Light: The Basics

Hey friends! I am so excited and grateful to be back with you! This session we endeavored to learn about what light is at its most basic level. There are, as I learned, a seemingly endless number of nuanced tangents we can take FROM this point and perhaps some day we'll do that together :) Definitely! For now, so we can make sense of those future learnings and conversations, we are going to cover the basics of what light is.

There will be many sources in which you will find contradictions to a few pieces of what we are going to talk about, namely the ideas that light is either a wave or a particle AND those that prejudicially assume light as a visible entity. I plan to tackle these concepts in this post to arm you with the understanding of those unique pieces of the conversation on light. I am not a professional in this field, so we'll learn bit by bit together and come back to it as we learn more:) Thanks for being here!

Light existed before we understood what we do now about it. There seems to be abundant room to grow in our learning about light, but within its scientifically-pronounced history, light has caused many conundrums for scientists throughout the ages. We do know that light is a form of energy. We know that in a vacuum - energy can neither be created or destroyed only converted from one form to another. You can witness the burner on your stove as a great example as you turn the knob which will engage the ignition for your chosen burner. Once it sends out a spark and engages with the gas, fire will occur. Electric stoves work differently, but once the heat is applied to the underside of a pot of water, the idea is the same - the heat heats up the water and then what? yes, you get a simmer or a boil etc. The water heats and boils and excites and then produces - steam......... Energy shifts and changes its face on us, however it is not lost (in a closed system at least :) )

When light was first being discussed as a form of energy, it was quite a debate as to whether or not it was a PARTICLE or a WAVE. One of the largest debates to this end occurred in the 17th century between Sir Isaac Newton and Christiaan Huygens - Newton voting for light as a stream of particles and Huygens considering it a wave. Particles and waves act uniquely, however as experiments went underway it became evident that in some ways - light acted both like a wave and like a particle. Why does this matter?

Well in science, classifications and laws aid in a more 'predictable' understanding of an experiment. The mental schemas that we have surrounding energy as particles or waves do not neatly adapt to the natural phenomenon of light and therefore we must now (at least FOR now) accept that it is BOTH!

Okay, so we know something about how it MOVES, BUT BACK UP/!!!!!!!!!!!! WHAT is moving? Consider an atom - the smallest unit of ordinary matter! If it freaks you out to think that small, just think of one lego piece - we're cool with that -we can imagine that. That is an atom. Atoms have a nucleus - which is made up of Neutrons (neutral in charge) and Protons (positive in charge). There is an exception in that some common varieties of Hydrogen do not have Neutrons, however for the most part both neutrons and protons are present. Surrounding this nucleus are orbits of electrons, which are negatively charged particles. To simplify our story let's say that atoms prefer to be stable. If an atom absorbs energy and becomes unstable, it will endeavor to expel that energy and this - my friends - is where light is born - at this moment of energy expulsion.

You have your atom - or lego. The atom has received energy and has become unstable and now it needs to release it. In the case of light, we have a photon which is a quantum (or smallest measurable unit) of light. It does not have mass, but rather travels as two perpendicular waves of ELECTRICITY + MAGNETISM in a given direction.

Phew - doing okay? I think we got this far pretty well - still with me?

This is where we encounter the 'is light a wave or is light a particle' debate. When this debate was in its infancy, observations of energy in motion were classified as behaving as particles or as waves. Particles, in theory, can bounce off of one another into opposing directions, they act in a more disbursed fashion. Waves, when they encounter other waves, can act in a variety of ways - amplifying one another, cancelling one another out, continuing in each waves' original direction through one another. There are more complexities beyond these introductory definitions of particles versus waves, however light, as we study it - can fit both families of energy behavior! This can mess with some of the tidy definitions we have established historically, however I often wonder if we were to simply accept something with all its wonder and confusion -it might bare to us more of its nature than we can extract with our fixed ideas.

Now that we have a basic idea of what light is and how it comes to exist, let's dig down to a slightly deeper level about the nature of light. We learned, above, about the nature of light's anatomy as perpendicular waves of ELECTRICITY and MAGNETISM. These relational waves are collectively referred to as electromagnetic radiation, or EM radiation.

Electromagnetic energy comes in many different frequencies and energy levels. Light, as we have always talked about it, is something that allows us to perceive our surroundings with our eyes. THAT light, however, is of a narrow range of frequencies and energy levels that are specifically perceivable to the human eye.

WAIT, WHAAAAAAAAAAAAAAAAT? Yes! In other words, there are some 'versions' of light, or EM radiation that are not observable to the human eye! This can frustrate some of us because we have always talked about light as something that we see. Could it be that we call the human-visible EM radiation LIGHT and refer to the other parts of the spectrum by their own designations? Sure! I just want to make sure that you know that I feel your pain! For me, much of learning is 'unlearning' things I thought of as hard truths.

So, there's invisible light? Okay, well if we want to take it there we can, but a more accurate way of talking about it would be that there are types of EM radiation that are not observable to the human eye. Those include EM frequencies that are more energetic and that have shorter frequencies such as gamma rays, x-rays, and ultraviolet radiation. On the OTHER SIDE of the visible light we just talked about, are less energetic waves with longer frequencies such as infrared, radar and radio waves.

We now know the photon results from expulsion of excess energy from an atom. We understand that light behaves like waves and like particles but have we seen that in action? Well, let's take a look. Light behavior is broadly broken down into four sub-categories:

REFLECTION / REFRACTION / DIFFRACTION / INTERFERENCE

There are subtle variants and unique behaviors within these sub-categories too, just to confuse and inspire us even more! I am going to offer you a few links here (1 and 2 and 3) for those of you who would like to learn more about those categories! If you continue this line of learning, you will learn about the color spectrum of light, the bending of light, the nature of light 'waves' interfering with other light 'waves', the behavior of light around the edges of things and through restricted spaces etc. It can be a fascinating and overwhelming journey. There are other types of behavior that you will run into too! No fear! We love learning. If you find something within this that you'd like to go further into together on WildEsse - email me! and we'll do that ! :)

Before we wrap things up here, it is impossible to end our conversation without addressing something as important as THE SPEED OF LIGHT! If you're a Trekkie like myself, you may have heard some reference to this a million times! What is it? Well, as light has been studied, we have learned that it has a fixed speed!

There are large and less energetic radio waves that can have frequencies as long as 11oo kilometers, and itty bitty gamma rays whose frequencies are ~10 picometers - but they all travel at the same speed! That's a bit hard to imagine - we have this fixed tortoise and the hair mentality about these things, but yes, they travel at a fixed speed in a vacuum*. Just imagine a human running with their itty bitty dog - I mean they're taking vastly different size steps and are different sizes, but their speeds match. *So, what do I mean by in a vacuum? That is to say that as light moves at a fixed speed when it has no interfering surfaces/forces etc. As it engages different surfaces, its speed DOES change. Light's fixed speed (in a vacuum) is 300,000 kilometers/second. Compare that to the speed in the different mediums below; what do you notice?

C= SPEED OF LIGHT

C (vacuum/without interference/influence) = 300,000 kilometers/second

C (through water) = 225,000 kilometers/second

C (through glass) = 200,000 kilometers/second

As you can see, light slows down when it encounters different surfaces. This phenomenon is one of the 4 broad categories mentioned above: refraction. So, there is a 'speed of light,' however within a system - our great ecosystem of Earth- for example, light engages the environment and interacts with that environment in many different ways. Light sometimes remains light, sometimes it becomes heat, other times it becomes more focused or more diffused.

I leave you with these particles of information :) and hope that you can ride the wave enough to find something inspiring to you. Light, for much of our life on Earth (some would say all of our life) is vital. Light interacts with our ecosystem in ways that, along with other entities such as air and water, supports life. It is confusing, inspiring, and SO DARN FAST!

If Earth's sun is 149.6 million kilometers away from Earth and if light travels at C, then how long does it take the light from Earth's sun to get to us on Earth?

>>>>>>>>>>>>>>>>>>>>>>>>>>About 8 minutes and 20 seconds. That's just a really cool fact you can share with your friends. Maybe just hang out for that long sometime and take note of that moment in time. It may make you feel more connected to our great Star :) Just a reminder that light is light is light. If you light a match, the resultant flame's light will travel just as quickly as the natural light from the sun. The same can be said of light emitted from a light bulb. Human-created light has unique sources, but the resultant EM energy abides by the same general rules :)

You guys are the best; I am excited that you shared this journey of light with me, and I look forward to researching many of the topics that you have emailed into me over the past few months!

Have a beautiful week!

~Sarah