Light Matters: What is Light Actually Made of?

| By on The President's Notebook

INTRO BY DEB: While much of our work at BioLogos is about presenting the case for evolutionary creation, we also take the time to analyze scientific proposals made by Christians who oppose evolution and an ancient universe. Today we continue a blog series focusing on a proposal from young-earth creationist scientist Jason Lisle to explain how distant starlight could have reached Earth if the universe were created roughly 6,000 years ago. Our guide through the topic is Casper Hesp, a graduate student in astrophysics and a gifted science writer. This series is intended for readers without any background in astronomy who want to learn more about God’s creation and how to think carefully about issues of science and faith.

In the previous post, we discussed the proposal of Jason Lisle for solving the distant starlight problem: The Anisotropic Synchrony Convention (ASC). In summary, ASC involves using Einstein’s theory of Special Relativity to demonstrate how distant starlight could theoretically have reached earth instantaneously during a literal six-day Creation event. ASC is a way of synchronizing clocks that differs from the standard picture (with a constant speed of light) in such a way that the speed of light is infinite towards any observer. As we discussed in the previous post, this way of synchronizing clocks is allowed in Einstein’s Special Relativity. The ASC description of the universe could be translated into that of the standard convention without changing positions or properties of objects in the universe. In other words, ASC and the standard convention are simply two ways of describing the same universe.

Let’s suppose that we follow Lisle’s lead in rejecting the proposal that starlight was created in transit. Then, the ASC describes a possibly young universe and the standard convention describes a necessarily old universe, while leaving the physical system unchanged. So, did we stumble upon the means of unification between standard and young-earth creationist cosmology? Unfortunately, not quite. One of these two ways is more truthful to the actual physics that underlie our universe. Einstein chose a constant one-way speed of light. How exactly did he motivate this choice? He has been famously quoted for saying, “God does not gamble.” Well, Einstein certainly did not allow himself to make any gamble here, either. He firmly based his framework on our knowledge of the fundamental nature of light waves, which goes back to Maxwell’s work on electromagnetism. I’ll take you through it step by step.1

Introducing electric and magnetic fields

How does light travel? The best answer we currently have comes from James Maxwell, a devout Christian physicist from the 19th century. Initially, Maxwell was not focusing on the question of light. He was trying to understand how electric fields interact with magnetic fields. Not everybody will be familiar with the concept of these fields, so I hope that the physics-minded among you will forgive me for shortly going over some basics. An electric field may be visualized as a collection of arrows that indicate in which direction a positive charge would be pushed if it were placed in the field. Magnetic fields are trickier to understand. For our purposes, it suffices to say that magnetic fields (1) arise from moving charges and (2) bend the movement direction of charges. I purposefully say bend because magnetic forces only act perpendicular to the motion of charges. This notion of perpendicularity will return later on. As these notions are sufficient for the purpose of our discussion, we will not study these fields in additional depth.

A primer on Maxwell’s theory of Electromagnetism

With this extremely concise understanding of these two fields, we can proceed with our treatment of their interaction: electromagnetism. Electric and magnetic fields have an intriguing reciprocal relationship: (1) changes in electric fields cause magnetic fields and (2) changes in magnetic fields cause electric fields. These relationships were defined in Maxwell’s equations. Now, imagine an empty universe with only a single perturbation in its electric field. The magnetic field will respond by changing. Replying immediately to that, the electric field will also change. Essentially, the magnetic and electric fields will start dancing around each other. Moving across space, they “pull” each other forth: an electromagnetic wave. A visualization of this phenomenon can be seen in the figure below.

Is this all we can say? Surely not. Maxwell would not be called a physicist if he had not examined his equations to study this phenomenon further. His famous equations can be studied in vacuum (i.e., without charges) to understand what behavior electric and magnetic fields produce together. This treatment results in the traditional form of the wave equation for both the electric and the magnetic field. The resulting wave equations then completely characterize the behavior of these waves. For example, they show that the electric and magnetic field waves travel perfectly perpendicular to each other, as can be seen in the animation (this property is no coincidence, remember the perpendicularity described earlier). But, much more importantly, one specific term in the wave equation defines how fast the wave travels (v stands for ‘velocity’):

At this point, the job was relatively easy for Maxwell. He simply plugged in the measured values of the physical constants ε0 and μ0 (both come from electromagnetism) to obtain the velocity, about 3.1×108 m/s. He was familiar enough with experimental results in physics to realize that this result corresponded very well with the speed of light according to the available measurements at his time. This led him to propose that, in fact, light itself is an electromagnetic wave. This means that, earlier, when we imagined the electric and magnetic fields dancing with each other, we actually witnessed the birth of a ray of light in our mind’s eye. At this point, I am tempted to say, “And there was light. God saw that the light was good.”

Coming full circle

So now, let us come back to where we started. Maxwell’s equations led to the idea that light consists of electromagnetic waves and that these always travel at the same speed in vacuum. To these findings, Einstein applied the idea that the laws of physics are observer-independent. This gave rise to his assumption of a universally constant speed of light. In turn, this led to his famous framework of Special Relativity (which we introduced in the previous post). Now, Special Relativity still leaves space for the choice of a synchronization convention. In light of our current discussion, we now understand what drove Einstein to assume a constant one-way speed of light: it agrees with the electromagnetic nature of light. Electromagnetic waves have a finite, constant speed. In contrast, Lisle’s proposal assumes a non-constant speed and, moreover, an infinite speed in directions towards an observer. While this way of synchronizing is technically allowed, it does not respect the physical nature of light as Einstein’s choice does.

A Railway Analogy

To understand what went “wrong” here, suppose that the local railway company wants to boast that it operates at travelling speeds that are virtually infinite  into the city. However, their trains suffer from physical limitations and have a maximum speed of about 50 miles per hour. To overcome this quandary, the railway company decides to change the synchronization convention of the clocks on all of its stations. The clocks are synchronized in such a way that trains into the city seem to arrive instantaneously, while trains out of the city travel at half the speed (say 25 miles per hour). With such amazing advertisements, it does not take long before somebody starts a lawsuit against this company (especially since we are talking about the US here). In its own defense, the company might say that this way of synchronizing clocks is technically allowed, just like the standard convention. The judge is taken somewhat off guard by this unusual proposal and decides to consult with expert physicists on the issue. Their advice entails that the accuracy of the advertised claims should be determined using the synchronization which is truthful to the physical limitations of trains (i.e., the standard convention). The judge decides to follow this piece of advice and the railway company loses the lawsuit.

Of course, our example is subject to simplifications. For example, in ASC every “station” has its own synchronization (such that the speed is infinite towards every observer regardless of his or her location). Also, for lightwaves the physical limitations are derived from Maxwell’s theory while those of trains are measured directly. These differences do not change the point of our analogy that physical limitations should be taken into account when discussing speeds.

Looking ahead

In an article published by Creation Ministries International (a YEC ministry), Dr. Sarfati dismissed Lisle’s proposal because it does not correspond with Maxwell’s theory. He considered this solution to be too ad hoc. But does electromagnetism really mean the definite demise of Lisle’s proposal? Not necessarily. Lisle described in his article that God could have specifically chosen the Anisotropic Synchrony Convention for the purpose of communicating Creation history in Genesis 1. So even if this description does not take into account the properties of light, it could have been used as a descriptive tool. In particular, Lisle proposed that it was used to describe a six-day Creation event that occurred less than 10,000 years ago. How much sense does that description make? From here on, we will proceed to answer that question by examining the ASC model itself. First we will translate it to the standard convention to understand the picture on the physical level. As we will see in the coming post, that translation leads to a rather peculiar view of Creation. Essentially, it revives the status of the Earth as the center of the universe. It implies that God “printed” the cosmos geocentrically.


Notes

Citations

MLA

Hesp, Casper. "Light Matters: What is Light Actually Made of?"
https://biologos.org/. N.p., 4 Apr. 2016. Web. 22 November 2017.

APA

Hesp, C. (2016, April 4). Light Matters: What is Light Actually Made of?
Retrieved November 22, 2017, from /blogs/deborah-haarsma-the-presidents-notebook/light-matters-what-is-light-actually-made-of

References & Credits

1. Light actually has a dual nature since it behaves as both a wave and a particle, but we won’t be covering that here.

 

About the Author

Casper Hesp

Casper Hesp is a Master student of Astrophysics and Neuroscience at the University of Amsterdam. Before starting this double programme, he obtained two B. Sc. degrees with the honorific Summa Cum Laude at the University of Groningen in 2015: one in Psychology and one in Astronomy. His research interests are focused on computational approaches for furthering theoretical understanding within both of these fields. He has worked on simulating a diversity of systems such as galaxies, parent-child play in autism, and neural agents in an evolutionary setting. Casper was elected as Student of the Year 2013 of the University of Groningen and is currently a recipient of the Amsterdam Science Talent Scholarship.

 

More posts by Casper Hesp

Comments