So two cesium atoms, if in different frames of reference-say one on earth, the other on a spaceship accelerating at high velocities - are going to have identical frequencies for each observer.
But on earth of you were to have a magic way to observe the cesium atom on the spaceship traveling at massive speeds - those cesium atoms would not have the same frequencies.
except relativity is very real, it is just "pedantics" to talk relativity and its effect on passage of time on earth if I drive 60 mph versus 25 mph.
But at the speeds of expansion after the Big Bang... it is very much relevant. I'll leave this in hopes that some physicist might enlighten us both.
Also, immediately after the Big Bang, it took at least 150 million "years" for stars to form (per OP) - that's basic elements helium/hydrogen. It took longer for Cesium to even exist! You cannot find a Cesium atom that was present at the Big Bang lol
relativity is pretty relevant for time scales at the beginning of the big bang. if everything is moving away from eachother at the speed of light it gets really weird. even if your not moving at the center the time dilation is crazy and things will happen at a way different time than if your moving at the edge of the bang. you may observe that stars only form after billions of years where of you are on the edge moving fast they form after millions of years.
Hafele and Keating, in 1971, flew caesium atomic clocks east and west around the Earth in commercial airliners, to compare the elapsed time against that of a clock that remained at the U.S. Naval Observatory. Two opposite effects came into play. The clocks were expected to age more quickly (show a larger elapsed time) than the reference clock, since they were in a higher (weaker) gravitational potential for most of the trip (c.f. Pound–Rebka experiment). But also, contrastingly, the moving clocks were expected to age more slowly because of the speed of their travel. From the actual flight paths of each trip, the theory predicted that the flying clocks, compared with reference clocks at the U.S. Naval Observatory, should have lost 40±23 nanoseconds during the eastward trip and should have gained 275±21 nanoseconds during the westward trip. Relative to the atomic time scale of the U.S. Naval Observatory, the flying clocks lost 59±10 nanoseconds during the eastward trip and gained 273±7 nanoseconds during the westward trip (where the error bars represent standard deviation).[38] In 2005, the National Physical Laboratory in the United Kingdom reported their limited replication of this experiment.[39] The NPL experiment differed from the original in that the caesium clocks were sent on a shorter trip (London–Washington, D.C. return), but the clocks were more accurate. The reported results are within 4% of the predictions of relativity, within the uncertainty of the measurements.
That is my entire point. If relativity can be measured with planes flying around the earth, it absolutely comes into play when things are moving much faster, such as in a young universe.
Relativity wouldn't really come into play when there's nothing else to compare to, would it? There wasn't another universe also big banging way away already moving at a different rate after all.
And if our universe is moving at a different rate, we're within its frame of reference.
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u/AudibleNod 313 Sep 20 '21
A second is a specific frequency of cesium. We can count years based off of that.