Why could Mad-Eye Moody see through the Invisibility Cloak using his Magical Eye?

Question

In the film and book series, Year 4 (Goblet of Fire), how is it Mad-Eye Moody/Barty Crouch could see Harry through his Magical Eye even when he was under the Invisibility Cloak?

As the cloak is a True Invisibility cloak, immune to charms and spells, and according to legend invisible to even Death, how did Mad-Eye detect Harry Potter under the cloak? How Nagini and Mrs. Norris were able to sense Harry were through other senses, such as smell and warmth, but not visually.

I'm referring to the scene/chapter where Snape follows Harry at night. Harry hides under the Invisibility Cloak but his foot is stuck at the broken staircase. Eventually Mad-Eye arrives, sees Harry through his Magical Eye, and talks Snape away.

Answer 1

There is a canon discrepancy regarding the Invisibility Cloak. You are correct that Harry's cloak was described as a "true" Invisibility Cloak, immune to charms and spells, indestructible, and invisible even to Death, by Xenophilius Lovegood.

However, in Tales of Beedle the Bard, Dumbledore's notes represent the cloak differently and not quite as impervious as Xenophilius Lovegood claimed. In Tales of Beedle the Bard, the cloak is described as having a "uniquely durable nature" and is not described as indestructible, impervious, or immune to Death's gaze. J.K. Rowling writes:

Invisibility Cloaks are not, generally, infallible. They may rip or grow opaque with age, of [sic] the charms placed upon them may wear off, or be countered by charms of revealment. This is why witches and wizards usually turn, in the first instance, to Disillusionment Charms for self-camouflage or concealment.

_{Tales of Beedle the Bard - pages 96-97 - Bloomsbury Edition - chapter 5, The Tale of the Three Brothers}

We know for certain that at least one spell works against the Invisibility Cloak: Homenum Revelio. In Chamber of Secrets, Dumbledore uses Homenum Revelio to see Harry and Ron under the Invisibility Cloak in Hagrid's hut:

‘However,’ said Dumbledore, speaking very slowly and clearly, so that none of them could miss a word, ‘you will find that I will only truly have left this school when none here are loyal to me. You will also find that help will always be given at Hogwarts to those who ask for it.’

For a second, Harry was almost sure Dumbledore’s eyes flickered towards the corner where he and Ron stood hidden.

_{Chamber of Secrets - page 195 - UK Hardcover - chapter 14, Cornelius Fudge}

J.K. Rowling confirms this in an interview:

Angela Morrissey: Why is it that albus dumbledore can see harry under his invisibility cloak at certain moments? (during the series is the cloak only infallible to those who do not own a deathly hallow).

J.K. Rowling: Dumbledore, who could perform magic without needing to say the incantation aloud, was using ‘homenum revelio’ - the human-presence-revealing spell Hermione makes use of in Deathly Hallows.

_{J.K. Rowling Webchat - 07.30.07 - [THE LEAKY CAULDRON]}

If Hermione could master Homenum Revelio, I'd wager Barty Crouch Jr as Mad-Eye Moody could have as well. Barty Crouch Jr was a bad guy and a Death Eater, but he did demonstrate he was competent at magic throughout Goblet of Fire. So Homenum Revelio is one possibility for how Crouch Jr/Moody was able to see Harry through the Invisibility Cloak. I interpret canon, though, as Mad-Eye's eye having powers above and beyond Homenum Revelio. Crouch Jr/Moody actually interacted with Harry while Harry was under the Invisibility Cloak; they had a silent conversation. It's clear Crouch Jr/Moody saw Harry. It's not clear whether Dumbledore saw Harry and Ron under the cloak in Hagrid's hut, or if he merely detected human presence (which is the extent of Homenum Revelio's power), then discerned what general area it was coming from, and knew it was Harry because who else (that we know from canon, circa Chamber of Secrets) had an Invisibility Cloak at Hogwarts?

Putting it lightly, it's likely Moody's magical eye was charmed to have exceptional and/or rare sight abilities -- heck, Moody probably could've seen the future with that eye! Okay, not really, but at the very least the magical eye was a prosthetic device that Moody could effectively channel revealing charms through (although that Ollivander in Deathly Hallows says a wand is the required instrument for channeling magic should be taken into consideration. If it actually channeled magic, I believe Moody's eye would be the only other instrument besides a wand to channel magic in canon¹). At most, the eye itself is a very powerful magical object (this is what I tend to think) which has magical abilities that just aren't directly explained by canon. We can only infer. Another point to remember is Dolores Umbridge was able to fasten the eye to her office door and presumably use it to channel sight in some way; we don't know from canon exactly how Umbridge used the eye, although it seems she merely used it to see who was approaching her office.

While a powerful magical object, I don't see Moody's eye as being on the same level as the Hallows.

¹_{I realize that some people parse Ollivander's words to mean a witch or wizard can channel magic through any kind of instrument -- meaning anything, any object -- but in the context of the conversation, I interpret Ollivander's words to mean a wand is the singular instrument for channeling magic and that almost any wand will work for a magical person. Deathly Hallows - chapter 24 - The Wandmaker - page 399 (UK) - page 494 (US)}

Answer 2

In the first DatDA class (the fake) Moody teaches, he calls out a student for not paying attention by seeing through a wooden desk. So we know the eye is capable of seeing through objects. There are a few ways to explain both this and being able to see through cloaks:

• The eye can see outside the regular visual spectrum, for example infrared or x-rays. Invisibility cloaks may not be designed to work with these wavelengths, which would render it useless - infrared in particular would be just like sensing heat.
• The eye has some sort of "sonar" system, bouncing waves around the room to figure out how it's shaped. You could look around objects by bouncing waves off the back wall, for example. Since the cloak is still tangible, it would be obvious.
• The eye is somehow capable of ignoring objects from its perception, allowing the user to see whatever's behind them. Think of having a stack of papers and removing the top one so you can read the next one. While it could easily ignore the cloak, you would first have to know it's there (possibly combining with one of the above).

Answer 3

I think we can all just agree (although it's blasphemy) that J.K Rowling, possibly, had not yet considered the exact details of the Hallows when writing and publishing the Goblet of Fire. Therefore, she made a human mistake. The invisibility cloak was supposedly perfect, impervious to all magically aided sight. I'm sure, in retrospect, J K Rowling would agree that Moody's eye should never have been able to see Harry through the cloak. Yes, possibly sense him in the way Dumbledore can sense the trace that magic leaves. But to be actually able to see through the cloak and see what/who's under there? I believe this to be a simple mistake....nothing more.

Answer 4

Whilst the Cloak is resistant to many spells such as accio, it has been shown previously that wearing the Cloak is not a guarantee of invisibility. Certain powerful magic can still enable the wearer(s) to be seen; for example, whilst Harry was wearing the Cloak, Dumbledore was able to see him without any apparent spellwork.

It also seems that charmed objects have greater and more reliable power than a witch or wizard performing a spell for the same effect. Only two wizards have been known to fly without the aid of a broom, and yet a broom can enable others to fly extremely well. Other objects have been so well protected by charms that spells can't damage or destroy them.

Paranoid as Mad-Eye was, he is sure to have augmented the eye with the strongest charms to detect the otherwise undetectable.

Answer 5

The story of Death himself creating the Hallows, while poetic, is just that - a story. Dumbledore himself said that the Peverells were probably just incredibly talented wizards, who were able to create such powerful artefacts.

If one wizard can make a long-lasting cloak of invisibility impervious to most spells, it stands to reason that another similarly skilled wizard could make something that can see through it. There's no question that Moody was indeed a great wizard, and also good friends with Dumbledore who himself may have assisted with the creation of the magical eye.

So my understanding was that far from being completely impervious, the cloak simply needs a similarly powerful spell or magical item to counter it.

Answer 6

Okay this may be a bit of a stretch, but nobody else has mentioned it so... when Harry forgot to jump the vanishing step, I believe it is mentioned that if someone coming from below looked up, they'd see his disembodied leg dangling because his leg slipped through the hole there (with the cloak being bunched up at the top of his thigh, so the rest of his leg was visible). Could Moody have just used his ability to look through objects to see a dangling leg and guessed the rest?

Or perhaps, continuing the with that line of reasoning... using the ability to see through objects, could MadEye possibly see Harry underneath the cloak without actually seeing a flaw in the cloak itself? The same way he could see someone hiding on the other side of a wall? So in essence, seeing both layers of it: first the perfect layer of invisibility that the cloak provides; and second a wholly separate layer of Harry BENEATH the infallible enchantment.

Answer 7

The cloak makes someone invisible, not sense-immune (as you noted, you can detect via smell and warmth).

It's possible the cloak emanates some magical residue/smell (Dumbledore tells of being able to detect traces of powerful magic when he was tracing Voldemort's steps at the cave in HBP); which is how both Dumbledore (allegedly) and Mad-Eye's eye can detect Harry under the cloak.

Answer 8

Coming up with some magic/pseudo-science, you could argue that the cloak worked by moving light around the cloak, which would make you invisible to anything that worked through optics. It would not cover up smell, and we have seen that it does not prevent others from hearing you. Mad-Eye's eye could work with something other than just light, and thus be able to detect someone shielded by a cloak.

Answer 9

We know very little of the cloak and its exact features. What we know for sure is that it can hide the user from plain and unsophisticated magical eyesight. It is unknown whether it also hides the following factors (I tried to order them in order of decreasing plausibility):

• Infrared / Ultraviolet light
• Traces in the dust on the floor
• Sounds (footsteps, shifting clothing, breathing, heartbeats)
• Actual sonar by detecting a soft barrier where none should be
• Smells, ambient dust, movements in the air

And this is just things which could give away a person to a muggle with sophisticated technology, to wizards employing appropriate spells, or to animals. The impression I got from book 7 is that it is very hard, especially for wizards, to properly dissolve all traces.

Additionally, the very presence of magic makes it possible to ignore most of the laws of physics and to devise other ways to sense things. Maybe Moody's eye could do something like open a wormhole to a random point in space and peek at what is visible from there. Maybe it picked up on gravity. I could not infer from the lore what it really did.