Ask a physicist anything. (2)

[IzzyPop]

Hot things glow because the heat excites electrons into higher orbits. Electrons are prefer lower orbits, so they fall back down. This releases energy in the form of photons. The more energy the electrons have, the higher orbits they get excited to, and thus higher energy photons are released when they fall back down. That's why hotter (more energetic) things go from invisible microwaves and infra-red rays, to visible red, to yellow, to white, as they get hotter. In other words, something glows red when it's hot enough because there's enough energy for the production of red photons.

Now, electrons are constantly getting excited then falling back down. When an object is cooled to room temperature, the electrons can't get excited as much, so they can't produce visible photons. They still produce low energy photons, mind you. That's how infra-red vision works: our bodies aren't nearly hot enough to emit visible light, but they are hot enough to emit infra-red light.

So it's not that the electrons have fallen back to a lower orbit, because they do that all the time. Rather, it's that the can't get back up to the higher orbits because they don't get enough energy.

Or, to be more precise, not enough electrons can get up there; you'd occasionally get a lucky electron that got up high, but not enough of the time for it to be visible.

Acckkk!! I thought I subscribed to the thread only to miss the first 100 or so posts so this is a semi-blind post.

How, exactly, does one excite an electron? Dinner and a movie, porn, rubbing at it's naughty bits?

 

[Wiccan_Child]

Acckkk!! I thought I subscribed to the thread only to miss the first 100 or so posts so this is a semi-blind post.

How, exactly, does one excite an electron? Dinner and a movie, porn, rubbing at it's naughty bits?

You're not far off! You excite it by giving it enough energy to be able to occupy a higher energy level. It must have at least a certain amount of energy, since energy levels in an atom are quantised (hence why quantum mechanics is called quantum mechanics: energy is quantised, at least in an atom).
You can give it this energy by any number of means. It could collide with an energetic particle, or it could absorb a photon, or what have you.

An excited electron is simply one that is in a higher energy level than 'normal'.

 

[Cabal]

Acckkk!! I thought I subscribed to the thread only to miss the first 100 or so posts so this is a semi-blind post.

How, exactly, does one excite an electron? Dinner and a movie, porn, rubbing at it's naughty bits?

Yes, you excite it till you can get it up.......






*COUGH*




sorry




....to a higher energy level.

 

[Doveaman]

Why do they call the flow of charged particles from the sun a “solar wind”? Why call it a “wind”? Isn't the flow of charged particles an electric current? If it's an electric current then the earth and all the planets in our solar system are electrically connected to the sun, are they not?

Then we are living in an electric solar system, right?

 

[Nathan Poe]

Why do they call the flow of charged particles from the sun a “solar wind”? Why call it a “wind”?

Probably for the same reason we park in a driveway but drive on a parkway -- not a whole lot of rhyme or reason in the English language.

Isn't the flow of charged particles an electric current?

Only if they're electrons.

 

[Wiccan_Child]

Why do they call the flow of charged particles from the sun a “solar wind”?

Because any fast flow of large gas is called a 'wind'. That it's ionised is neither here nor there. Besides, lots of phrases in sciences are throwbacks or colloquialisms. Particle cross-sections are measured in 'barns', which stems from when early physicists said the Uranium nucleus was 'as big as a barn'.

Why call it a “wind”? Isn't the flow of charged particles an electric current?

It's a flowing plasma, which contains (among other things) electrons. This technically constitutes an electric current, I suppose.

If it's an electric current then the earth and all the planets in our solar system are electrically connected to the sun, are they not?

Then we are living in an electric solar system, right?

If you want to use such phraseology, sure. But you may as well say I'm living in a electric body, because my body contains electrons. It's technically correct, but both misleading and superfluous.

 

[canehdianhotstuff]

Probably for the same reason we park in a driveway but drive on a parkway -- not a whole lot of rhyme or reason in the English language.



Only if they're electrons.

Not true. Flow of positive particles is also electricity.

e.g. The salt bridge in most batteries has a flow of positive ions usually.

 

[Nathan Poe]

Not true. Flow of positive particles is also electricity.

e.g. The salt bridge in most batteries has a flow of positive ions usually.

I stand corrected. thanks!

 

[Doveaman]

If you want to use such phraseology, sure. But you may as well say I'm living in a electric body, because my body contains electrons. It's technically correct, but both misleading and superfluous.

Then an electric car is both misleading and superfluous too, right?

 

[Nathan Poe]

Then an electric car is both misleading and superfluous too, right?

Only if you claim that every car is an electric car -- which, while technically correct, is in fact misleading and superfluous.

 

[Wiccan_Child]

Then an electric car is both misleading and superfluous too, right?

Yes. It's a phrase used for marketing purposes only. Obviously, all modern cars are electric, regardless of whether they run on fossil fuels or not.

EDIT: On second thoughts...

Though even they use electric turn signals.

 

[TerranceL]

Hahahaha.

 

[Doveaman]

Only if you claim that every car is an electric car -- which, while technically correct, is in fact misleading and superfluous.

It is called an electric car because it runs on electricity without the need for “fossil fuels”, therefore the term “electric car” is neither misleading nor superfluous.

 

[Doveaman]

Because any fast flow of large gas is called a 'wind'.

It’s a fast flow of electrons and protons which makes it an electric current.

Why not call it what it is? When we think of winds we tend to think of windmills and hurricanes. When we think of gas we tend to think of cooking gas or the gas we experience when we eat too much baked beans.

I’m sure the average person can better understand the term 'solar current' instead of “solar gas” or “solar wind” because they know what an electric current is.

That it's ionised is neither here nor there.

That it's ionized makes it an ‘electric current’ and not a “gas” or “wind”.

Besides, lots of phrases in sciences are throwbacks or colloquialisms. Particle cross-sections are measured in 'barns', which stems from when early physicists said the Uranium nucleus was 'as big as a barn'.

It is still an electric current.

It's a flowing plasma, which contains (among other things) electrons. This technically constitutes an electric current, I suppose.

Yes, it does.

If you want to use such phraseology, sure. But you may as well say I'm living in a electric body, because my body contains electrons. It's technically correct, but both misleading and superfluous.

When the term ‘electric body’ is used to refer to the fact that our bodies rely of those electrons to function then it is neither misleading nor superfluous.

When the term ‘electric solar system’ is used to refer to the fact that our solar system relies on the electric currents of the sun it is neither misleading nor superfluous.

Yes. It's a phrase used for marketing purposes only.

Not only. It is also used to denote the fact that the car runs on electricity without the need for “fossil fuels”.

Obviously, all modern cars are electric, regardless of whether they run on fossil fuels or not.

The phrase ‘electric car’ most often, if not always, refers to cars that run on electricity without the need for “fossil fuels”.

EDIT: On second thoughts...

Though even they use electric turn signals.

But they use horse to run, not electricity.

EDIT: On second thoughts...the horse has electrons in his body.

 

[Doveaman]

Canst thou send lightnings, that they may go, and say unto thee, Here we are?

It would seem Job knew about cosmic lightning bolts many thousands of years ago, but scientists haven't figured them out yet.

 

[AV1611VET]

It would seem Job knew about cosmic lightning bolts many thousands of years ago, but scientists haven't figured them out yet.

By the time scientists catch up to the Bible, we'll be living under a whole new set of physics.

 

[catzrfluffy]

If light doesn't get through something by passing through the gaps between the atoms, how does it get through?

 

[pgp_protector]

If light doesn't get through something by passing through the gaps between the atoms, how does it get through?

If I Recall correctly.

Photon Hits Atom, energizes the electron, the electron jumps up to the next orbit, drops down again, emits a photon, this photon then travels further, hits another atom & copy & repeat.

After a small fraction of time the photon has hit, absorbed, emitted, repeated its way through the item it's appearing to go through.

If I'm wrong, this will soon be corrected

 

[Wiccan_Child]

It’s a fast flow of electrons and protons which makes it an electric current.

I never said it wasn't. You asked why it was called a wind, and I gave you the rather straight-forward answer: because it is a wind.

Why not call it what it is? When we think of winds we tend to think of windmills and hurricanes. When we think of gas we tend to think of cooking gas or the gas we experience when we eat too much baked beans.

I’m sure the average person can better understand the term 'solar current' instead of “solar gas” or “solar wind” because they know what an electric current is.

Are you really suggesting that we throw away the entire scientific lexicon, just because the layman might not intuitively understand it?

When I think of chalk, I think of the things used in school, not the White Cliffs of Dover. But the cliffs are nonetheless made of chalk. Chalk as a specific definition, and both the little white sticks and the big white cliffs fit that definition. Likewise, a gas has a very specific definition; that propane and flatulence constitute a gas doesn't change the fact that the solar wind is also a gas.

That it's ionized makes it an ‘electric current’ and not a “gas” or “wind”.

Ionisation doesn't stop it being a gas, or a wind. An ionised gas is called a plasma.

It is still an electric current.

I never said it wasn't. I was simply pointing that colloquialisms abound in science; they aren't meant to be taken at face value.

When the term ‘electric body’ is used to refer to the fact that our bodies rely of those electrons to function then it is neither misleading nor superfluous.

When the term ‘electric solar system’ is used to refer to the fact that our solar system relies on the electric currents of the sun it is neither misleading nor superfluous.

I think you need to look up the terms 'misleading' and 'superfluous'. Namely, the former is an implied meaning other than the main, and the latter is an unnecessary description. Both 'electric body' and 'electric solar system' use 'electric' in misleading and superfluous ways.

Not only. It is also used to denote the fact that the car runs on electricity without the need for “fossil fuels”.

Indeed, but since all cars run on electricity, it is misleading and superfluous. It's like describing a car as 'mobile', or a bachelor as 'unmarried'. It implies meaning beyond the technical, and is an unnecessary descriptor.

The phrase ‘electric car’ most often, if not always, refers to cars that run on electricity without the need for “fossil fuels”.

Yes, I know what an 'electric car' is. And the point is that calling it an 'electric' car, just because it doesn't run on fossil fuels, is misleading (all cars run on electricity, not just 'electric cars') and superfluous (again, all cars run on electricity, so the descriptor is unnecessary).

I can't believe I'm having to explain this.

It would seem Job knew about cosmic lightning bolts many thousands of years ago, but scientists haven't figured them out yet.

Really? Job knew about cosmic lightning bolts? You're getting that from a single line of poetry?

 

[Wiccan_Child]

If light doesn't get through something by passing through the gaps between the atoms, how does it get through?

If I Recall correctly.

Photon Hits Atom, energizes the electron, the electron jumps up to the next orbit, drops down again, emits a photon, this photon then travels further, hits another atom & copy & repeat.

After a small fraction of time the photon has hit, absorbed, emitted, repeated its way through the item it's appearing to go through.

If I'm wrong, this will soon be corrected

Nope, that's pretty much bang on! That's why a photon appears to travel slower when passing through a medium: there is a small delay between absorption and emission, which means the photon takes every so slightly longer. Between emission and absorption, it's travelling at full light-speed.

Of course, this relies on the atom emitting the photon in the same direction as it was coming. The odds of this happening depends on the material in question: glass lets light 'through' more easily that a steel girder, though the former can become opaque if thick enough, and the latter is transparent if thin enough.

And then there's mirrors and even exotic materials with negative refractive index, which muck everything right up.