Mary Poppins, the 1964 musical film produced by Walt Disney, was an immediate smash hit. Starring an until-then largely unknown Julie Andrews, the film went on to 13 Academy Award nominations and earnings of more than $100 million at the box office. The film was so profitable for the Walt Disney company that it played a role in financing Walt Disney World in Florida.
While it's difficult to imagine a world wherein Mary Poppins doesn't exist, pop culture phenomena like this can't be predicted or intentionally manufactured. Instead, they simply pop into our lives when we most need them, not unlike Mary Poppins herself.
In her duties caring for the Banks children, Poppins unveils a seemingly endless bag of tricks, including controlled flight aided only by an umbrella; she also boasts the ability to inhabit animated spaces, not to mention an impressive singing voice. There is also, of course, the bag itself, with its TARDIS-like ability to be larger on the inside. The Banks children rarely question their new nanny's special abilities, willing to accept her particular brand of magic on its face.
This week, however, 54 years after her initial on-screen appearance, the magical nanny is back in Mary Poppins Returns, and we're older, wiser, and ready to examine just what, exactly, is going on.
The easy answer, and the one Poppins seems to want people to accept, is that she is simply magical. And there's a good reason for that; the world of the 1950s wasn't ready for the truth. Poppins likely would have been run out of town on a rail if anyone caught wind of the undeniable truth: Mary Poppins is an interdimensional visitor from a higher dimension.
Allow me to explain.
The case for extra dimensions
Each of us exists in a reality that is seemingly comprised of three spatial dimensions: left-right, forward-back, and up-down. But there's good evidence that more spatial dimensions exist.
According to implications of Einstein's General Relativity, spacetime isn't flat, it's curved. It's difficult to imagine curvature of a three-dimensional space because our brains just aren't set up to visualize objects in more than three dimensions. Despite that, experimentation supports the notion that spacetime is not flat. And the measured curvature suggests the existence of a fourth spatial dimension (maybe more) that we aren't capable of seeing, at least not from our current viewpoint or with our current technology.
Carl Sagan discussed the problem in an episode of the original Cosmos and provided a useful thought experiment to help visualize what it might be like. In it, he posits a two-dimensional world, a la Edwin Abbott's Flatland novel, curved into a three-dimensional sphere. 2D beings living in that world would be incapable of seeing the curvature, but they could detect it through experimentation.
Moreover, recent experiments published in the journal Nature might support the notion of four-dimensional space.
Beings on a 2D world wouldn't be able to see a 3D object hovering over them, but they would be able to see its two-dimensional shadow being cast over their world. Scrutinizing that shadow might not tell them much about the nature of the object, but it would tell them something.
This is what two teams of researchers in the United States and Europe attempted to do, detect the shadow of 4D processes, and those experiments worked.
Just like the inhabitants of Flatland, any objects or living entities existing in 4D space would be invisible to us, here in 3D space, unless they happened into our plane of existence, even then we would only perceive them as an incredibly small cross-section of what they really were.
In the case of a sentient being from a higher plane, it stands to reason it might have some control over how it appears to us. It might, for instance, choose to appear as a light-hearted nanny with a penchant for song and dance.
Power of movement
Our first clue toward Mary Poppins' true origin occurs during her first appearance onscreen, just a few moments into the beginning of the film. She sits, rather casually, atop a cloud, without the slightest hint of the effects of rational fear or gravity.
Later, when she arrives at the Banks' home, she does so by floating leisurely down with only the aid of an umbrella. An examination of her descent reveals a complete disregard for the laws of physics. Even more telling, she initially comes in too low and, at the last moment, pops a little higher to make it over the fence.
It's clear to anyone watching that she isn't actually gliding under the support of that umbrella. Instead, she is moving under her own power, via forces unknown to humanity. That umbrella is nothing more than a prop, and a thinly veiled one at that.
The more likely explanation is that Mary Poppins is capable of moving up and down with ease, the same way you or I might move forward and back or the right and left.
To better understand, we need only to take the two-dimensional Flatland and turn it on its side.
If we imagine a 2D plane standing on its end, we see that inhabitants of such a world would experience the directions left-right and up-down. Supposing they had something equivalent to gravity, they might be confined mostly to the bottom of the plane, excepting to the limit they could climb, build, or locomote via technology.
Should you stand in front of such a world and stick a finger in, thus entering this vertical Flatland, you'd have little trouble resting on a cloud or moving up and down under your own power.
Mary Poppins isn't flying, she's doing something much simpler, yet all the more impressive: sticking her unimaginable finger into our world.
Her magic carpet bag
One of the most impressive tricks up Mary's long black sleeve is her seemingly endless carpet bag (made of carpet). Her bag is capable of holding anything and everything Mary might need, despite being empty when the Banks children look inside.
This bag has often been compared to the Doctor's TARDIS and given as evidence that Mary Poppins might herself be a Time Lord. And for good reason.
On several occasions, the Doctor has made clear that the internal space of the TARDIS exists via use of the fourth dimension. Upon entering the TARDIS, the Doctor or his companions leave traditional spacetime and move into another type of space altogether.
This could explain the way Mary's carpet bag works, as well.
Again, the best way to understand this is to return to Flatland with a container of our own. Let's imagine, when journeying into 2D space, you bring with you, not a carpet bag, but a carpet tube. To the inhabitants of Flatland, the container would appear relatively small, only as large as the circumference of the tube. Yet you would be capable of storing much more than would fit within that area by shuffling it down the tube and into three-dimensional space.
When any two-dimensional being looked into the tube it would appear empty in much the same way Mary's bag appears empty when the children look inside.
We can attempt to understand this in 4D space by examining polytopes.
A polytope refers to any geometric shape with flat sides existing in any number of spatial dimensions.
By taking a one-dimensional line and dragging it an equal distance at a right angle to itself, you get a square in 2D space. Repeat the process again in the third dimension and you end up with a cube.
Imagining an object in 4D space requires a bit of mental gymnastics. Taking that cube and moving it out again at right angles to all existing sides gives us a tesseract. It's nearly impossible to imagine, but the math works out. If Mary's carpet bag, like the TARDIS, exists in this way, it allows for the observed behavior.
Jumping into flat land
Even after all this, you might be tempted to discard the notion of Mary Poppins as a 4D visitor out of hand. But don't be so hasty. Perhaps the most obvious evidence for her dimension-hopping shenanigans comes from one of the film's most beloved scenes.
Accompanied by Bert (Dick Van Dyke), Mary Poppins and the two Banks children enjoy a stroll on the town admiring chalk art displayed on the street. What follows is a famous scene combining live action with animation. It's a spellbinding sequence, but it tells us something important about the abilities of the titular caregiver.
Without any more than a second glance, she gathers her companions and leaps into a lower dimension. From this, we can surmise two things. First, Poppins is, in fact, capable of traveling between spatial dimensions, and she is capable of moving others in the same way.
As explained by Sagan above, an entity from the third dimension acting on the second would be able not just to enter but manipulate inhabitants of that lower plane in otherwise inexplicable ways.
Poppins accomplishes this miraculous feat with such aplomb we can confidently guess that she must have considerable experience.
If all of this weren't enough, Mary Poppins tips her hand in her use of naming conventions. Her very own surname gives us a clue, and the books that serve as the source material confirm it. That name comes from the way she "pops in" and out of people's lives, of the story, and of our world. Likewise, her carpet bag is an obvious nod to the term "carpetbagger," which refers to a person acting in an area with which they have no local connection. Sound familiar?
Under the weight of these conclusions we can only be grateful that Mary Poppins uses her otherworldly powers for dalliances in worlds of chalk and magic, rather than to tear our world asunder.
Though it's been more than 50 years since she last popped out of our plane of existence, Mary Poppins Returns is now in theaters.