<p>You have 2 separate concepts here. The length of a day and a year are unconnected with how you measure seconds, minutes and hours.</p>

<ul>
<li><p>The length of a day is defined as how long it takes for the planet to rotate on its axis, and a year is how long it takes to orbit its primary.</p></li>
<li><p>Seconds, minutes and hours are a measurement chosen by us back in history, and chances are we will still use the same wherever we go in the universe. The way we measure it is designed to let us always measure seconds consistently. </p></li>
</ul>

<p>Even on Earth, we say that a day is 24 hours, but it isn't really, as the two sets of concepts don't match up. We haven't defined a second as a fraction of the time it takes the planet to rotate - it is defined based on physical constants. So if you were to say that Gliesa has a day that is 30 units long - it would be astonishing if those units were exactly hours!</p>

CC BY-SA 3.0
2014-08-18T09:57:08.610Z
2014-08-18T09:57:08.610Z
Rory Alsop
<p>we measure time based on earth and earth mass\gravity plays a role in the measurement ? so how and what would be time if not earth time on other exo planets since they will be having different mass/gravity and probably more variables affecting time measurement.</p>

<p>I can say Gliesa has a day of 30 hrs(assumed) , </p>

<p>So will the length of second, minute and hour, likeewise day or month will fall under its own time system?</p>

CC BY-SA 3.0
2014-08-18T10:52:45.430Z
its weird when I click the Quora link in email it opens stackexchange..
Ciasto piekarz
<earth><exoplanet><space-time>
the length of second, minute or hour, what defines the time of exo planetary bodies
Ciasto piekarz
# the length of second, minute or hour, what defines the time of exo planetary bodies

(Asked by: username_0 on 2014-08-18)

we measure time based on earth and earth mass\gravity plays a role in the measurement ? so how and what would be time if not earth time on other exo planets since they will be having different mass/gravity and probably more variables affecting time measurement.

I can say Gliesa has a day of 30 hrs(assumed) ,

So will the length of second, minute and hour, likeewise day or month will fall under its own time system?

**Tags:** earth, exoplanet, space-time

> **Comments:**
> **username_0**: its weird when I click the Quora link in email it opens stackexchange..  

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## 1 answers

### Answer by username_1 on 2014-08-18. Score: 3

You have 2 separate concepts here. The length of a day and a year are unconnected with how you measure seconds, minutes and hours.

* The length of a day is defined as how long it takes for the planet to rotate on its axis, and a year is how long it takes to orbit its primary.
* Seconds, minutes and hours are a measurement chosen by us back in history, and chances are we will still use the same wherever we go in the universe. The way we measure it is designed to let us always measure seconds consistently.

Even on Earth, we say that a day is 24 hours, but it isn't really, as the two sets of concepts don't match up. We haven't defined a second as a fraction of the time it takes the planet to rotate - it is defined based on physical constants. So if you were to say that Gliesa has a day that is 30 units long - it would be astonishing if those units were exactly hours!


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