1

New Theories / Re: what is temperature?

« on: Yesterday at 15:39:13 »

It's perfectly plausible that the cord of a lamp is making a passable antenna to transmit some RF noise from the mains and the earth cord (or the design of the lamp with more metalwork) is attenuating that.

And incandescent lamp is basically a coil of wire, it's going to generate a magnetic field when you use it.

The big question is...
Who cares?

2

New Theories / Re: what is temperature?

« on: Yesterday at 12:14:15 »

Unfortunately the makers of infrared heat lamps do not share your profound knowledge!

A good absorber is also a good emitter in the same spectrum. That's where infrared heat lamp can optimize it.
But lower frequency radiation should also be considered.

Short video about the importance of grounding your heat lamp.

What "point" are you trying to make here?

3

New Theories / Re: what is temperature?

« on: 18/01/2025 23:11:20 »

Most of us know that impedance is frequency dependent. Mathematical model for impedance is a complex number. Thermodynamics and black body radiation seem to consider only the real part of this impedance. That's because in those cases, the imaginary part is not significant. They're only special cases from the more general cases where the radiating or radiated bodies are not necessarily black body.

It's understandable that scientific research started with simpler cases. But let's not forget that there are more than what earlier discovery has told us.

You have that more or less exactly wrong.
The imaginary part of the refractive index relates to absorbing light.(And thus BBR) But  the real part relates to the wavelike properties of the light that carries on or is reflected.

"Light propagation in absorbing materials can be described using a complex-valued refractive index.[2] The imaginary part then handles the attenuation, while the real part accounts for refraction"
From
https://en.wikipedia.org/wiki/Refractive_index

Did you consider learning science (rather than just watching YT)?

4

Physiology & Medicine / Re: Is Menthol Safe?

« on: 16/01/2025 13:11:04 »

I've just realised that Lockets throat lozenges make a cough and sore throat worse

What's the evidence base for that assertion?

5

New Theories / Re: what is temperature?

« on: 16/01/2025 13:06:22 »

In this scenario, we get an increase in system entropy without any change in temperature nor internal energy.

Lucky us!
You can calculate it if you like.
https://en.wikipedia.org/wiki/Sackur%E2%80%93Tetrode_equation

6

New Theories / Re: what is temperature?

« on: 16/01/2025 12:59:24 »

I think it's necessary, since you didn't seem to realize how insignificant it was.

As I said,

you don't know what the phrase "in principle" means.

7

New Theories / Re: What makes NP problems hard to solve?

« on: 16/01/2025 12:57:26 »

IMO, the biggest factor in determining P vs NP problem is because the problem isn't well structured/defined.

And is your opinion well informed?

8

Physiology & Medicine / Re: Is Aspartame Safe And Healthy To Eat?

« on: 13/01/2025 13:10:37 »

Personally I would consider aspartame to be preferable to some of the other sweeteners, saccharin, acesulfame and sucralose as these are synthetic substances

Cyanide and arsenic are natural.

aspartame is a peptide ester. 

Botulinum toxin is a peptide and I doubt that sticking a methyl group on it would affect its properties much.

You can't easily  tell anything about a substance's toxicity from it's structure.
And the origin (natural or synthetic) tells  you nothing about whether it's harmful.

Nothing is ever "safe", but aspartame is safe enough.

9

New Theories / Re: what is temperature?

« on: 12/01/2025 14:19:52 »

Here's another thought experiment to check our understanding of temperature, and its relationship with entropy.
Two isolated containers each with 1 cubic meter volume. Their internal surface is perfectly elastic, thus doesn't absorb energy from molecules hitting it. A small pipe equipped with a closed valve is connecting those containers. Initially, the first container contains helium gas at STP, while the second container is at vacuum. The whole system is inside a space lab, isolated from outside  world.
When the valve is opened, some gas molecules will move to the second container. Since the collision with the container walls are elastic, they maintain their kinetic energy. At equilibrium, the flow rate from the first container equals the reverse flow. The pressure of both containers become half of standard pressure. The temperature is still at standard temperature, according to ideal gas law, P.V=n.R.T
The gas, which initially occupied 1 cubic meter of volume, now occupy 2 cubic meter.

Why do you keep posting stuff that we clearly already know?

By the way, if you say "an ideal gas" rather than "helium", you can get round the problem that it isn't actually ideal.

10

New Theories / Re: what is temperature?

« on: 12/01/2025 14:18:20 »

But, in principle, your spinning magnet warms it up a bit.

The effects are much less than Eddy current generated in metals, thus doesn't significantly change the temperature measurement.

The experiment in the video clearly shows this.

Eddy Current Demo #electromagnetic induction #physics #physicsninja

That's a lot of trouble to go to in order to show that you don't know what the phrase "in principle" means.

11

New Theories / Re: what is temperature?

« on: 12/01/2025 14:17:09 »

But we know that glass melts at its melting temperature.

We know that the melting point of something (when it has one- glass doesn't) is defined as the temperature where the liquid and solid phases are in equilibrium.

12

New Theories / Re: what is temperature?

« on: 09/01/2025 12:31:46 »

And, if it's not at equilibrium, it doesn't have a properly defined temperature.

If that's the case, the curve below won't be possible because the temperature is measured while heat is being transferred to/from the system.

If you look carefully, you will se the only bits of the line where the temperature is constant are the bits where there are two phases in equilibrium.

It will melt before reaching equilibrium.

I know.

And it would melt

Why do you keep posting stuff that we clearly already know?

13

New Theories / Re: what is temperature?

« on: 09/01/2025 12:20:12 »

According to Kirchhoff's law of thermal radiation, a good absorber is also a good emitter for the same radiation frequency.

There's a good chance that I told you about Kirchhoff's radiation law. I have cited it quite a bit in these pages.

14

New Theories / Re: what is temperature?

« on: 08/01/2025 23:48:53 »

On teh other hand...

Note that objects heated by radiation from incandescent lamps can have higher temperature than the glass surface of the lamps. This pose question about thermal contact. Is exchange of kinetic energy through radiation counted as thermal contact?

It does not pose that question.

If you put a mirror round the bulb so that all the radiation was reflected back then the glass would  reach thermal equilibrium with the filament. (And it would melt)
But a bit like the Calender and Barnes continuous flow water calorimeter, the heat is continuously carried away from the glass (by the air round it, and by emission of IR) , so it never reaches the same temperature as the filament.
It never reaches equilibrium.


Paradoxically, even though quartz glass is nearly opaque to far IR radiation quartz halogen lamps were sometimes used as the "light" source for far IR spectroscopy.
The radiation used was actually that emitted from the quartz envelope.

15

New Theories / Re: what is temperature?

« on: 08/01/2025 23:31:32 »

I spent several years working on "dynamic equilibrium" calorimeters for measuring ionising radiation dose rates. Long story but it was a cunning way of measuring millidegree temperature changes to better than 0.1% precision.

The classic Callendar and Barnes continuous flow water calorimeter uses a similar principle.

So... not Joule's method.
You found a method where the temperature difference between ingoing and outbound  was essentially constant.
OK.
I agree it's a very clever method.

It seems to be drifting rather from the point (so far as HY's threads ever have one)

16

New Theories / Re: what is temperature?

« on: 07/01/2025 17:52:45 »

If the magnet is spinning then viscous dag will heat the air near to it.
And then it won't be at equilibrium any more.

We tend to consider the boundary layer a stationary in laminar viscous flow. And it would be a pity if Joule's determination of the mechanical equivalent of heat by stirring water was seriously wrong - his result was within 0.75% of the current value.

Joule measured the rate of rise of temperature.
Funny looking eqm that's getting hotter with time.

17

New Theories / Re: what is temperature?

« on: 07/01/2025 10:29:20 »

But you seem un\aware of the fact that a spinning magnet in air will heat the air, thus disturbing the equilibrium.

You seem to be unaware that as an example, I put the spinning magnet inside a vacuum glass box. There will be no friction between the air and the spinning magnet. But the spinning magnet can still generate heat in nearby metals by inducing Eddy current.

I'm unaware of many things that you just decided to make up. Mindreading isn't my forte.
You should have mentioned it.


You do know that oxygen is paramagnetic, don't you?

And, if it's not at equilibrium, it doesn't have a properly defined temperature.

Does the surface of the sun have a properly defined temperature?
Does the corona of the sun have a properly defined temperature?

Fairly well defined. But, in principle, your spinning magnet warms it up a bit.
Why do you ask?

18

New Theories / Re: what is temperature?

« on: 03/01/2025 23:00:36 »

Being unaware of these effects can lead to erroneous measurement values.

And the guy who can tell you about 5 different sorts of liquid in glass thermometers is almost certainly not "unaware of these effects".
But you seem un\aware of the fact that a spinning magnet in air will heat the air, thus disturbing the equilibrium.
And, if it's not at equilibrium, it doesn't have a properly defined temperature.

What point did you think you were making, and to whom?

19

New Theories / Re: what is temperature?

« on: 03/01/2025 22:57:00 »

Depends on the radiated peak power, and is only limited by the horizon.

Pick one.
But...
"Common sense says that the air close to the spinning magnet will be  in thermal equilibrium with the magnet surface"
Not really; but the problem lies with the definition of the problem.
If the magnet is spinning then viscous dag will heat the air near to it.
And then it won't be at equilibrium any more.

20

Just Chat! / Re: What Happened To 'Ye'?

« on: 02/01/2025 16:58:44 »

Like I said before on this board, using the singular form of you (which is thee and thou in English) fell out of use a couple hundred years ago.

A lot of folk in the North of England don't agree with that assessment; and they sometimes use  "ye" too.