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Stupid Science Questions 2

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The Natural Way

12:12 / 11.08.04

So I was having this annoying conversation w/ a friend the other day about non euclidean and euclidean geometries. And we both realized, as so often happens, that we really didn't know what we were talking about. He told me that euclidean shapes, when super-expanded to the size of galaxies, or something, start to "bend about" and the measurements go all wrong, blah. I suggested this was because of gravity and curved space-time. He looked at me blankly. We continued watching the Sopranos.

But was I right?

15:53 / 12.08.04

I'm not sure I understand the question. A shape is a shape -- it doesn't change no matter how big you make it, because it doesn't have a physical reality, as far as I know. A triangle is going to remain a triangle no matter how big you make it. A triangular region of space, though, might do some weird things once expanded, due to gravity and stuff.

I think what you're really asking about is one of those "shape of space/time" questions, to which there's no definitive answer.

By the way, there's another "stupid science questions" thread in here -- I think I'll rename this one to be #2, okay?

18:30 / 13.08.04

How about this:

consider a thin piece of orange peel: to lay it flat on a table we have to squash or tear it: the orange peel has curvature. How could an intelligent insect confined to the orange peel detect this curvature? Well, it could measure the ratio of the circumference of a small circle on the peel to its radius --both measured along the peel. The outcome will be less than 2 x pi: this indicates positive curvature.

A surface is flat or euclidean if the ratio circumference / radius is always 2 x pi. (Confusingly, perhaps, a piece of paper rolled-up into a cylinder like a scroll is euclidean: it can be unrolled flat without stretching or tearing)

There are also surfaces of negative curvature a saddle made of thin material is an example.

Another a way of thinking about it is to consider mapmaking: you can make a distortion-free map if the surface is euclidean. Maps of the Earth always suffer from distortion e.g. Greenland looks huge.

In higher dimensions the situation is similar but more complicated. You need a gadget called the Reimann tensor to capture all the information about curvature. In general relativity the local curvature is determined by the distribution of matter and energy. Higher concentrations of matter/energy lead to greater positive curvature of space-time.

Hope this helps

All Acting Regiment

12:32 / 11.09.04

I've got another damn fool question: can anyone give a list of those really small things, i.e. atoms, protons etc, showing how big they are in relation to eachother? Like, from the smallest up to the largest? I've never got my head round it.

STOATIE LIEKS CHOCOLATE MILK

08:52 / 12.09.04

Apologies if this has been asked before, but can someone explain this.

Okay, I KNOW that if the ice caps melted, the water level would rise. But what I don't understand is why... surely if the majority of ice is below sea level, and ice takes up more volume than water, the opposite would occur? Is it something to do with the water itself being warmer and taking up more space? I'm confused...

10:01 / 13.09.04

Not sure about this myself but -
A floating iceberg displaces its weight in water. When it melts, it is no longer displacing any water (sea level drops) but it has added its weight in water to the sea (sea level rises). There would be no net change in sealevel by melting an iceberg. But, large quantities of antarctic ice are resting on land, not floating. Perhaps it is this ice only that would raise sea levels on melting.
- l

10:58 / 13.09.04

Ok Chris,

Smallest are (until they possibly find something smaller) fermions.

There are two types, quarks and leptons.

There are six different types of quarks. However only two types actually exist in normal conditions in the universe (ie. outside particle accelerators). These are known as 'up' and 'down' quarks. No one knows the exact size of these but there masses are approx. 10e-29kg. Or 0.00000000000000000000000000001kg.

Three of these make up either a proton or a neutron which weigh about 10e-27kg.

Electrons are a type of lepton and weigh about 10e-30kg.

Hope that answers your question.

STOATIE LIEKS CHOCOLATE MILK

17:42 / 13.09.04

quantities of antarctic ice are resting on land, not floating. Perhaps it is this ice only that would raise sea levels on melting

That makes sense. Thank you.

17:46 / 13.09.04

Anybody know whether air compressed into a SCUBA tank (at roughly 3000psi) is in a liquid state or not? I know that such changes have as much to do with temperature as they do with pressure, but never really understood the science behind it.

21:19 / 14.09.04

No, the air in a scuba tank is a gas, just a pressurized one.

In general, increased pressure raises temperature, while cooling a gas would make it a liquid. That said, I'm not sure exactly how they make liquid nitrogen/hydrogen or whatever else. But I've gone diving enough to know it's not a liquid in there.

21:25 / 14.09.04

On the iceberg thing: water expands when in freezes into ice, but that's also the reason why ice cubes float -- more water is trapped in the ice above the water level than the amount that the crystal structure displaces throughout the whole cube; there's more water above than empty space below. In other words, if you put an ice cube in half a glass of water and let it melt, the water level will rise very slightly. The "global catastrophe" from the ice cap melting is just that happening on a very large scale.

09:16 / 15.09.04

Perhaps these guys explain it better than I did.

14:41 / 15.09.04

I think the most important factor in the whole rising sea levels thing is, as Luminocity stated earlier, that an awful lot of the ice rests on solid land. The following is from Wikipedia:
"The Antarctic ice sheet is the largest single mass of ice on Earth. It covers an area of almost 14 million km 2 and contains 30 million km 3 of ice. Around 90 per cent of the fresh water on the Earth's surface is held in the ice sheet, an amount equivalent to 70 m of water in the world's oceans. In East Antarctica the ice sheet rests on a major land mass, but in West Antarctica the bed is in places more than 2500 m below sea level. It would be seabed if the ice sheet were not there."
There is also a big ice sheet resting on greenland, which wshould also be taken into account.

15:46 / 16.09.04

Damn, I was positive there was more water-as-ice above the water level than was being displaced below. Consider me schooled.

Oh, and here's something on the relative size of subatomic particles -- a rough comparison between an atom and the solar system. I know there's a better graphic out there, but I can't find it right now.

16:06 / 16.09.04

While flogging myself over my ignorance, I also came across this Q&A, which indicates that not only is it mainly the ice on land that's a problem with the rising ocean levels, but yeah, also the warmer water will in fact expand. That sounds screwy to me, but I think I need to spend a long time in a hot bath figuring all this out again.

11:10 / 17.09.04

The warming ocean thing applies to the fact that water is at it's greatest density at 4C.

So as the water warms it will expand.

This doesn't really apply to the ice caps melting, just to the overall global warming trend.

15:06 / 20.09.04

"No, the air in a scuba tank is a gas, just a pressurized one.

In general, increased pressure raises temperature, while cooling a gas would make it a liquid. That said, I'm not sure exactly how they make liquid nitrogen/hydrogen or whatever else. But I've gone diving enough to know it's not a liquid in there."

Gas can be made liquid by cooling it, but also by increasing the pressure - the temperature a liquid boils at depends on the pressure, and increasing the pressure increases the boiling point. However all gases have a 'critical temperature' above which they cant be condensed at any pressure.
As for breathing liquids, while its not currently used for diving, trials have been carried out in which animals survived for hours breathing oxygen saturated salt solutions. 'Fluid ventilation' is currently being researched for medical use in humans and clinical trials with 'perflubron' have been conducted. Apparently breathable liquids could potentially be used for diving, which I imagine would feel rather odd.

21:18 / 21.09.04

I recently got hold of a copy of The Particle Odyssey by Close, Marten and Sutton (ISBN 0198609434) which I'm half-way through. It is superb at explaining how the various particles interact, and as long as you can get your head around special relativity (energy is mass and vice versa), it makes a lot of sense. There's something about seeing the pictures that fixes it in your head very nicely. It also helps to read Feynman's QED to understand the reason the wave/particle argument is a bogey.

The resistable rise of Reidcourchie

08:14 / 29.10.04

These maybe some completely elemental questions. Is there such a think as a Blue Star? Is it actually blue in colour? What are it's properties, how is it different from other stars? Does anyone know of any images of what one might look like?

Cheap. Easy. Cruel.

17:12 / 29.10.04

Yes, Reidcourchie, there is such a thing as a blue star. They are called blue giants. A blue giant is a huge, very hot, blue star. It is a post-main sequence star that burns helium. This link has a bit more information.

The resistable rise of Reidcourchie

07:04 / 01.11.04

Cheers cheap much appreciated.

19:33 / 15.11.04

I'm going to bring it down from the galactic to the personal in a question relevant to the gents and a select few highly trained ladies:

When using a urinal, you can either aim for the porcelain, or aim for the water. Which is best for minimizing the mist of urine which is wafting onto you and your clothing? For a while I figured that the water would absorb the force of the urine stream; then it occurred to me that the urine stream into the water might cause the 'kerplunk' effect of a stone hitting the surface. (As a side note, I hear that gaseous planets 'ejaculate' when a meteor hits them; the force of the meteor strike causes a shockwave that knocks a clump of gas out from elsewhere on the planet.)

Our dry cleaners thank you.

12:53 / 16.11.04

I've often think about this whilst drunk for some reason.

I've decided that the best way to reduce "splashidge" is to minimise the angle between stream and the wall of the urinal. So that the pish follows the contour of the urinal. This should redude the reaction force against the porcelin.

Never conducted scientific experiment though...

Nobel prize?

10:23 / 18.11.04

1) Does metal have DNA?

2) Is Pluto officially a planet or not?

Cheap. Easy. Cruel.

13:44 / 18.11.04

Warewullf

No, metal does not have DNA. DNA is a hallmark of living (or once living) tissue. Metal is not, and has never been, living.

Pluto is indeed classified as a planet. Whether or not you think it is, is another matter entirely.

05:39 / 19.11.04

i thought "non-euclidean geography" was something lovecraft made up, until i saw a display on it at the science musuem. doh.

00:09 / 24.11.04

Melting icecaps >

Disclaimer: although my university degree is in geology, I haven't worked in the field in about 6 years.

One other interesting thing to note about large masses of land ice melting is that not only do you have an increase in sea level, but land upon which a large amount of ice was previously resting will experience uplift. There is good evidence that much of the northeastern U.S. has risen more than 200 feet since the end of the last ice age, due to the removal of ice.

The rock of the craton (the continental mass) is made up largely of silicon, potassium, and sodium in what are called the "felsic" (feldspar-rich) minerals. These minerals are substantially lighter than the magnesium- and iron-rich minerals that make up the seafloor and the earth's mantle. As a result, the continents literally float in the semifluid mantle like icebergs in the ocean. If there is sufficient ice added to the landmass, the continental crust will sink a little bit.

The upshot of all of this is that not only will sea level rise if the Antarctic ice melts, but the landmass of Antarctica is likely to rise up several hundred feet to compensate for the reduction in ice weight.

10:05 / 24.11.04

Cheers, Cruel.

The metal/DNA thing came up in, um, a recent Transfomers comic and I knew it was rubbish but self-doubt demanded I double-check before proclaiming it bollocks.

And that whole Pluto debate was raised in a recent episode of QI where Stephen Fry said Pluto was re-classified as a moon (or asteroid). I remember reading that a while ago but thought it was re-re-classfied as a planet because it was too confusing and everyone wanted it to be a planet anyway...

10:51 / 26.11.04

Speaking of planets, why is the Earth hot inside?

09:44 / 27.11.04

Hi guys,
Decimals. You've got 2.54cm's, now when you add anything on the left side of the decimal point you're making that number bigger, right? 20.54 is bigger than 2.54.

But when you add to the far right hand side aren't you stretching the distance between units into infinity?

IE, 2.54, 2.543, 2.5436, 2.54368, 2.543681

And so on?

Doesn't this make going from 0.1cm to 1cm impossible?

Stupid question as I am more than 1cm tall but I thought I'd get this cleared up. Thanks!

11:36 / 27.11.04

Hi triplets,

It seems that your question, while not precisely the same, is very similar to one of zeno's paradoxes - Achilles and the Tortoise. This has been solved.

Modern mathematics states that even when a series of numbers is infinite it can have a finite answer. To fully understand it you would need degree level mathematics but it is simple enough to say that numbers can 'converge' on a value.

So if you add up all the numbers between 0.1 and 1, even though are an infinite number of them, they will 'converge' on 1.

Does that make sense?

14:44 / 27.11.04

On a related note, can you have a square - even a theoretical one - that has an area of 3 precisely? If so, how long is one side? Is it just unmeasurable, or is it impossible?

16:41 / 27.11.04

Yes, I think it does.

If you add up a certain amount of numbers between 0.1 and 1 starting at 0.1 then eventually you'll get to one, ie:

0.1 + 0.11 = 0.21
+ 0.111 = 0.321
+ 0.1111 = 0.4321
+ 0.11111 = 0.54321
+ 0.111111 = 0.654321
+ 0.1111111 = 0.7654321
+ 0.11111111 = 0.87654321
+ 0.111111111 = 0.987654321
+ 0.111111111 = 01.987654321

Is that anywhere near right?

02:09 / 28.11.04

Okay, I've just thought of this after coming home pissed and making pasta...

If we consider the universe as an ever-expanding bubble, expanding at light-speed wouldn't that make my expanding decimal thingy true?

Think about it. If we consider the Big Band point, the singular point, as 0.1 and the edge of the universe as 1 then there is an infinite distance between the two as we can never reach it, right? How does THAT fit in?

16:25 / 28.11.04

On a related note, can you have a square - even a theoretical one - that has an area of 3 precisely? If so, how long is one side?

The smug answer is "the square root of 3".

Is it just unmeasurable, or is it impossible?

I would answer that question by dodging it. The careful answer would say that, given any measuring equipment and construction method, you can make a square that is as close to having sides the square root of 3 as the equipment allows. But since you can't measure any better than your equipment, this is as close to "exact" as you can get.

The ultra smug answer is to say, take any square and define a set of units so that it has area 3. You now have a problem about whether you can construct a square of area 1 in those units...

If we consider the universe as an ever-expanding bubble, expanding at light-speed wouldn't that make my expanding decimal thingy true?

You can certainly have limits that approach yet don't reach a certain number. Just as you can have a cruise control that never lets you go over 40mph. But I'm not sure the first tells you anything about decimals approaching 1 any more than the second tells you about the number 40. But I think Atyeo has it right that you sound like you want to muck about with Zeno's paradox(es).

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