AstroTalk: What the Photon?

Hello everyone!

By far, the most requested posts are to write more about stars, making this post long overdue. My dilemma however, was to to be able to write at the correct level. My experience as a reader of many things celestial shows that it is all too easy to spout jargon or act like you are talking to a 3 year old,but very hard to do anything in between. And this is exactly what the aim of AstroTalk is (thus making your feedback even more valuable!). Moving on.

One of the most important things that is needed for astronomers to function is light. It however, recently struck me how much we take it for granted.

Friend: Oh you know I saw this thing…

Me: Well you know, you didn’t actually see it.

Friend: What on earth are you on about?

Me: You are not seeing the actual object, your eyes are detecting the light that bounces off said object.

Friend: You’re impossible you are.

To quote my friend, what on earth am I on about?

Our eyes are actually like cameras, that detect “photons” which are essentially small bits of light. When you switch on a lamp or stand under sunlight, it acts as a source of photons, creating bits of light that bounce off other objects in the room, enabling you to see them. At night or when you switch the lamp off, there are no photons to bounce off things and you cannot see them. Thus making it dark. This is also why we are able to see the moon. Because it reflects light off the Sun.

While this may be rather obvious uses of light, there are some not so obvious ones too. I am using the word “light” to describe stuff we use to see, but actually it is just a small part of something much bigger.

For example, what if I were to say Radio is also technically light?

Random person: Hang on? Radio like I listen to when I am in the car?? Surely that’s sound!!

The answer lies in this often used, and extremely helpful diagram.

Source: The Electromagnetic Spectrum

Source: The Electromagnetic Spectrum

In the figure above, you can spot the familiar colours of the rainbow. But what about the stretches of black to either side? That my friends, is also light, but light that we cannot see. You see (Haha get what I did there?) light carries information. When you “see” an object, your brain is interpreting the information that the light reflected off the object is bringing you. At the same time, light that you cannot see is bringing you information that you cannot understand. Confusing I know.

What does this have to do with radio? Everything. Radio waves are also a type of light that is used to carry information. Radio towers transmit these radio waves that are picked up by that box in your car that you call a radio. This magic box then converts the light that is radio waves into sound: thus enabling you to listen to Mozart, Vivaldi and unfortunately Justin Bieber.

Keeping with the radio theme, what does tuning into a frequency mean? Frequency is how many times the wave oscillates (move up and down in the picture above) in one second. The more the oscillations per second, the more energy it has. (Think of a very energetic small child jumping up and down). By tuning in to the correct frequency, your radio converts that light energy into sound without all that annoying static.

This concept can be extended into the other regions on the spectrum. For example Gamma Ray Telescopes. Gamma rays have very high frequencies, meaning of course that they have very high energies. These telescopes have instruments that can detect when a gamma ray hits it, and exactly how much energy it has. This is then converted into images we can see like so:

Source: National Geographic. Image taken using data from Fermi Telescope.

Source: National Geographic. Image taken using data from Fermi Telescope.

The bright spots show where most of the gamma rays are coming from.

And there you have it! A quick overview of light and photons. You are now ready to explore the Universe, just remember to bring your towel.

Until next time, Love, Me 🙂


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