Software grows, hardware shrinks: That's more or less the story of the tech industry right now. So it's a little surprising to see that the new iPad is both thicker and heavier than its predecessor: .37 inches and 1.44 pounds to the iPad 2's .34 and 1.34. This isn't much extra bulk, sure, but it's certainly not less.
More than processor cores or camera specs, this is the kind of thing that matters to would-be buyers. This thing is neat, they think, but isn't it kind of heavy? Yep! Heavier than a book, heavier than a Kindle. Too heavy to hold with one hand for more than a few minutes. Too heavy to throw around carelessly. The iPad Proposition would be fundamentally different if the tablet weighed, like, a three-quarters of a pound and was as thin as a Kindle.
Anyway, here's what's happening: Apple has hit the battery wall.
When you crack open an iPad, here's what you find: A couple little circuit-boards and a giant battery. The width and height of the iPad is determined by the screen, the size of which is up to Apple. The thickness of the iPad is determined almost entirely by its battery. (If the iPad 2 didn't need a battery, it would have been 7.4mm thick--that's .29 inches)
Here's what the batteries in the first and second iPad look like:
The only reason Apple was able to make the second iPad thinner than the first is that it found a slightly better battery: A unit that held a bit more energy--25 watt-hours, compared to 24.8--while being half as thick (but much wider). It was a more efficient, or dense, battery with a much better design.
Apple was able to pull this off because the iPad 2 was, in power terms, about the same as the first one: Same screen, similar processor power demands, etc.
To power the new iPad's super-high-resolution retina display and the graphics hardware needed to run it, as well as 4G internet, the new iPad needs more power, and more battery. We don't know how much more, exactly, but it must be a lot--enough to force Apple to release a thicker, heavier version of one of its products, which it never does. (Well, not quite never: The second iPhone was thicker at its center than the original because--yup!--it needed a bigger battery for 3G.)
Chalk this up to a larger issue: Batteries are the worst parts of our gadgets: They're what make them bulky, they're what make them hot, they're what make them go black every night and die completely after just a couple years. To make matters worse, the prospects for a new type of battery are bleak--we've been using the same basic technology for a decade, and may be stuck with it for another.
In other words, batteries are the worst. That's why the iPad is the way it is.