Virtual human puts doctors inside their patients

Let me preface this by saying that the preceding news article is actually very good news. I worry that what I will say next may give the impression that I am against this “virtual human” as an amazing tool for medical science.

There has been a very interesting discussion going on that I am happy to call attention to yet again, because I think it has the potential to go on and on and on and it’s very cool to me. (It’s an older article from this website and all its following comments.) We have been talking about art and its meanings and manifestations, and somewhere in there is a brief tangent about semantics.

I consider myself a laid-back person, but for some reason I’m a stickler for semantics. I think it’s important that we all know what we’re talking about and express our ideas properly so that others listening may be on the same page. With all our tools of communication nowadays, our language(s) is(are) evolving faster than the ecosystem after a nuclear powerplant meltdown on the Galapagos Islands. In other words, really fast. So whenever I see something, especially a news article, make a linguistic mistake, my first reaction is panic and outrage. I don’t always make sense myself, so I am forgiving of others, but still…grrr.

What the virtual human described in the article linked above does is show doctors what objects in the bloodstream will do, and doctors can watch these virtual objects travel through the virtual human as they would in reality (supposedly). The virtual human is a three-dimensional view of the inner workings of the human body. (It’s actually a two-dimensional view seen through 3-D glasses, which is just an optical illusion, but for the sake of my post, we’ll simply refer to it as 3-D. I don’t want to go on too many tangents here…)

What I balk at is when the article calls it four-dimensional. It’s not. It’s a very common misconception, and it drives me mad.

The fourth dimension isn’t time — not exactly. Okay, we can call it “time” if we have to, but only in the sense that it’s just a name, like “length,” “width,” and “depth.”

It’s hard to explain, but I will try. Think about a graph. The first dimension is length. You add a new axis to it at ninety degrees and you get width, or the second dimension. Right? Now you can have planes, not just lines (as well as all sorts of other shapes). You add a third axis at ninety degrees from the second, and you get depth, the third dimension. Now you can have cubes and spheres and pyramids and all kinds of groovy shapes of all sizes.

In this fashion, the fourth dimension is not the passage of time. It’s really fucking hard to imagine another axis at ninety degrees — which way could it possibly go? — but that’s pretty much what it is. I’m no physicist, but I can say with a fair degree of certainty that a three-dimensional model of a human body is just three-dimensional, and at any given moment in time you see a small object moving around through that model, you’re always seeing it in 3-D. The human brain works best in 3-D, that’s why a fourth dimension is so hard to visualize.

Cubism is an attempt at creating a visual representation of four dimensions. In this light, the fourth dimension could be described as the passage of time. Cubist painters showed an object in three dimensions — it looks so bizarre to us because their attempt was to capture this three-dimensional object as it would look if the change in view were a process that required time to pass. For example, if you walk in a circle around the Eiffel Tower, it appears different from every angle. Or if you leave a bowl of fruit by the window, the shadows and colors change as the sun passes over the house. All this on one canvass, which you see at the same moment in time.

Again, don’t get me wrong — I love Cubism to death; I think the paintings are immeasurable fascinating — but the attempt was incomplete. I doubt any human could produce a complete visual representation. You would have to somehow show all angles of the third dimension on one plane, and then all angles of the third dimension on a related plane, and for every plane involved. (In this paragraph, by “plane” I mean whatever one would call in the fourth dimension what in the third dimension we see as a plane.) And to capture the whole of the third dimension onto one plane, think about this: a circle is two dimensional, with 360 degrees around its center (and, of course, an infinite amount of fractions of degrees in between; mathemeticians just decided one day that 360 was a good number). A sphere is like a circle rotated along one axis 360 degrees (and, again, an infinte amount of fractions in between). So a sphere has 360 to the power of 360 degrees from its center. (That’s a really big fucking number!) That’s the third dimension, a sphere. Easy enough to show on a canvass or a computer monitor. To show the fourth dimension, you would need to display that really big number TO THE POWER OF 360. Whatever shape that makes. I can’t see it, but that’s the fourth dimension. To see that shape in one moment in time, that’s 4-D. Not a 3-D object as it moves around.

Anyway.

There’s not much use for a rant like this, and again, the virtual human is undoubtedly a fantastic medical device. I think I would just prefer it if people didn’t confuse the fourth dimension with the passage of time. It’s a matter of semantics. If I’m not making sense, I apologize.

Whatever. There’s a better post coming up next. I’m not sure when it will be, but there is a sequel, and it will be better. I think.

Filed by Bil at 3:57 pm under The Arts, The Science