Rosa Parks sparks Civil Rights Movement. On this day in 1955, Rosa Parks, an African-American, was arrested and charged with violating a Montgomery, Ala., ordinance that required her to relinquish her bus seat to a white passenger. Her act of defiance sparked a yearlong bus boycott in the segregated city.
View full size image. The speed of light in a vacuum is 186,282 miles per second (299,792 kilometers per second), and in theory nothing can travel faster than light. In miles per hour, light speed is, well, a lot: about 670,616,629 mph. If you could travel at the speed of light, you could go around the Earth 7.5 times in one second.
Main article: Speed of light. The speed of light in a vacuum is defined to be exactly 299,792,458 m/s (approx. 186,282 miles per second). The fixed value of the speed of light in SI units results from the fact that the metre is now defined in terms of the speed of light.