1

New Theories / Re: what is temperature?

« on: Today at 13:09:47 »

Why? It's pretty obvious that a conductor carrying a couple of amps at 50 - 60 Hz is going to radiate em. The question is whether that actually matters in the context of all the other current carriers in the  house.

It depends on the shape of the conductors, whether it will act like an antenna, or more like a Faraday cage.

LED lamps obviously emit less because they are DC-powered, but if you obtain that power from the mains, you are probably emitting 100 kHz  from the switch-mode power supply.

That oscillation can be radiated to its surroundings. It can affect the temperature measurement of some types of thermometers, especially the electronic ones.

Why do you keep stating the obvious?

2

The Environment / Re: How are global warming and world population expansion linked?

« on: Yesterday at 19:35:59 »

However, places like Gaza and Cox Bazaar have around 4 children and such places can never become self sustaining.

They will if half the kids die.
Sadly that's all too plausible.

3

New Theories / Re: what is temperature?

« on: Yesterday at 15:16:58 »

What makes you fail to distinguish between impedance and refractive index?

The fairly close relationship between them.
The impedance is sqrt(  permeability /permittivity).

And (for non magnetic materials) the dielectric constant is the square of the refractive index.

Light reflected from a window is an impedance mismatch effect.

Were you aware of this?
https://en.wikipedia.org/wiki/Clausius%E2%80%93Mossotti_relation

4

Technology / Re: Is producing our own petrol a viable idea?

« on: Yesterday at 15:08:59 »

I shall inform you that many motorhome and caravan heaters are diesil, not gas,

That's a fairly pointless thing to tell someone who was talking about ..

I see a lot of people buying those cheap diesel heaters.

The only difference seems to be that you didn't spell it correctly.

5

Technology / Re: Is producing our own petrol a viable idea?

« on: Yesterday at 15:07:25 »

It is a good way of storing energy

Not really.
There's probably a case for using hydrocarbons for planes where weight is really important.

6

Technology / Re: Is producing our own petrol a viable idea?

« on: Yesterday at 15:04:17 »

but you need a vent.

So what?
Places where people live need a vent.

7

New Theories / Re: what is temperature?

« on: 22/01/2025 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?

8

New Theories / Re: what is temperature?

« on: 22/01/2025 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?

9

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)?

10

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?

11

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

12

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.

13

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?

14

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.

15

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.

16

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.

17

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.

18

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?

19

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.

20

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.