Science is hardly on top of this "light" thing. Light is not necessarily the fastest object in the universe, or do you know for certain otherwise? You already take it on faith that the speed of light is, what? c. 386,000 miles per second? Your reason has led you to accept the testimony of several others who claim to have measured it. That's okay. I believe it, too. But to reject outright the suggestion that the speed of light may not have always been constant is, well, like rejecting the notion the earth is spherical before checking it out.
Darwinism has been an unwitting proponent of flat earth "science." Too bad it clings to education like a bad barnacle.
Actually it is the other way around. The speed of light in a vacuum is a constant and has been defined as exactly 299792458 meters per second.
BTW, you can roughly measure the speed of light yourself with nothing more that a microwave oven, a ruler, and a meltable food such as cheese or chocolate.