Jupiter’s Clock and the Birth of Light’s Speed 🌠Part 1# Foundations of the Finite Light Hypothesis

The postulates of “The Special Relativity of Gravity,” proposed by Albert Einstein in 1905, were mainly based on numerous observations regarding the measurement of the speed of light since the 17th century. The very 1st attempt at measuring the speed of light was made by Danish astronomer “Ole Romer” in the year 1676, where he was able to prove that light doesn’t travel instantaneously but has a finite value. Although Ole Romer’s observations & interpretations did not provide a true value for the speed of light, he successfully laid to rest the long-standing debate on light’s true speed, namely whether light is instantaneous or has a finite speed. Later on Dutch mathematician, horologist, astronomer & physicist “Christiaan Huygens” using Ole Romer’s observations on “Eclipses of Jupiter’s moon Io” & studying Earth’s orbital diameter along the Sun, was able to come up with an estimate value for the speed of light of approximately 220,000 km/s (actual value of speed of light = 3*10^8 m/s), meaning about 25% lower than the actual light speed. Later, about 250 years after Ole Romer’s discovery, in 1926, American physicist Albert Michelson provided a much more precise value of 299,796 km/s using a rotating mirror apparatus setup.

Note : In between these 250 years & even post 1926, there were many attempts made by different scientists & physicists to determine the most precise value of the speed of light, example French physicist “Leon Foucault” in the year 1862 measured the speed of light to be 298,000 km/s using an apparatus consisting of a stationary mirror, a rotating mirror & a light source. British physicist “Keith Davy Froome” in the year 1958 published the measurement of the free-space velocity of electromagnetic waves to 299,972,500 m/s

Calculating the speed of light is never easy, especially when compared to measuring the speed of someone walking or measuring the speed of a vehicle, which can be easily done by noting the distance travelled by the vehicle in a certain period of time & then simply dividing that distance travelled by the time taken & we’ll have the speed of the vehicle. For example, if a car covers a 100-meter distance in 10 seconds, then the speed of the car will be 10 meters/second. But measuring the speed of light cannot be done using the same method, as light travels so fast that in approximately 1.28 seconds to 1.3 seconds, light from Earth can reach our moon. This same concern was being discussed by great ancient minds for ages, like the great Greek philosopher Aristotle, who believed that the speed of light was infinite, meaning that as soon as someone switches on the light, it fills the entire available space. Now, considering the super-fast speed of light, without the use of technology, switching on lights in a confined space, or even a larger room, will always feel instantaneous & infinite. But another Greek philosopher, Empedocles, who lived in the pre-Socratic era & even before Aristotle, thought that the speed of light was finite, but in that era there was no technological capacity for him to prove his thought.

Note : Aristotle was hugely influenced by the works of Empedocles, even though he shared a different viewpoint with Empedocles, considering the nature of the light & its speed

This debate regarding the nature of light continued till the 17th century without much progress. In fact, famous German astronomer & mathematician “Johannes Kepler” even he believed that light was instantaneous & a non-material substance without any mass. He believed that the Sun stayed fixed as the universe’s center emitting light isotropically in all directions, acting as the source of energy for all planets to keep moving.

Then in the 17th century, the 1st piece of evidence with respect to light’s true speed was formulated by a young Danish astronomer named “Ole Romer”. Born in 1644 in the city of Aarhus, Denmark, Ole Romer was quickly considered to have a gifted mind & at a young age of 18 got himself enrolled for “mathematics & astronomy” in the “University of Copenhagen”. While studying, he met “Erasmus Bartholin” who worked as the professor of “geometry & medicine” in the university. Impressed with Romer’s intellect & curiosity, Bartholin took him under his wing & became his mentor; he even asked Romer to shift to his place, which Ole Romer gratefully obliged. At that time, Bartholin was working to organise, prepare a manuscript & have published the many voluminous, unpublished naked-eye astronomical observations of the great Danish astronomer “Tycho Brahe” that he had compiled during his lifetime without making them public. The then King of Norway & Denmark, “King Frederick III”, had entrusted Erasmus Bartholin with this task of organising & preparing a manuscript from the many unpublished observational logs of Tycho Brahe’s lifelong work. These unpublished observational logs were purchased by “King Frederick III” from Tycho Brahe’s heirs in the year 1655 & later handed over to Bartholin for this scholarly project. Ole Romer was more than happy to assist Bartholin in his scholarly work, having access to raw data of the many exceptional works of the great Tycho Brahe, which eventually helped Romer to deep dive into astronomy, physics & mathematics & also perform his own research on the subject. But unfortunately, this entrusted project was never fully completed by Bartholin & his assistant Ole Romer; the incomplete manuscript, along with many observational logs of Tycho Brahe, was eventually handed over to French astronomer & priest “Jean Picard” who took these logs back to Paris Observatory in 1672. Before 1672, Erasmus Bartholin went on an expedition to Iceland in the year 1668, & brought back transparent calcite crystals called “Icelandic feldspar” on his return back home. Later, while examining a single transparent “Icelandic feldspar” calcite crystal, Bartholin noticed that when he saw through the crystal, objects appeared doubled. He then drew a line on a piece of paper & placed a single Icelandic feldspar crystal over it & he could see 2 distinct lines. On rotating the crystal, Bartholin noticed that one image remained fixed while the other moved in a circle around it as the crystal rotated. Bartholin understood that a single light beam was getting split into 2 on contact with the calcite crystal, he named these refracted light rays as the “Ordinary Ray”, which followed standard laws of refraction & the “Extraordinary Ray”, which did not. This way Bartholin made an accidental discovery of the optical phenomenon of “Birefringence”, meaning Double Refraction of light when a single beam of light is passed through a transparent calcite crystal. Now even though Bartholin himself could not explain this phenomenon of Double Refraction, as the concept of light polarization was yet to be understood, but this discovery gave the foundation to the study & discovery of “The Wave Theory of Light” by Dutch mathematician, horologist, astronomer & physicist “Christiaan Huygens” developed in the years 1676-77, communicated the following year in “Académie des sciences” (The French Academy of Sciences) in Paris & published in the year 1690 with his book titled “Treatise on Light”. Also, to note, Bartholin’s discovery of Double Refraction was in direct contradiction with Isaac Newton’s optical theories, but nevertheless, Erasmus Bartholin published his findings in the year 1669 with his book titled “Experimenta Crystalli Islandici Disdiaclastici Quibus Mira & Insolita Refractio Detegitur” (Experiments on birefringent Icelandic crystal through which a marvellous and unusual refraction is discovered). This entire episode of Bartholin’s discovery of Double Refraction was assisted by Ole Romer, still living at his mentor’s place, which made Romer’s interest in the study of light peak even more than before.

Links :
Christiaan Huygens “Treatise on Light” ==> https://archive.org/details/treatiseonlight031310mbp/page/18/mode/2up

Erasmus Bartholin “Experimenta Crystalli Islandici Disdiaclastici Quibus Mira & Insolita Refractio Detegitur” ==> https://www.digitale-sammlungen.de/en/view/bsb10225829?page=24,25