***Like did the Earth go zooming around the Sun really fast in pre-deluge times?***
Have you ever heard of Progeria?
It's the disease that causes children to age rapidly and have the body of a 70 year old at age 20.
Point being that you are assuming that things are continuing along just as the have been from the beginning.
Just like all intelleget people once thought that the speed of light was a constant...
(eyes rolling) Not that hoary business again. The earliest several published measurements of the speed of light were several percent greater than the modern (extremely stable) value. So young-earth creationists decided that light was much faster a few tens of centuries ago. This explains why we can see galaxies that are millions of light years away. But that's a hell of an extrapolation! Physicists say that if the speed of light were higher, all the physics tied to it would change as well; the results would be tremendous. Chemistry, etc. wouldn't work properly.
But what I want to argue here is that we don't need to believe in a God who created a world that looks really old even though it is very young. We can believe in a God who created a beautiful world and universe that are intelligible to us -- everything makes good sense if you understand the science. No need for contrivance ("do you believe in progeria?"). Newton and the other great scientists who created the scientific revolution in the 17th century were all profoundly devout men. Modern science would not have arisen without the understanding that God created a universe amenable to human understanding. Newton thought he was learning about God by studying his creation. He was right.
By definition, the speed of light in a vacuum is a constant.