Gravity on the Ships from Sci-Fi Movies/Shows

[s09119]

we might have a rather good understanding of gravity, there are still many mysteries

That doesn't mean "real gravity doesn't exist" like some people are arguing.

[K^2]

That doesn't mean "real gravity doesn't exist" like some people are arguing.

We can discuss your issue with that as soon as you explain what "real gravity" is.

[Aer'ki]

We can discuss your issue with that as soon as you explain what "real gravity" is.

No, you explain it. It's your terminology.

Centrifugal force is fictitious, but so is real gravity, so that's alright.

[morrismike]

Centrifugal force is fictitious, but so is real gravity, so that's alright.

No, the mechanism for artificial gravity is never properly explained, because nobody knows how to produce any other sort than centrifugal that does not involve accelerating black holes.

Centrifugal force is imaginary for physists but it is a very real force (albiet dependent on a very specific point of reference) that is used by engineers to design a great many things. The water making it to your tap wouldn't arrive without pumps utilizing centrifugal force. The U235 rich UFl6 segregation wouldn't be possible without it. Ditto for many processes used to segregate particles. Your vacuum cleaner...... I can do this all day.

I can appreciate the fact you may be a lab nerd but just let this one go.

Physists (and a great many dumb engineers) explain explain electrical current as "holes" moving when in fact current is the flow of charged particles (electrons). Try to explain to a college professor that current flow is the movement of electrons and you'll get a blank stare. It all depends on your frame of reference.

[Quadhelix]

Physists (and a great many dumb engineers) explain explain electrical current as "holes" moving when in fact current is the flow of charged particles (electrons). Try to explain to a college professor that current flow is the movement of electrons and you'll get a blank stare. It all depends on your frame of reference.

This might not be a fair example, but I just finished taking Electromagnetic Theory, and the professor specifically mentioned the Hall Effect - which first showed that the charge carriers in electrical currents are negative, i.e., electrons.

The thing about holes only arises in materials where the Hall effect shows that the charge carriers are positive. In that case, you have actual positive charge carriers, although the charge carriers are just holes that get filled by an electron.

[morrismike]

This might not be a fair example, but I just finished taking Electromagnetic Theory, and the professor specifically mentioned the Hall Effect - which first showed that the charge carriers in electrical currents are negative, i.e., electrons.

The thing about holes only arises in materials where the Hall effect shows that the charge carriers are positive. In that case, you have actual positive charge carriers, although the charge carriers are just holes that get filled by an electron.

and yet it's the electrons in motion

[Quadhelix]

and yet it's the electrons in motion

Yes, but that was not my point: you said, "Try to explain to a college professor that current flow is the movement of electrons and you'll get a blank stare" (here). I was saying that, yeah, you'd get a blank stare, because they would be wondering why on Earth you were explaining something to them that they already know.

Also, as I mentioned, materials in which electric current behaves as moving "holes" are the exception, rather than the rule. Furthermore, the reason that the explanation is of moving holes is because the materials behave as though they had positive, not negative, charges flowing moving through them. Therefore, in a very real sense, the charge carriers are not the electrons, but rather the holes that the electrons fill.

[K^2]

No, you explain it. It's your terminology.

In that context, I meant gravity caused by mass. Apologies if that was not clear. But it's certainly not what was meant in the text I was quoting. So my statement remains valid.

Centrifugal force is imaginary for physists but it is a very real force (albiet dependent on a very specific point of reference) that is used by engineers to design a great many things. The water making it to your tap wouldn't arrive without pumps utilizing centrifugal force. The U235 rich UFl6 segregation wouldn't be possible without it. Ditto for many processes used to segregate particles. Your vacuum cleaner...... I can do this all day.

Centrifugal force is not imaginary to Physicists. Occasional school physics teacher, maybe, but that's hardly the same.

Centrifugal force is fictitious. There is always an inertial frame of reference where it does not exist. Same goes for gravity. Same goes for any force resulting from accelerating frame of reference.

If you do not understand what a fictitious force is, the only thing I can suggest is a standard graduate level classical mechanics text, section on accelerated frames of reference. Plus any literature necessary to get you to the point where you can actually read and understand it.

I can appreciate the fact you may be a lab nerd but just let this one go.

Thanks for the laugh.

Physists (and a great many dumb engineers) explain explain electrical current as "holes" moving when in fact current is the flow of charged particles (electrons).

Current is defined as flow of positive charge. That's the definition. "Holes" are quasi particles in certain types of conducting media, and are only used to describe conductivity in such media. E.g. P-type Semiconductors.

If you are going to use something as an example, try to make sure you actually understand it.

[lordofseas]

In that context, I meant gravity caused by mass. Apologies if that was not clear. But it's certainly not what was meant in the text I was quoting. So my statement remains valid.

Centrifugal force is not imaginary to Physicists. Occasional school physics teacher, maybe, but that's hardly the same.

Centrifugal force is fictitious. There is always an inertial frame of reference where it does not exist. Same goes for gravity. Same goes for any force resulting from accelerating frame of reference.

If you do not understand what a fictitious force is, the only thing I can suggest is a standard graduate level classical mechanics text, section on accelerated frames of reference. Plus any literature necessary to get you to the point where you can actually read and understand it.

Thanks for the laugh.

Current is defined as flow of positive charge. That's the definition. "Holes" are quasi particles in certain types of conducting media, and are only used to describe conductivity in such media. E.g. P-type Semiconductors.

If you are going to use something as an example, try to make sure you actually understand it.

I am not a physicist. But, isn't current, electricity, [insert other name], the flow of electrons, which are negatively charged, compared to protons, which are positively charged?

[K^2]

I am not a physicist. But, isn't current, electricity, [insert other name], the flow of electrons, which are negatively charged, compared to protons, which are positively charged?

Current can be caused by motion of positively or negatively charged particles. In metals, yes, it is motion of electrons that causes current. But it isn't the current itself.

Current was defined a long time ago to be flow of positive charge. For a single particle, you can think of current caused by this particle as velocity of the particle times its charge. Electrons have negative charge, so an electron moving to the right causes current to the left.

This is greatly oversimplified, of course, for the sake of discussion.

[morrismike]

I am not a physicist. But, isn't current, electricity, [insert other name], the flow of electrons, which are negatively charged, compared to protons, which are positively charged?

It's all semantics. At some point the academics were faced with a quandry in that energy flows from high to low potential. In the case of a battery energy (electron flow) goes from negative to positive and they got their panties in a wad. It's obvious to anyone with a lick of sense that the "negative" and "positives" are polarity and the electrons are driven by a differential potential but in order to make it all seem right, everything was based on positive charge flow. As hard as this will be for you to believe there are many college professors (engineering and physics) that won't even speak of electron flow as they feel it is a distraction.

[Quadhelix]

At some point the academics were faced with a quandry in that energy flows from high to low potential.

How do they know which way the energy is flowing?

It's obvious to anyone with a lick of sense that the "negative" and "positives" are polarity and the electrons are driven by a differential potential but in order to make it all seem right, everything was based on positive charge flow.

Again, the direction of current was defined before the discovery of the electron, so it made sense to define current as a flow of positive charge. Once it was discovered that the charge carriers in most materials are negative, it made no sense to change the convention because there is no practical difference outside specialized circumstances.

As hard as this will be for you to believe there are many college professors (engineering and physics) that won't even speak of electron flow as they feel it is a distraction.

Well, save under very specific circumstances (e.g., the Hall effect), there is very little practical difference between positive charge flowing one way and negative charge flowing the other way.

[morrismike]

How do they know which way the energy is flowing?



Again, the direction of current was defined before the discovery of the electron, so it made sense to define current as a flow of positive charge. Once it was discovered that the charge carriers in most materials are negative, it made no sense to change the convention because there is no practical difference outside specialized circumstances.


Well, save under very specific circumstances (e.g., the Hall effect), there is very little practical difference between positive charge flowing one way and negative charge flowing the other way.

Nearly all technology in use today depends on electrons flowing thru wires and I fail to see how this could be a "specialized circumstance" if it applies to everything (same logic with centrifugal force). Even those semiconductors where holes come into play wouldn't work without electron flow. I can appreciate the need to hang on to tradition but peoples understanding of things will improve if they are taught make believe things or have to be told to push the "I believe" button by teachers.

[Quadhelix]

Nearly all technology in use today depends on electrons flowing thru wires and I fail to see how this could be a "specialized circumstance" if it applies to everything (same logic with centrifugal force).

However, 98 times out of 100, the electrons flowing in one direction can be treated as positively charged particles flowing in the other direction without changing the result.

The "specialized circumstances" are the 2 times out of 100 when negative charge flowing one way would behave differently than positive charge flowing the other way.

Even those semiconductors where holes come into play wouldn't work without electron flow.

Except that, in those cases, the charge carriers can be shown to be positive. Since electrons are not positive, they are quite clearly not the charge carriers.

I can appreciate the need to hang on to tradition but peoples understanding of things will improve if they are taught make believe things or have to be told to push the "I believe" button by teachers.

Except that, again, there are only a handful of cases when positive charge flowing one way needs to be treated differently than negative charge flowing the other way.



Furthermore, there is the issue of current as a broader phenomenon. Electrical circuits, as common as they are, are still only a single example.

For example, if you have a circuit driven by a battery, electrons do flow through the circuit from the negative terminal to the positive terminal. However, within the battery (depending on the type of battery), positive ions flow from the negative terminal to the positive terminal - that is current as well.

[Aer'ki]

Nearly all technology in use today depends on electrons flowing thru wires and I fail to see how this could be a "specialized circumstance" if it applies to everything (same logic with centrifugal force). Even those semiconductors where holes come into play wouldn't work without electron flow. I can appreciate the need to hang on to tradition but peoples understanding of things will improve if they are taught make believe things or have to be told to push the "I believe" button by teachers.

Well said...except 'will' should be 'won't,' but I think people got the idea.

Pure academics lends toward fiction. Only when such extrapolation is grounded in reality does it become science. Technology is a form of grounding, as are other real life experiences. People who believe the universe is a giant hologram or that all matter is nothing more than magnetic fields need to get outside and get smacked in the head with a baseball...then see if its all a matter of perspective.

This is why I don't give much credence to anything coming from 'theoretical scientists.'