1

New Theories / Re: what is temperature?

« on: Yesterday at 21:16:39 »

"The potential energy of a strained lattice may be enormous"
yes, it was the cause of the Windscale fire- it made the graphite very hot...

No, it was the release of Wigner potential energy that raised the temperature. Problem is that once you reach the annealing temperature you can initiate a chain reaction that outstrips the cooling capacity of the system - as happened at Windscale.

2

Just Chat! / Re: Why are cigarette smokers so brand loyal?

« on: Yesterday at 21:10:35 »

A habit is a habit, and becomes part of a personality and identity. Ask any addict or churchgoer.

3

Physics, Astronomy & Cosmology / Re: How can I pass a large DC current through mercury?

« on: Yesterday at 21:08:18 »

The reason mercury was so useful in barometers stems from its low vapor pressure at room temperature

And there was me thinking it was the density..
Presumably all the ten metre high barometers full of water  somehow escaped my attention.
The water vapour pressure is a complication, but you could allow for it.

If you had a liquid of similar density but high vapor pressure, the barometer would be more sensitive to temperature. Not a problem for a laboratory instrument where you can apply any number of corrections but an additional complication at sea. 

4

General Science / Re: How do we make synthetic gasoline?

« on: Yesterday at 21:04:39 »

Thanks in part to Margaret Thatcher, whose most significant political acts were to welcome General Pinochet to the UK, install gates across Downing Street, and assume the role of Head of State previously held by the Queen, one third of THE ECONOMY  is spent on mortgages.

If wind power isn't free, why are people so excited by it?

5

New Theories / Re: what is temperature?

« on: Yesterday at 12:36:42 »

This is why temperature is in units of energy.

No. The mean energy of a particle within a body is k_BT  where k_B is the Boltzmann constant, whose dimensions are joules per kelvin.

Entropy is dimensionless.

No. The dimensions of entropy are joules per kelvin.

6

General Science / Re: How do we make synthetic gasoline?

« on: Yesterday at 12:26:38 »

As long as the input energy is free, that isn't a problem. It's a possible solution to  transport problems: you can use free wind power to make a fuel compatible with all existing vehicles including ships and planes, with no net carbon emission.

7

New Theories / Re: what is temperature?

« on: Yesterday at 10:23:02 »

Temperature is the amount of energy required to change the entropy by one bit.

So the entropy of an object at constant temperature is continually changing?  Welcome to the world of Hamdani Yusuf!

The gradient is d height/ d distance .
That doesn't mean that all hills are moving.
That's not H Y's world, nor S T's world.
It's only in your world.

So if T>0, by ST's statement there is plenty of available energy in the system to change its entropy, and nothing to stop it.

8

New Theories / Re: what is temperature?

« on: Yesterday at 10:20:34 »

It's any form of energy.

Er, no. The potential energy of a strained lattice may be enormous, but as that can't be transferred by thermal conduction to another body, it doesn't affect its temperature.

There's a discussion elsewhere about dissolving a stressed spring.

9

Physics, Astronomy & Cosmology / Re: How can I pass a large DC current through mercury?

« on: Yesterday at 10:15:33 »

Just as well the US Navy (nor Roscosmos, in the early days) don't watch Youtube.

science.howstuffworks.com/rail-gun1.htm

10

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: Yesterday at 10:10:59 »

It only shows that average temperature of an object (ice-water mixture) can be different than local temperature at specific location

An average being different from a sample? My god, he's invented statistics! There's a Nobel physics prize awaiting if you can demonstrate it, and  Fields Medal if you can present a mathematical proof. Or maybe not.

11

General Science / Re: How do we make synthetic gasoline?

« on: Yesterday at 10:08:42 »

Audi have made synthetic gasoline directly from atmospheric CO2 and H2O. Almost as efficiently as a tree.

12

New Theories / Re: An essay in futility, too long to read :)

« on: 23/05/2022 23:12:52 »

Seems they believe that none except Putin had a hand in creating this war.

I don't recall anyone else having the authority to command the Russian army to invade Ukraine.

13

New Theories / Re: what is temperature?

« on: 23/05/2022 23:06:14 »

Would that be 0.3010 or 0.6931? Or does it mean log₂ of any number you can think of?

14

General Science / Re: How do we make synthetic gasoline?

« on: 23/05/2022 23:00:10 »

The best thing about the Lurgi process is its name!

That said, some London buses and taxis ran on producer gas during WWII, and if the Thatcher government hadn't destroyed the mines, there would be around 200 years-worth of convertible coal under the UK.

15

New Theories / Re: what is temperature?

« on: 23/05/2022 18:48:53 »

How do you calibrate temperature far from those defining points, such as 1 milli Kelvin, or 1 million Kelvin?

You can only calibrate an instrument at the agreed fixed points. You can interpolate or extrapolate other values.

I measured microdegfree temperature changes with a thermistor, whilst my good buddy (also named Alan)  in the next lab measured plasma temperatures of 100 MK by studying the electron resonance spectrum. Herr Boltzmann's Konstant was very helpful in both cases.

16

New Theories / Re: what is temperature?

« on: 23/05/2022 18:42:54 »

So, what's your answer to this question : what is temperature?

A measure of the internal kinetic energy of a body.

17

New Theories / Re: what is temperature?

« on: 23/05/2022 18:41:38 »

Temperature is the amount of energy required to change the entropy by one bit.

So the entropy of an object at constant temperature is continually changing?  Welcome to the world of Hamdani Yusuf!

18

Physics, Astronomy & Cosmology / Re: Is there a net heat exchange between water and ice at 0 degree C?

« on: 23/05/2022 18:35:16 »

Sadly, many people have attempted to disprove the laws of thermodynamics, with increasingly sophisticated apparatus. The goal is unlimited wealth and omnipotence - you could make a whole new universe! But AFAIK nobody has succeeded.

19

Question of the Week / Re: QotW - 22.05.23 - Where does the potential energy of a spring go in acid?

« on: 23/05/2022 18:32:18 »

My father was asked the same question in the 1940s - it's a real classic.

Fortunately James Joule answered it on his honeymoon when he measured the mechanical equivalent of heat, 4.2 joules per calorie. If you dissolve two identical springs, one compressed, and measure the heat of reaction, one will release a bit more energy. 

20

Physics, Astronomy & Cosmology / Re: How can I pass a large DC current through mercury?

« on: 23/05/2022 18:28:25 »

The reason mercury was so useful in barometers stems from its low vapor pressure at room temperature, allowing it to be used also in diffusion pumps if silicones and organics are undesirable. The incidence of mercury poisoning from the pure metal is very sporadic: there are films of workers in a mercury production plant walking on the surface of vats of the stuff, yet some people succumb to its neurotoxicity at extraordinarily low concentrations.

Nevertheless the MIT experiment was about 40 years behind the times. The electrodynamic railgun was proposed as a satellite launcher in the 1960s and you can make a satisfyingly dangerous model that propels ball bearings  along two parallel rails. IIRC we used 500 microfarad capacitors charged to 300V to deliver a good whack of pulsed current through the 5 mm ball. Apart from the risks of electrocution and an occasional broken window, the college authorities found it quite amusing.