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Data Has Weight but Only on SSDs

46 points by LorenDB ago | 24 comments

tliltocatl |next [-]

I think the article is wrong in its core premise. While the electrons get added or removed from the floating gate, the total number of electrons in the SSD chip stays the same. Gates are capacitors, in order to add electrons to one capacitor plate, you have to remove an equal numbers of electrons from the other plate, i. e. from the transistor channel. The net charge of a SSD chip is always zero. Otherwise it would just go bang. <s>2.43×10^-15</s> [my bad 1] 2.67×10^15 electrons is about 300µC - that's a lot of charge to separate macroscopically.

Therefore the mass (weight is a different thing, through it is proportional to mass at a given constant gravity potential) of the data on a SSD isn't fundamentally different from a HDD - they both are caused by a change of internal energy without any change in the number of fermions. I'd expect data on SSD to have larger mass change because a charged capacitor always store more energy than a discharged one, while energy of magnetic domains is less directional and depends mostly on the state of neighbor domains - but I'm not sure about this part.

[1] Thanks stackghost.

nickcw |root |parent |next [-]

> So, assuming the source material is correct and electrons indeed have mass, SSDs do get heavier with more data.

That is definitely wrong! No way the source material has more electrons. The only way it could do that is by being charged.

Richard Feynman, The Feynman Lectures: "If you were standing at arm's length from someone and each of you had one percent more electrons than protons, the repelling force would be incredible. How great? Enough to lift the Empire State Building? No! To lift Mount Everest? No! The repulsion would be enough to lift a "weight" equal to that of the entire earth!"

From: https://tycho.parkland.edu/cc/parkland/phy142/summer/lecture...

stackghost |root |parent |next |previous [-]

>2.43×10^-15 electrons

I believe TFA reads 2.43×10^-15 kg, not electrons. Unless SSDs are creating new and exciting physics, one can't have less than one electron, as it's an elementary particle.

karmakaze |root |parent |next [-]

Well you could have a virtual particle whose mass could be time-averaged.

jmalicki |root |parent |next |previous [-]

Neutrinos weight far less than electrons (but while NAND flash involves super weird physics it's not that weird)

stackghost |root |parent [-]

They do weigh far less, but a quantity of "10^-15 electrons" is still impossible.

alanh |root |parent |previous [-]

10^–15 is not a negative number, just a small one. https://www.wolframalpha.com/input?i=10%5E-15+

1718627440 |root |parent [-]

And it is less than one?

JadeNB |root |parent [-]

I think my favorite part of that comment is "documenting" that 10^(-15) is not negative by appealing to Wolfram Alpha.

zahlman |root |parent |previous [-]

TFA started out seeming well enough written but definitely turned LLM-padded in the middle. And yeah, I think you're right about the actual science.

nwellnhof |next |previous [-]

Reminds me of an old April Fools' prank in German c't magazine. They offered a defragmentation-like tool for HDDs that claimed to distribute 0s and 1s more evenly on the drive to make it run more smoothly and extend its lifespan.

jerf |root |parent |next [-]

Amusingly, that's unnecessary, but possibly not for the reason most people think. It's not because the hard drive hardware is oblivious to runs of 0s and 1s exactly... it's because it's actually so sensitive that it already is recording the data in an encoding that doesn't allow for long runs of 0s and 1s. You can store a big file full of zeros on your disk and the physical representation will be about 50/50 ones and zeros on the actual storage substrate already. Nothing you do at the "data" layer can even create large runs of 0s or 1s on the physical layer in the first place. See https://www.datarecoveryunion.com/data-encoding-schemes/

omgbear |root |parent |previous [-]

I think my network card does that.

TazeTSchnitzel |next |previous [-]

Lights in video games are real, but only if you're using an OLED or CRT.

tlb |next |previous [-]

The rate at which molecules of plastic sublimate off the surface of the enclosure is probably a much larger amount of mass. The rate increases with e^kT, where k is such that it doubles about every 10 degrees C. So if you get a drive and fill it with data (which warms it up significantly) the lost casing material will dominate the mass balance.

stephbook |next |previous [-]

Light bulbs in video games use real electricity.

alanh |next |previous [-]

"Data has weight, but only on SSDs" - Not just SSDs! Unless you always hang the chad, surely writing data onto punchcards reduces the weight of that 'storage medium'!

erg0s4m |root |parent [-]

So it has negative weight in this case.

epx |next |previous [-]

Was expecting Boltzmann and entropy to be involved at some point :(

MengerSponge |root |parent [-]

Yeah, I was motivated to go Wiki diving, where I just learned about the Shannon (unit). https://en.wikipedia.org/wiki/Shannon_(unit)

Time to replace "I'm zero surprised" with "That's a zero Shannon event"

antimatter15 |next |previous [-]

Another fun calculation is that due to special relativity, a hard drive that is spinning gains a certain amount of mass due to the rotational kinetic energy and E=mc^2.

Assuming the platter is 100g, 42mm, spinning at 7200RPM, there is about 25J of rotational kinetic energy, whose mass equivalent is 2.8x10^-13g (0.28 femtograms).

Assuming 200 electrons per NAND floating gate with 3bits/cell TLC on a 2TB SSD, there would be 5.3x10^14 electrons, weighing about 0.5 femtograms.

themafia |next |previous [-]

More appropriately data has a temperature.

https://en.wikipedia.org/wiki/Thermodynamic_beta

jmclnx |previous [-]

interesting, I wonder if one can translate this into the amount of data on the drive ? Maybe it does not matter unless one cleared the drive using dd(1).

Also would trimming cause a different value even though the data size remains the same ? I would think so, assuming I understand trim.