James Clerk Maxwell didn't calculate the speed of waves through space; instead, he formulated equations that describe the behavior of electromagnetic waves, including their speed. These equations, known as Maxwell's equations, were groundbreaking in the field of electromagnetism and played a crucial role in understanding the behavior of electric and magnetic fields, as well as the propagation of electromagnetic waves.
One of the key results of Maxwell's equations is that they predicted the speed of electromagnetic waves in a vacuum (such as space). The speed of electromagnetic waves in a vacuum, according to Maxwell's equations, is approximately 299,792,458 meters per second (often rounded to 300,000 kilometers per second or 186,282 miles per second). This speed is commonly denoted as "c" and is the speed of light in a vacuum.
Maxwell's work in formulating these equations was instrumental in demonstrating that light is an electromagnetic wave and that it travels at this constant speed through a vacuum. Einstein later built upon this understanding in his theory of special relativity, which incorporated the constant speed of light as a fundamental principle.