How much does downloading a book increase the weight of your Kindle?

Although the electrons were already present, keeping them still rather than allowing them to float around takes up extra energy – about a billionth of a microjoule per bit of data.

Using Einstein’s E=mc² formula, which states that energy and mass are directly related, Prof Kubiatowicz calculated that filling a 4GB Kindle to its storage limit would increase its weight by a billionth of a billionth of a gram, or 0.000000000000000001g.

This is roughly equivalent to the weight of a small virus, while the equivalent number of books – about 3,500 – would weigh approximately two tons.

And there you go, pointer courtesy of Mike Rosenwald.


Whew! That takes a load off my mind!

That's the sort of stupid, irrelevant science that boggles the mind. What's the point? If you indeed want to demonstrate E=mc2 is this the best example? All the dust and fingerprints on my Kindle probably weigh more. What's the Signal-to-noise ratio of such a computation? Hope no sixth grader tries to measure this for his science fair.

What's next: My GarminGPS displaying my Heisenberg uncertainty of location?

Wow, you sound like a very boring person.

Yes, intellectual curiosity is valueless. A question is only worth pursuing if it holds direct and immediate implications for your supply of water, food, shelter, or sex.

Unless you know two things, this is stupid.

(1) Does representing a zero weigh differently than a 1?
(2) Does downloading a book change the relative number of zeroes and ones?

Just another example of Tyler's credulity.

A kindle uses flash memory. The transistors used have two defined states, the default being 1. When you write information, you write zeros by applying a voltage.

Therefore: (1) yes (2) yes

Isn't most new flash made up of multi-level cells? So it's not just 1 and 0.

Also, even in single-level cells, whether a voltage is one or zero is just a convention. It's not even obvious that it has to be observed uniformly one way within a device. There might be advantages to doing otherwise.

I suspect you are wrong. A lack of information is probably entropy, and information is the energy required to re-organize the entropy.

Then perhaps I'm wrong. Why does it take more energy to hold something as 01 than to hold it as 11?

if TS is correct, simply because they chose '1' to be the lower-voltage state. You could do things the other way around and choose 0 to be low, 1 to be high.

The relation between thermodynamic entropy and information entropy is not obvious. It's just that they both use the name 'entropy' because of their shared log(1/p) characteristics.

Bits of information considered by themselves (apart from implementation details like voltage differences) have the highest entropy when the probability of a 0 or 1 is closest to 50%. A Kindle book might have this characteristic distribution, but the 'meaning' behind the data does not affect the entropy; 100k random bits does not contain any less information. Information theory does not speak to the meaning of data, only to the data itself.

For more info look up the Shannon paper. And there's an MIT course on youtube "MIT 6.450 Principles of digital communication"

Where would Einstein have stood to test the right measurement: between the object tilting at the windmill, or outside of the object and the windmill?

Adding energy does not add weight. Energy is conserved and mass is conserved, except in some very rare circumstances (none of which apply to the insides of a Kindle). E=mc^2 has nothing to do with the effect of gravity on energized electrons -- it only says that, under the right conditions, the energy of those electrons could be converted into something (mass) on which gravity could act producing weight. If the conditions to transmute energy into matter are not present, then the energy does not affect either the mass or the weight of the kindle.

This is very true. Any 'extra' energy going into memory is necessarily just being transferred from the battery. Maybe you gain some extra electrons next time you charge it up, though.

This is very not true. All forms of energy contribute to the energy-momentum tensor, which is the relevant stand-in for "mass" in this context. The point about energy coming from the battery is valid... the Kindle will be constantly losing mass (though heat radiation) if it's running on battery anyway. It's true that E=mc^2 has nothing to do with gravity, but it also doesn't "say" what you say it says. It's merely the formula for rest mass (the constant of proportionality between 4-velocity and 4-momentum) in special relativity.

The real gain in mass will be from all the Kindle owners who no longer get the exercise involved in carrying around the heavier books.

Best comment!

Non-stagnation markets in everything. Mass edition.

And that's why Americans are getting obese.

And the relevant comparison of course is not to the weight of the books, but to the weight added to the books and ink by organizing the ink just-so.

The new Murakami novel added 2 lbs.

I guess so.........

It is nonsensical to speak of a change you cannot perceive or measure, directly or indirectly.

Some of you guys sound like gender feminists. Where is your sense of humor? I have waited years for this problem to be addressed. I thank the physicist for their help in educating a senior citizen

This doesn't make any sense to me--the storage capacity of the battery does not increase when you add a book, so the energy contained cannot either. Keeping the electrons in place will require greater power (energy per time), but the effect will be faster draining of the stored energy in the battery, not an increase in energy.

I still think I am better off carrying printed books around: (not 2 tonnes though)

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