<p>Calculation of the <a href="https://rl.se/sub-solar-point" rel="noreferrer">subsolar point</a> is relatively straightforward. The actual point moves at nearly 500m/s in a circle, as the Earth spins. The linked website does the calculation in a few lines of python using a free library, The value is probably correct to within a few 10s of kilometres.</p>

<p>But you are looking for a different order of accuracy:  If you (for some reason) need 1cm accuracy, you would need to take into account the actual, non-spherical shape of the Earth. </p>

<p>The Earth is not a sphere, it can be better modelled as an oblate ellipsoid. But for 1cm accuracy, you would need to consider all of the mountains and hills. And you would need a very accurate time, not just a date. That is not a practical calculation. I can think of no practical application.</p>

CC BY-SA 3.0
2017-09-12T18:19:59.867Z
2017-09-12T18:19:59.867Z
James K
<p>Word choice is important.  It's easy to calculate to arbitrary <strong>precision</strong> but to arbitrary <strong>accuracy</strong>, not so much.  Aside from the shape of the Earth, defining a surface of the sun is difficult as well.</p>

<p><a href="https://i.sstatic.net/ytPl9.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ytPl9.gif" alt="precision vs. accuracy"></a></p>

CC BY-SA 3.0
2017-09-13T15:19:56.943Z
2017-09-13T15:19:56.943Z
Carl Witthoft
<p>Can we, with arbitrary precision, calculate what's the place on earth that's closest to the sun on a given date? If so, what's the math like? Say, if I wanted to calculate this within 1m, 10cm or 1cm precision, what exactly should I take into account?</p>

<the-sun><earth><distances><time>
Can we, with arbitrary precision, calculate what's the place on earth that's closest to the sun on a given day?
Carlos Vergara
# Can we, with arbitrary precision, calculate what's the place on earth that's closest to the sun on a given day?

(Asked by: username_0 on 2017-09-12)

Can we, with arbitrary precision, calculate what's the place on earth that's closest to the sun on a given date? If so, what's the math like? Say, if I wanted to calculate this within 1m, 10cm or 1cm precision, what exactly should I take into account?

**Tags:** the-sun, earth, distances, time

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## 2 answers

### Answer by username_1 on 2017-09-12. Score: 6

Calculation of the [subsolar point](https://rl.se/sub-solar-point) is relatively straightforward. The actual point moves at nearly 500m/s in a circle, as the Earth spins. The linked website does the calculation in a few lines of python using a free library, The value is probably correct to within a few 10s of kilometres.

But you are looking for a different order of accuracy: If you (for some reason) need 1cm accuracy, you would need to take into account the actual, non-spherical shape of the Earth.

The Earth is not a sphere, it can be better modelled as an oblate ellipsoid. But for 1cm accuracy, you would need to consider all of the mountains and hills. And you would need a very accurate time, not just a date. That is not a practical calculation. I can think of no practical application.


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### Answer by username_2 on 2017-09-13. Score: 0

Word choice is important. It's easy to calculate to arbitrary **precision** but to arbitrary **accuracy**, not so much. Aside from the shape of the Earth, defining a surface of the sun is difficult as well.

[![precision vs. accuracy](https://i.sstatic.net/ytPl9.gif)](https://i.sstatic.net/ytPl9.gif)


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