As we, being objects with mass, approach relativistic speeds, our masses continue to increase, and the energy required to propel us continues to increase; once we are near enough to the speed of light, a major mathematical and physical conflict occurs: not only are we now composed of infinite mass, but we also require infinite energy to propel ourselves. Considering the fact that there is not an infinite amount of energy, or mass, for that matter, in the universe, it is reasonable to believe that the speed of light is unattainable for us massive beings. Our travels are limited to short, interstellar neighborhood voyages. Even so, our failure in breaking physics, at least now, raises the question: what does actually travel at the speed of light, or for that matter, what even is the speed of light? In this chapter, we are to discuss the speed of light and the objects it is restricted to.

References:
Speed of Light - Wikipedia
https://en.wikipedia.org/wiki/Speed_of_light
Parallax Angle (Seconds of Arc) - NASA JPL
https://www2.jpl.nasa.gov/teachers/attachments/parallax.html
Luminiferous Aether - Wikipedia
https://en.wikipedia.org/wiki/Luminiferous_aether
Lorentz Transformation - Wikipedia
https://en.wikipedia.org/wiki/Lorentz_transformation
Caesium Standard - Wikipedia
https://en.wikipedia.org/wiki/Caesium_standard
History of Light - Photon terrace
https://photonterrace.net/en/photon/history/
A Very Brief History of Light - M. Suhail Zubairy
https://link.springer.com/chapter/10.1007/978-3-319-31903-2_1
Refractive Index - Wikipedia
https://en.wikipedia.org/wiki/Refractive_index
Lorentz Factor - Wikipedia
https://en.wikipedia.org/wiki/Lorentz_factor
Massless Particle - Wikipedia
https://en.wikipedia.org/wiki/Massless_particle