# Information is energy

1. Aug 2, 2010

Is information energy?

This thread was inspired by a conversation https://www.physicsforums.com/showthread.php?t=419343". I thought we got a little off topic, but the conversation is worth continuing.

The idea seems to stem from http://en.wikipedia.org/wiki/Landauer%27s_principle" [Broken] that states that "any logically irreversible manipulation of information, such as the erasure of a bit or the merging of two computation paths, must be accompanied by a corresponding entropy increase in non-information bearing degrees of freedom of the information processing apparatus or its environment."

This seems to indicate to me that it is the computational process rather than the information itself that increases entropy. It reasons that any type of computation would increase entropy since computation is work.

Is it generally accepted that Landauer's principal equates information to energy? If not, is there another principal/law/etc. that does?

Last edited by a moderator: May 4, 2017
2. Aug 2, 2010

3. Aug 3, 2010

4. Aug 3, 2010

### Andy Resnick

Hint: thermodynamic quantities are easily calculated for *cyclic* processes (closed loop in state space).

5. Aug 3, 2010

### Pythagorean

(Smith, 1999)?

IBM "zero power" information destroy

6. Aug 3, 2010

Re: Is information energy?

Thanks mgb_phys for bringing up an interesting topic. Thanks also to Pythagorean for the paper. Incredible stuff.
The question has never been whether thermodynamics arguments can be applied to computation. Obviously they can. We already agree on that:
The question still remains:
I'll further clarify. You can burn a book (please don't) and exploit the thermal energy from that process. This the energy is not coming from the information, it's coming from the chemical energy stored in the paper and print. You can use the electromagnetic energy in radio signals to do work. The energy is coming from photons, not from the information in the signal.

I'm not concerned with the energy in the medium in which the information is stored or transmitted. I'm concerned with the information itself. If it is energy, how can I extract or transform it to do work?

Please direct me to a source that directly says that information is energy. This is the third of fourth time I have asked you (Andy Resnick).

Last edited: Aug 3, 2010
7. Aug 3, 2010

### Andy Resnick

Re: Is information energy?

Ah, good- now you are getting somewhere.

Yes, let's say my information is a set of instructions for building a bomb. How much energy is 'stored' by that information? Clearly, by extracting the information I can perform a lot of work- build the factory, purify the explosives, blow up a bomb. That is, the *free energy* I gained from copying the information into my memory (reading the memory device), I can then use to perform *useful work*. The free energy of a system tells you the maximum available energy that can be converted into work.

Here's another example: I give you a working design for a 5 MW power plant. Because of the transmission of information from me to you, you are able to generate 5 MW of power able to perform useful work.

Clearly, we can transform the energy stored as information (by processing the information) and convert it into other forms- like a bomb instead of plans for a bomb. Or if you prefer, a working fusion reactor instead of plans for a fusion reactor.

Ok, so far? This is not referring to energy needed to build a bomb, this is referring to the energy needed to *know how* to build a bomb.

8. Aug 3, 2010

Re: Is information energy?

That is philosophy and you still haven't provided a source.

We agree that energy cannot be destroyed, so it follows that if information is energy, then it cannot be destroyed either. Consider the following:

On Monday, Alice asks Bob to create a message of any length and to store the information in his brain. The plan is that on Tuesday Bob will relay the message to Alice. The problem is that Bob has "en.wikipedia.org/wiki/Anterograde_amnesia"[/URL] and can no longer form new memories. On Tuesday, Alice goes to visit Bob to receive the message he created the previous day only to find that Bob no longer remembers the message.

Alice has access to all of the most advanced technology that the future of neuroscience has to offer. She thoroughly examines Bob's brain but finds no trace of the message since it was never transfered into his long term memory. The message was overwritten due to limitations in the brain's short term or working memory to process only a few chunks of information at a time.

The message has been irretrievably destroyed.[/COLOR]

That's philosophy. I can do it too. :biggrin:

A more scientific example of the loss of information is the [PLAIN]"en.wikipedia.org/wiki/Black_hole_information_paradox"[/URL]. If you can resolve the black hole information paradox such that information is preserved after the formation of a black hole (difficult), or you can provide a source stating that information is energy (should be less difficult), you'll certainly prove your case.

Last edited by a moderator: Apr 25, 2017
9. Aug 4, 2010

### Pythagorean

Re: Is information energy?

You're confusing the definition of information in the information theory context. The way you define information in your example can be destroyed (obviously), but that's a lot like saying "look I destroyed this window! I've destroyed matter!"

If all there was in the universe was matter, it would be frozen in time and there wouldn't be much of a universe. The universe, however, exhibits motion: change. The change of one particle in the universe would be meaningless to all the other particles if information wasn't exchanged between the particles. The change has to propagate if causality means anything.

Personally, I think Andy's being too accommodating to your application of information to human perception, as most people think that their abilities to sense the environment and respond to it are somehow fundamentally different from a particle's interactions with the rest of the universe. You're basically in a frame where some magic is happening if humans aren't bound by the laws of physics.

10. Aug 4, 2010

Re: Is information energy?

This is the point. I don't really want to discuss the information that we generally would call knowledge. I only introduced my little thought experiment because I thought it would make clear the fact that I mean physical information... and I thought it would be funny. (Sarcasm frequently doesn't play the way one intends in written word.)

I also thought I made it clear by calling it philosophy rather than science and by introducing the black hole information paradox.

Just to further clarify, by information I mean "en.wikipedia.org/wiki/Physical_information"[/URL] (or another commonly accepted definition in physics) without respect to the storage medium of the information.

Last edited by a moderator: Apr 25, 2017
11. Aug 4, 2010

### Pythagorean

Can we clarify something Andy? The thread title says information is energy. Do you think this is a little strong? I had alway taken your position to be informatoon is equatable to energy.

12. Aug 4, 2010

### cesiumfrog

Re: Is information energy?

That doesn't sound right. The energy content of information is not the amount of work the information can teach you to harness. Not if we're talking about thermodynamics and information theory, as the OP seems to intend, rather than philosophical word games.

I take it the basic idea is related to maxwell's demon: how much information we need to be able to compress a gas just by operating a shutter? Or how much work must it take to reset the demon's memory (discharging the previous information into the environment somewhere)? But it's been a while since I read those papers... can't remember if or how they fix an energy scale to an information bit..

You think your mind works by magic?!?
Uh, does that mean you think the physics of matter interactions cannot fully explain (or perfectly simulate) the behaviour of an amoeba? A nematode? A chimpanzee?

13. Aug 4, 2010

### Pythagorean

Re: Is information energy?

No, I was pointing out the fallacy that you're accusing me of.

14. Aug 4, 2010

### Andy Resnick

Yes, I can be quantitative: the free energy required to erase a bit of information is kT ln(2). The entropy associated with receiving a bit of information is k ln(2) (k is Boltzmann's constant).

It's the same concept as "heat is equivalent to work". That is, they are both forms of energy, but one cannot be freely converted into another without the loss/dissipation/entropy limits given by thermodynamics.

15. Aug 4, 2010

### Andy Resnick

Re: Is information energy?

That is true- I was trying to be careful not to confuse the two.

The *intrinsic* energy content of a message can be uniquely given by Kolmogorov's "algorithmic information" content of the message

http://en.wikipedia.org/wiki/Kolmogorov_complexity

Loosely, the amount of information in a given message is equal to:

1) the number of bits required to uniquely specify the message
2) the length of a computer code needed to generate the messgae as an output.

16. Aug 4, 2010

### Andy Resnick

Re: Is information energy?

Are you seriously asking me simply to provide you a reference that contains the phrase "information is energy"?

17. Aug 4, 2010

### Andy Resnick

Re: Is information energy?

Last edited by a moderator: Apr 25, 2017
18. Aug 4, 2010

### ACPower

Knowledge is proportional to information and it is well known that knowledge is power, thus since power is a rate of work, we can conclude that information is actually a rate of change of energy. We would need to integrate information over time to get an actual energy amount; it is not just what you know, but how long you know it.

19. Aug 4, 2010

Re: Is information energy?

Let's not speak so loosely. The word energy appears exactly zero times on that page. That being said, it's still an interesting topic. I hadn't previously heard of Kolmogorov complexity.

Yes. That was your claim in post #17 in https://www.physicsforums.com/showthread.php?t=419343", so I'd like a source that clearly states this. I have asked you repeatedly for one.

I have never failed to understand the material. If I have, please give me a specific example, and do your best to correct me. I find that comment unnecessarily combative. I fail to see what it contributed to the discussion.

The http://arxiv.org/abs/hep-th/0507171" [Broken] is the only thing that you have produced so far that actually supports what you have been claiming. I won't make the argument against Hawking myself, that would be silly. There are a lot of other papers that are unwilling to make the conclusion that the information is preserved.

Some papers:
http://arxiv.org/abs/0909.4143
http://arxiv.org/abs/0910.1715

This paper actually argues that the problem is not our (lack of) quantum gravity theory, but a problem of the singularity.
http://arxiv.org/abs/0907.0677

This one says that only by elimination of the singularity can information be preserved:
http://arxiv.org/abs/0901.3156

We could go back and forth finding papers to support this or that, but these papers are theoretical. They are all equally in question. A paper that has been experimentally verified would be appreciated. I'm not sure if that is an unreasonable expectation or not.

Last edited by a moderator: May 4, 2017
20. Aug 4, 2010

### Q_Goest

Sorry, but I have to ask a REALLY STUPID question....

Presuming information = energy (in some way as defined by others) then let's say I arrange baby blocks thus:

Then wouldn't the amount of information available in the blocks depend on how they are arranged?

Wouldn't the 'energy' contained by that information vary depending on how I stack the blocks? By putting more or less space between blocks, by changing the angles between them or stacking instead of sitting next to each other, by reading one side of a block instead of another, all of these factors would need to come into play in order for any of the information on the blocks to be interpretable, so every nuance would need to be prescribed mathematically in order for one to quantify the entropy and thus the energy contained by the information in the system of blocks. I have to believe it will quickly become infinitely imprecise to try and quantify what information is contained in the stack of blocks.

Sorry to appeal to intuitions here (which I agree is a terrible way of appealing to a scientific mind), but stacking blocks is no different than arranging information in any other way, which is to say I don't see any way we can ascribe a given amount of energy (entropy) to the way blocks are arranged (other than the obvious bits of entropy such as potential energy due to stacking, etc...).