Submitted by squidwards_noze t3_127vtaj in explainlikeimfive
squidwards_noze OP t1_jeg20h6 wrote
Reply to comment by RhinoG91 in ELI5: Is there a time difference everywhere? by squidwards_noze
Okay so what you’re saying is there are indeed subtle differences and Northern California would have a tiny bit different time, but we just don’t acknowledge it?
SpiralSuitcase t1_jeg321s wrote
Yes, because Time Zones basically came around with the advent of the railroad. It was important that everybody agree on what time it is, otherwise it would be impossible to plan anything. The earth spins at a constant rate, meaning that the sun goes across the sky at a constant rate. It would just be completely impossible AND useless to split the entire world into, say, 1-minute time zones.
schoolme_straying t1_jeg658f wrote
> The earth spins at a constant rate,
Constant-ish rate.
Great American Gladys West developed her model of the world to take into account variations in the earth's spin to ensure that sat nav is accurate.
SpiralSuitcase t1_jeg7x0s wrote
How much does the rotation of the earth vary, and is it significant enough to warrant this detour in an explanation to a 5-year-old?
schoolme_straying t1_jegno5c wrote
> How much does the rotation of the earth vary, and is it significant enough to warrant this detour in an explanation to a 5-year-old?
ELI5 is not for actual 5 year olds. It's for an intelligent layperson.
Day length fluctuations explains all in a depth that is beyond me.
When I went with my son to Greenwich observatory on the River Thames, London.
We looked at our GPS co-ordinates we found that the zero meridian was 100m or so further east than the observatory. This was explained as being caused by the earth slowing more than anticipate and so the 0° meridian moves further east.
Every so often there is a leap second when this occurs the GPS data resets the zero meridian back to the observatory
SpiralSuitcase t1_jegp2uc wrote
So answer the question I was obviously asking.
schoolme_straying t1_jegruqf wrote
Not sure exactly what you are asking - could you rephrase it for me?
SpiralSuitcase t1_jegtvpw wrote
You explained that ELI5 isn't literal. But I was clearly asking if the clarification you're making is necessary within this kind of explanation. Was my technical inaccuracy negatively impacting the explanation I gave in any way?
schoolme_straying t1_jegvrxz wrote
We're that far down in the weeds nobody is interested in our conversation
I think the idea that the time the earth takes to rotate 360° varies and is thus not constant is important and it has consequences that are verifiable to anyone with a mobile phone and GPS.
In terms of science etc I think the idea of a constant should only be used for things that do not change. IE π e and the speed of light in a vacuum.
Obviously I thought it was important or I wouldn't have mentioned it.
As a distraction here's a man in the 1970s with a GPS wondering about the implications of a better organised society
SpiralSuitcase t1_jegvypo wrote
Your response was to my TOP LEVEL COMMENT.
But I also want to make it clear that I am also part of the nobody that is interested in this conversation.
ETA: actually, that wasn't clear at all. I am not interested in this conversation and I think your correction is absolutely unnecessary.
schoolme_straying t1_jegx62f wrote
I thought my comment was warranted. You didn't. Fine. Good people may agree to differ.
[deleted] t1_jeg8elh wrote
[removed]
li_grenadier t1_jeg5m91 wrote
You keep saying things like "tiny bit different time." No, the clock on the eastern edge of the time zone is the same as the clock on the western edge. If it is 12:30 PM in the Eastern US time zone, it's not 12:05 in Indiana, 12:30 in Pennsylvania, and 12:55 in Maine. It's 12:30 across the whole time zone. That's sort of the whole point of having the time zones in the first place: to sync everyone up in that area, while still allowing everyone to hit "noon" roughly when the sun is overhead in their own area.
When you cross into Central, the clock will read 11:30. So in that sense, yes, the time is an hour different just because you cross that magic border line.
I think what you are really after though is whether or not the sun is in a different position, and the answer to that is yes. Lookup sunrise/sunset times in various cities in the same time zone, and you'll see they vary slightly. So again, in the eastern time zone, sunrise today in Indianapolis was 7:30 am, in Pittsburgh it was 7:05 am, and in Boston it was 6:28 am. All of them hit 7:30 AM at the same time, but the sun position in the sky can vary across the same time zone.
RhinoG91 t1_jeg3nbo wrote
What? How did you come up with that?
No, the only difference is the position of the sun at any given instance in time. Google midnight sun or 24 hour darkness.
When it’s noon in one time zone, it’s noon everywhere in that time zone. Latitude has little bearing on the time. Our timekeeping is just to maintain a standard. Call someone in NorCal at noon and they’ll say it’s noon. Not 12:01. The sun would be lower in the sky compared to socal due to earth’s curvature, but “standard time” is just an agreed upon construct so we can all be harmonized.
Selfless- t1_jeg77g0 wrote
With Daylight Savings, noon is now at 1:00pm, since we all decided to call what’s actually 11:00am 12.
squidwards_noze OP t1_jeg3v6d wrote
Would the different position of the sun not indicate a slight, but unacknowledged difference of time?
frustrated_staff t1_jeg5rxr wrote
Only East to West. Not North to South. North to South only changes the height of the sun in the sky, not the amount of time it takes to pass through its path.
Antithesys t1_jeg557e wrote
> so what you’re saying is there are indeed subtle differences and Northern California would have a tiny bit different time, but we just don’t acknowledge it?
Not really. The subtle difference between nearby places is in when the sun (and other things in the sky) rises and sets. There is no objective "time" at which these events occur. It's determined by the local horizon.
Muslims need to keep track of the sunset for fasting reasons. They are advised that if they happen to be at the top of the Burj Khalifa, they should remember that the sun sets three minutes later at the top of the tower than at the bottom. That doesn't mean it's "actually three minutes earlier" at the top of the tower. It's the same time as it is on the ground, it's just high up so the sun is above the horizon longer.
schoolme_straying t1_jeg77g8 wrote
I know that muslim scholars decided that muslims in space can track their day/night for fasting based on the time in Mecca.
frustrated_staff t1_jeg5jmu wrote
It's not that we don't acknowledge it, it's that we don't acknowledge it in our day-to-day lives because the difference is so small. Your talking femto-seconds or less between Northern and Southern California (due to acceleration and gravity and all that jazz).
If you're thinking time zones (which it seems like you are), those are artificial constructs designed to keep people in different parts of the world talking about time of day in the same terms (If I say it's 4pm, you have abpretty good idea that the sun is up and bright and there's yay-and-so-many hours until dusk, regardless of where I am).
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