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Author Topic: Ask your dumb Science questions here, you idiot  (Read 31629 times)
MadPiper6
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« on: September 18, 2012, 10:08 am »

Is quantum physics being used for any practical applications yet, by folks that aren't ducks?

Are there probably more dimensions of spacetime than we experience?
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norumaru
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« Reply #1 on: September 18, 2012, 10:22 am »

I read yesterday that a pressurized spring weighs more than a relaxed one, and read an explanation via e=mc2 that seemed to make sense, but I also saw differing opinions.

I also always thought that converting energy to mass was a pretty tricky thing to do, and the idea of that being true kinda violates my admittedly rudimentary understanding of physics.

So, I feel really dumb for even asking, but is it true?
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YaoMing
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« Reply #2 on: September 18, 2012, 11:02 am »

Quantum Mechanics have a great many applications, the biggest example is semiconductors. The theory behind semiconductors relies on quantum mechanics. Try to imagine a silicon crystal lattice, by itself silicon is not very conductive for electrons to jump through the lattice. By doping the silicon with small amount of impurities, you can create "holes" which makes electron much easier to jump through. this phenomena can be explained by taking account of the different energy level of the molecular orbitals for both silicons and added impurities.

Take your laser pointer, the basis behind it is also based on quantum mechanics. fluorescence is also based in quantum mechanics.

You have to realize, quantum mechanics is a pretty old field. Schrodinger's equation was back in 1927, and really opened up a way to draw up a great approximation of molecular orbitals and their interaction.

This is all from the point of view of someone who is studying chemistry. And you have to a really decent grasp of Quantum mechanics to explain phenomenons that you encounter. 
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barco
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« Reply #3 on: September 18, 2012, 12:03 pm »

Is quantum physics being used for any practical applications yet, by folks that aren't ducks?

Are there probably more dimensions of spacetime than we experience?

To add to the above, QM is, experimentally, by far the most successful field of science. The results are crazy accurate. Michio Kaku, in his book, Hyperspace, says "It is often stated that of all the theories proposed in this century, the silliest is quantum theory. In fact, some say that the only thing that quantum theory has going for it is that it is unquestionably correct."

As for dimensions, maybe? The family of string theories require it, and it'd be a convenient explanation for why gravity is so weak, but nothing has been proven yet (and string theory is potentially untestable).
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fermun
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« Reply #4 on: September 18, 2012, 12:43 pm »

LEDs and solar panels required understanding of quantum to make. They both work essentially as being 2 different types of semiconductor in contact with each other in a circuit though, so YaoMing covered it, essentially.

Semiconductors can be doped with impurities that have an excess of electrons or impurities with a deficit of electrons, either type of impurity can allow them to conduct, but the way they do it is slightly different.

A LED works because you have electrons going from a semiconductor with a high energy level molecular orbital to one with a lower energy level molecular orbital. When it makes the jump, that excess energy gets spit out as a photon of the difference in energy between the two molecular orbitals.

A solar panel works because you have electrons going from a semiconductor with a low energy level molecular orbital to one with a higher energy level molecular orbital. When the electron hits the barrier between these two, it is stuck and needs more energy to jump to the new semiconductor, but along comes light of the right amount of energy, and the electron can pop across and continue its merry way, having gained energy equivalent to how much that photon had.
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Johnny Roastbeef
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« Reply #5 on: September 18, 2012, 02:19 pm »

I read yesterday that a pressurized spring weighs more than a relaxed one, and read an explanation via e=mc2 that seemed to make sense, but I also saw differing opinions.

I also always thought that converting energy to mass was a pretty tricky thing to do, and the idea of that being true kinda violates my admittedly rudimentary understanding of physics.

So, I feel really dumb for even asking, but is it true?

Apparently this physics book says so too.  I've actually never heard that before myself.
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barco
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« Reply #6 on: September 18, 2012, 02:35 pm »

So, you can get stuff that perfectly (??) insulates against electricity, but it seems everything is permeable to a magnetic field. What gives? Aren't they basically the same thing anyway?
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HyperGlavin
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« Reply #7 on: September 19, 2012, 12:58 am »

I read yesterday that a pressurized spring weighs more than a relaxed one, and read an explanation via e=mc2 that seemed to make sense, but I also saw differing opinions.

I also always thought that converting energy to mass was a pretty tricky thing to do, and the idea of that being true kinda violates my admittedly rudimentary understanding of physics.

So, I feel really dumb for even asking, but is it true?

I had a physics teacher explain this to me once, but he used a pocket-watch as an example and ran through a simple mock-up of the calculations required. As could be expected when working with the speed of light, the change in mass is infinitesimal and therefore negligible for almost every situation. The only real issue with the idea would be conservation of mass and energy, but if you're looking at a closed system involving the watch, then you'd also have to take into account whatever was winding it, which would lose energy, and therefore mass.
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norumaru
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« Reply #8 on: September 19, 2012, 02:51 am »

Yeah, I was aware that the change in mass isn't big enough for me to have to consider it when I build my spring-based doomsday device, but I really wanted to know where the extra mass came from.

fermun, being more intelligent and handsome than me, explained it with a thing called "virtual particles": Energy is converted into mass all the time, into particles and antiparticles to be precise, which then touch and are converted back into energy. A compressed spring has more stored energy, hence more particles, hence more mass. Thanks fermun!
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RummyLu
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« Reply #9 on: September 19, 2012, 03:05 am »

Why does my partner say that putting salt in the cooking pot makes the water boil faster?
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HyperGlavin
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« Reply #10 on: September 19, 2012, 03:15 am »

Adding salt to water actually increases its boiling temperature, but only by a fraction of a degree so it's ultimately pointless.
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barco
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« Reply #11 on: September 19, 2012, 03:21 am »

Adding salt to water prematurely can also cause pitting, damaging your pot! Wait until that shit is boiling, yo
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HyperGlavin
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« Reply #12 on: September 19, 2012, 03:23 am »

Or alternatively, don't use salt at all. Pasta tastes just fine as it is.
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RummyLu
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« Reply #13 on: September 19, 2012, 03:30 am »

Oh sweet, thanks guys. I suppose my next question should be, "why do Europeans love salt so goddamned much," but I'll let it pass for now.
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Mr Gale
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« Reply #14 on: September 19, 2012, 07:57 am »

I always put a pinch of salt in when I am boiling pasta, the packets SUGGESTS IT so you HAVE TO.
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jimbob
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« Reply #15 on: September 23, 2012, 01:14 pm »

But if the pan is smooth and the water is around the boiling point, adding small crystals of salt might create nucleation points for the bubbles to form, since they will increase the surface area of solid in the hot water. That effect wouldn't occur if you added the salt earlier though, as it would have time to dissolve.
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thermus aquaticus
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« Reply #16 on: September 24, 2012, 09:38 am »

Also salt lowers the water's heat capacity, so it gets to boiling point faster. Also it reduces its thermal conductivity, so that might slow it down. Of all the effects mentioned so far, I don't know which one would dominate, but you can bet one pinch in a pot would make sure the effect is too small to notice.

So, you can get stuff that perfectly (??) insulates against electricity, but it seems everything is permeable to a magnetic field. What gives? Aren't they basically the same thing anyway?

Electricity and magnetism are effects of the same fundamental force, but they're still different effects doing different things. In the case of your question though, they're the same. Electric and magnetic fields penetrate or get blocked by the same things, as far as I know. By "electricity" you must mean an electric current, which you could say is another effect of that fundamental force. Insulators don't have any electrons that are weakly bound enough to let them flow freely through the material. But that doesn't stop fields from going through the material.
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« Reply #17 on: September 25, 2012, 04:43 am »

My boss at a bar used to put loads of salt in buckets of cold water, put drinks in the bucket and then put the bucket in the freezer. He wanted it to go below freezing without turning to ice, so the drinks would cool down quicker. Although I suppose if it was below zero, any drink you have in the ice bucket would freeze anyway.
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HyperGlavin
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« Reply #18 on: September 25, 2012, 05:16 am »

Salting ice is a great way to cool drinks down because it significantly lowers the freezing temperature of water, forcing it to melt. The process of melting requires thermal energy, which is then drawn into the ice from the surrounding air/water/drinks, cooling them down. You don't need to put the bucket in the freezer, but it's a good idea to fill the air gaps in the ice bucket with cold water to increase efficiency.
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« Reply #19 on: September 25, 2012, 05:47 am »

Awesome. Science!
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