John Brownlee for Cult of Mac:
But surprisingly, an iPad without anything installed on it does weigh less than an iPad that is full.
Why? Because data stored on flash drives has weight. The difference is almost infinitesimally minute, but it is there.
The extra weight comes from flash storage storing more data in memory. The transistors in flash memory distinguish between a 1 and a 0 by trapping electrons.
The more data a flash drive stores on it, the more electrons are trapped. And these electrons do have weight: For 4GB of data, the difference between full and empty is 10-18 grams. For a 64GB iPad, it would be 12 times that.
These calculations were done back in 2011 by University of California at Berkeley professor of computer science John D. Kubiatowicz for Amazon’s Kindle e-reader, but they’d be applicable to any device with a flash drive.
This really won’t be noticeable for anyone using an iPad, iPhone, or flash-based MacBook (most scales can’t even pick it up), but certainly fascinating to think about.