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atomicclock.now guides & articles

10 in-depth guides on Atomic Clock and related topics.

The science

The science Atomic Clocks in GPS Satellites: Why Timing Is Position Why satellite positioning is really a timing problem, which atomic clocks each GPS satellite carries, the relativistic corrections applied to them, and what a nanosecond of error costs in metres. 6 min read The science Caesium Atomic Clock vs Rubidium and Optical Clocks How caesium, rubidium, hydrogen maser and optical lattice clocks differ in accuracy, size and cost, where each is used in practice, and why optical clocks will define the second next. 6 min read The science How Atomic Clocks Work: Counting the Caesium Second A plain explanation of how atomic clocks work: the caesium-133 hyperfine transition that defines the second, why atoms keep better time than quartz, and how accurate the best clocks really are. 6 min read The science Leap Seconds Explained: Why the Clock Sometimes Says 23:59:60 Why Earth's rotation forces the occasional leap second, who decides when one is inserted, the problems it causes for computers, and why the practice is being abandoned by 2035. 5 min read The science National Time Standards: NIST Time and Its Counterparts What national metrology institutes such as NIST, NPL and PTB actually do, how their atomic clocks are combined into International Atomic Time by the BIPM, and how the public gets that time. 5 min read The science Radio Controlled Clocks and WWVB: How They Really Work How the WWVB, MSF and DCF77 longwave time signals reach a radio controlled clock, why reception is best at night, and why these clocks are not atomic clocks at all. 5 min read The science TAI vs UTC vs GPS Time: The Offsets Explained What International Atomic Time, Coordinated Universal Time and GPS time each are, the fixed offsets between them, why satellite time diverges, and which scale your systems should use. 5 min read The science What Is NTP? The Network Time Protocol Explained How the Network Time Protocol measures and corrects clock offset, what the stratum hierarchy means, the accuracy to expect over the internet, and why NTP slews rather than jumping. 6 min read

Fixing your clock

Fixing your clock How to Sync Your Computer Clock on Any Device Step-by-step instructions to sync your computer clock on Windows, macOS, Linux, iOS and Android, plus how to choose a time server and diagnose a sync that refuses to work. 6 min read Fixing your clock Clock Drift: Why Computer Clocks Lose Time Why every computer clock drifts: quartz tolerance in parts per million, the strong effect of temperature, what virtual machines and sleep add, and how synchronisation corrects it. 6 min read