Answer to skunk's question

[Bartman10]

If it's 0 degrees today, and it's going to be twice as cold tomorrow, how cold will it be?

Do you mean half as hot? Temperature is measured in degrees of heat. Do you mean degrees C or degrees F? Because the final number will be quite different:

In degrees C half of zero is -136.575 degrees C
In degrees F half of zero is -213.835 Degrees F

Most of you will think whatever :whocares: but I make it my job to inform people about temperature.

Temperature is a measure of molecular agitation. In gasses it is expressed through the pressure of the gas. In solids it is expressed in a variety of ways, including the radiation of electromagnetic rays and in the voltage change across a piece of wire, or the bandwidth of electrical noise generated in a piece of wire.

The temperature scale that is most widely used is the ITS-90 scale which is actually based on the freezing points of different metals, for example zinc has a defined melting point of 419.527 degrees C, and aluminium has a defined melting point of 660.323 degrees C etc. The ITS-90 scale is not a natural scale, and there are small errors in it. If skunk hadn’t asked about half of zero, then the answer above would have had a slight error due to differences in the ITS-90 and thermodynamic temperature scales. Lucky that 0 is (almost) defined on the both ITS-90 and thermodynamic scales.

Well class today’s take home message is: A thermometer measures its own temperature. If your thermometer is not in thermal equilibrium with its surroundings you will not measure what you think you’re measuring.

To find out more about temperature and temperature measurement email me or check out www.irl.cri.nz/msl

[ZorsT]

since 23degrees is good, it will be minus 23 :devil2:

[Virago]

If it's 0 degrees today, and it's going to be twice as cold tomorrow, how cold will it be?
Okay, "twice as cold" must equal "half as hot".

Absolute zero is approx -273 C from memory, so "half as hot" must be -136.5 C.

There's your answer! :yes:

[Bartman10]

Okay, "twice as cold" must equal "half as hot".

Absolute zero is approx -273 C from memory, so "half as hot" must be -136.5 C.

There's your answer! :yes:

Striaght to the top of the class.

Something went hideously wrong before I'd finished and the post got posted prematurely incase you're wondering about the sudden increase in lecture material for today!

[Hitcher]

Talk about over-complicating an answer!

To answer Skunk's question, one needs to know nothing about physics or chemistry. Mathematics will give you the answer you seek.

For example: If it is 0 degrees celsius today when normally it is 14 degrees, if it is to be twice as cold tomorrow, then the temperature will be minus 28 degrees.

However rather than being pedantically literal, Skunk was probably using a couple of figures of speech: one called exaggeration and the other called irony. And, I suspect, the two were entwined in a rhetorical question.

[mini_me]

Striaght to the top of the class.

Something went hideously wrong before I'd finished and the post got posted prematurely incase you're wondering about the sudden increase in lecture material for today!

haha, you had me totally lost for a moment there

[Drew]

I reackon the Hitch man is right, it was rhetorical, and I have gone cross eyed trying to keep up with what you guys said, tahkns ervy umch!

[WINJA]

Talk about over-complicating an answer!

To answer Skunk's question, one needs to know nothing about physics or chemistry. Mathematics will give you the answer you seek.

For example: If it is 0 degrees celsius today when normally it is 14 degrees, if it is to be twice as cold tomorrow, then the temperature will be minus 28 degrees.

However rather than being pedantically literal, Skunk was probably using a couple of figures of speech: one called exaggeration and the other called irony. And, I suspect, the two were entwined in a rhetorical question.
THAT MAKES NO SENSE , WHEN US PROS DO CALCS WE USE ABSOLUTES AND KELVIN

[Bartman10]

Talk about over-complicating an answer!
For example: If it is 0 degrees celsius today when normally it is 14 degrees, if it is to be twice as cold tomorrow, then the temperature will be minus 28 degrees.

Where did you get 14 degrees C from. Whats 14 degrees C got to do with anything? He asked what half of zero was.

I'm confused by your example, twice as cold as what? Maybe you could reword it.

You can add to the Celsius scale but you can't multiply it. Celsius is not a metric scale. It’s meaningless to talk about fractions of the Celsius scale unless you convert to Kelvin first, do your multiplication and go back to Celsius. Half of 14 Celsius is –129.575 Celsius. –28 has got nothing to do with it.

[WINJA]

I reackon the Hitch man is right, it was rhetorical, and I have gone cross eyed trying to keep up with what you guys said, tahkns ervy umch!
ITS NOT THAT HARD -273 DEGC IS ABSOLUTE ZERO OR ZERO KELVIN, ITS AS COLD AS COLD CAN BE , I DONT THINK ITS BEEN COMPLETELY ACHIEVED BUT WE CAN GET CLOSE USING A CASCADE REFRIGERATION SYSTEM USING HELIUM/NITROGEN/CO2/404A OR R502 AND ME TO BUILD IT FOR YOU
EDIT

[Drew]

THAT MAKES NO SENSE , WHEN US PROS DO CALCS WE USE ABSOLUTES AND KELVIN
Yeah, but who the fuck talks like that in the real world? And calculas, is theorised on an ideal invironment, the real world has too many variables to be measured.

[Hitcher]

THAT MAKES NO SENSE , WHEN US PROS DO CALCS WE USE ABSOLUTES AND KELVIN
I'm sorry about that. Lets say then that today's temperature is is 273.15 degrees Kelvin, when normally it is 287.15 degrees. If it was to be twice as cold tomorrow, it would be 245.15 degrees. I hope that makes more sense for you pros.

[Drew]

Where did you get 14 degrees C from. Whats 14 degrees C got to do with anything? He asked what half of zero was.

I'm confused by your example, twice as cold as what? Maybe you could reword it.

You can add to the Celsius scale but you can't multiply it. Celsius is not a metric scale. It’s meaningless to talk about fractions of the Celsius scale unless you convert to Kelvin first, do your multiplication and go back to Celsius. Half of 14 Celsius is –129.575 Celsius. –28 has got nothing to do with it.
Re-read the question, it says how cold will it be. Even in the ice age, the air temperature didn't get to anywhere near -136. So that is obviously not the answer to the question.

[Hitcher]

Where did you get 14 degrees C from. Whats 14 degrees C got to do with anything? He asked what half of zero was.
No, he said that it was zero degrees today and would be twice as cold tomorrow. He was talking about comparative temperature difference.

14 degrees was my presumed average midday ambient temperature for July.

[Hitcher]

Here's another question for you professional scientists:

The Interisland ferry Awatere is lying at anchor in Wellington harbour. It has a rope ladder hanging down one side. The rungs are made of steel. The ladder has rungs spaced at 0.25m intervals. There are 80 rungs on the ladder above the waterline. It is currently low tide in Wellington harbour. The difference between the high and low tides tonight will be 3.28m. How many rungs on the ladder will be exposed at high tide?

[WINJA]

Here's another question for you professional scientists:

The Interisland ferry Awatere is lying at anchor in Wellington harbour. It has a rope ladder hanging down one side. The rungs are made of steel. The ladder has rungs spaced at 0.25m intervals. There are 80 rungs on the ladder above the waterline. It is currently low tide in Wellington harbour. The difference between the high and low tides tonight will be 3.28m. How many rungs on the ladder will be exposed at high tide?
WHO CARES :whocares:

[Hitcher]

WHO CARES :whocares:
But you said you were a PRO?

[WINJA]

But you said you were a PRO?
IM NOT A MATHMATICIAN, YOU GUYS WERE JUST TALKING ABOUT A SUBJECT I DEAL WITH EVERYDAY. YOULL HAVE TO ASK INDY ABOUT BOATS, ROPES AND BABY OIL

[Hitcher]

IM NOT A MATHMATICIAN, YOU GUYS WERE JUST TALKING ABOUT A SUBJECT I DEAL WITH EVERYDAY. YOULL HAVE TO ASK INDY ABOUT BOATS, ROPES AND BABY OIL
So you're really Jim Hickey?

[WINJA]

So you're really Jim Hickey?
NO , BUT SURELY THE SAME RUNG WILL BE IN THE SAME PLACE UNLESS THEIR LOADING THE BOAT OR THE MOORINGS HOLD IT DOWN

[Bartman10]

ITS NOT THAT HARD -273 DEGC IS ABSOLUTE ZERO OR ZERO KELVIN, ITS AS COLD AS COLD CAN BE , I DONT THINK ITS BEEN COMPLETELY ACHIEVED BUT WE CAN GET CLOSE USING A CASCADE REFRIGERATION SYSTEM USING HELIUM/NITROGEN/CO2/404A OR R502 AND ME TO BUILD IT FOR YOU
EDIT

Quite right WINJA. You can't get to zero Kelvin (NOT degrees Kelvin). Say you had some beers and you wanted to cool them. Whaddya do? Stick em in the fridge of course. Now here's the crunch - the fridge is colder than the beer right - so to cool something you need something colder. In the case of the beer it's the fridge, in the case of the fridge it's the expanding CFC's that come out of the compressor. In the case of the expanding gas it's random molecular motion (THE MEASURE OF TEMPERATURE) being changed into directed molecular motion. Think about the "you need something colder" principle for a while and then tell me if it's possible to even get to zero Kelvin.

[Big Dave]

Here's another question for you professional scientists:

The Interisland ferry Awatere is lying at anchor in Wellington harbour. It has a rope ladder hanging down one side. The rungs are made of steel. The ladder has rungs spaced at 0.25m intervals. There are 80 rungs on the ladder above the waterline. It is currently low tide in Wellington harbour. The difference between the high and low tides tonight will be 3.28m. How many rungs on the ladder will be exposed at high tide?


The same - the boat goes up and down with the tide.

[Ixion]

Mr Hitcher is right. The key is the statement "twice as cold". Twice as , compared to what. Unless we know that the statement is meaningless. However , when people say such things, they normally "twice as cold AS NORMAL, or as AVERAGE".

So if normal, or average, is about 22 degrees Celcius, then the comparison is 0 to 22 today, or -22 to 22 tomorrow.

[Bartman10]

Mr Hitcher is right. The key is the statement "twice as cold". Twice as , compared to what. Unless we know that the statement is meaningless. However , when people say such things, they normally "twice as cold AS NORMAL, or as AVERAGE".

So if normal, or average, is about 22 degrees Celcius, then the comparison is 0 to 22 today, or -22 to 22 tomorrow.

NO! Get it out of your head that Celsius is a metric scale. It's not. What you're saying is equivilent to saying that the guy who rides number 46 in the motogp is only half as good as the guy that rides number 92. You can't infer fractions of temperature from the Celsius scale, just like you can't infer the quality of motogp riders by their numbers. Twice as cold as your "normal" is -125.575 degrees Celsius.

Where can I get a bike with 92 on the front?

[riffer]

Here's another question for you professional scientists:

The Interisland ferry Awatere is lying at anchor in Wellington harbour. It has a rope ladder hanging down one side. The rungs are made of steel. The ladder has rungs spaced at 0.25m intervals. There are 80 rungs on the ladder above the waterline. It is currently low tide in Wellington harbour. The difference between the high and low tides tonight will be 3.28m. How many rungs on the ladder will be exposed at high tide?

Are we to assume that the Awatere is still capable of floating? In which case there will be 80 rungs. :whistle:

edit: damn - didn't check the second page of posts. It's already been answered.

And a question - if absolute zero can never be reached, how can we be sure that its as cold as it can get?

[WINJA]

it's the expanding CFC's that come out of the compressor. In the case of the expanding gas it's random molecular motion
I THINK YOU MEAN SUBCOOLED LIQUID COMING OUT OF THE RECEIVER OR CONDENSOR, SUPERHEATED VAPOUR COMES OUT OF THE COMPRESSOR

[Virago]

.........if absolute zero can never be reached, how can we be sure that its as cold as it can get?
When Mrs VV comes to bed tonight and puts her cold feet on me, I can assure you that absolute zero can be reached, and even surpassed.

But hey, good question. Also, if the speed of light cannot be reached, how do we know nothing can travel faster (with the possible exception of bad news)?

[Hitcher]

NO! Get it out of your head that Celsius is a metric scale. It's not.
Of course it's a "metric" scale!

One degree on the Kelvin scale is exactly the same as one degree on the Celsius scale. The only difference is that 0 degrees Celsius is the mean freezing point of water at sea level, whereas 0 degrees Kelvin is an extrapolation to "absolute zero", currently estimated as -273.15 Celsius.

[WINJA]

When Mrs VV comes to bed tonight and puts her cold feet on me, I can assure you that absolute zero can be reached, and even surpassed.

But hey, good question. Also, if the speed of light cannot be reached, how do we know nothing can travel faster (with the possible exception of bad news)?
AT SCHOOL I BROKE THE SOUND BARRIER WHEN SOMEONE SAID THEY WERE GIVING AWAY PIES AT THE TUCK SHOP

[Hitcher]

AT SCHOOL I BROKE THE SOUND BARRIER WHEN SOMEONE SAID THEY WERE GIVING AWAY PIES AT THE TUCK SHOP
I seem to recall reading something somewhere about that particular fart.

[Ixion]

Of course it's a "metric" scale!

One degree on the Kelvin scale is exactly the same as one degree on the Celsius scale. The only difference is that 0 degrees Celsius is the mean freezing point of water at sea level, whereas 0 degrees Kelvin is an extrapolation to "absolute zero", currently estimated as -273.15 Celsius.

I'm with Mr Hitcher. Doesn't matter what scale you use. Use celsius, my "normal" is 22 . Today is 0, that's 22 degrees of "cold". Tomorrow will be "twice as cold" , 44 deg. of cold , ie -22 Celsius.

Use Kelvin, "normal" is approx 293. Today is 273 , tomorrow will be 253 . You're just changing the zero point.

[Skunk]

All very interesting... :motu:

[speedpro]

since the speed of light has already been mentioned - what happens in a spaceship going REALLY fast like 99.999999% of the speed of light when a torch in the spaceship is shone forward but still within the spaceship? Does the light go forward or just sort of ooze out or collect round the lightbulb? Is it a relative thing? And what would happen if it was shone out the forward porthole? If it was shone backward would it just sort of fall out of the torch and lay there?

[N4CR]

The speed of light limitation is some crackpot stuff made up to stop people questioning physicists about light :rofl:

Nikolai Tesla in some heavily obscured 1900's experiment ... (wonder why it was obscured) sent radio waves around the world.. calculated at 3.6 times the speed of light.

Amazing how we never hear about that one. Everyone called him a crackpot and now they are starting to use some of his theories for experiments.

[Ixion]

The speed of light limitation is some crackpot stuff made up to stop people questioning physicists about light :rofl:

Nikolai Tesla in some heavily obscured 1900's experiment ... (wonder why it was obscured) sent radio waves around the world.. calculated at 3.6 times the speed of light.

Amazing how we never hear about that one. Everyone called him a crackpot and now they are starting to use some of his theories for experiments.

Actually the speed of light isn't a limitation. The idea that "you can't go faster than the speed of light" is not contained anywhere within Mr Einstein's work. It was just that assuming the speed of light to be a constant made the mathematics easier. Otherwise it appeared to become impossibly complicated. Then they discovered quantum, and it became impossibly complicated anyway. Need to use a few more dimensions.

[WINJA]

since the speed of light has already been mentioned - what happens in a spaceship going REALLY fast like 99.999999% of the speed of light when a torch in the spaceship is shone forward but still within the spaceship? Does the light go forward or just sort of ooze out or collect round the lightbulb? Is it a relative thing? And what would happen if it was shone out the forward porthole? If it was shone backward would it just sort of fall out of the torch and lay there?
ID SAY IT WOULD BE LIKE LAUNCHING A MISSILE FROM A JETFIGHTER

[Big Dave]

since the speed of light has already been mentioned - what happens in a spaceship going REALLY fast like 99.999999% of the speed of light when a torch in the spaceship is shone forward but still within the spaceship? Does the light go forward or just sort of ooze out or collect round the lightbulb? Is it a relative thing? And what would happen if it was shone out the forward porthole? If it was shone backward would it just sort of fall out of the torch and lay there?


Supercoach Jack Gibson said Andrew Ettingshausen was so quick the he could 'Turn the light out and be in bed before it was dark.'

[Bartman10]

Of course it's a "metric" scale!

One degree on the Kelvin scale is exactly the same as one degree on the Celsius scale. The only difference is that 0 degrees Celsius is the mean freezing point of water at sea level, whereas 0 degrees Kelvin is an extrapolation to "absolute zero", currently estimated as -273.15 Celsius.


Metric scales have a pysical natural zero that you cannot go below, like speed, distance, mass, Kelvin, amps, volts and so on. The Celsius scale does not fit in this category, because you can go below zero. That makes multiplication by factors such as 0.5 etc meaningless and means that Celsius is not a metric scale.

Remeber that random molecular motion is the basis of temperature, and you can't have negative molecular motion. Thus the celsius scale is misleading.

Fahrenheit thought he'd found the natural zero on his scale, at -32 Celsius, but unfortunately he was mistaken.

I'm really glad my post has drawn so much attention to temperature and physics in general. Discussion around these important topics is all good.

The thermodynamic temperature scale is defined by what’s called the triple point of water, which is defined as 273.16 Kelvin or 0.01 Celsius. The freezing point of water at atmospheric pressure really doesn't have anything to do with the definition of thermodynamic temperature; it's just a convenient point.

The triple point is the point at which the gas, liquid and solid phases are in equilibrium.

If you consider the Kelvin scale it gives you a much better appreciation of the sensitivity of living systems, a 1.6% change in body temperature will kill you! If you took the Celsius scale it would be an 11.9% change. Do you want to come around and do a little experiment? I’ll increase the average molecular agitation in your body by 6% (good safety margin there) and that’ll settle the metric scale argument for good.

[Bartman10]

since the speed of light has already been mentioned - what happens in a spaceship going REALLY fast like 99.999999% of the speed of light when a torch in the spaceship is shone forward but still within the spaceship? Does the light go forward or just sort of ooze out or collect round the lightbulb? Is it a relative thing? And what would happen if it was shone out the forward porthole? If it was shone backward would it just sort of fall out of the torch and lay there?

Light moves at the same speed for all observers. That means that if you shine a torch out the window of your space ship the light will move away from you at the speed of light. We actually live in velocity space. Space and time are linked together. I can't visualise what things would look like at very high speed because I've never experienced the warping of space-time to such an extent that it is noticeable although it is actually happening all the time. If anyone has seen the warping of space time let me know, I'd be interested to see what it looks like.

[Drew]

Light moves at the same speed for all observers. That means that if you shine a torch out the window of your space ship the light will move away from you at the speed of light. We actually live in velocity space. Space and time are linked together. I can't visualise what things would look like at very high speed because I've never experienced the warping of space-time to such an extent that it is noticeable although it is actually happening all the time. If anyone has seen the warping of space time let me know, I'd be interested to see what it looks like.
Lets sort a couple things out, I'm pretty sure I remember enough sixth form physics, to know that light has mass. So light speed, just like the speed of sound, is always different. This whole space time stuff, is many generations out of our grasp yet, and should only be looked upon for interesting things, like WINJAs' poll, on weather or not it is gay, to go back in time and give yourself a handjob.

[SPman]

Thought I read somewhere that there are particles that travel faster than C, but cant go slower! C is a barrier like the berlin wall, that hasnt been demolished yet. You're on one side or the other and never the twain shall meet!

But then.....
who gives a Toss :drinkup:

[erik]

Metric scales have a pysical natural zero that you cannot go below, like speed, distance, mass, Kelvin, amps, volts and so on. The Celsius scale does not fit in this category, because you can go below zero. That makes multiplication by factors such as 0.5 etc meaningless and means that Celsius is not a metric scale.

Remeber that random molecular motion is the basis of temperature, and you can't have negative molecular motion. Thus the celsius scale is misleading.
...


What Ixion said made sense to me (and Hitcher, except he went 3 times as cold).
Something can only be cold relative to something else.
In this case, 0°C is cold relative to the normal ambient temperature (reference temperature), say 22°C.
Twice as cold would be equal to the reference temperature minus 2 times whatever the "cold" temperature was.
Eg: 22-2*22 = -22°C

If you thought 3°C was cold relative to 22°C, twice as cold would be:

22-2*(22-3)=-16°C

[Ocean]

The answer is -145.43°C