The Scale of the Universe

The size of the universe is incomprehensible by humans. One of the most fascinating experiences was playing around with the scale of the universe app made by Cary Huang. Seeing just how huge the Milky Way galaxy is made me feel small. I knew it was big, but not like that. Although, that app still does not convey the tremendous distances between objects in space. In this post, I will compile a list of the most interesting analogies and comparisons that help us understand just how big the universe is.

An image of the globular cluster NGC 6397, taken by the Hubble Telescope. This cluster formed 13.5 billion years ago and is one of the first clusters that has formed after the Big Bang. Credit: NASA.

Firstly, let’s start with something closer to home. This analogy was first brought into my attention by Vsauce. The International Space Station orbits 400km above the Earth’s surface, which is about the distance from New York to Vermont. Yet, if we take our planet to be a peach, the ISS would still be skimming the fuzz. Also, if you thought the sky was crowded with asteroids, try putting 5000 people in random places and make them find each other.

Now for the solar system. If you imagine that the Earth is the size of a baseball on the homeplate of Nationals stadium in Washington D.C., Mars would be a block away from the fence. The edge of the solar system, the oort cloud, would be a halfway on the way to the Moon! The nearest star, Alpha Centauri, would be a little bit past the Moon’s orbit. I think we are starting to lose a sense of scale again, but how can you not. Remember, we started with a baseball for Earth. Feel free to make your own analogy. The user incoming on the nasaspaceflight forum suggests that the easiest way to do this is using a spreadsheet and picking an initial real life object to compare the size of Earth to.

Another one of my favourites is the toilet paper solar system. Try unrolling a roll of toilet paper and put the Sun on the first square. Mercury will be on the 3rd square, Venus on the 5th, Earth on the 7th, and Mars on the 11th. Now, time for a leap. Jupiter will be on the 39th, Saturn on the 72nd, Uranus on the 144th, and finally Neptune on the 225th. This really shows the astronomical (heh) difference in distance between the terrestrial planets and the gas giants. This is apparently a school activity for elementary school students, so if you want to try this with your younger siblings, it would be a wonderful learning experience for both of you.

An example toilet paper solar system. Credit:

One of the earliest examples of these size comparisons is the 1977 film Powers of Ten. It begins at a picnic in Chicago and zooms out all the way to billions of galaxies, and then zooms back in to the inside of a cell. The grainy quality makes the experience eerie and the score allows for a thoughtful reflection. Also, check out this beautiful diagram that compares gravitational wells made by different objects. Not only does it act as a size comparison of some of the planets, but also teaches the reader about gravitational wells and general relativity.

The comparison of gravitational wells. Credit: xkcd.

If you want to know more, check out this excellent size comparison of the universe video from Harry Evett. Also, if you have a powerful enough computer, I recommend playing Universe Sandbox. It’s a blast, which teaches you about our solar system and the properties of planets. I’ve been playing it for the last couple months, and in addition to blowing things up with sand grains travelling at the speed of light, I now understand how our solar system moves in the galaxy. Take a look at the steam page. Furthermore, the Charleston Lake Astronomical website provides a few additional analogies that you might find insightful. Take care!


Emspak, J. (2016, June 2). Does the Universe Have an Edge? Livescience.Com.

Episode 11: Toilet Roll Solar System. (n.d.). Institute of Physics.

Melina, R. (2017, August 4). International Space Station: By the Numbers. Space.Com.

Popova, M. (2017, March 29). Five Visualizations to Grasp the Scale of the Universe. The Marginalian.

The Scale of the Universe. (n.d.). Charleston Lake Astronomical.

Published by Mateusz Ratman

High school student from Warsaw, Poland. JHU Class of 2026.

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