=Frayed Knot;2878943]I'm not sure what you mean here by "true." The point is, that's how it's defined. The very definition of one second is a certain number of cycles of a specific transition in the cesium atom (it's nine some-odd billion of them, not one, but that doesn't matter here).
I have found that atheists are always averse to any absolutism. For the atheistic relativist, admitting that a behavior is absolutely moral or immoral is getting dangerously close to the need for a Moral Prescriber which is above man. Here you post that truth is "how it's defined." So, for you truth is relative, or there is no such thing as truth. But is that true? If truth is relative or "how it is defined," then what I define is true and what you define is true, so nothing can be true or untrue. If so, we really could not have a debate. But is something true and not true at the same time and in the same way? No. This is not possible.
You argued that the cesium atom is your ultimate standard ("a second is a certain number of cycles of a specific transition in the cesium atom"). But how do you know how long a second is?
Think of it like this - the meter used to be defined by the length of a certain metal rod in Paris. If someone had told you that this was the ultimate standard of what a meter was, and then that person asked you how you knew that this was a "true" meter, what would you say? That's how the meter is defined!
On a good day, I weigh 230 lbs and I am 6 feet, three and one-half inches tall. If you measure me with a 10-inch-per-foot ruler, would it change how high I really am from the ground to the top of my head? If you weighed me with a 12-ounce-per-pound scale, would I actually weigh more?
Same with the second and cesium atoms.
How do you know the cesium atom will exist tomorrow? How do you know that the cesium atom will behave tomorrow as it has today?