859.40 kilometers per hour is about 0.0000008 times as fast as The Speed of Light.

The speed of light (and all other electromagnetic radiation) in a perfect vacuum is known as "c" and measures exactly 1,079,252,850 kilometers per hour, per the formal definition of the meter. While visible light travels close to this speed in air, it slows to 719,501,899 kilometers per hour when passing through the glass of a typical window.

In other words, it's 0.0000007962916210 times the speed of The Speed of Light, and the speed of The Speed of Light is 1,255,821.330 times that amount.

(C) (in a vacuum)The speed of light (and all other electromagnetic radiation) in a perfect vacuum is known as "c" and measures exactly 1,079,252,850 kilometers per hour, per the formal definition of the meter. While visible light travels close to this speed in air, it slows to 719,501,899 kilometers per hour when passing through the glass of a typical window.