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I am not a mathematician(IANAM), however I wish I could be.

My question: I often find this at the bottom of pages.

Page generated in 0.00013899803161621

Sometimes, I come across

Page generated in 9.0122222900391E-5

What does that time mean?

I tried searching Wikipedia for E and maths but found the e mathematical constant with a scary looking graph. My guess is E stand for Exponential or something and -5 is the power it is raised to. And the time is a really small number. But that doesn't make sense when compared to the other time in the question is 0.00013899803161621 bigger than 9.0122222900391E-5?

If it means x times $10^{-5}$, then 9.0122222900391E-5 will be 0.000090122222900391 which is smaller than 0.00013899803161621

  • 7
    In case anyone knows: where is this particular number coming from? There are a large number of google hits for it, many of which are not mirrors of this site, whereas (unsurprisingly) if I change the last decimal place by 1 in either direction there are no hits at all.2011-08-25
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    @Michael, for whatever it's worth it is the multiple of $10^{-18}$ that is closest to $189\times 2^{-21}$. Google also knows various multiples of $2^{-22}$ to a similar precision. They all seem to be values related to timing. Possibly related, I have come across a bug in some versions of Linux whereby the system time would be off by exact multiples of $\frac{2^{42}}{10^{9}}$ seconds. Notice that $42+22=64$...2011-11-12
  • 1
    So it is really a computer question, not a math question. If you want something other than wild speculation to the supplementary question "what does the E stand for?" you should try a computer site...2012-05-08
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    How in the world does this have 12K views?2013-03-12
  • 1
    How does this page have 125K views now??2015-12-28
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    I agree with @GEdgar. It's not a math question. So I suggest to delete it (or something similar).2017-07-18
  • 0
    How did it get so many views? It was linked from somewhere else...somewhere with lots of users.2017-07-18

3 Answers 3

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It means $9.0122222900391\times 10^{-5}$. This is known as "scientific notation".

  • 1
    Is the E an abbreviation for something?2010-10-07
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    On calculators that E is sometimes denoted "exp", which is short for "exponential". In fact, "exponential notation" is another name for "scientific notation"2010-10-07
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    This probably explain the "abuse" of $\log=\log_10$. :)2010-10-07
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    Well, only mathematicians the following is true: "Thou shalt not have another base before e", right? ;)2010-10-07
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    The reason for using this notation is it lets you represent very large or small numbers more compactly. For instance, writing 6.26068E-34 is much more convenient than 0.000000000000000000000000000000000626068, and easier to get an idea of its size without counting 33 zeros.2010-10-07
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    @AD.: I was really confused for a while, until I realized that you meant $\log_{10}$ rather than $\log_1 0$. :-)2010-10-08
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    @Andy The 11th commandment!2010-10-09
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    @Hans Lundmark: Of course, sorry :)2010-10-09
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    so `eN` or `e(N)` always means `10^N` or `10^(N)`??2018-11-18
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E-5 just means x 10^(-5) i.e. divided by 100000

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    if `-5` is positive, it's multiplication? it's only division when `-5` is a negative like `-5`??2018-11-18
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I have always taken the E or e to mean "exponent of 10." This construction parses in all modern computing languages as an IEEE754 double or single precision number.