Ask any question you want about Physics

originally posted by: Diablos
By the way, as I've started up my self-studying of QM (more like a review of my notes so far), I have a quick conceptual question.

1. Is it correct to interpret the momentum space wave function Φ(p,t) as the projection of the position-space wave function onto eigenstates of the momentum operator? If not, how do you physically interpret it and the inner product:

Φ(p,t) = ⟨fₚ|Ψ⟩

Where fₚ is the eigenfunction of the momentum operator with eigenvalue p.

Well in QM we can make this representation with superposition.But yes it doesnt matter if you choose the eigenfunctions of the position operator as a set of basis functions then we have a state as a wave function ψ(r) in position space. This is well scrodingers equations with what your doing here its more used in harmonics but than again theirs really not a question here only part of an answer.

originally posted by: Phage
a reply to: dragonridr

But with all the advancements in science just think what the next hundred will bring.

Cool stuff?

This might be an opportune time to point out, once again, that although we don't know everything (or even close to it) it does not mean we don't know anything.

Yes good point we have learned alot about what isnt happening in the universe through experiments and alot surprised us about what we know to be occurring. Now we are working on the why.

a reply to: Arbitrageur

Yes, I'm aware of the expanse of universe that we don't have a grasp on- and it's a large amount, as it should be considering how insignificantly small we are.

I'm more interested to know what certain circles of physicists think the universe is in it's totality- not necessarily what it is comprised of or the mechanics of it. I get that this probably delves more into philosophical notions, but I have to imagine there are conversations, based on what they know and are currently researching, about what this thing is.

a reply to: PhotonEffect

I'm more interested to know what certain circles of physicists think the universe is in it's totality-

Ever watch a bunch of hyper kids in a mirrored funhouse?

originally posted by: PhotonEffect
a reply to: Arbitrageur

Yes, I'm aware of the expanse of universe that we don't have a grasp on- and it's a large amount, as it should be considering how insignificantly small we are.

I'm more interested to know what certain circles of physicists think the universe is in it's totality- not necessarily what it is comprised of or the mechanics of it. I get that this probably delves more into philosophical notions, but I have to imagine there are conversations, based on what they know and are currently researching, about what this thing is.

Id say the most common is that we must live in a frothy sea of multiple universes. Some of the earliest models of inflation say that before the big bang, space-time contained what’s known as a false vacuum, a high-energy field devoid of matter and radiation that is inherently unstable. To reach a stable state, the vacuum began to bubble like a pot of boiling water. With each bubble, a new universe was born, giving rise to an endless multiverse.

a reply to: dragonridr

I talked to a leading astrophysicists about this point. The common hypotheses is that there are different universes which 'froze out' into various vacuum minima of the fundamental fields, but that the identity of the fundamental fields are the same as is the basic structure of Standard Model interactions in all of them. Effective masses, strengths and mixing angles could be different, the things which appear to be governed by chance.

Hay quick question.

I heard from a physicists, think it was Lawrence Krauss. He said that when scientists say the word 'Fundamental' what they really mean to say is that they dont know, but instead of saying I dont know they say its Fundamental.

Pretty sure it was Lawrence but cannot find were he said it. Could have been another physicist. Was def one of the
famous scientists as I wouldnt have believed them.

Have you heard this saying? well not a saying as ive only heard it once.

Coomba98

originally posted by: mbkennel
a reply to: dragonridr

I talked to a leading astrophysicists about this point. The common hypotheses is that there are different universes which 'froze out' into various vacuum minima of the fundamental fields, but that the identity of the fundamental fields are the same as is the basic structure of Standard Model interactions in all of them. Effective masses, strengths and mixing angles could be different, the things which appear to be governed by chance.

Exactly meaning that nothing is truly random and universes actually occupy the same space.

a reply to: coomba98
So Lawrence Krauss and I actually agree on something? Just kidding, I agree with him about a lot, like his skepticism though not complete rejection of "string theory", etc.

I'm not sure if I ever heard Krauss say that, but I know I've said it, on page 34 and probably again later in the thread:

www.abovetopsecret.com...

originally posted by: Arbitrageur
When you see the word "fundamental" in physics, it often means that we don't know any deeper explanation for the observation, yet. We can say mass "bends space-time" but beyond this we don't know exactly why this happens so we call it a "fundamental" interaction.

Several properties of the electron are "fundamental", like mass, charge, spin, and we don't really know exactly why those have the values they do. Someday we might and then they won't be called "fundamental" anymore, but something deeper will probably take its place and that will be called "fundamental", is my guess.

To elaborate on that point a little bit more, at one time in the past, we didn't know that the proton was made of anything smaller, so the proton could be called a fundamental particle in that case. But now that we know the proton is made of smaller components like quarks and gluons, we tend not to think of it as fundamental, like the electron.

So we've got fundamental interactions, fundamental particles, and fundamental constants for which we don't have any deeper explanation, but as the proton example shows, just because something was fundamental in the past doesn't mean it will always stay that way.

a reply to: dragonridr
a reply to: mbkennel
I was afraid of where that question might lead, such as some philosophical nonsense or even that "holographic projection" or matrix stuff, but I'm glad to see it didn't go that way and I like your answers. I brought up the multiverse concept myself back when we got the question about "what is the universe expanding into?", that we don't really know if there could be other universes beyond ours and out ability to observe, but if there were, I wouldn't rule out that some might bump into each other if there were several, and they were all trying to expand. But this is not only unknown, it's probably also unknowable.

a reply to: Arbitrageur
The only answer to this question - that’s bothered me for ages - has to be centered in physics. At least I hope!

Here goes: I’ve been to a couple of hit and run accidents. What haunts me to this day is what’s left. In the road. Their shoes.

First time - it was a pair of fluffy pink ladies, old lady's slippers. An elderly woman was hit walking across the street to the market. She was struck and thrown over 20 feet - yet her slippers staid exactly at the impact point. They couldn’t even have weighed but a few ounces.

Second time - it was a pair of sneakers - tight laced (I checked) - that remained at point of impact when the young man was thrown almost 30 feet. It’s like they were super-glued to the pavement.

It just makes absolutely NO sense to me - none. How can people be blown right out of their shoes? And the shoes stay - right there at the impact sight. *Shakes head* - It really does not make any sense at all. I mean - well, I don’t know what I mean that’s why I’m asking you.

How can it by ’physics-ly’ possible? I know it is - I just don’t understand how.

Thanks tons!

gracie

a reply to: silo13
Interesting question, and you're right, the answer is in physics.

Every accident seems to be unique, so I think it would be a mistake to give any blanket answer and say that's what happens in accidents generally. I'll talk about what I've seen and analyzed using some examples in a minute, but first let me comment on your two cases.

The slippers coming off shouldn't be surprising since they aren't firmly attached (they're named slippers because they slip on or off so easily, right?), so I'd actually be more surprised if they stayed on the feet after a severe impact.

The tight laced sneakers are more interesting, but I assume they weren't "high tops", because tight laced high tops probably won't come off, and tight laced regular sneakers certainly can. How? You can remove laced sneakers in some cases by dragging your feet backwards (or if an impact causes your shoes to be dragged against the ground with some downward force).

Here's a video that has nothing to do with a car accident showing what appears to be tied shoes coming off from dragging the feet backward during a boxing session, and it is something along the lines of this effect which seems to be more likely to remove the shoes in the accidents I've reviewed, as opposed to being "knocked out of" tied shoes, which the evidence doesn't support:



Let's look at some accidents. Here's one where I think the shoes were "peeled off" because there was some downward force on the legs/shoes, in addition to the lateral force of the impact:



It's interesting to note that the shoes end up not far from the point of impact and don't follow the body, and this I suspect is the result of friction between the shoes and the pavement. It also looks like maybe his feet played "tiddly winks" with the shoes, resulting in them getting airborne and actually moving maybe a foot or two in the opposite direction as the body. Did you ever play with tiddly winks and get them to fly up like that man's shoes? Note there's a witness in the top of the frame who I suspect might make a conclusion similar to yours where the shoes were found near the impact point, while the body was knocked forward, but as you can see, the shoes were actually anything but "super-glued to the pavement" as you put it. The witness probably didn't see the initial impact but only the aftermath, which happens a lot in accidents, so they might also conclude that the shoes didn't budge when he/she didn't really see exactly how the shoes ended up where they did.

Here's an example of shoes that are secured well enough to withstand the impact from the car, but then a shoe comes off after being subjected to impact and friction with the pavement as he is dragged backward by his momentum:



I think that's probably one of the best videos I've seen, to show what can actually remove a shoe that is somewhat secure. It's also interesting that only one shoe comes off. The shoe that impacted first probably impacted harder than the other shoe and maybe that's why it came off while the other one apparently stayed on.

Another example of where the shoes don't come off at the impact point because they aren't dragged across the ground, and even if they were, it's not backwards or sideways. Dragging the shoes across the ground forward probably won't remove them, but this guy is knocked in the air and it looks like his shoes stay on.



By the way, I think that video illustrates why we are supposed to walk on the shoulder facing traffic, because this is what can happen if you walk on the shoulder with traffic; you have no warning to get out of the way.

Another example where the shoes stay on after a fairly severe impact, because his shoes don't get dragged across the pavement, rather you can see his feet actually go airborne and make a clockwise circle as he does a flip. Also the fact that the shoes aren't sneakers but are made of stiffer material I suspect would be a factor making the shoes more difficult to remove:



Anyway it's a little easier to figure out what happened in cases with video evidence, compared to cases where all we have is a verbal description of the aftermath where it's difficult to piece together exactly what happened.

a reply to: Arbitrageur
Thank you for the time and the answer. And yes, the 'slippers' make more sense - but the sneakers (which were not 'high-tops') were left right there - at the point of impact - that's what gets me - at the point of impact - side by side like he was just 'blown' out of them.
It still gets me.
Thank you -
peace

originally posted by: dragonridr

originally posted by: mbkennel
a reply to: dragonridr

I talked to a leading astrophysicists about this point. The common hypotheses is that there are different universes which 'froze out' into various vacuum minima of the fundamental fields, but that the identity of the fundamental fields are the same as is the basic structure of Standard Model interactions in all of them. Effective masses, strengths and mixing angles could be different, the things which appear to be governed by chance.

Exactly meaning that nothing is truly random and universes actually occupy the same space.

No, that's not right. The 'popping' into new universes is probably random and they don't occupy the same space, by definition.

originally posted by: mbkennel

originally posted by: dragonridr

originally posted by: mbkennel
a reply to: dragonridr

I talked to a leading astrophysicists about this point. The common hypotheses is that there are different universes which 'froze out' into various vacuum minima of the fundamental fields, but that the identity of the fundamental fields are the same as is the basic structure of Standard Model interactions in all of them. Effective masses, strengths and mixing angles could be different, the things which appear to be governed by chance.

Exactly meaning that nothing is truly random and universes actually occupy the same space.

No, that's not right. The 'popping' into new universes is probably random and they don't occupy the same space, by definition.

If we are talking about multiple dimensions, then the Universes would quite literally occupy the same space but because the rules, constants, and variables of nature may be different, we can not see it or interact with it, but it is there. and it would occupy and make up the same space the we exist in. In string theory an even stranger concept occurs. The implication here is one universe would be formed in its entirety and an instant later a second universe would be formed in the very same space-time. The laws of physics could be different in these two universes depending on the elementary particles formed by the string oscillations. The only common thing linking these two universes is they both occupy the very same space-time but not simultaneously. Then, another instant later a third universe would be created where the second one had been, and so on until the cycle starts over by creating the first universe again.

Each time our universe is recreated some of the string characteristics would have been changed, as the vibrational energy moved across the membrane, over time while forming and dissolving the other universes. While our recreated universe would return with slightly changed string/particle parameters, from when it was last dissolved. We would have no information of what happened during the time period where our universe did not exist to cause these changes. We are already seeing such unexplained effects in the laboratory, such as how an electron’s location skips around in its orbit. Meaning things like virtual particles arent popping in and out of existence we are meaning the universe flipping through different versions of the universe. Much like drawing pictures and flipping the pages we see it as motion. In actuality is just varying energy levels on an 11th dimensional membranes.

How is everyone doing lately ? Have you found any answers for the meaning of life, antigravity, et ? No ? Nothing ?
Well fear not..i is here...with an all important question that will get us closer to being a space traveling bunch of highly trained apes.
Step 1 : build Dr. Li's superconducting-disc-machine-field-generating-anti-gravity-that's-not-anti-gravity.
Step -1: figure out what she means by ''time varying magnetic field'' cause this is use to spin the ions in the superconductor disk.

So does anyone know what it actually means ? time varying magnetic field ? is it just a fancy name for an electro-magnet with a power adjusting dial ? It seems that by spining all the ions, they line up theyr micro electro garvitic thingy , all perpendicular to their spin axes(quadrillions rev pe second, and this creates a bose-einstein condensate, with the final effect that you get the combined micro gravitic effect from the spin of all the ions, as if it was one massive ion...aparently relativity says this gravitic thingy is present where ever there is energy and mass or mass and movement or something like that...so these tiny guys, the ions definately generate tiny tiny gravitic fields by spinnind at 1-4 quadrillion? times per second.
Anyway..anyone knows how to build a time varying magnetic thingy ?

a reply to: Choice777

Back in grade school I remember reading a simple thought experiment about relativity.
They asked what would happen if overnight while we slept everything including the rulers we measure with expanded in size by the same amount?

In the macro world there might not be much evidence but what about the quantum world where the rulers might be in some kind of "ground state".

Elementary particle/wave interactions might not be able to expand uniformly in an analog manner.

Sprawling on the fringes of the city
In geometric order
An insulated border

Maybe the universe crystallizes like glass?

originally posted by: [post=18778896]Choice777 Anyway..anyone knows how to build a time varying magnetic thingy ?

In a way, yes, but may not be magnetic

originally posted by: Choice777
Anyway..anyone knows how to build a time varying magnetic thingy ?

That part's easy. The hard part is to build the rest of it.

originally posted by: Choice777
So does anyone know what it actually means ? time varying magnetic field ?

Here's a youtube video of someone making a time varying magnetic field called a "stirrer", by rotating a hard drive magnet.



Li apparently used a rotating type II YBCO superconductor (instead of a hard drive magnet) as described in this paper:

Static test for a gravitational force coupled to type II YBCO superconductors

As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (∼ 10−6 g cm3). Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating type II, YBCO superconductor, with the percentage change (0.05–2.1%) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 10^4 was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field. Changes in acceleration were measured to be less than 2 parts in 10^8 of the normal gravitational acceleration. This result puts new limits on the strength and range of the proposed coupling between static superconductors and gravity.

Those are extremely small effects if they are effects at all and the criticism I hear most often about antigravity research is that the effects are so small that they could be due simply to experimental error.

However I do find it interesting that her 2001 DOD grant expired in 2002 without publishing the research and that her company apparently still exists in 2014. While this may inspire some excitement and speculation, I also recall that the Navy sponsored cold fusion research for decades without any publicly known useful results, so just because research goes on a long time doesn't necessarily infer it's bearing fruit. Anytime you're dealing with liquid nitrogen, and reporting small effects, the question of possible experimental error is raised.

In GR gravity to electromagnetic coupling is on the order of one part in trillions. that is why usually with experiments the sigma is so bad. this is why when Tajmar got results billions of times stronger than predicted by GR everyone was all aflutter. Tajmar subsequently retracted his paper because he became convinced it was an effect of the flow of his coolant in his test rig and not gravity coupling.

Though his retraction disappointed me i was relieved to see even the most cautious scientists plainly admitting gravity does couple to electromagnetism and its component forces and later via Zvi Bern; the strong force.