Pyrotechnic Permuations

[petrushkagoogol]

Nature manifests fire in different forms.

 

Violent : volcanoes, forest fires, lightning

Subdued : the hearth

 

Interestingly the ancient Greeks had one set of gods for the first category and another for the second. eg) Volcanus versus Hestia

 

Did they really appreciate what they were dealing with ? 

 

[exchemist]

 

Nature manifests fire in different forms.

 

Violent : volcanoes, forest fires, lightning

Subdued : the hearth

 

Interestingly the ancient Greeks had one set of gods for the first category and another for the second. eg) Volcanus versus Hestia

 

Did they really appreciate what they were dealing with ? 

 

Scientifically speaking, neither vulcanism nor lightning is fire.

 

Fire (combustion) is a particular form of exothermic oxidation reaction.

[petrushkagoogol]

Scientifically speaking, neither vulcanism nor lightning is fire.

 

Fire (combustion) is a particular form of exothermic oxidation reaction.

 

Volcanic lava comes with flames, lightning is a highly ionized plasma similar to fire, which is also a plasma (essentially)..... So I am not digressing .....

[exchemist]

Volcanic lava comes with flames, lightning is a highly ionized plasma similar to fire, which is also a plasma (essentially)..... So I am not digressing .....

There are no flames in lava, unless you have something external that is set on fire by its high temperature.  

 

Flames do not generally contain plasma.  

[petrushkagoogol]

There are no flames in lava, unless you have something external that is set on fire by its high temperature.  

 

Flames do not generally contain plasma.  

 

http://www.askamathematician.com/2013/05/q-is-fire-a-plasma-what-is-plasma/

 

Fire is a genuine plasma.  Maybe not the best plasma, or the most ionized plasma, but it does alright.

http://physics.stackexchange.com/questions/83536/why-is-lightning-considered-a-plasma

 

Plasma is when the electrons are "freed" from their host atoms for a short time, due to high temperatures. Fire is plasma, it responds to electric fields. Lightning is also plasma. When a column of electrons flows from sky to ground, the air that it passes through lights up with energy. What we see as lightning is actually the air where the electrons are at, getting excited and giving off light. Not the electrons itself. Lava refers to molten rock. Molten. Liquid. Not ionised gas. It's a plasma when it's ionised gas, nobody cares about temperature. If a gas can be ionised (IF) at -100 degrees Celsius, it's still called plasma.

 

[exchemist]

 

http://www.askamathematician.com/2013/05/q-is-fire-a-plasma-what-is-plasma/

 

Fire is a genuine plasma.  Maybe not the best plasma, or the most ionized plasma, but it does alright.

http://physics.stackexchange.com/questions/83536/why-is-lightning-considered-a-plasma

 

Plasma is when the electrons are "freed" from their host atoms for a short time, due to high temperatures. Fire is plasma, it responds to electric fields. Lightning is also plasma. When a column of electrons flows from sky to ground, the air that it passes through lights up with energy. What we see as lightning is actually the air where the electrons are at, getting excited and giving off light. Not the electrons itself. Lava refers to molten rock. Molten. Liquid. Not ionised gas. It's a plasma when it's ionised gas, nobody cares about temperature. If a gas can be ionised (IF) at -100 degrees Celsius, it's still called plasma.

 

 

Yes, I take your point but I don't entirely buy that explanation. I think they should have spoken to a chemist, because what goes on in a flame is a series of chemical reactions, not just physics!

 

Flames can contain ions, I agree, and if so will respond to an electric field as shown in the demo, but a real plasma involves a serious degree of dissociation of gas into ions. To do this thermally, which is how it would take place in a flame (as opposed to an electric arc, for instance), needs temperatures hotter than many flames. The light emitted by most flames is not due to incandescence but to formation of excited states of molecules during combustion. More here: https://en.wikipedia.org/wiki/Flame

 

You may notice that the Wiki article on plasma states that only "some flames" can be considered plasma.

 

This fits what I have always understood about flames.

[CraigD]

Interestingly the ancient Greeks had one set of gods for the first category and another for the second. eg) Volcanus versus Hestia

I don’t think we should make too close a connection between Hephaestus/Vulcan and volcanos, which take their name from this mythological figure’s Roman name. Haphastus character was famed for using fire in a controlled manner for forging metal, not letting it burn in a destructive, out-of-control way. In myths and superstitions, ancient Greeks imagined volcanos to be vents of this giant god’s underground forges, not the main work he was about. Likewise, Hestia/Vesta was famed in myth for using fire in a controlled manner for household heating and cooking

 

Both Haphaestus and Hestia were about control of fire. Haphaestus’ mythic forge fires were hotter than Hestia’s cooking ones, but both were safe and controlled.

 

Did they really appreciate what they were dealing with ?

I think it’s important to understand that while the Greeks were impressively good at math, geometry, and practical mechanics on a scale visible to the naked eye – they knew the Earth was a spheroid, and by 240 BC had cleverly measured its diameter with about 90% accuracy – they had no spectrometers or thermometers, so had only a sketchy understanding of light, heat and temperature. So while they, like prehistoric humans, knew fire made objects hot, and hot objects could ignite fires, they didn’t have a good theory of why.

 

You may notice that the Wiki article on plasma states that only "some flames" can be considered plasma.

The description I prefer is that some parts of a flame are plasma, while others parts are gas mixed with particles in a liquid and solid state.

 

You can get a good intuitive feel for the difference between merely hot, glowing matter and matter in a plasma state by using a spectrometer. Glowing stuff, even metals with lots of electrons making different shell transitions to emit different frequency photons, have sharp emission spectral bands with nothing in between. Plasmas, with their wandering electrons emitting photons willy-nilly, have smooth spectra with gaps caused only by absorption by non-plasma state electrons.

 

Taking a couple of images from the Wikipedia article “emission spectrum” we see this spectrum for glowing iron:

and this from a plasma in ionized vapor lamp:

 

Spectrographically, plasma “fills the gaps”.

[exchemist]

I don’t think we should make too close a connection between Hephaestus/Vulcan and volcanos, which take their name from this mythological figure’s Roman name. Haphastus character was famed for using fire in a controlled manner for forging metal, not letting it burn in a destructive, out-of-control way. In myths and superstitions, ancient Greeks imagined volcanos to be vents of this giant god’s underground forges, not the main work he was about. Likewise, Hestia/Vesta was famed in myth for using fire in a controlled manner for household heating and cooking

 

Both Haphaestus and Hestia were about control of fire. Haphaestus’ mythic forge fires were hotter than Hestia’s cooking ones, but both were safe and controlled.

 

I think it’s important to understand that while the Greeks were impressively good at math, geometry, and practical mechanics on a scale visible to the naked eye – they knew the Earth was a spheroid, and by 240 BC had cleverly measured its diameter with about 90% accuracy – they had no spectrometers or thermometers, so had only a sketchy understanding of light, heat and temperature. So while they, like prehistoric humans, knew fire made objects hot, and hot objects could ignite fires, they didn’t have a good theory of why.

 

The description I prefer is that some parts of a flame are plasma, while others parts are gas mixed with particles in a liquid and solid state.

 

You can get a good intuitive feel for the difference between merely hot, glowing matter and matter in a plasma state by using a spectrometer. Glowing stuff, even metals with lots of electrons making different shell transitions to emit different frequency photons, have sharp emission spectral bands with nothing in between. Plasmas, with their wandering electrons emitting photons willy-nilly, have smooth spectra with gaps caused only by absorption by non-plasma state electrons.

 

Taking a couple of images from the Wikipedia article “emission spectrum” we see this spectrum for glowing iron:

and this from a plasma in ionized vapor lamp:

 

Spectrographically, plasma “fills the gaps”.

Er, well, not entirely right. Glowing solid or liquid metals do not exhibit an emission spectrum: they radiate as black bodies, with a continuous spectrum. A well-known example is the tungsten filament of a traditional light bulb. (There are no discrete energy levels of the valence electrons in a metal: they are delocalised in bands.)

 

To get an emission spectrum, you need to excite free gaseous atoms, which do have electrons in discrete energy levels, rather than merely heat the solid metal. The spectrum you show will have been obtained in that way, perhaps in an electric arc, or indeed in a flame. 

[CraigD]

Er, well, not entirely right. Glowing solid or liquid metals do not exhibit an emission spectrum: they radiate as black bodies, with a continuous spectrum.

Yeah, you’re right. :( I don’t know what I was thinking – when I had a spectrometer, I took spectrographs of everything I could think find, including, or course, an incandescent light and a glowing electric stove element (a tough image to see, since it’s very dim compared to most light sources). As you say, hot stuff in a solid state has a smooth spectrum, not a very perfect black body spectrum, but roughly one.

 

Here’s the spectrum of an incandescent light, taken from the first image that came up in a google search for “incandescent spectrum (taken from, of all places, an old website campaigning against US regulations phasing out incandescent lights in favor of more power-efficient ones):

Not very perfectly blackbody, but not too far off.

 

Here’s a graph of the ideal blackbody spectrum, from its Wikipedia article:

 

Why, I wonder, is that? The many electrons in an hot atom of iron in a gas state, not much interacting with other atoms has a sharp spectrum. When they are near other atoms in a solid, is the change in energy of an electron emitting a photon not determined exactly by it change in atomic orbital, but rather also by its interaction with neighboring atoms?

[exchemist]

Yeah, you’re right. :( I don’t know what I was thinking – when I had a spectrometer, I took spectrographs of everything I could think find, including, or course, an incandescent light and a glowing electric stove element (a tough image to see, since it’s very dim compared to most light sources). As you say, hot stuff in a solid state has a smooth spectrum, not a very perfect black body spectrum, but roughly one.

 

Here’s the spectrum of an incandescent light, taken from the first image that came up in a google search for “incandescent spectrum (taken from, of all places, an old website campaigning against US regulations phasing out incandescent lights in favor of more power-efficient ones):

Not very perfectly blackbody, but not too far off.

 

Here’s a graph of the ideal blackbody spectrum, from its Wikipedia article:

 

Why, I wonder, is that? The many electrons in an hot atom of iron in a gas state, not much interacting with other atoms has a sharp spectrum. When they are near other atoms in a solid, is the change in energy of an electron emitting a photon not determined exactly by it change in atomic orbital, but rather also by its interaction with neighboring atoms?

It's because in a metal the valence shell atomic orbitals, each of which has a sharply defined energy level, overlap and merge into energy level BANDS. There is a "sea" of electrons, all at slightly different energy levels and no longer attached to any individual atom. The idea of atomic orbitals overlapping and merging to form molecular orbitals is how chemical bonding is accounted for. In a metallic structure, the process involves merging of all the valence shell atomic orbitals across the lattice, thus forming this energy band continuum.

 

In general one has to be careful with "condensed matter" phases. One tends to learn a lot about idealised, monatomic gas phase atoms, whereas real matter very often involves chemical bonding regimes, which modify the picture considerably.  

[petrushkagoogol]

I don’t think we should make too close a connection between Hephaestus/Vulcan and volcanos, which take their name from this mythological figure’s Roman name. Haphastus character was famed for using fire in a controlled manner for forging metal, not letting it burn in a destructive, out-of-control way. In myths and superstitions, ancient Greeks imagined volcanos to be vents of this giant god’s underground forges, not the main work he was about. Likewise, Hestia/Vesta was famed in myth for using fire in a controlled manner for household heating and cooking

 

Both Haphaestus and Hestia were about control of fire. Haphaestus’ mythic forge fires were hotter than Hestia’s cooking ones, but both were safe and controlled.

I disagree with the role of Hephaestus as defined by you. His festival, the Volcanalia had priests throw small fish into the fire, so as to appease the god, and thereby prevent destruction of grain by fire, and the collateral damage also, namely human life. For this reason his worship was at Ostia, outside of Rome. (where the granaries were present). His fire was the fire of conflagarations, and this is epitomized by Volcanoes. :xmas_tree: :xmas_tree: :xmas_tree:

[CraigD]

I disagree with the role of Hephaestus as defined by you. His festival, the Volcanalia had priests throw small fish into the fire, so as to appease the god, and thereby prevent destruction of grain by fire, and the collateral damage also, namely human life. For this reason his worship was at Ostia, outside of Rome. (where the granaries were present). His fire was the fire of conflagarations, and this is epitomized by Volcanoes.

I think both our characterization are right, because while the Romans were aware of the Greek’s god Hephaestus and equated him with their Vulcan, these 2 were religious figures among separate peoples for centuries before their merging in the Roman pantheon, and were imagined by their worshipers very differently.

 

I’ve not made a deep study of the history of ancient religions, but from encyclopedia entries, gather that the ancient Roman’s Vulcan was the appeasement-requiring, destructive deity you describe, while the ancient Greek’s Hephaestus was primarily the blacksmith and craftsman deity I describe. Vulcan was credited with Hephaestus’ craftiness mostly by later writers and artists, or by religionists eager to supplant the Greek gods with Roman ones. To his actual worshipers, he was a destroyer, or, if you gave him enough sacrificial fish, protector.

 

My fault for slash-conflating these two. Though the Romans may have tried to equate them, to their oldest worshipers, Hephaestus and Vulcan were distinctly different deities.

 

Sources: https://www.britannica.com/topic/Hephaestus; https://www.britannica.com/topic/Vulcan; http://romanandgreekmythology.weebly.com/hephaestusvulcan.html

[petrushkagoogol]

I think both our characterization are right, because while the Romans were aware of the Greek’s god Hephaestus and equated him with their Vulcan, these 2 were religious figures among separate peoples for centuries before their merging in the Roman pantheon, and were imagined by their worshipers very differently.

 

I’ve not made a deep study of the history of ancient religions, but from encyclopedia entries, gather that the ancient Roman’s Vulcan was the appeasement-requiring, destructive deity you describe, while the ancient Greek’s Hephaestus was primarily the blacksmith and craftsman deity I describe. Vulcan was credited with Hephaestus’ craftiness mostly by later writers and artists, or by religionists eager to supplant the Greek gods with Roman ones. To his actual worshipers, he was a destroyer, or, if you gave him enough sacrificial fish, protector.

 

My fault for slash-conflating these two. Though the Romans may have tried to equate them, to their oldest worshipers, Hephaestus and Vulcan were distinctly different deities.

 

Sources: https://www.britannica.com/topic/Hephaestus; https://www.britannica.com/topic/Vulcan; http://romanandgreekmythology.weebly.com/hephaestusvulcan.html

 

http://supernaturalcreatures.org/encyclopedia/vulcan/