The discovery and implications of the speed of light
History:
The speed of light is approximately 299,792,452 m/s and represents the universe’s speed limit; nothing can move faster than it. The constant was first quantified in the 19th century and formed the foundation of modern physics. By discovering the speed of light, we gained a deeper understanding of its obscure properties. The challenge to measure the speed of light began during the early 17th century when a Danish Astronomer, Ole Roemer, made the first effective estimate by observing the delay in eclipses in Juipuiter’s moons. His observations made a breakthrough in the world of physics at the time and debunked the assumption that light travelled instantaneously. In the mid-19th century, James Clerk Maxwell derived equations that solidified light as a constant denoted as c, which illustrated light as an electromagnetic wave travelling in a vacuum at constant velocity. In 1905, Einstein’s special theory of relativity established the constant c as the universal speed of light for energy and matter.
Why can no object travel at the speed of light:
Before discussing why nothing can travel at or past the speed of light, we must consider classical and relativistic momentum. Both classical momentum and relativistic momentum remain the same at lower speeds, as shown in Figure 1, but as velocity approaches the speed of light, we can see classical momentum continues in a constant linear fashion as opposed to relativistic momentum exponentially growing to infinity. The linear and asymptotic trends observed can be attributed to their respective formulas, as seen in Figure 1. Relativistic momentum’s only difference from classical momentum is its denominator. This difference is the reason why the relativistic momentum graph creates an asymptote at the speed of light growing exponentially to infinity, implying that it takes infinite momentum to travel at the speed of light,t which is not possible because an infinite amount of momentum requires an infinite amount of energy. Classical momentum was derived by Isaac Newton by considering everyday experiences and not speeds close to or at the speed of light, which is why the classical model is still used for non-relativistic velocities.
Figure 1: Classical momentum vs relativistic momentum provided by Science Ready
Applications:
There are so many important applications after the discovery and refinement of the speed of light, such as the speed of light defining the concept of a “light year” being the distance it takes light to travel in one year, allowing scientists to make better and more readable measurements in our universe. An example of a light year in a practical scenario is when observing light from very distant stars. It is like looking back in time, as we see now; it could have been created millions or billions of years ago.
The speed of light also has large implications for technology. Global Positioning System (GPS) satellites require precise timing for location search. If signals between satellites and receivers travel at the speed of light, it would undergo relativistic effects such as time dilation. To counteract these effects, GPS devices are calibrated to ensure accurate navigation and mapping.
Experimental proof:
In 2011, the OPERA experiment reported observations of neutrinos travelling faster than the speed of light. If this were true, there would’ve been a massive hole in Einstein’s theories of relativity and, therefore the rest of modern physics as a whole. Fortunately, a better investigation of the measurements showed that the neutrino wasn’t travelling faster than the speed of light, but rather, the observations were tainted because of experimental errors and faulty equipment. After corrections were made to the experiment, the scientist concluded that the speed of the neutrinos approached the speed of light and did not reach or surpass it.
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