<p>This is better suited for English Language &amp;Usage SE, but the word you're looking for is </p>

<h2>Isochron</h2>

<blockquote>
  <p>an imaginary line or a line on a chart connecting points at which an event occurs simultaneously or which represents the same time or time difference</p>
</blockquote>

<p>(Source: <a href="https://www.merriam-webster.com/dictionary/isochron" rel="nofollow noreferrer">Merriam-Webster</a>)</p>

<p>Isochrons are typically used in diagrams rather than maps, for techniques like rock dating, where correlating things by time is more important. </p>

<p>But cartographers are used to putting all types of <a href="http://wiki.gis.com/wiki/index.php/Isarithmic_map" rel="nofollow noreferrer">isarithm</a>s on maps, and would understand what an isochron was meant on a map.</p>

<p>The trick is to define "same time" as "same solar time", giving you the "moving meridian" you're looking for.</p>

<p>You could contrive a more specific term like <strong><em>isoheliochron</em></strong> but it hardly seems worth the effort, because they're pretty boring on a map.</p>

CC BY-SA 4.0
2019-09-25T21:27:11.460Z
@BarryCarter That would be a specific value, and in the rotating frame of reference OP is referring to, the longitude value changes. OP seems to be looking for some sort of invariant within the frame, and "isochron" appears to give enough abstraction to be useful.
Spencer
CC BY-SA 4.0
2019-09-24T01:07:47.793Z
2019-09-24T16:31:29.400Z
2019-09-24T16:31:29.400Z
Spencer
<p>Imagine a <a href="https://en.wikipedia.org/wiki/Meridian_(geography)" rel="nofollow noreferrer">meridian</a> that moves over the Earth's surface such that it remains at the longitude that corresponds to a particular solar time (e.g. midday). </p>

<p>This meridian would remain stationary relative to the Sun as the Earth revolves under it.</p>

<p>Is there a name for such a meridian?</p>

CC BY-SA 4.0
2019-09-23T12:51:52.180Z
This is an interesting question! I think that a [sun-synchronous orbit](https://en.wikipedia.org/wiki/Sun-synchronous_orbit)'s sub-satellite point would likely follow this meridian, whatever it might turn out to be called.
uhoh
CC BY-SA 4.0
2019-09-23T16:58:37.230Z
The only line I can think of is the [terminator](https://sos.noaa.gov/datasets/daynight-terminator-daily/), which is the line that separates day from night.
Fred
CC BY-SA 4.0
2019-09-24T00:37:20.757Z
solar noon is effectively that kind of meridian
haresfur
<terminology><earth-observation>
Is there a name for a "moving meridian" corresponding to particular solar time?
Museful
# Is there a name for a "moving meridian" corresponding to particular solar time?

(Asked by: username_0 on 2019-09-23)

Imagine a [meridian](https://en.wikipedia.org/wiki/Meridian_(geography)) that moves over the Earth's surface such that it remains at the longitude that corresponds to a particular solar time (e.g. midday).

This meridian would remain stationary relative to the Sun as the Earth revolves under it.

Is there a name for such a meridian?

**Tags:** terminology, earth-observation

> **Comments:**
> **username_1**: This is an interesting question! I think that a [sun-synchronous orbit](https://en.wikipedia.org/wiki/Sun-synchronous_orbit)'s sub-satellite point would likely follow this meridian, whatever it might turn out to be called.  
> **username_2**: The only line I can think of is the [terminator](https://sos.noaa.gov/datasets/daynight-terminator-daily/), which is the line that separates day from night.  
> **username_3**: solar noon is effectively that kind of meridian  

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## 1 answers

### Answer by username_4 on 2019-09-24. Score: 3 | Accepted answer

This is better suited for English Language &Usage SE, but the word you're looking for is

## Isochron

> an imaginary line or a line on a chart connecting points at which an event occurs simultaneously or which represents the same time or time difference

(Source: [Merriam-Webster](https://www.merriam-webster.com/dictionary/isochron))

Isochrons are typically used in diagrams rather than maps, for techniques like rock dating, where correlating things by time is more important.

But cartographers are used to putting all types of [isarithm](http://wiki.gis.com/wiki/index.php/Isarithmic_map)s on maps, and would understand what an isochron was meant on a map.

The trick is to define "same time" as "same solar time", giving you the "moving meridian" you're looking for.

You could contrive a more specific term like ***isoheliochron*** but it hardly seems worth the effort, because they're pretty boring on a map.

> **Comments:**
> **username_4**: @BarryCarter That would be a specific value, and in the rotating frame of reference OP is referring to, the longitude value changes. OP seems to be looking for some sort of invariant within the frame, and "isochron" appears to give enough abstraction to be useful.  

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