Unsurpassable pace, immutable reference of the universe.
Speed is a relative concept. Imagine you are standing at the train platform, and you might think you are still. But a friend of yours sitting in a train driving through the station would say the opposite: for them, you do have a speed! However, no matter who or where you are: in vacuum, light always travels at the same speed. The speed of light is the ultimate speed limit and serves as a reference. This simple and intriguing fact has tremendous repercussions for the evolution of our universe.
The explanation that the mass of an object increases as it approaches the speed of light is a rather common misconception.
How is this possible?