The Ultimate Thermometer

The substance, water, without which life would be impossible, has been used to measure all temperatures, in effect.

When science, serious science began, it was realised that some sort of temperature scale would be necessary. Mr Faranheit came along with an arbitrary system. Then Mr Celsius saw common sense and invented another system, first calling it "Centigrade" before being modified to "Celsius".

He defined it very simply; with water.

"At normal temperature and pressure, let pure melting ice be zero Centigrade, and pure boiling water be one hundred Centigrade."

Just to make things easy. To convert from one to the other was fairly easy:

Celsius to Fahrenheit (°C × 9/5) + 32 = °F
Fahrenheit to Celsius (°F - 32) x 5/9 = °C

Or, in words,

°F to °C Deduct 32, then multiply by 5, then divide by 9
°C to °F Multiply by 9, then divide by 5, then add 32

Most Americans use Deg F (except for the scientists), whilst almost everyone else uses Deg C (because Celsius is the Universal unit of temperature as adopted by the Scientific Community - it is simpler).

One may have noticed that in the definition of zero and one hundred Celsius, zero is not simply "ice", nor is one hundred simply "steam".

There is a very good reason for this. Thermodynamics again. If you take a block of ice and heat it, it's temperature goes up like this:



There are five bits to it: three sloping bits and two flat bits. The sloping bits are easy. Over time, as more heat gets put into the substance, the temperature rises, the first slope is the temperature of ice rising, the second slope, that of water, the third, that of steam, as more and more heat is supplied.

But what about the flat bits? This is the interesting part. The flat parts of the graph are where the temperature stays constant because all the heat (therefore energy) is used in breaking chemical bonds, the first flat bit from ice to water (solid to liquid), the second flat bit from water to steam (liquid to gas).

Celsius used this simple fact to define his fixed points, the two flat bits, where the temperature is always the same.

So, if you want something to be cooled to EXACTLY zero degrees Celsius, stick it in a bag of MELTING ice, or if you want something to be EXACTLY 100, put it into a container of boiling water.

That is why water could be called "The Ultimate Thermometer"

( It is quite clear that the bigger the sample of ice, the more heat you have to put in to break the two types of chemical bonds. There is a measure for this was well, it is called "Specific Heat Capacity", but that is another story. )

Closure

There was some confusion about my last post.

Some clarification is needed.

In thermodynamics, a "closed system" means energy can neither enter or leave. To talk about the universe as a "closed" thermodynamic system may not have any meaning, as nothing exists "outside" it, as there is no "outside".

In Cosmology, because of the expansion of the Universe, it has been speculated that the Universe falls into one of three categories: Open, Closed or Flat.

This is a gravitational consideration, and has nothing to do with thermodynamics.

The question involves the amount of matter in the Universe. Is gravity enough to stop the expansion? If it is, the expansion will stop, and a contraction will ensue, resulting in a "Big Crunch", or "GnabGib". This is a closed Universe.

As opposed to an Open Universe, in which the expansion continues forever.

AND a Flat Universe where gravity is just enough to halt the expansion only.

Trusting that Closure has been reached....

The Laws of Conversation

Whoops, lo siento mucho - I mean conservation

In physics there are many conservation laws. But what does that actually mean?
It is best illustrated by an example, and the one most people feel comfortable with is The Conservation of Energy.

This "Conservation of Energy" means that energy can neither be created nor destroyed, just converted from one form to another. It is an expression of the first Law of Thermodynamics.

In any physical process, the total amount of energy IN A CLOSED SYSTEM is constant and never changes. Closed systems mean that in the action studied, no energy is let in or out through some predetermined boundaries.

For some "closed systems" it is easy to understand this concept. Take for example, making a cup of tea. Into a closed room, take a recently boiled kettle, a cup, a teaspoon of sugar and a jug of milk. From outside the room, via robotic arms, you put some sugar and milk into the cup, with a teabag. Then you pour the near-boiling water into the cup and stir it.

Tea up! What has just happened? Well, the heat (energy) from the water has heated the cup, milk and tea. The hot water brings the flavor from the tea, dissolves the sugar, and the temperature of the cup of tea is now less than the initial water.

If a calculation is made (it's pretty simple) of all the energy before pouring, and after the tea has been brewed, the temperature of the milk has gone up, and the temperature of the water that made the tea, gone down, a similar measurement is made, there will have been no change. If the amount (mass) of each is taken into account (not to mention the energy released by the melted sugar), the amount of energy available before, is the same (exactly) as after.

If you think this was complicated, Consider the energy changes if the tea is made on a one meter table, then the full cup dropped to the floor to shatter. There are at least eight energy changes. Can you name them? In order?

Not only energy is conserved, either.

Momentum is mass x velocity, that is conserved also.
Electric charge is conserved.
Angular momentum ( r x p, when p is momentum, and r is the distance from the rotation point. However, the "x" is not a multiplication sign, but the "cross product" of two vectors)is also conserved.
Color charge is also conserved.

..and the somewhat esoterically sounding, "weak isospin" is also conserved.

There are other quantities conserved, but only under certain conditions.

The "Discovery" of Absolute Zero

This is a chart to show what happens when we chill out. More specifically, what happens to a gas.

Everyone knows what happens when it gets cold.....things SHRINK (men would know more about this).

It has to do with vibration (don't get excited, girls).

Heat = energy and the less heat an object has, the less it's vibration.

So the size decreases.

If you are talking gas (Ethel Merman go home) then for the same amount of gas, if you cool it, the container you need to keep it in will have to be smaller.

There was once a guy named Charles, who figured this out, but he did not stop there.
He said to himself, what if, the gas did not go to a liquid, bur instead stayed as a gas? He called it an "Ideal Gas".

The buckshot (whoops, Upshot) was that he continued the picture right back to zero volume ( as per the picture) and he found out that no matter WHAT gas was used, they all ended up at zero volume at EXACTLY the same "temperature".

It was from then on called "Absolute Zero". and the number is 273.16 degrees Celsius below the freezing point of water.

Nothing has ever been cooled further since.

This whole issue is couched in quantum mechanics, although at the time, it wasn't even thought of. The reason why quantum mechanics comes into it is down to Heisenberg again - the Uncertainly Principle. If something stops moving, then you can say where it is (Trivial, I know, but hang on). This is completely forbidden by quantum mechanics. Moving targets are a must!

So stuff need to keep moving. and if you are at absolute zero, you stop. Therefore, you cannot get there (thermodynamics again).

Physics is wonderful because basically all the stuff around us is related to everything else. It's only when you study really hard do you get to know (and wonder at) how it all fits together.

This is the be-all and end-all of why the subject is so dear to me. You can call me a "bore" but at least I know the answers to the questions we have all asked our parents as kids.

Water, or di-hydrogen oxide, is the strangest of all, and blatantly refuses to conform....!

Why does ice float?

More Heat from the Arrow of Time

Continuing the theme of "Heat" and "Energy" led to a startling conclusion.

So we have three laws of Thermodynamics. All sorts of concepts have sprung out of this field, such as "Statistical Mechanics", "Carnot Cyles", "Heat Efficiency", and "Ideal Heat Enchangers".

However, the most infulential was the concept of "Entropy".

Simply put, Entropy is the measure of how disorderly a system is. The more disorderly, the more entropy. For example, a teacup falls to the floor and smashes. It falls apart but gains a lot more entropy because it is far more disoredered after the smash.

More accurately, we say "system" has gained entropy, the "system" being the cup PLUS the floor.

All this is intricately connected with thermodynamics, and is one of the central tenets of the field. Recall the three Laws of thermodynamics, cynics' version:

Law 1: "You cannot make a profit, only break even"
Law 2: "You can only break even if banking is free"
Law 3; "The bank is always closed"

Taken all together , they simply state that "you can never break even". the translation of this into real physics means that, in any process whatsoever, ANY process, there will always be heat loss, and that no "system" is 100% efficient.

Thought of this way, it actually means that a perpetual motion motion machine is not only impossible, it is forbidden even in principle.

However, this ia a digression to say the least, if not less.

The whole entropy thing hangs completely on the second law, which can be "translated" into yet another statement:

"The change in entropy in any system is always greater than zero"

In scientific parlance,

" dS > 0 "

where "S" is entropy and the little "d" is the universal scientific symbol for "change".

Bear this in mind, because it has as a far deeper significance than at first meets the eye.

For now, though, consider physics in general. All physics is governed by laws, and those laws are expressed through mathematical formulae. Formulae are made up of letters, symbols and numbers, and usually some are quite familiar. "x", for instance, can be a number representing a distance, a volume, etc. Capital "t", or T, is usually "Temperature" and capital "p", or P is usually Pressure. "q" is usually electric charge, and E usually Electric field (sometimes it is Energy, too).

A lot of these "variables have "direction", too. For instance going North is the opposite of going South, so we call them "x" and "-x" (it does not matter which). We all know that electric charge is either positive of negative, so we write "q" or "-q" depending on whether the charge is positive or negative.

However, we can't write "T and "-T" simply because the equations won't allow it (yes, I know you can have negative temperature in life, such as liquid nitrogen boils at -196 deg C, but that is a consequence of the arbitrary scale, namely the Celsius scale).In the physics world, all temperatures start at absolute zero so it does not make any sense to have a negative temperature. More easy to understand is pressure - you most definitely cannot have a negative pressure.

The point is this: The equations sometimes don't care if the thing has a positive or negative sign. When you plug in the values and turn the handle, the answers always come out the same even if some things have a minus sign in front of them. Time, "t" is one of them. That is, the equations don't care if you put a "-t" instead of every "t" because the answers are always the same.

You can run the equations backwards in time and the numbers don't care!

Time has no "arrow"!

Here's the rub: The second law of thermodynamics contradicts this!

For example, take the smashed cup. No way in the Universe do you ever see the cup reassemble itself and jump back into your hand, do you, complete with anti-smashing sound?!

Time DOES have an "arrow"!

Which is correct? They can't BOTH be right!

How Many Laws Are There To Describe Heat?

Now that energy has been dealt with, there now follows the Scientific Equivalent of "What Happened Next....".

In other words, the detailed study of the way heat, or energy, behaved. This was branch of science was called "Thermodynamics" and was defined as the way "heat" (the "thermo" bit) "moved" (the "dynamics" bit).

There were found to be three laws. However, there was more than one way of stating them. The most common was :

1st Law of Thermodynamics: "In a perfectly insulated system, heat is neither lost nor created. "

2nd Law of Thermodynamics: "Perfectly insulated systems only exist at Absolute Zero of temperature. "

3rd Law of Thermodynamics: "Absolute Zero of temperature can never be attained. "

where the term "system" means an isolated bunch of things, such as a kitchen, or a bathroom.

The first Law is simply another way of stating the Conservation of Energy.
The second and third Laws together say 100% efficiency is impossible.

In other words, heat or energy can be freely exchanged but there will always be some unwanted heat produced.

Cynical scientists translate them this way:

Law 1: "You cannot make a profit, only break even"
Law 2: "You can only break even if banking is free"
Law 3; "The bank is always closed"

There's more.....after these three Laws were formulated and called Laws 1, 2 and 3, the scientists realised they had left out an even more fundamental truth than the conservation of energy. It was this:

"If two things have the same temperature as a third, they are at the same temperature as each other."

This was promptly recognised as the REAL first Law, but since they had already been named, it was put before the first Law. What do you call the number before one? Zero, of course.

It was called "The Zeroth Law of Thermodynamics" and officially runs like this....

"If two bodies are both in equilibrium with a third, they are also in equilibrium with each other".

Just how gullible ARE you people? ROTFL!!!!