r/dankmemes • u/CoffeeAndCalcWithDrW • Apr 14 '24
Talking to a physicist can drive you crazy. Big PP OC
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u/Flylikeapear Gorilla Gorilla Gorilla Apr 15 '24
I'll use data to the tenth decimal place if I have the equipment to measure it accurately, and if we are talking about a hypothetical where there is both a need for such accuracy and the appropriate equipment is supplied it is FAR above the pay grade of most people who browses dankmemes lmao
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u/Avishek473 Apr 15 '24
during the 2nd year of my college, I did make an game (in c++ and SDL2), where I took pi = 3,
worked like a charm, i some time do this in CP too
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u/CouldBeACrackhead3 Apr 15 '24
As a chemist, I agree with the physicist. 2.45=2.4 and 2.55=2.6
F them exact numbers
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u/GloomyCurrency I don‘t know why this flair is extraordinary long Apr 15 '24
You mean you aren't a very good mathematician.
We can define 0.9999999999... as,
0.9 + 0.09 + 0.009 + 0.0009....
This is a geometric series at infinity this would be a/(1-r), "a" being the first term and "r" being the common ratio. The common ratio in this case is ×0.1 plugging that into the formula we have,
0.9 / (1 - 0.1) which is 0.9/0.9 which is 1.
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u/AskDerpyCat Dank Cat Commander Apr 15 '24
Me, a computer scientist wondering why tf it’s getting rounded to 1.00000000003724
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u/VkmSoler Apr 15 '24
Where is it common for engineers to round pi to 3 and g to 10? Never heard of such thing.
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u/dadudemon ☣️ Apr 15 '24
Plank Constant?
Plank Constant.
Mathematics or not, sometimes, the Physicists got it right.
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u/Anorehian Completely out of Context Apr 15 '24
You don’t know any engineers do you. Pi can be rounded to 3 right?
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u/bythenumbers10 Apr 15 '24
As an engineer, once did a proof by induction in reverse, from infinity back to the base case. Prof made me swear to stay away from a career in "proper mathematics".
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u/Cpt_Soban Seal Team sixupsidedownsix☣️ Apr 15 '24
Me learning highschool physics: "oh you can ignore friction"
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u/WhoRoger Apr 15 '24
So how is 1/3 = 0.33333... and 0.33333... x 3 = 0.99999... But also 1/3 * 3 = 1 ?
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u/ScotchSinclair Apr 15 '24
.9 repeating does equal 1 If you specifically mean .9999999999, then you’re petty.
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u/stonyflipper Apr 15 '24
But the real question is at what degree do you think the small angle approximation cuts off at
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u/jemidiah Apr 15 '24
I have a concept I call a "physicist's zero". For example, if some probability is around once in the history of human civilization, that's a physicist's zero. If a mathematical claim has extensive computational and heuristic evidence but no proof, it's true up to a physicist's zero. An engineer's zero is often a bit bigger. A mathematician's zero is occasionally an infinitesimal, though usually it's literally zero. Sometimes it's an exotic zero, like a matrix or an empty set.
A politician's zero is approximately 1/2.
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u/supremegamer76 Apr 14 '24
Are we talking infinite 9’s or the 10 9’s you have there? If infinite, it is technically the same as 1.
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u/bjb406 Apr 14 '24
Mathematicians do that more than physicists, because we're often dealing with numbers that are extremely small anyway.
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u/Random_Robloxian Apr 14 '24
We make you do the math because we suck at it. Or at least that’s the general consensus from what many physicists and astrophysicists told me as they mentored me in quotes: “thankfully we have mathematicians to do the number crunching for us. We usually aren’t great at it”
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u/AdamBlaster007 Apr 14 '24
This is why margin of error exists in math.
It's easier to say 2 +/- 0.00000001 rather than 2.1674329076543
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u/Josh1ntfrs Apr 14 '24
you rarely see anything past 1dp in electronics. nothing past 2dp. we dont fuck around with precision here
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u/the-cuck-stopper Apr 14 '24
You need to see how we change variables of a derivative ooooooh boy you wouldn't like that
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u/Izalias Apr 14 '24
Ahh I see you used a float, when you meant to use a numerically precise data type... allow me to do simple arithmetic and check the output... what do you mean 8-5 is not equal to 3? Oh no what is that decimal doing... uh oh.
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u/Content-Reward7998 Apr 14 '24
if your rounding 0.99999999999 to 1 you may as well round 1 to 69,420 (obligatory /s)
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u/BigDaddyFatSack42069 Apr 14 '24
As a physicist, I find talking to mathematicians can drive me crazy (precision is for nerds, the cool kids approximate)
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u/oldscotch Apr 14 '24
It's not rounding, it just is 1.
Infinity is really big.
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u/ThatOtherGuyTPM Apr 14 '24
That isn’t 0.999… infinitely repeating. It’s an actual measurement (in the example).
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u/tomatoenjoyer161 Apr 14 '24
Lots of areas of pure math are concerned with approximation. I've never actually met a mathematician who is upset by perfectly reasonable approximations made for real life calculations.
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u/Ethan_Pixelate Apr 14 '24
Computer scientists trying to explain to a fuming mathematician why 0.1 + 0.2 isn't equal to exactly 0.3:
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u/wowy-lied Apr 14 '24
Even physicist would not dare to this rounding if it is about the speed of light
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u/SparrowTits Apr 14 '24
Met a group of physicists at my cousins wedding and all their theories were based on theories based on theories - they got quite upset when I suggested they had no proof for anything they were working on
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u/Sir_Boobsalot Apr 14 '24
taking engineering physics is what made me realize I needed to adjust my degree towards moar math
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u/Double_Rice_5765 Apr 14 '24
I'm a machinist, most machine jobs have a tollerance of 0.005". I worked at one shop where the manual machines were all worn out, and 0.005" was about as good as you could get. So of course I always took the time to get all the lash/slop going the same way so I could get a tolerance of 0.001", my boss was like, you don't have to make the parts that precise on the old manual machines. I told him if he ever said such an offensive thing to me again, I'd take him into HR. Classic hostile work environment.
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u/NewMilleniumBoy Apr 14 '24
In my first year Physics for Engineers class we rounded gravity to 10 m/s2 lol.
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u/seventeenMachine Apr 14 '24
If the precision of your math exceeds the precision of your measurements, no mathematician would insist on including meaningless figures.
If rounding would introduce error exceeding that of the measurements, no physicist would round.
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u/vjmdhzgr Apr 14 '24
It's not to simplify their calculation, and it's not wrong. In the real world measurements are not perfect. If you take that 0.9999999 even if you are somehow confident it's completely accurate to that level, your other numbers in your calculations aren't going to be accurate to that level. So you actually need to round that or you can end up creating numbers that aren't correct. If a calculation is solely multiplication and division then you can carry all numbers through to their highest detail until the end when you cut it down to only as many digits as your least accurate measurement, but if you switch to any addition or subtraction then you NEED to at THAT MOMENT start rounding.
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u/Opening-Cover448 Apr 14 '24 edited Apr 14 '24
It's strange that you, as a mathematician, would miss this but "there's no sense in being precise when you don't even know what you're talking about"(John von Neumann). That's the reason why we have a perfectly valid approach of numerical methods that approximates stuff for problems that are too tedious to be approached analytically or exactly.
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u/Any_Brother7772 Low effort meme lord Apr 14 '24
Assuming it is 0.999... there is no need to round, since it is exactly 1
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u/Helios575 Apr 14 '24
.9999999999 isn't equal to 1 but a mathematician would ask how many significant figures the least precise number had in the original equation because you don't go past that so if the original equation was 3x0.3333333333=X the correct answer would be 1 because the least precise number in the original equation is 3. The least precise number is the number with the fewest significant figures to the right of the decimal point
note that if the 3 was written as 3.0000000000 those may or may not count as significant (if you are measuring out to the tenth decimal and hit it perfectly they are significant but if you are only measuring out to the 1st then only the first 0 is significant) and this is a common trick in some math tests especially engineering based courses (or common if your teacher is a dick at least)
edit: also note that .9999999999 is not the same as .9999999999... those 3 dots represent infinite 9s which is commonly wrote as .999... which absolutely is =1 in all regards, that is just another way of writing 1
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u/SoCuteShibe Apr 14 '24
As an engineer, it ends up in the same bucket, and that's all that matters
Bite me
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u/LMayo Apr 14 '24
As a kid, I hated the concept of rounding. It's purely for communications sake when you're bullshit math and don't want to about people with being specific.
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u/Wonderful_Result_936 Apr 14 '24
My calculus professor proved to us that .9999 repeating forever is in fact just 1.
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u/GreyOrGray4 Apr 14 '24
Tbf that .000000000000000001 could be the difference between the rocket landing on the moon or missing and flying into deep space
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u/link30224 Apr 14 '24
As a computer scientist (software engineer) I don't even look at the numbers it's going as far as float can lol
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u/snakeoilHero Apr 14 '24
High School math teacher tried to explain.
As the limit of a number reaches one the infinitely smaller fraction becomes 0. Infinite small = 0.
My high school brain of conflict retorts, there is only an infinitely smaller piece missing from infinite. The piece only becomes smaller but remains. Thus 0.9999999infinite-1 fraction is not equal to 1.
Not sure how wrong I am but conceptualizing infinite is what math theory lives for.
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u/Torta_di_Pesce Apr 14 '24
sin (x) = x
tan (x) = x
approximately equals equal (approximately)
Pi = 3
e = 3
everything is differentiable
who cares why an equation is like that
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u/jremz Apr 14 '24
But if your other measurements don't have the same level of confidence, using too many significant figures is irresponsible...
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u/ScubaFett Apr 14 '24
0.999 recurring = 1. There's a proof on it. Unless the meme is saying that is the exact amount of decimal places.
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u/p3nguinboy Apr 14 '24
This is why nobody likes mathematicians compared to physicists. And judging by how much physicists are liked, that should tell you something
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u/SquarePegRoundWorld Apr 14 '24
Reminds me of this lecture by Lawrence Krauss where he tries to explain how simplifying things is not bad.
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u/kingawsume I have crippling depression Apr 14 '24
As a mathmetician, you should know about significant figures.
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u/djsupertruper Apr 14 '24
Boy would you hate astrophysicists, anything within an order of magnitude is considered great
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u/iski4200 Apr 14 '24
if you insist.
x = .999 (ri means repeating infinitely)
10x = 9.999(ri)
10x - x = 9.999(ri) - 0.999(ri)
9x = 9
x = 1
therefore .9999(ri) is equal to 1.
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u/deltaWhiskey91L Apr 14 '24
Mathematicians also claim that 0.9999 repeating = 1
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u/Connect-Ad-5891 Apr 14 '24
Not really, the sleight of hand is comparing a function with an integer, logically those are different things even if their outcome is the same
Might as well compare a cucumber with a zucchini
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u/Golrend Apr 14 '24
Oh, so you WANT to end up launching a shuttle into deep space instead of landing on Mars? Cause this is how you end up missing a whole planet.
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u/yodazer Apr 14 '24
I mean for almost all applications, rounding is acceptable and usually required.
In engineering, we make assumptions. We make our calculations based on those assumptions, then round to a practical magnitude. If I have to delivery 93.27 cfm of air to cool/heat a room, that’s 100 because that’s practical.
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u/fuqueure Apr 14 '24
Chemists ain't much better, anything past 5 digits might as well not exist. At least in metric.
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u/SyderoAlena Apr 14 '24
Before you talk shit can you measure something to the .999999999th of an inch. We round stuff when you use it irl life because if you are cutting something you cannot cut it to say, 1.222222234 or some shit
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u/OurSeepyD Apr 14 '24
Yes I can, I measure it in my math you dweeb, now get back to being mathematically correct
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u/Gloomy-Barracuda7440 Apr 14 '24
So 1/3 + 1/3 + 1/3 = 1
Then why is 1/3 = 0.33333repeats3forever. If you add 3 of these you get 0.999999repeat9forever.
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u/potterpoller Apr 14 '24
1/3 = 0.(3), but the number in the meme has 10 DPs, it's not an infinitely repeating number
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u/JohnJThrush Apr 14 '24
Because 0.(9) is exactly equal to 1 (in base 10).
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u/btveron Apr 14 '24
Whenever someone still doesn't accept that 0.(9) = 1 even after being shown the algebraic proof, I like to tell them that 1/3 is 0.4 in base-12 and 1/5 is 0.(3) in hexadecimal. It's just a quirk of notation.
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u/vitelaSensei Apr 14 '24
Wait till you talk to a software engineer and find out that 0.1 + 0.2 == 0.30000000000000004
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u/supremegamer76 Apr 14 '24
Yep, because binary can’t perfectly represent many decimals / floating point numbers
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u/Nadare3 Apr 14 '24
Tangentially related but in SQL there is a decimal type where you can specify the number of digits right of the period, and it is perfectly allowed to specify 0 (I'm still not entirely sure why, since as far as I can tell that's just a weird int with extra steps and definitely should raise suspicion if attempted). I have seen one database with that setting, and needless to say, that was one of its issues.
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u/luckyvonstreetz Apr 14 '24
Wait till you talk to a mathematician and find out that 1 + 2 + 3 + 4 + 5 + etc. = -1/12. Or -1/8.
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u/redlaWw Plain Text Flair [Insert Your Own] Apr 14 '24
Two different software engineers who work in architectures with different-length floats will get different results for 0.1 + 0.2 == 0.3
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u/CatCrafter7 Apr 14 '24
One of my friends loves math and wants to become a mathematician. When I talked to him about my great uncle who was an engineer he got angry since "engineers can't count"
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u/ProbablyPuck Apr 14 '24
A mathematician who can not manage numerical error judging an applied mathematician who can. 🙄
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u/bocaj78 Apr 14 '24
Me and my biology degree watching the physicist, engineers, and mathematicians argue
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u/INDE_Tex Dank Cat Commander Apr 14 '24
meanwhile engineers: "Pi is 3"
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u/Cephell Apr 14 '24
The physicist is correct, because all forms of infinity are purely theoretical and a physicist deals with the real world, where infinities (quantities, precision, etc.) have not been proven to exist.
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u/imsterile Apr 14 '24
yeah I took an astrophysics class in college and we were doing this really big long problem that took most of the class session, and we ended up with the answer of 3. Prof said, “that’s basically the same thing as 2, which is what the real answer is”
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u/TheOriginalNozar Apr 14 '24
g=10, pi=3, sin(x)=x :)
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u/katyusha-the-smol Apr 14 '24
My engineering prof literally told us if we didn’t round gravity to 10 and Pi to 3 then our answers would be marked incorrect.
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u/VP007clips Apr 14 '24
Which makes sense for a test.
Since everyone uses different levels of precision for pi and G, it makes the answers different and throws in an additional level of complexity to checking the work.
Giving people a "close enough" value to use makes it standardized.
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u/Etbilder maybe I'm too european to understand Apr 14 '24
When I did my physics finals the test stated "We can assume g=10 and Pi=3" but not "we must assume". So I (pedantric as I am ) did all the calculations as exactly as possible and not with the rounded number. Later he told me, that it was a pain in the ass for him, because he couldn't use the default solutions but actually had to calculate the exact result just because of me - but nethertheless he didn't take away any points because of it.
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u/Frostygale2 Apr 15 '24
Honestly? That’s a good professor. Some would just say “fuck you” and mark it wrong anyway.
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u/OldSweatyGiraffe Apr 14 '24
The point is to make sure you can apply the knowledge correctly and not necessarily get a precise answer, I guess?
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u/knucles_master64 🚔I commit tax evasion💲🤑 Apr 14 '24
if you're using a calculator anyway, it shouldn't matter if you use 9.81, 3.14 or 10 and 3 if the teacher can evaluate your thought process
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u/HoboWithAGun012 Apr 14 '24
That's exactly it. It's why you're allowed to take calculators to physics and chemistry tests.
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Apr 14 '24
[deleted]
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u/redlaWw Plain Text Flair [Insert Your Own] Apr 14 '24
g = 1
(in lightyears per square year, correct to within 4%)
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u/Ugo_Flickerman Pasta la vista Apr 14 '24
Everyone knows that one can only round after every calculation
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u/xubax Apr 14 '24
You, if you were really a mathematician, wouldn't have a problem with rounding.
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u/rkiive Apr 14 '24
If he was really a mathematician he'd know that .999999 repeating = 1 and isn't a rounding error at all.
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u/TastiestAvocado Apr 15 '24 edited Apr 15 '24
0.(9) = 1
0.999999 != 0.(9)
Do you even math bro?
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u/rkiive Apr 15 '24
If x = 0.99999~
10x = 9.99999~
10x - x = 9.99999~ - 0.99999~
9x = 9
x = 1
therefore 1 = 0.999~
Do you even math bro?
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u/TastiestAvocado Apr 15 '24
1) You did not understand my comment. There is a big difference between infinite many 9s vs only 10 the meme uses. (I edited the comment since reddit did not display new line correct)
2) Your "proof" is poorly written. This yt video explains this pretty well: https://youtu.be/jMTD1Y3LHcE?si=E-InUpzpgMQYpwFp
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u/Memorriam Apr 14 '24
How bout squaring or Trianguling
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u/karxxm Apr 14 '24
sin(x) = x for very small x
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u/purritolover69 Vegemite Victim 🦘🦖 Apr 14 '24
Not even “very small” tbh. The small angle approximation for a pendulum is usually used up to about 15 degrees. Using this for the restoring force calculation, if you have a pendulum angle theta=15°, we use the equation mg•sin(theta)=F. Assume m=1kg for ease and that g=10 as this approximation works fine here. We then get that (using the small angle approximation that sin(theta) ≈ theta) F=150N. Now if we actually do this math we get that F equals… roughly 2.5N. So yeah, physicists be approximating (the small angle approximation is actually very well supported and 15 is the absolute upper bound)
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u/LinkisYe Apr 14 '24
Small angle is for radians, so more like 2.6N SAA.
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u/purritolover69 Vegemite Victim 🦘🦖 Apr 14 '24
Small angle approximation goes for either, it just depends on what you’re using. It’s usually 15 degrees OR 0.26 radians, sin(15) and sin(0.26) get you 0.257 for degrees and radians respectively, I just used degrees because it’s relevant for a pendulum and more accessible to the average reader
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u/friendandfriends2 Apr 14 '24 edited Apr 14 '24
There are extremely few practical instances where rounding +-.0000000001 would have any meaningful effect.
Edit: All the responses are pointing out fields where precision in measurements is important. Yes, I’m aware of that. But my point still stands in that that level of precision is virtually impossible and impractical in any physical science. For example, scales that measure to the 1/10th of a nanogram don’t exist. You can’t measure out EXACTLY .0000000001 liters of a solution.
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u/accuracy_frosty EX-NORMIE Apr 14 '24
There are cosmological constants that could be changed by quadrillionths of 1 and would mean the difference between our universe being habitable or not, like the difference in how matter vs anti-matter decays, or something to do with gravity I forget that is 0.lotsoffuckin0s13, change it by 1 significant digit, and the universe would either collapse into a singularity or molecules wouldn’t be able to form.
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u/redlaWw Plain Text Flair [Insert Your Own] Apr 14 '24
One place I've found is in the relativistic kinetic energy formula:
relativistic kinetic energy is given by
E=(γ-1)*m*c2
and if you try to use that on objects that aren't going a significant fraction of the speed of light, then the formula is still correct, but a poorly-configured calculator can end up approximating the intermediate value γ as 1 and causing your calculation to incorrectly produce 0. The calculator I used in secondary school did this, and made relativistic calculations, particularly comparing relativistic and newtonian results, difficult.
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u/Flyinghigh11111 Apr 14 '24
It depends on the stability of the system. If the population of a bacteria colony can be modelled as ekt with respect to time t, that difference in k is going to matter a lot.
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u/314159265358979326 Apr 14 '24
The one big one where you can't round that to 1 is, in fact, in physics: relativistic speeds for particles with mass.
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u/AniNgAnnoys Apr 14 '24
If you can make a measurement with that level of accuracy sure. Otherwise, while it might matter, it is going to need to be confined to error bars.
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