**Ask a monkey a physics question thread**

[MadMojoMonkey]

Even after you wash something, most anti-bacterial soaps /sanitizers claim to kill 99.99% of germs. So that leaves about 1 part per ten thousand... which is a over a thousand times more than necessary for the average person's nose to smell.

Just realized that could mean that 99.99% of known bacteria will be killed... and not necessarily 99.99% of any sample.

[a500lbgorilla]

The Prince Rupert drop video is effing awesome

[wufwugy]

the majority of the genetic differences between humans and chimps are olfactory

[chemist]

The human sense of smell is sensitive to several parts per billion. Which means that only a few molecules of 'stink' per every billion molecules of air can be smelled by an average human's sense of smell. Microscopic particles can remain suspended in the air for a surprisingly long time. Dust from the Sahara makes its way to South America.

Even after you wash something, most anti-bacterial soaps /sanitizers claim to kill 99.99% of germs. So that leaves about 1 part per ten thousand... which is a over a thousand times more than necessary for the average person's nose to smell.


P.S. smell disappear

Which is enough to catch the noro virus from vomit or faecal particles.
So can you catch it from some douche farting?
If you smelt it you caught it.

[Savy]

Just realized that could mean that 99.99% of known bacteria will be killed... and not necessarily 99.99% of any sample.

You realise it says 99.99% because it'd cost them millions to do testing to get every single form of bacteria to prove it was 100% not because it leaves 0.001% alive.

[jackvance]

Links, please.

http://www.forbes.com/sites/markgibb...nge-after-all/

[MadMojoMonkey]

Which is enough to catch the noro virus from vomit or faecal particles.
So can you catch it from some douche farting?
If you smelt it you caught it.

From the wiki on Norovirus:
"infection can follow eating food or breathing air near an episode of vomiting, even if cleaned up"

[MadMojoMonkey]

http://www.forbes.com/sites/markgibb...nge-after-all/

OK, this is news to me. It does seem as though some preliminary verifications are coming in. No one has a physical model for the process yet, so that's interesting.

The inventor, Andrea Rossi, has had a dubious history with false claims and tax fraud / waste dumping fiascoes that ended his previous businesses. So it wouldn't at all be surprising if this is another scheme or scam. Also, his paper was reviewed and the scientific community basically responded by saying that his designs were inconsistent with any accepted theoretical model.

That said, there is a research group in Bologna, Italy that claims to have reproduced Rossi's results. If that's true, it basically ends the scientific criticism for a while... until more experiments can be performed to reproduce the results.

In short, this is either a spectacular, ground breaking invention/discovery, or it's just a flash in the pan. If it truly works, then physics is going to have to catch up a bit and figure out what's going on.

I have to say that the author is a bit hyperbolic and speculative in his linked articles. The E-CAT web site is completely useless as to describing it.

[wufwugy]

Pretty sure it's bunk. If not, it would be huge news, which it has been many times in the past, only to be found bunk. The inventor being shady voids all credibility, and there are loads of false claims in research

[abelardx]

Aren't tokamaks a real thing though?

[MadMojoMonkey]

Aren't tokamaks a real thing though?

Oh yes. There are dozens of them... well more than 2 dozen, at least. There's one in the UK at Culham Science Centre in Oxfordshire, for the UK crowd in the audience.

They are not cold fusion, though.

[eberetta1]

It took years of building a big enough particle accelerator to make a high enough energy collision to have any hope of detecting a Higgs boson. The LHC at CERN has accomplished this task. After more years of experimenting, scientists have found a particle with some of the properties that Higgs suggested the Higgs particle should have.

Could this thing accidentally create a black hole on Earth...

[MadMojoMonkey]

Could [the LHC at CERN] accidentally create a black hole on Earth...

Well... I wouldn't say, "accidentally"... more like "hopefully". It would give us the chance to observe Hawking Radiation and award a Nobel before he dies.

The thing about the LHC at CERN is that it's a controlled environment. It's not even close to the highest energy experiments that are conducted on earth. It's just that the other ones are caused by cosmic rays. For those experiments, it's hard to get the detectors in the right place at the right time since we don't know when or where to look. Cosmic rays come predominantly in low energies, but extremely high energy particles have been observed, as much as 50 times more energy than possible at the LHC. These extremely high energy particles hit the Earth ~1 per year per km^2... so you see what I mean about not knowing where or when to look.

Bear in mind that the LHC runs 400 million experiments per second when it's switched on, of which ~100,000 per second will yield "interesting" results... I.e. a particle collision that could have produced a Higgs boson.

[MadMojoMonkey]

I found this one. Short and sweet.
Place a candle in the center of a capacitor and watch the flame split in 2.
What's In A Candle Flame?
My favorite part was watching the smoke after the candle went out. The 3 streams of smoke... 1 to each plate of the capacitor and 1 straight up... very cool.

[Pelion]

http://www.youtube.com/watch?v=ph8xusY3GTM this is pretty cool too. Cooling water below freezing point and keeping it a liquid, and then causing it to freeze in seconds.

[a500lbgorilla]

On NPR today http://www.npr.org/blogs/krulwich/20...tein-s-glasses

[MadMojoMonkey]

Just a quick note for those of you who're interested in the Higgs Boson.

I misunderstood some bits and can clarify one thing.

The Higgs boson is not responsible for imparting mass to things which are massive. (protons, electrons, etc.)

The Higgs boson is evidence of the Higgs field, which imparts mass to massive objects through the Higgs mechanism.

The observation of the Higgs boson is as close as we can get to actually observing the Higgs field. In fact, we can only observe the photons left over after a Higgs boson decays. So everything about the Higgs mechanism is completely unobservable in any direct sense. We have observed the photons from the decay of many Higgs bosons, though... which is evidence of the underlying mechanism.

This is one of those cases where the fact that theory preceded observation is the compelling case for the theory being the appropriate description.

[a500lbgorilla]

Some physics news. Apparently their gonna hit a ball with some light and wrap physics up.

https://www.simonsfoundation.org/qua...ity-interface/

[MadMojoMonkey]

Why is the sky blue?

Why does water boil?

What doesn't superfluid boil?

How can a superconductor have 0 resistance? Is it really 0 or just very small?

How does my oven work?

How does my microwave work?

Why don't solar electric panels trump gasoline and coal?

Why does the earth have a magnetic field?
(Trick question. No one knows. We think there are currents of molten iron inside the earth that carry charges in knotted loops... Why there is any rotation that is out of sync with the surface rotation is a mystery. Viscous drag should have dampened irregularities in the flow so that the entire globe would be spinning at a constant rotation rate by any known model.)

Is it true that everything is radioactive? (yes)
If it's true that everything's radioactive... then what's the big deal with radiation?

Does the fact that the position wave function of every particle that is "me" or "you" or anything occupies the entire universe with a non-zero value mean that we're all connected in a mystical kind of way?

***
Just throwing you guys a few softballs.. seems like you've lost the spark of curiosity.

[seven-deuce]

Is it true that everything is radioactive? (yes)
If it's true that everything's radioactive... then what's the big deal with radiation?

Can you answer this one?

Edit - And how does this work - http://www.youtube.com/watch?v=kbJIjWhsn7I

[MadMojoMonkey]

Is it true that everything is radioactive?
Pretty much. All matter in the universe has non-zero temperature. Anything with non-zero temperature radiates photons as it cools. This is called blackbody radiation, and was one of the first major discoveries of Quantum Mechanics. Nothing can cool to absolute zero temperature by any finite number of steps, as we know from thermodynamics. So everything radiates, it's just a matter of how much.

Humans radiate heat, a form of light, which is electromagnetic radiation. Many people have heard of heat lamps... which are otherwise normal lamps, but which glow strongly in the infrared bandwidth. Infrared radiation corresponds to a temperature of ~300 Kelvin, which is very nearly human body temperature. Humans strongly interact with the infrared bandwidth of electromagnetic radiation, because that's the frequency of radiation that corresponds to our temperature.


If it's true that everything's radioactive... then what's the big deal with radiation?
There are basically 3 kinds of radiation: Alpha particles, beta particles and gamma rays. These names basically mean the first, second and third kind, using the first 3 letters of the Greek alphabet. These names were chosen when very little was known about the radiation, other than that it seemed to come in 3 kinds.

Since then, we've learned that an Alpha particle is a fully ionized Helium nucleus... that is, it's 2 protons and 2 neutrons bonded together without any electrons. Alpha particles have a charge of +2, and are "heavy" and "large" from a radiation perspective. You can protect yourself from alpha radiation by holding up a piece of paper. Alpha particles are easily stopped due to their size, mass, relatively slow movement, and charge. In general, alpha particles are not dangerous to humans, as your clothes will protect you from them.

Alpha particles are released when an atomic nucleus undergoes nuclear fission. The release of 2 protons from the nucleus changes the chemical properties of the atom... moving it 2 spaces to the left on the periodic table.

Beta particles have since been found to be electrons. These can be dangerous to humans, depending on the amount and speed of the electrons as they come in contact with your body. If the electron has enough (kinetic) energy, it can speed through your body, slowing down as it passes through and ionizing nearby atoms and molecules as it decelerates. This ionization may or may not cause a problem, depending on how widespread it is. Generally, being exposed to beta radiation is considered a bad thing. Since beta particles are actually electrons, they can be absorbed by metal, like aluminum foil... well thick aluminum foil, or perhaps aluminum sheet.

Gamma rays are the major problem. Gamma rays are photons. The bandwidth called gamma rays is the highest energy portion of the electromagnetic spectrum. Gamma rays are higher in energy than X-rays. Gamma rays are created by protons inside a large nucleus changing their energy level and releasing the difference in the form of a photon.
This roughly analogous to a ball falling from one stair to a lower stair and letting out a thunk. The thunk is the gamma ray... but it maintains all of it's energy in one lump; it does not get quieter if you're farther away... it's silent or it's a boom... only one person hears it, and they hear all of it... a photon is a quantum thing, it can not dissipate it's energy by spreading out.

When that gamma ray is absorbed by another proton inside another nucleus, there's a chance that the other nucleus is much smaller than the parent nucleus from which the gamma ray originated. When the absorbing proton receives that boost of energy, it can be enough to eject the proton from the nucleus entirely... nuclear fission. Again, this fission will change the atom's chemical nature by moving it one space to the left on the periodic table.
This is the danger of gamma radiation, which is fundamentally just really, really violet light. (It's silly to use a color word, like violet, since the eye can't see them, but they're very high energy and violet is higher energy than red.)

If one of the atoms in the DNA inside a cell nucleus is changed, then it is no longer the same DNA molecule it was a moment before. This can be no problem, or a big problem, depending on your the cell reacts to the change. This is generally is considered to be a major cause of cancer.


So the big deal is that there's no real difference to a physicist between radio waves, microwaves, visible light, X-rays and gamma rays. They're just arbitrary names that divide up the electromagnetic spectrum. E.g. you or I might disagree if something is red-orange or orange-red... because those are arbitrary names.

So the problem is that the word "radiation" covers too much ground. Some radiation can be used to send radio signals or cook food in a microwave oven... Some radiation allows us to see the world around us... Some radiation can cause cancer or even instant death if the exposure is too high.


Geez, this is long... I can go on, as usual. Any questions?

[MadMojoMonkey]

And how does this work - http://www.youtube.com/watch?v=kbJIjWhsn7I

2 cameras on tripods. All you need is 1 camera, but it takes a lot longer to shoot it all. The tripod is mandatory.

For setup, each camera outputs to a single screen which blends the images 50/50 so that the cameras can be aligned to view identical images, but on different floors of the stairwell.

Then it's just finding willing participants for the prank, and a clever editor.

There's some other hand-cam work being done there, but the basic premise is the same.

It's MIT, man... too many nerds with access to cool technological shizzle wizzle... and a historical reputation for epic pranks.

[wufwugy]

currently reading this. http://www.reddit.com/r/science/comm..._wormhole_mit/

can you eli5 the difference between the standard model and string theory?

[MadMojoMonkey]

That looks like a pretty good discussion, but I didn't read too much of it. You should read up on the "EPR paradox" to get an overview of what Quantum Entanglement is. I wrote a paper about it, so I can go on at length about EPR if you're curious.

The Standard Model is basically, "What we've figured out so far". It is the most widely tested collection of predictive ideas in the history of humanity. Its counter-intuitive elements of Quantum Mechanics have been so refuted and tested to the point that we now know that the predictions are accurate to something like 35 decimal places. No other predictive theory in history shows that kind of accuracy and precision.

It's hard for me not to say, "The Standard Model is what we know is right." However, that's no way to talk about scientific theories. We know that there is always a non-zero chance that they're incorrect, or incomplete. This openness to the revision of the Standard Model is its inherent strength. If anything is shown to disprove a part of the Standard Model, that disproved part is thrown out.


String Theories are nipping at the boundaries of the Standard Model. There is plenty that the Standard Model doesn't explain, or explains poorly. String theories are trying to find explanations that can make sense of the things in the Standard Model that are still incomplete.

String theories are taking the idea that particles behave like waves to posit that they look like waves because some physical thing is waving.
That makes sense to me.
They suppose the thing that is waving is a string of some sort with a thickness many times smaller than the diameter of a proton.
That also makes sense to me.
Unfortunately, there is no way to measure anything that tiny. Even if it's length spans the universe, the thinness of it makes it invisible to any known detection method.
So one problem with string theories is that their fundamental premise is unobservable.

Another problem is that in order to be included in the Standard Model, a string theory would have to make a prediction that is not made by a preexisting portion of the Standard Model. It has to provide "new" or "unique" insight into the nature of the universe to be added to the current explanation.

No string theory has yet predicted anything that is not predicted already and which is also observable.

There's no reason to assume that these theories will or wont come to greater fruition, but decades upon decades of work on string theories has not yet yielded new physics.

[wufwugy]

Another problem is that in order to be included in the Standard Model, a string theory would have to make a prediction that is not made by a preexisting portion of the Standard Model. It has to provide "new" or "unique" insight into the nature of the universe to be added to the current explanation.

No string theory has yet predicted anything that is not predicted already and which is also observable.

This is mainly the area I'm looking for clarification on. If string theory doesn't predict anything that isn't also predicted by the standard model, then how is it distinguishable from the standard model? If not, doesn't this make string theory the god of the gaps, where it kinda just makes stuff up about what can't be known?

[MadMojoMonkey]

If string theory doesn't predict anything that isn't also predicted by the standard model, then how is it distinguishable from the standard model?

First of all, there are many string theories, not just 1. Different theoreticians are taking different assumptions about the properties of the strings.

They're different from the Standard Model because they do not fully overlap. When a string theorist is doing his research, he first assumes physical properties of the strings. Next, he tries to show how strings with these properties would look like anything already described in the Standard Model. Then, he tries to see what else the string theory says.

So the idea that string theories are equivalent to the Standard Model is a misunderstanding. They only agree with the Standard Model in so far as the fundamental assumptions have been tweaked to force agreement somewhere.

Once the theorist can demonstrate that he's describing something physical, then he looks to see what else it describes. If it makes predictions that are at odds with the Standard Model in any way, that particular string theory is discarded.


So it's like the string theory starts out by tracing the Standard Model, then tries to color it in while staying inside the lines.

If not, doesn't this make string theory the god of the gaps, where it kinda just makes stuff up about what can't be known?

I don't think that a fair description. String theorists are not throwing up their hands and calling it "magic" or "god's work". They're working their asses off to try to find a portion of their theory that can be tested. They're not just throwing out some nonsense that can't be openly refuted and claiming to be the next Einstein.

String theorists are motivated by the fact that the Standard Model is incomplete. Not only is it incomplete, but also there's no clear hint as to which direction to hunt for the ideas that will complete it. The Standard Model is an open ended collection of ideas that explain a whole heap of a lot, and quite well. However, it doesn't explain everything, and has some glaringly frustrating omissions (like resolving QM with GR). String theories are guesses as to what the next step might be...

If anything, string theories are trying to chase down the God of the Gaps to kill it.

[wufwugy]

So it's like the string theory starts out by tracing the Standard Model, then tries to color it in while staying inside the lines.

How does it do this without making predictions?

So if I have you right, string theories are something like this: take all the math of the standard model, add more math, if it changes the standard model discard it, if it doesn't keep adding math. All the while making no falsifiable predictions.

I know I must be reading this wrong. I was struck by a comment in the reddit thread about how something posited by string theories and was supposedly proven (I think it was Higgs) was also posited by the standard model. This makes me wonder what string theories actually do. Could it be that anything predictable would just be a part of the standard model?

[MadMojoMonkey]

How does it do this without making predictions?

This is sticky, I know. String theories do make predictions.

So far, string theory predictions all fall into one of these categories:
A) The prediction is new, has been observed and the prediction is false
B) The prediction is old, has been observed and the prediction is true
C) The prediction is new, but can not be observed.

The compelling category for serious attention from the physics community at large would be
D) The prediction is new, and can be observed, but has not yet been observed.

If a string theory (or any theory) makes a prediction that falls in the D category, then that will be something to get excited about.

So if I have you right, string theories are something like this: take all the math of the standard model, add more math, if it changes the standard model discard it, if it doesn't keep adding math. All the while making no falsifiable predictions.

I don't know. In practice it might seem like that to a casual observer. It might even actually be like that at times to the theorist.

It's not about adding math. It's about adding a new idea.

Math is a tool of symbolic logic. It is invaluable to physics because the inductive and deductive statements you can make are all readily symbolized. So once you learn how the symbols interact, you have a time saving tool that when you give it (mathematics) a statement, it gives you back equivalent statements. Those return statements may or may not be at all intuitive, but they are always as "true" as the input.

As such, math is a great tool for physicists to use. The ability to generate equivalent statements from any input is why it's so amazing.

So it's not about "adding math". Except in the sense that adding an idea, then using symbols to describe the idea, then using math to manipulate those symbols.... that clearly involves using math... but the math is just shorthand for sentences, and sentences are just expressed ideas.

I know I must be reading this wrong. I was struck by a comment in the reddit thread about how something posited by string theories and was supposedly proven (I think it was Higgs) was also posited by the standard model. This makes me wonder what string theories actually do.

The Higgs Boson has absolutely nothing to do with string theory.

String theories hypothesize a substructure to all existing particles. String theories attempt to explain things which are observed and unexplained by adding the idea of a sub-structure. Specifically, that the substructure is unfathomably tiny strings, whose vibrations look like particles and forces.

String theory could offer an explanation for the sub-structure of a Higgs boson, but the Higgs boson was predicted without using string theory.

If a string theory could explain the whole of the Standard Model without error, and without predicting things that are "false", then that would be a huge thing.

It would mean that we have 2 seemingly equivalent frameworks to use as accurate descriptions. Which means that there would be a higher likelihood that strings are a valid description for the sub-structure of everything.

Could it be that anything predictable would just be a part of the standard model?

That's the idea. If the preexisting theories are shown to be less robust than a new theory, then the old theory is out and the new theory is in.

If a string theory effectively unifies all known matter and forces and their interactions into one single theory, then there's a great chance that theory's name would stick around.

[wufwugy]

If a string theory could explain the whole of the Standard Model without error, and without predicting things that are "false", then that would be a huge thing.

So is it true that all string theories so far have not been able to explain the current standard model without also positing things that are known to be false? Or have some created a framework that explains everything but isn't testable so there's no way to know? If not, what's the furthest that a theory has gotten? Like has there been unity of the four forces but only in an unfalsifiable way? Or has every unity of the forces done things like posit additional unknown forces?

Related question: is there a way to know if something is true based exclusively on the math? Or is it that math can operate within its own systems, so even a mathematical model that explains every known thing perfectly may still be false?

[BorisTheSpider]

Related question: is there a way to know if something is true based exclusively on the math? Or is it that math can operate within its own systems, so even a mathematical model that explains every known thing perfectly may still be false?

I'll wait for MMMs answer as far as the physics goes, but as an interesting tangent:

http://en.wikipedia.org/wiki/G%C3%B6...eness_theorems

http://en.wikipedia.org/wiki/Entscheidungsproblem

One of the themes of early 20th century mathematics was the attempt to prove that our systems of mathematics were internally consistent - that is to say, if we had a set of axioms and a system such as the natural numbers, that we could, in theory at least, prove that every true statement in that system was true, or that we could, in theory at least, construct a hypothetical "maths machine" that could take a statement and decide it's truth or falseness. In many ways, this parrallels newtonian physics - the idea that even if only in theory, we could predict/understand all the physical phenomena in the universe.

Both physics and maths turned out to be more subtle than was believed, physics with the discovery of relativity and quantum theories, and mathematics with Godel/Turing and the work done on computability/decidability and the discovery that, to state Godels theorem in the plainest way, if a mathematical system is internally consistent then it must not be complete (there must be things we can't state or prove within it), and that quite aside from that a system can't be used to prove it's own consistency.

[wufwugy]

to state Godels theorem in the plainest way, if a mathematical system is internally consistent then it must not be complete (there must be things we can't state or prove within it), and that quite aside from that a system can't be used to prove it's own consistency.

doesn't that mean that a "theory of everything" is impossible?

[BorisTheSpider]

doesn't that mean that a "theory of everything" is impossible?

My best answer to that would be, that physics doesn't have a single proof of anything in it. Physics concerns itself with making theories about nature then comparing the predictions of those theories with observation, if a theory makes predictions that agree closely with observation, the best we can do is say that the theory is an accurate model of nature, but we can't prove anything, and to get a little philosophical we can't say what nature "is".

So a "theory of everything", which I take to mean a unified theory that unites all the fundamental forces, certainly seems to be possible - but we'll never be able to prove it's true, merely say that as we further and further refine our experiments/observations we'll have a higher and higher degree of confidence in it's validity the more closely we see its predictions according with our observations.

[MadMojoMonkey]

So is it true that all string theories so far have not been able to explain the current standard model without also positing things that are known to be false?

Some string theories make predictions that are known to be false. E.g. if it predicted that an electron should have a mass of a star, that would clearly be a poor description. Most make predictions that are unable to be determined as true or false.

Or have some created a framework that explains everything but isn't testable so there's no way to know?

As far as I know, no string theory completely overlaps with the Standard Model... they don't even come close.

If there was a string theory that did "explain everything", then it would be of great interest.

If not, what's the furthest that a theory has gotten?

I don't really know. Not so far as to reconcile even one chapter of a physics book, much less all the chapters in all the physics books.

I'm not current in the field and people with PhD's in physics are working on these theories. When I do try to read them, I don't get far. I don't really speak the language enough to even figure out which little nibble on the edge of current theory they're attempting to elucidate.

Like has there been unity of the four forces but only in an unfalsifiable way?

Not to my knowledge.

Or has every unity of the forces done things like posit additional unknown forces?

I really don't know.

Related question: is there a way to know if something is true based exclusively on the math? Or is it that math can operate within its own systems, so even a mathematical model that explains every known thing perfectly may still be false?

I'd argue that the qualities of "truth" and "falsehood" only exist in math, and math-like logical systems. Without a rigorous logical framework, the ideas of true and false are meaningless.

Science is never true or false. Science isn't really concerned with truth and falsehood, just an honest account of observation. Which brings up a whole bonanza of questions.

If someone hallucinates something, observing it, does that mean it's "real"?
If something is observed by many... does that make it "real"?
If something is unobserved... can it be "real"?
Is a sense of shared subjective observation indicative of an "objective reality" that is observed?

Science can't even answer simple questions like those... so the idea that it's going to reveal some deeper truth about anything is, I think, off base.

The magic of math is that you can give it a statement and then work some mathemagic and return another statement. Whatever the truth of the input statement is identical to the truth of the output statement.

[MadMojoMonkey]

Just shoot me over the whole saying science isn't concerned with true and false and using the words true and false over and over ITT.

It's just too easy to fall into that trap of saying something is right because we're 99.99999999999999999999999999999999999% sure it's right.

Rigorously speaking, nothing I speak of is "true" from a scientific perspective. I hope it's clear that I'm only the vaguest, slightest, tiniest, most miniscule bit uncertain about most of it.

[wufwugy]

Thanks for the responses. It's just fascinating to me that physicists have such trouble unifying gravity with the other three forces. I mean, it doesn't fascinate me that a theory of everything might not exist, as I think the ultimate state of truth is also a state of non-truth, but being unable to unify the forces seems a strange thing to not be able to do

Obviously I'm wrong, just saying

[wufwugy]

Just shoot me over the whole saying science isn't concerned with true and false and using the words true and false over and over ITT.

It's just too easy to fall into that trap of saying something is right because we're 99.99999999999999999999999999999999999% sure it's right.

Rigorously speaking, nothing I speak of is "true" from a scientific perspective. I hope it's clear that I'm only the vaguest, slightest, tiniest, most miniscule bit uncertain about most of it.

A long time ago I was raked over the coals by somebody smarter than me who did his best to explain why nothing can be truly known: the foundation is always an assumption. Even if it works every time it's observed, because information isn't 100%, it's still an assumption

[MadMojoMonkey]

doesn't that mean that a "theory of everything" is impossible?

My best answer to that would be, that physics doesn't have a single proof of anything in it. Physics concerns itself with making theories about nature then comparing the predictions of those theories with observation, if a theory makes predictions that agree closely with observation, the best we can do is say that the theory is an accurate model of nature, but we can't prove anything, and to get a little philosophical we can't say what nature "is".

So a "theory of everything", which I take to mean a unified theory that unites all the fundamental forces, certainly seems to be possible - but we'll never be able to prove it's true, merely say that as we further and further refine our experiments/observations we'll have a higher and higher degree of confidence in it's validity the more closely we see its predictions according with our observations.

I don't think that's what the Godel's Incompleteness Theories say about physics.

We posit our axioms as true within the mathematical framework. How that model matches up to observation is independent to how those axioms work within the framework they generate. Mathematically speaking, axioms are true by definition.

The GIT's say that no matter how many axioms we put into the system, there will always be statements within the framework of the system which cannot be proven true or false by the axioms, and no finite number of axioms can relieve this property.

I really don't know how to think of this in terms of a canonical set of physical laws.

[BorisTheSpider]

I don't think that's what the Godel's Incompleteness Theories say about physics.

Yes I wasn't trying to imply that GIT had anything to say about physics. What I was mainly saying was, physics doesn't concern itself with rigorous proof.

So in a sense, there are two ways to answer "even a mathematical model that explains every known thing perfectly may still be false?" - firstly, the physics answer: "how could we ever know it explained every known thing perfectly? we could arbitrarily approach "perfectly" as our measurements got more and more accurate, but we could never reach a perfect standard of measurement", and secondly the maths answer: "assuming the human mind is equivalent to a turing machine, no-one could ever prove that our systems of mathematics are consistent, the model itself may be inconsistent and we couldn't know it anyway"

The GIT's say that no matter how many axioms we put into the system, there will always be statements within the framework of the system which cannot be proven true or false by the axioms, and no finite number of axioms can relieve this property.

Yeah, and further than that, it also says that, in any system we might devise which is at least as complex as basic arithmetic (peanos axioms and the natural numbers), that it is impossible (algorithmically) to prove a systems consistency within that system.

It's possible (but now we're really going down the rabbit hole) that human mathematical creativity is not algorithmic - ie. the mind is not equivalent to a turing machine, in which case Godels theorem doesn't apply to us.

[seven-deuce]

2 cameras on tripods. All you need is 1 camera, but it takes a lot longer to shoot it all. The tripod is mandatory.

For setup, each camera outputs to a single screen which blends the images 50/50 so that the cameras can be aligned to view identical images, but on different floors of the stairwell.

Then it's just finding willing participants for the prank, and a clever editor.

There's some other hand-cam work being done there, but the basic premise is the same.

It's MIT, man... too many nerds with access to cool technological shizzle wizzle... and a historical reputation for epic pranks.

Kinda disappointed about the stairs thought they were real.

This is pretty cool.

[chemist]

I don't think that's what the Godel's Incompleteness Theories say about physics.
. . .
The GIT's say that no matter how many axioms we put into the system, there will always be statements within the framework of the system which cannot be proven true or false by the axioms, and no finite number of axioms can relieve this property.

I'm fairly certain that if I am thinking, then something has to be doing the thinking.

[MadMojoMonkey]

Quantum Tunneling is an excellently non-intuitive discovery of Quantum Mechanics. The fusion in the sun wouldn't happen at the temperature that it does if not for proton-on-proton tunneling. There's a few steps in the chain, and more than one chain, but they begin with tunneling.

@Chemist: I don't see any connection between GIT and "Cogito Ergo Sum".
Presupposing your own existence is an axiom, and therefore absolutely true within the system it creates.

Please expound on this... I don't see what you're getting at.

[MadMojoMonkey]

If the radius of a pizza is z, and the height of the pizza is a,
then a good approximation for the volume of the pizza is
Pi(z)(z)(a)

[eugmac]

right... pi(r)^2(h). what's so amazing about that?

[MadMojoMonkey]

right... pi(r)^2(h). what's so amazing about that?

Volume of Pizza = Pizza.

[Savy]

That's the type of shit that puts kids off physics.

[MadMojoMonkey]

That's the type of shit that puts kids off physics.

It's a post like this that makes it so so easy read everything you write as the voice of a petulant teenager.

Anyone who is turned off a subject because of a little pun was probably never going to be interested in the subject in the first place.

EDIT: It's not even a joke about physics.

[Savy]

What's the probabillity that MMM takes a joke poking fun at him to heart?

[eugmac]

oh it was a joke

[eugmac]

joke thred down the hall

[kingnat]

How did you develop your skills as a good physics explainer person? I actually has a phd in physics, and I know and can explain a fair number of things itt, but you do an outstanding job on a lot of topics that aren't typically covered in the standard curriculum. Cheers!

[wufwugy]

til a phd in beards that banged ur gf isnt the only one kingnat has

[MadMojoMonkey]

How did you develop your skills as a good physics explainer person? I actually has a phd in physics, and I know and can explain a fair number of things itt, but you do an outstanding job on a lot of topics that aren't typically covered in the standard curriculum. Cheers!

[sarcasm]
So... you're telling me:
A) You are pretty (ugly?) enough to be mistaken for a member of the band Metallica
B) You're a musician who's actually gigging
and
C) You have a PhD in physics
... ?!

Fuck you, man... Fuck, fuckin', you.
You gotta come into my thread where I pretend to be smart about stuff and you show me up on 3 fronts?

What's next... You want to brag about your Christmas dinner with Brian May and Niel DeGrasse Tyson?

My impression of Kingnat:
"Lolz, look at the 'tarded monkey.
His pic is of an ape, not a monkey. Whatta boob!
He talks about music like as though he played more than a handful of gigs a decade ago, like he's not a washed-up has-been.
He talks about physics as though he's got 3 times as much actual training in the field as he does."

til a phd in beards that banged ur gf isnt the only one kingnat has

This.
[/sarcasm]
***
Oh wait. You're complimenting me? As in, you think I'm not the dumb?

Awwwww.... thanks, man. You're the king (nat).
***
On being a good explainer person:

I don't know. I've always been a good communicator. I've repeatedly been told that I should be a teacher, and I've repeatedly not pursued that job because I am equally capable of being a physicist or engineer, and those professions pay a lot more.

Still, there is a teacher in me that wants to be validated by being right and convincing other people to agree with me. It's not a very scientific motivation, but it makes a great compliment to scientific rigor.

I find one of my greatest challenges to keep myself from talking about half-baked ideas in the same voice as when I talk about physics. It's hard to avoid the blending of knowledge and speculation when I'm talking casually.


The amount of time and number of revisions that go into the posts in this thread are probably going unnoticed. If we were to talk face to face, I doubt that I'd come across as this well-spoken. I say the wrong thing many times before I refine it to something that I think my professors would not cringe at.

[wufwugy]

because black holes consume everything and get their consumption powers based on how much they consume, doesn't that mean they eventually consume everything?

[MadMojoMonkey]

because black holes consume everything and get their consumption powers based on how much they consume, doesn't that mean they eventually consume everything?

I delved into black holes a bit in this post, and I feel like you might find some interesting and relevant info there.

In short... black holes act no different than a moon, planet, or star when it comes to "consuming". They are more massive, and therefore have a more long-reaching effect on their surrounding space. They do not "suck stuff in" like a vacuum, except during transient events.

Bear in mind that, on a universal scale, "transient" can mean a process that "only" lasts for a few tens of millions of years.


If there is a binary star system, one of the stars sometimes accumulates mass by accretion (a gradual process whereby one object slowly expands into another object's gravity well, and falls into it) from the other star.

If one object is a neutron star which accumulates enough mass to become a black hole, then it will do that. It will not "suck in" the other star, except that it already was... before it was a black hole... and that's how it became a black hole. It won't instantly expand to envelope the other star... if anything it will contract under it's acquired mass.

If there were any planets in orbit around this binary system, they would remain in orbit unaffected during this change. From a certain distance, nothing has changed. There's x amount of mass, forming a gravitational center in y direction, at z distance. That doesn't change whether it's a star or a black hole or a bunch of either.

It's only when you're "up close" to one that it would matter.


Also, don't forget that "black hole" is a misnomer that was pointed out by Stephen Hawking. Hawking radiation spews out of black holes. They "burn out" over time.

[MadMojoMonkey]

How did you develop your skills as a good physics explainer person?

It just occurred to me that during my formative years (16 - 21), I had a group of friends and one of our standards of determining knowledge from teenage BS was, "If you can't explain it, then you don't understand it."

I thoroughly believe this.

[kingnat]

"If you can't explain it, then you don't understand it."

I thoroughly believe this.

I think this is true as well. I also, probably more than most people, am very comfortable admitting when I don't know something. I use this to balance my need for actually learning all the nuance to challenging questions, if that makes sense. I know some of things pretty well, and I probably know enough to satisfy most standard questions, but a few of the typical trolling physics questions take some thought, and I always feel imposter-y when i can't figure them out instantly.

I certainly reads like you totally know your shit. I haven't done a careful review, but I haven't seen anything that I can see is incorrect. I figured you actually had a phd, tbh. It's a great thread.

[kingnat]

I'd love to see a back-of-the-envelope-type calculation for this: http://www.viralnova.com/backyard-igloo/ that gives me reasonable confidence that something this size, with blocks this small has a very low chance of failure.

[wufwugy]

I'd love to see a back-of-the-envelope-type calculation for this: http://www.viralnova.com/backyard-igloo/ that gives me reasonable confidence that something this size, with blocks this small has a very low chance of failure.

If they were to fall, where would they fall?

IIRC the earliest examples of stable stonework above empty space is the arch. It works. Because it has no where to fall to

[MadMojoMonkey]

I'd love to see a back-of-the-envelope-type calculation for this: http://www.viralnova.com/backyard-igloo/ that gives me reasonable confidence that something this size, with blocks this small has a very low chance of failure.

A dome is an incredibly stable structure, allowing for a lot of tolerance in deviation from the ideal shape.

Consider a hemi-spherical soap bubble on the surface of the dish water. A bubble is perfectly stable under the load of it's thin shell up to a certain size. Comparing the diameter of a large soap bubble to thickness of the bubble's shell is a pretty large number.

Since there's no pressure loading on the igloo shell, it all comes down to supporting its own weight, which it would do, even if it was much thinner than the 4 inches it looks to be.

So it comes down to loading. It's a practical aerodynamic shape, adjacent to the ground. My guess is that it would stand up to extreme winds in excess of 100 mph. Perhaps twice as high.

Additionally... I think a lake only needs to be frozen 6" thick to play hockey on it. This link seems to confirm that notion. According to this, at 4 inches of ice, a frozen lake is thick enough to ice fish.

If 4 inches with a transverse load of a human is safe enough to encourage the public to walk out on to it, then a 4 inch thick igloo that is adequately mortared should be able to support a person standing and maybe even jumping on it... maybe not even a thin person.

The snow-crete is a very nice mortar for this structure. If it's done right, it has just enough moisture to make a material bond with the ice blocks it's holding in place. Even if it's a little weak, you can add water and more snow in the joints and shore it up. It's a very strong structure because you're effectively welding the ice blocks together.

***
I can break out some calculations for thin shell structures, but they're in the context of pressure vessels, and so the loading isn't the same. Nonetheless, thin hemispherical shells are amazingly efficient structures when pressure loaded. An inverted, weighted caternary (a la the St Louis Gateway Arch) is designed to have equal stress in all sections. If you built the igloo in this manner, you could make one the size of a large house, I'd wager. It's not like ice is weak in compression.

[!Luck]

Not sure if physics question, but not sober:

If all particles have formula for action even if its stochastic in nature doesn't that imply there is no free will?

[MadMojoMonkey]

Not sure if physics question, but not sober:

If all particles have formula for action even if its stochastic in nature doesn't that imply there is no free will?

I don't know. It sure feels like free will, whatever it is.

I have deleted so many attempted responses to this question that it deserves mention.

Bottom line is that there is a huge gap in understanding between the atomic world and our selves. Physics -> chemistry -> biology -> neurology -> psychology... We have many fields of study bridging the gaps, but I'd say it's a stretch to say that humans understand consciousness and/or free will.

I don't see any time in the near future where physics will be able to describe all the atoms in 1 biological cell, much less complex biological systems composed of many moles of cells.

So I don't think physics will be able to answer this question any time soon.

[wufwugy]

The best answer I can come up with to the free will thing is that it doesn't matter what the answer is and it's probably an unsound question, sorta like asking what the internet was like before the internet existed.

It's possible the uncertainty principle analogy works here in that the act of observation changes the information. This could work in that if free will is perceived in a determined world, it is free will. It could also work in what are ultimately the same properties behave both in determined and free ways. As paradoxical as that may sound, I have little problem with suggesting that the foundation of existence is itself a paradox

[a500lbgorilla]

A great motivator for anyone getting a whiff of what MMM is cooking and thinking they might want to dive in.

http://fledglingphysicist.com/2013/1...cs-so-can-you/

Basically a girl goes from 0 to physicist in a couple of years.

"If I can sit here and calculate the Debye temperature, you can too. If I can sit here and find Green’s functions, by god, you can too. If I can bang my head against my desk in frustration because I can’t figure out how to solve some crazy stat mech problem, you can too. If I can stay awake at night freaking out about the EPR paradox and the foundations of quantum mechanics, you damn well can too. Seriously. Instead of watching an extra hour of TV, go pick up a calculus textbook, or a book about the standard model – anything!"

[MadMojoMonkey]

Excellent article. This bit resonates with me:

"I decided to take a course on quantum field theory. Not to sound cheesy, but it was like the sky had opened up. I saw how beautiful and elegant physics was, and I realized how stupid and sad it was that only a select group of people who have been deemed “smart” were ever given the opportunity to learn about this."

[wufwugy]

Article is kinda strange to me. I guess around here "not being a math person" is something we impose on ourselves, not something we're told by teachers

[MadMojoMonkey]

Article is kinda strange to me. I guess around here "not being a math person" is something we impose on ourselves, not something we're told by teachers

I don't know what you're asking.

If someone chooses to avoid learning math because they're just not interested in the topic, then that's fine. It's disingenuous to claim that they lack aptitude math when they only lack motivation to learn math.

It's easy to claim to be "not a math person" and use that as an excuse to be lazy about numbers. I'm not accusing you, wuf, or anyone in particular of thinking this way. I just come across this attitude all the time, and at least some people are only held back in math because they didn't realize they were just being lazy about thinking about numbers.

[wufwugy]

That's what I'm saying. I've seen lots of people claim they're bad at math, but I've not seen many people claim others can't get good at math. In the article, she claims that she got a lot of pressure from others that she shouldn't be doing math

[Savy]

That's what I'm saying. I've seen lots of people claim they're bad at math, but I've not seen many people claim others can't get good at math. In the article, she claims that she got a lot of pressure from others that she shouldn't be doing math

Because you're not a woman.

I know loads of people who got told they shouldn't do maths A-Level because they'd fail (16-18 year old exam) when in reality it's really easy. I could get anyone willing to put in some time and an average IQ to get an A. And I'm not the important part in that equation, anyone capable of teaching math could.

The reality is though they aren't getting told they can't do it not because they aren't capable, but because they lack the motivation to put the time in. The problem is pretending it's as simple as just doing a bit of work. Everything is basically that simple, but the reality is the hard part is being motivated.

[wufwugy]

hmmm the sexist answer is likely. maybe not for where i live -- this is one of the most anti-sexist regions in the world -- but for some place like arizona -- where the author says she's from -- it could easily be the deciding factor

[a500lbgorilla]

Because you're not a woman.

I know loads of people who got told they shouldn't do maths A-Level because they'd fail (16-18 year old exam) when in reality it's really easy. I could get anyone willing to put in some time and an average IQ to get an A. And I'm not the important part in that equation, anyone capable of teaching math could.

The reality is though they aren't getting told they can't do it not because they aren't capable, but because they lack the motivation to put the time in. The problem is pretending it's as simple as just doing a bit of work. Everything is basically that simple, but the reality is the hard part is being motivated.

That's pretty much the story of most skills. If you can grab at that spark of motivation and keep those embers lit, you can go very far.

You think Arnold Schwarzenegger doesn't think you could get beyond ripped if you kept it up at the Gym and in the Kitchen? Just gotta get it in your gut to go.

[wufwugy]

dude used to put dianabol in his cereal

[kingnat]

A dome is an incredibly stable structure, allowing for a lot of tolerance in deviation from the ideal shape.

Consider a hemi-spherical soap bubble on the surface of the dish water. A bubble is perfectly stable under the load of it's thin shell up to a certain size. Comparing the diameter of a large soap bubble to thickness of the bubble's shell is a pretty large number.

Since there's no pressure loading on the igloo shell, it all comes down to supporting its own weight, which it would do, even if it was much thinner than the 4 inches it looks to be.

So it comes down to loading. It's a practical aerodynamic shape, adjacent to the ground. My guess is that it would stand up to extreme winds in excess of 100 mph. Perhaps twice as high.

Additionally... I think a lake only needs to be frozen 6" thick to play hockey on it. This link seems to confirm that notion. According to this, at 4 inches of ice, a frozen lake is thick enough to ice fish.

If 4 inches with a transverse load of a human is safe enough to encourage the public to walk out on to it, then a 4 inch thick igloo that is adequately mortared should be able to support a person standing and maybe even jumping on it... maybe not even a thin person.

The snow-crete is a very nice mortar for this structure. If it's done right, it has just enough moisture to make a material bond with the ice blocks it's holding in place. Even if it's a little weak, you can add water and more snow in the joints and shore it up. It's a very strong structure because you're effectively welding the ice blocks together.

***
I can break out some calculations for thin shell structures, but they're in the context of pressure vessels, and so the loading isn't the same. Nonetheless, thin hemispherical shells are amazingly efficient structures when pressure loaded. An inverted, weighted caternary (a la the St Louis Gateway Arch) is designed to have equal stress in all sections. If you built the igloo in this manner, you could make one the size of a large house, I'd wager. It's not like ice is weak in compression.

BTW...

It's 12 ft in diameter, i.e., fucking huge compared to the original.

[Renton]

Grunching so sorry if something similar has been asked.

Can you concisely explain states of matter and how boiling and freezing points work? Like taking water for example, it's freezing point is 0 degrees celsius. Does that mean that any water that reaches below 0 is automatically ice? Similarly is any water that reaches the boiling point steam instantly?

[MadMojoMonkey]

I sprained my left wrist yesterday when I came across some motherfucker hitting a woman. I tackled/punched him and landed on my wrist. I can only type with one hand right now, so I'll answer this question more deeply in a couple of days.

In the meantime, here's a decent link about the thermodynamics of water

It's always about energy. If it is energetically favorable, it will happen. In a prior post, I talked about freezing point of water having a link to the pressure as well as the temperature.

Suffice to say that it would be very difficult to make soup if all the water simultaneously vaporized (exploded) when a certain amount of heat was achieved. When any fluid reaches a temperature and pressure where a phase change would occur, then it can exist in either (sometimes all) of the possible phases. Only when enough heat has been added or removed (or the pressure changed to accomplish the same) so that all the particles are the same phase- only then will the temperature of the fluid be able to change (on a large scale).

Fun fact:
If you watch a pot of water as it just begins to boil, you can see bubbles form on the bottom. As the first bubbles become buoyant enough to detach from the bottom surface of the pan, they begin to rise. However, they never reach the surface of the water because all of their "extra" heat was absorbed by the water above them, and the bubbles turned back into water. This is one of the thermal mixing processes in a pot of boiling water.

Fun fact:
In superfluid helium, quantum effects make the fluid transmit thermal information "perfectly" throughout the liquid. As such, there can be no "localized" spot to boil. Superfluid Helium doesn't boil, even though it is rapidly evaporating, because every molecule of the fluid is the same temperature.

[MadMojoMonkey]

BTW...

It's 12 ft in diameter, i.e., fucking huge compared to the original.

I feel compelled to point out that an "igloo" is a cartoon invention, as far as I can tell. I would LOVE to see a link to any indigenous people using an igloo as a normal part of their daily lives. I found lots of variations on the practice of making a temporary shelter out of ice/snow, but none of them are what I'd consider an igloo.

Also, having made and used a snow shelter in Boy Scouts, I can tell you that if you can't keep the wind out, you've wasted your time. If you're going to sleep in it, you'll want a (at least mostly) sealed door, and a small roof vent so you can put a camping stove or small campfire inside. This will cause the walls to slowly melt, but so slowly that it's not relevant. However, the water runoff will ruin your comfort if you don't prepare for it. 1) The door to the igloo goes downhill. 2) carve a fist-sized groove in the floor around the wall on the inside and out the door. 3) Never put anything in the groove.