Sticking with the numbering system you've introduced...
1) Again, I think your disagreement is based on philosophical grounds. In more familiar terms, we might ask if chairs exist. "Of course they do!" Well, what qualifies a chair? Is it something on which you rest your butt? Then what is a butt? Is a bean bag chair a chair? It has no specific solid form. How about a stump? That isn't man-made. What if I begin carving a seat into that stump? At what precise instant does it cease to be a stump and become a chair?
I find these arguments absurd and pointless. If you want to go that route, you quickly find yourself in the realm of essentialism. Philosophically, I tend to lean the other way, toward existentialism, which would appear to support and expand on your view. It isn't just that virtual photons don't exist, no human constructs can be meaningfully said to exist! We're all one big gelatinous mess of a wavefunction attempting to derive meaning out of subsets of ourselves, never able to grasp the big picture.
But I'm also a scientist. If I throw a ball into the air at a very specific speed and it consistently returns to my hand in two seconds, do I really need to question the existence of the ball itself? No. I like to get things done. In terms of their predictive power, virtual photons seem to be more real than balls or frictionless surfaces or blocks on inclined planes or other more familiar notions.
Your point is that other notions are useful but not real. Maybe, maybe not. It depends on what you mean by useful. For a scientist, numerical predictions trump all. What about non-mathematical notions? Is love real? It seems to be a construct of the mind, yet we seem to have a decent understanding of how love affects people. Again, this is a mostly philosophical question of where to draw the line and I begin to lose interest when we leave the realm of science and enter philosophy.
I'm very interested, however, in where you draw the line. What is something that you consider useful but not "real"?
2) I should have been more clear. Virtual UFOs make no testable, falsifiable, or substantiated predictions about how physics works. You said this is easy to fix, so what's your proposal? We don't have to discuss it at length.
3) You lost me here. Admittedly, particle physics isn't really my forte, but your claims seem fishy to me. It does take energy to create a magnetic field and a magnet will lose energy if it radiates some if it away. You may be confused by the fact that the magnetic force can do no work, but that can be reconciled (tediously) by entering a moving reference frame in which the magnetic field is transformed into an electric field. Historically, quantum field theory was developed to reconcile special relativity and quantum mechanics. Practically, the subject produces predictions of things like the magnetic dipole moment of the electron and scattering coefficients. I'm not sure how that ties in with the magnetic field energy.
1) Sure, for things such as chairs you will always get problems on where to draw the line. Elemental particles do not have this problem. They are strictly defined in mass, spin, charge, etc. An electron is never a proton, which is never a photon.
Some things which are useful but don't exist are:
- Personification of inanimate objects (the air "wants" to get out when there's a pressure difference)
- Fairy-tales
- Thinking of electricity as a rope, the voltage as how hard you pull, the resistance how much friction there is, and the current as the speed of the rope.
2) You added "testable, falsifiable, or substantiated" now. At first it was just a prediction, which I said is easy enough to add. For example: virtual UFOs make the universe expand. We know virtual UFOs to be real because the universe expands faster than expected from just gravity. Also, virtual UFOs steal socks in washing machines. We know this to be true because sometimes a sock is missing.
Anyway, I don't see why we should discuss that, because it quickly becomes silly.
3) I can't say I'm well versed in it either (which is probably why I can't get virtual particles) but take this example: an electron. It has an electric charge. That means it will repel another electron. How does it "tell" (see, personification again) the other electron that it's there? By emitting photons, the electromagnetic force carrier. But sending out photons would mean that the electron would lose energy, and we know that the mass and charge stays the same for every electron. So we say that those photons aren't real photons, they are virtual. But now you say that on long range they are real - so where does the energy to send out real photons in all directions constantly come from?
Joined: 10/27/2004
Posts: 1978
Location: Making an escape
Question for clarification of all this talk about "conventional current."
Let's take a look at this Duracell battery.
The top is, obviously, labeled positive, with the bottom being negative. If I understand correctly, are we saying that, when we put a load between the top and the bottom of this battery, that electrons flow from the bottom to the top?
A hundred years from now, they will gaze upon my work and marvel at my skills but never know my name. And that will be good enough for me.
Question for clarification of all this talk about "conventional current."
Let's take a look at this Duracell battery.
The top is, obviously, labeled positive, with the bottom being negative. If I understand correctly, are we saying that, when we put a load between the top and the bottom of this battery, that electrons flow from the bottom to the top?
You are understanding correctly. The electrons flow from the bottom through the load to the top.
In electric calculations, because electricity was discovered before electrons were understood, it was (unfortunately incorrectly) guessed that current flowed from plus to minus. This has continued to this day for backwards compatibility.
Marx wrote:
What if protons flow?
Will it be from top to bottom?
Protons don't usually flow in an electric circuit. The protons make up the cable which the electrons move through, and are stationary.
If an electrolyte is used instead of a cable, it is a bit more tricky. The ions in the electrolyte flow in both directions at the same time, as rhebus talked about earlier.
(Feel free to correct me if I'm wrong everyone, it was a while ago I studied this.)
Basically, hundreds of years ago, before electrons were discovered, somebody guessed randomly that the charge carriers in a metal were positive. He guessed wrong. Physics has never changed the convention.
Basically, hundreds of years ago, before electrons were discovered, somebody guessed randomly that the charge carriers in a metal were positive. He guessed wrong. Physics has never changed the convention.
It means you're using the wrong formula.
The definition of density is simple:
density = mass / volume
If you have any finite amount of mass and compress it into a space of zero volume,
lim (volume -> +0) mass / volume = +inf
says that your density is now infinite.
Applying the GR formulas to black holes suggest that at the very center, you get infinite density, thus a singularity.
But it is well known that the GR formulas don't apply at very small scales, and if a volume of zero doesn't qualify as "small scale" then I don't know what does.
It is not yet fully understood how QM applys in this area (mainly because there's no QM theory of gravity yet, and gravity is kind of important in black holes), but IIRC I read some articles that used QM to say: "We don't know what it looks like, but we can prove that it's not what GR says it is."
Joined: 3/23/2012
Posts: 296
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What i'm saying was that If a person is moving at a speed of light, does time slow down?
Is this different from my first question?
If its not , then a person's time doesn't slow down but instead he would die in 1 day.
Jungon wrote:
if I was to have a Tool-Assisted real life ... I'd..
I could abuse death, just to see if it saves time ..
What i'm saying was that If a person is moving at a speed of light, does time slow down?
A person cannot move at the speed of light. A person can move close to the speed of light, and time passes at different speeds at different frames of reference.
If a spaceship leaves Earth at a very high speed, travels for a time, then stops and turns back, and travels back to Earth, then more time will have passed on Earth than in the spaceship. If the spaceship could accelerate to near the speed of light, then the time difference would become quite significant. Eg. a person in the spaceship could experience one year and when he comes back to Earth decades or centuries could have passed on Earth.
Is this different from my first question?
I don't quite understand your first question. Please explain it in more detail.
Joined: 3/23/2012
Posts: 296
Location: In X position=50 y position=20
On my first question , If a person can spend a 1 sec like a year and if he runs , the observer would saw him moving at the high speed, right?
And if he dies on one day(observer's time) , I don't see any slow down
Jungon wrote:
if I was to have a Tool-Assisted real life ... I'd..
I could abuse death, just to see if it saves time ..
You know, I read your question and decided not to answer it for one reason: it was horribly worded, in such a way that "pie" would be just as reasonable an answer as any. You are doing it again.
Lets see:
What if person is able to spend 1 sec like 1 year for his own. (not for observers)
What exactly does this mean? Does it mean that the observer is moving such that every second from his point of view is equivalent to 1 year to another, "reference" observer? Or that every second for this "reference" observer is equivalent to a year for this person?
They are quite possible interpretations on your horribly mangled wording. Moreover, you don't specify what is the source of the difference between the time for one observer versus the other; is it different gravitational field? Is it one falling in a black hole while the other is looking? Is it them drifting apart from a common starting point, never to meet again? Is it them converging to a common ending point without having ever been on the same place before? Is it them meeting again at a common ending point after drifting apart for some time?
Because each of these is a completely different scenario and gives a different answer.
Edit:
On my first question , If a person can spend a 1 sec like a year and if he runs , the observer would saw him moving at the high speed, right?
So after a horribly mangled version, you post a less mangled one that is completely different from the original and think you are still talking about said original. This is different because you specify the source of the difference in time passage -- the relative speed.
The question still accepts "pie" as an answer, though. Do you mean that the person "running" is moving fast enough that time passes for him at the rate of 1 second for every year that passes for the "outside world"? Or do you mean that each second from the "outside world" is equivalent to one year to him?
In either case, the answer would still be "pie": do they start at a common location and eventually re-converge at the same location to compare? Because if not, both "yes" and "no" are valid answers for both questions, as the two scenarios are equivalent -- relativity of simultaneity means you can always find one observer that sees the person dying before the "rest of the world", and one observer that sees the "rest of the world" dying before that person.
Anyway: care to specify the question more?
You know, I read your question and decided not to answer it for one reason: it was horribly worded, in such a way that "pie" would be just as reasonable an answer as any. You are doing it again.
Please be civil. Relativity is a difficult subject; it can be difficult for those new to it to distinguish between questions which are meaningful but bizarre and those which are completely meaningless. An example of a meaningless and yet intuitively sensible question is "what speed is the Earth *really* travelling at?"
Your response is in general good: there is little else to be done than to point out where the question is meaningless or underspecified, and ask for clarification -- but use of words such as "horrible" and "mangled" can make this thread feel like a less safe place for people to ask questions.
Please be civil. Relativity is a difficult subject; it can be difficult for those new to it to distinguish between questions which are meaningful but bizarre and those which are completely meaningless.
I think it's reasonable to expect some effort to be put into making a question intelligible and understandable. The question in one's brain cannot be transferred properly to another, if the medium is a garbled mess of random words.
Marx is not a native english speaker,give him a break.
I'm not either.
I want all good TAS inside TASvideos, it's my motto.
TAS i'm interested:
Megaman series, specially the RPGs! Where is the mmbn1 all chips TAS we deserve? Where is the Command Mission TAS?
i'm slowly moving away from TASing fighting games for speed, maybe it's time to start finding some entertainment value in TASing.
Or that every second for this "reference" observer is equivalent to a year for this person?
Yes this one
Relativity says that when you move relative to someone else, time passes more slowly to you than to the "stationary" person. So this scenario is impossible to happen without an additional source of time dilation for the "moving" person. Meaning you deliberately picked the scenario that goes against the laws of physics and was surprised that the result was contrary to the laws of physics.
But in any case, Warp was (is) correct -- since a year passes for the "moving" guy for each second that passes for the "stationary" guy, the "moving" guy will die in a year for the "stationary" guy regardless of why time is passing faster for him than it should be.
grassini wrote:
Marx is not a native english speaker,give him a break.
I'm not either.
Joined: 3/2/2010
Posts: 2178
Location: A little to the left of nowhere (Sweden)
I watched a movie on TV today and figured one scene as completely impossible, but a friend disagrees with that. Neither of us can produce arguments that hold any kind of ground.
So here comes the question:
Assume the average modern sedan personal car, and a normal tire pressure.
Also assume said car is sinking in a sweet water lake.
Would it be possible to empty the air of the tires into 2 sporting bags (one for each side of the car), and use those as floatation devices to bring the car to the surface?
If someone can explain why this will (not) work, it would be appreciated.
Joined: 10/27/2004
Posts: 1978
Location: Making an escape
Let's see, doing a little googling here, making a few assumptions...
Boyle's Law is the key here. A cursory web search shows about 2.4 cubic feet internal volume per tire, so 9.6 cubic feet for all four tires. Typical tire pressure is 30 PSI gauge, or ~45 PSI absolute. Let's make things simple and assume the air is being released to atmospheric pressure, which is ~15 PSIa.
So:
45 PSIa * 9.6 ft^3 = 15 PSIa * volume of released air
This gives us 28.8 cubic feet of air when released out of the tire.
Next step is to apply Archimedes' principle and figure out how much water gets displaced by 28.8 cubic feet of air. We'll go with 62.3 lbs per cubic foot of water.
62.3 lb/ft^3 * 28.8 ft^3 = 1794.24 pounds of displaced water.
So, if my ballpark math is correct, that's only a little more than half of the water you need displaced. So sadly, in spite of your impressive efforts, your car is doomed to sink.
Please kindly correct me if I'm wrong about any of this.
Edit: Crap, I forgot to add in the water displaced by the car itself. But I'm tired, and I'm not terribly sure it'd work.
A hundred years from now, they will gaze upon my work and marvel at my skills but never know my name. And that will be good enough for me.
Assume the average modern sedan personal car, and a normal tire pressure.
Also assume said car is sinking in a sweet water lake.
Would it be possible to empty the air of the tires into 2 sporting bags (one for each side of the car), and use those as floatation devices to bring the car to the surface?
The idea behind it isn't completely unfounded. After all, take a filled air tank (those used in diving) and throw it into water: It will sink like a rock. Release its air under water into some kind of balloon of sufficient size, and it will be able to lift the tank back to the surface.
The problem is, of course, that a car weighs slightly more than an air tank, and car tires probably don't have as much air than such a tank (nor is it even nearly as compressed). Probably not even near enough.
The top is, obviously, labeled positive, with the bottom being negative. If I understand correctly, are we saying that, when we put a load between the top and the bottom of this battery, that electrons flow from the bottom to the top?
