Sigh. People who try to talk about science without using math should give up and become lawyers instead. Or psychologists. It's is like trying to study classic literature without the use of words. Or at least with really bad spelling. So as a professional douchebag (I have a master's degree.... in Science!), I would very much like to point out how stupid everyone else is now. I'm in a bad mood.
I recently purchased a Seagate 1.5TB hard drive for a mere $136 (with shipping) off of a site called tigerdirect.com, I can't believe the price is already this cheap! I'm gonna go download every movie/song in existence now..
You're off by a factor of about ten thousand, by my best guess. One single layer DVD is 4.37 gigabytes. Your hard drive is therefore sufficient for 300 to 400 feature length movies. More like 200 if they're double layer. Make that 60 blu-ray movies. Even cruddy low quality divx will barely get you up into the thousands. How many movies have been made since the beginning of the 20th century? And that's just movies, not TV shows (including not just sitcoms but every news or sports broadcast ever), music (well, that's going to be a lot smaller), or hell forbid AMATEUR productions (just imagine the amount of space used by youtube). Hell, I could fill up a terabyte hard drive just with japanese anime series that start with the letter "d", compressed to 200 megs per 20 minute episode if I wanted to.
The good news is though, your brain only has a capacity of a few petabytes, so there's not any point to downloading all the movies ever made even if you did have the space, because you wouldn't have the capacity to appreciate it. Figure it out yourself. 100 billion neurons. Only 10 billion are in the cortex. Each of which has the potential to have an axon going to any of a million of its nearest neighbors, but no more than a few thousand axons total. Let's say 10 thousand of its nearest million neurons. That's a binary decision, whether to have a connection to a given other neuron. In a typical connection set, making full use of capacity, each will then be connected to 10k of 1M neurons and so each neuron carries about 20 bits times 10k connections or 200 kilobits of information. Multiply that by 10 billion and you get 2 petabits. Ouch. Didn't even make it to a single petabyte. Well, those 90 billion non-cortical neurons are probably good for something.
mfratt, this is why you're wrong. The improvement from 5 megs to 2 gigs to a terabyte were on scales much smaller than the capacity of your own mind. The next step won't be. Individuals will never have a use for an exabyte until they stop being remotely human. Mark my words. I will still be correct 100 years from now. Or 1000.
Well with nanotechnology TB iPods won't be impossible.
Kind of like the statement "if you weigh 60 kilograms here on Earth, you'll weigh more than 80 kilograms on the surface of a neutron star". Let me give you a hint about what you can expect out of molecular scale devices. DNA. Do you know what its storage capacity is? Two bits per molecular unit. Thus (avagadro's number divided by 4) bytes per mole. A mole is 6 * 10^23. The molecular weight of one DNA chain segment is on average about 660 times the mass of a hydrogen atom (since it's different for the different base pairs). Of course, that's with MATCHED base pairs. The information is still stored if you only have one strand of the double helix. So 330 grams in a mole of DNA chain links. About 2 thirds of a pound. Two thirds of a pound of DNA thus has a storage capacity of roughly 1.5 times 10 to the 23'rd power. Terabyte iPods won't be impossible. True. But you're underestimating it by almost a trillion. But like I said. There's no point to having that capacity. It'll probably stop far below that level because the cost of continuing will far outweigh the benefits. The human brain can't appreciate something much greater than itself so if the utility is for entertainment purposes of that human brain, there's no point in it.
Then again, according to information theory, information can never be destroyed. This is a direct consequence of that there second law of thermodynamics.
There's as big a difference between information theory, the field of mathematics created by Claude Shannon which has been mostly been absorbed into Electrical Engineering, and quantum theory as created by a bunch of other guys, as there is between, say, integration by parts, and Civil Engineering. Information theory makes no such claims about the universe. It makes no claims about the universe at all. And you've got the causal relationship with the 2nd law of thermodynamics backwards. The second law of thermodynamics would be a direct consequence of the permanence of information. Destroying one bit of information and creating two bits of junk that don't give you any knowledge of the bit destroyed would satisfy the second law of thermodynamics just fine. The entropy aka information in the universe has increased, yet information has been destroyed. That's all the second law of thermodynamics says. The total amount of information has to go up. Not that any particular bit of information can't be destroyed and replaced by that quantity or more of different information. Of course it works the other way around. If you knew that information couldn't be destroyed, then the total quantity of information in the universe could certainly never go down.
Morel panic:
YES, it will stop. The information contained in a single atom is WAY, WAY less than you obviously think it is. You see, at any given temperature, information ACTUALLY HAS A MASS. Google the words "how much does the internet weigh" to see more about this. The fact is, that if ANYTHING at room temperature has a given amount of information in it, that information has a specific mass given by the bosemann constant as well as a few others (I don't remember exactly what the relation is - but the internet works out to be WAY more massive than a few million atoms, though still less than a speck of dust), so if it doesn't weigh at least a certain amount, it can't possibly contain more than a certain amount of information. Of course, as I said, it depends on temperature. In particular, it is directly proportional to the temperature. So information at liquid nitrogen temperature weighs a third as much per bit as it does at room temperature. This is a fundamental limit to the amount of information that can be stored PER atom.
And I guarantee you. It is a VERY loose upper limit. But like I said. You don't have any use for an exabyte of information anyway. Well, maybe some computer simulation could require that or more. If you wanted to simulate the biosphere of a planet for instance. Or describe a living human all the way down to the scale of Shroedinger's equation. But like I said, nothing for entertainment purposes. Nothing you'd be able to appreciate if you saw or heard.
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