
The more data you save on a flash drive, the lighter it gets? - zdw
https://www.sciencefocus.com/future-technology/does-a-usb-drive-get-heavier-as-you-store-more-files-on-it/
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kens
Isn't that complete nonsense? Although the gate gets more charge, that's going
to be balanced out by less charge elsewhere. The USB drive as a whole isn't
gaining electrons, or else it would have a negative static charge, which would
be dissipated as soon as it is connected to ground.

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bluesign
Yeah actually from my understanding, even in the transistor, state (location)
of electrons should change only, not the number of electrons.

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nomel
Isn’t the concept that the location difference causes a potential/energy
difference, which has mass?

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viklove
It's all changing within the system (USB drive), so to an outside observer
there is no change in mass.

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nomel
A system with more potential energy will have more mass [1]. For example, a
compressed spring has more mass than a spring at rest, and will take more
energy, from an external force, to get to the same velocity. Same with a
spinning disk. So unless there's a nice balancing act, with no potential
energy change from moving electrons around within the drive, the mass of the
drive will change, negligibly, from the potential energy change of the gates.
So, the real mass loss of a USB drive is electrons out in addition to
potential energy loss from the floating gates. So it's, the world smallest
double whammy!

[1] [https://physics.stackexchange.com/questions/274329/does-
pote...](https://physics.stackexchange.com/questions/274329/does-potential-
energy-of-an-object-increases-its-relativistic-mass/274680)

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kerrto
The question can be simplified to: does a charged capacitor weight more?

As a first approximation, the answer is No: each electron on the negative
plate is balanced by a missing electron on the positive plate.

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nomel
The mass comes from the potential energy. Same as a spinning disk has more
mass than a disk at rest.

It’s absolutely negligible, but it’s real.

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DougN7
Potential energy has mass? Is that true? It means a rock at the top of a
mountain has more mass than it does at the bottom of the mountain. And a
stretched rubber band has more mass than a relaxed rubber band. It’s been a
looong time but I don’t recall learning this in physics.

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nomel
You surely did, but the literal reality of the mass-energy equivalence maybe
wasn't apparent: E = mc^2

A system with more potential energy will have more mass.

See: [https://physics.stackexchange.com/questions/274329/does-
pote...](https://physics.stackexchange.com/questions/274329/does-potential-
energy-of-an-object-increases-its-relativistic-mass/274680)

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fortran77
It's not clear what the default erase state is. It could be all 1s or some
other pattern used during testing.

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monocasa
Yeah, as shipped they tend to have random looking patterns from procedures in
the factory searching for bad blocks.

Edit: it might be hard to see in a dd of the disk, because all ones or all
zeros for blocks tend to be special cases in the FTL to not even have blocks
associated and just mark that it was all zeros/ones to avoid wear.

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strathmeyer
"This means that an empty USB drive (which mostly holds zeros)"

...maybe?

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kosma
Default erase state for NAND memory is ones.

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segfaultbuserr
It's also true for most NOR memory and most earlier EEPROM and EPROM chips.
This convention came from the original OTP memory - a "0" is created by
burning the fuse to physically destroy an electrical link [0] on the chip, you
can only change "1" to "0", not vice versa.

[0] In physical implementation details, however, an antifuse is actually more
common than a fuse, i.e. breaking the link (e.g. by a high voltage pulse)
creates a short, not an open.

