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General Science => General Science => Topic started by: tangoblue on 12/10/2010 19:09:09

Title: Why is pi infinite?
Post by: tangoblue on 12/10/2010 19:09:09
I dont think this is strictly a science question but its kind of physicsy. Anyway, why is pie (as in 3.141592653...) infinite, and how did they get pie to be that number? finally, how many digits do they know pi up to? thanks.
Title: Re: Why is pi infinite?
Post by: LeeE on 12/10/2010 19:22:43
It's not so much that pi is infinite, meaning that it has infinite decimal places, but that it cannot be expressed as a fraction.  For example, the fraction 1/3 also has infinite decimal places when expressed as a decimal (base 10) but it can quite obviously be expressed as a finite fraction.

Nobody 'got' pi to be any particular number; it is the natural ratio between the diameter of a circle and its circumference, and by virtue of that, it is also the ratio between the square of a circle's radius and its area.

I'm sure a quick Google will tell you to how many digits pi has currently been calculated.
Title: Why is pi infinite?
Post by: Geezer on 13/10/2010 07:07:14
It is convenient to size circles based on two points that are 180 degrees apart (the diameter), but we could just as easily size circles based on two points that are at some angle other than 180 degrees so that the ratio was a nice round number, like 3 for example.

A possible downside to this would be the amount of mental gymnastics required to establish the diameter.
Title: Why is pi infinite?
Post by: RD on 13/10/2010 09:47:34
Quote from: Geezer on 13/10/2010 07:07:14
... ratio was a nice round number, like 3 for example.

You're not in Indiana Geezer ? ...
http://www.straightdope.com/columns/read/805/did-a-state-legislature-once-pass-a-law-saying-pi-equals-3
Title: Why is pi infinite?
Post by: Geezer on 14/10/2010 01:22:34
Quote from: RD on 13/10/2010 09:47:34
You're not in Indiana Geezer ? ...

Er, I don't think so, but I am in one o' them thar "I" states. It's not Iowa, or even Ohio, so it must be Idaho.

(Personally, I think it's the nicest one of all. Even the trees seem to agree.)
Title: Why is pi infinite?
Post by: Evie on 22/10/2010 18:32:24
I think that supercomputers have gotten the digits out over a trillion. Thanks Wikipedia!
Title: Why is pi infinite?
Post by: yamo on 24/10/2010 17:38:37
Is the magic of pi restricted to 2 dimensions?  Are there similar, related geometric ratios in 3 dimensions? 4, 5, 6, etc?  Since nothing exists in only 2 dimensions (everything exists in however many dimensions there are but nothing exists in only 2 dimensions), is pi real?
Title: Why is pi infinite?
Post by: RD on 25/10/2010 02:29:20
Quote from: yamo on 24/10/2010 17:38:37
Is the magic of pi restricted to 2 dimensions?  Are there similar, related geometric ratios in 3 dimensions?

A sphere is 3D ...

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2F0.tqn.com%2Fd%2Fmath%2F1%2F0%2FI%2FF%2Fspherer.gif&hash=5b838dbd219ef93ac98bc6438569a22b)