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#### Science Forum

1. 21 Mar '18 03:39
the earth spins at about 1040 miles per hour at the equator..so how fast would a person be spinning if at the exact North pole or exact South pole?
2.  DeepThought
21 Mar '18 03:49
Originally posted by @ogb
the earth spins at about 1040 miles per hour at the equator..so how fast would a person be spinning if at the exact North pole or exact South pole?
They'd be rotating about their central point so different parts of their body would be moving at different linear speeds depending how far out from the axis of rotation the bit is. But to practical purposes they'd be stationary.
3.  lemon lime
go phish
21 Mar '18 05:25 / 1 edit
Originally posted by @ogb
the earth spins at about 1040 miles per hour at the equator..so how fast would a person be spinning if at the exact North pole or exact South pole?
That person would be making one full turn every day (24 hours).
As to how fast he would be spinning, I don't know. It depends on how wide he is. His width determines the length (circumference) of the circle the outermost part of his body travels in one day. But however fast that is, a snail can travel much faster than some guy 'spinning' at one of the poles.
4.  sonhouse
Fast and Curious
21 Mar '18 05:37
Originally posted by @lemon-lime
That person would be making one full turn every day (24 hours).
As to how fast he would be spinning, I don't know. It depends on how wide he is. His width determines the length (circumference) of the circle the outermost part of his body travels in one day. But however fast that is, a snail can travel much faster than some guy 'spinning' at one of the poles.
Assume he is 2.4 feet wide, then he would be spinning at the incredible rate of 1/10th foot per hour or about one inch per hour or about 2 cm per hour. Probably won't get dizzyðŸ™‚
5.  DeepThought
21 Mar '18 17:16
Originally posted by @sonhouse and also in reply to @lemon-lime
Assume he is 2.4 feet wide, then he would be spinning at the incredible rate of 1/10th foot per hour or about one inch per hour or about 2 cm per hour. Probably won't get dizzyðŸ™‚
Following the OP I worked on the assumption that we are ignoring the earth's orbital speed, but an effect we've neglected is the precession of the spin axis, which from memory has a period of something like 5,000 years. I don't think it changes the answer by much though.
6.  sonhouse
Fast and Curious
21 Mar '18 19:02
Originally posted by @deepthought
Following the OP I worked on the assumption that we are ignoring the earth's orbital speed, but an effect we've neglected is the precession of the spin axis, which from memory has a period of something like 5,000 years. I don't think it changes the answer by much though.
I forgot to do the circumference so the speed is about 5 times greater, 9 cm per hour. Still won't get dizzyðŸ™‚
7. 22 Mar '18 00:55
so Part II..if a person spends their entire life at the exact North Pole and their brother spends entire life at the equator, which one is aging faster. In other words, which twin will become older, quicker..?
8.  lemon lime
go phish
22 Mar '18 01:29
Originally posted by @ogb
so Part II..if a person spends their entire life at the exact North Pole and their brother spends entire life at the equator, which one is aging faster. In other words, which twin will become older, quicker..?
which twin will become older, quicker

The colder one will become the older one... quicker.
9.  DeepThought
22 Mar '18 03:03
Originally posted by @ogb
so Part II..if a person spends their entire life at the exact North Pole and their brother spends entire life at the equator, which one is aging faster. In other words, which twin will become older, quicker..?
Ha, that's quite a good question - I've just read your post and need to do a little maths to get to the answer. It's complicated by the way the Earth is an oblate spheroid and so the gravitational field at the poles is different from the field at the equator. It's also 3am so you're going to have to wait until tomorrow for your answer. Best guess is that the twin at the pole will have a clock that runs very slightly faster and so will age faster (biological issues with cold, heat, and sunlight notwithstanding).
10.  sonhouse
Fast and Curious
22 Mar '18 17:30
Originally posted by @deepthought
Ha, that's quite a good question - I've just read your post and need to do a little maths to get to the answer. It's complicated by the way the Earth is an oblate spheroid and so the gravitational field at the poles is different from the field at the equator. It's also 3am so you're going to have to wait until tomorrow for your answer. Best guess is ...[text shortened]... faster and so will age faster (biological issues with cold, heat, and sunlight notwithstanding).
And the grav variation due to the fact the person on the equator is moving faster so time will slow down, maybe the two effects cancel?
11.  lemon lime
go phish
22 Mar '18 19:32 / 1 edit
Originally posted by @sonhouse
And the grav variation due to the fact the person on the equator is moving faster so time will slow down, maybe the two effects cancel?
I think the grav variation is probably so slight as to be negligible.

GPS automatically adjusts for time clock variation to insure accurate locations on earth, but I've never read where grav variation is also taken into account. This doesn't mean it isn't or can't be taken into account, it just means I've never read or heard of it being incorporated into a GPS system. But even if it could be incorporated, and might add some extra level of accuracy, I suspect it would be a very complex and complicated adjustment.
12.  sonhouse
Fast and Curious
22 Mar '18 21:59
Originally posted by @lemon-lime
I think the grav variation is probably so slight as to be negligible.

GPS automatically adjusts for time clock variation to insure accurate locations on earth, but I've never read where grav variation is also taken into account. This doesn't mean it isn't or can't be taken into account, it just means I've never read or heard of it being incorporated i ...[text shortened]... d some extra level of accuracy, I suspect it would be a very complex and complicated adjustment.
It is on the sats themselves since they are way up, some 8000 miles up so that would be in a field 1/4th or so of ground level gravity so the clocks would run faster and have to be compensated for. Each of those sats has an atomic clock onboard to track local time flows.
13.  lemon lime
go phish
22 Mar '18 23:56 / 1 edit
Originally posted by @sonhouse
It is on the sats themselves since they are way up, some 8000 miles up so that would be in a field 1/4th or so of ground level gravity so the clocks would run faster and have to be compensated for. Each of those sats has an atomic clock onboard to track local time flows.
Right, but if there is a significant gravitational strength difference between the equator and the North Pole (as DT suggests there may be) it could mean there will be less of a difference in the aging.
Having said that, I can't imagine any surface grav variation completely cancelling out the difference in aging between the twins.

Imagine looking straight down from space at the North Pole. One of the twins will appear to be a point in the center of a circle, and the other appears to be a point on the circle travelling very fast around the center point... and taking into account that (for all practical purposes) the center point remains motionless.
14.  sonhouse
Fast and Curious
24 Mar '18 13:06
Originally posted by @lemon-lime
Right, but if there is a significant gravitational strength difference between the equator and the North Pole (as DT suggests there may be) it could mean there will be less of a difference in the aging.
Having said that, I can't imagine any surface grav variation completely cancelling out the difference in aging between the twins.

Imagi ...[text shortened]... . and taking into account that (for all practical purposes) the center point remains motionless.
But Earth is corkscrewing its way in orbit around our galaxy and the whole galaxy is moving from the gravitational gradients so figuring all that would add to the complexity but I imagine those movements would be effecting the twins at the same rate so can be canceled out as an affector.
15.  lemon lime
go phish
24 Mar '18 16:53
Meanwhile, back at the ranch (here on earth)...

As yet no one has jumped in to prove me (the layman) wrong. This tells me I'm probably right about which twin ages faster than the other.
"The colder one will become the older one."