There is no evidence that life spontaneously arose on earth beyond the fact that we exist.
Not just 'we', but a vast variety of life. The evidence we have is that at one time conditions on Earth were inimical to life as we know it. Shortly (in geological timescales) after conditions on Earth became compatible with life as we know it, very simple life appeared and spread rapidly. We also have evidence that many of the complex molecules on which life relies (the 'building blocks' of life) were available in the environment.
Our own lab experiments have shown that many of the reaction cycles of simple metabolic pathways, some of the more complex molecules of life, cell-like vesicles, and other cellular structures, can all spontaneously appear in conditions believed to be very similar to those when the first evidence of life appeared.
We have a good thermodynamic explanation for why spontaneous self-assembly of complex systems occurs under those conditions, and a number of plausible hypotheses being tested for how life might have arisen using those processes.
Creation would be a better explanation for a great many reasons.
Well, I don't know how you judge a good explanation, but for me (and many scientists & philosophers), a good explanation should make testable predictions (so you can find out if it's wrong); it should have specificity, so it gives an insight into and understanding of the particular phenomenon it explains; it should preferably have some scope so that insight & understanding can be seen to apply to other phenomena; it should be parsimonious so that it introduces no unnecessary or unknown entities (Occam's razor); it should not raise more questions than it answers, particularly unanswerable questions, and it should preferably be consistent with our existing body of knowledge; finally, an explanation that can directly explain
anything is not really an explanation at all.
Now, not all explanations can satisfy
all of those criteria, but creation (if that means invoking some kind of 'creator'), is interesting in that it satisfies
none of them. As I have said many times in these forums, I don't see how it is any better than saying it was 'Magic!'.
If you can make a reasonable argument for why the criteria above are not good ways to judge an explanation,
or show how your creation explanation is a better explanation than the 'Magic!' explanation, then we can discuss the merits of the creation explanation.
Since the process cannot be duplicated it cannot be proven by the scientific method.
The scientific method does not prove things, it can provide evidence to increase or decrease confidence in an explanation; at best, it can
disprove an explanation by showing that its predictions are false.
We don't have to duplicate the exact process by which life arose - we'll probably never know the exact process. We don't even have to demonstrate the whole process in one go; we only have to demonstrate that every step of
a process to produce simple life can occur, and that they can plausibly link together.
Since the estimate is flexible and a plugin to the equation it is meaningless.
I'm inclined to agree with you on that - many people have taken it seriously and put in estimates that support their views of the incidence of life of various levels of complexity. The answers vary by many orders of magnitude.
We may have reasonable estimates for a few of the terms, but I see it more as a warning of the futility of making numerical estimates with multiple dependent unknowns.
