The h Bar

user351417

17:00

@PM2Ring This is madneß

user351417

(because that confußing one is an excellent thing to keep around :P)

John Rennie

@PM2Ring done!

dm__

i'll never understand why Jackson is the standard, when there are SO many better advanced texts. my theory: a generation suffered through it, and then they wanted the next one to as well, and then the next one, ad nauseum

PM 2Ring

@JohnRennie Much better! Thank, John.

Rico

@Chair you there having trouble

@Chair having little problem choosing the best courses after 10 borde if I want to have a physics as my carrier.

PM 2Ring

17:13

@Chair BTW, if an OP posts a dupe of their own closed question, the system does permit a dupe closure, even if the original has no answers.

Abcd

Why is everyone using $\beta$ for s @JohnRennie

PM 2Ring

@dm__ Could be. ;) The series of maths textbooks I had in high school was a bit like that.

John Rennie

@Abcd it's not a beta, it's a German character that is pronounced as "s".

Abcd

Oh okay.

John Rennie

We have been joking with ACuriousMind about it. He is German.

PM 2Ring

17:17

See en.wikipedia.org/wiki/ß; if you're curiouß

enumaris

I ßee

John Rennie

ß

In German orthography, the grapheme ß, called Eszett (IPA: [ɛsˈtsɛt]) or scharfes S (IPA: [ˈʃaɐ̯fəs ˈʔɛs], [ˈʃaːfəs ˈʔɛs], lit. "sharp S"), represents the [s] phoneme in Standard German, specifically when following long vowels and diphthongs, while ss is used after short vowels. The name Eszett combines the names of the letters of s (Es) and z (Zett) in German. The character's Unicode names in English are sharp s and eszett.It originates as the sz digraph as used in Old High German and Middle High German orthography, represented as a ligature of long s and tailed z in blackletter typography...

Loong

Next we will reintroduce ſ.

PolarBear

Hißßßßß

Loong

And then use Fraktur as standard font.

PM 2Ring

17:19

Which proves that Gollum was actually German...

enumaris

$\frak{s}$

Rico

Plz anybody help. Me I don't much about this course called IB after 10 grade . I Know. this room is not designed for carrier discussion. Plz help me . is it good to choose IB after10 grade if I want to end up my carrier with physics

enumaris

I think the two popular programs are IB and AP

I never took IB courses so I dunno them

PM 2Ring

@Loong But of courſe.

enumaris

but I just know they are some sort of "advanced" courses like AP

Rico

17:21

@enumaris Which course did you take

enumaris

I took APs

John Rennie

Presumably IB = International Baccalaureate? What is AP?

Rico

@enumaris After 10 grade ?

enumaris

AP = Advanced Placement

@Rico starting from 10th grade

I think

don't really remember lol

John Rennie

@Rico whereabouts in the world are you? The USA?

Rico

17:22

Which all subjects did you study, I mean what kinda of stuff

enumaris

standard HS stuff

I think AP courses I took were Chem, Bio, US History, Econ, and probably one other that I forgot

Rico

@JohnRennie sad to say India

enumaris

I think I had 5...

some people had 7

some had 8 or 10

John Rennie

@Rico we have lots of Indian students around so this is a good place to ask.

Rico

Thanks

@enumaris you are physists Right

enumaris

17:25

not anymore lol

but I do have a PhD in physics

now I do A.I. stuff :D

John Rennie

@Chair you're doing IB aren't you?

PolarBear

@Rico sad ಠ_ಠ

Rico

Yup

Any Cambridge student?

enumaris

maybe John? @JohnRennie where did you go to school? :P

John Rennie

@Rico I was a Cambridge student, but it was 40 years ago :-)

enumaris

17:28

aha

a Cambridge man...not an Oxford man...

John Rennie

But that doesn't help because in the UK students do A levels rather than the IB.

Rico

Damm John when see dp I feel like you are hawking

Stephen hawking

John Rennie

I did see him occasionally in Cambridge, but never said hello.

Rico

What

John Rennie

My college was near the Dept of Mathematics and Theoretical Physics where he worked.

Rico

17:31

What was his age that time

Avnish Kabaj

If I had a dollar for every time someone asked John Rennie wether he knew Stephen Hawking

PolarBear

@JohnRennie How nice.

Avnish Kabaj

(I would have $3)

PolarBear

@AvnishKabaj 10/10

John Rennie

@Rico Well it was 1980-86 I was at Cambridge. Presumably Hawking's date of birth is on Wikipedia ...

Avnish Kabaj

17:32

Eyo polar baer

Study 65 days to go

PolarBear

That's what. So much left hoohooohoooooo

I'm excited.

John Rennie

Hawking was born in 1942 to he would have been around 40 when I was at Cambridge.

Rico

@AvnishKabaj are you India n

Avnish Kabaj

@Rico no

PolarBear

He lives in Tibet.

Meditating on the Himalayas.

Rico

17:33

@JohnRennie why didn't you say a hellow

@PolarBear XD

John Rennie

@Rico he was already famous and I suspect he was pretty fed up with tourists coming up to say hello. I ddn't want to hassle him.

PolarBear

Guess if everyone who passed by said hello.

Rico

That 19 century was so beautiful , full physists

Full of physists

@JohnRennie god at least a smile

pZombie

not even a selfie?

Loong

@Rico 90 % of all the physicists that ever lived are alive today.

3

Rico

17:38

Sorry Nobel prize winners

Loong

Nobel prize? Certainly not so many in the 19th century.

Rico

@Loong thing to ask if GR was so accurate about understanding gravity why didn't he get Noble prize

John Rennie

@Rico Hawking?

Rico

Enstien

Anonymous

@Rico You mean the 20th century, no?

Anonymous

17:41

This is the 21st century.

Rico

Blue are you in ib

Anonymous

@Rico Nope.

John Rennie

Einstein did get a Nobel prize, though ironically not for relativity

PM 2Ring

What Loong said. OTOH, there was a lot of low-hanging fruit to harvest in maths & physics from the time of Galileo to the start of the 20th century.

Rico

Ya I know it was for his potoelectric effect

@JohnRennie Did that ether turned him away

Loong

17:43

@Loong Actually, there were zero Nobel prize winners in physics in the 19th century.

Anonymous

The first was in 1901.

John Rennie

@Rico the reason that Einstein didn't get a prize for relativity was because it was so hard to prove. Traditionally Nobel prizes aren't awarded for a theory unless the theory has been proven true.

Anonymous

So I suppose Rico is referring to the 20th century, and not the 19th century.

PM 2Ring

Well, relativity was still pretty controversial. But it is ironic that Einstein got his Nobel for a quantum physics thing, considering his attitude to what QM became down the track.

Anonymous

And that claim is sort of true, because physics did take a huge turn in the 1900's.

John Rennie

17:45

He was technically awarded the prize for his work on the photoelectric effect, but in reality it was awarded for relativity as well, and for his work on Brownian motion. He was an all round smart cookie.

Rico

You too

John Rennie

I taught Einstein everything he knows.

5

Anonymous

Now it all makes sense... :P

John Rennie

@Blue can you comment on whether the IB would be a good option for Rico if he wants to study physics?

Rico

Hmm yeah just came for that though

Anonymous

17:48

I did have some friends who shifted to IB in grade 11, but they had different goals compared to me. Indian students who take the IB are usually the ones who intend to shift abroad for their undergrads. If Rico intends to appear for JEE and stuff, for Indian unis IB wouldn't be a good fit. However, like Chair he certainly could apply abroad if he gets into IB.

John Rennie

@Rico check this out. Cambridge accepts the IB as a qualifying exam. That suggests it's pretty well respected.

Rico

You mean jee is good for reaserch

PM 2Ring

If you're interested in the history of relativity & QM, I urge you to read Abraham Pais' biography of Einstein Subtle is the Lord, and his biography of Bohr, Niels Bohr's times. I prefer the 1st one, but they're both good books that contain a lot of physics.

Anonymous

@Rico I dunno what you mean by that. JEE is just an entrance exam for Indians unis. :P

John Rennie

@PM2Ring Seconded. I've read it and it's very good. Though it's kind of sad to read how he wandered off down blind alleys in his later years.

Anonymous

17:50

If you want to get into research, the European countries and USA are certainly better. However, they'd be pretty damn expensive for undergrad studies. So make sure to discuss with your parents.

Rico

@Blue What did you choose after 10

John Rennie

@Blue all unis? Or just for engineering courses?

Rico

Silly one, if ether wasn't there how can he curve the space

Anonymous

@JohnRennie Ah, with JEE one can also apply to physics courses (like the IITs and some NITs have pure physics and applied math courses too). There are also the IISERs (and IISC Bangalore which Pratyush has joined) which are focused on pure science, but even those have similar competitive exams (and one can apply to those via JEE too). :)

Anonymous

Without sitting for competitive exams it's hard to get into a good uni, if not impossible. All the good unis (for science as well as engineering) have their entrance exams.

Rico

17:53

Are you iitain blue

Anonymous

@Rico I was in ISC in grades 11 and 12.

PM 2Ring

@JohnRennie It is a bit sad. But it just goes to show that even great scientists can become stuck due to their beliefs.

Rico

Isc what tell me more

Anonymous

@Rico Nope.

Anonymous

@Rico Umm, what?

Anonymous

17:57

@Rico BTW the IISERs are doing quite well in the research front. My undergrad friends there are already participating in research projects right from their first year.

PM 2Ring

I'm doing quite nicely on this answer; I almost posted it as a comment. :)

Anonymous

Unfortunately, the scope for pure math sorta sucks in India. There are very few places like ISI and CMI which have a strong focus on math at the undergrad level...and those are insanely competitive. (Balarka joined ISI Bangalore last year.)

Anonymous

BTW if you want to get into theoretical physics later, applied math is also a good choice. You could take up a physics minor (several places are offering minors these days).

enumaris

fun times...

Anonymous

That said, IB certainly would be a good choice, IF you can afford it. :P

enumaris

18:10

bad choice?

Anonymous

Oops!

enumaris

Freudian slip

he's conning you all

don't belive

Anonymous

I couldn't afford it back then (even if we could, my father wouldn't be willing to spend that much on my schooling). Those schools are very expensive. :)

Curio

I really don't know what it's wrong here:

Rico

@Blue Is it gonna be ok for my physics carrier if choose Science cbse . for least that's what I can afford

Curio

18:12

We have a solution of C2H5OH 19% m/m , so m1/(m1+m2)=19/100 so m2 =m1* 81/19

Anonymous

@Rico CBSE Science is definitely good. Also, the syllabus correlates well with JEE.

Anonymous

In fact, the JEE Mains syllabus is basically your CBSE Science syllabus.

Rico

Jee what I am going die . Basically I am thinking to do BSC and have a PhD in physics

Curio

We have to get molality, so n/m2 = (m1/M)/m2. M is 46g/mol. So at the end molality = 5.1m

Where's the mistake?

Anonymous

@Rico "die"? :P

Anonymous

18:14

You have good foresight. ;)

Rico

Not can't even afford a time for it

Foresight means

Anonymous

> the ability to predict what will happen or be needed in the future.

Rico

Jee needs a hard coching for 2 years . I just want to put my every time with physics. Even after ages of training it's hard crack it

Anonymous

@Rico That is true, yes.

Curio

Any ideas?

Rico

18:18

11:47 I guess good night blue , you are blue

Anonymous

See you! :P

Curio

Oh instead there's no mistakes lol

PolarBear

@Rico This is not true.

pZombie

18:50

They broke the 2nd law of thermodynamics... :( - nature.com/articles/…

Abcd

Woah!

Didn't a scientist claim that all laws except the 2nd Law of Thermodynamics can be violated?

Anonymous

@pZombie Erm no, you're misinterpreting it.

ACuriousMind

The introduction is very clear about this effectively being an implementation of Maxwell's demon, which is well known to lead to a local "violation" of thermodynamic laws if you do not consider the state of the demon.

The impressive thing is that Maxwell's demon, of course, is a hard thing to practically construct for a reasonably sized classical system, so it's neat they figured out how to do it for a quantum system

This is, however, by far not the first demon physicists have unleashed on the world, viz. molecular demons

pZombie

@Blue Depends i guess. If you were to agree that the 2nd law of tm was derived to be true only for idealized non-real systems then nothing was broken as it has nothing to say about the experiment conducted in the nature link i posted. But for any real system, the 2nd law of tm simply does not apply as shown by the fluctuation theorem and observed on biological agents among other things

Abcd

So.. it has not been violated?

Anonymous

19:03

@Abcd No.

ACuriousMind

@Abcd It depends on what you mean by "it" and what you mean by "violated" :P

Abcd

@Blue Lol I had already started imagining textbooks without the Second law of Thermodynamics or with modifications in it :( .

@ACuriousMind It- second law, Violated - Not applicable everywhere or The entropy of the universe is not increasing.

ACuriousMind

it is still the case that the 2nd law is not violated in closed systems, nor spontaneously in nature.

Quoth the paper:

"To make the time reversal possible, one would need a supersystem manipulating the quantum system in question. In most of the cases, such a supersystem cannot materialize spontaneously. As an illustration, we use the simplest systems of a single- or two particles subject to electromagnetic fluctuations.

We show that even the evolution of these single- or two-particle states in a free space generates the complexity that renders spontaneous time reversal either highly improbable or actually impossible. We expect that if irreversibility emerges even in the systems that simple, than, even, more it should appear in the more complex systems. "

(The "supersystem" is basically Maxwell's demon. They make no claim about the total entropy of the time-reversed system + supersystem. )

Anonymous

@pZombie Sure, but if you're already considering a real system, I don't see how this paper "breaks" it. The second law does have some assumptions. It doesn't make sense to say you've broken the law when you're working outside those assumptions.

Anonymous

You can only break a law when you're working within that framework and manage to show an inconsistency.

vzn

19:11

in theory salon, 38 secs ago, by vzn

Turning back time. Researchers use quantum computer to reverse time / scisco media

pZombie

@Blue Yes, but it is obvious to me that many, including physicists, do not really understand that this law applies only within a distinct framework, which does not describe realistic systems where quantum fluctuations are a factor. Not like there is a theory which describes any real systems 100% accurate but there are some like the fluctuation theorem which gets a little bit closer

@vzn i beat you to it

vzn

@pZombie just saw that nice find! :)

Anonymous

Eh, you don't even need to go quantum. Maxwell's demons are well known in classical statistical physics too.

Anonymous

You really need to provide citations for "many, including physicists, do not really understand that this law applies only within a distinct framework".

ACuriousMind

Of course the 2nd law works for real systems, and even for almost all quantum systems as the very paper you linked says

You can construct highly specific situations in which it does not apply, but these do not arise in nature on their own as far as we know

vzn

19:15

@Blue that was phrased in a simplistic way but quantum thermodynamics is a new/ cutting edge area of research. the paper supports the view that in short "mysteries remain"...

pZombie

@Blue if by classical statistical physics you mean a theory which includes poincare's recurrence, hence would allow a closed system to lower its entropy and even get back to min entropy in finite time, then those classical statistical physics are probably correct

ACuriousMind

@vzn quantum statistical physics is literally almost as old as quantum mechanics itself (cf. e.g. von Neumann's discussions of it). If you call quantum mechanics "new/cutting edge", then all of modern physics is cutting edge, making the moniker pointless

And the paper does not support that "mysteries remain". It refers repeatedly to other papers having predicted exactly this possibility. Where's the mystery?

pZombie

"entropy always increases in a closed system" is simply not the case for a realistic system. Imagine the system at max entropy. Now you would have to reformulate this law to "entropy either always increases or remains static in a closed system" since it cannot get higher than max (assuming there is no negative entropy)

finally, since a closed system at max entropy would never remain always at max in a realistic closed system, even the second formulation is not true for real systems

ACuriousMind

we've been over this. There is no "max entropy" for almost all systems, and I don't really care to revisit that discussion

Anonymous

@pZombie The points really is: the second law is statistical. It doesn't forbid Poncaire recurrence at all!

pZombie

19:23

@Blue that's a nice way of saying that it is blind to fluctuations

it statistically averages them away

@Blue and yes, the statement that entropy always increases would pretty much forbid poincare recurrence

Anonymous

@pZombie That's a popscience statement ("the entropy always increases"). :P

ACuriousMind

the point is that the fluctuations necessary to violate it are, under ordinary circumstances, so astronomically unlikely that there's really no difference between it and a "non-statistical law". You don't go around saying that Newton's laws are "invalid for real systems" because real systems are quantum and don't have well-defined position values

Anonymous

@Blue You'll find the rigorous version in textbooks.

ACuriousMind

Ehrenfest's theorem averages away fluctuations! It's not a real law!

Everything's just a model. Embrace it.

JMac

Embrace it deep enough and you become an engineer.

pZombie

19:28

this fairy tail with fluctuations being negligible because of the astronomical chance of a whole system reverting to its initial state is nonsense. Those fluctuations make a huge difference and are not negligible when we go towards the nanoscale, a scale that is quite big still as far as particle physicists are concerned.

vzn

@ACuriousMind sees your sentence seems to miss the point of research. :(

pZombie

There are many important implications from the Fluctuation Theorem. One is that small machines (such as nanomachines or even mitochondria in a cell) will spend part of their time actually running in "reverse". What we mean with "reverse" is that it is possible to observe that these small molecular machines are able to generate work by taking heat from the environment. - en.wikipedia.org/wiki/Fluctuation_theorem

Anonymous

@pZombie You know, talk is cheap. Let's do the math. :P

ACuriousMind

@pZombie I point you again towards the very paper you brought up, saying that even for two free electrons (arguably far below the "nanoscale"), time reversal is very unlikely.

pZombie

Now if there was no difference between what really happens and a world where we can ignore fluctuations, those mitochondria would be in a difficult position

@ACuriousMind physicists find uses for unlikely phenomena all the time

and biology does too as it appears

JMac

19:35

@pZombie It's not about "a world" where you can ignore those fluctuations, it's about what you are trying to determine and what aspects are negligible in that case. That's how negligible things work. They have some real effect; but the scale of the effect is such that it can be ignored in your analysis without changing the results.

ACuriousMind

@pZombie It sounds like you are falling prey to the old fallacious thinking that the formation of biological "order" is a violation of the 2nd law. Neither the earth as a whole nor the mitochondria of the cell are in any sense remotely a closed thermodynamical system.

vzn

The new thermodynamics: how quantum physics is bending the rules / Nature Nov 2017 nature.com/news/…

ACuriousMind

Earth is not "low entropy" because of fluctuations, but because of the massive flow of energy from the sun. Mitochondria are not "low entropy" because of fluctuations, but because of the influx of chemical energy from citric acid cycle, which ultimately also sustains itself through the sun (photosynthesis)

Life is just a heat engine, fuelled by the sun. And when the sun is one day gone, then entropy will get us all.

pZombie

then let me ask you this way...

What would be the minimal amount of measurements required to prove to you that the 2nd law of thermodynamics does not apply to our universe

What kind of minimal experiment, measuring what exactly would you propose to test if the 2nd law of tm is true or not

surely, there has to be some minimal amount of measurements to settle this once and for all

ACuriousMind

@pZombie Only a single one, but of the following nature: 1. It does not use a system that can attain negative absolute temperatures. (I'm not sure this has any actual relevance) 2. It demonstrates reproducibly a closed system whose total entropy decreases without interference from outside.

vzn

19:47

UK Put a Black Hole on a 50p Coin to Honour Stephen Hawking, And It Looks Stunning / sciencealert

Physicists reverse time using quantum computer / physorg

ACuriousMind

@vzn Do you really need to link more pop-sci articles badly paraphrasing the paper when the paper is already posted and starred here?

pZombie

easy, put some gas in a box with a given total energy. Let it reach max entropy. Keep measuring the entropy periodically and eventually you would find it to have decreased. Now you might argue that this is not really a closed system but one would have to consider the whole universe instead. But you can consider a whole mini universe with just that gas.

Anonymous

"Physicists reverse time using quantum computer"...I love this one. :P

Anonymous

> But you can consider a whole mini universe with just that gas.

pZombie

or consider our universe when it reaches a state of max entropy

unfortunately our is in an accelerating expansion phase which makes matters a bit more complicated i guess

ACuriousMind

19:54

@pZombie 1. Again, there is no "max entropy". 2. The gas does not "reach" any entropy. Entropy is a function of a thermodynamical macrostate and usually only applied to equilibrium states. A closed system in equilibrium does not evolve at all, it just sits there. Fluctuations are changes in the microstate invisible to the macrostate. 3. How do you measure the entropy of a gas in the box?

pZombie

obviously i mean max entropy state

@ACuriousMind 3. How do you measure the entropy of a gas in the box? - Are you implying that we cannot estimate the entropy state of a gas in a box by measurements like using nano sized pressure/temperature/particle detectors placed all over the box?

If i cannot detect a particle on the right side of the box for quite some time, i would have to assume that it is not in a max entropy state yet unless i got very unlucky

JMac

@pZombie How would you get that information out of the box while keeping it isolated?

pZombie

by making the particle detectors, myself and the computer analyzing the data part of the box

ACuriousMind

@pZombie Okay, so we compute the entropy from these measurements through the ordinary equilbrium relations. Even without quibbling about whether this is a closed system, I am fully confident that you can stare at the measurements from that box until I am dead without ever being able to show me that the entropy has decreased.

pZombie

@ACuriousMind Are you sure that if the box contained only 20 particles or even 100, you would have to wait that long?

ACuriousMind

20:05

@pZombie How are you getting a "pressure" from 20 particles? With 20 particles you can detect the individual particles hitting the walls, not measure a "pressure"!

I.e. I do not see how that's a usual thermodynamical system for which the notions of "pressure", "temperature" or "entropy" make sense

pZombie

why, is there an exact amount of particles per volume requirement for the 2nd law of tm to be true? Which amount would that be then?

ACuriousMind

The sorts of statistical systems you make with 20 particles are usually "string of spinful atoms in a magnetic field", not "gas in a box".

@pZombie If you can give a proper definition of temperature and pressure and a procedure to measure them reliably for such a low number of particles I'm happy to hear it.

pZombie

to do that, we would first have to agree on what a temperature measurement consistutes

and more precise, how our measurement device measures temperature

and then show me that this cannot be applied to a box with 100 particles inside

is there a time limit which we are not allowed to exceed when placing a thermometer in a box?

a temperature measurements time limited?

ACuriousMind

@pZombie You are reversing the burden of proof here - you claim that you have an experiment that would show the second law to be untrue in the sense I outlined above. You have not produced a citation for this claim, nor have you been able to describe the experiment to my satisfaction. But, frankly, even if you did describe it to my satisfaction I'd still ask you to provide the actual evidence, not least for your own good.

Don't you realize that a reliable violation of the 2nd law without demons (classical or quantum) acting as a potential producer of the "missing" entropy would be a major publication?

pZombie

actually i did not claim that i have an experiment. The opposite is the case. I asked YOU to device a minimal experiment which in case it would turn out positive, it would show the 2nd law of tm to be violated.

Since anything we bring up does not seem to convince you, then surely you must have thought of something that would settle this

JMac

20:16

But then you proposed your own experiment, which is what he was talking about

pZombie

@JMac not really, i just reduced the number of particles

ACuriousMind

uh...if I knew an actual experimental setup that I believed could disprove the second law, why would I believe the law held true?

pZombie

that's a strange thing to say

ACuriousMind

I described a category of experiments which, if they yielded a certain result, would convince me

Qmechanic

@AvnishKabaj : This is just in: An election of 2 new moderators is scheduled to start some time in April to replace Manishearth and because of increase in traffic.

10

ACuriousMind

20:18

Then you claimed your gas in a box is such an experiment and indeed would yield the result. I disagree. But in order to end this discussion: No matter how you engineer your gas in a box, and no matter the number of particles, I do believe I will be dead and you will still be staring at the box.

Anonymous

@Qmechanic Oh, an election. Fun times! :)

pZombie

maybe you are older than me then

ACuriousMind

Statistically unlikely, but much more likely than a violation of the second law :P

Anonymous

I'm pinning it if you don't mind. And let's see if we can coax @JohnRennie to run this time. :P

JMac

@Qmechanic I assume this is to keep up with all the rules Emilio will want to implement about HNQs? :P

Anonymous

20:25

Nah, this time SE'll probably hit us with sticks and stones if we pester them about the HNQ again. ;P

JMac

We don't have to pester them anymore though, that was my point, now we can pester our own moderators

Anonymous

Ah, that'd be fun...

Anonymous

Kicking off all the pop-sci from HNQ? :D

Anonymous

(Emilio might actually take that idea seriously...)

Anonymous

But yeah, we have a lot of good folks here who could lend a helping hand in moderation.

JMac

20:31

there's a really good pool of active users that would fit well, I'm interested to see who actually wants the position

PM 2Ring

Say we have a box containing 320 (which is less than 7 cubed) particles moving randomly.Each particle can be found on either the left or the right side of the box. On average, there will be equal numbers of particles on each side, give or take 18 or so, but if we wait long enough, they'll all be on the right side. Let's simulate the particles via coin tossing.

Feb 3 at 18:05, by PM 2Ring

Let's expand the coin tossing experiment to 320 coins. 2^10 is a little over 10^3, so 2^320 is around 10^96. The universe is just under 14 billion years old, and there's about 31 million seconds in a year. There's around 10^80 protons in the observable universe, so let's pretend we can flip each proton like a coin, 320 times per second. We'd expect a single run of 320 heads by now.

Luyw

20:47

Guys, hi

Quick question about diodes, does it conduct when the potential difference across it is positive or if it is superior to its "characteristic voltage"?

PM 2Ring

21:20

@Luyw When the diode is forward biased, you get a small current for voltage below the threshold, but generally you need to be at the threshold voltage (or higher) for the diode to be considered switched on. The Wikipedia article is pretty good.

Luyw

Thank you!

PM 2Ring

21:35

There's already a question about that quantum time reversal stuff physics.stackexchange.com/questions/466335/…

Anonymous

> This method will not be used to raise the dead, unspill cups of coffee, take back stupid actions, or any of the other practical applications of reversing the arrow of time

Anonymous

Yeah, we needed someone to write that down. :P

PM 2Ring

With this kind of stuff, you gotta nip it in the bud. ;)

Anonymous

Totally!

Anonymous

Anonymous

21:48

Okay, LOL. Found it.

Physics Meta

22:13

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Q: Should I Not Edit My Old Questions On a Spree?

I recently visited a couple of old questions that I had posted and there were a lot of edits (mainly grammatical but not all) that I wanted to make. I edited a couple of them and went back to the homepage and the homepage had all of these edited questions on it. It seemed like a disruption in the...

Scientist Smith YT

23:03

@All According to an article I read physicists say that sound waves might carry mass. What are everyone’s thoughts on this?

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