[b_sharp]

" If you've never seen an indy car do 400 miles per hour, it would not be reasonable to assume that it could do so. If you've seen one pushed to the redline to do 220, then it becomes unreasonable to assume they can go much faster because you know the care is redlining at 220 - which means the engine is near blowing."

Change the gearing in an Indy car and 220 will not be a limit. Place an Indy car on a flat straight track and with current gearing 220 would not be a limit. CART cars were averaging 230mph at Indy and at Detroit. For the average to be 230mph on an oval, the straightaway speed would have to be a fare bit higher.
Our 'observation' of the limits of the current architecture (eg. redline point) does not make 400mph 'unreasonable'. What would affect the 'reasonableness' of 400mph is the understanding of the underlying physics involved in getting the car to reach that speed given its environment.

"How then can one claim it reasonable to assume that 14C was remaining constant in the atmosphere when it isn't currently.

When using Carbon 14 to date recent ages, potential variances are taken into consideration. Do you really think scientists would miss something as obvious as that? I'm afraid that with your level of knowledge you would be extremely hard pressed to come up with any problems with dating that scientists have not already considered.

"How can one "reasonably assume that half-lives remain constant over time if you have no basis in knowledge as to whether such an assumption is reasonable or not.

E=MC².

If half-lives were shorter in the past there would be evidence of such.

[Havoc]

What would affect the 'reasonableness' of 400mph is the understanding of the underlying physics involved in getting the car to reach that speed given its environment.

You made my point. If you Know something, then assumptions based on what you know are reasonable within limits. If you don't know something, then assumptions with regard to unknowns are blind and therefore not "reasonable". Practicality.

When using Carbon 14 to date recent ages, potential variances are taken into consideration.

That's what I hear..

Do you really think scientists would miss something as obvious as that?

Apparently they did for some time as the fact of variable nature of 14C sent everyone into a CYA dance for a while. I remember the flurry of articles about it.

If half-lives were shorter in the past there would be evidence of such. Really, how would you know what that evidence would be? Some have suggested that "assuming" the conditions of the origin of the earth, the result would be extreme heat that would have destroyed the earth. That's great if their assumptions are right. Given they don't know the conditions and that any such assumptions are inherently unreasonable as a result, No one can really say heat would be problematic.. much less detectable.