Because the scientific consensus is 4.5/4.6 billion years, not 200 million. And that's been the case for several decades now. So wherever you pulled the 200 million from (your hat?), it wasn't a scientific source. No, it is simply deducible based on the stuff you write down. For example, suppose I told you that "my source" tells me that Jesus met the pink undetectable 7-headed leprechaun that lives in my garage... You would be able to deduce that whatever my source was, it won't be the bible, correct? For the reason that you know perfectly well that the bible doesn't mention any undetectable 7-headed leprechaun(pink or otherwise). That's the same logic that is being applied here. Whatever your source was for "200 million" - it wasn't a scientific source. Because we know that the scientific source will state it is 4.5 billion instead. Yep. And the fact is that scientific sources will say it is 4.5 billion, not 200 million. And that is how we know that whatever your source was - it wasn't a scientific source. Just like you would know that whatever MY source was for the 7-headed leprechaun - it wasn't the bible (no matter if I claim it is). Nope, as I have just demonstrated to you. You don't require "supposition, guesswork, gambling, blind faith and foolishness" to deduce that my source for the 7-headed leprechaun is not the bible - regardless of my claims, right?