Universe Size Comparison Game: Scale of the Universe

How to play

1. Two objects appear side by side (stacked on a phone). The first shows its size and the dimension it measures, such as height, length or diameter; the second keeps its value hidden.
2. Decide whether the second one is larger or smaller and press Larger or Smaller.
3. The hidden value counts up and your answer is judged. When you are right, the second card moves across and a new one takes its place.
4. One wrong answer ends the run. There is no timer, and values stay fixed for the whole run. Pictures are not to scale, so compare the sizes written on the cards. Objects within 10% of each other are never paired.
5. Your result is saved in this browser. Once enough people have played a game, the results also show how your score ranks, and you can copy or share an image of your result, or replay.

Understanding the comparison

Compare the stated dimension rather than the apparent image size. Convert units when needed: a micrometre is one thousandth of a millimetre. A length, a height, and a diameter describe different measurements.

From a proton to the observable universe

The 69 objects in this game span about 42 orders of magnitude: the observable universe is roughly 10 to the power of 42 times the size of a proton. Each order of magnitude is a factor of ten, so a scale this wide only makes sense on a logarithmic ruler, where every step multiplies the size by ten instead of adding to it.

On that ruler a person (~1.75 m) sits about 15 orders of magnitude above a proton and about 27 below the observable universe. The midpoint of the whole range is about 1,200 km, and the object closest to it in the game is Ceres (940 km).

How the sizes are measured

Every card names the dimension it compares. Buildings and people are measured by height, ships, aircraft and many animals by length, and planets by their equatorial diameter, excluding rings.

Very small and very large objects have no sharp edge. A proton’s size is a charge radius rather than a hard surface, a star’s diameter depends on the model used, and nebulae and galaxies are given by their approximate extent. The largest sizes are given in light-years: one light-year, the distance light travels in a year, is about 9.46 trillion kilometres.

Measurements come from NASA, NIST, museums and the primary source linked for each object in the game’s credits, with photographs, micrographs, telescope images and visualizations labelled on each card.

Sources

Source: NASA and per-object references

A curated size collection, not one statistical series. Each object specifies a dimension and links its reference in How to Play. Representative sizes, estimates and bounds are identified there; pictures are not to scale.

• NASA and per-object references