The instantaneous travel of photons at the speed of light might seem counterintuitive, but it is a fundamental property of electromagnetic radiation according to our current understanding of physics. Let's explore this concept in more detail.
In the realm of classical physics, momentum does indeed require a starting point or a force acting upon an object to set it in motion. However, photons are not ordinary objects and do not behave like particles with mass. Photons are elementary particles that fall into the category of massless particles, which means they have no rest mass. As a result, the usual laws of classical physics, including the requirement for a starting point for momentum, do not apply to them.
According to the theory of relativity, specifically Einstein's theory of special relativity, the speed of light in a vacuum is an absolute constant denoted by 'c.' All massless particles, including photons, travel at this constant speed. It is a fundamental property of the universe, and nothing with mass can reach or exceed this speed.
When a photon is created, it is essentially "born" with its energy and momentum already determined. The creation of a photon typically occurs through processes such as the emission of electrons in atoms or nuclear reactions in the Sun. As soon as it comes into existence, the photon starts traveling at the speed of light, following the wave-particle duality behavior associated with quantum mechanics.
It's important to note that while we can describe the behavior of photons using the language of particles, they also exhibit wave-like characteristics. The wave-particle duality of photons is a fundamental concept in quantum physics, and it allows us to understand their behavior as both particles and waves.
In summary, photons, being massless particles, travel at the speed of light from the moment of their creation because they have no rest mass and are governed by the laws of special relativity. Although it may seem unfathomable from our everyday experiences, this behavior is well-supported by experimental evidence and the current understanding of physics.