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El_Cadejo's avatar

Does time move slower at the equator?

Asked by El_Cadejo (33660 points ) 3 weeks ago

I was recently watching a video about “What if the earth suddenly stopped spinning” . In the video the presenter talked about the speed the earth is moving at different latitudes on the planet. This got me thinking, if the earth is moving quicker at the equator shouldn’t time move more slowly a la Einsteins principles of relativity?

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16 Answers

jerv's avatar

Considering the speeds involved compared to the speed of light, it’s negligible.

We’re approximately 24,000 miles in circumference (rounded to simplify math), and rotate every 24 hours. Compare 1000 miles/hour to 186,000 miles/second (669,600,000 miles/hour) and you’ll find the time dilatation virtually nil. Not quite zero, but close enough.

Thammuz's avatar

It’s kinda like how gravity should be lower the higher the altitude. It does but it’s barely noticeable.

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LuckyGuy's avatar

The factor you need to calculate is sqrt ( 1 – (v^2/c^2)) where v is the velocity and c is the speed of light. If we call velocity of a person at the Noth pole zero and the person at the equator v we can say v is roughly 40,000 km/24 hours = 1666 kph = 463 m/s. The speed of light is roughly 300,000,000 m/s. v^2/ c^2 is about 2.4×10^-12. Now subtract that from 1 and take the square root and you get…. something really small.

Time moves more slowly on the ISS, roughly 0.014 seconds per year, and that is moving about 16 times faster than the equator. As a crude first order estimate you can divide that by 16 to get less than one millisecond per year.

zenvelo's avatar

Well, it takes only a day to make one year at the poles (6 months of light, 6 months of dark), but at the equator it’s 365 days of 12 hours light/12 hours dark. So the equator is slower. :)

kritiper's avatar

Only man can conceive of the concept of time so, no, it doesn’t. All time is the same in it’s own zone.

cazzie's avatar

@LuckyGuy absolutly wins this question.

Dutchess_III's avatar

It’s not just a concept @kritiper, any more than gravity is a “concept.”

LuckyGuy's avatar

@cazzie Since you commented, (and I was eating supper) I felt I owed it to the collective to figure out the real number rather than simply estimate.
Using relativity, the difference between someone at the pole vs someone at the equator would be 37.56 microseconds at the end of a year.

I also recalculated the numbers for ISS and got 0.011 seconds at the end of a year. I had to make assumptions for altitude and orbital velocity so the NASA value of 0.014 sec is probably more accurate.

Dutchess_III's avatar

So the answer is “yes.’ Good job @LuckyGuy! I love smart people.

kritiper's avatar

@Dutchess_III Does your pet (if you have one or any) know what time it is?
Before noon of Nov. 18, 1883, 12:00 noon was when the sun was directly overhead no matter where you were. After that time and date, the time was fixed according to the railroads. It’s a concept. Without people to know of it, it doesn’t exist.

jerv's avatar

@kritiper Time exists; it’s the concept of measuring time that varies.

kritiper's avatar

@jerv As I said, time only exists in the minds of men. It is not my idea that it is a concept, just my reporting that it has been determined a concept by those in the know. Otherwise, the only thing that matters is right now.

kritiper's avatar

After more study on the subject, I find that Albert Einstein thought of time as a concept, since some might like to know who “those in the know” are.
” My solution was really for the very concept of time, that is, that time is not absolutely defined but there is a inseparable connection between time and the signal velocity. Five weeks after my recognition of this, the present theory of special relativity was completed.” -Albert Einstein, Kyoto Address, 1922
It would appear that time itself does not slow down, but more accurately, the devices that measure that time since time is a measurement of passing events as they relate to the people who wish to measure them.
And moving clocks run slower than stationary clocks. A clock at the Equator will run slower than a clock (or even the same clock) placed at the North Pole. I depends on your point of view, literally.
“It might appear possible to overcome all the difficulties attending the definition of ‘time’ by substituting ‘the position of the small hand of my watch’ for ‘time.’ And in fact such a definition is satisfactory when we are concerned with defining time exclusively for the place where the watch is located; but it is no longer satisfactory when we have to…evaluate the times of events occurring at places remote from the watch.” -Albert Einstein, ‘The electrodynamics of moving bodies’, 1905
(Excerpts taken from the book “Einstein’s Mirror” by Tony Hey and Patrick Walters, Cambridge University Press, 1997)

El_Cadejo's avatar

@kritiper As said by the ever wise Ford Prefect “Time is an illusion, lunchtime doubley so.”. Still, the question was about how we as humans measure time.

kritiper's avatar

@El_Cadejo Yes. Clocks, which measure time, are affected by movement. Time itself is unaffected. The question would have been more accurate to have been directed to the passing of time as measured by clocks rather than just dealing with the issue of time alone.

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