The Speed of Light: The Universe’s Limit

Light in a vacuum travels at about 299,792 kilometers per second—nature’s fastest speed.
At this speed, light can circle Earth over 7 times in just one second.
Nothing with mass can reach or exceed the speed of light, according to Einstein’s relativity.
Light slows down when passing through glass, water, or air, but never faster than in a vacuum.
The speed of light is so fundamental it defines the meter in the international system of units.
Light from the Sun takes about 8 minutes and 20 seconds to reach Earth.
Looking at distant stars means looking back in time, since their light traveled for years to reach us.
The cosmic speed limit shapes concepts like time dilation and relativity in physics.
Even information can’t travel faster than light, setting limits on communication across space.
The universe itself is mapped in “light-years,” the distance light travels in one year.