Maximum Capacity

Here are some dictionary definitions of Capacity:

• The ability to hold receive or absorb
• The maximum amount that can be contained
• Ability to perform or produce
• The power to learn or retain knowledge
• Innate potential for development
• Position or Authority to do something

According to the Canadian Building Digest “Elevator cars are rated according to maximum allowable weight and number of passengers… Usually, the maximum loading of an 1150 kg elevator will not exceed 13.”
So a 1150 kg elevator will have a maximum capacity of 13 people.
What about a computer? How many human minds can we fit in a computer?
It all depends on how you define a mind. You might start by trying to model a brain
A human brain contains around 100 billion cells. If we imagine that each cell is either on or off (firing or not firing) we could say that each cell could be represented by a bit, or 1 or 0.
A human brain would therefore need 100 000 000 000 bits or 12 500 000 000 (12.5 billion) bytes of memory to be stored on a computer. This is the same as about 11.6 Gb.  In other words, by this model, I could fit two brains on my 30Gb iPod.  (I have written this in August 2005. No doubt in a couple of years time the capacity of my iPod will appear laughably small.)
How many human minds could be stored on an iPod? Is the answer still 2?
No.  In fact, to be honest the previous answer is not really 2.  It assumes an awful lot about the structure of a brain, not least the fact that a frozen snapshot of the states of a set of neurons captures all the data stored therein. It also says nothing about the processing performed by the brain that gives rise to a mind.
For example, each neuron is connected to thousands of other neurons, via trillions of synaptic junctions.  Modeling this bumps up the numbers of bits required tremendously, and blows the possibility of iPod storage out of the water. 
Current estimates of brain capacity are expressed in Terabytes ie 1 x 10^12 bytes. Coincidentally, that is about equal to the current estimate for the number of people who have ever lived. So that means we would need about 1x10^24 bytes to store the combined experience of the human race, assuming each brain has a maximum capacity of 1 terabyte.
That’s a lot of memory.  But suppose we apply Moore’s law to memory storage, and assume that capacity doubles roughly every two years.
That suggests that by the year 2095 one could purchase an iPod capable of storing the memories of everyone who has ever lived.
That’s certainly something to think about.


Next: The Twin Slits Experiment