@offsetSammy (I'm a physicist.):

Basically what @GlasWolf said. There are in principle an infinite number of things that can happen between the input and the output (you may for instance always add an extra self-energy term as shown in the video at 5:30 onwards), but usually only a few of all these infinite possible processes make up most of the total process.

To understand what I mean by that, it's important to remember that we are talking about quantum physics here. When we say that the different subprocesses have different probabilities, we don't mean that the particles choose (with a certain probaility) one of the possible Feynman diagrams to follow. No, in fact all the possible diagrams are followed at the same time. But the fact that some of the diagrams are more likely than others means that they are weigthed more heavily in the calculations. All the diagrams that contribute a tiny part to the total process can therefore be ignored, making the calculation much easier. And if your calculations turn out incorrect, you can simply add a few extra diagrams and try again.

This is also related to why the Feynman diagrams at first were met with scepticism by the physics community. Particles behave according to quantum mechanics, and don't go along straight lines as in the diagrams. But it turns out that they are very useful for translating the inherently counter-intuitive quantum physics into a language that is easier for the human brain to understand. They were therefore accepted as a very valuable tool, even though they are technically unphysical.

>> ^offsetSammy:

Here's something I have never understood about Feynman diagrams, and I hope someone can explain it to me.
A Feynman diagram represents one possible way that two particles can interact, and from a single diagram you can work out the probability of that event occuring. But wouldn't there be an infinite number of ways an interaction could play out, and therefore an infinite number of diagrams? How do you know which one to draw?


It depends exactly what you mean. For an electron-positron annihilation/scatter, there are a couple of basic diagrams as he showed in the film. These are called "second order diagrams", indicating that there are two vertices. You can add in extra loops and vertices in the middle of the diagram to create third, fourth etc. orders, but each one contributes a very quickly decreasing amount towards the whole picture. I'm no physicist, but I think after the fourth or fifth order they're pretty much just ignored.

If you mean there are an infinite number of "things that can happen" for each input, then no; it's very limited by the rules of the diagram (mostly based around conservation rules - charge, momentum etc.). Drawing out the diagram, twisting it around and swapping the joins and vertices is a very good way of determining what the possible outcomes are.

Here's something I have never understood about Feynman diagrams, and I hope someone can explain it to me.

A Feynman diagram represents one possible way that two particles can interact, and from a single diagram you can work out the probability of that event occuring. But wouldn't there be an infinite number of ways an interaction could play out, and therefore an infinite number of diagrams? How do you know which one to draw?

Your video, Quantum Field Theory Made Easy! - Feynman Diagrams, has made it into the Top 15 New Videos listing. Congratulations on your achievement. For your contribution you have been awarded 1 Power Point.

Being a nerd but not a scientist, i've read about how awesome Feynman Diagrams are but this is the first time i've understood them!

I've cheated plenty of times in school and it did me no harm - what's the point in rote learning some history dates you'll never use again for the rest of your life, or some diagram of a cell. In my job i use google throughout the day to get things done quicker, to reuse where possible. Rote learning is outdated and achieves nothing, except to encourage cheating.

Not technically a dupe but there is a couple of versions of this already on the sift.

http://videosift.com/video/I-m-my-own-grandpa-with-family-tree-diagram-Ray-Stevens

i agree with everything you just said, but i think you might be over estimating how much of it is science.
it's a great deal business. at least in the US. where medicine is mostly for profit. for huge huge profits.
medical RESEARCH is in fact, science. and i have faith in it. the dispensing of medicine is however, a business.

i'm saying this as someone who has degrees in health science fields. spent 8 years as a health care professional. spent 1/3 of that time doing administrative work. and now owns a business as a CAM practitioner.... which btw, is also a good bit business.

i'd also like to stick up for alternative medicine here.
a good deal of it is bullshit. any results are simply the placebo effect. but i don't think we should discount the placebo effect. it's an amazing mechanism. if you feel less depressed because someone hit you with a tuning fork and you didn't have to take any pills or go to a counselor, then okay. that's awesome. i still think you probably need counseling, but whatever. i also think you should take a good hard look at your diet and how much exercise you're doing. but how much does it cost in the US to go to a counselor, go to a doctor, get your anti-depressants and have a nutritionist and a phsyical trainer help you learn how to excercise and eat right? it's probably cheaper to pay someone $80 to hit you with that tuning fork and convince yourself it's going to work.

I make a decent living practicing complementary health care. but i don't tell anyone they need to be hit with a tuning fork or have someone throw energy beams out of their hands at them. i tell people they need to stretch, and i teach them how. i tell people they need to sleep properly, and i help them do it. i tell people they need to find an effective way to deal with stress, and i give them that. i tell people they need to find a form of exercise that's right for their bodies and lifestyles, and i help them find it. a lot of people just need someone to trust and someone to talk to. and that's why they call me a "therapist". i never tell people to go against their doctor's orders. i never tell anyone to stop taking their medicine or not to be vaccinated. and that's why what i do is COMPLEMENTARY.

we're too quick to dismiss a different approach when it comes to health care.
the same people are also very quick to be able to recognize the problems with our for profit health care systems when it comes to political discussions. the profit motive hasn't just tainted medicine in terms of disparity. it's tainted it in terms of effectiveness. this is where a holistic approach is good. it's not effect to only treat the symptom. if someone is overweight, has high blood pressure, their stress is out of control and they have diabetes. prescribing them pills, while necessary in the short term, is not at all where the "care" should end. i know doctors will also tell their patients to eat right and exercise but they do not teach them how to do it. because for profit health care doesn't think that is profitable. a for profit system does not want you healthy.

soooo... the market has opened up. if the way we practice medicine and viewed health in this country was working, people wouldn't pay to get hit with tuning forks. oh and half of this is a problem with our education system.
>> ^dag:

^Yes, how dare anyone question the all-knowing oracles of medical knowledge.
I think the reason that many geeky type people always toe the main-stream medical line is because they conflate medicine with science (which we all love). Yes, it's almost the same, but if I had to draw it as a venn diagram, there would be a crescent of over-hang. Medicine to me is 80% science and then the rest is filled in with dogma, patriarchy and business ($$).
That crescent of non-science is the part that makes me squirm. I don't think it's that wrong to question medical programs like vaccinations- with the idea that it may be being pushed non-scientifically by the medical industrial complex. (big pharma).
Bill Maher is not a kook.

Well... Their diagram is a little funny. I think you could do it if the car or track was a superconductor, but I don't see the reason to make both superconducting.

Superconductors levitate by generating an equal and opposite magnetic field outside the superconductor to expel the magnetic flux inside (think Lenz's Law). The Meissner Effect is naively perfect diamagnetism.

I look at this and think it is totally doable. If you want I can send the video to guy I know that studies superconductors. I think most physicists would probably say that you could make this.

>> ^dannym3141:

Pretty sure that's possible, i don't care to speculate how in an engineering fashion, but sure, you can get them to follow a track and even suspend them upside down if you like, i don't how well they can stick to the track during fast turns, perhaps you'd need to tilt the surface gradually.
I assume it'd be easier to cool the track rather than the cars, otherwise you're gonna have to wire up the cars to deliver coolant which would destroy the point. The idea of nitrogen gas coming out of the tiny cars for the whole video is a bit of a suggestion it's not real. That's assuming he was putting nitrogen in the car in that weird pipe.
Shit, they do stuff similar to this with trains full of people in some places. Probably a bit of a tamer ride because of the much higher masses involved.
(I study physics, but maybe someone knows more than me about the current progress on all that)

In reply to this comment by budzos:
Aw, gee. Now we've bonded. This is how I make all my friends. VS definitely one of the friendlier places on the net. That's why I gave you a rationale/weak apology for calling you a cunt!



In reply to this comment by budzos:
And I think the best answer to your question about what explanation I would prefer is: a vague 2D force diagram sort of explanation with words and gestures if a graphic overlay is out of the question.

That's also how I would have described it if I was him, in addition to talking about compression waves. But I guess they wanted to keep it short.

Aw, gee. Now we've bonded. This is how I make all my friends. VS definitely one of the friendlier places on the net. That's why I gave you a rationale/weak apology for calling you a cunt!

And I think the best answer to your question about what explanation I would prefer is: a vague 2D force diagram sort of explanation with words and gestures if a graphic overlay is out of the question.

In reply to this comment by Ornthoron:
Ok, tempers can rise. I just don't like being called a cunt, especially when I can't see any reason for the increased anger. And I'm also used to VideoSift being a more friendly corner of the internet than many others. From your second comment on my profile I see that you have deeper reasons than I thought, but I believe you misunderstand my intentions, as I have partially explained below.

In reply to this comment by budzos:
By the way, don't take me seriously. I abuse my anonymity online and would not be this rude or reactive otherwise. And really I'm just procrastinating and trying to ward off anxiety. Plus I type really fast and sometimes fire off things that I probably wouldn't if I waited five more minutes. So no hard feelings.

In reply to this comment by Ornthoron:
May I ask what has made you so pissed off with me?

In reply to this comment by budzos:
Explain why you're being a cunt.

The diagram didn't show how the air gets into a pressurized chamber. Since it's a clincher type tire, and clincher rims don't hold air pressure at all, I'm guessing this tire uses a regular bike tube, and there's an external device from the tire to the tube valve similar to the valve on a bike pump. I'm seeing something like that in the photos of the wheel before the ride. This device would also have to contain a gauge so it would know when to stop putting the air into the chamber.

The only advantage this product provides is eliminating regular maintenance pumping (10 strokes once every few weeks). It does not eliminate the pumping needed when you get a proper flat, because you can't roll with no air in it at all. This product would be aimed only at recreational cyclists who want to occasionally avoid using a pump. Seriously?

Also given that the pump's life is over once that outer tube got cut, that's the whole point of the tire gone. I guess it'd still continue to function as a normal tire, but where's the fun in that?>> ^albrite30:

>> ^GenjiKilpatrick:
..what happened when you get a couple nails/shards of glass in 'em?

I was wondering that too. I would suspect that they would have to buy a new outer tube to surround the aluminum. Great idea, but perhaps not cost effective yet.
[edit]

I understand why this is confusing as hell;

http://science.kennesaw.edu/~jdirnber/InvertZoo/LecIntro/TreeTime.jpg

... here is a relatively straight-forward 'evolutionary tree' cartoon,... the biggest thing to note is the Time axis... you have to trace the lines to see where species diverge and then look around to see if that line split happens before other line splits with respect to the Time direction.

Even in this simple diagram, you have to look at it for a minute to realize that reptiles, birds and most of the dinosaurs we think of split off from what became mammals, then reptiles split off from that group, then some dinos split off, then birds... So this is to illustrate that the split between what became mammals is farther back in time than the split separating birds and most dinos, and birds and reptiles. So this illustration really functions like a family tree, showing relationships with time and allow you to pick out that birds are closely related to dinosaurs, and that we have to go pretty far back to see where animals diverged into what became mammals and what became reptile/bird/dinosaurs.

If you're interested you should look for bigger ones trees,... when you start including plants, bacteria, archaebacteria, etc.... stuff gets pretty wild because you're reaching the edge of the science... and the complex smaller trees that just cover one group of critters can be really interesting to see... so much variety.

Oh, last note for transparency; they generally make these 'family trees' by researching comparative anatomy and tons of fossils, but have been using DNA to produce new and correct old 'phylogenetic trees' for 20 or 30 years now.

(image from this page, which focuses on terminology, but has good pictures: http://science.kennesaw.edu/~jdirnber/Bio2108/Lecture/LecPhylogeny/LecPhylogeny.html )


>> ^Jinx:

>> ^heathen:
>> ^Jinx:
Same logic: What are we then?

Mammals - which birds aren't and dinosaurs weren't.

Yes ok, but Mammals are as much Reptile as Bird are Dinosaur.

It's the mindset of "It's just business." If someone does it because they want to do it and act like he does on TV they are deranged. However if that person gets paid for it, business-men like themselves can see their motives (Money).

I mean can't you understand that they are getting 7 digit salaries to act like a complete asshole? Wouldn't you do that if were offered that kind of money? Why can't people understand it's business, it doesn't reflect his TRUE beliefs, morality, etc etc etc.

And they just keep telling themselves that until someone gets tired of them harping at them one too many times and pretending like they didn't just insult them for cash. Somehow they are supposed to keep their "Im a human too" card, but get to behave however they want.

If he didn't have people to take care of shit for him in a semi-anonymous fashion with lawyers to back them up if something gets squirrely...I think Beck would have a hard time operating on a daily basis when he's likely offended/insulted every other person out there. Would you like spit in that coffee?

As for the wife, she married, stayed married and had a kid with this guy.....no one in their right mind can say that she doesn't know what her husband does on a daily basis like he's some kind of secretive mobster.

Daughter......perhaps she is so far removed from reality through his money that she thinks it's normal, but I still find that hard to believe. It'd be pretty hard not to see your father on TV crying, ranting, drawing weird circular chalk diagrams plus doing gold investment commercials and not get a pretty good idea of what he does. So, either she has the "it's just business" mindset down, or she's a nut too.

And the boyfriend? Dunno if his daughter is hot, but hey girl with a rich family......he probably has the "I do it for the money, not because I agree with it." mindset down.

But, I think he just uses a played up version of events to make him look "right". I mean he doesn't mention his security at all. And if he has security, he knows there's the potential for people to decide his face needs a few more lumps.

I've got that book. Mine doesn't have diagrams either.