Returning to the topic of infinitesimal numbers, which is an example of a surreal number, here is what i have learned:
To create these 'surreal numbers' first you must define what a number is, mathematically. Now this may come as a surprise to you, but numbers are fairly hard to define. This definition is just one of many, and it goes something like this:
A number is defined by two sets of numbers, where no member of the 'left' set is greater than or equal to any member of the 'right' set.
Math wise it will look like this: x --> [XL,XR]; XL ³ XR
(Since every number corresponds to two sets the L and the R are used to designate the two "X" sets from each other when not side by side.)
Now, at first you may have noticed that this definition is self-referential - it uses sets of "numbers" to define numbers, but this can be overcome by starting with an "empty" set of numbers.
So, the first "number", we shall call it a since we don't know what the number is yet, would be:
- a --> [ { }L,{ }R ]
Does it fit the definition? It has two sets of numbers, although both sets are "empty". So are any numbers in the left set greater than or equal to any number in the right set? No, there are no numbers in the left set (greater than, equal, or otherwise).
Now we have a single number with which to define more numbers, they are:
- b' --> [ { },{a} ]
- b'' --> [ {a},{ } ]
- b''' --> [ {a}, {a}]
Do they also fit the definition? The left set b' has no numbers, so there can be no numbers that are greater than or equal to a (the only number in the right set of b'), ergo, it fits the definition and is a number. Likewise, the a in the left set of b'' cannot be greater than or equal to any number in the right set of b'' because there are none.
At this point b''', as a number, cannot be determined, because there is no way of checking whether or not a is greater than, less than, or equal to a. It sounds funny, i know, but we have to define at least one relationship between numbers in order to define numbers themselves. It has only worked so far because of the "empty" set has no numbers, and we can compare something with nothing without relationship.
Do not fear, tomorrow i will define a relationship and we can continue with this. OK now you can fear. :)
P.S. Interesting to note, there were no actual numbers used in this post, like a "1" or a "2". It has all been letters and symbols
Recent Comments