Get closer to the Moon without leaving the Earth

"Close to the Moon, but not as close as I can be" - Astronomy Koan by Daniel Cummings
Astronomy Koan by Daniel Cummings

How close can I get to the Moon while still staying on the Earth’s surface?

I frame this as a sort of astronomy poem I call an Astronomy Koan. These are short sayings that contain astronomy puzzles. The answers to these puzzles carry insights into physical astronomy concepts.

Guy Ottewell has posted an article at about getting close to the Moon.

“I am close the the Moon but not as close as I can be.” This Astronomy Koan invites the reader to consider all of the ways which an Earth-bound observer might get as close to the Moon as humanly possible – without leaving the surface of the Earth.

The Earth and Moon are moving, I am moving

The Moon and the Earth are two oblate spheroids interacting in complex ways.

The Earth-bound observer is able to move around on the surface of the Earth while we calculate the “closest” point of the Moon to be the surface point that is closest to a surface point on Earth.

The goal of the Earth-bound observer is to find the location and time where they will be physically closest to the Moon.

Motions of the Moon that bring the Moon closer and further to your “closest personal point”

  • Daily apparent revolution – every 24h 50m wherever we are on the Earth surface, the Moon transits (crosses the meridian) and reaches the “closest personal point” at that time. 
  • The apsides of the Moon’s orbit – the Moon’s orbit is slightly elliptical and has an apogee (furthest point from Earth) and a perigee (closest point to Earth). If a perigee coincides with a Moon transit, this brings the Moon even closer to the surface of the Earth. Approximately 357000km (perigee) and 406000km (apogee)
  • The inclined orbital track of the Moon. Close to the ecliptic, but an additional 5 degrees offset, this gives the Moon an opportunity to be closest to people located on the surface of the Earth who are slightly north (up to 5.14 degrees) of the Tropic of Cancer and south of the Tropic of Capricorn.
  • The Moon’s orbit is slowly moving away from the Earth (by 3.8cm per year, about 38km in 1million years) – so the longer you wait, the further away it will be!
  • Surface of the Moon orientation toward my location – East-west libration moves the “orientation” of the Moon as it relates to the Earth
  • The surface of the Moon has crater walls and valleys. The closest point would be at the height of a crater wall or central peak. Hipparchus crater or Triesnecker crater seem like likely candidates because they are “central”, but this is beyond my understanding of the topology of the Moon surface and how it might interact with the orientation changes caused by libration, nutation, and the inclined orbit.

My motions on the Earth that can get me closer to the Moon

  • The transit can be made closer by moving closer on the surface of the Earth to the current declination of the Moon. Generally speaking, that involves going toward the equator, but it get complicated by the fact that the orbit is inclined to the equator and ecliptic.
  • The transit can be made closer by going to a higher elevation 
  • The transit can be made closer by going to the top of a mountain close to the equator (Mt. Chimborazo as opposed to a tall mountain like Everest that is not near the Equator)

The “ideal” situation that would bring a human on the surface of the Earth as close as can be to the Moon would be

Stand at the top of Mt. Chimborazo, at the moment of Moon transit, at the exact orbital perigee, with Hipparchus crater wall oriented toward Mt. Chimborazo, as soon as possible!


We looked at all of the ways that the Earth and Moon approach and recede from each other. The goal is to understand more directly when I am close to the Moon and observe the motions that change that distance.

Please let me know if I have missed anything here! Add in comments below.


NASA Moon page: – has “an animated diagram of the subsolar and sub-Earth points for 2023” Indicates the general sweep of the “closest Moon-Earth point” as it traces out irregular shapes on the surface of the Moon.

NOAA answers a question about the “tallest” mountain, Mt. Chimborazo:

ASC page with information about the various motions of the Moon:

Wikipedia Orbit of the Moon article:

Wikipedia Lunar Distance (measure the distance from the center of the Earth to the center of the Moon):

Moon orbit distance growing:

Quora Answer that mentions Mt. Chimborazo:

GPS uses Quasars

GPS uses Quasars to work

GPS uses quasars to get its own position
GPS satellite in low Earth orbit. Credit: NASA artist’s impression
The Global Positioning System (GPS) is precise.

That precision originates in a mind-blowing place!

GPS signals tell billions of people where they are each day.

GPS helps pilots land planes and captains steer ships.

GPS signals stamp locations onto millions of photos per minute.

GPS gives you driving directions.

But, where does GPS get its own GPS?

The GPS for GPS

How does GPS know where a GPS satellite is?Click here to continue reading…

Stellarium – Find the Humanity Star

A new satellite called the Humanity Star looks like a disco ball

Update Apr. 1, 2018.

The Humanity Star is no longer an active satellite – it has fallen out of the sky:

However, even though the Humanity Star is now gone, this article still teaches you how to load satellites into Stellarium. So, read on for a quick tutorial on how to track any satellite in Stellarium.

Looking for information on how to track the Humanity Star any satellite location using Stellarium astronomy software?

Here is a quick tutorial on how to find the Humanity Star any satellite using Stellarium.

You can track the position of the Humanity Star with Stellarium
The Humanity Star satellite before launch – still on the Earth.

Rocket Lab founder and CEO Peter Beck announced that the company’s rocket had placed a special satellite in a 90 minute orbit around the Earth.

A lot of people want to see this new “star” in the sky. Stellarium can help you do that.

If you don’t have Stellarium, you can download a copy here. And I have a few tutorials that can help you get started with this amazing piece of software.Click here to continue reading…