Nerd factor: It’s just a phase
Dr. Mike Robinson ~ UL Communication Studies Professor
At first, the ability to pass through solid objects seems like an ideal superpower to have. No walls can hold a phaser. No ropes can bind them. And in the very physical career of superheroics, no blow can land upon them. However, there are many problems and potential dangers associated with intangibility.
Watch your step. Excluding an outright magical origin for the power, intangibility tends to come in one of two forms. The first is a side-effect of density control. Consider, for example, the Vision. The synthezoid Avenger is able to lessen his density by shunting his mass into an alternate location (presumably another dimension) such that he may pass effortlessly through solid objects. The second source of the power is essentially a reorientation of molecules. The things around us that seem solid are in fact mostly small amounts of matter bound together by powerful physical forces. There is all sorts of space in between if one can just find a way to slip through it. Heroes such as the Flash or Kitty Pryde (aka Shadowcat) are able to not so much violate these laws of physics as bend them a bit to their advantage, nudging their own molecules through.
No matter how intangibility is achieved, though, it works in all directions. If one can slip through a wall then one can fall through a floor. And if a superhero is not careful, then that superhero can end up knee deep in the floor, or worse, falling into the ground below. Density manipulators risk floating away, because they are presumably lighter.
It is all in the footwork. For this reason, what seems like a very casual superpower actually becomes an exercise in intense concentration. Intangible superheroes must be able to vary the use of the power across their bodies, keeping at least the bottoms of their feet solid until they have to walk through a wall or actually want to sink through a floor. Imagine having to think about every step you take. Long hours of practice would be needed until this became almost reflexive.
Hold your breath. Presumably, intangibility comes with the benefit of being able to take some of the molecules around you with you. Thus, no phasing superhero steps out of their clothes and arrives nude on the other side of walls. Air in the lungs is probably part of that deal. However, any superhero who steps into a large amount of solid material, say while penetrating a villain’s secret mountain lair, has only so much time to do so before passing out from lack of oxygen. Suddenly solidifying in a wall is not ideal.
Timing is everything. Turning off intangibility while still inside any object is quite painful. Some superheroes have used this power as a mighty weapon. The Vision, for example, once defeated Hyperion (Marvel’s equivalent to Superman) by solidifying his arm inside his foe’s chest. The Vision is a machine though and he can probably turn off the pain. It may not hurt him to be stuck in a wall. Most superheroes cannot do this though and thus every use of the power carries a fatal risk.
However, there are more than just the obvious solid people and objects to avoid. The air is full of many “no see ‘ems”. Consider, for example, Central Virginia’s most abundant summer lifeform, the gnat. Phasing seems like a fantastic way to avoid the clouds of floating bugs, but those things get everywhere. Solidifying with a gnat or two in the brain is bound to do some damage.