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#1
09-12-2019, 05:04 PM
 Charter Member Join Date: Aug 2001 Posts: 16,450

## What time is it a mile east of me.

Okay, I know the official time is the same time as me. But if we were to do the math, what time would it be a mile east of me if it were exactly 12pm?
#2
09-12-2019, 05:07 PM
 Guest Join Date: May 2015 Location: 123 Fake Street Posts: 8,101
What lattitude?
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It may be because I'm a drooling simpleton with the attention span of a demented gnat, but would you mind explaining everything in words of one syllable. 140 chars max.
#3
09-12-2019, 05:08 PM
 Guest Join Date: Aug 2012 Posts: 14,493
If I understand your question properly, the answer is going to depend quite a bit on your latitude. At / near the South Pole, one mile east is going to be quite a few time zones away. At the equator, not so much.

ETA: ninja'd, but I want extra credit for spelling latitude correctly.

Last edited by HurricaneDitka; 09-12-2019 at 05:09 PM.
#4
09-12-2019, 05:08 PM
 Guest Join Date: Aug 2001 Posts: 25,417
Wouldn't that depend on your latitude? Time, in the sense you're asking, is a function of the angle of arc you subtend on the surface of the globe, so 1 mile at thee equator would be different than one mile at, say, 45o north.
#5
09-12-2019, 05:12 PM
 Guest Join Date: May 2015 Location: 123 Fake Street Posts: 8,101
Quote:
 Originally Posted by HurricaneDitka If I understand your question properly, the answer is going to depend quite a bit on your latitude. At / near the South Pole, one mile east is going to be quite a few time zones away. At the equator, not so much. ETA: ninja'd, but I want extra credit for spelling latitude correctly.
I blame my phone. It should have caught my idiocy.
__________________
It may be because I'm a drooling simpleton with the attention span of a demented gnat, but would you mind explaining everything in words of one syllable. 140 chars max.
#6
09-12-2019, 05:15 PM
 Charter Member Join Date: Aug 2001 Posts: 16,450
I didn't even think about latitude.

I live in Dallas, but if using the equator makes it easier, we can go with that.
#7
09-12-2019, 05:15 PM
 Guest Join Date: Sep 2001 Location: Canada Posts: 2,118
Yes, it depends on your latitude. At the equator, the earth's circumference is not too far from 25000 miles. So there, one mile is roughly 1/1000 of an hour, so about 4 seconds. At 45 degrees, it's close to 17,500 miles. One mile would be about 1/750 of an hour, so about 5 seconds.
#8
09-12-2019, 05:18 PM
 Member Join Date: Mar 2002 Location: Trantor Posts: 13,042
What is your latitude? It is 4 minutes later for each degree of longitude. At the equator, a degree is approximately 25,000/360, nearly 70 miles. It comes to about 3.5 sec. But if you are at 45 degrees latitude, the length of a circle at the latitude is not 25,000 miles, but only the square root of 2 (cos 45) times that so that one mile east is nearly 5 seconds. Other latitudes will give other answers.
#9
09-12-2019, 05:21 PM
 Charter Member Join Date: Aug 2001 Posts: 16,450
You guys are great.

Thanks.
#10
09-12-2019, 05:21 PM
 SD Curator of Critters Moderator Join Date: Oct 2000 Location: Panama Posts: 43,088
The circumference of the Earth at the Equator is 24,901 miles. Since there are 86,400 seconds in a day, it will be 3.47 seconds later by sun time one mile east of you if you are on the Equator.

ETA: Ninja'd, but I gave more decimal places.

Last edited by Colibri; 09-12-2019 at 05:23 PM.
#11
09-12-2019, 05:24 PM
 Guest Join Date: Sep 2001 Location: Canada Posts: 2,118
Running the numbers for Dallas, I get 4.1 seconds, which seems about right, so hopefully I didn't do anything silly in the calculation.
#12
09-12-2019, 05:38 PM
 Guest Join Date: Apr 1999 Location: Foat Wuth! Posts: 5,306
Why do you want to know what time it is in Mesquite?
#13
09-12-2019, 06:39 PM
 A Rather Dubious Fellow Indeed Join Date: Jul 2003 Location: The Last Green Valley Posts: 375
Fun fact: If you're at 89° 59' 51.745'' N (give or take a few feet of latitude), then the time a mile east of you is ... the same as the time where you are.

Well, it was fun for me.
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Take care of yourselves, and those around you. -- Margo Timmins
#14
09-12-2019, 07:13 PM
 SD Curator of Critters Moderator Join Date: Oct 2000 Location: Panama Posts: 43,088
Quote:
 Originally Posted by mjmlabs Fun fact: If you're at 89° 59' 51.745'' N (give or take a few feet of latitude), then the time a mile east of you is ... the same as the time where you are. Well, it was fun for me.
What time is it, Yogi?

Yogi Berra: You mean now?
#15
09-12-2019, 08:40 PM
 Guest Join Date: Nov 2018 Location: Ohio Posts: 80
Quote:
 Originally Posted by Colibri What time is it, Yogi? Yogi Berra: You mean now?

Moe: Shemp, what does your watch say?

Shemp: Nothing, you got to look at it.
#16
09-12-2019, 10:16 PM
 Guest Join Date: Jul 2005 Location: N of Denver & S of Sanity Posts: 13,544
Tom Scott's take on a similar question.
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#17
09-13-2019, 07:01 AM
 Member Join Date: Jul 2009 Location: Rural Western PA Posts: 32,779
You're calculation must allow some latitude for the distance you are from the equator.
#18
09-13-2019, 07:10 AM
 Charter Member Join Date: Aug 2001 Posts: 16,450

So just to wrap my mind around this. Is a guy sitting at the equator spinning around on the planet faster than a guy siting in Alaska?
#19
09-13-2019, 07:22 AM
 Member Join Date: Jul 1999 Location: Chicagoland Posts: 2,240
If we want to nitpick, altitude affects the equation also because of gravitational time dilation. Hey, a millionth of a second here, a millionth of a second there; it adds up.
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"The greatest obstacle to discovery is not ignorance -- it is the illusion of knowledge."
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#20
09-13-2019, 07:34 AM
 Charter Member Join Date: Jun 2000 Location: St. Louis, MO 50mi. West Posts: 5,194
Quote:
 Originally Posted by Grrr! Thanks for the answers guys. So just to wrap my mind around this. Is a guy sitting at the equator spinning around on the planet faster than a guy siting in Alaska?
In relation to what?
#21
09-13-2019, 07:36 AM
 Guest Join Date: Jan 2008 Location: Off the Deep End Posts: 700
I came in to link that Tom Scott video but Saint Cad beat me to it.

Quote:
 Originally Posted by mjmlabs Well, it was fun for me.
Was it also fun when you shot the bear? What color was it?

Me too.
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That's my post. Hope you liked it!
#22
09-13-2019, 07:38 AM
 Guest Join Date: Jan 2003 Location: washington, dc Posts: 991
Quote:
 Originally Posted by Grrr! Thanks for the answers guys. So just to wrap my mind around this. Is a guy sitting at the equator spinning around on the planet faster than a guy siting in Alaska?
Yes.

That's not just an odd bit of trivia, The difference between the speed of rotation at the equator and the speed at higher latitudes drives much of the Earth's weather and ocean currents.

An overly simple explanation: A mass of air at the equator is moving at about 1000 mph (1600 km/hr). If it moves north it passes over land that is not rotating as quickly as that, so begins to move from west to east. Similarly, a mass of air from the north that expands southward will begin to move from east to west. Voila, the clockwise motion of a hurricane.
#23
09-13-2019, 07:42 AM
 Charter Member Join Date: Aug 2001 Posts: 16,450
Quote:
 Originally Posted by GaryM In relation to what?
Well, you got tow people that have traveled vastly different distances in the same 24hrs.

So one of them has to be going faster right? Or am I missing something?
#24
09-13-2019, 07:44 AM
 Charter Member Join Date: Aug 2001 Posts: 16,450
Quote:
 Originally Posted by zimaane Yes. That's not just an odd bit of trivia, The difference between the speed of rotation at the equator and the speed at higher latitudes drives much of the Earth's weather and ocean currents. An overly simple explanation: A mass of air at the equator is moving at about 1000 mph (1600 km/hr). If it moves north it passes over land that is not rotating as quickly as that, so begins to move from west to east. Similarly, a mass of air from the north that expands southward will begin to move from east to west. Voila, the clockwise motion of a hurricane.

Interesting. Thanks.
#25
09-13-2019, 07:48 AM
 Guest Join Date: Aug 2001 Posts: 25,417
Quote:
 Originally Posted by Grrr! Thanks for the answers guys. So just to wrap my mind around this. Is a guy sitting at the equator spinning around on the planet faster than a guy siting in Alaska?
First, let's ignore all the other ways that we're moving. The earth is moving around the sun, the solar system is moving around the galaxy, and the galaxy is part of an expanding universe. If you take all of that movement into account, then where you're standing on the earth's surface is a pretty minor issue.

But if we forget all of that, and just think about the earth as a closed system, then yes, the person at the equator has a linear speed, "through the air" as it were, that it faster than a person at 45o, who in turn has a liner speed faster than someone near the poles. The angular velocity is the same, because angular velocity is expressed as the number of degrees you move over a period of time (usually expressed in radians per second).

So all (stationary) people in different parts of the world have the same angular velocity, but very different linear speeds.
#26
09-13-2019, 08:11 AM
 Member Join Date: Aug 1999 Location: Great White North Posts: 4,677
Quote:
 Originally Posted by Grrr! Thanks for the answers guys. So just to wrap my mind around this. Is a guy sitting at the equator spinning around on the planet faster than a guy siting in Alaska?

Correct, in one 24 hr rotation a point on the equator travels ~1,674 kilometers per hour (1,040 mph) while near the poles is ~0.00008 kph (0.00005 mph).

Last edited by Sparky812; 09-13-2019 at 08:12 AM.
#27
09-13-2019, 08:13 AM
 Guest Join Date: Apr 2001 Location: Europe Posts: 5,982
Quote:
 Originally Posted by HurricaneDitka If I understand your question properly, the answer is going to depend quite a bit on your latitude. At / near the South Pole, one mile east is going to be quite a few time zones away.
At the South Pole, there is no east.
#28
09-13-2019, 11:08 AM
 Member Join Date: Aug 1999 Location: Great White North Posts: 4,677
Quote:
 Originally Posted by psychonaut At the South Pole, there is no east.

Sure, at the pole there is no east, west or south, only north... but he did say "near".

Last edited by Sparky812; 09-13-2019 at 11:09 AM.
#29
09-13-2019, 12:06 PM
 Voodoo Adult (Slight Return) Charter Member Join Date: Jul 2000 Location: Charlotte, NC, USA Posts: 26,569
nm

Last edited by KneadToKnow; 09-13-2019 at 12:07 PM.
#30
09-13-2019, 12:13 PM
 Guest Join Date: May 2016 Posts: 3,821
The South Pole is on New Zealand time, so you know when to get your breakfast in the cafeteria, and so forth. The sun does not rise and set like you are used to, though.
#31
09-13-2019, 02:04 PM
 A Rather Dubious Fellow Indeed Join Date: Jul 2003 Location: The Last Green Valley Posts: 375
Quote:
 Originally Posted by mhendo ... yes, the person at the equator has a linear speed, "through the air" as it were, that it faster than a person at 45o, who in turn has a liner [sic] speed faster than someone near the poles. The angular velocity is the same, because angular velocity is expressed as the number of degrees you move over a period of time (usually expressed in radians per second). So all (stationary) people in different parts of the world have the same angular velocity, but very different linear speeds.
... Which is one reason (of several) that NASA launches spacecraft from Florida (angled toward the east) and not from, say, Portland, ME, or Seattle. Every bit of escape velocity helps, and the Earth's rotation is free. (As in "free beer," not "degrees of freedom.")
#32
09-13-2019, 04:26 PM
 Guest Join Date: Jun 1999 Location: San Antonio, TX Posts: 5,570
Here's the breakdown in intervals of 10º latitude:

Lat
N/S Solar seconds 1 mile E/W
0 3.469675936 seconds
10 3.52320128 seconds
20 3.692352009 seconds
30 4.006436671 seconds
40 4.529340258 seconds
50 5.397857525 seconds
60 6.939351872 seconds
70 10.14465377 seconds
80 19.98106737 seconds
#33
09-14-2019, 12:07 AM
 Guest Join Date: May 2016 Posts: 3,821
Quote:
 Originally Posted by AWB Here's the breakdown in intervals of 10º latitude: Lat N/S Solar seconds 1 mile E/W 0 3.469675936 seconds 10 3.52320128 seconds 20 3.692352009 seconds 30 4.006436671 seconds 40 4.529340258 seconds 50 5.397857525 seconds 60 6.939351872 seconds 70 10.14465377 seconds 80 19.98106737 seconds
That is an awful lot of digits of precision there
#34
09-14-2019, 10:08 AM
 Guest Join Date: Jul 2018 Location: The City Different Posts: 130
Quote:
 Originally Posted by DPRK That is an awful lot of digits of precision there
The model geoid used by the United States National Geospatial-Intelligence Agency only has eight digits for the semi-major axis and thirteen digits for the semi-minor axis.
#35
09-14-2019, 11:15 AM
 Guest Join Date: May 2016 Posts: 3,821
Quote:
 Originally Posted by Ynnad The model geoid used by the United States National Geospatial-Intelligence Agency only has eight digits for the semi-major axis and thirteen digits for the semi-minor axis.
The rotation of the Earth, and therefore mean solar time, is nowhere near that regular, anyway.
#36
09-14-2019, 11:22 AM
 Guest Join Date: Dec 1999 Location: wilmington, ma Posts: 943
Quote:
 Originally Posted by zimaane ... Voila, the clockwise motion of a hurricane.
No, in the northern hemisphere, low pressure areas (e.g. hurricanes) rotate counterclockwise. High pressure systems rotate clockwise.

As for the OP: (A) At the equator, the earth rotates about 1520 feet per second. Elsewhere the speed is 1520 FPS times the cosine of the latitude (e.g. at JFK airport, the speed is 1520 * cos(40.64) = 1153 feet per second. (B) Nit Pick: there is no such time as 12pm. You probably mean 12 noon
#37
09-14-2019, 03:29 PM
 Guest Join Date: Jul 2019 Location: Various Posts: 290
Quote:
 Originally Posted by bizerta Nit Pick: there is no such time as 12pm. You probably mean 12 noon
Counter Pick: According to the latest US Government Printing Office Style Manual, 12 p.m. is a perfectly cromulent statement of time.

Last edited by ASL v2.0; 09-14-2019 at 03:31 PM. Reason: Update latest manual
#38
09-14-2019, 10:24 PM
 Guest Join Date: May 2016 Posts: 3,821
Quote:
 Originally Posted by ASL v2.0 Counter Pick: According to the latest US Government Printing Office Style Manual, 12 p.m. is a perfectly cromulent statement of time.
This has been discussed in various threads. "12 p.m." may be "cromulent" (??), but when is it? Since nobody really knows for sure- and there is no way the US Government Publications have been consistent on this- it is best to avoid such designations. Having said that, a 12-hour digital clock will switch from "a.m." To "p.m." at the moment of noon, so you will see 12:00 pm when you look at it.
#39
09-14-2019, 10:40 PM
 Guest Join Date: Jul 2019 Location: Various Posts: 290
Quote:
 Originally Posted by DPRK "12 p.m." may be "cromulent" (??)
Clearly, you need to embiggen your vocabulary.
#40
09-14-2019, 10:59 PM
 Charter Member Join Date: Apr 2003 Location: The far canal Posts: 12,698
Quote:
 Originally Posted by Colibri What time is it, Yogi? Yogi Berra: You mean now?

What time is it, Eccles?
#41
09-16-2019, 01:13 PM
 Guest Join Date: Oct 2018 Posts: 149
Oh, my, I'm so late to this thread...

1. OP, you're basically solving the problem of longitude.

Well actually, you're solving it backwards, but it takes the same math. There's a whole lot of books about it, I'd suggest reading "Longitude" by Dava Sobel. Nice little book. Was made into a BBC drama starring Jeremy Irons (!). Also see https://en.wikipedia.org/wiki/Longitude_(book)

The setup: Sailors at sea had always found it pretty easy to find their latitude with a sextant by just measuring the angle between a star (or planet, or even the sun) with the horizon, and your latitude, itself an angle, just pops out directly. Really simple. Notice, latitude just tells you how far north or south you are. But when you're navigating across the ocean, you really want to know your East-West numbers, and for that you need longitude. To solve for longitude, you need to know the exact time, and (yes) your latitude. And you need to measure angles of objects near your East or West horizons, such as morning or evening start (best measured at twilight, when you can still see the horizon).

So the story Longitude is really about the need to solve the problem, and how it was eventually solved mechanically, but a certain John Harrison, who made (for the time) phenomenally precise clocks. They compensated for different temperatures (which affect properties of the metal movements of the clocks), and had a devices that functioned as pendulums that were not affected by wave motion you feel when on board.

So back to my premise: Saying "what time is it, 1 mile east of me" is kind of equivalent to "20 seconds ago, the sun was at its zenith over me, and the time was 12:00. My latitude is X. So now, where is the sun at its zenith?" Answer: One mile to the East of you.

2. You're going faster the closer you are to the equator

As stated previously, yes. This is the reason why, for rocket launches we usually choose a launch site that is as close to the equator as possible! So, Florida, Texas, Guiana. Such flights already start moving in the right direction at a higher speed, so they take a little less fuel to reach orbit.

Last edited by Limmin; 09-16-2019 at 01:18 PM.
#42
09-16-2019, 01:23 PM
 Guest Join Date: Oct 2018 Posts: 149
past 5 minute error corrections...

>> morning or evening STARS not start

>> one mile to the WEST of you (since the sun moves from east to west).

It would be better to rephrase the problem to ask how fast does the sun move per minute at my latitude.
Then, one mile to the East of you it was overhead 20 seconds ago. So if it's noon here now, it's 12:00:20, one mile to the East of you.

Last edited by Limmin; 09-16-2019 at 01:25 PM.
#43
09-16-2019, 01:24 PM
 Guest Join Date: Mar 2002 Posts: 3,424
Quote:
 Originally Posted by Grrr! Thanks for the answers guys. So just to wrap my mind around this. Is a guy sitting at the equator spinning around on the planet faster than a guy siting in Alaska?
You obviously never read enough Calvin & Hobbes:

https://www.reddit.com/r/calvinandho...d_around_this/
#44
09-16-2019, 04:50 PM
 Guest Join Date: Jan 2003 Location: washington, dc Posts: 991
Quote:
 Originally Posted by bizerta No, in the northern hemisphere, low pressure areas (e.g. hurricanes) rotate counterclockwise. High pressure systems rotate clockwise. As for the OP: (A) At the equator, the earth rotates about 1520 feet per second. Elsewhere the speed is 1520 FPS times the cosine of the latitude (e.g. at JFK airport, the speed is 1520 * cos(40.64) = 1153 feet per second. (B) Nit Pick: there is no such time as 12pm. You probably mean 12 noon
You are right, thanks for the correction.
#45
09-17-2019, 01:48 AM
 Guest Join Date: Aug 2012 Posts: 284
Quote:
 Originally Posted by DPRK The South Pole is on New Zealand time, so you know when to get your breakfast in the cafeteria, and so forth. The sun does not rise and set like you are used to, though.
Now THIS is why I like coming here.
I never knew this little factoid.

It made me dig around a bit, and.. Surprise surprise, the North Pole has *NO* time zone.

How... symmetrical
#46
09-17-2019, 03:42 AM
 Charter Member Join Date: Jan 2000 Location: My own private Nogero Posts: 7,128
The South Pole, actually Amundsen-Scott Base, gets its supplies from NZ. Anyone going to or from the base goes through the same place (Christchurch, NZ). So it makes sense they'd keep the same time. If for some reason they were directly supplied from the US, say Los Angeles, they'd keep the same time as LA.

The North Pole has no base, so there's no reason it has or needs a time zone. Time zones are for the convenience of humans; the natural world doesn't need them.
#47
09-17-2019, 04:32 AM
 Guest Join Date: Jun 2000 Location: Floriduh Posts: 770
Quote:
 Originally Posted by zimaane Voila, the clockwise motion of a hurricane.
An earlier poster already corrected this, but to clarify, hurricanes spin counterclockwise in the Northern Hemisphere. They spin clockwise in the Southern Hemisphere.

https://www.scienceabc.com/nature/hu...is-effect.html
#48
09-17-2019, 08:56 AM
 Guest Join Date: Dec 2000 Location: temperate forest Posts: 7,172
Quote:
 Originally Posted by DPRK This has been discussed in various threads. "12 p.m." may be "cromulent" (??), but when is it? Since nobody really knows for sure- and there is no way the US Government Publications have been consistent on this- it is best to avoid such designations. Having said that, a 12-hour digital clock will switch from "a.m." To "p.m." at the moment of noon, so you will see 12:00 pm when you look at it.
I can see the remote possibility of confusion, but it seems to me that a moment's reflection would make it obvious that it's clearer and more logical for exactly 12:00 noon to have the same am/pm designation as 12:01 in the afternoon and 12:00:01 (including seconds) and 12:00:00 and 1 millisecond (all of which are clearly pm).

Does anyone seriously advocate that noon should be "12:00 am"?
#49
09-17-2019, 09:19 AM
 Guest Join Date: May 2012 Location: Slow-cala, Florida Posts: 24,533
If you're standing 3 feet from--and facing--the North Pole, east is to your right, so 1 mile east is 422 days in the future.

#50
09-17-2019, 09:57 AM
 Guest Join Date: May 2016 Posts: 3,821
Quote:
 Originally Posted by Quercus Does anyone seriously advocate that noon should be "12:00 am"?
According to the summary table on Wikipedia, the U.S. Government Publishing Office before 2008 (when they abruptly reversed themselves) and after some unspecified point (the 1953 guide recommends simply "noon" or "12 m."), and officially in Japan, as well as other miscellaneous users.

Last edited by DPRK; 09-17-2019 at 09:58 AM.

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