Wikipedia:Reference desk/Archives/Science/2007 December 18

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December 18[edit]

What happens to weight and pressure at centre of Earth?[edit]

This one has had me stumped for years. Imagine being in a very sturdy air-conditioned spherical pod right at the centre of the Earth. Now, you have equal amounts of mass pulling on you from every side, so the gravitational attraction should equal out, and you should be weightless, just floating around in the pod. Could that be right? But if weightlessness rules at the Earth's centre, then how does that affect the enormous pressure that's supposed to be down there. If you are floating around weightless, then there can't be matter pressing in on you, and so there should be no pressure. But that doesn't make sense either. That would mean that you really COULD have a hollow Earth with habitable regions at the middle! And how does this weightlessness tie in with Einstein's General Theory of Relativity, which says that mass curves space, which causes the gravity effect? Does that mean all that mass unwinds the curvature at the centre of massive objects like the Earth. Myles325a (talk) 00:28, 18 December 2007 (UTC)

There is weightlessness, and there is pressure on the outside of the pod due to the weight elsewhere, this is not a contradiction.--Patrick (talk) 00:48, 18 December 2007 (UTC)
I agree with Patrick - you are weightless - but the planet all around you is still being pulled inwards - so the pressure is spectacular. In a previous question, we were asked to explain what would happen if there were some kind of tunnel cut through the center of the earth and lined with some kind of indistructable, heat-proof material. One of the conclusions is that the air pressure at the center of the earth would be enough to liquify the air!
For the second part - imagine the old diagram (which if you watch any science programs at all, you've seen!) of a rubber sheet with a bowling ball rolling around on it - the dimple made by the ball has a flat bottom - corresponding to the lack of gravitation at the very center of the earth. You'll also have seen those pointy, almost conical space-distortion diagrams where there is a black hole...because they have zero size and infinite density. SteveBaker (talk) 01:00, 18 December 2007 (UTC)
See also previous answers to this question here and here. ›mysid () 13:48, 18 December 2007 (UTC)
The rubber sheet is a model of Newtonian gravity, not general relativity. See Gravity well. -- BenRG (talk) 23:54, 18 December 2007 (UTC)
You experience weightlessness but it does not mean there's no gravity, or more precisly force. You are at equillibrium becase gravitational forces pulling on you from every direction are cancelling each other out. Since there are still forces, you can imagine there can still be presurre. General Theory of Relativity is not effected since mass did not change. Your weight changes due to gravity, mass does not. Force (weight) = M (mass) * Accellaration (gravity) NYCDA (talk) 20:41, 18 December 2007 (UTC)

values for ATP hydrolysis - enthalpy and entropy[edit]

I am looking for the thermodynamic free energy values of ATP hydrolysis to ADP and Pi as a function of the temperature or alternatively the values of the enthalpy and entropy. Thanks, Ron Milo Harvard University —Preceding unsigned comment added by Ron milo (talkcontribs) 01:01, 18 December 2007 (UTC)

Walk over to Widener Library and look up the answer yourself in any biochemistry textbook. Delmlsfan (talk) 02:29, 18 December 2007 (UTC)
Are you looking for standard conditions of physiological conditions? If the latter there is a range depending on the concentrations of ADP, ATP and Pi in the cell at any given time. Have you looked at ATP yet, and it's talk page too? David D. (Talk) 02:36, 18 December 2007 (UTC)
After consulting several textbooks and professors I could not find the values (notice that the text books usually have the free energy (deltaG) at only one temperature). I am looking for either standard conditions or physiological conditions whatever I can find which is reliable. Yes, I did check the wikipedia page. —Preceding unsigned comment added by Ron milo (talkcontribs)
Well standard conditions by definitions will be 25 degrees celcius. Why do you consider the text book values for standard conditions unreliable? (at least that seems to be your implication). What was wrong with the values in the links above. As i mentioned above, if you need a physiological value you will have to deal with a range, not an exact figure, since the physiological conditions will vary in an organism. Try this link that shows two graphs that represent how the free energy of hydrolysis changes with respect to pH and Mg2+ concentrations respectively. Clearly many other factors will change it too. David D. (Talk) 03:45, 18 December 2007 (UTC)

I am looking for the enthalpy and entropy, so 25 deg could be fine or alternatively deltaG as a function of temperature (which then is not standard, you are right). I am aware of the effect of the physiological conditions, Mg, and pH. The links and textbooks talk about deltaG only (not deltaH, deltaS) and at one temperature only. Will be really happy if you find any of these values. Thanks. By the way, you can see many useful biological numbers at BioNumbers - —Preceding unsigned comment added by Ron milo (talkcontribs) 14:48, 18 December 2007 (UTC)

Good link. OK sorry, you really do what enthalpy and entropy, I just assumed you were misusing those terms. My apologies. You must have a high regard for wikipedia to come here for such answers. Off the top of my head I have no idea what those values are. I assume there is a standard reference book with all these values for biological reactions but i don't know which one. My focus is more developmental and genetics rather than biochem. I suggest you ask GraybeardBiochemist (talk · contribs) he makes excellent edits on the encylopedia and is clearly very knowledgeable. My bet is he'll know a reference book that has these values. David D. (Talk) 15:16, 18 December 2007 (UTC)

2 cars crash head on[edit]

I'm sure this had been asked before, but I couldn't find it. This is a long running fued on alot of sites:

Two identical cars travel at identical speeds in opposide direction crash head on resulting in both coming to a stop. All energy is lost via noise/phsyical deformation.

For a driver, the impact would be identical to driving into a solid stationary wall at either:
-The same speed as was in the head on collision.
-Double the speed as per head on collision (ie combining the speed of both vehicles)

I contend the same speed, as in both cases the car goes from the speed to zero and dissipates the same amount of energy, and since the cars are identical, both will dissipate equal and opposite such that the head on collision is effectively as if each ran into a solid wall anyway.

Furthermore I also contend that if one vechile is stronger than the other, the stronger vechicle driver should have the creedence to choose to hit another car head on rather than hit a stationary wall, even if the other car is coming as fast as he is in the opposite direction.--Dacium (talk) 04:11, 18 December 2007 (UTC)

This was asked a few months ago, but I don't feel like hunting it down. The "same speed" scenario is correct. Since the cars are identical, they will symmetrically come to a stop. Therefore, they will each cover exactly half the distance between them, so you can basically just draw yourself in imaginary wall at that meeting point, and neither car will pass through this wall. Then just satisfy yourself that this is the same as each car hitting a very non-imaginary, immovable wall. Someguy1221 (talk) 04:56, 18 December 2007 (UTC)
You could also reason out that going at double speed into a wall would actually involve twice as much energy as the two colliding cars. Indeed, you could think of it entirely in terms of kinetic energy. If each car in the original scenario has energy E, then the total system must dissipate 2E between two cars; each car dissipates E. In the one car, same speed into a wall, the car has to dissipate E as well (you can just say the wall is so heavy and such a good insulator, that it won't help dissipate any energy). For the one car, double speed scenario, it has to dissipate 4E all by itself. Someguy1221 (talk) 04:57, 18 December 2007 (UTC)
To further clarify this, Someguy1221's first answer is wrong, and his second answer is correct. The impact felt by a passenger in either car will seem to be double if his car hits the other coming in an opposite direction from what it would be like if he hit a stationary object with just his one car involved.
The physics behind this is very simple - it involves the kinetic energy of the two cars. When an object that is moving comes into contact with a stationary object (such as the wall), some of the energy that is involved with the moving object (which is called kinetic energy) is transfered from the moving object to the stationary object. Likewise, the stationary object also has a kind of energy, which is a kind of potential energy called rest mass energy. So a large solid brick wall has more potential rest mass energy stored in it than say a wall made of tissue paper. When a car hits the brick wall, it will encounter a lot more potential energy than if it had hit a wall of tissue paper.
So what we have when a car hits a brick wall is a certain amount of kinetic energy (represented by the car's speed and mass) that comes into contact with a certain amount of potential energy (represented by the wall's mass), resulting in a transfer of energy between the two objects. If the car's kinetic energy is a lot greater than the wall's potential energy, then the wall will fall apart and the car will continue on, although slowed down a bit and the worse for wear. But if the brick wall's potential energy is far greater than the car's kinetic energy, then the car will smash into the wall, perhaps causing some damage to it as the energy is transfered between the car and the wall, but the wall will stand. It all is about how much mass is involved in both the wall and the car, as well as the speed of the car. If the car is going slow, it will have less kinetic energy than if it was going fast. Speed and mass is the key here.
Now, when two cars traveling in opposite directions hit, they both have kinetic energy that is released. This energy would be roughly twice as much as if just one car hit a brick wall because the speed of the impact would be twice as large. To compare this with another example, think of baseball. There is a kind of baseball game that is played by young kids called Tee Ball in which the baseball is set on top of a post about shoulder high to the kid at home plate. The ball is stationary, thus making it easier for the little kid to hit it with the bat. Now, if you had a professional baseball player from the Major Leagues step up to bat and hit the stationary baseball on top of the Tee, it would probably be hit for quite a long distance - let's say 250 yards. However, if the same baseball was thrown at 90 miles per hour by a professional pitcher to the same batter, who used the same force to hit it, and all other things being equal, the ball would be smashed for a much longer distance - say 350 yards - than if it had just remained stationary. The reason for this is because the ball was traveling at a high velocity towards the bat when the two objects (bat and ball) impacted. The resulting transfer of kinetic energy between the bat and ball would be much greater than if the ball had remained stationary on the Tee in the first example. This extra kinetic energy transfer would give the ball much more velocity away from the bat, making it travel a lot farther.
So it would be with the two cars colliding - think of them as the bat and the ball that was pitched. The solitary car hitting a wall would be like a bat hitting the ball sitting stationary on a Tee. Thus you can visualize how the transfer of kinetic energy works, and thus visualize why it would be much more dramatic to be in a head-on collision than a collision with a stationary object. -- Saukkomies 14:16, 18 December 2007 (UTC)
I found it very interesting to notice that my first answer was wrong, and the second one correct, when they're actually the same...Someguy1221 (talk) 20:34, 18 December 2007 (UTC)
Not so. The problem with the bat-and-ball analogy is that the bat and ball are not even remotely the same mass, nor do they have the same forces applied (the ball is freely moving, the bat being continuously acted on by the batter). A correct baseball analogy is two pitching machines throwing at each other -- there will be no (idealized) difference in a two-ball collision than in a ball-plus-wall collision. Someguy's note about the imaginary wall is quite correct, and Dacium's note about the larger car preferring collision is also correct. — Lomn 14:32, 18 December 2007 (UTC)
The last time this question was asked was August 15th: Wikipedia:Reference_desk/Archives/Miscellaneous/2007_August_15#Head-on_collision_with_two_cars.
My answer remains as then:
Q: Suppose two identical cars with 2 clone drivers collided with each other head-on, each traveling at a speed of 100 km/h. Would the impact that the two driver feel be equal to the impact of them driving into a solid wall at 200 km/h? This is what I intuitively think, but several driving instructors told me that the impact would be like as if driving into a solid wall at 400 km/h, citing something to do with physics.
It's most definitely like hitting a wall at 100kph. There is a simple answer and a MUCH more complicated answer - and your driving instructors are picking the complicated one and failing to understand the full consequences of that decision. I'll try to explain - but it's gets horribly complicated very fast!
  • SIMPLE ANSWER: The total energy that has to be dispersed by crumpling metal is twice as high when two cars collide (if both are travelling at 100kph) than if one car hits a totally immobile brick wall at 100kph - but the crumple distance is also doubled and so is the amount of bent metal at the end (which is where all that kinetic energy went) - so the accelleration is the same when two cars collide at 100km/h versus one car hitting a wall at 100km/h. So no - driving into another car with both going at 100km/h would be the same as driving into a wall at 100km/h. (In fact, no wall is going to perfectly fail to absorb any energy - so you'd probably be fractionally better off hitting the wall in the real world).
  • UGLY RELATIVE MOTION ANSWER: The relative motion argument is another perfectly valid way to look at it - but you have to be utterly consistant about that. So from the point of view of a frame of reference that's moving at a uniform speed of 100kph towards you: You are initially rushing towards that frame of reference at 200kph and the other car is stationary (compared to that frame of reference) - then you collide - but then both cars continue on at 100kph - the frame of reference didn't stop moving. So your speed (in that frame or reference) went from 200kph to 100kph - so you lost 100kph and it's no worse than driving into a brick wall at 100kph in a stationary frame of reference.
  • DRIVING INSTRUCTOR ANSWER (which is bogus): I suspect these guys read that kinetic energy is mass times the SQUARE of the velocity (that's true - if you hit a brick wall at twice the speed - you'll take four times the amount of damage - so drive slowly!). So they reason that the kinetic energy at double the approach speed is four times higher. But then they make the mistake of picking the other car's frame of reference, instead of having two cars, both with energy (E) given by E=(Mass x 100kph x 100kph) - they assumed that this was the same thing as one car moving at twice the speed (Mass x 200 x 200)...which is 4E. But that's only allowed if you take the 'UGLY RELATIVE MOTION ANSWER' - and in that case, the car doesn't lose all of it's kinetic energy - it only loses enough to drop its speed from 200kph to 100kph (3E) - and (critically) in this rather strange frame of reference, the other car GAINED kinetic energy because it starts off stationary and winds up moving backwards at 100kph, gaining -E in the process. The resulting energy (2E) is then shared between the two cars - so (as if by magic), each car has to dissipate exactly 1E of damage...just the same as it was if you pick a less mind-bending stationary frame of reference.
SteveBaker (talk) 16:13, 18 December 2007 (UTC)
We also answered this on May 18th: Wikipedia:Reference_desk/Archives/Science/2007_May_18#question_about_multinertia. Comfortingly, we came to the same conclusion! SteveBaker (talk) 16:25, 18 December 2007 (UTC)

There is just one more point to make, which is that one reason the scenario produces debate is that it's unrealistic. When cars crash into fixed obstacles in real life, the normal behavior is that they smash into the obstacle; it at least suffers surface damage or gets pushed out of position, and if it's something like an ordinary building wall, then the car breaks right through it. Or if the object is really strong, like a load-bearing wall struck endwise, then it may be narrow and the car may wrap around it. Those kinds of collision, while very serious at any significant speed, are less damaging to the car than if it hits a truly invulnerable stationary object as supposed in the question. --Anonymous, 17:27 UTC, December 18, 2007.

Yep - exactly. This is why "in real life" you are actually better off smacking into a brick wall than into another car going at the same speed in the opposite direction (aside from the obvious one of not causing the other driver to have an accident too!). However, once you start getting into collisions with objects of various shapes, the arguments get vastly too complex and too dependent on how your car is constructed. But for an idealised indestructable, unbending, immobile wall, the effect is the same as smashing into another car coming at you in the opposite direction at the same speed as you. SteveBaker (talk) 22:15, 18 December 2007 (UTC)
See, the problem with what I was contributing was that I did not take into account the absorption factor of the vehicles' front ends. I see the point being made about how an automobile with a lot of absorbing material up front is different than that of a baseball, which has little of that sort of thing. However, I do disagree with the person who said that the baseball and bat is a bad analogy due to how the ball is freely moving and the bat being continuously acted on by the batter. For one thing, there is only a fraction of a second's contact between the bat and ball, and any amount of energy that is transfered from the bat to the ball will take place within that time - in other words, the bat does not hit the ball and then continue to propel it forward on its path. Also, if we're comparing this to the automobiles, they too are being (theoretically) continuously acted upon by the engine and drive shaft of the car to propel them forward against the obstacle they're hitting. But this is missing the point that I was trying to make: if you eliminate all of the absorption from the front end of the automobiles, the bat and ball analogy works. The real reason that a front end collision would not be more severe (and from my personal experience this is not the case in real life, by the way) is not due to the physics of kinetic and potential energy, but due to the engineering of the vehicles that reduces the shock felt by the driver inside the automobile as energy is transfered away from the passenger area through the engine compartment and front end of the car as it collapses on impact. If the passenger was sitting on the front of the bumper of the car upon impact instead of inside on the driver's seat, the impact of a head on collision with another car would be twice as strong as if it was against an immobile object. -- Saukkomies 10:12, 19 December 2007 (UTC)
Sorry - no. I have to completely disagree with you there. So long as you sit in the same place in the car in both cases - it doesn't matter whether you smack into a totally unyielding object - or another car coming in the opposite direction at the same speed. That's true even if both cars are made out of something that doesn't crumple well. I'm not going to go over it again - re-read my first explanation in this thread. SteveBaker (talk) 20:01, 19 December 2007 (UTC)
If you work out the law of Conservation of Energy, you'd see it's the same as hitting a stationary wall. You can do this simple experiment. Get 3 identical balls. Roll 1 ball at the wall at a right angle at a fixed speed and observe the speed of the ball as it rolls back at you. Now roll 2 balls at each other at the same speed used earlier, you will observe the speed of the 2 balls after it collides and rolls away from each other is the same as the the speed of the ball 1 when it rolls back at you after it hit the wall. Using a 3rd stationary ball. Roll balls 1 and 2 towards it from opposite direction at exactly the same speed again. You will observe, ball 3 will not move even after balls 1 and 2 collides with it at the same time. Balls 1 and 2 will roll away after collision at the same speed. Energy is conserved. Now for the explination, but for simplicity, we need to assume the experiment was done in a vacume, without gravity, friction etc so that the speed you roll the ball into the wall is the same speed the ball rolls back to you. Looking at the first test, ball 1 has some kenetic energy when it hits the wall, the ball pushes on the wall while at the same time the wall is pushing on the ball (don't forget for every action, there's an equal and opposite reaction). Wall's net energy is unchanged, it received x from the ball but gave x back to the ball. Ball's net energy is also unchanged since it gave it's initial kenetic energy of x to the wall but also recived exactly x back from the wall. (This correspond to car hitting the wall at 100 mph). Looking at experiment 2, each ball has initial x kenetic energy. When the 2 collides, each transferred x energy to the other ball and recived x energy back which is exactly the same as if the ball hit a stationary wall. (This is identical to 2 cars hitting each other at 100 mph, but really is the same as 1 car hitting the wall at 100 mph). The 3rd experiment shows what happens to the wall. When 2 balls hit the 3rd, the 3rd ball felt the twice of the force balls 1 and 2 felt. (The wall feels the same force when 2 cars going at 100 mph hit at the same time or 1 car going at 200 mph hit it.) So when 2 cars collides at 100 mph, each car would only observe a 100 mph collision, but any 3rd party not in the cars will observe a 200 mph collision. (edit: The same would be observed if you used rigid objects like marbal instead of soft boucing balls, aka crumble zone of cars is not a factor) NYCDA (talk) 21:59, 19 December 2007 (UTC)
Thank you NYCDA for that explanation. It makes sense to me where others didn't for some reason. I was told by my dad as a young man learning to drive a car that having a head-on collision produces twice the damage, and so this is why I was so firm in my stance on it being that way - I mean, if my dad said it was that way, it must be so, right? Well, there goes another mistaken belief out the window! I sure do learn a lot here in the Wiki Reference Desk, even when I already think I know something it often turns out that I'm dead wrong. My apologies for taking up the bandwidth over this issue folks - you've won me over. -- Saukkomies 16:07, 20 December 2007 (UTC)
Woah, wait a minute, both cars are symmetricaly identical? How so? If you look at the line between the two cars right when they crash, you'll see that this is not a line of perfect symmetry. What about the driver's position? The steering wheel? The location of the air bags (if any)? The internal parts of the car that are not identical on both sides (eg. tailpipe, battery, tubes, etc)? What about any bumps in the road? The wind direction? The objects surrounding the road? The stones in the road? What about the fact, that for both cars to have collided symmetricly, they would have to collide in the centre of the road, and for that to happen, each car would have had to swerve left (for driving on the right side) or right (for driving on the left side)? Since there is osme asymmetry, any combination of factors could cause the cars to splinter in different directions from each other. If the cars did not collide in the middle of the road, one car would have moved in a different way than the other. Some splinters will likely leave the crash verticly or sideways. What about any last-minute reactions of the drivers? Could they possibly be identical? Thanks. ~AH1(TCU) 23:28, 22 December 2007 (UTC)

Two grounds not matching[edit]

Guys I have two digital design boards which use digital ground all perfectly designed PCB. These two boards have two major FPGA chip soldered along with some leds and switches. Now the case is that I use to send data from one to another using one data bus and one clock line.Along with this a ground and a ready signal is provided(4 wires). Problem here is that the leds in the receiver board flickers when I connect as usually.This should not occur,coz that is not how it's programmed.When I provided one more 2nd wire for ground, this problem is solved,program works. 2 ground wires are required to solve the case. I use 5V Dc supply seperatly for these 2 boards. Why isn't the ground shorting with one single wire?. I tried using big wire,fat wire,shielded cable and also measured the resistance between the two boards ground after shorting with 1 wire but it's almost zero.Noise level is under normal level.Please suggest me if there is any way that I can overcome this.It appears so strange and crazy in electronics!. ThanksBalan (talk) 04:34, 18 December 2007 (UTC)

Is your data at high speed - gigabits per second or higher? - if that is the case the length of the links will be critical, and you will need RF design techniques to make sure you have the right shape to transmit data cleanly. Graeme Bartlett (talk) 11:21, 18 December 2007 (UTC)
Are the two systems geographically seperate (say a mile apart)? If so you may have anomalies due to the two units having different ground, causing unwanted current flow over your cabling (see Ground loop (electricity)). You may need to optically or magnetically isolate the two units to prevent the ground loop. -- Finlay McWalter | Talk 12:56, 18 December 2007 (UTC)
All good ideas. In addition, you may have marginal timing, or ground bounce, or both. Check that your setup and hold times are adequate at the receiver. Also check that you have sufficient decoupling capacitors between your 0 V and 5 V rails on both boards. You may also have ringing on the data and clock lines. Are they properly terminated?
If you disconnect the data bus between the two boards, is there a voltage difference between the grounds of the two boards? If there is, then you have a ground offset problem and you need to tie the two grounds together at source (assuming they are not a mile apart). --Heron (talk) 13:04, 18 December 2007 (UTC)
Sounds like you have the same problem with ATA cables. Original ATA cables have 40 conductors and 40 wires and is limited to a lower speed. Newer cables uses 80 wires but still 40 conductors and achives higher speed due to the extra 40 ground wires. The extra ground wires stabilizes the signals. If you are using a ribbon cable, this might be your problem. NYCDA (talk) 20:47, 18 December 2007 (UTC)
That's right. And notice too that the ground wires in the ribbon cable fall in between the data wires. This separates the data wires from each other, which reduces crosstalk between the data wires. --InverseSubstance (talk) 17:12, 19 December 2007 (UTC)

US State with highest percentage of forests?[edit]

Which US State has the highest percentage of forests? What is that percentage? The same question about Canada's provinces and territories. —Preceding unsigned comment added by (talk) 14:01, 18 December 2007 (UTC)

I think that Maine with 90% has the highest, but I am not sure so don't quote me on it! And I don't know about Canada. Harland1 (t/c) 14:26, 18 December 2007 (UTC)
Alaska? -Arch dude (talk) 01:27, 19 December 2007 (UTC)
No, Alaska might have the most amount of forested land due to its enormous size, but there are huge areas of Alaska that are covered with Tundra, Glaciers, and snow capped mountains. My guess is that one of the northern states would be the winner - Maine (as said before) or Michigan come to mind. Of course it might also end up that Alabama or Mississippi might be the number one state... -- Saukkomies 10:16, 19 December 2007 (UTC)
If we're talking percentage, then Alaska is definitely not a contender. This report, Forest Resources of the United States, 2002, has a bunch of tables, including one that lists each state's total area and total forested area (with a description of how "forested area" is defined somewhere in the report). Unfortunately they didn't bother to calculate percentages and I can't be bothered to do it for every state. But just from looking at the numbers, it is obvious which states have the largest perentage of forested areas, and I calculated those. Maine is the winner, with 89.6% forest. It is followed by New Hampshire, at 83.9%, then a near tie between West Virginia (78.5%) and Vermont (78%). The next three, I think (didn't check all states closely enough to be sure), are Alabama (70.8%), Georgia (65.8%), and South Carolina (64.7%). Alaska, in comparison, comes in at 34.7% forested. I would have thought Idaho, Washington, and Oregon might come out with higher percentages, but I guess they all have large areas of treeless arid land. Pfly (talk) 23:52, 19 December 2007 (UTC)

Plants: CO2, respiration etc.[edit]

Hi everyone,

I was looking through a sixth-grade test and I found a question that I thought quite complicated:

I found this a difficult question, but it also brought to mind a bunch of other questions: Can a plant produce enough oxygen through photosynthesis to provide for its own respiration? How much oxygen would a plant require if it weren't producing any? How long can a plant survive in "stasis"without any CO2 or O2?

Any thoughts appreciated. Thanks! --Mary

I don't have numbers, but I would assume that in general, plants provide more than enough oxygen to provide for their own respiration. Otherwise there would be a world-wide oxygen deficit. (talk) 15:04, 18 December 2007 (UTC)
I have no numbers either but plants definitely produce more oxygen than they use in respiration. Harland1 (t/c) 15:34, 18 December 2007 (UTC)
Isn't the real limitation (in either case) the amount of CO2? There's plenty of oxygen in a random sample of air for the mouse but the CO2 quickly builds up. On the other hand, photosynthesis looks to have CO2 as the limiting factor in a sealed environment. — Lomn 15:43, 18 December 2007 (UTC)
Well the question seems to focus on the oxygen perspective. It does not ask why the plant does not grow but why doesn't it die (suffocate). The former is due to carbon dioxide depletion the latter due to photosynthesis producing oxygen. David D. (Talk) 15:56, 18 December 2007 (UTC)
But how necessary is CO2? If the plant has a supply of sugar, can't it live off that for a while? Surely the only necessary hour-to-hour process that the plant requires is respiration, right? Can it survive without respiration for any extended period of time? --Mary
It does not require CO2 for extended periods. But the answer to your question of "an it survive without respiration for any extended period of time" No. This is why flooding is bad for plants as the roots die from hypoxia. Some plants have an emergency cell death response to root hypoxia where the center of the roots die producing a conduit called aerenchyma to the bottom of the roots from the air. David D. (Talk) 15:56, 18 December 2007 (UTC)
Some plants, especially desert adapted ones, don't "breath" at all during daylight hours. They take in all of their oxygen/CO2 during the night in order to limit water loss during gas exchange. However, they do store some of these gasses in their tissues and use them during the day, so it's not like they shut down entirely during the day. Dragons flight (talk) 16:17, 18 December 2007 (UTC)
The point is that the amount of Oxygen produced by the plant depends on the amount of sunlight the plant gets in each 24 hour cycle. During the day, the plant consumes CO2 and makes oxygen - during the night, it consumes oxygen. So if you vary the amount of sunlight the plant gets, you'll alter the oxygen/CO2 ratio inside the sealed container. More sunlight = More oxygen, More darkness = Less oxygen. SteveBaker (talk) 15:58, 18 December 2007 (UTC)
I don't think the question even considers all of that. Just that plants produce oxygen and therefore can still respire as oxygen is not depleted in the chamber. The question does not appear to address light or dark conditions. David D. (Talk) 16:05, 18 December 2007 (UTC)
Right. They can't grow though - in order to do that they'd have to get carbon for their sugars and starches - and the only source is the CO2 in the air inside the container (which, presumably, isn't much). So unless the container is VERY large - the plant can't make an appreciable amount of additional growth. It might also have trouble simply surviving if (for example) it sheds it's leaves periodically because it won't have the raw materials to regrow them. SteveBaker (talk) 22:01, 18 December 2007 (UTC)
We agree, that is why I said above "The question does not ask why the plant does not grow but why doesn't it die (suffocate)". There would be no reason to expect the plant to grow unless it had appreciable storage reserves. This might be true if it is a seedling and the seed is still attached (i.e. a bean seedling). Even then it would not gain dry weight, just transfer it from the seed. David D. (Talk) 00:35, 19 December 2007 (UTC)

So, to answer the original question... Plants can utilize either O2 or CO2 to maintain homeostasis whereas Humans can ONLY utilize O2. It takes a whole lot more water and light to make energy primarily from O2, for a plant.
Mrdeath5493 (talk) 22:13, 18 December 2007 (UTC)

This seems a little confusing. Plants utlize O2 the same as humans for stasis. They can also make it, something humans do not do. CO2 for a plant is like food for a human and is not really part of the question. The last sentence: "It takes a whole lot more water and light to make energy primarily from O2, for a plant" is wrong, or I am misunderstanding your point? David D. (Talk) 22:21, 18 December 2007 (UTC)
Great answers here. I'm just wondering. Doesn't the plant survive longer simply from the fact that it's metabolism is a lot slower than the mouse? It simply requires less oxygen and CO2 over the same period of time right? —Preceding unsigned comment added by PvT (talkcontribs) 22:42, 18 December 2007 (UTC)
Well, in general, most plants are Poikilothermic, and therefore we will assume that general plants have low metabolic activity. Low metabolism means that cellular respiration is low and therefore each plant cell requires less oxygen, H20, glucose-->(which comes from photosnthesis - calvin cycle)--Hey mrs tee (talk) 02:47, 24 December 2007 (UTC)
plants do not use O2 like humans do. See Photosynthesis versus Oxidative Metabolism. A plants main source of energy is light, not CO2 or O2. Our main source of energy is food. The light reactions of photosynthesis make high energy molecules that are used to rearrange CO2 and water into glucose and oxygen. We need sugar to make high energy molecules (ATP) and ensure homeostasis whereas plants make ATP from light and use it to make sugar. (In humans: Food -> Sugar -> ATP) (In Plants: Light -> ATP -> Structure) Now, I was under the impression that after a long period with out CO2, the the equilibrium of the light reactions would shift making them harder to push forward because of high O2 concentration which would mean you need more energy input (light) and a higher concentration of the driving force (H ions from water).
Now looking back at all I have said it looks like CO2 and O2 are not really involved in the production of high energy molecules needed to maintain homeostasis in plants. However, CO2 is needed to make them grow. So I am confused and this is way too hard for a sixth grader.
Mrdeath5493 (talk) 23:16, 18 December 2007 (UTC)
1) Are you suggesting that plants don't have cellular respiration?
2) Roots don't photosynthesize. They get their "food" from sugar exported from the leaves. Those sugars are from CO2.
3) The ATP used in the cytoplasm of a plant cell is made by the mitochondria (as in humans). The ATP made by photosynthetic light reactions is only used in the chloroplast. So (Light -> ATP -> Structure) is incorrect. It should be (Light -> ATP/NADPH -> Sugar -> ATP -> Structure)
4) It would not be the high O2 that would cause the light reactions to slow when CO2 runs out but the high levels of NADPH in the chloroplasts. This would cause the electron transport chain to become fully reduced all the way to photosystem II. But this is not really addressed by the question because the timeframe of the question is hours, the time it takes a mouse to suffocate.
You seem to have a misconception here with regard to how photosynthesis integrates with the rest of plant metabolism. You are right that O2 and CO2 are not required for the production of ATP and NADPH in the chloroplast. You are also correct that the plant needs CO2 to grow. David D. (Talk) 00:26, 19 December 2007 (UTC)
It's a trick question. A plant cannot survive in a truly sealed container. If you seal out the light, the plant will die. Therefore, the difference is energy. An organism cannot survive without the appropriate energy input. In fact a mouse can survive in a sealed container, if photons can enter the container and there is a device in the container that can use photons to extract oxygen from CO2. One such device would be a nice big plant. -Arch dude (talk) 01:50, 19 December 2007 (UTC)
In the question the container is stated to be glass. On must assume there is light but that is a fair assumption. A plant does not extract oxygen from CO2, it is a product of water being oxidised by photosystem II. David D. (Talk) 02:58, 19 December 2007 (UTC)
Given the nature of the original question and the fact that it's aimed at 6th graders I still think the answer is " plant metabolism is a lot slower than that of an active, warm blooded, mouse thus it can survive a lot longer in a sealed container ". When I was 12 years old all I knew was that plants " breathed in " CO2 and " exhaled " O2. I didn't even know they required O2 for their own energy needs. Just my 2 cents PvT (talk) 10:54, 19 December 2007 (UTC)
What counts is the syllabus. They probably are taught that plants respire. However, there is such a strong misconception that animals respire and plants don't respire but photosynthesis instead that at university level these mistakes are still made. I have even met biology graduate students that are not sure if plants have mitochondria. It just does not sink in, there is some mental block for those that focus on animals. David D. (Talk) 11:41, 19 December 2007 (UTC)

Possible to use neutrinos for communication?[edit]

Since neutrinos can pass through solid objects without any problems, I thought they might be useful as a means of wireless communication. One could be inside of a room with 3 foot lead walls, or in a cave deep underground, and the neutrinos would be able to pass through it without any problems. Is this at all possible? (talk) 16:00, 18 December 2007 (UTC)

Are you asking about the near future? Or the distant future? Because modern-day neutrino detectors are not really small enough to put into a cellphone. (talk) 16:15, 18 December 2007 (UTC)
Distant future. (talk) 16:17, 18 December 2007 (UTC)
Neutrino-based commmunications (and observation) systems are a staple of 'hard' science fiction writing; as 72.10 notes, detecting neutrinos with a handheld device currently requires unobtainium. TenOfAllTrades(talk) 16:27, 18 December 2007 (UTC)
The major problem is that neutrinos also fail to interact with your receiver ;-) --Stephan Schulz (talk) 17:06, 18 December 2007 (UTC)
I never mentioned anything about the device being small. I just asked if it was possible to use neutrinos for communication. (talk) 17:07, 18 December 2007 (UTC)
But I think the responses are valid, as you may not have considered quite how large the detectors are. The Sudbury Neutrino Observatory requires 1000 tons of heavy water to detect neutrinos. Aside from detection, though, no one has mentioned whether it is easy to control the emission of neutrinos in order to create a message. Is it? --Mary —Preceding unsigned comment added by (talk) 17:12, 18 December 2007 (UTC)
This is not a problem. One "traditional" way to create a neutrino beam is using a particle accelerator, and that's easy to modulate. You can also modulate the reaction rate of a nuclear reactor, but even with a fast responding reactor you'd be lucky to get a few bits per minute. However, with current technology you probably need several hours to collect enough neutrinos to decide if a single bit is a 1 or a 0 anyway, so even the modulated reactor would not be the bandwidth limiting step. LouScheffer (talk) 17:52, 18 December 2007 (UTC)
You say "I never mentioned anything about the device being small", but you referred to a room and a cave, which limits the possible size. Anyway, as you've seen by now, the answer is that it's theoretically possible if the technology could be made small enough. --Anonymous, 17:35 UTC, December 18, 2007.
Don't be pedantic. (talk) 18:14, 18 December 2007 (UTC)
Don't be preposterous. —Steve Summit (talk) 02:54, 19 December 2007 (UTC)
If you really don't care about inconvenience and size, then yes, you could build a 1/2 mile particle accelerator and beam neutrinos to a 1000 ton neutrino detector virtually anywhere else on Earth. You might even be able to engineer a decent bit rate (i.e. kbps), however I can't imagine there being much of a point. Dragons flight (talk) 17:25, 18 December 2007 (UTC)
No, I never said I don't care about inconvenience and size, I just wasn't asking about that. And it doesn't matter if you think there's a point or not. The applications for such a device can be realized if a need for it arises. The fact that it's possible to communicate wirelessly between two points even if there's over 100,000 miles of lead inbetween them, is an important revelation. I think most people are assuming, I'm thinking of a device we can build right now, and use. Not at all. Future concepts, require a groundwork of whether something can accomplish what you want to do in the first place. Whether we can build such a device now, is irrelevant, because that's not what the groundwork is. The helicopter was thought up way before it was ever practical to build one. But that didn't stop scientists from realizing that it was possible. (talk) 18:14, 18 December 2007 (UTC)
Well then let me be more specific. It's not possible, even in principle, to use any known form of matter to build a compact neutrino detector. Dragons flight (talk) 18:35, 18 December 2007 (UTC)
So what? We already know that. Repeating yourself over and over again, doesn't add anything meaningful to this topic. (talk) 18:41, 18 December 2007 (UTC)
Why are you being so hostile? People want to give more complete answers. If the only answer you had received above was one word -- "yes" -- then would you not have asked for more information? Of course. So don't be hostile when people give you that extra information. Naturally people would assume that requiring 1000 tonnes of heavy water, for instance, would be pertinent information... -- Mary 18:50, 18 December 2007 (UTC)
I'm not. Yes, 1000 tons of heavy water is fine, but when I explain that size is not something I'm asking about, I usually like people to understand that, rather than pointing out the size over and over. (talk) 18:57, 18 December 2007 (UTC)
Thank you, 64.236 for your practical demonstration of Kant´s categorical imperative. I am certain that your thoughtful responses and the appreciation you have indicated for the answers have increased the motivation of the volunteers on this reference desk. --Cookatoo.ergo.ZooM (talk) 19:02, 18 December 2007 (UTC)
You don't understand the rules. You have to assume good faith and can't be rude. He can say whatever the hell he wants to the people who are trying to help him. You'll get used to it. -- Coneslayer (talk) 19:08, 18 December 2007 (UTC)

This discussion isn't really appropriate here. I think we should get back on topic. Anyway, just to help illustrate my point for the use of such a device, it could be used to communicate with colonies on the dark side of heavenly objects, like the moon. This was what I was talking about before, about a need arising. It doesn't have to have a use now, just a potential use. (talk) 19:12, 18 December 2007 (UTC)

Here we see a common problem. Someone has a bright idea that seems to them to be entirely wonderful and revolutionary - and they know just enough science to be dangerous! They bring it to the RefDesk in the hope that we'll immediately shower them with praise and wonderment at their amazing intellect. When we explain, carefully and logically why the idea is impractical at best, and more likely, completely impossible - they become hostile. They also tend to start to add caveats that will narrow the scope of our responses to an answer they would like to hear. If you ask a question - which people come here to answer of their own free will without payment, the least you can do is listen to what they have to say.
Well, guess what OP...IT WON'T WORK! Even if something like a modulated nuclear reactor and a few cubic kilometers of dry cleaning fluid that could transmit (optimistically) one bit per hour were considered "feasible" - we could do better by using high explosives and seismometers to transmit through the solid earth. Yes - it too would be hard - but you'd get a better data rate (albeit with poorer latency), you'd only need a tiny receiver and the transmitter might even be a thing of manageable size (compared to a large nuclear reactor at least). As a communications device, both gadgets have some exceedingly bad characteristics - firstly, they are spectacularly slow (compared to radio waves), they are both inconveniently bulky and hugely expensive, they also broadcast your message to everyone - and only one person on the entire planet can be transmitting at a time because there is very little directional sensitivity in the receiver. In the case of the 'neutrino radio', noise rejection is going to be a bitch because we've got this honking great neutrino source a mere 150 million kilometers away - and unless you are rather careful where you place source and transmitter, your message is going to be completely drowned out once a day. But the appalling slowness of the device is its ultimate downfall. If you wish to transmit the string "Hello World", from one side of the world to the other, it would certainly be quicker to write the message on a post-it note, book a plane ticket to your destination, sometime later in the week you can fly there, relax for a couple of days to get over your jet lag, then bicycle to the recipient and deliver the message in person - and it'll STILL get there way ahead of the neutrino transmitter!
SteveBaker (talk) 21:16, 18 December 2007 (UTC)
Haha, no. For one thing, it's not even an idea that hasn't been considered already. And I wouldn't have asked if neutrinos can be used for comm in the first place, if I already believed it would work. I was asking if it would work. You honestly believe I care about praise from some random goobers on the internet who probably edit wikipedia while still in their underwear? That's stupid. (talk) 14:36, 19 December 2007 (UTC)
The discussion is entirely appropriate. Can neutrinos be used for communication? Sure, but only if we allow a ludicrously large amount of handwaving (that is, magic). But given the amount of magic we have to use, the question is meaningless. I could just as meaningfully state that we could use woolly mammoths to communicate with Abraham Lincoln. All we need is a woolly mammoth generator and a temporal distortion unit (no receiver is needed, as Lincoln is quite capable of seeing a mammoth already). All that's lacking is the practical technology that has no present basis in reality, but hey, who's to say we won't invent it? So mammoths are clearly a superior communications paradigm versus neutrinos.
Does this convey the problem with your original question, and why the discussion is appropriate? — Lomn 19:22, 18 December 2007 (UTC)

Also with the Colonization of Titan, it could be useful. It would be very difficult to communicate with Titan when Saturn is in the way. (talk) 19:25, 18 December 2007 (UTC)

This is what relay satellites are for, in other words more practical and cost effective technology that already exists. With neutrinos you need to generate ~10^20 for every 1 that's detected, so virtually all of your energy and signal is immediately wasted. Dragons flight (talk) 19:31, 18 December 2007 (UTC)
Background noise would be a big problem in any neutrino based communication system - every square centimetre of the earth is exposed to 70 billion neutrinos per second - a nuclear reactor can produce 1020 neutrinos per second, but these will radiate in every direction. Unless you made the beam directional, it would be less than 1% of the background noise within 70 metres of the source - if you did make the beam directional, it would become far more difficult to communicate (consider the difference between using a mobile and a satellite phone - the mobile works instance, while the satellite phone needs to be carefully lined up so that the beam heads toward the satellite). For your moon example, you would need a neutrino source 1022 (roughly the same as the number of grains of sand on all the beaches of Earth) times larger than a nuclear power plant. Focusing the neutrinos would be your only option, but would be almost impossible, as the neutrinos would pass through anything that tried to block them. Laïka 19:32, 18 December 2007 (UTC)
There are advantages over relay satellites. For one thing, a neutrino comm device can be deep underground, and well protected. A relay satellite is in space, and is vulnerable. Lets say, if our goal is to make sure communication isn't disrupted in a time of war or unforeseen emergency, a neutrino comm device would be preferable. (talk) 19:39, 18 December 2007 (UTC)
If you get to posit interplanetary neutrino communication, I get to posit indestructible satellites. (To put it another way, lots of things have "advantages" if you get to ignore their disadvantages.) -- Coneslayer (talk) 19:46, 18 December 2007 (UTC)

Most of the background neutrino noise is coming from the sun, the interior of the Earth, and nuclear reactors. Fortunately, neutrino detectors can be directional. Now, if I recall correctly, the Kamiokande could even tell when nuclear powered ships were offshore. Now, it's been very expounded upon above that you simply can't make a small neutrino detector. But that doesn't stop you from making a small neutrino emitter. In any normal circumstance, this would be entirely pointless, and you may as well go with radio or whatever suits your needs. But let's say you want to send a spy into an enemy country. He could stash a relatively small nuclear reactor in his van, heavily shielded to block most of the detectable radiation. But his neutrinos would get out just fine; they wouldn't tip off anyone monitoring radio traffic, and it couldn't be jammed. Bandwith would be a significant issue, and you'd have to hope the enemy doesn't have nuclear reactors all over the place...Of course, if you can slip a nuclear reactor into a country without being noticed, you could probably do a lot more. If we ever have pocket sized sources that emit detectable levels of neutrinos, it could be a very intriguing possibility. Someguy1221 (talk) 20:24, 18 December 2007 (UTC)

So he doesn't tip off enemies listening by radio -- but how does he avoid tipping off enemies listening by neutrino? Not really a solution. — Lomn 20:27, 18 December 2007 (UTC)
Because he's not pointing his neutrinos at the enemy's enormous tank filled with 1000 tons of heavy water? (talk) 20:35, 18 December 2007 (UTC)
Where was the evidence of a directional neutrino generator, again? I missed that one. Besides, we can already bounce tight-beam radio/laser transmissions off satellites and do the same thing with real actual technology. This is yet another solution in search of a problem. — Lomn 20:40, 18 December 2007 (UTC)
Let's say we do develop a pocket sized neutrino emitter. Now tell me, do you have another way to get a signal out of some evil guy's underground fortress? Radio would be jammed or blocked outright, and laser signals have no avenue of escape. It might be a great for something as simple as planting a bug on (or in) an informant going for a meeting with a mob boss. Their little hand held bug sweepers would easily pick up any radio bug the moment it started transmitting, and they would probably notice if you aimed a laser pointer at a window. But it would be highly unlikely they would have neutrino detector on hand. So you see, finding a problem for this solution is not actually so difficult, but there are some extrmee engineering obstacles in the way. Someguy1221 (talk) 21:24, 18 December 2007 (UTC)
There is no "Let's say we do" here. Neutrino's go through vast amounts of 'stuff' without hardly noticing it's there - that's the reason our OP wants to use them after all. The reason that neutrino detectors have to be huge is precisely because neutrino's don't interact much. We're talking about a particle that can go through a million miles of solid lead without much chance of being stopped by it! A small detector couldn't possibly stop enough neutrinos to detect that they were even there. A typical cubic-kilometer detector manages to stop (and thereby detect) a few neutrinos each day from the sun. From a smaller source - vastly fewer. If you build a cubic-meter sized detector, it would pick up 1/(1000 x 1000 x 1000)th as many neutrinos. Which means you'd have to wait about a million years before you detected a neutrino - and even then, it would almost certainly be one from the sun. If (has been suggested) we could build a HUGE nuclear reactor that could produce even 1% of the neutrinos that the sun produces - then your detector MIGHT manage to detect whether it sent a '1' or a '0' after a couple of hundred million years of detecting. So NO, you can't have a small neutrino radio detector. It's not an engineering problem that has to be overcome - it's a physical impossibility that derives it's impossibility from the very reason it might be desirable (ie that neutrinos go through stuff). It's pointless to even speculate about such a device. SteveBaker (talk) 21:41, 18 December 2007 (UTC)
That was actually just a typo on my part, I meant to say "pocket sized neutrino emitter". If you'll notice, my statement doesn't make sense otherwise. Someguy1221 (talk) 21:44, 18 December 2007 (UTC)
The point about the underground fortress is well-taken. That said, I'm skeptical about the lack of enemy detection (unless we start positing a directional transmitter). Since the neutrinos aren't stopped by anything, an enemy detector doesn't have to be close. If those detectors can get the direction of the source, then any 3 detectors should be able to triangulate pretty well. And then, yeah, there's all the engineering obstacles :) But it's fun to think through. — Lomn 21:50, 18 December 2007 (UTC)
Perhaps if you needed to communicate with someone living on the inside of the Moon. That might be neat. (talk) 20:53, 18 December 2007 (UTC)
Possibly if you needed to do so without alerting people on Earth to the existence of a hollow-moon colony. (talk) 20:57, 18 December 2007 (UTC)
...and the Lunar colonists have a few cubic kilometers of dry cleaning fluid to spare...and they don't want to send a reply - and they don't want to be able to hear the message when there is a full moon...and they didn't think to leave a radio antenna on the surface with a wire trailing down to the interior...and they don't mind waiting about one day per character transmitted. SteveBaker (talk) 21:21, 18 December 2007 (UTC)
They like wearing suits and are very keen on keeping them clean...and they don't have anything to say - and they observe religious silence on full moons...and they don't want anyone to notice a radio antenna (that would just give it away)...and they're very patient. OPEN YOUR MIND STEVE Someguy1221 (talk) 21:27, 18 December 2007 (UTC)
Come on, why wouldn't a hollow-moon colony have a few hundred tons of dry cleaning fluid?
Or, to posit another far-fetched sci-fi idea that's a bit of a stretch, what if you were trying to communicate a simple "go" code to a large number of massive, buried devices hidden throughout the solar system. (Possibly the machines perform dry-cleaning functions as part of their normal operation.) I suppose you'd need an unrealistically powerful neutrino source at that point, though. Oh well. APL (talk) 00:15, 19 December 2007 (UTC)
It occurs to me that the right way, and indeed the only sanity-preserving way, to respond to any of's questions is the same way you respond to the fervent proponent of a newly-invented perpetual motion machine: "Great idea! Come show us when you've built a working one!" —Steve Summit (talk) 02:36, 19 December 2007 (UTC)
Naa. Such menial tasks are beneath him. He's the "big idea" guy! We poor slobs can do the number crunching since he's graced us with the key concept. -- Coneslayer (talk) 02:58, 19 December 2007 (UTC)
Coneslayer, stop trolling. Summit, when a person asks a question, that's not synonymous with wanting to build a new invention. (talk) 14:36, 19 December 2007 (UTC)
64, do please stop calling kettles black. I've half a mind to delete this entire thread. —Steve Summit (talk) 15:02, 19 December 2007 (UTC)
Go ahead. The discussion is over, and my question has been answered. But don't throw out accusations like that. That's bias. Coneslayer hasn't contributed to this thread at all, except to ridicule and insult. (talk) 15:10, 19 December 2007 (UTC)
Why should I? You have amply demonstrated that you don't take real learning seriously—you think it's beneath you to actually learn something about the basic concepts that could help you solve problems yourself. Your interactions with people who help you consist of either ignoring them, or attacking them. In the dozens of questions you've asked, I don't remember you ever thanking someone for a helpful answer. You either argue with responders, or move on to your next ill-thought-out idea. You are supremely critical of other people's responses, but apparently have no such filter for your own ideas. Anything that pops into your head, you put on the reference desk without thinking seriously about it. Yet despite your rudeness to responders here, you are ever eager to wrap yourself in the mantle of "assume good faith". To answer your questions, you depend on the kindness of people who have paid their dues and learned how to think critically, yet you hold these people in contempt. You seriously need to develop intellectual maturity and a more resourceful approach to problem solving (along with human interaction). -- Coneslayer (talk) 15:28, 19 December 2007 (UTC)
Of course I take learning seriously. I wouldn't be asking so many questions otherwise. I was taught to never stop asking questions. And there is no limit to the amount of questions I can ask on the reference desk, nor should there be, so I will continue to ask questions. That's what learning is about. And yes, I have thanked people before, either on the reference desk or on their talk page, where it belongs. If you feel I have come off rude, I apologize, but nothing was ever intentional. Keep in mind it takes two to tango. Usually someone was rude first, then it goes from there. That aside, if you don't want to answer my questions, feel free to abstain, but don't bog down the discussion with these rants, and personal attacks. It only serves to make ruin your credibility, and demonstrate immaturity. You may want to read this, Wikipedia:Staying cool when the editing gets hot64.236.121.129 (talk) 16:21, 19 December 2007 (UTC)
Usually someone was rude first, then it goes from there. Hmmm - good point. So - let's be clear about this - who threw the first hostile post into this thread? Aaahh...that would be: Don't be pedantic. courtesy of...drum roll please...User: a model of WP:AGF there! It goes deeper than that though - as Coneslayer points out - you have a history here. But actually, I don't think that's the problem.
Throughout this thread, whenever anyone comes up with a potential roadblock to your idea, you immediately act as if you'd known that all along - we say something like: "Oh but the detector has to be unreasonably huge" - you say something along the lines of "Yes, but of course I knew THAT"....with the strong subtext of..."(but now I'm going to say that it's irrelevent how big it is - so my idea for using neutrinos for communication is still OK!)" So we are lead to believe that either:
  • You knew in advance that neutrino communication was possible but horribly, horribly impractical (in which case why the heck did you ask?)...OR...
  • Every time someone tried to tell you something interesting and important on the topic, you acted like you'd always known that and that the respondant was stupid to have even pointed it out (when in reality, you only just learned that).
So either you are wasting everyone's time asking questions to which you already know the answer - or you are being insufferable to people who are honestly trying to educate you. If you doubt the truth of what I'm saying, notice that that you have so many smart people yelling at you right now...when those very same people are usually exceedingly polite to our questioners. What's the difference between all of those other threads and this one? The difference is YOU - so we may reasonably conclude that this is indeed your fault somehow - so a proper apology and a change of future behavior is indeed called for here. SteveBaker (talk) 17:57, 19 December 2007 (UTC)
Haha. *pats your head* You're mad. (talk) 17:08, 20 December 2007 (UTC)
If you are serious about learning, then why did you respond "Naa" when I gave you advice as to how to really learn? "Asking questions" is fine, but it only gets you the answer to those questions. Developing reasoning skills, and learning the basic principles of a subject, is what gets you to the point that you can answer questions on your own. I know Steve Baker also gave you this advice, and you have rejected it. This communicates to the rest of us that you are not really serious about learning. Would you care to clarify why, exactly, you think learning the basics is beneath you? This is your chance. -- Coneslayer (talk) 16:30, 19 December 2007 (UTC)
Coneslayer, a word of advice: this person, if not a troll, is certainly acting like one. Best not to feed him. —Steve Summit (talk) 16:40, 19 December 2007 (UTC)
You know, I was going to give a meaningful response to Coneslayer's question, but now I don't really feel like it. Just remember that statement about calling kettles black Summit, then realize if your posts are contributing anything useful. (talk) 16:50, 19 December 2007 (UTC)

Hydrogenated polyisobutene?[edit]

This hand lotion says it contains "hydrogenated polyisobutene", but this chemical name doesn't make sense to me. It seems to me that polyisobutene is already saturated, and hydrogenation only makes sense for unsaturated compounds. How can you hydrogenate polyisobutene? —Keenan Pepper 23:29, 18 December 2007 (UTC)

This substance is Butyl rubber that also contains a proportion of isoprene, whcih is poly unsaturated, and will leave some unsaturation when polymerised. Graeme Bartlett (talk) 01:44, 19 December 2007 (UTC)
So does that mean it's really polyisobutene with some hydrogenated polyisoprene? —Keenan Pepper 03:47, 19 December 2007 (UTC)
It sounds like it, although so far I have failed to find a reference to confirm it. What I have found is that it is not completely hydrogenated and still has a non zero iodine number. Graeme Bartlett (talk) 19:58, 19 December 2007 (UTC)
There's a structure given on this page referenced from our polyisobutene article that supports these thoughts. DMacks (talk) 16:22, 20 December 2007 (UTC)