How do companies that make measuring tools like rulers make sure the product is accurate? Is there a universally ruler that is used to check? How do they make sure the measurements are exact?
In: Engineering
I’ve wondered this same thing except for time.
Almost a billion people in the world use their iPhone to tell the time (and reference it to set their other clocks). So where does Apple get their time from?
Is there a universal clock that all clocks are based on?
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