![]() ![]() Modern atomic clocks which use strontium or ytterbium instead of caesium lose one second every 300 million years or so. Some 12 years later, the caesium atomic clock became the international time standard, and over time, atomic clocks became far more accurate. It was accurate to a second in 300 years. The first atomic clock that was accurate enough to be used to set the time was built in 1955 at the UK's National Physical Laboratory. They sound super futuristic, but atomic clocks have been around for more than 60 years. Those microwaves have a particular frequency (the number of full waves completed each second) which can be measured as the atom's "ticking" rate.The energy emitted each time an electron makes a particular jump is always the same, and is in the form of microwaves.Electrons can "jump" between levels when they absorb or release a specific amount of energy.As electrons whiz around the nucleus, they occupy different orbits or "energy levels".A second is defined by the movement of electrons in a caesium-133 atom, which comprises a nucleus - containing 55 protons and 78 neutrons - surrounded by 55 electrons.Rather than looking to the heavens, this form of time-keeping drills into the waves of radiation shrugged off by atoms when they're bathed in laser light. So while astronomical time might do for timetabling and such, science demands precision. Our days are lengthening, by an extra 1.7 milliseconds each century, thanks to our gravitational tango with the moon. For instance, the length of a day was determined by one spin of the Earth on its axis.īut astronomical phenomena tend to slow down or speed up. "Measuring time and frequency with such an incredible accuracy provides a really powerful lens to view the natural world," Mr McGrew said. It turns out they tick, in almost perfect synchronicity, 500 trillion times a second. Study co-author Will McGrew, a PhD student at the National Institute of Standards and Technology in the US, said the clocks' "ticking" is produced by oscillations of radiation emitted when electrons in ytterbium atoms are excited by lasers. More immediately, the clocks could tell us what's going on inside the earth by precisely mapping our planet's bumps and lumps - if the clocks are shrunk, that is. The clocks' exquisite precision, outlined in Nature today, means they can measure how space-time distorts under gravity forces.Įventually, astrophysicists could enlist their help to detect mysterious dark matter. But they won't be used to keep the trains running on time. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |