Uniformitarian assumptions are frequently used in creating estimates of the age of the earth and the universe.
A scientist measures current processes, and extrapolates those processes into the past to make an estimate of the age of the earth.
A Uniformitarian assumption is an assumption that the way things are right now, are the way things have always been.
It is a reasonable assumption, to a point, but there are cases where uniformitarian assumptions fail.
Moon recession is a case where the uniformitarian assumption has a limited range of applicability.
The moon is known to be receding away from the earth at a rate of 1.5 inches per year. That is the current rate. Physics tells us that the recession rate would have been faster in the past. If we extrapolate backwards, the moon would have been in contact with the earth 1.5 billion years ago.
No one thinks this happened, because it would have been catastrophic for life on the planet. But if 1.5B years is absurd, then even more so is the standard old-earth assumption of 4.5B years.
Clearly the uniformitarian assumption is valid only within a limited range, and we don’t really know where that range begins.
https://www.space.com/moon-drifting-away-from-earth-2-5-billion-years
https://answersingenesis.org/astronomy/moon/lunar-recession/?srsltid=AfmBOoqWrD1iota4wJGENIz4coVM3GjrYfk36yEwfVSQ2gP8olZRfuMr