Does it seem obvious? Well, doh. We must assume that physics, chemistry and biology works in much the same way today as yesterday, if we are to explain something about the world. It's called uniformitarianism and is usually linked to gradual changes. In its original form it applies everywhere and always - that the laws of nature have always been the same, that the processes and mechanisms that exist today are the ones that always existed.
When uniformitarianism is pressed to the extreme it gets weak. Today we use explanations that require extraordinary events. Most scientists believe that dinosaurs today - sooner than birds - died out when the giant meteor impact with the Yukatanhalvön 65 million years ago. Luckily, meteors don’t crash into earth that often. And when it comes to the big bang, it seems all the laws of nature be dissolved and it becomes meaningless to talk about a 'before'. So big-bang theory and uniformitarianism doesn’t go very well together.
These extraordinary events are more in the line of thought before Charles Lyell and Charles Darwin. One that was the opposite of uniformitarianism was the French naturalist Georges Cuvier. He believed that it was impossible for species to evolve, that they would die out as soon as they changed even a bit. He also had evidence that there was no gradual change - mummified Egyptian cats which he examined had the same skeleton as today's cats even though they were some 3000 years old. Instead, Cuvier argued that there were other worlds before ours, worlds with other species, which disappeared in global emergencies. He said that it explained why one finds groups of species together when you find fossils. Cuvier had an intellectual position which was in direct opposition to Charles Lyell. And he was dead wrong.
All Cuvier got was weak evidence when he examined his mummified cats. It is always difficult to prove that something does not happen; it can be overthrown by just one observation. Cuvier mistake was that he, as well as so many others before and after him, had a two narrow perspective when it came to time. Today we know that there are organisms that do not appear to have changed in any significant way in 220 million years. That does not mean that there is evolution. During the same time span, the mammals evolved by evolution, including the domesticated cat.
Cuvier big mistake was really that his explanation requires something extraordinary. He said that there was a lack of evidence for gradual evolution, something we have plenty of evidence of today, and at the same time he took it as obvious that there had been previous worlds with different conditions and other species. Where is the evidence that those worlds existed? What kind of natural laws could have caused the disasters that led to the transition from one world to another? Cuvier theories show how easy it is to find an explanation and how difficult it is to prove a claim.
Today most scientists a position that is much closer to Charles Lyell than Cuvier. Modern science is based on what we can observe today, the experiments we can do and the evidence we can gather in the real world to support or reject hypotheses. Still the contemporary position is not as extreme as that of Charles Lyell. The research of today has a stronger emphasis on the empirical and experimental evidence. And that’s a good thing. But it had been a longer road to get there without Charles Lyell.