Sometimes, when you measure things, you need to really really be very detailed about how much you have, and other times it’s more of a ballpark figure. One of my friends insists in measuring everything to the meniscus in the kitchen, even when adding a tablespoon to 10 cups of something else. It doesn’t matter on that scale.
In the lab, it depends on your equipment. You can pipette 5 microliters with the P200 Gilson, or 5.0 with the P20, or 5.00 with the P5 (NB. I didn’t look this up so I might be wrong in the details, but you get the idea.) 1
In adding things, you’re going to want to go with the lowest number of decimal points of the numbers you start with2. Adding 4.88 microliter to 10 microliter gives you 15 microliter, not 14.88. This has to do with the above pipettes. The bigger one can’t tell the difference between 10.04 and 9.99, so it’s just “10”. The smaller one can tell you have exactly 4.88, but if you don’t know whether you’re adding that to 9.99 or 10.04, you can’t say that you have 14.88 microliters in the end. You might have a bit more or less. So, 15 is the closest you can get to the actual amount in your tube.
Summary: 10 + 4.88 = 15 (and not 14.88)
You can’t just add extra numbers after the decimal point. This 15 is not the same as 15.0
In multiplying numbers you need to stick with the lowest number of significant digits2. If you have 17.25 ml of a 7.7 M solution, you have 1.3 × 10^2 mmol altogether (not 132.825) because 7.7 only has two significant digits.
Summary: 7.25 × 7.7 = 1.3 × 10^2 (and not 132.825)
Again, you can’t just add extra significant digits. You don’t know if it’s 1.30 × 10^2 or 1.33 × 10^2
So (and here’s the point of all of this) why are version of the World Wide Web expressed in two significant digits if we went straight from web 1.0 to web 2.0?
Because it’s not counted that way. Far too much detail here, but basically the number before the dot indicates which major release it is (a change here means the internals have been heavily messed with), and the number after which minor release. There is often a third number (e.g. R is currently 2.9.2), where the third number is bug fixes.
Usually the shift from 0 to 1 means that the version is considered stable. This means that a certain amount of timidity results in this for one software package: 0.999375-31.
This is a great summary on significant figures, which always becomes an issue in first year physics (and I’m sure other science) labs. As for software programs – Bob seems to have covered it.
I know it’s releases. Still, why go from .0 to .0?
Shouldn’t we be on web 2.4 by now?
Bob’s a nerd and missed the point.
I want my Web 2.4.
What I’d really want is a Web 2.47. I like the sound of it. Maybe if we go back and re-measure the whole web thingy with more accurate tools? (or precise, which was it now?)
If it’s a number less than 10, aren’t we supposed to write it out in full?
Web two point four seven. Hmmm, boats ain’t being floated.
hmm…i thought maybe it just sounds cooler/more pro if it was web 1.0 or 2.0, like “007”. but Bob’s explanation of it makes more sense.