Where’s the scientific evidence that the earth is 4 billion yrs old?
4.54 billion years +/- about 50 million years.
The best estimates for the age of the earth come from radiometric dating, specifically lead-uranium dating of zircons. However, there are multiple other types of radiometric dating that confirm this.
The estimates of the age of the earth have fluctuated wildly through the history of geology. However, none of the
scientific estimates made in the last ~200 years have been less than 10s of millions of years, and none of the estimates in the last 100 years have been less than billions.
The age of the earth has been basically settled at 4.5 billion years (and some change) since the mid 1950s. All we're doing at the moment is refining the second or third significant digit up or down (a bit).
Oh, and the evidence.
https://websites.pmc.ucsc.edu/~rcoe/eart206/Patterson_AgeEarth_GeoCosmoActa56.pdf
Or the universe-13 billion? if that is what they’re ‘predicting’ now.
13.8 billion, +/- about 60 million years
Very, very simplified: We look at the expansion of the universe, then reverse it and we get to a point of time where there sort of stops being a universe (or at least, our local presentation of space-time).
To verify that, we look at the afterimages and microwaves generated by the very rapid initial expansion of the universe.
It’s obvious to even the most untrained eye, that there has been a global flood at some time in history. The sedimentary rock layers are proof enough.
All those PhD Geologists will be kicking themselves. "Sedimentary layers!" they'll say, "Of course". They'll grumble: "If only I'd spent 5 minutes reading forum posts from 'Psalm 27' instead of those 10 years of my life actually studying and practicing geology. Gosh, what a waste against their crushing insight that its obvious to anyone without training".