What Einstein Discovered
In 1905, Albert Einstein showed through his theory of special relativity that light always travels at the same speed no matter who measures it. He also discovered that energy and mass are connected through the famous equation E=mc². This means that as an object moves faster, it gets heavier and requires more energy to speed up further.
The Energy Problem
As any object approaches the speed of light, the amount of energy needed to push it even a tiny bit faster grows enormously. Once you reach speeds very close to light speed, you would need essentially unlimited energy to go any faster. Since unlimited energy does not exist, nothing can actually reach or exceed the speed of light.
Why Light Can Travel at Light Speed
Light is different from objects with mass. Light particles, called photons, have no mass and always travel at light speed through empty space. For massless particles like photons, the speed of light is not a limit they approach but rather their natural travel speed.
Universal Implications
Because nothing can travel faster than light, information cannot spread through the universe faster than light speed either. This means there are cosmic speed limits on how quickly events can influence each other across space. These limits fundamentally shape how the universe works and prevent certain things from being possible.
Experimental Confirmation
Scientists have tested Einstein's predictions countless times over more than a century. Every experiment has confirmed that nothing travels faster than light. Particle accelerators, astronomical observations, and precision laboratory tests all support that light speed is indeed a universal limit. 
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