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April 5[edit]

Hawking's Fact or Theory ?[edit]

I'm in the UK and while watching a recent documentary regarding Steven Hawking and the latest 'string theories' my partner asked me a simple question and I was stumped. My partner is in no way a scientist and questioned, 'So is this fact or just what people think?'. Can any model of the universe be proven as factual or is it just mathematical modelling? This question may seem silly to the scientists out there but I regret I am not one of them. I teach six year olds! Thank you for your wisdom! Kirk UK —Preceding unsigned comment added by 88.144.9.132 (talk) 00:09, 5 April 2008 (UTC)[reply]

It's a theory. Mind you, that doesn't mean it should be dismissed easily. Theories have been tested and found to accurately model what we know of the universe, and Hawking's theories are no exception. String theory on the other hand is mostly just a mathematical model. The term "theory" is more of a cultural attachment than a scientific appellation, because string theory requires some rather wonky things to be true for it to work. And we don't have the capacity to test those things right now, so it's more of a "string hypothesis." It's mathematically sound, but not necessarily accurate. -- Kesh (talk) 01:33, 5 April 2008 (UTC)[reply]

The easiest way to think of the difference between facts and theories is that facts are simple bits of data about the natural world, whereas theories are explanations about the natural world. An example: it is easily observable that a ball dropped from your hand on Earth will fall towards the ground. This is a fact. The reason for this is the theory. Isaac Newton would have said that the mass of the Earth itself exerted a force on the ball, pulling it to the ground. Albert Einstein, by contrast, said that the mass of the Earth deformed spacetime in such a way that towards its center was the path of least resistance for the ball. Two very different explanations of the same phenomena; two very different theories.

Any model of the universe will be a theory by definition. It is a model. It is not the sort of thing that is a "fact", a small piece of data. This is not a problem. Facts are not "proven" theories, facts and theories are two totally different categories of information.

Einstein's Special and General Relativity are both theories. Newton's theory of gravitation is, as the name implies, a theory. Darwin's idea of natural selection as the engine of evolution is a theory.

Is String Theory a theory? Well, it wants to be a theory. Is it really one? Scientists and philosophers disagree. Some don't even think it is a theory because there isn't any way it can currently be proven incorrect. If an explanation about the natural world cannot be tested—proven right or wrong—then it is not a scientific theory. For example, instead of Newton or Einstein's theories I could just as easily say that my theory of why the ball falls is because there are invisible, intangible fairies who carry the ball to the ground. It's a theory that perfectly accounts for any phenomena that one might see. But that's the problem: you can't do anything to test it, you can't possibly prove it wrong. As such, you cannot distinguish between my theory and Newton's theories when it comes to which is more correct. So this is not science. You can distinguish between Einstein's and Newton's theories—they give different experimental and observations predictions in some cases, and indeed it turns out that Einstein's theories perform better than Newton's.

So anyway, back to String Theory. It's very dubious whether it can be truly tested at the moment. At the moment we have no way of distinguishing between a universe run by String Theory and a universe run by the Standard Model of physics. Someday fairly soon we will be able to test some aspects of some variations of String Theory, but even if those tests come back negative they won't really distinguish between String Theory itself and anything other than String Theory. There are some highly imaginative experiments with tools we do not have and may never have that could test String Theory, but given that they are not real options it's not clear that they count towards the philosophical question. Anyway, it's an active question.

Sorry to lecture; your question seemed to me to have two questions in it (what is the difference between fact and theory, and is String Theory a theory). I tried to be clear but not condescending, maybe I have been successful, maybe not... --Captain Ref Desk (talk) 01:58, 5 April 2008 (UTC)[reply]

I thought you did a great job, and I wish the sorts of people who run American school boards could all read your answer. --Sean 13:43, 7 April 2008 (UTC)[reply]

A very complete answer. You might like to read the article on Karl Popper. William Avery (talk) 09:08, 5 April 2008 (UTC)[reply]

Also, I suppose you know the String theory strip from xkcd. – b_jonas 18:44, 6 April 2008 (UTC)[reply]

Train Washing Machines[edit]

Hello all. I am looking for a site which has detailed descriptions of new(est) technology in the field of recycling the water used by train washing machines. I have looked, but been unable to find anything useful. Thanks in advance for any help.

Cuban Cigar (talk) 03:04, 5 April 2008 (UTC)[reply]

Are you sure that trains actually have washing machines ? I would think that the expense of hauling around the washing machines, dryers, and water would be prohibitive. For things like towels and bedding on sleeper trains, they could instead drop off dirty laundry and pick up clean laundry at each station. That's how I'd do it if I ran a passenger railroad. StuRat (talk) 13:52, 5 April 2008 (UTC)[reply]

Perhaps the questioner is referring to machines which wash the train [1] [2] Think outside the box 14:52, 5 April 2008 (UTC)[reply]

Hmm, that could very well be what they meant. StuRat (talk) 04:46, 6 April 2008 (UTC)[reply]

If so, have a look at this. It's about vehicles in general, but should be adequate. —Preceding unsigned comment added by D0762 (talk • contribs) 15:51, 6 April 2008 (UTC)[reply]

In the railway business they refer to them as 'Carriage Wash' machines, you might try some heavy duty railway company like GEC.

Gauge to track relative movement[edit]

Does anyone know a name for the type of gauge shown in this image? Do we have an article on it?

The device is intended to track the relative movement of two objects (in this cases, two parts of a wall that has split apart). I think most of us who live in earthquake zones have seen a few of these; I imagine that they must also be used for buildings that are settling unevenly in other contexts as well.

Feel more than free to edit the description on Commons and add any appropriate categories: this is one of those cases where having snapped the photo does not mean I know a lot about the topic at hand. - Jmabel | Talk 05:08, 5 April 2008 (UTC)[reply]

I've seen it called a crack gauge or crack width gauge, and I'm shocked to see that we don't have an article on it yet (as of the following timestamp). --Heron (talk) 09:19, 5 April 2008 (UTC)[reply]

That sounds more like something which might be used by plumbers. :-) StuRat (talk) 02:25, 6 April 2008 (UTC)[reply]

It's a mechanical strain gauge, like the one shown here. Gandalf61 (talk) 12:58, 5 April 2008 (UTC)[reply]

They are all over downtown Charleston. The engineers and insurance companies properly call them strain gauges. -- kainaw ™ 17:59, 5 April 2008 (UTC)[reply]

Admittedly I only know what I can find on the web, but everybody seems to call them crack gauges, tell-tales or something similar: [3] [4] [5] [6] [7] [8]. There is exactly one example of the name "mechanical strain gauge" being applied to the thing we are talking about, and that's on Wikipedia. Everywhere else, the latter term seems to mean either a linear displacement gauge with a dial or a penis-measuring device. --Heron (talk) 10:28, 6 April 2008 (UTC)[reply]

I would object to calling it a "strain gauge" as 1) that's a well-defined term for an electrical sensor and 2) the gadget in the picture isn't measuring strain; once the object under test cracks, there's no strain left, just a variable displacement.

Atlant (talk) 15:50, 6 April 2008 (UTC)[reply]

They measure strain on a foundation as a crack widens. I have always assumed that is why the insurance paperwork refers to it as a strain gauge. It could simply be that they don't want to use common terminology because legal paperwork is specifically designed to be unreadable for those who aren't "in the know." -- kainaw ™ 23:59, 6 April 2008 (UTC)[reply]

Like I said, once the object under test fails (in this case, the foundation cracks), the strain is no longer defined.

Atlant (talk) 15:48, 7 April 2008 (UTC)[reply]

Calling it a strain gauge is at least a little confusing because there is another device that is more well known as a strain gauge (an electro-mechanical device that measures strain). Any articles on these two different things should make it clear that there is another thing that might go by the same name. ike9898 (talk) 13:38, 8 April 2008 (UTC)[reply]

Sifting flour[edit]

A British recipe for pancake (thin compared to the American variety) calls for me to sift the flour to "air" it. Later, it has me stirring in eggs, milk and water. Is there going to be any of the original air left after all that whisking? Will the air-content of the batter be any different depending on whether or not the flour is sifted? Wont the liquid displace any pockets of air between the flour grains? ----Seans Potato Business 15:41, 5 April 2008 (UTC)[reply]

Sifting of flour is superfluous with modern, high-quality flour stored properly. Originally, sifting was used to get out all kinds of undesirable stuff, and to break up clumps sticking together due to humidity. Just use flour out of the package, unless you like the ritual (it makes a nice, even mound of flour ;-). Be aware that most European flour is plain, i.e. not self-raising. Self-raising flour will make very different pancakes (though they can be nice as well, of course). --Stephan Schulz (talk) 16:43, 5 April 2008 (UTC)[reply]

Sifted flour will be slightly less dense, which matters in the U.S. where people measure out so many "cups" (8 fluid ounces) of flour. It would make little difference in the rest of the world where people measure so many grams of flour. Edison (talk) 19:34, 5 April 2008 (UTC)[reply]

Yes, this is important. See Hausner ratio. If the recipe was written for measuring without sifting and you want to follow the recipe closely, you'll probably match it better by not sifting. Measuring is more important in baking than it is in some other types of cooking, for a variety of reasons. ike9898 (talk) 19:40, 7 April 2008 (UTC)[reply]

Most American flour is also non-self-rising. I think self-rising flour is only common in the South, where it is used for biscuits. -- Coneslayer (talk) 19:36, 5 April 2008 (UTC)[reply]

US biscuits, I assume? Bazza (talk) 14:37, 7 April 2008 (UTC)[reply]

Also, just because flour starts out lump-free at the factory doesn't mean it always stays that way. It could get a few drops of water in it that form lumps (say if the scoop used to get the flour was just washed). Or, even worse, it could have bugs in it (living or dead). I'd rather find this out when sifting than when I bite into one. StuRat (talk) 01:50, 6 April 2008 (UTC)[reply]

A useful pancake tip: If you want light, fluffy pancakes and the recipe calls for water, use seltzer instead. The carbon dioxide in the seltzer will come out of solution and make for lots of tiny gas bubbles in your batter.

Atlant (talk) 15:46, 6 April 2008 (UTC)[reply]

When making British pancakes, light and fluffy isn't really relevant. In fact, adding more air bubbles is just risking holes that will drip lemon juice :) English pancakes are sort of halfway between crepes and American pancakes, which are closer to scotch pancakes or dropscones. 130.88.140.121 (talk) 13:01, 8 April 2008 (UTC)[reply]

Blood vessel cells[edit]

Not a homework question; do the cells of the blood vessels obtain oxygen and nutrients from the blood the vessels are carrying or do the veins and arteries have their own circulatory system as the heart does?--TrogWoolley (talk) 21:34, 5 April 2008 (UTC)[reply]

See Vasa vasorum. --Arcadian (talk) 01:40, 6 April 2008 (UTC)[reply]