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:

How Fast is the Earth Moving? – A Quiz

A family views the visible orbit path of the earth.
A family views the visible orbit path of the earth.

“How fast?” means “What is our velocity?” Velocity is a speed combined with a direction. We can figure out our speed and our direction on the Earth by looking at these 6 motions and directions…

But, before you read these, try to think of the 6 different motions that the Earth has.

Just putting some space in here to give you time to think about the Quiz.


The answer:

  1. Rotation of Earth (cycle) – 0.5 km/sec
  2. Orbit around Sun (cycle) – 30 km/sec
  3. Solar System through Galaxy (cycle) – 200 km/sec
  4. Milky Way Galaxy moving toward Andromeda within the Local Group (non-cyclical toward Andromeda)- 109 km/sec
  5. Local Group motion inside Virgo Supercluster (non-cyclical toward “overdense” regions) – 300 km/sec
  6. Cosmic Void repulsion (non-cyclical) – 600 km/sec

Earth’s Overall motion = 368 km/sec +/- 30 km/sec depending on season

Our overall direction of motion? The Cosmic Microwave Background (CMB) tells us generally which direction we are moving in: towards the “overdense” regions of the Cosmic Void.


Thanks for Ethan Seigel for gathering all the relevant data points for this quiz.

How many stars are in the sky? A Quiz

Have you ever looked up and wondered how many stars are in the sky?

This person is wondering how many stars are visible in the sky right now.
How many stars are in the sky right now?

It’s a simple question with a surprising answer!

This question has layers of answers – the most common answer is “it depends” – it depends on where you are, what part of the year it is, what time it is, and most of all… how dark are your skies and how powerful is your telescope? 

Let’s start with a quick (approximate) list of how many stars you might be able to see at once at night under “normal” conditions with no telescope. (The details on these calculations are near the end of this article.)

How many stars can I see at night:

  • The most stars anyone can see from the Earth (no telescope): 3700
  • The number of stars can you see at a dark sky site: 2000
  • How many stars can I see in my suburban yard: 200
  • How many stars can I see in a large city: 20

Another trick answer to “how many stars are in the sky?” is: “all of them!” All of them are in the sky, but they are just not visible to you “right now” for one reason or another.

I know, these answers are not quite what you may be looking for. Let’s look a little bit deeper by starting our search for how many stars can I see at night.

Quiz – How many stars are in the sky, how well do you know them?

Let’s start by taking a short quiz (answers are just a scroll away, so don’t peek!):

  1. Which star is the brightest in the sky?
  2. Which star is the closest to us?
  3. Which star is the first one discovered to have a planet supporting life?
  4. Which stars have a solar system?

Scroll down a bit to see the answers to this first part of the quiz.

While we are waiting to scroll (and to keep the peekers from peeking!)… let’s talk a little bit about how professional astronomers count the stars.

Annie Jump Cannon – Harvard star counter extraordinaire

Astronomer Annie Jump Cannon found a lot of stars and classified them
Annie Jump Cannon – Harvard University Image: Public Domain

Have you ever tried to count the stars? If you have, you probably gave up at some point because there were too many to keep track of.

In the early 1900s there was a tenacious Harvard astronomer named Annie Jump Cannon who didn’t give up counting! In fact, she counted so many stars that she almost lost track.

To keep everything organized she started categorizing them by their colors. She invented the spectral classification system – O,B,A,F,G,K,M – and personally classified over 350,000 stars!

Her method of categorizing stars is still in use today.

The answers to the star Quiz

The Sun is one of many stars. Proxima Centauri, Sirius, Arturus and Rigel are shown in a size comparison.
The Sun compared to other stars. Image: Daniel Cummings

The number of stars in the sky is…

SPOILER ALERT! – Here are the answers to the quiz above! 

The quiz is a trick quiz because the answers to are all “the Sun.” If we don’t include the Sun in this quiz then we get very different answers and the answers are:

  1. Sirius is the brightest star (it is almost as bright as Jupiter),
  2. Proxima Centauri is the closest star (it is 4.22 light years away),
  3. No star’s exoplanets have yet been proven to support life – the Sun is the only star so far to host life.
  4. There is only one solar system. The answer to question 4 is truly a trick question: “No other stars have a solar system… because only one star is named “Sol” … the Sun! The “Solar System” is named after Sol – the Sun. See: Sol+ar = Solar. Other stars would have planetary systems named after the star. For instance, there may be a “Sirius-ar system” that hosts a planet like Earth.

The Known Universe

Ok, now you are done with the quiz let’s get counting stars. Go outside, look up, start counting!

How many stars are in this picture? We may never know since the know universe keeps growing
Artist’s conception of the known universe. Credit: Pablo Carlos Budassi via Wikipedia

Before, we start… There is one tiny problem with counting the number of stars. Even with the best tools humans have invented, we can only see a small part of the universe. Astronomers call this the “known universe” and it stretches about 14 billion years back through time in one direction, and (we assume) 14 billion years back in another direction.

Ten sextillion stars in the known universe

Astronomers have estimated the number of stars in the Milky Way galaxy as one hundred billion (this is a low estimate by the way). The Milky Way is an average galaxy. Astronomers estimate that there are one hundred billion galaxies in the known universe (another low estimate). The math to figure out the total number of stars in the universe is as simple as the result is mind-boggling!

100,000,000,000 (one hundred billion – 11 zeros) x 100,000,000,000 (one hundred billion – another 11 zeros) = 10,000,000,000,000,000,000,000 (ten sextillion – 22 zeros)

Counting to one million is not like Counting to one billion

A million is way, way smaller than a billion.

It would take 11 days to count to one million if you counted one number per second without doing anything else. Counting to a billion at the same pace (one per second) would take you 32 years of continuous counting!

Count to 1 million at a rate of 1 per second = 11 days
Count to 1 billion = 32 years

– Arithmetic

If you counted all the stars in the Milky Way at the rate of one per second, it would take you about 3200 years to finish counting our one galaxy’s set of stars.

How many stars in my sky now?

Ok. So, let’s get real. Now we know how many stars there may be in the entire known universe, let’s narrow the question. 

Here is how we will narrow the question. Let’s create a set of ideal conditions that will guarantee we see as many stars as possible.

This is the set of almost ideal seeing conditions. This set of conditions would guarantee seeing the most number of stars that anyone could ever see with the naked eye:

I am on a tall mountain top with no trees looking up at the perfectly clear and calm sky right now. It is midnight. I can now see approximately half the stars in the sky. These near perfect seeing conditions make it so that I can see stars to magnitude 6 with my 20/20 vision.

Number of stars in the sky I see

According to David Haworth of there are approximately 7400 magnitude 6 or brighter stars. Remember, we can only see half the sky at any time. So, cutting 7400 in half we get 3700 stars. 3700 stars is the greatest number of stars that any earth-bound human can ever see at any one moment without a telescope or other aides.

Stars in my sky right now

Now we know how many stars you might ever see at once, let’s look at how most people see the sky.

Most people cannot see 3700 stars because of serious light pollution, horizons full of trees and landforms, and atmosphere, lots of watery, moving atmosphere floating above us.

If you are lucky and go camping in a dark sky area you might be able to see about 2000 stars on a good night.

In a typical, light-polluted suburban sky you can see approximately 200-300 stars.

In the middle of a big city the number of stars goes down to about 12 to 20.

12 Stars.

12. That’s not a lot of stars. Maybe take a trip out of the city to see the stars?


You can see 3700 stars under perfect viewing conditions.

You can see about 2000 under excellent dark skies.

You can see about 300 stars in the suburbs.

You can see 12 stars under bright city lights.

References for how many stars – David Haworth compiled data on the number of stars at each magnitude and presented it in a nice table.

Sky and Telescope article – covers skyglow, light measuring technology, light maps, NELM and more. Authoritative. article – how astronomers estimate the number of stars in the Milky Way.

National Geographic Kids – Mini article on light pollution with estimates on how many stars are visible from different places.

Quiz – Can we see the Sun at midnight? Where is the Sun?

Can we see the Sun at midnight?

Yes. We can see the Sun at midnight. But, only if we are at one of the polar regions during the Summer season.

A quiz – seeing the Sun at midnight – don’t scroll til you try to answer!

When you see the Sun “rising” in the morning at dawn you are facing the east.

When you see the Sun “setting” at the end of the day you are facing the west.

Assuming you are not above the Arctic circle and not too close to the equator… if you could look right at the Sun (when the night is exactly half over) – by looking through the Earth – which cardinal direction would you be facing? East, West, North, or South?

Looking north or south to see the Sun at midnight?
A compass rose showing the cardinal directions.

Click here to continue reading…