Easy Questions?

[Aggie]

They all end like biscuits in Calgary, as does ANYTHING left out (fruit in our apartment dries before it ripens).
I've been sending a couple of gallons of water through the humidifier lately (for the benefit of the houseplants), and never even get a trace of condensation forming on the windows.  It is DRY here, and horrid for the skin in winter.


What's more curious is why they don't just make biscuits out of cake in the first place to avoid this.

[Sibling Spoffish]

If I was explaining the first and third to a young child, I would do it like this - assuming that they knew that the earth, sun, and moon are all round.

If the sun was a beach ball, the earth would only be a marble - that's how big the sun is. It looks smaller because it's further away, like a tree in the distance looks really little.

If the earth is a marble, then the moon is like a tiny bead, or a teeny ball of blue-tack (whichever is handier).

The earth, the marble, goes around the sun. It takes one year for the sun to go all the way round.

The moon, the bead/blue-tack, goes around the earth. It takes about a month for the moon to go all the way around.

All the time, the earth is spinning. Each time it spins is one day and one night. The day is when we're facing towards the sun, so the light can shine on it, and the night is when we're on the other side, so the rest of the earth blocks the light.

You can see that the moon is always closer than the sun.

Demonstration is the best way, in my opinion.

[Bob in a quantum-state-of-faith]

Actually, for a 20-inch beach ball (50cm) you'd need a 1/10-inch earth - about the size of a green pea.  The marble is usually about 1/2-inch, too big.  Make an acceptable Uranus or Neptune.  A 1-inch marble would make an acceptable Jupiter.

As for the moon, a very small pin-head would work I suppose.

Here's a cool Java site with a scale-size calculator http://www.exploratorium.edu/ronh/solar_system/

Now, if you're talking ORBITS, it gets even more interesting.  Take a 1-inch marble (Sun), and the orbit of the earth would be almost 9 feet, and the diameter of the earth would only be 2 tenths of a millimeter, or about a hundredth of an inch. (remember: the average orbit of the Earth is 93 million miles)

If you keep that 20 inch sun, the Earth's orbit goes out to nearly 180 feet, or more than 1/2 of a foot-ball field (which is 300 feet).  To keep it in perspective, that puts Neptune at more than a mile away, and Pluto about 1 and 1/2 miles from the 20 inch sun.  (No wonder Pluto is so cold )

And while on the subject of scale, there is a VERY cool demonstrator of scale - it is a little animation that goes from the nucleus of an atom to an overview of the universe.  I first saw this as a film in the Smithsonian museum, when I was a teenager.  http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html

[Swatopluk]

One should not underestimate the lack of knowledge/understanding even in adults (what an elitist statement ). There are quite many people who cannot believe that a solar eclipse always happens at new moon. Their "common sense logic" tells them that a moon "that is not there" cannot eclipse the sun, therefore solar eclipses naturally occur only at full moon.

Concerning the cake and biscuit question
Clearly depends on the type. One thing is clear: there is a dynamic exchange between the atmosphere (gas with "dissolved" water) and the solid object. The cake could be seen as a sponge that already holds water while the biscuit is more like a dry sponge.
The atmosphere being big will have a more or less constant humidity (let's ignore the weather for a moment) while in the wrapping of the eatables there is not much air, i.e. only a fixed small amount of water. In the wrappers there will be an equilibrium between water in the eatable thing and the surroundings. In the open air a dry good will suck water from the surroundings until there is again an equilibrium. If on the other hand you have a humid good the not saturated air (unlimited capacity) will suck the water out until there is either an equilibrium or there is no accessible water left. Goods will dry often at the surface only because the water at the center cannot easily come to the outside (and the other way around in dry food, soggy on the outside but still dry inside).
That food gets soggy in the fridge is slightly different. Cold air can hold less water than hot air. The fridge permanently exchanges the air inside itself. The air from outside is cooled down and will lose some of its water content that will end either as condensation or will be sucked up by food stored in the fridge. In the oven you have the opposite effect. The hot air can hold more water and will suck it from the baking goods.
I have to admit that there are a lot of aspects concerning this that I do not completely understand. There is probably another effect of water tightly and loosely bound in the food. We will not notice it in the former case but if by some effect the tightly bound water becomes loose we will.
A nice experiment demonstrating something similar can be carried out at home too.
Get some copper sulphate. It is blue and apparently dry. Now heat it ( a gas stove would be best) and it will turn colorless/white. If you keep it under dry conditions it will stay that way but under humid conditions it will turn blue again without seemingly getting wet (at first). If you have precise scales you can show that the blue dry salt is slightly heavier than the white dry salt. In the blue version the water is bound so tightly that it cannot be detected.

[Bob in a quantum-state-of-faith]

There are other chemicals besides copper sulfate.  Silica gel crystals behave in much the same way.  You'll often find them in those "do not eat" packets that look like 1/2 size sugar packets--you'll often find these in foods that need to stay very dry.  Electronics products often have them as well.

A nice source for a lot of the silica gel crystals is that new cat litter. 

What many people do not realize, is that you can re-activate the crystals with heat.  Get the silica gel crystals hot enough (300+ degrees F) and the water will be driven off.  There is not a color change, unlike the copper sulfate.

(If one had access to a suitable oven, one could get away with purchase of only 1 bag of the kitty litter - it's pricey, when compared to clay litters - and whenever it becomes saturated, simply bake in an oven for an hour to renew.  Likely you'd want enough for 2 changes - one to be baking, and one to be in use.  Store the just-baked batch in an airtight container, so as to minimize absorption of atmosphere water.)

If I remember my chemistry right, the water that is bound in the copper sulphate or silica gel, is held by what is called "loosely bound".  That is, it IS a chemical bond, as opposed to simply dissolved in solution or held by surface-tension as you'd see in a sponge.

This "loose" chemical bond is easily broken by the application of heat.

Isn't science fun? :O

[Swatopluk]

It's called the complex binding (also very complex in detail with bonds inside the molecule weakened to allow for the outside binding to the metal that then creates a back-binding. Enough to torture chemistry students for half a year with). I chose the copper salt because of the color change. Silica gel itself has no visible change but is often dyed with cobalt salts that have a blue to pink transition.
Apart from water ammonia is a common complex ligand. A faintly blue-green copper salt solution in water will for example turn dark blue after addition of ammonia.


Next question: Why is there thunder after a lightning strikes? It's not that clouds should make sounds when crashing (otherwise we would hear it when a plane goes through the clouds). The story about the big guy with the hammer looks a bit fishy.

[Sibling Chatty]

Air rushing into the vacuum caused by the lightning.

The charge of the strike leaves an "airless tunnel" that is refilled by the air around it, and it rumbles as it rushes into the vacuum.

[The Black Spot]

If camera lenses are round, why do the pictures come out square?

[Sibling Chatty]

Because film is a strip, not a circle, silly. And not all lenses are round.

Besides, the lens thingy is to capture the light so the imps can see to paint the picture!!

[Swatopluk]

Back to the thunder. The lightning looks so thin. Why can the air filling that tiny bit of vacuum make such a deafening noise?

[That's not disputing the answer, just the counterquestion to be expected]

Additionally: An electric arc/discharge is audible with a typical "electric sound". Why doesn't the lightning sound like that?


Another tricky one: Why does the mirror switch left and right but not up and down?

----
Chatty,
But don't say "Heckuva job, Brownie!" to your camera

[The Meromorph]

Another tricky one: Why does the mirror switch left and right but not up and down?

It doesn't switch either.
It switches front to back!
Your head is still in the same position, your right hand is still in the same position. But your image is reversed front-to-back.
Since your mind has to interpret somehow, and it 'understands' that people can turn around, but not that they can be 'reversed', then it interprets a 'reversed person as being switched from left-to-right. (The true front-to-back reversed 'doesn't make sense' because the 'turned around' is so 'obviously' the answer.)

[Sibling Lambicus the Toluous]

The "sinking ship" method has one disadvantage. It could be that the light has a tendency to either follow the surface or be drawn away from it, i.e. the rays of light could be curved slightly instead of being straight lines. Of course it is possible to disprove it but some effort would be needed.

And to complicate things even more, radio waves do tend to curve over water (especially salt water) to follow the surface, and they're part of the EM spectrum just like light.   

[Swatopluk]

Another possible answer to the mirror question (Quasi-Mero is of course right, eh left, eh... whatever )would be that left/right are relative to the viewer and the "person on the other side of the mirror" is falsely seen as another viewer while the other directions can be absolutely described. I have read that only the indogermanic group of languages uses that subjective perspective while others use absolute coordinates.
What would we do, if our eyes were not side by side but above each other. Would the concept of left/right still make sense (let's ignore our asymmetric inner organd for a moment).


If the tides are caused by the moon pulling why is there flood tide on the opposite side of the Earth also? And is it the moon pulling the water or does the Earth slightly change its form and the water follows the way of least resistance? [Ignore breaking/reflecting effects on coasts, that is still beyond complete mathematical modelling]

And while we are at the moon again, why do we always see the same side of it while from the moon we can see the whole earth turning in front of use once about every 24 hours?

[Bob in a quantum-state-of-faith]

I don't remember the tide-answer, I used to know. (old age--*sigh*)

As for the moon's face, that one I do know.

In any two-body gravitational system, each object is free to rotate on an axis within the system.

That is, as the moon circles (elipsis? it's not a true circle, actually.  ) the earth, it also rotates about it's axis.  As does the earth.

As it turns out, the axis of each is roughly in the same direction (unlike the planet Neptune, which lies on it's side). 

The earth rotates once every 24 hours (roughly-- there's a tiny fraction of difference). 

The moon rotates once every 28 days.  As it turns out, this corresponds to a complete "lunar year" or revolution of the moon in the circular path around the earth.

Thus as the moon moves about the earth in it's orbit, it ALSO rotates at a rate that ensures the same face points to the earth.

Why this is so, is still a mystery. But there are a number of pretty theories to explain it.  I'll leave the research to discover these theories as an exercise for the student. 

[Swatopluk]

Calculation show that he tides slow down the rotation of the Earth and that one day Earth and moon would face each other with the same side permanently. To keep the angular momentum balance the moon would then be much farther from the Earth. This will actually not happen because the sun will go Red Giant long before and either swallow the Earth directly or having it tumble into it on a spiral.

What a pity for werewolves. They could either follow their inner predator by settling in the permanent full moon regions or avoid it by living somewhere else.

We'll talk about the tide effect later.