The Science Thread

Quote: Nareed

Well, flu is a name that applies to many kinds of respiratory infections. The infamous Spanish Flu pandemic was likely a type of pneumonia.

No, the Spanish Flu was the flu. Many deaths were caused by pneumonia that developed as a complication, but the Spanish Flu was H1N1 flu. All flus are variations of a specific category of RNA viruses.


Also, flu is absolutely transmitted airborne, through the mucus membranes. Cold and other respiratory illnesses are transmitted through surfaces, but flu is almost completely airborne.

And, whereas antibiotics are useless against the flu, they can be very effective against a secondary pneumonia.

Quote: Ayecarumba

There's a whole system known as homeopathic medicine that is based on exactly what you are getting at. Small bits of "nastiness" will stiimulate your body's natural systems to grow immune to the particular baddy, as well as others that produced similar symptoms. A lot of quackery, but perhaps some truth. The practice has been formalized for more than 200 years. I'd still refrain from wiping my eyes after touching chips in any casino though.

Homeopathy doesn't even have "small bits" in it. The preparations are diluted so there is no active molecules in the sugar pill they sell you. Pure quackery.

However, getting "general" yuck will help, as though future germs will be different, they may be at least similar to something you've seen before.

The last round of 'flu wasn't too virulent against certain members of the older generation as it was similar enough to a strain that had bumped around in the 60's. So some people's immune system was familar enough to shake it off quickly.

Quote: thecesspit

Homeopathy doesn't even have "small bits" in it. The preparations are diluted so there is no active molecules in the sugar pill they sell you. Pure quackery.

I'm not sure there's even any sugar in them sugar pills :)

Homeopathy is based on the belief that water retains a "memory" of substances previously dissolved in it. This begs the question that since a particular drop of water you get from the tap might have been literally anywhere in the world in previous times, and come in contact with any number of substances it dissolved, then how can you tell you're not taking the water's memory of, say, a neuro-toxin?

It is quakery.

Sorry if I digress but I was wondering if anyone could help figure out how one of our youth, a high schooler no less, burned herself using only ice and salt. The why it happened is wrapped up in the mystery of teenagers, but myself and the youth minister are a little curious as to how, any ideas?

Quote: Nareed

I'm not sure there's even any sugar in them sugar pills :)

Homeopathy is based on the belief that water retains a "memory" of substances previously dissolved in it. This begs the question that since a particular drop of water you get from the tap might have been literally anywhere in the world in previous times, and come in contact with any number of substances it dissolved, then how can you tell you're not taking the water's memory of, say, a neuro-toxin?

It is quakery.

The Quakers might be offended :)

The Homeopaths will tell you all about Succussion, where you have to strike the dilute ten times against an elastic surface to "activate" the energies of the substance. So this is why just taking a sample of just -any- water doesn't have the effect you describe.

Plus there's the "like cures like" and diagnosing symptoms, and using dilutes based on the effects of a chemical that cuases those symptoms.

It's all quackery, for sure, but like many true believers, they have a simple (broken) model to answer the obvious questions.

Quote: FrGamble

Sorry if I digress but I was wondering if anyone could help figure out how one of our youth, a high schooler no less, burned herself using only ice and salt. The why it happened is wrapped up in the mystery of teenagers, but myself and the youth minister are a little curious as to how, any ideas?

A freezer-burn from the cold?

Salt lowers the freezing point of water, so it'd be possible to use ice and salt to get water to below zero Centigrade (32 F). Stick your hand on it for a will and you can get frost bite (probably pretty mild initially).

Quote: thecesspit

The Quakers might be offended :)

So long as they keep the oatmeal coming... :P

Quote:

The Homeopaths will tell you all about Succussion,

But of course. And astrologers have their mumbo-jumbo, too. Any successful religion needs the double-talk or it fails to win many converts.

Quote: thecesspit

A freezer-burn from the cold?

Salt quickly breaks down ice, so that heat which was gradually removed to produce ice is quickly re-introduced back into the water.

Quote: FrGamble

Sorry if I digress but I was wondering if anyone could help figure out how one of our youth, a high schooler no less, burned herself using only ice and salt. The why it happened is wrapped up in the mystery of teenagers, but myself and the youth minister are a little curious as to how, any ideas?

I'd be suspicious. While it's true that salt water can reach <32* before freezing, I would think that 1) it's not an incredible amount of difference and 2) that simply adding salt wouldn't make the ice/water combo colder.

If you had pure water frozen at 32* and added salt, it would begin melting. That melted ice (water) would dissolve the salt making salt water. It may be possible that energy could be taken from this salt water to continue melting the ice that remains, which would bring the salt water lower than 32*, but I would bet several dollars the temp wouldn't fall below 30*, and I'd bet the farm it wouldn't drop to even 20*.

Living in NY, I've had skin against many different materials at a temp lower than 0*F without problem. Even putting bare ice on bare skin for several minutes as an injury treatment is only uncomfortable/painful, not noticably damaging.

I think you've been had, Father =/

Quote: FrGamble

Sorry if I digress but I was wondering if anyone could help figure out how one of our youth, a high schooler no less, burned herself using only ice and salt. The why it happened is wrapped up in the mystery of teenagers, but myself and the youth minister are a little curious as to how, any ideas?

This has me curious as well. Has anyone consulted Doc yet?

I'd guess she burned herself and then lied about it, put salt water on it.

Quote: Wizard

Quote: FrGamble

Sorry if I digress but I was wondering if anyone could help figure out how one of our youth, a high schooler no less, burned herself using only ice and salt. The why it happened is wrapped up in the mystery of teenagers, but myself and the youth minister are a little curious as to how, any ideas?

This has be (sic) curious as well. Has anyone consulted Doc yet?

I hadn't heard of this post at all until your P.M. suggested I look.

Quote: thecesspit

A freezer-burn from the cold?

Salt lowers the freezing point of water, so it'd be possible to use ice and salt to get water to below zero Centigrade (32 F). Stick your hand on it for a will and you can get frost bite (probably pretty mild initially).

That was my first guess, also. Freezer burn isn't really a burn, like with a hot iron, but it may feel similar and do similar damage. There is also the possibility that the chemical was not correctly identified. Rather than "salt" it could be something far from a neutral pH, giving either an alkali or acid "burn".

Quote: Garnabby

Salt quickly breaks down ice, so that heat which was gradually removed to produce ice is quickly re-introduced back into the water.

Uh..., no. I see no logical thought process that should make one think that something from which substantial heat has already been removed would suddenly give up a lot more heat when salt is added. The process of ice melting absorbs heat rather than giving it up.

Basically, the process is something like this: as thecesspit noted, adding salt reduces the freezing point of the ice/water. It tends to cause the ice to melt, though the ice might be even colder than the salt/ice melting point so that it stays frozen. If it does melt, the latent heat (discussed earlier in this thread), also called heat of fusion, must be added to the ice as it changes to a liquid. This energy typically comes from the water, resulting in salt water that is at a lower temperature than the original temperature of the ice. As thecesspit said, this colder water could lead to a freeze burn.

Quote: Mosca

I'd guess she burned herself and then lied about it, put salt water on it.

I have no info on such other possibilities, so I'll just say that if it is not a case of freezing or a chemical burn, we are left with speculation about what really happened.


Edit: Just one further comment -- if the young lady did burn herself in some other manner that she would prefer not to reveal, putting ice on the burned skin is not too bad a first aid technique. It tends to reduce the pain and to keep the damaged tissue from dehydrating. Of course, it is important not to introduce contaminants if the burn results in an open wound. (Please understand that my user ID of "Doc" does not imply medical training beyond what I got in a Boy Scout first aid class and a few odds and ends picked up along the way.)

It could be frostbite. Think about putting your hand in a foot of snow. Then, you add a bunch of salt around your hand. Though the snow melts, you now have your hand in water that's well below freezing. A 10% salt solution will dissolve that ice at 20F (-6C) which means the water (which conducts much better than snow) is at 20F. A 20% salt solution will melt snow at 2F (-16C). And water is a much better conductor than ice. But frostbite is not a burn. It's deadening of tissue as the blood no longer flows to the cold area.

Perhaps the trick is that Sodial hydroxide (a mean base) and Hydrochloric acid creates salt water:

NaOH + HCl -> NaCl + H2O.

Both items will burn badly but the result of mixing the two gets you salt water. I'm starting to remember my grade 12 Chemistry class.

Quote: boymimbo

It could be frostbite. Think about putting your hand in a foot of snow. Then, you add a bunch of salt around your hand. Though the snow melts, you now have your hand in water that's well below freezing. A 10% salt solution will dissolve that ice at 20F (-6C) which means the water (which conducts much better than snow) is at 20F. A 20% salt solution will melt snow at 2F (-16C). And water is a much better conductor than ice. But frostbite is not a burn. It's deadening of tissue as the blood no longer flows to the cold area.

Perhaps the trick is that Sodial hydroxide (a mean base) and Hydrochloric acid creates salt water:

NaOH + HCl -> NaCl + H2O.

Both items will burn badly but the result of mixing the two gets you salt water. I'm starting to remember my grade 12 Chemistry class.

I thinks that's too in depth, though. Ice+salt to me creates an image of an ice cube and salt shaker, maybe even a cooler full of ice. 2 minutes of a hand in that would be excruciating, on the upper limits of human tolerance, but I bet there would be no burn. Even constant contact on one specific part of you, say an ice cube placed on the skin that gets replaced while it melts, though tolerable, wouldn't cause a burn without a ridiculously long amount of time doing it. I've done it plenty of times for sprains and breaks and have been fine. Why would this teen have done anything like that?

Even a likely scenario, like playing outside in the snow, doesn't give an answer. I snowboard, worst day ever was about 5*F for 8 hours, face totally exposed - no issues. Steelhead fishing last year saw me in 20*F with a 30mph wind for 5 hours, with hands perpetually wet and gloves unusable. Couldn't feel my hands, but after 10 minutes of the car heater, they started working again and were undamaged. What in blazes could this teen have been doing to subject themselves to that type of exposure? It just doesn't jive, not one bit. After all, if it was cold weather related, you'd say "I got frostbite from playing outside" not "I got burned by ice". Come to think of it, you'd never say "I got burned by ice", you typically say exactly what happened.

I doubt this teen moonlights as a soap-maker-slash-metal-worker, so while your chemistry is solid, the logic does not compute =). Also, neither of those trades involve ice, in case they are a metal and soap maker. I smell hijinks, Father. Best start preparing penance ;)

The term is "endotermic process". To melt, the ice has to absorb energy from outside. So, putting such mixture on your hand will indeed cause a minor frostbite, not because the resulting water is that much colder (it's just a couple of degrees), but because of the speedy removal of energy from you skin by the process of thawing.

Remember, it's been already discussed in this thread, that it is not the contact with something cold by itself, that makes you cold, but loss of heat caused by it. The more rapidly you are losing heat, the worse off you are. In this case, the mixture against your skin isn't really very cold, but it causes your skin to lose heat very quickly, so that your body has no time to replace it, causing a frostbite.

And guys ... this really is possible. Don't try it, and don't tell your kids about it ... because they won't believe you, and run to the kitchen to prove you wrong :) The result is not a terribly bad burn, bad still pretty nasty.

Don't stick your hand in the homemade ice cream maker, eh?

If I go back to chemistry class, i now remember doing a science experiment to prove that when you mix an acid and a base, like sodium hydroxide and hydrochloric acid, the two mix to get salt water and there is also a large release of heat from the reaction. This is basic chemistry.

NaOH + HCl -> NaCl + H2O + heat.

If the kid splashed some of the acid on his skin before he mixed them together or during the mixing process, he would indeed get a nasty burn, even though the end result is salt water.

Alternatively, if the concentration of the acid and base are high enough, the exothermic reaction will heat the resulting salt water to a point where the salt water might get very hot. This was one of our calorimetry experiments. The higher the concentration of NaOH and HCL mixed together, the hotter the resulting hot water got.

Quote: boymimbo

If I go back to chemistry class

One difference here is that the heat being absorbed by the salted ice comes from a forced change of state, you are melting ice without using heat, thus heat is demanded from the environment. In the case of NaOH + HCl -> NaCl + H2O + heat, the energy is coming from a chemical reaction.

Quote: boymimbo

Perhaps the trick is that Sodial hydroxide (a mean base) and Hydrochloric acid creates salt water:

NaOH + HCl -> NaCl + H2O.

Both items will burn badly but the result of mixing the two gets you salt water. I'm starting to remember my grade 12 Chemistry class.

From what I recall of my chemistry calsses, HCl alone will burn you badly if it's at a ahigh enough concentration. I recall using it to dissolve metal in lab "experiments."

Assuming the student is telling the truth, then that leaves frostbite. As you point out, that's not a burn. but as Doc points out, the damage is similar to that casued by burns. No mystery there, both burns and frostibite destroy tissue. But frostbite, unlike burns, takes time. The girl would have had to leave her skin in contact with the very cold water for a rather long period.

Quote: Nareed

The girl would ahve had to lever her skin in contact with the very cold water for a rather long period.

Actually, just a few seconds is enough.

So weaselman is saying with a salt shaker and a couple of ice cubes at the Old Country Buffet it is possible for a young girl to create on her hand what looks like and feels like a burn. Science of course is about testing and verifying; anyone willing to try it? The mystery looks like it is solved and the truth was indeed told. What a good kid :)

Quote: FrGamble

So weaselman is saying with a salt shaker and a couple of ice cubes at the Old Country Buffet it is possible for a young girl to create on her hand what looks like and feels like a burn.

It depends.

Common household freezers operate at around -4 C. That's just cold enough to keep things frozen. Restaurant freezers operate in a range of -4 to -6 C. Industrial freezers, like at a meat-packing plant, run around -10 C.

Now, assuming ice at -5 C, you'd need a lot of ice to cause a frostbite burn. You can hold a regular ice cube in your hand for a long period without any damage at all. So think about an ice bucket or larger, and at least a pound of salt to melt it all.

Quote:

Science of course is about testing and verifying; anyone willing to try it?

We could do it at the next WoVCon and place bets on the outcome :)

Quote: Nareed

Now, assuming ice at -5 C, you'd need a lot of ice to cause a frostbite burn.

No, just one cube, pressed tightly against skin, generously sprinkled with salt is enough. And the temperature doesn't really matter. It could be exactly 0.
It's not the temperature that hurts you, it's the heat exchange.

Quote:

You can hold a regular ice cube in your hand for a long period without any damage at all.

Yes. The key is the salt causing it to melt quickly, sucking heat out of your skin.

Quote: Garnabby

Salt quickly breaks down ice, so that heat which was gradually removed to produce ice is quickly re-introduced back into the water.

Quote: Doc

Uh..., no. I see no logical thought process that should make one think that something from which substantial heat has already been removed would suddenly give up a lot more heat when salt is added. The process of ice melting absorbs heat rather than giving it up.

What are you talking about?

Seems like the some of the most-prolific authors on the internet message-boards least comprehend the obvious.

Quote: Wizard

Has anyone consulted Doc yet?

Oh really? Maybe "con-salted" would've been more-appropriate.

Quote: weaselman

... sucking heat out of your skin.

Poor choice of words.

Quote: weaselman

It's not the temperature that hurts you, it's the heat exchange.

But the bigger the temp difference, the more heat is exchanged.

I'm willing to take a regular hotel ice bucket full of ice, melt it with salt and stick my hand in it for three seconds. It won't be pleasant, but it won't give me frostbite either. How much would you bet agaisnt it? :)

Not really, but, "Knock yourself out."

There are two things happening here. There's an endothermic reaction where energy is absorbed to lower the freezing point of the water (the melting ice). When you add salt to a cup of ice water, the temperature goes down.

If your skin is in there, the transfer of energy is directly your skin to the ice cube via the salt, and the local temperature of the ice - salt solution (at your skin) is very much below freezing.

Frostbite is caused by the deadening of tissue. Tissue dies when no blood is flowing into it. When your nervous system experiences cold, the body's reaction is to reduce the flow of blood to that area (that's why you get the Seinfeld effect when you go swimming: I was in the pool!!!) in order to preserve your core temperature.

No, but try the following experiment:

Pour a tablespoon of salt onto a plate. Take an ice cube and place it in the salt. Place the ice cube, salt side down, on your skin. Wait.

Or save the time and hurt and watch this video..

Quote: Garnabby

Quote: Doc

Uh..., no. I see no logical thought process that should make one think that something from which substantial heat has already been removed would suddenly give up a lot more heat when salt is added. The process of ice melting absorbs heat rather than giving it up.

What are you talking about?

Seems like the some of the most-prolific authors on the internet message-boards least comprehend the obvious.

Perhaps we have some kind of miscommunication, or perhaps this is some kind of challenge to a pissing contest. If it's the latter, I'm not really interested, but if it is the former, then we should try to resolve the issue.

Here, I assume that the ice is not initially at such a low temperature that adding salt will not cause any melting; e.g., if it were initially at -40F, it would likely remain completely solid when the salt is added. Let's assume that the ice is initially at a temperature around 30F. Alternatively, we could assume that the ice is initially at 32F and is at equilibrium in a bath of water also at 32F.

It appears from your posts that you believe that adding salt to the ice in an attempt to melt it will result in heat being released into the water. Is that correct? If heat is released from the ice to the water as it melts, would you expect the water's temperature to tend to increase? If so, then we definitely disagree.

I expect the water (now with salt dissolved in it) to tend to drop in temperature as it transfers heat to the ice in the process of melting the ice. When the system reaches a new equilibrium point (with the salt now included in the system and dissolved in the water), the water (melted ice) and any remaining unmelted ice will be at a lower temperature than the original ice, unless there is some other source of energy, such as warm air or the hand of a teenaged girl.

May I ask how much heat you think you can get out of the ice and into the water by adding salt? How hot do you think you could get the water? Are you familiar with the second law of thermodynamics?

Quote: Nareed

But the bigger the temp difference, the more heat is exchanged.

True, but the difference is negligible. You can easily hold a piece of ice in your hand at 0F for a good while with only slight discomfort.
It is not the slow heat exchange due to the difference in temperature that causes damage in this case, but the rapid endotermic process of ice melting that does.

Quote:

I'm willing to take a regular hotel ice bucket full of ice, melt it with salt and stick my hand in it for three seconds. It won't be pleasant, but it won't give me frostbite either. How much would you bet agaisnt it? :)

That's not how you do it.
Try sprinkling a teaspoon of salt on your arm, and pressing a single cube of ice against it for like 20-30 seconds.
Or rather don't try it. You are not going to like it.

Quote: weaselman

That's not how you do it.

Indeed not. You gave the hustle away :P

Quote:

Try sprinkling a teaspoon of salt on your arm, and pressing a single cube of ice against it for like 20-30 seconds.
Or rather don't try it. You are not going to like it.

I wouldn't characterize 20 to 30 seconds as "a few." Rather that's a substantial portion of a minute.

As bizarre as it may sound, I think that weaselman and Nareed are both correct, if you allow a little third-party interpretation of their positions on this.

This is one of those interesting topics where thermodynamics and heat transfer come together. In most cases, thermodynamics is discussed in terms of systems that are in equilibrium states. We talk about changing from one equilibrium state to another, but we allow that the change might take place over a very long time so that there are no non-equilibrium states to concern us. In contrast, heat transfer is all about the rate at which the state is changing, and equilibrium states tend to be boring in a heat-transfer sense.

When the salt is added to the ice, it goes into solution in the water state. (There is always at least a film of liquid water on the surface of ice, even if it is at a lower temperature than where we would expect the water to be in solid form. Surface effects are another complicating issue.) How long it takes for the salt to dissolve is another issue, but let's assume that it does so very quickly. It has been pointed out by weaselman that the salt lowers the freezing point and necessitates the phase change (melting the ice). This phase change requires that a significant amount of heat be transferred to the ice (in spite of the claims by one poster.)

Now here is where weaselman and Nareed appear to disagree: weaselman claims that the phase change draws the heat rapidly out of the girl's skin, damaging her hand. Nareed says that the rate of heat transfer is due to the temperature difference -- for very rapid heat transfer from her hand, the ice would have to be a lot colder than her hand. Did I represent the differing views reasonably accurately? If so, then I repeat that I think that they are both correct. If the phase change occurs, there must be heat transferred to the ice, and for rapid heat transfer, there must be a sizable temperature difference (dependent also upon the thermal conductivity of the skin).

Here is the way I would describe the process: The melting of the ice does not occur instantaneously just because the salt has been added. There must be adequate time for heat to be transferred from a higher-temperature source. If everything in the vicinity is at the same temperature (32F ?) then the phase change forces the temperature to decrease so that there is heat transfer. Thus, the water/ice in the melting zone may drop to a significantly lower temperature, but not lower than the temperature at which the salt water would remain frozen. As weaselman points out, this can be quite cold.

Now if there is a teenage girl's hand in the immediate vicinity, that is a good source of heat to melt the ice. The heat will be transferred at the rate permitted by the thermal conductivities and the temperatures. I expect that the core of the girl's hand will remain rather warm, but the surface of the skin will quickly drop to a temperature essentially the same as the melting ice, and it will be damaged rather quickly. The skin temperature must drop very nearly to the ice temperature because the thermal conductivity of her hand is not sufficient to keep transferring heat to the surface quickly enough to keep the skin warm while it is rapidly melting the ice. The temperature-difference limitation on the rate of heat transfer becomes a difference between the core of the hand (blood in the vessels?) and the surface of the skin, not one of a difference between the skin temperature and the ice temperature.

I don't care to conduct such experiments on my own skin.

Quote: Doc

Perhaps we have some kind of miscommunication, or perhaps this is some kind of challenge to a pissing contest. If it's the latter, I'm not really interested, but if it is the former, then we should try to resolve the issue.

How diplomatic. Now, according to yourself, i've also made it a possible "pissing contest"/challenge to boot. How stupid do you think we are?

Quote: Doc

It appears from your posts that you believe that adding salt to the ice in an attempt to melt it will result in heat being released into the water.

Where/how does my brief, single specific post about this topic say/imply that? Something, i'm sure you would've already noted in-full were any of that the case. How stupid do you think i am?

Quote: Garnabby

Quote: Doc

It appears from your posts that you believe that adding salt to the ice in an attempt to melt it will result in heat being released into the water.

Where/how does my brief, single specific post about this topic say/imply that? Something, i'm sure you would've already noted in-full were any of that the case.

Well, actually, your "single specific post about this topic" has been several posts. My comment that it appears you believe that melting ice will result in heat being released into the water is derived from this post of yours:

Quote: Garnabby

Salt quickly breaks down ice, so that heat which was gradually removed to produce ice is quickly re-introduced back into the water.

So are we dealing with some kind of semantics where "heat being released into the water" is markedly different from "heat ... is quickly re-introduced back into the water"? And, yes, as a matter of fact I did point out that specific comment of yours earlier.

Quote: Garnabby

How stupid do you think i am?

At this point, I think I am going to have to ask for input from other members. Have I been misinterpreting what Garnabby has been saying? While I am not inclined to call any member here "stupid", does it seem to anyone else that this poster has posted silliness in a "science" thread in an attempt to start an argument? Does he seem to be acting like a troll? Is JL alive and well? What am I missing here?

I don't think you're missing anything Doc. I appreciate your patience and input.

There can be energy transfer without temperature change. In fact, that is what happens at a change of state of material. Salt used to melt the ice would make sense. The temperature of the ice doesn't change, but the molecules will draw heat rapidly from their surroundings, like your skin. The key here seems to be to make the skin in contact with the ice and salt at the point that state change occurs (hence the procedure... arm, salt then ice).

Quote: Doc

Well, actually, your "single specific post about this topic" has been several posts.

No, there's only one reply of mine to "this topic", FrGamble's question about salt and ice causing a "burn". My other replies were re-replies in my defence against your misreading(?) that one reply.

Quote: Doc

My comment that it appears you believe that melting ice will result in heat being released into the water is derived from this post of yours.

Again, how do you conclude that? Where/how does my statement say/imply the above?

Quote: Doc

And, yes, as a matter of fact I did point out that specific comment of yours earlier.

It was a statement, not a commentary. But you still have not responded about where that statement of mine says/implies the previous quote.

Quote: Doc

At this point, I think I am going to have to ask for input from other members

Okay, but i hope to see more-meaningful input than the following.

Quote: Ayecarumba

I don't think you're missing anything Doc. I appreciate your patience and input.

That doesn't address the conflict per se.

Quote: Doc

While I am not inclined to call any member here "stupid", does it seem to anyone else that this poster has posted silliness in a "science" thread in an attempt to start an argument? Does he seem to be acting like a troll? Is JL alive and well? What am I missing here?

Then skip supercilious stuff beginning with like, "Uh..., no." And never refer to such a simple, obviously-honest, straightforward statement in the above manner and way. Ridiculous. Anyway, why is it that you seem (to me) to be the only one here who's "inflammed" by that so-called silliness; and has welcomed others into this?

Quote: Face

OK, let's get gross with this. I subscribed to a lifestyle later made famous by Carlin in one of his skits, namely, if you subject yourself to enough nastiness you become impervious to all. I almost never wash my hands (except lately due to having a child), I don't wash fruits/veggies, I eat food well past it's expiration, let mayo sit out, whatever, eat raw egg products, eat undercooked meats including chicken, drink creek and lake water... and I (now) NEVER get sick. I mean, I get a sinus infection like clockwork everytime the seasons change, but I never get a cold, never get the flu, never get a stomach bug, nothing.

The last time I remember having a cold was about 7 years ago. The last time I got the flu was nearly 20 years ago. The last time I had stomach issues was also nearly 20 years ago, and it always happened after visiting a certain body of water (one I used to drink, and one I still drink to this day, but now, with no consequence)

Is there something to this, or is it just luck? Other than the "shame" of being gross, could it be better healthwise to be somewhat dirty as opposed to overly clean?

I'm the same way. Don't many preventions work by giving you small doses to fight off? We can't get sick, we're already sick, except our body is tired of showing it. It gave up. It's tired of warning us about nothing that is harmful. Did I regain the "Vague" title?

FrG, I enjoyed the reference to the Old Country Buffet. I have eaten at the one on Route 40 many times, especially on ribs night.

To change channels a bit, any chance you could get more details out of in her in the confessional? Oh wait, what is said is supposed to be confidential. Dang!

Quote: Doc

At this point, I think I am going to have to ask for input from other members.

I am behind you 100% on this Doc. It pains me to see the treatment Garnabby is giving you, which is rude and disrespectful. Despite you not accepting the title, I still say you are the "science guy" of the site.

Quote: Wizard

I am behind you 100% on this Doc. It pains me to see the treatment Garnabby is giving you, which is rude and disrespectful. Despite you not accepting the title, I still say you are the "science guy" of the site.

Thanks for the support. I still think much of my "science" may be out of date, much as I am myself, so I still decline the title. I think I retain a fair understanding of the basics as they were taught back in the old days.

This gives me the opportunity to compliment some other members. I have noticed very high quality of science understanding by many others on this forum, some of which understanding very likely goes beyond my own -- it's not just the math nerds here! If I could keep all the names straight in my head, I should compliment several people on their posts, but I will take time to mention only one here, because he has made several good posts in this thread, and that is weaselman.

There has been at least one topic on which weaselman and I have disagreed. I finally figured out that it is just a matter of how each of us uses a particular term, so I want to clarify that point here -- language, not a disagreement about science, I think.

My perspective: I view "weight" to be the force which a mass experiences due to the local gravitational field; weight may be calculated by multiplying mass times the acceleration of gravity. This force may or may not be counterbalanced. If not, then the body will accelerate, perhaps in totally free fall. Even in that case, the body has the same weight, provided its mass and the gravitational field have not changed. If the gravitational force on the mass is completely counterbalanced by an upward force, then there will be no acceleration (Newton's first law).

weaselman's perspective (I think): Weight is the force that a mass imposes on its support structure when the mass is acted upon by a gravitational field and there is no acceleration. If the object is in free fall, it has no weight.

In a different thread, we came danged close to getting into an argument over this before I realized that we just use the term "weight" to describe different forces. If there were a problem with gravitational attraction, masses, and maybe even some acceleration, I suspect that weaselman and I would calculate the same answer, provided we were careful not to use the term "weight" along the way and get back into a dispute about language rather than science. Conclusion: weaselman, I think you have your act together on this stuff, even if I disagree about how to use this one term.

At the risk of getting off topic, I recall struggling with the difference between weight and mass way back when. I think what helped me is I went to a science museum and there were various scales for how much you would weigh on various planets. By the same "scale" logic, if you put a scale in a fast elevator, and stood on it, it would register more going up and less going down. Also consider the G Force One plane, where you basically are in freefall. Their website says, The ZERO-G Experience is a once-in-a-lifetime opportunity to experience true weightlessness. So, while admitting I'm not at your level in terms of science, weaselman's argument sounds like it holds more water, to me at least.

Thanks for the kind words Doc. Means a lot coming from you.

FWIW, here is the definition of weight from NIST (which they in turn copied from ISO 8000-4):

Quote: ISO 8000-4

the weight of a body in a particular reference frame is defined as the force that gives the body an acceleration equal to the local acceleration of free fall in that reference frame.

This is another (awfully complicated :)) way to say the same thing I was saying - weight is basically the force, measured by the scale (provided, that you use a reference frame co-moving with the scale, and the mass).

I actually think, that my definition (force exerted on the support) is even better (if for no other reason, because it does not depend on the "acceleration of free fall" - another term, that needs to be defined for completeness, and also, I don't like using a concept of reference frames when talking about forces, it complicates things way too much unnecessarily), but functionally it does define the same force.

Note: This reply to the Wizard was composed before I read weaselman's post immediatly above.


Yes, "zero-G" and "weightlessness" are terms that are very commonly bandied about when discussing freefall. There are perspectives (such as weaselman's, I suppose) that support these usages, and other perspectives that point out fallacies or inconsistencies. For examples:

(1) What does "zero-G" mean? Does it suggest that there is zero gravity? If so, why do you fall? What would you think of a car that claimed "zero-G" acceleration performance? Wouldn't you expect it to sit still at the starting line? Isn't that quite different from what they call a "zero-G" experience falling from the top of a tower? (From my perspective, when you are in free fall, you are experiencing exactly 1 g, not zero-G, no matter how commonly that term is used.)

(2) What does "weightlessness" mean? Does it mean that there is no weight pulling you down? If so, why do you fall? If you don't realize that you are falling faster and faster while you seem to be floating in that modified 727, then they have pulled a carney stunt on you. (Actually, they probably start that experience while on an upward path so that your downward acceleration changes you from an upward velocity component to a moment of zero vertical velocity and then a period of falling faster and faster.)

So how would I describe a "zero-G" situation? Well, I'm having one right now sitting in front of my computer. Gravity is pulling me down with a force equal to my weight (my use of the term). That force is transmitted to my chair by contact, while my chair is pushing back up on my butt with an equal force (Newton's third law). Since the force the chair imposes on me is equal in magnitude and opposite in direction to my weight, I am not accelerating at all (Newton's first law), so I am experiencing zero G (or g) of acceleration. I am in a 1 g gravitational field, but the force from the chair counteracts that. Zero g is the state in which we spend most of our lives. However, the term "zero-G" has a nice ring to it, and the experience of free fall provides an eerie sensation, so the two have been combined in common parlance, as well as in the $4,950/person tour you provided the link for.

Here's a little thought experiment (which isn't likely to resolve any disagreement). Suppose you have a rock with a mass of one pound. We normally describe this as 1 lbm. If this rock were sitting stationary on a table in a standard gravitational field, weaselman and I would agree that it has a weight of one pound force or 1 lbf. If you were to drop that rock over the railing at the top of the Stratosphere tower, it would plummet. My perspective is that it would still weigh 1 lbf and would be experiencing 1 g acceleration (neglecting the affect of air resistance). I think weaselman would say that it would have zero weight during the fall, and some people would say that the rock was having a zero g experience, though I don't know whether weaselman would use that term or not.

Now suppose that we had some means of providing a small upward vertical force on the rock during its fall -- perhaps an insufficient parachute, or a canary tied in a harness. I could also suggest the ordinary drag of air resistance, but for this thought experiment I want to consider providing a constant upward force equal to 0.25 lbf. That is not enough to support the rock or to keep it from accelerating downward, but it would reduce its downward acceleration from 1 g to 0.75 g (in my perspective). So the question becomes: What is the weight of the rock as it is falling, while the canary is ernestly but unsuccessfully attempting to keep it up?

In my opinion, the rock weighs 1 lbf all of the time in this experiment -- it never experiences weightlessness and the canary didn't change the weight of the rock. What is your opinion of the rock's weight in this situation? Answers are invited from all.

Quote: Doc

(1) What does "zero-G" mean? Does it suggest that there is zero gravity? If so, why do you fall? What would you think of a car that claimed "zero-G" acceleration performance? Wouldn't you expect it to sit still at the starting line? Isn't that quite different from what they call a "zero-G" experience falling from the top of a tower? (From my perspective, when you are in free fall, you are experiencing exactly 1 g, not zero-G, no matter how commonly that term is used.

I am not familiar with "zero-G" as a scientific term. A quick google search reveals "abbreviation: zero gravity", which, I agree with you does not make any sense. There is no such place in the whole Universe where there would be "zero gravity".
What I think is usually meant by zero-G is, roughly, inertial motion. If you hold a stone in hand, and let it go, it should stay where it is relative to you. This is a test for "zero-G" state.

Quote:

(2) What does "weightlessness" mean? Does it mean that there is no weight pulling you down?

It actually means that there is no force pushing you up :)

Quote:

If so, why do you fall? If you don't realize that you are falling faster and faster while you seem to be floating in that modified 727, then they have pulled a carney stunt on you.

This stunt is the corner stone of the Relativity :)

Quote:

I think weaselman would say that it would have zero weight during the fall, and some people would say that the rock was having a zero g experience, though I don't know whether weaselman would use that term or not.

Yeah ... I, probably would not :) I am in general not a big fan of using several different terms to describe the same entity.
"zero weight" (weightlessness) is descriptive enough, no need to invoke another term.

I have a similar problem with your definition of weight BTW - it seems indistinguishable from gravitational force.

Quote:

I want to consider providing a constant upward force equal to 0.25 lbf. ...
What is the weight of the rock as it is falling, while the canary is ernestly but unsuccessfully attempting to keep it up?

You said it - it's 0.25 lbf :)

Quote: Wizard

At the risk of getting off topic, I recall struggling with the difference between weight and mass way back when.

I have a very different concept of Mass but I wish people were as nice and thoughtful as Doc and Weaselman over on the religious threads.

Quote: FrGamble

I have a very different concept of Mass but I wish people were as nice and thoughtful as Doc and Weaselman over on the religious threads.

Yeah, no one's ever been burned at the stake, or marched into a gas chamber, because his definition of mass differed from that of the majority. Also no one tries to force others into accepting their moral code because they think they're definition of weight is the only one acceptable.

Quote: Doc

Yes, "zero-G" and "weightlessness" are terms that are very commonly bandied about when discussing freefall.

Speaking of free fall, I've two questions that have been nagging me:

1) I'll ask it if you've read Larry Niven's "The Integral Trees."

2) Suppose the Earth was a perfect sphere with its mass evenly distributed. Now suppose it has a hollow center, say 10 meters in diameter. If you were at the exact center, would you experience weight? Wouldn't you be pulled equally in all directions?

Thanks.

Quote: weaselman

I have a similar problem with your definition of weight BTW - it seems indistinguishable from gravitational force.

Yep, from my perspective, my weight is precisely the force that gravity imposes on my mass – nothing to distinguish. It appears that we understand each other, which seems like a good basis on which to agree to disagree on the use of the term. However, I sometimes find it difficult to leave well enough alone. :-)

Quote: weaselman

Quote: ISO 8000-4

the weight of a body in a particular reference frame is defined as the force that gives the body an acceleration equal to the local acceleration of free fall in that reference frame.

I think I agree with this definition but disagree with your interpretation, so let's try another one:

Choose a frame of reference fixed with respect to the surface of the earth, and consider only local problems. In particular, consider the example the Wizard mentioned of travel in an elevator.

Suppose the teenage girl mentioned by FrGamble a couple of pages earlier in this thread has a mass of 100 lbm. Suppose that she owns an extremely accurate bathroom scale. (Yes, I know.) She places the scale on the floor of the Stratosphere elevator, steps on, and waits until the elevator is ready to start. Gravity is imposing a downward force of 100 lbf on the girl, a force that I call her weight. The scale, of course, reads 100 lbf. I interpret this to mean that the scale is pushing upward on her feet with a force of 100 lbf, and I think you interpret that force as being her weight. Numerically, we agree on her 100 lbf weight. Now you know that from my perspective she is going to weigh 100 lbf the entire time, so let's consider some of the situations that might get in the way of everyone agreeing.

The elevator operator hits the button, they start the trip toward the top, and the young lady glances at the display on the scale. It reads 120 lbf. I suspect you are going to say that she then weighs 120 lbf, right? At what rate are she, the elevator, and all of the other occupants accelerating? By my perspective, they are accelerating at 0.2 g upward. Do we agree?

Now suppose the Stratosphere had a super elevator and that the young lady is impressively strong. As the super elevator zooms them upward, she looks down at the scale and sees the display reading 200 lbf. What does she now weigh? (200 lbf from your perspective, right?) At what rate are they accelerating? By my view, they are accelerating at 1 g upward. Do we agree?

What force is the scale imposing on the girl's feet? I think we would both agree on 200 lbf upward as the answer to this question, right? Is gravity still imposing a force on her body? How much? I think it is still 100 lbf downward, do we agree on that? If so, what is the net of all forces acting on her body? I think there is a 200 lbf upward force delivered by the scale to her feet and a 100 lbf downward force delivered by the gravitational field for a net force of 100 lbf upward. Do we agree?

OK, now look at the ISO definition. Her weight is defined as the force that gives her body an acceleration equal to the local acceleration in free fall; i.e., an acceleration of 1 g. We have changed the direction from fall to climb, but I believe that there is a net upward force of 100 lbf giving her an acceleration equal to 1 g upward. By the definition, doesn't that mean that her weight is 100 lbf rather than the 200 lbf that the scale reads?

Responses to these questions are invited from all, just as the invitation still holds to all regarding the weight of the 1 lbm rock that the canary can't lift.