The Science of Light, the Heartbeat of the Universe

A particle, a wave, an energy field, the speed police … what is light?

Lenka Otap
Jul 31, 2020 · 10 min read
Image for post
Image for post
Photo by Jude Beck on Unsplash

“The vastness of the heavens stretches my imagination — stuck on this carousel my little eye can catch one — million — year — old light. A vast pattern — of which I am a part… What is the pattern, or the meaning, or the why? “ — Richard Feynman

Light. One of nature's wonders, that we take for granted because we see it every day. Literally, we not only see it — but we see nothing but it.

Image for post
Image for post
The Milky Way as observed in different wavelengths. From the longest radio waves at the top to the shortest gamma rays at the bottom. The optical image, that we would see with our eyes, is the third one from the bottom. Note all the dark areas, which are due to dust. We can see through the dust with longer wavelengths and hence be able to see deeper into the galaxy. Image source: https://asd.gsfc.nasa.gov/archive/mwmw/mmw_images.html
Image for post
Image for post
My mindmap of the electromagnetic force, which is the fundamental force that light consists of, and all the connections between other definitions for light. Parts of this mindmap will be zoomed in on in the following sections.

Light as an electromagnetic wave

The electromagnetic wave is also one of the four fundamental forces: Electromagnetic force. The force is a wave propagating through space at the speed of light.

Image for post
Image for post
The electromagnetic wave and its properties.

Our vision and light detection

When we observe with our eyes, we detect the light reflected from surfaces. Our eyes can detect electromagnetic waves that are reflected, but only if the wave has a certain wavelength between approximately 400 and 750 nm. We call light with shorter wavelength for UV (Ultraviolet) light, X-rays, and the shortest wavelengths for gamma and cosmic rays, while longer wavelengths are IR (infrared), microwaves, and radio waves.

… and the rest of the electromagnetic spectrum

The shortest wavelengths in the spectrum are the cosmic rays and the gamma rays, which are deadly for our cells because they carry enough energy to break up the structure of molecules and cells.

Image for post
Image for post
Image for post
Image for post
Artist Nickolay Lamm, known for his photo manipulations, created a series of images illustrating wifi signals as different colors, traveling from a source as a sphere or from different sources. Image Credits: Nickolay Lamm.

Light as particles

“Is he a dot, or is he a speck?
When he’s underwater does he get wet?
Or does the water get him instead?
Nobody knows, Particle man”
Particle man, song by They Might Be Giants.

A particle is a quantum of matter or energy, and the photon is defined as the smallest possible quantum of electromagnetic radiation, where a quantum means a quantity or amount. Unlike in our macro-world, a particle can only have discrete levels of energy and this is what quantum mechanics is all about.

Image for post
Image for post
Light defined as a particle, the photon.

Light as quantum fields FTW!

A modern way of looking at the particle and wave duality is to imagine the fabric of space consisting of endless particle fields. There is a field for every type of fundamental particle and the most common examples are the electron fields and the electromagnetic fields interaction.

Image for post
Image for post
Particles, including the fundamental forces, defined as excited particle fields.

Our experience of the Universe is defined by light

The electromagnetic force is not only what defines our vision, but it also defines our other senses. When we touch something, it’s once again the electromagnetic force working.

Image for post
Image for post
Some random general properties of light, that I find fascinating.

General properties of light

“What if I could ride a beam of light across the Universe?” — Albert Einstein

Light is not only fundamental for us and for how we see and define the Universe, but it also has properties that seem to define the Universe.

Predict

where the future is written

Sign up for Predict Newsletter

By Predict

Monthly updates on science and technology shaping our future. Take a look.

By signing up, you will create a Medium account if you don’t already have one. Review our Privacy Policy for more information about our privacy practices.

Check your inbox
Medium sent you an email at to complete your subscription.

Lenka Otap

Written by

Computer scientist and almost-astrophysicist. Curious about life, the universe, and everything. Are you too? https://www.facebook.com/groups/scienceandcuriosity

Predict

Predict

where the future is written

Lenka Otap

Written by

Computer scientist and almost-astrophysicist. Curious about life, the universe, and everything. Are you too? https://www.facebook.com/groups/scienceandcuriosity

Predict

Predict

where the future is written

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store