Biggest science or math pet peeve

[micromass]

That's because you're determined to stick with PEMDAS, so you need your implied parenthesis. Whereas, I never learned PEMDAS so I'm free to say in this case we do the division last. As I have no a priori rule that operations must be done in a set order it doesn't upset my mathematic apple cart

Every notation you use and introduce has their own precendence rules. And those precedence rules need to be introduced whenever the notation is introduced. Just because schools introduce PEMDAS before they introduce the notation $\frac{a}{b}$ or $e^{2\pi i x}$ doesn't mean that PEMDAS are in any way invalid, or that you can't just make a consistent set of rules easily that takes into account this notation.

 

[jack action]

I never learned PEMDAS so I'm free to say in this case we do the division last.

«La mia macchina è rotta.»

I never learned Italian so I'm free to say in this case that sentence means «I'm the most beautiful man alive.»

Couldn't care less what Google translate says.

 

[Mark44]

What I wouldn't do is insist on PEMDAS and then have to explain:

$\frac{a+b}{c+d}$

And why you do the additions before the division. That's what I as a 15 year old would have taken exception to! I fail to see it ad a logical consequence of PEMDAS.

But that is a fraction, not a division. The horizontal bar adds meaning to the division implied (i.e. the parenthesis, as told by @Mark44 earlier).

A fraction implies division.

 

[Mark44]

It adds meaning to how this equation must be evaluated.

Nitpicky, I know, but the thing you're talking about is an expression, not an equation.

 

[vela]

Nitpicky, I know, but the thing you're talking about is an expression, not an equation.

Heh, I was about to post that was one of my pet peeves.

 

[russ_watters]

There may be more on this forum but the brow beating I've taken would deter most from uttering a word in my defence!

Since you are soliciting more opinions, I agree......with @micromass and @Mark44!

I guess I have a minor pet Pete about calculators not always being clear about which convention they use, but if we'really going to go there, I have a long list of Excel pet peers too...and also the autocorrect on my phone is trying to drive me insane.

 

[russ_watters]

But I should say that I have no memory of learning the order of operations in my elementary school years. But I don't have a good memory so I can't remember how I did it!

I don't either. I had to Google "PEMDAS" before adding my 2 cents. The rule gets converted to instinct and ultimately forgotten after a while.

 

[TeethWhitener]

The expression in this article of the link seems clear-cut to me.

Wait, so does this mean that we can't write binomial coefficients inline as $n!/k!(n-k)!$ ? Because $n!/(k!(n-k)!)$ looks atrocious to me. Just my two cents.

 

[TeethWhitener]

One small peeve of mine that's starting to come up more and more in chemistry is the insistence on using IUPAC nomenclature. Sometimes it's good, but for reaction following it can be a pain. For instance, an example I ran into recently involved a Heck addition of perfluorobutyl iodide to ethylene. You get an ethylene attached to a perfluorobutyl group. Some older authors call this compound perfluorobutyl ethylene, which is immediately understandable and makes it clear which groups were combined and how. But the IUPAC name for this compound is the hideous 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, which gives essentially no information about how it was derived and requires at least several brain cycles (and possibly pencil and paper) to decipher that, yes, it's just a perfluorobutyl chain attached to an ethylene.

 

[sophiecentaur]

Ye Gods. 184 posts. We are a grumpy lot, aren't we!

 

[JaredJames]

Ye Gods. 184 posts. We are a grumpy lot, aren't we!

Well, about 5 peeves and 9 pages of arguing why perok's peeve is wrong.

 

[OmCheeto]

Ye Gods. 184 posts. We are a grumpy lot, aren't we!

Educators OmCheeto should fill this thread!

I have so many...
Though, I recognize that most of mine are my own personal problem.
But still, even the ones that aren't that personal, still peeve me.
I think most are very, very old, from my younger days...

Back in college:

Om; "What is the proper 'chemistryish' name for water"?
Chemistry book; "Water"
Om; "That's stupid. Why does everything else have a logical name?"
Chemistry book; "Wait until you get to hydrocarbons. Ha Ha!"
Om; "Grrrrrr..."
[ehr mehr gerd.... I ain't studyin' any more chemistry until you kids get your, um, stuff together...]
​

More recently:

Om; "Who and when was it decided to change the Latin name of the "Guppy"? I learned that when I was 7, and now I see it's been changed."
Botanists; "We did".
Om; "When"?
Botanists; "Um..."
Om; "And why"?
Botanists; "Well..."
[ehr mehr gerd... see: Synonyms]​

I could go on all day...

Om; "Oh, so I can't say; "Degrees Kelvin", to reduce the confusion of whether or not I'm talking about "the man" or "the weather"?"
Pedants' "No. We have spoken..."
Om; "Grrrrrrrrr..."​

ps. I recently got interested in geology, after trips to Ceres and Crater Lake National Park, and I think geologists may be the worst of all.

Om; "Where did you guys come up with these names"?
Geologists; "We made them up."
Om: "And the numbers?"
Geologists; "Eyeballing".
Om; "I like your honesty. ps. Do you ever get jealous of that "Howard" guy"?
Geologists; "Kind of".​

 

[Mark44]

Wait, so does this mean that we can't write binomial coefficients inline as $n!/k!(n-k)!$ ? Because $n!/(k!(n-k)!)$ looks atrocious to me. Just my two cents.

If it's written like this, no problem: $\frac{n!}{k!(n - k)!}$, but as you wrote it the first time, it's ambiguous.

The main problem with PEMDAS is that, IMO, it's sort of a work in progress, that hasn't been as well thought out as, say, what the computer science folks have done in specifying the precedence of operators in programming languages, and specifically the languages that stem from C. These precedence tables not only specifiy which operations should be performed before which others, they also specify the associativity of each operator, so that a + b + c should be evaluated left to right, the same as if it were written (a + b) + c. Note that on computers, addition is not necessarily associative; due to overflow or underflow, (a + b) + c might give a different result from a + (b + c).

It seems to be fairly well agreed on that for the addition and subtraction operations (the A and S in PEMDAS), the operations are at the same level of precedence and should be performed left to right.
In a footnote on the Wiki page for Order of Operations (https://en.wikipedia.org/wiki/Order_of_operations), emeritus Berkeley math professor George M. Bergman has this to say: (https://math.berkeley.edu/~gbergman/misc/numbers/ord_ops.html)

For expressions such as a−b+c, or a+b−c, or a−b−c, there is also a fixed convention, but rather than saying that one of addition and subtraction is always done before the other, it says that when one has a sequence of these two operations, one works from left to right: One starts with a, then adds or subtracts b, and finally adds or subtracts c.

IOW, 3 + 4 - 2 should be thought of as meaning (3 + 4) - 2, yielding 5. Similarly, the expression 3 - 2 + 4 should be thought of as meaning (3 - 2) + 4, again yielding 5.

What is not well accepted is that multiplication and division (the M and D of PEMDAS) should be treated as having the same precendence, and be evaluated left to right, making these operations consistent with the treatment of addition and subtraction.
Another quote from the George Bergman footnote (italics added by me):

Presumably, teachers explain that it means "Parentheses — then Exponents — then Multiplication and Division — then Addition and Subtraction", with the proviso that in the "Addition and Subtraction" step, and likewise in the "Multiplication and Division" step, one calculates from left to right. This fits the standard convention for addition and subtraction, and would provide an unambiguous interpretation for a/bc, namely, (a/b)c. But so far as I know, it is a creation of some educator, who has taken conventions in real use, and extended them to cover cases where there is no accepted convention.

With no clear-cut convention regarding expressions with multiplication and division, particularly when written inline, you run into problems with expressions as simple as 1/2x. If we hold that multiplication and division are at the same precedence level, and should be evaluated left to right, the expression 1/2x is the same as (1/2)x. OTOH, a number of prominent textbooks, including "Course of Theoretical Physics" by Landau and Lifshitz, as well as the "Feynman Lectures on Physics" interpret 1/2x the same as $\frac 1 {2x}$.

Another area where PEMDAS is deficient with associativity not clearly spelled out is in stacked exponents. Per this Wiki page

https://en.wikipedia.org/wiki/Order_of_operations]Stacked[/PLAIN] exponents are applied from the top down, i.e., from right to left.[/quote]
However, both Microsoft Office Excel and Matlab R2015B evaluate 2^3^2 (i.e., $2^{3^2}$) as if written (2^3)^2 = 64 rather than 2^(3^2) = 512.

 

[late347]

From top to bottom. What's on the top must be computed first.

lets imagine that we have expression as follows

$2^{2^{2^{2}}}$

why should it be through pemdas, that one calculates from the top right, towards bottom left?

Are you supposed to initially judge that the leftmost number at the bottom, two = "the base number". Therefore, essentially, all the others two's are some sort of powers as themselves. I suppose it makes sense like that. Is that a real math term anyway "base number"?

Usually people simply speak 2 squared (for the case of $2^2$. And not e.g. 2 as the base number, and 2 as the exponent.

 

[Mark44]

lets imagine that we have expression as follows

$2^{2^{2^{2}}}$

why should it be through pemdas, that one calculates from the top right, towards bottom left?

PEMDAS doesn't say anything about this, since there are no other operations other than exponentiation. The convention, not always honored (see my previous post) is that the order of evaluation (the associativity) is from right to left.

Are you supposed to initially judge that the leftmost number at the bottom, two = "the base number". Therefore, essentially, all the others two's are some sort of powers as themselves. I suppose it makes sense like that. Is that a real math term anyway "base number"?

We usually say just "base". In $2^8$, the base is 2 and the exponent is 8.
In the expression you wrote, each 2, except the rightmost one, is the base for some exponential expression.

Usually people simply speak 2 squared (for the case of $2^2$. And not e.g. 2 as the base number, and 2 as the exponent.

 

[Mark44]

More recently:
Om; "Who and when was it decided to change the Latin name of the "Guppy"? I learned that when I was 7, and now I see it's been changed."
Botanists; "We did".
Om; "When"?
Botanists; "Um..."
Om; "And why"?
Botanists; "Well..."

I'm not a botanist, but I took one field botany class many years ago, purely for interest, and have managed to hold onto the scientific names of quite a few plants. I've noticed that the scientific names of several plants have changed, including that or Oregon grape, a shrubby plant that grows in my area. It used to be Berberus aquifolium, but now it's Mahonia aquifolium, so they changed the genus the plant belongs to.

They've even changed the names of at least one family - Compositaceae, the family that sunflowers, daisies, and asters belong to. It seems to now be Asteraceae, although I see from wikipedia that the older name is still valid.

 

[Bystander]

That's the difference between "Linnaean" and "cladistic" taxonomies.

 

[TeethWhitener]

If it's written like this, no problem: n!k!(n−k)!\frac{n!}{k!(n - k)!}, but as you wrote it the first time, it's ambiguous.

Sure, but I imagine that if most mathematicians or scientists saw $n!/k!(n-k)!$ in a paper, they'd probably automatically associate it with a binomial coefficient immediately, rather than thinking it means
$$\frac{n!(n-k)!}{k!}$$

 

[Mark44]

Sure, but I imagine that if most mathematicians or scientists saw $n!/k!(n-k)!$ in a paper, they'd probably automatically associate it with a binomial coefficient immediately, rather than thinking it means
$$\frac{n!(n-k)!}{k!}$$

Probably so, but if this appeared in a paper, it would likely be nicely formatted as $\frac{n!}{(n - k)! k!}$.

 

[DrClaude]

In another thread, I just got reminded of another pet peeve that is science related, videos like this:

Image source: at 02:30

It's an audio-visual medium, use the audio! Talk to me! If I want to read, I'll look up a text. And don't force me to read at a given speed.

 

[Kevin McHugh]

Here is a major pet peeve of mine. I had to take QM in my senior year for my BS in Chemistry. Even though I had two semesters each of calculus and physics, I was totally unprepared to fully appreciate QM. I lacked the background in matrix theory, operators and Hamiltonian/Lagrangian formalism to fully grasp the concepts in the course. Of course we were given a cursory glossing over of these topics, but not enough to fully appreciate the course material. I have since gone back and started reading QM by Shankar. The treatment of this material is very rich. I love this text!

 

[Ben Niehoff]

That and the date convention. How does 3/1/15 for 1 march 2015 make logical sense... at all?

Because we actually say "March 1st, 2015", not "1 March 2015". Although I think the date format 2015/03/01 would make a lot more sense.

 

[micromass]

Because we actually say "March 1st, 2015"

I know you say it. My point is that there is no logical reason to say it like that.

 

[Bystander]

"March 1st, 2015", not "1 March 2015".

no logical reason to say it like that.

When asked for my birth date, I reply, "Six March forty-seven."

 

[Ben Niehoff]

When asked for my birth date, I reply, "Six March forty-seven."

Are you American? I am pointing out a dialectical difference. British people do say the day first.

 

[micromass]

Are you American? I am pointing out a dialectical difference. British people do say the day first.

How would you say the US independence day?

 

[Ben Niehoff]

How would you say the US independence day?

We say "4th of July", and it is a fossilized phrase, like all your phrases in Dutch that start with 's.

 

[micromass]

We say "4th of July", and it is a fossilized phrase, like all your phrases in Dutch that start with 's.

We don't have phrases that start with 's, but we have words starting like that.

 

[Ben Niehoff]

We don't have phrases that start with 's, but we have words starting like that.

Sure, but you and any linguist would probably agree that the genitive case no longer exists in Dutch.

 

[micromass]

Sure, but you and any linguist would probably agree that the genitive case no longer exists in Dutch.

Fortunately.

 

[Bystander]

Are you American? I am pointing out a dialectical difference. British people do say the day first.

... and, Americans who've been in uniformed service.

 

[Ben Niehoff]

... and, Americans who've been in uniformed service.

And they also say things like "fourteen hundred hours" for 2:00 pm, which is total nonsense. :P

 

[micromass]

And they also say things like "fourteen hundred hours" for 2:00 pm, which is total nonsense. :P

Why is it nonsense? We tend to have the same pattern in dutch, but not for hours.

 

[Ben Niehoff]

Why is it nonsense? We tend to have the same pattern in dutch, but not for hours.

Because it does not literally mean that 1400 hours have passed since midnight?

 

[jim mcnamara]

I'm not a botanist, but I took one field botany class many years ago, purely for interest, and have managed to hold onto the scientific names of quite a few plants. I've noticed that the scientific names of several plants have changed, including that or Oregon grape, a shrubby plant that grows in my area. It used to be Berberus aquifolium, but now it's Mahonia aquifolium, so they changed the genus the plant belongs to.

They've even changed the names of at least one family - Compositaceae, the family that sunflowers, daisies, and asters belong to. It seems to now be Asteraceae, although I see from wikipedia that the older name is still valid.

@Mark44
The reason: botanists love to cubbyhole plants taxonomically. Until recently there was only morphology usually of the flower and the seed/fruit (Angiosperms) to use to categorize. So, if you have ever seen a lotus plant and a water lily you would think, based on floral morphology, they were at least "first cousins". Then along came DNA sequencing data. Turns out the plane tree (Sycamore in the US) is the closest living relative of the lotus.
Fruits:
https://pixabay.com/static/uploads/photo/2015/07/06/05/14/lotus-fruit-833012_1280.jpg
http://publicdomainvectors.org/en/free-clipart/Sycamore-vector-graphics/32210.html

There a lot of other data tidbits like this that drove the taxonomically inclined into a cladistic nomenclatural frenzy. Applies to zoologists, too. The giraffes of the world spontaneously combusted into multiple species a short while ago:
http://www.smithsonianmag.com/ist/?next=/smart-news/there-are-four-giraffe-species-not-just-one-180960411/

I hope it wasn't painful for those tree-tall guys on the savanna.

Defining species can be a painful, messy and somewhat inexact science. Look up Switchgrass -
Panicum virgatum in wikipedia.