**Ask a monkey a physics question thread**

[MadMojoMonkey]

Well, as per the big oil thing... I have only heard a bunch of paranoid questions which bear no proof or even a direct accusation. It's just "Oh they would totally do XXX, 'cause they're evil." I'm not convinced. If someone wants to accuse them of a specific act, then I will gladly hear the evidence of that act. Otherwise, it's just hippy-styled fear mongering.

The meteor thing is harder to answer, because I'm assuming that the object falling is roughly spherical... which is close enough for any blunt re-entry vehicle, but if you really want to damage the ground, then a thin cylinder is probably the best shape. I mean... rockets are that shape because once you've moved the air out of your way, it's best to keep as much of your vehicle behind that front portion so you don't have to move any more air out of your way. The same would hold on your way down, it's just that we are usually interested in maximizing deceleration for as cheap as possible on the way down. Hence the Apollo manned landing modules were largest at the front and tapered behind that, instead of a cylinder with nose cone.

If your entry vehicle wants to have as much kinetic energy as possible when impacting the ground, then a cylinder w/ nose cone would be better than a blunt shape. This would mean less atmospheric heating, less plasma, less brightness of the meteor streak it leaves as it falls.

Bear in mind that whatever falls to the ground is going to be there to be found at the center of the crater. Maybe buried by a few feet of debris, but it'll def. be there. If 2 tons of Tungsten fell onto a spot, there will be a significant Tungsten deposit (I suspect with evidence of recent exposure to the vacuum and radiation environment conditions of space).


A shooting star is def. covered with heavy metals which fracture and fly away (ablate) as it falls. The meteorite is generally quite cold upon impact with the ground, because the heated material has been stripped away from the inner, colder material. This is exactly what inspired the Apollo missions to create ablative heat shields.

[OngBonga]

Oh these things aren't spherical. They're long and very aerodynamic. Hence, rods, not balls. At the velocities we're talking about, I'm assuming it's going to penetrate very deep indeed. They are bunker busters... they could take out a nuclear bunker... at least so it's theorised. I don't think they'll be finding tungsten a few feet under debris. More like half a mile underneath a crater.



As for the mass of these things, well I've seen various figures, from 2 to 5 tonnes. Obviously I'm not finding any credible sources, it's all the kind of hogwash one associates with conspiracy theories. People jumping to conclusions or quoting "unnamed sources" etc.

I'm thinking that maybe these can go unnoticed from ground level. If they're coated, any light emitted would be very high up and might just look a little strange but otherwise innocent from ground level. But I'm still struggling with the cost of getting them up there. I think for this to happen, we need secret propulsion technology. While I might entertain that idea, it's not something I seriously think is out there.

So I remain very much skeptical of this one.

Not like the oil industry being a bunch of evil bastards. There's no skeptism there!

[MadMojoMonkey]

Stuff doesn't bury itself upon impact as deeply as you might think. Crazy as it seems, a first approximation was done by Newton.
Wikipedia Impact Depth

The density of Tungsten is ~19.25 g/cm^3. The density of the Earth's crust is ~2.2 g/cm^3
It's going to penetrate (19.25 / 2.2)*L ~= 7.5 times it's length.

We need an estimate of its length, now.

The total volume of 2 tons of Tungsten is ~100 Liters. (estimating 2 tons as ~1800 kg = 1.8(10)^6 g, then dividing by 19.25 g/cm^3 and converting to liters)

Using a ruler, I measure the diameter of those things in your picture as ~2 mm, and the length as ~25 mm. Matching this ratio, I find a cylinder with a volume of 100 L is ~22 cm in diameter and ~275 cm long.

So 275 cm * 7.5 ~= 2000 cm ~= 20 m

More than a "few feet," I grant you, but closer to that than "half a mile".

***
I don't see why the cost of getting them up there is even worth batting an eye about. You could fit 7 of these at 2 tons each as the payload on a Falcon 9. It is widely known that the US military had its own private access to the Space Shuttle program. They still have a space drone. Since when has the US military let a little funding slow them down?

It's at least plausible that these things could be up there.

***
Your argument amounts to saying "Since they're evil, they're definitely doing every evil thing that I can imagine."

[OngBonga]

The density of Tungsten is ~19.25 g/cm^3. The density of the Earth's crust is ~2.2 g/cm^3
It's going to penetrate (19.25 / 2.2)*L ~= 7.5 times it's length.

This appears to be missing a factor.

For example, according to this calculation, the rod will penetrate exactly the same depth at 10mph and MACH 10, because its velocity is not taken into account. I only see density and length being considered.

What am I missing here?

It's at least plausible that these things could be up there.

Um, really? They could afford to take these things up there? My skeptisism is evaporating.

Since when has the US military let a little funding slow them down?

I wasn't thinking of a "little" funding, I was assuming it would cost a ridiculous amount.

Your argument amounts to saying "Since they're evil, they're definitely doing every evil thing that I can imagine."

Not at all. I haven't accused the oil companies of the recent terrorist attack in Nice. All I've accused them of in this thread is stifling energy technology, which is something they would have a vested interest in doing.

[MadMojoMonkey]

This appears to be missing a factor.

For example, according to this calculation, the rod will penetrate exactly the same depth at 10mph and MACH 10, because its velocity is not taken into account. I only see density and length being considered.

What am I missing here?

I'm guessing you didn't click on the wiki link I posted. The wiki page is very short, but here's the meaty bit:

Newton's approximation for the impact depth for projectiles at high velocities is based only on momentum considerations. Nothing is said about where the impactor's kinetic energy goes, nor what happens to the momentum after the projectile is stopped.


The basic idea is simple: The impactor carries a given momentum. To stop the impactor, this momentum must be transferred onto another mass. Since the impactor's velocity is so high that cohesion within the target material can be neglected, the momentum can only be transferred to the material (mass) directly in front of the impactor, which will be pushed at the impactor's speed. If the impactor has pushed a mass equal to its own mass at this speed, its whole momentum has been transferred to the mass in front of it and the impactor will be stopped. For a cylindrical impactor, by the time it stops, it will have penetrated to a depth that is equal to its own length times its relative density with respect to the target material.

Put simply, the speed of the ground being shoved out of the projectile's way is equal to the speed of the projectile, and it cancels out.

Um, really? They could afford to take these things up there? My skeptisism is evaporating.

I wasn't thinking of a "little" funding, I was assuming it would cost a ridiculous amount.

The cost of producing the projectiles is moot. The US armed forces pay through the wazoo for the highest tech munitions that are available. Furthermore, the projectile needs no warhead, so it's significantly cheaper than one which does require a warhead.

The suggested mass of the projectiles is well within max. payload specifications of space-faring rockets.

The US space program exists and our military has private access to it. I think it's a bit naive to assume that they wouldn't be weaponizing space to some degree.

Not at all. I haven't accused the oil companies of the recent terrorist attack in Nice. All I've accused them of in this thread is stifling energy technology, which is something they would have a vested interest in doing.

Fair enough... it's not "every" evil thing you can imagine... just the ones you suppose they have a "vested interest" in.

They also have a vested interest in making boatloads of money and if they have the money and power to suppress some tech, they have the money and power to own that tech and profit off of it.

[OngBonga]

Put simply, the speed of the ground being shoved out of the projectile's way is equal to the speed of the projectile, and it cancels out.

I did take the link and read most of the article, but this wasn't obvious to me.

The US space program exists and our military has private access to it. I think it's a bit naive to assume that they wouldn't be weaponizing space to some degree.

Oh I totally expect them to weapnise space, it's just a question of to what degree we can do so at this moment in time.

They also have a vested interest in making boatloads of money and if they have the money and power to suppress some tech, they have the money and power to own that tech and profit off of it.

I'm really trying to avoid getting too deep into this subject in this thread. It's not physics, it's conspiracy. What I will say is that the next generation of energy should, in theory, be abundant. Oil is scarce. Therefore, oil will be more expensive (and thus higher profit margin), than any theoretical newgen energy. An energy company can sell solar panels, but it can't sell sunlight.

[OngBonga]

Put simply, the speed of the ground being shoved out of the projectile's way is equal to the speed of the projectile, and it cancels out.

To expand on this point.

If I drop a stone on sand from head height, say six foot, it displaces x amount of sand. If I throw it from the same height, it displaces more sand and leaves a larger crater. The stone will be lower in the sand, compared to when I merely dropped it. Right? This isn't logical to me right now.

[MadMojoMonkey]

You're describing peculiarities which only come into play at the final milliseconds of the projectile stopping, after it has slowed down enough for cohesion interactions to take place. This is not the behavior of the interactions for the majority of the impact.

[OngBonga]

Let's think of this another way. If I drop a bullet into water, it will hit the water and begin sinking. If I fire the bullet into water, it will surely travel deeper before slowing to its terminal velocity, assuming that's the correct term for a sinking object in water.

The same is surely true of a meteor. A faster meteor will surely penetrate the atmosphere more than a slower one of equal size and density before slowing to terminal velocity. Am I wrong?

[OngBonga]

You're describing peculiarities which only come into play at the final milliseconds of the projectile stopping, after it has slowed down enough for cohesion interactions to take place. This is not the behavior of the interactions for the majority of the impact.

Right, I think I'm out of my depth trying to think about this.

[MadMojoMonkey]

I'm really trying to avoid getting too deep into this subject in this thread. It's not physics, it's conspiracy. What I will say is that the next generation of energy should, in theory, be abundant. Oil is scarce. Therefore, oil will be more expensive (and thus higher profit margin), than any theoretical newgen energy. An energy company can sell solar panels, but it can't sell sunlight.

Fair enough. I was at first just trying to see if you have a physics question about it, but then I got to the point of pressing a broader standard of evidence-based theories... till I degened down to picking at hypotheticals. my bad.

Solar panels are nowhere near a theoretically viable option to produce the amount of energy we consume. Until I see a solar panel powered mining operation which mines the resources to feed a solar panel factory which is 100% run on solar power, I'm not giving any hope to the solar solution.

It's really got to be nuclear. The energy density of a good nuclear fuel rod is so freakishly many orders of magnitude greater than any chemical reaction can possibly offer.

[OngBonga]

It's really got to be nuclear. The energy density of a good nuclear fuel rod is so freakishly many orders of magnitude greater than any chemical reaction can possibly offer.

This did occur to me as I hit submit, that energy companies can still monopolise nuclear energy.

Still, such an energy revolution would dramtically change the global economic landscape. I'm unconvinced that's in the interests of the powers that be.

Anyway, let's leave this aspect of the conversation alone.

[MadMojoMonkey]

Let's think of this another way. If I drop a bullet into water, it will hit the water and begin sinking. If I fire the bullet into water, it will surely travel deeper before slowing to its terminal velocity, assuming that's the correct term for a sinking object in water.

You might be interested to know that high velocity bullets penetrate the water LESS DEEPLY than low velocity bullets.

https://youtu.be/yvSTuLIjRm8?t=1m41s

There are more videos on the YouTubes about stuff like this.

The same is surely true of a meteor. A faster meteor will surely penetrate the atmosphere more than a slower one of equal size and density before slowing to terminal velocity. Am I wrong?

It's complicated to take non-trivial shapes into account, but the shape is a large factor in how it moves through the atmosphere.

I really don't know the answer to this. The thing with bullets is making me 2nd guess my immediate intuition to agree with you. The faster meteor will ablate more, and lose mass faster, than the slower meteor. The changing mass and size may or may not have a significant difference in the impact with the Earth's crust, as far as energy delivered by the 2 meteorites.

[MadMojoMonkey]

Right, I think I'm out of my depth trying to think about this.

Cohesion is the stickiness between molecules.

When the projectile hits the ground, the difference in the speeds between the projectile and ground is so great that they aren't actually in contact with each other for long enough to establish a chemical bond... a molecular interaction. The projectile's molecules course past the Earth's molecules so rapidly that they don't interact individually, only as a bulk pressure.

[Eric]

Could there be xmen type folks who can see more colors in telescopes than the rest of us? The http://www.digitaljournal.com/article/326976 article says at least one person has been found that can see extra colors.

[MadMojoMonkey]

Could there be xmen type folks who can see more colors in telescopes than the rest of us? The http://www.digitaljournal.com/article/326976 article says at least one person has been found that can see extra colors.

Sure.

I already knew that tetrachromacy was moderately common in women and not known to exist in men. I didn't know that it's rare for a person with 4 cones to have the "extra" cones be active.

As I understand it, the extra cone is between green and red, and wouldn't allow the person to see infrared or ultraviolet.

[Eric]

Sure.


I already knew that tetrachromacy was moderately common in women and not known to exist in men. I didn't know that it's rare for a person with 4 cones to have the "extra" cones be active.

Yeah, that article did a nice job explaining the fact that there is a subset of women in the 4 cone group where the extra cone is active.


On another note, we were watching the Vancouver English Bay fireworks show last night from a distance. As one would think, the light got to us very quickly but the sound waves took longer. It almost sounded like there were two explosions each time, one delayed a little bit from the light and one delayed even more.


We use one word for thunder and another for lightning but they both come from the same event. What are some other examples in the universe where we perceive things to be different when they come from the same event? I guess an obvious answer would be space-time but there are probably quite a few others...

[MadMojoMonkey]

It almost sounded like there were two explosions each time, one delayed a little bit from the light and one delayed even more.

This is almost certainly an echo.

We use one word for thunder and another for lightning but they both come from the same event. What are some other examples in the universe where we perceive things to be different when they come from the same event? I guess an obvious answer would be space-time but there are probably quite a few others...

Whether an object is moving or stationary is a matter of perspective.

Whether a field is electric or magnetic or a combination of both can be a matter of perspective for the above reason, applied to electric charges.

E.g. if you are holding a charged object and you drive past me... to me, your object is a moving charge, hence it creates a magnetic field. To you, it is a stationary charge, hence it creates no magnetic field. We both measure the same total energy in the electromagnetic fields.

I'm sure there are plenty of other things. It is frequently our description (expectation) of a thing or phenomenon which characterizes what we think we perceive.

[Savy]

Right, this is probably wrong but I don't know much about stats.

I'm playing a game where when you win you get to spin a wheel that is split into 10, all equally likely to be landed on. After you spin the wheel you get the reward on that segment. The next time you win you spin the same wheel but 9 parts have a reward and if you land on the 10th you get no reward.

I'm trying to figure out the average number of spins needed to win every prize on the wheel.

First spin you always get a prize.

To get the second prize
(9/10) 1 spin, [1/10][9/10] 2 spins, [1/10]^2 [9/10] 3 spins, etc

Third prize
(8/10) 1 spin, [2/10][8/10] 2 spins, [2/10]^2 [8/10]3 spins, etc

First of all is that correct? I'm pretty sure it is.

Then does it work if I calculate what all of those sequences converge to individually & then add them all together?

So first prize is 1 spin, second prize is 1.1 recurring spins so on average I'd need 2.1 recurring spins to win two prizes?

If this is nonsense which wouldn't surprise me how do I go about doing it? If it's not nonsense is there a better way of doing it?

The number is spat out on n=1 to 10000 seem realistic.

I work out I need ~29.3 spins so I'd round that up and say 30?

If this has worked can I work out the variance just by summing each individual variance and adding them? I think I remember that sometimes this works and sometimes it doesn't and it seems to me this is relatively simple distributions so would work? (If not I don't need an answer explaining why)

[MadMojoMonkey]

@Savy: This is a version of the Coupon Collector's Problem.

Your work looks fine.

For n=10, the average EV per winning spin is SUM(1/n) {for n=1...10} = 2.93 spins.
The EV of total spins to hit each of 10 equally likely values at least once is 30 (10*2.93, rounded up).
The variance is 330 using the method in the link.

For the variance, I plugged the numbers n = 1 to 10 into Excel, created a column of p_i = 1/n, and created a column with (1 - p_i)/p_i^2. The sum of that column is 330, for a standard deviation of ~18.

[Savy]

Brilliant cheers.

[chemist]

Do black holes have measurable mass or energy?
When they swallow stars and galaxies do they not break the first law of thermodynamics for the closed system of the universe?

[chemist]

Is there methane based life on Titan that eats hydrogen?

Dunno.

There is currently no known evidence of extra-terrestrial life. There is a bit of fuzziness there in that amino acids have been found in (I believe) comets and asteroids.

wikipedia "Life on Titan"
If it's there, it's going to be exotic to say the least. We know basically nothing about the origins of life. Our direct evidence only suggests that it happened on Earth (or near enough to Earth and was deposited here).

It would be a huge boon to biology to have another example to study.
Niel DeGrasse Tyson has said that he would be excited just to find DNA anywhere but Earth.

Some researches found a possible cell wall structure which might work.
It's a computer model of a structure with similar properties to a cell wall. It has not been observed in nature (as far as I can tell from the article).

It sounds like this is only one piece of the puzzle. A cell wall is important insofar as it protects the rest of the cell. We still need a model (if not example) of the internal chemistry/biology that makes up the cell.

Going back to an old topic.
"If it's there, it's going to be exotic to say the least."
"Niel DeGrasse Tyson has said that he would be excited just to find DNA anywhere but Earth."

If it is so exotic why would it necessarily have DNA?
Could something exotic without DNA still be considered a life form?

[OngBonga]

Do black holes have measurable mass or energy?

We can measure its gravity, so certainly.

When they swallow stars and galaxies do they not break the first law of thermodynamics for the closed system of the universe?

This is more complex and I should probably leave this to mojo. But I won't.

I don't think so. Because it has gravity, its mass still exists in this universe, it remains part of the closed system that is the universe. It hasn't gone anywhere. The total mass/energy of the universe remains unchanged.

The question for me really is... does a black hole occupy space?

If not, does it travel through space? Or does space travel around it? Is there even a distiction between those two concepts?

[MadMojoMonkey]

Do black holes have measurable mass or energy?

Yes.

In general, the mass of an object is found by observing its effect on other, known masses. We've gotten pretty clever at determining the mass of stars based on their emissions. One of the ways we locate black holes by observing stars in orbits about an unseen object. When that unseen object is of a certain mass and the orbital path of nearby stars brings them close enough to rule out less dense objects, then the only candidate for the source of mass is a black hole.

Check it out!


The orbits of stars within the central 1 square arcsecond of the Milky Way, centered on the location of the central black hole (yellow star symbol). The fuzzy blobs are diffraction-limited star images in a frame taken by the 10-meter Keck telescope in 2004. While every star in this image has been seen to move, estimates of orbital parameters are only possible for those that have had significant curvature detected. The annual average positions for these seven stars are plotted as colored dots, which have increasing color saturation with time. Also plotted are the best fitting simultaneous orbital solutions. These orbits provide the best data yet on the mass of the central black hole.
(Source)

When they swallow stars and galaxies do they not break the first law of thermodynamics for the closed system of the universe?

Dunno. It's a fairly hotly debated topic in physics right now.

I'm not sure that the "closed system of the universe" is a correct description of a universe which contains event horizons, myself.


Stupid black holes being so totally awesome, while also being really, really, really, ... , really far away and hard to experiment on.

[MadMojoMonkey]

Going back to an old topic.
"If it's there, it's going to be exotic to say the least."
"Niel DeGrasse Tyson has said that he would be excited just to find DNA anywhere but Earth."

If it is so exotic why would it necessarily have DNA?
Could something exotic without DNA still be considered a life form?

The first question answers itself. It would be hugely unlikely for it to have DNA if it isn't something that the universe or periodic table favors. If it could be shown that the DNA-having stuff originated from somewhere else, that's huge. (If it turns out it came from here and contaminated to somewhere else, then that's meh.) If it turns out that there is non-DNA-based life, then that's huge.

The second question is probably better answered by a biologist, but my gut says that if it can argue that it is alive, then it's probably best to not argue back that it isn't.

[chemist]

The first question answers itself. It would be hugely unlikely for it to have DNA if it isn't something that the universe or periodic table favors.

That is what I thought and why I was confused by the Niel DeGrasse Tyson statement which I thought was irrelevant to the original answer. Sure non earth originating DNA is interesting but let's not rule out non DNA exotic life.

if it can argue that it is alive, then it's probably best to not argue back that it isn't.

Good Answer.
Unless it is smaller than us, then we could argue with it.
I'd argue with a little monkey but think twice about arguing with a big Gorilla, (unless it was remotely in an online forum).



I'm glad black holes are so far far away that we can't yet measure their change in gravity as they consume galaxies,
though a little concerned that you show the milky way in your example.

(our great great ... great ... great ...great great grandchildren should definitely have a referendum to leave the milky way before that hole takes over)
Yeah I know you're going to point out the sun will have expired long before that happens.

[chemist]

The question for me really is... does a black hole occupy space?
If not, does it travel through space? Or does space travel around it? Is there even a distiction between those two concepts?

As things go in they massively stretch so space and time are being distorted, to some frames of reference, but I don't know what that really means.

[MadMojoMonkey]

That is what I thought and why I was confused by the Niel DeGrasse Tyson statement which I thought was irrelevant to the original answer. Sure non earth originating DNA is interesting but let's not rule out non DNA exotic life.

There's probably a tone issue here. He sometimes answers a question in a way that implies, "Not only would that thing you implied excite me, but this other thing which is much less complicated than your thing would excite me."

I'm glad black holes are so far far away that we can't yet measure their change in gravity as they consume galaxies, though a little concerned that you show the milky way in your example.

Don't be. It's highly speculated that Sagittarius A-star is the reason there is a Milky Way in the first place.

Current hypotheses suggest that there is a Super-Massive Black Hole at the center of every galaxy. Unfortunately, it's pretty hard to directly detect a black hole, even an SMBH. They're generally surrounded by a galaxy of stars, whose emissions shield the core of the galaxy from observation.

(our great great ... great ... great ...great great grandchildren should definitely have a referendum to leave the milky way before that hole takes over)
Yeah I know you're going to point out the sun will have expired long before that happens.

Dude. Humanity isn't leaving the Milky Way. Not ever. Not using any kind of physics I can reasonably speculate. The inter-stellar distances within the Milky Way are prohibitively far, even with hypothetical near-light-speed spaceships. The inter-galactic distances are another unimaginable scale. Humans are stuck with our Milky Way, as I understand it.

BUT...

Black holes don't suck up galaxies any more than stars suck up planets or planets suck up moons. The gravitation is the same in all regimes. It's just that a black hole has an event horizon. Bear in mind that the sun has a photosphere, but it's of no real danger to Earth, because Earth's orbit doesn't go "inside" the sun. So long as an object's orbit doesn't go inside the event horizon on its closes approach, there is no a priori reason that it ever will be "taken over" by the black hole.

[MadMojoMonkey]

As things go in they massively stretch so space and time are being distorted, to some frames of reference, but I don't know what that really means.

If I may...
As things go in they (appear to) stretch (according to a stationary observer, far from any event horizon) because spacetime is distorted by the extreme mass of the black hole, but I have no intuition which helps me understand this.

Stretching of spacetime is caused by the mass of any object. Mass curves spacetime, and the curves in spacetime express forces on masses... this is how GR describes gravity.

[chemist]

If I may...
As things go in they (appear to) stretch (according to a stationary observer, far from any event horizon) because spacetime is distorted by the extreme mass of the black hole, but I have no intuition which helps me understand this.

You may, because I did already say, 'to some frames of reference', ie for example the frame of reference (according to a stationary observer, far from any event horizon) among perhaps others, , but thanks for making it specific and thus clearer.

[MadMojoMonkey]

To clarify again... the objects will actually stretch, as well, as they get "close enough" to the black hole such that the acceleration due to gravity at their feet is significantly greater than the acceleration at their head (or whatever, I'm assuming the feet are pointed "down" toward the black hole). This would be readily observed by anything close enough to see the thing getting stretched. This has nothing to do with GR, per se. It only has to do with feeling different forces across a body. The net force causes acceleration, which increases (theoretically without bound as you get closer and closer to the singularity) and will eventually rip apart whatever bonds are holding that body together - intermolecular bonds, then molecular bonds, then atomic bonds... who knows how far this goes. No point in dwelling on it. QM and GR don't really get along at these energy scales.

This stretching may happen inside or outside the event horizon. This is because event horizons have to do with the magnitude of the net (not necessarily exclusively gravitational) acceleration, whereas the stretching is due to the variation in g-forces (accelerations of a mass due to gravity) felt by objects which occupy some volume.

[Eric]

What do you make of the http://phys.org/news/2016-08-physici...ry-nature.html article? Specifically this part:

The UCI work demonstrates that instead of being a dark photon, the particle may be a "protophobic X boson." While the normal electric force acts on electrons and protons, this newfound boson interacts only with electrons and neutrons - and at an extremely limited range.

[MadMojoMonkey]

The only definition I can find for protophobic is a chemistry term which has to do with the particles of a solvent being able to "donate" pairs of electrons to other particles in the solvent. I can't find any definition which makes sense in terms of particle physics. It doesn't sound like this new thing they've found has got any electrons to donate, since they're hypothesizing that it's a new particle / force.

So I don't know what they're talking about, yet. Give me a bit to ask some fellow physicists.

They're calling it the "X boson" because they claim it is an unknown force. X for unknown and bosons are the force carriers in particle physics.

***
The group claims 6.8 sigma significance on their result, which means there is less than a 1/570,000,000 chance that their result is a statistical fluke, so they're pretty certain they detected something and that it wasn't a fluke. That doesn't rule out systematic error. E.g. if there was a peculiarity of their experimental setup which caused the phenomenon they observed, then their explanation is erroneous. I'm not saying this is the case, just saying what "6.8 sigma" means.

As ever, this experiment needs to be repeated (preferably by multiple groups) in order to show confirmation of the claims.

If it is confirmed, then it will be exciting to read about the new physics, even if it is shown to be a sneaky facet of pre-existing theory.

[MadMojoMonkey]

I have asked 2 PhD's in chemistry and 5 in physics if they know what "protophobic" means... especially with respect to the topics in this article.

No one I've asked has ever heard this word before. I'm still not entirely sure what are the actual claims of this paper.


It is worth noting that the original data was collected by a group in Hungary, and submitted with an explanation.
That data and explanation was reviewed and interpreted by another group at UC Irvine, which said their explanation was in conflict with other known experimental results. So now the Hungarian team has introduced a new explanation which invokes dark matter and other stuff.

The article is publishing the new explanations.
These current explanations have not been interpreted or reviewed by any 3rd parties as of yet.

[Savy]

I'll probably give this a think if I have time but fancy giving me a quick answer to solve this problem. Hearthstone related obviously for those that play (I just started)

If I have a win rate of x% how do I work out the likelihood of me winning a certain number of games given the conditions.

If you lose 3 games you are finished.
If you win 12 games you are finished.

[Savy]

So the combinations are 12W, 12W1L, 12W2L, 11W3L, 10W3L, ..., 1W3L 0W3L

In each of these combos the final result has to be a W when 12W and a L when 3L so can be thought of as a combination of all results except the last.

Each of these can be worked out using (total outcomes)!/ [(W outcomes)!(L outcomes)!]

Example - 8W3L can be thought of as a combo of 8Ws and 2Ls so 10!/(8!2!)

Each outcome has a probability of (x)^W * (1-x)L where x is your win%

By multiplying the # combos with the probability of each happening we get how likely that result is.

edit

Then I assume we can work out our avg # of wins just by doing # wins * how likely for every result.

[MadMojoMonkey]

I'll probably give this a think if I have time but fancy giving me a quick answer to solve this problem. Hearthstone related obviously for those that play (I just started)

If I have a win rate of x% how do I work out the likelihood of me winning a certain number of games given the conditions.

If you lose 3 games you are finished.
If you win 12 games you are finished.

You're asking your EV for the number of wins on an arena run, given your winrate.
Let X be {winrate}.
0 <= X <= 1

Option 1: Your Arena run ends due to acquiring your 3rd loss
For 3 <= N <= 14:
(N - 1) matches produced (N - 3) wins and (2) losses, in whatever order, then the Nth match was your 3rd loss.
EV(N,X) = C(N-1,N-3)*X^(N-3)*(1-X)^2 * (1-X)
EV(N,X) = C(N-1,N-3)*X^(N-3)*(1-X)^3

Option 2: Your Arena run ends due to you defeating the 12th opponent
For 12 <= N <= 14
EV(N,X) = C(N,N-12)*X^(12)*(1-X)^(N-12)


***
I plugged this into Excel and I'm getting less than perfect results, so there's something wrong in there, but I don't see it.
To clarify, for values of 0 < X < 35%, the sum of all of those results rounds to 100.00%
For 35% < X < 64% the sum of all results is over by less than 1%
The error reaches a maximum at X ~= 88%, where the sum of all probabilities is over 106%.

Given these unexplained errors in the results, I show that you need a winrate of X > 80% to have more than 50% EV at winning 12 matches.

***
If anyone sees the error in my analysis, let me know.


EDIT: error found. I forgot to account for the fact that your final match is always a win in option 2.

Correction:
Option 2: Your Arena run ends due to you defeating the 12th opponent
For 12 <= N <= 14
EV(N,X) = C(N-1,N-12)*X^(12)*(1-X)^(N-12)

The sum over both cases for all N yields 100% for any X.

[Eric]

The article is publishing the new explanations.
These current explanations have not been interpreted or reviewed by any 3rd parties as of yet.

I see. Hopefully they'll make some clarifications following 3rd party reviews.

[MadMojoMonkey]

So the combinations are 12W, 12W1L, 12W2L, 11W3L, 10W3L, ..., 1W3L 0W3L

In each of these combos the final result has to be a W when 12W and a L when 3L so can be thought of as a combination of all results except the last.

Each of these can be worked out using (total outcomes)!/ [(W outcomes)!(L outcomes)!]

Example - 8W3L can be thought of as a combo of 8Ws and 2Ls so 10!/(8!2!)

Each outcome has a probability of (x)^W * (1-x)L where x is your win%

By multiplying the # combos with the probability of each happening we get how likely that result is.

edit

Then I assume we can work out our avg # of wins just by doing # wins * how likely for every result.

I didn't see this when I posted my initial response to your question.

This reasoning is spot on.

Your result of 10!/(8!2!) is equivalent to my notation of C(10,8). This is the binomial coefficient.
By symmetry, C(10,8) = C(10,2); just like 10!/(8!2!) = 10!/(2!8!)

To restate my solution here, using your notation of W for number of wins and L for number of losses:

For cases where you lose 3 matches
EV(W,L=3,x) = C(W+3-1,2)*X^W*(1-X)^3

For cases where you win 12 matches
EV(W=12,L,x) = C(12+L-1,L)*X^12*(1-X)^L

For all the "inner" cases, your EV of being in any state of 0 <= W <= 11 and 0 <= L <= 2
EV(W,L,x) = C(W+L,L)*X^W*(1-X)^L
or, by symmetry of the binomial coefficient
EV(W,L,x) = C(W+L,W)*X^W*(1-X)^L

The only notable difference is the "-1" in the binomial coefficient for the "end states" that is not present in the "intermediate states."

I still find that you need x > 81.3% to get a 50% shot at winning 12 matches.

Of course, this all assumes that all matches are of equal difficulty and your winrate taken as an aggregate of all matches is acceptable as an estimator as the Arena progresses to different matches. I think this is not too bad a model, since the arena matches seem to be always against players of roughly your rank +/- 1, therefore roughly equal skill, no matter how many W/L you have.

[MadMojoMonkey]

Who loves graphs?



I DO!!!

[Savy]

I also made an excel sheet!!!! I think it becomes beneficial to play arena rather than spending gold on other things somewhere between the 4 and 5 wins per arena mark and that 7 wins guarentees you enough gold that you always have enough gold to enter another arena whilst getting other rewards too.

Of course, this all assumes that all matches are of equal difficulty and your winrate taken as an aggregate of all matches is acceptable as an estimator as the Arena progresses to different matches. I think this is not too bad a model, since the arena matches seem to be always against players of roughly your rank +/- 1, therefore roughly equal skill, no matter how many W/L you have.

This is actually why I think it's got faults as a model (I thought I'd commented on this somewhere but I had not, was on another forum).

First of all you get to draft a new deck every arena of which some are better and some are worse. I think it's fair to assume that this averages out and can be ignored but I don't have any real explanation for why I think this.

What I don't think averages out is how likely you are to win each game. Assuming your deck can be considered an average deck that deck gets less and less likely to win after every game because the average deck you are playing against and the average player you are playing against (these can be combined into it gets harder) whilst your deck and skill level don't change. So there would be a decrease in likelihood of winning after every win you have*.

I imagine (no strong reason) that this means your results are squished up a bit more and drop down quicker whilst hopefully not having a mental effect on your results. Worth noting that I think the lower your win rate the bigger this effect will be.

That all being said (sorry bit boring) for what I wanted this for it does a sufficient job (how can I say this when I don't actually know?) for what I want it to do (the reason is it's of 0 real importance to anything I'm doing).

*I think it's done on wins so there's no bias in if you've just started you're going to play a 0-0 rather than a 0-2 compared to if you're 0-2 yourself.

[MadMojoMonkey]

I don't think it's done on wins, due to the logistical nightmare of making that happen.

Suppose the server is not too full. Suppose you just beat the only other "good" player on the server for your 11th win.
There are no other players on the server with more than 4 wins.

How long is it going to take before you have a worthy opponent?

It's no good. Players already complain about how long it takes between matches and it's less than 15 seconds in many cases.

Of course, this is all speculation.

There's another point that your opponents are always your rank +/- 1, so that places a further restriction on choosing your opponent if the server also has to match your number of wins.

[Savy]

My results are saying 81.3% win rate gives you a 49.79% chance of getting 12 wins just to clarify that the results match up.

[MadMojoMonkey]

My results are saying 81.3% win rate gives you a 49.79% chance of getting 12 wins just to clarify that the results match up.

Yep.

We're talking about the winrate of your current arena deck, not your winrate outside of arena or with a different arena deck.

The assumption is that the winrate against the 1st opponent is not statistically different than the winrate against any other opponent.

[Savy]

I don't think it's done on wins, due to the logistical nightmare of making that happen.

Suppose the server is not too full. Suppose you just beat the only other "good" player on the server for your 11th win.
There are no other players on the server with more than 4 wins.

How long is it going to take before you have a worthy opponent?

It's no good. Players already complain about how long it takes between matches and it's less than 15 seconds in many cases.

Of course, this is all speculation.

There's another point that your opponents are always your rank +/- 1, so that places a further restriction on choosing your opponent if the server also has to match your number of wins.

I got told that the more wins you have the more variation it accepts so up to like 7 wins you're very likely to get someone on the same number of wins but if you're on 11 wins you could be facing people from 11 wins to 8 wins. No reason for me to think the person would lie but it certainly can't be given as a truth either.

It's all besides the point I was just interested I'm sure someone somewhere will have done a much better more informed model that takes into account these things. There is 100% data that exists which tracks peoples arena runs on a large scale which will give a better picture of how far different people get.

[MadMojoMonkey]

I see. Hopefully they'll make some clarifications following 3rd party reviews.

This may not be a flash in the pan.

I'm still tossing this around my dept. and I've found someone who has the experience to understand the original experiment and who has taken the time to analyze their work and get back to me.

Here is the significant quote:
"I have went back and looked at the original exp. Paper. (PRL 116,042501). I thought I could find a hole but cannot.
It actually looks like a good experiment. There is - in principle - a way to make it much better, but it would be a big technical challenge."
-A qualified and credentialed radiochemist, whose permission I have not asked, so I wont state their name.


This is very similar to the response of the UC Irvine group who said the conclusions weren't robust against other experiments. It is worth noting that they didn't discredit the experiment or the data, only the conclusions, and the extent of discrediting was not for mathematical-physical reasoning, but incompatibility with other known experiments.


Fifth force or no, I'm more convinced that there is something going on here that is more than media sensationalism.

[OngBonga]

Does mould take water directly from humid air, or does it rely on condensation to occur?

[MadMojoMonkey]

Does mould take water directly from humid air, or does it rely on condensation to occur?

Yes. As far as I can tell, the mold doesn't care. There are loads of different species of molds, and they may differ in this. Some molds live underwater, some on the surface of a liquid and some in places which are only occasionally moist. There's a lot of variation in molds.

Again, as far as I can tell:
They absorb water from their environment, and they don't really care whether it's airborne humidity or a standing pool of water.

It may take a condensed pool or prolonged period of wetness for a mold colony to take hold, but once it's there, it will happily lie dormant if the environment becomes desiccated and wait until the humidity goes up, at which point it reactivates. Some molds become powdery when they dry out, making it easier for air currents to take them somewhere else.

[OngBonga]

I just wonder if heating a room is an effective method of stopping mould from taking hold. Warmer air holds more water vapour, so while water volume in air goes up with temperature due to increased evaporation, relative humidity goes down.

But if mould is taking water right out of the air, then warmer air will allow it to colonise faster, so I'm wondering whether it's better to have warm air or cool air when it comes to fighting mould.

Intuition tells me warm air, but I'm not sure.

[MadMojoMonkey]

I just wonder if heating a room is an effective method of stopping mould from taking hold. Warmer air holds more water vapour, so while water volume in air goes up with temperature due to increased evaporation, relative humidity goes down.

But if mould is taking water right out of the air, then warmer air will allow it to colonise faster, so I'm wondering whether it's better to have warm air or cool air when it comes to fighting mould.

Intuition tells me warm air, but I'm not sure.

Temperature is not really relevant, as you've pointed out, it's humidity and condensation. I'm not sure if it's about absolute humidity or relative humidity. I'm certain that temperature matters at extremes, but not sure what counts as extreme to a mold.


A dehumidifier would be best, but really, they produce a huge amount of heat, and can be really unpleasant if they're in the room with you. An AC unit must reduce the humidity below the dew point before it can cool the air below the saturation temp. So using an AC on high is a way to drive down humidity. You can put a space heater in the same room and leech the moisture out of walls, ceilings, floors, furniture, etc. It's not a super-fast process, though, and it's expensive to run a heater and an AC in the same space, obv.


If you are dealing with an established mold colony, and not just using preventative measures, then treat affected areas with Hydrogen Peroxide (not bleach, bleach is too aggressive and has a very high chance of producing airborne mold when used) and don't spray the mold directly. Spray near it and wipe the H2O2 across the moldy area. Inhaling mold spores is bad news. You want to minimize airborne mold especially when cleaning it up. It can kill you if you inhale too much mold. It's no joke. Acute mildew inhalation poisoning happened to a roommate of mine once and he was inpatient hospitalized for a week.

[OngBonga]

Recently, the German government advised their citizens to stockpile essential items, I think they said a week's supply. I heeded that warning, asking myself why they felt the need to tell their citizens this. I have a feeling their central bank is on the brink of collapse, which will have huge financial implications.

I wanna talk about water filters.

I'm curious... let's assume the world has gone to shit and we've run out of bottled water or our regular water supply is compromised. What does mojo do?

I've been looking into water filters, how to make them. The best plan I can come up with so far is to first chlorinate the water, and then pass it through activated carbon. I'll make the activated carbon by first making charcoal, and then treating it with calcium chloride.

Is this sufficient and practical? I currently have a 1kg bag of CaCl2 on order from ebay, and I already have some water purification tablets. These will simply go into storage, and I'll likely increase these supplies over time, adding pool grade cholrine flakes which I intend to buy next week.

What I'd also like to know is how practical it is to make CaCl2, and Cl2, using nature. Let's assume we have a supply of limestone and salt.... we have calcium and chlorine in these compounds. Can they be processed safely to give us Cl2 and CaCl2? I think it's safe to say that electrolysis of molten salt is impractical and unsafe, so that one's out.

If we can't make CaCl2 and Cl2 from salt and lime, are there any other common compounds we can process?

I think this kind of knowledge is worth more than water itself in a post apocolyptic world. I've got 20l of mineral water in storage and will increase that over time, but of course that's a short term solution... effective for bunkering down for a period of time after a disaster, but not effective when it comes to sustaining life indefinitely if infrastructure is compromised.

Also, in your opinion, what would be the most valuable commodities in a collapsed world? Obviously water and water purification methods, but things like salt... it can preserve food, and has chemical properties that can perhaps be exploited. Salt is obvious though, what properties does sugar have other than sweetening?

[Savy]

I think you should lay off the pot for a while mate.

[OngBonga]

I think you should lay off the pot for a while mate.

hahaha

You realise that stockpiling supplies and learning how to filter water is as paranoid as keeping a gun "just in case", right? If I said I wanted a gun for protection, would you say I should stop smoking weed?

[OngBonga]

Deutsche Bank is going to collapse. That isn't me reading crazy websites, that's what I'm told by my friend's mother, who has just retired from her job in finance. Why are they telling their citizens to stockpile? What do they think is going to happen in the coming months?

I don't think it's excessive paranoia to heed such a warning. It's not like I've been prepping since 9/11, which is when my distrust in the system really kicked into gear.

[MadMojoMonkey]

Boy Scout motto is "Be prepared."

They should prob. lay off the pot, amirit?

***
I really don't know much about this. These are all chemistry questions, and not really the kind of stuff I focus on.

***
Best thing would probably be to control a plot of land with adequate ground water, dig a well, and protect that land and well from thieves.

You can purify water by boiling it, which will kill any viruses or bacteria in the water. This wont make the water taste any better, and it wont remove non-biological threats. I believe this is what the chlorine does, i.e. kills biological threats, but not other chemical impurities.

If you up your game a bit and don't drink the boiled water, but rather you use the boiling to evaporate the water, then condense the evaporate and drink that... then you have distilled drinking water. This will be much improved in taste, having separated out sediments and other contaminates from the source water and the distillate.

If you're very careful, you can pass the water through multiple distillation steps at increasing temperatures in each step. This can separate any chemicals with lower or higher boiling points from the water. You only drink the liquid which boiled at the appropriate temperature. I.e. alcohol boils at a lower temp than water. So you can slowly raise the temp of a water/alcohol mixture to a temp where the alcohol evaporates, but the water doesn't. (There will always be a bit of water in there, due to the statistical nature of temp.) Ideally, you started with a water/alcohol mix, and ended with water separate from alcohol. If there is then some other chemical in the water with a higher boiling point, then you distill off the water, leaving that other chemical behind.


All of this is what I remember from purifying lake water as a boy scout and my middle-school chemistry class.

As to sources or methods of acquiring CaCl2, I'm totally ignorant, but maybe Chemist will show up and help you out.

[Poopadoop]

Deutsche Bank is going to collapse. That isn't me reading crazy websites, that's what I'm told by my friend's mother, who has just retired from her job in finance. Why are they telling their citizens to stockpile? What do they think is going to happen in the coming months?

I don't think it's excessive paranoia to heed such a warning. It's not like I've been prepping since 9/11, which is when my distrust in the system really kicked into gear.

I think you're reading too much into things here. The German gov't is only updating advice that was given before. They're also on high alert after all the terrorist shit that's been going on there lately. It's not like they somehow believe the bank's collapse is going to lead to some catastrophic food shortage.

But hey if you have a house full of salt when the zombie apocalypse comes you'll probably be able to trade it for a big bag of weed on the black market.

[OngBonga]

Cool, thanks. Im aware of distillation as a method of purification, I just never really thought it would be practical in the sense it's not easy to collect the vapour. I guess it would be possible to make condensation tubes with aluminium foil, so maybe it is more practical than I thought.

I don't anticipate seperating alcohol and water. If we have any vodka in a world-gone-to-shit scenario, I'm boiling stangant canal water before wasting vodka!

[Poopadoop]

I guess it would be possible to make condensation tubes with aluminium foil

Why ruin a perfectly good hat?

[OngBonga]

I think securing land and protecting it, it's not practical. I have neither land, nor weapons. I live in a town, so unless I'm lucky enough to get into the countryside with someone who does have a means of protection, then finding dirty water, perhaps by digging down to the water table or by collecting rainwater and dew, then cleaning it, this might be a more practical method of survival.

[OngBonga]

Why ruin a perfectly good hat?

My hat is made from tin.

[MadMojoMonkey]

Cool, thanks. Im aware of distillation as a method of purification, I just never really thought it would be practical in the sense it's not easy to collect the vapour. I guess it would be possible to make condensation tubes with aluminium foil, so maybe it is more practical than I thought.

It's not easy to collect all of the vapor w/o a sealed container, you're right. However, that's not really a mandate. As long as you can capture some clean water, then you're doing it. We did this in my 5th grade classroom, so it's not hard. Granted, we used a hot plate to boil the water and a large, flat, shallow pan full of ice held at an angle above the boiling water.

The water boiled. The vapor rose out of the container and then condensed on the bottom of the cold pan. Since the cold pan was at an angle, the condensed water ran down to one end and dripped off of it.

You'd need some other way of making a "cool" surface to do this method, but it doesn't have to be ice cold by any means.

It's perfectly do-able. I mean, distillation is part of the moonshine process. Informed, but not necessarily intelligent, people can do it in the backwoods with a couple of drums and some metal tubing.

I don't anticipate seperating alcohol and water. If we have any vodka in a world-gone-to-shit scenario, I'm boiling stangant canal water before wasting vodka!

If the alcohol is at 1%, you're going to want to distill that out and concentrate it, man!

[Savy]

Boy Scout motto is "Be prepared."

They should prob. lay off the pot, amirit?

Do you struggle with taking this literally when they're not meant that way?

edit - I don't mean that as an insult or anything it's a serious question. A lot of my posts you seem to take too literally. Might be a UK thing.

hahaha

You realise that stockpiling supplies and learning how to filter water is as paranoid as keeping a gun "just in case", right? If I said I wanted a gun for protection, would you say I should stop smoking weed?

I'd tell you to make sure you've hidden your weed well because owning a gun will most likely get the police involved.

Americans are over paranoid creatures, their short terms history facilitates that. If you want to buy loads of water, own a gun etc I'm all for that being ok. I'm not trying to stop you just point out you shouldn't worry yourself too much about these things because they're unrealistic in the short term.

[MadMojoMonkey]

I think securing land and protecting it, it's not practical. I have neither land, nor weapons. I live in a town, so unless I'm lucky enough to get into the countryside with someone who does have a means of protection, then finding dirty water, perhaps by digging down to the water table or by collecting rainwater and dew, then cleaning it, this might be a more practical method of survival.

Before the instillation of clean, public water sources and public sewage removal, cities were death traps. They sustained themselves by immigration. Death rates were much higher than birth rates, and only the influx of people from the surrounding areas kept them populated. If, in your scenario, these public services are non-functional, then you want to GTFO fast.

You do not want to be in a place where the land cannot sustain the population in the event of a zombie apocalypse.

That option of finding a friend, or making a friend, who does have land away from large populations is your best bet.

(I'm making certain assumptions about the size of your town. If your town is small enough where everyone knows everyone else's names, then your community may be small enough to sustain itself.)

[MadMojoMonkey]

Do you struggle with taking this literally when they're not meant that way?

edit - I don't mean that as an insult or anything it's a serious question. A lot of my posts you seem to take too literally. Might be a UK thing.

I sometimes do. I sometimes think it's funny to highlight how silly a turn of phrase is... especially old ones like "let the cat out of the bag" whose literal meanings are completely lost to anachronism.

That was just a joke, though.

***
Thinking about emergency preparedness is a good process to go through in moderation, IMO.

I don't think the zombie apocalypse is upon us, or even the Germans, any time soon, though.

[OngBonga]

I'm not trying to stop you just point out you shouldn't worry yourself too much about these things because they're unrealistic in the short term.

I don't worry too much about it. I just think it's sensible to worry about it enough to the point where you have some idea how to survive if it happens. The signs are there that our financial system is under immense pressure. USA will go to war with anyone to protect the dollar. There is certainly the potential for hard times in the future. I just don't really want to be thinking "I wish I'd learned how to filter water" as I shit a stream of brown liquid.

It doesn't hurt to learn stuff, or discuss what you think you know with people who know better.

[OngBonga]

(I'm making certain assumptions about the size of your town. If your town is small enough where everyone knows everyone else's names, then your community may be small enough to sustain itself.)

Nah, I don't live in a friendly community type place. I'd want to either GTFO or bunker down for long enough for things to settle down. Leaving town would be the best option by far, but it's important to have somewhere to go if you don't want to get shot by a farmer protecting his food and water supply. Plus, travelling might be dangerous, so there's that.

[MadMojoMonkey]

USA will go to war with anyone to protect the dollar.

Not entirely true.

It'd take a lot of years of political pressure to change that we're never going to war with either GB or Israel.
We can probably include Canada in that. Then no one's going to war with the Swiss, like ever.
I think Americans would be opposed, for at least a little while, to war with any Western European nation, really.

I think America has learned its lesson with trying to war with Russia. Russia too stronk.

***
I don't think going to war with China would be a good idea for anyone, but the reasons are totally different. I suspect the only reason USA is left to play the world police in the past 50 years is because the Chinese see how expensive it is for us, and are happy to let us foot that bill while becoming financially indebted to them for it.

That could be is certainly terribly naive on many counts, though.

[MadMojoMonkey]

Umm... this should really be moved to the Rando thread at this point.

[OngBonga]

Yeah this is moving into politics, rather than science.

What happens if Switzerland moves at 90% light speed towards crashing the dollar? Would it happen in Switzerland's future from USA's pov, but USA's past from Switzerland's pov?

[chemist]

... especially old ones like "let the cat out of the bag" whose literal meanings are completely lost to anachronism.

Originally a phrase people frequently had to say to Erwin Schrödinger.

It'd take a lot of years of political pressure to change that we're never going to war with either GB or Israel.
We can probably include Canada in that.

Don't trust those americans they have been planning war with GB since 1920. See War Plan Red, and Canada too, war plan crimson.

[wufwugy]

I asked my chemistry teacher this a while back but didn't get a clear answer. I've returned to the question a few times in my mind, but keep forgetting to ask. I've forgotten much of the chemistry vernacular since then, so bear with me. You know how in intro chem classes one exercise you'll do is calculate the energy to take a quantity of h2o from solid to liquid to gas, and how you have to calculate the energy for the phase changes between solid and liquid then liquid and gas? I recall it being stated along the lines that for the quantity to phase from liquid to gas, the entire thing must be 100C (with perhaps some caveats). At least by the calculations we did, that is suggested to be true.

Anyways, my question is "when I'm making coffee in the morning and I'm bringing water to a boil, once the first bubble appears, does that mean that the entire pot is 100C?" My teacher answered "yes, well, actually no" but she never clarified so I was left not understanding.

The utility reason I ask this question is because I want to know at what point a pot of water can be said to have first reached 100C.

[OngBonga]

I guess the temperature of the molecule that boiled was 100 degrees, but the average temperature of the entire mass is marginally less. Or maybe something to do with not being at exactly sea level, thus lowering the boiling point of water fractionally below 100 degrees. I won't add more because it probably annoys mojo when I butt in! It would annoy me! I just can't help myself though...

[Poopadoop]

Well it's a chemistry question so probably he won't mind too much.

The water isn't going to uniformly heat. The part near the heating element is going to heat first and it will travel through the rest by convection/contact whatever heat travels by. I mean if a volcano goes off under the sea, part of the sea near the volcano can boil but obviously the whole ocean isn't 100C.

[Poopadoop]

Also if I'm not mistaken that's why the bubbles start at the bottom of a pot of boiling water, because that's where the heat's being applied.

Unless I completely misunderstood the question.