force of attraction or repulsion that acts at a distance. Magnetic materials are found in all sorts of places on earth and even in space. Some asteroids and meteoroids contain iron and can be magnetic. Space can be a dangerous place.
Our sun is shining bright, but it’s very important to never look directly at it. And its brightness is not the only thing that makes it dangerous. Occasionally, the sun ejects large amounts of material into space. This solar wind can also be very harmful for us. Luckily, our planet has an atmosphere and its very own invisible magnetic force field, which keeps us safe. But how do we know that really exists if we can’t see it? Well, the solar wind high energy particles get caught up in the Earth’s field lines, which meet up at the north and south poles. There, they sneak into our atmosphere revealing its invisible elements. Nitrogen, oxygen, and argon are the main ones.
The light particles excite some of the atoms, giving them energy. Atoms don’t like to be exited. They get rid of the extra energy as colourful light– green, red, or even violet. These beautiful light displays are called “aurorae.”
So even though we might not really have superpowers, being able to see the invisible sometimes makes us feel just a little like we do.

If you can’t actually observe an astronomical phenomenon it is very difficult to explain it.

Here you will find a video we have created that brings together many science concepts that can’t be observed and looks at how we can begin to explain them.

Here is a list of useful scientific phenomena linked to space and physics covered in the video:

  • Meteorites are rocks that fall to Earth from space. They come from the asteroid belt and some of them contain iron which makes them magnetic.
  • The Sun is an active ball of gas – mainly hydrogen and helium. Over one million Earths could fit inside the Sun.
  • The Sun ejects a stream of high energy particles called the solar wind. These particles can move at speeds reaching 750 kilometres per second!
  • The solar wind interacts with the Earth’s invisible magnetic field. The magnetic field lines channel these particles towards the north and south poles, a bit like a bicycle getting caught in tram lines on the road and following the track.
  • The air is made of a number of different gases such as nitrogen (78%) and oxygen (21%).
  • These gases are usually invisible to us, however the solar wind particles collide with these gases, give them energy and in response they glow.
  • These curtains of green, pink and red light are called aurorae, or the northern and southern lights.
  • Some other planets such as Saturn and Jupiter have aurorae over their poles
  • Aurorae also emit ultraviolet light which is invisible to our eyes. Astronomers use special telescopes that can detect this type of light.

If you would like to follow this up with extra activities take a look at the classroom resource How do we see things?

This article is from the free online

Our Solar System and Beyond: Teaching Primary Science

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FutureLearn - Learning For Life

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