They have what are called "prototypes" of pound weights and kilograms. Measuring rods for feet, yards & metric measurements like meters.
For example, they have a "Meter Standard" a reinforced bar of platinum alloyed with exactly 10% iridium. When they want to know the exact measurement of a "meter" they cool this bar down to 0 degrees Celsius at a sea level of 45 degrees latitude then they know they will have the exact tip to tip measurement of a meter.
That bar is known as prototype #27, because the original is kept in a suburb of Paris at the International Bureau of Weights & Measures.
We Christians also have a measuring rod that never changes. 2 Timothy 3:16-17 tells us:
"All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, 17 so that the servant of God[a] may be thoroughly equipped for every good work."
Remember, there's no substitute having scripture in your heart and mind. Do not allow this world to dictate who you are and what to believe in.
Memorize scripture and let it be your life's standard.
It's your protection from devil's lies and deceptions.