You could set the moon on fire

Citizen Science App How the moon deceives us

Everyone has fallen for this illusion: It looks impressively large in the sky, and when we photograph it, it is a little more imposing point: the moon. What annoys us, leisure moon gazers, fascinates people in science, for example Professor Claus-Christian Carbon from the University of Bamberg. Carbon is a perception psychologist and researches this effect. For him, the moon illusion is one of the most impressive demonstrations for human perception:

If you look through a small perforated disk, the moon is always terribly small, a tiny little point of light.

Claus-Christian Carbon, Perception Psychology

The fact that the moon sometimes seems so big when we look at the sky is a fallacy, says the scientist: "We use our brain to process this signal so strongly that it sometimes no longer corresponds to reality. That means: some things are strengthened, enlarged, some things are made smaller because they are not that important at the moment. " Just why

How is the moon illusion explained so far?

Most people think that the deception is related to the respective distance from the earth, knows Claus-Christian Carbon. From the point of view of the psychologist, however, the perceptual effect, i.e. the effect that perception itself plays here, is significantly stronger: "We are talking about a multiple of the astronomical and optical effects." It's easy to understand, he says, if we pay attention to how the moon mutates from a true giant to a relatively tiny-looking celestial body within a few minutes. He usually looks particularly small high up or in the zenith. Very impressive, on the other hand, on the horizon. Either way, the moon looks much bigger than it should actually appear.

Another explanation that is often put forward: "Sometimes the light breaks differently, in the evening." This phenomenon does not explain the lunar illusion either, says scientist Carbon.

Moon research for everyone - by mobile phone

It is not yet known whether perception varies depending on age or gender, explains Carbon, and the data available so far is too thin for that. And this is exactly what the researcher wants to enlarge with the help of the Citizen Science project "Moondiary", i.e. lunar diary. This app (available for Android) can be used by anyone interested in the moon to enter their data. Carbon explains what exactly you have to do:

You are simply asked how the moon appears right now, how big it is, how far away it is. (...) We collect this data and later calculate back using the position of the moon, for example, where the moon was, how far away it was, under what conditions you saw it.

Claus-Christian Carbon, Perception Psychology

And not just in the night sky, but whenever we see the moon. Entries for the day are also possible if the properties of the moon or its position have changed. Entering into the app takes about a minute. That will probably not make us moonstruck, but in the long term it will make us smarter when it comes to the perception of the heavenly body.

The fact that science is bringing everyone on board who is enthusiastic about the moon phenomena is new. So far, researchers have mostly tried purely theoretical explanations on the moon illusion, says the Bamberg scientist, with experimental setups and very few test subjects. The Citizen Science App, on the other hand, at best collects data from a large number of different people, i.e. not just from students in a certain department or a small group of test subjects.

Moon research for everyone - until when?

The app can be fed moon observations until the end of summer. After evaluating all the data, perceptual psychology may then provide a new explanation for why the moon appears to us sometimes large and sometimes small, even though it does not change its size. A visit to the planetarium can generally show us very impressively, says Carbon - but warns at the same time:

You will be amazed by the stars, yes, but utterly disappointed with the representation of the moon.

Claus-Christian Carbon, Perception Psychology

Claus-Christian Carbon hopes - besides a batch of rich data - also for another effect:

We fly to the moon, but often don't look forward to the sheer sight of the moon.

Claus-Christian Carbon, Perception Psychology

We could all do that again, regardless of whether we (can) load data into an app or just enjoy the moon and keep our observations to ourselves.