A View of the Map: Understanding How the Marauder’s Map Works

Let us take a look at the mysterious, amazing Marauder’s Map.

But first, let’s look at the castle. If you research castles on the Internet, you will see that Hogwarts is a castle of unprecedented (mammoth, huge, gigantic) size. You might find some castles that have towers that are 7 commercial stories high, but you will not find castles that have 7 floor main buildings. Example, a Keep, which is an older style square tower-like castle, is typically 90 feet high and will have three or at the most four floors in it. Hogwarts, in my imaginative view, has several wings all 7 floors high with very high ceilings, and its many towers are much much higher than that. Given that castles always have very high ceilings [Actually, except in special-purpose rooms such as great halls and chapels, the opposite tends to be true for most areas within a castle.—Ed.], I can picture the main 7 floor wings of Hogwarts being as high as a 12 to 14 story commercial or residential building. That would make the high towers in the range of a 20+ floor high common building. That is ONE BIG MOTHER of a castle.

Now picture that castle’s complete floor plans drawn in standard architectural format. That would be many many extremely large documents. But the Marauder’s Map is a single piece of parchment. Even if it is 3 feet on a side, the floor plans plus the castle grounds would have to be drawn at microscopic size to fit in that space.

I’ve always had the idea that the castle floor plans were layered on top of each other, and when you wanted to see a specific floor it came into sharp relief while the remaining overlapping floors fade to a pale unobtrusive grey. Even if that speculation is correct, the drawing would still have to be very tiny.

Plus, in combination with shifts in the wizard’s conscious desire, it could be very finely attuned to the mind of the user, to his subconscious fears and concerns, and could adjust what it shows based on the slightest shift in the perception, or mental state of that user. Just as your eyes make constant subtle shifts in focus, the map could shift what it shows based on subtle shifts in your mental focus; conscious or unconscious mental focus.

The minuscule size of the drawings alone could easily explain why Fred and George never saw Peter/Wormtail, and why Lupin never saw the second Harry and Hermione on the map during their time travels. So, the only thing you see clearly is the tiny area you are intensely concentrating on. Everything else fades to a blur.

Selective Display

Next, many have speculated that in order to keep the map from being too cluttered to use, it is selective in what it shows. As far as the map being selective, there are many different ways in which it could be selective.

We know that the map has ‘dead’ spots. Harry doesn’t see himself until he exits the classroom. Lupin doesn’t see Harry/Ron/Hermione/Scabbers until they exit Hagrid’s cabin. In addition, it would seem that Scabbers has been hiding out in Hagrid’s cabin for a while, and neither Lupin nor Harry ever saw him. It could very well be that Wormtail knew that the cabin was a ‘dead’ spot and that’s why he chose it.

Another possible reason why some areas wouldn’t be shown is that it’s possible that there are areas on the map that are irrelevant. Since the map is for ‘mischief making’, there would be no need to know who was in the Great Hall or the common rooms. It might be nice to know Snape was in the Great Hall, but unless you are making mischief in the vicinity, it serves no purpose. Plus the Great Hall and the common rooms are very crowded, so the map would show one big jumble of indecipherable names.

Which brings us to the next reason why some areas wouldn’t be shown. It is possible that it doesn’t show extremely crowded areas, like the common rooms. Showing the common rooms would be especially ineffective at certain times of the day when most of the students are there studying. Again, all you would see is a hopeless jumble of names.

Another mode of selective display could be proximity. You don’t need to know if Snape is in the furthermost point of the castle, but you would certainly like to know if he were nearby. So, picture an invisible bubble of importance surrounding the user. Anything within the boundaries of this bubble would be highlighted on the map. This wouldn’t be so much a matter of ‘live’ spots or ‘dead’ spots, but more a matter of highlighted foreground with the irrelevant faded into the background.

Another explanation of how so much information could be contained on such a small map is MAGIC. Perhaps the map is like Moody’s seven-key trunk or the boot (trunk) of Mr. Weasley’s car. The surface area of the map is far larger than its perimeter dimension. As you scan the surface of the map, your visual field grows while the size of the parchment remains fixed. Even if this is true, for it to be visually functional, the size of the drawings would still have to be small, and Harry confirms this. Harry constantly refers to everything on the map as minute (as in tiny, not 60 seconds).

Another ‘dead’ spot is the forest. The map can’t possibly show all of the castle, the grounds, and the forest too. So, I speculate that where the forest is shown, the map only penetrates 10 to 15 feet. That explains why Barty Crouch Sr. wasn’t seen until he moved to the edge of the forest near Harry and Krum.

I’m sure other people can came more ways in which the map could be selective.

Potential Conflicts in the Story

Why didn’t Fred and George see Peter Pettigrew on the map?

For the moment, let’s say it is not selective. Now picture viewing Gryffindor tower on the map, what are you going to see? A hopelessly undecipherable jumble of overlapping names. That would certainly make it difficult to pick Peter Pettigrew out of the crowd.

Next, Fred and George are at school; the context of the situation controls how they will interpret what they see. In the context of school, seeing the name of some underclassman (Peter P. or P. Pettigrew) in close proximity to Ron would mean nothing to them. In that context, where they are conditioned to expect to see the names of teachers and kids. I seriously doubt that one of them would see the name and go, ‘Hey, isn’t that the obscure old dead guy that we have some vague knowledge of?’. I don’t think so.

Then of course, they used the map for mischief making, and would have no reason to look for anyone other than someone who could affect that mischief making. Again, context controls what they see.

Why didn’t Lupin see time travelling Harry and Hermione?

Well, he wasn’t looking for them. He was specifically looking for Harry, Ron, and Hermione to go down to Hagrid’s. So he concentrated on the route from the castle to Hagrid’s. Time travelling Harry and Hermione were only on the grounds for a brief run, and by that time, Lupin had already spotted the ‘normal’ Harry and Hermione. After that, time travelling Harry and Hermione spent most of their time hidden in the forest, and in all probability, off the map. When they exited the forest to get Buckbeak, Lupin was concentrating on Harry, Ron, Hermione, and Scabbers walking back to the castle, and was then distracted by the attack by Sirius, the dog, after which time, he was rushing to their aid. He would have had no reason to search the map fully.

Barty Crouch searches Snape’s Office

In the Yahoo HPforGrownups group, Linda pointed out:

A single dot was flitting around a room in the bottom left corner—Snape’s office. But the dot wasn’t labeled ‘Severus Snape’…it was Barty Crouch. GF25)

She then asked a question related to the map’s selective viewing. She pointed out that Harry saw Barty Crouch but he would have had no desire, need, or intent to see Crouch. Harry would have no reason to be looking for Barty Crouch. He thinks he is at home, too ill to even go to work. He wasn’t looking to see if Snape was in his office because the preceding text line simply says that the movement caught his eye, not that he checked to see if Snape was in his office.

And I responded:

Barty would not be of interest to Harry in that he would never think to look for Barty on the map, and it may have been the movement that caught his eye, but I don’t think that shoots down the original theory. The key is not Barty or Snape, but Snape’s office. Snape’s office is an area that Harry would routinely and habitually be concerned with. It would be an area of interest to him on the map. So, I think it is safe to assume that this would be part of a default set of areas that would show up on the map. Snape’s office, Filch’s office, Dumbledore’s office, as well as their quarters, and the hallways would all be areas of concern to any rule breaker because they represent some of the people most likely to be out trying to catch rule breakers.

You are right, it was movement that caught Harry’s eye, but more than that it was movement in Snape’s office, and Harry would certainly be interested in any activity in there.

Final conclusion

Even if the map is aided by magical size distortion, everything has be very, very, very small, and available information has to be limited by some relevance, and therefore, the map takes forced concentration, focus and effort to view. This size, focus, and effort would reduce or eliminate the likelihood of accidentally viewing random peripheral information.