immijimmi

I'd like to learn about this, but the wiki page is incomprehensible to me. From my understanding, this explains how energy can exert a gravitational pull (along with a lot of other factors). Can someone explain how that works to me? I'm currently learning AS physics so I don't have much of an understanding of any complex ideas... keeping that in mind please don't overcomplicate it, or introduce any theories I won't understand without explanation.

Thanks in advance!

The interaction between nucleons has a finite range. The interaction between quarks does not drop off. The former is a residual effect of the latter.

 

http://en.wikipedia....ong_interaction

 

 

 

Any quark you create is bound to at least one other quark. You will never have a single quark.

My apologies, I mistook attributes of the residual strong force as effective on both types.

I have an interesting thought experiment related to this topic, however: In the event that tachyons exist, would a tachyonic quark be able bind with bradyonic quarks into a composite particle if it was to orbit the other quarks at superluminal speeds?

I understand, that when particles "interact", they have "detected" & "measured" each other, quantum mechanically, i.e. "interactions" cause wave-function "collapses", into eigenstates, of the interaction force (EM/W, S). Apparently, the eigenstates, of the EM,S interactions, are the "canonical" or "mass" eigenstates, e.g. m_e = 511keV. However, the eigenstates, of the W interaction, are special "weak" eigenstates, which are "mixtures", i.e. quantum super-positions, of the canonical mass eigenstates. Vaguely, [math]d_W \approx 0.97 d + 0.22 u[/math]; and [math]\left(\nu_e\right)_W \approx 0.9 \nu_1 + 0.5 \nu_2[/math].

 

Note that the neutrino mass eigenstates, [math]\nu_1,\nu_2,\nu_3[/math], should be depicted on the SM table of particles, to be consistent, with the other fermions, listed according to their mass eigenstates. However, b/c neutrinos only interact weakly, they are only generated into Weak eigenstates, whilst their pure mass eigenstates are not directly observed -- observing neutrinos requires them to interact, which requires the Weak force, which "collapses" all emerging neutrinos into Weak eigenstates. So, logically inconsistently, the SM table of particles lists every other fermion, according to their canonical mass eigenstates; but lists neutrinos according to their "Weak flavors", i.e. Weak eigenstates, [math]\nu_e, \nu_{\mu}, \nu_{\tau}[/math].

Maybe I should wait until I understand particle physics more before I attempt to venture into this particular topic...

Actually I have a whole nother realm of a question:

 

If a photon hits an electron and get's re-emitted and head's towards an observer, is the location of where the photon hit the electron "recorded" within the photon, or is the location that we measure the electron at uncertain within the photon that we measure?

In other words, is it predetermined where we will measure an electron at within a photon?

...What? The reason we see things which photons have bounced off is that the photons that are not absorbed are of a specific frequency or frequencies, which gives us the colour of the object. Put all the photons that enter your eyes together and you get an image. The photons that reached us don't carry an image of the incident. They won't have changed at all. We can't measure anything from this lone photon you're talking about unless we know some other details of the incident. (for example, we could measure when it happened if we knew where, by calculating distance/speed).

I was gonna put a post here about how it's impossible to measure a 0 in motion because it would mean inertia compared to everything else, and that we should be focusing on a zero in temperature. However something just ocurred to me: physicists used to think that motion was relative to the universe itself, right? Well, we know that light is always moving at c. To maintain this constant speed it cant really be moving relatively to anything, can it? We also think that it appears to move slower at times to to gravity, etc. curving spacetime around it. We've applied this to how black holes absorb light. If it appears to slow down when crossing an area containing a different 'density' of spacetime, then it's moving relative to that. In light of this, why aren't we measuring motion relative to the fabric of spacetime? that would mean that you have to take into account movement compared to this substance (if it can be called a substance) as well as temperature, if you want to stop an object's time.

Or you could just flood the area with gravitons.

Found it!! It isnt helicity because they don't travel at c so it's technically a variable. Apparently it's chirality. I had to look in the wiki page for sterile neutrinos to find that gem, though.

Credit to DrRocket for the original suggestion of chirality though.

Might gluons have mass ? If so, then only EM photons would be mass-less, i.e. massive force-carriers would be the rule, not the exception. By what means do experimenters conclude, that gluons have no mass ?

 

 

 

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I understand, that "what is so special" about the Weak interaction, is that its eigenstates are not orthogonal, to those of (all?) the other interactions, i.e. the Weak-mixing angle. I cannot explain "why" that is so, but I understand that that is "what" differentiates the Weak interaction, from (all?) the others.

This sounds dense of me, but is there any way you could explain that to an AS physics student? I dont know what the 'weak-mixing angle' or 'orthogonal' mean, and i'm not sure what the intended meaning of 'eigenstates' is in that context. If something has an eigenstate that means that you know the exact values of its quantum numbers. How do you apply that to a force? (I'm quite new to eigenstates too actually so correct me if that last was wrong)

The singlet state is identified in the link I provided — the symmetric superposition of the three color/anticolor pairings.

Ok, but that still leaves six other observed states and not 8.

And, if r /r = colorless, which it does, why do I have to involve b /b and g /g? (as an example)

I understand, that the "singlet" gluon amounts, in effect, to an "all white (& anti-white)", i.e. "color-less" gluon, having no forceful effect what-so-ever:

 

[math]g_s \approx g_{\bar{r}r} + g_{\bar{y}y} + g_{\bar{b}b} \approx g_{\bar{W}W} \approx g_{BW}[/math]

Could such a Strong-force "color-less", "black-and-white" gluon be compared, to a Weak-force "neutral current", i.e. [math]Z^0[/math] ??

 

 

 

I understand, that when gluon bonds "break", they "rip" at the "juncture" between their color & anticolor, creating a new quark & antiquark, having those color & anticolors:

 

[math]g_{\bar{r}r} \rightarrow \bar{q}_{\bar{r}}'q_r'[/math]

I understand, that the new quark & antiquark become bound into new hadrons:

 

[math]q_r : g_{\bar{r}r} : q_y q_b \rightarrow q_r \bar{q}_{\bar{r}}':q_r' q_y q_b \rightarrow q_r\bar{q}_{\bar{r}}'+q_r' q_y q_b[/math]

The resulting meson [math]q_r\bar{q}_{\bar{r}}'[/math], is a pion, which "burps" from one baryon, to a neighboring baryon. The residual Strong nuclear force seems to stem, from the stressing & breaking, of intra-nucleon gluon bonds.

How is gluon fission relevant to whether quarks have color charge at creation? I mean, sure, you're showing how quarks with c-charge can be created from a gluon, but that already has color charge to pass on. I'm pretty sure that quarks have color charge from creation, but I wasn't sure.

The interaction between nucleons has a finite range. The interaction between quarks does not drop off. The former is a residual effect of the latter.

 

http://en.wikipedia....ong_interaction

From the Wiki page:

The strong interaction is observable in two areas: on a larger scale (about 1 to 3 femtometers (fm)), it is the force that binds protons and neutrons together to form the nucleus of an atom. On the smaller scale (less than about 0.8 fm, the radius of a nucleon), it is also the force (carried by gluons) that holds quarks together to form protons, neutrons and other hadron particles.

Strong interaction isn't observed after 3fm, like I said, so we don't know from this information if it has any effect past this distance.

I know i've read somewhere that gluons have mass and was .14 MeV.

Regardless of whether they do or not, there is actually another explanation for the limited range of the color force:

http://en.wikipedia.org/wiki/Gluon

Scroll down to 'confinement' and read.

Everything is made of energy. When things release photons it is because photons are made of energy and not much else, therefore they are easy to create as an outlet for spare energy. One reason photons can't be the fundamental constituents of matter would be that they don't have color charge, electric charge or mass, and most components of matter possess these qualities.

I dont get why everyone separates these behaviors. As I see it, all matter behaves as wavicles. They can exhibit both properties at once, and the nature of observation determines which behavior we see.

The problem I have is that kinetic energy is a frame dependent notion.

 

For example, go outside and pick up a rock. Hold it steady. What is the kinetic energy of this rock?

about 288K? When he refers to kinetic energy having an effect on time it isnt necessarily net movement. The rock is vibrating in your hand but not to a noticeable degree. Temperature is to movement what distance is to displacement, I suppose. If I kick a ball 5m into the air and it lands where i kicked it from, distance travelled is 10m but displacement is 0m. If you hold a rock steady in your hand, its movement is 0 but its temperature (and therefore kinetic energy) is quite a bit more.

1. Weak interaction is the only method by which strangeness and CP can be violated. What's so special about it that it can do this?

2. The only gauge bosons that have mass are both associated with this force. Is that significant?

Anyway, you should not think of spin as anything to do with spinning in any classical sense.

But the wiki for spin in particle physics says:

'Spin is a type of angular momentum, where angular momentum is defined in the modern way as the "generator of rotations"

I'm confused... >.<

The gluon singlet state is not observed, leaving you with 8.

http://en.wikipedia...._singlet_states

So, the gluon singlet state is a 'colourless' gluon? There are 3 of those, though... that means there are only 6 combinations:

r /b

r /g

b /r

b /g

g /r

g /b

The three that wouldn't be observed are:

r /r

b /b

g /g

So, why are there 8 observed?

I'm not sure how you could determine that; I can't think of a way to time tag an event that produced them, and the speed differences are exceedingly small. But scientists are clever so if you have a link I'd like to read about it. The detection of neutrinos (e.g. from SN1987a) is also indeterminate, because it takes a little time for the photons to make it out of the supernova so the neutrinos arrive first. But that gives you some information; SN1987a was 168,000LY away, and the time difference was a few hours. If you know the time delay of the photons you could get an approximate speed of the neutrinos. I think you're looking at roughly a day out of 168,000 years, or a part in 10^8.

sorry, i dont have a link. I think i heard it in a documentary about the neutrino research at SNOLAB.

People are saying it's useless because there's no energy gain, but isnt it an alternative to electricity-powered planes? Plus, you're using greenhouse gases to make the HC in the first place so no net pollution! Basically, It means keeping fuel-powered engines, but with the benefits of electicity.

Actually, I do not believe in the" evolution theory"; since the anatomy of our eye is the same as the one of a human lived 10000 years ago. So "evolution" has nothing to do with this topic.

Sorry, I have to butt in here against my better judgement to say that evolution is slightly more than a theory, to put it lightly. For some reason science differs from other subjects and disciplines in that its 'theories' are backed by evidence. We have discovered fossils for practically every possible evolutionary stage from caveman to modern-day human, for example. And yet, some people refuse to believe that this means anything because they are ignorant of the facts. I don't like ranting, and I certainly won't force beliefs on you, but please, please look at the information available before you make up your mind. Also, according to evolutionary theory the anatomy of our eyes has changed over time significantly, so it is relevant.

I dont know where you got the quote from, but strong force has no strength over 3 fm. Otherwise, we'd be seeing some rather large hadrons forming, granted enough quarks or energy.

Gluons aren't suppose to have mass

Eeeeeh, it depends. We aren't sure (where ARE we sure?) but most of the evidence points towards gluons having around 0.14 MeV (either MeV or eV) of rest energy. Like I said before, they must have mass to explain the 3 fm limit of the strong force.

Also, you can't disregard the extra quarks created by the energy input. The problem is that the quarks that ae created will bond with the original, thus further preventing isolation.

1. Are quarks created with a specific color charge? For example in pair production a red up quark and a cyan antiup quark?

2. Why are there only 8 colour states for gluons? There are nine possible combinations of colour to 'anticolour'.

3. If there were only blue and red quarks but no green, would the strong force still have an effect and be able to bind quarks into hadrons?

4. Why is the strong nuclear/residual force transmitted by virtual pions, and since that's possible does it mean that all composite particles that have an integer spin (bosonic) can transmit a force in such a manner? (i.e. atoms such as helium 2)

If you know the answer to one and not the others just answer that one.

Agh, I give up on this one until university. Too many conflicting answers :/

You apparently did a bit of research. But you are not questionposter and you did not question the use of wiki articles in providing an explanation.

 

The mass of neutrinos is thought to be exceedingly small. It is only because of this mass, which as you note is required for neutrinos to oscillate between types, that they do not travel at c. Prior to the discover of the neutrino oscillations particle physics texts treated the neutrino as massless, traveling at c. I am not aware of any experiments that have actually measured a neutrino speed below c, and in fact there is one that purports to have evidence of superluminal travel by neutrinos (though I think most people expect that there is a mistake somewhere).

 

The difference between particles and anti-particles lies in a change in sign of certain quantum numbers -- charge and chirality.

 

Assuming that neutrinos are indeed massive, chirality is not the same as helicity.

 

That is the "true physical difference" between a particle and an anti-particle.

Thanks, that's all the answer I needed.

You're right that neutrinos have very small mass, electron neutrinos have less than 3 eV in rest energy.

Haven't neutrinos been observed at just under c coming from the Sun, though? I'm sure i've heard that somewhere.

If all atoms have the same energy levels, as in the electrons in the ground state electron in lead wouldn't be closer than in hydrogen, and those energy levels can absorb only specific energies of light, why are there many different shaped orbitals?

Firstly the different atoms dont necessarily have the same energy levels as each other. Proton count in lead is higher so the inner electrons would be closer. But that's irrelevant to the question. There are different shapes of orbitals because of the different relative energy levels of the electrons in that atom. For example carbon. It has 6 electrons. The first two are the closest so they have the lowest energy level. These inhabit a sphere shaped orbital. The next two electrons do the same, but farther from the nucleus because the inner electrons repel them. The last two inhabit a different shaped orbital: this one has a dumb-bell shape. The different shape is due to the fact that these two have more energy and so are confined to the atom differently. I don't know enough about it to go much further than that, but I hope I answered a few of your questions.

immijimmi.When you say "I really don't understand what you mean now".The point is it's just a model of what is known.The reason that billions of pounds is being spent on particle accelerator experiments is because nobody really knows for sure.That's my understanding of the situation,please correct me if I am wrong.

 

And your thread has gone from virtual photons to photons.You started the thread with virtual photons.

Why has it gone from virtual photons to photons?

Okay, here's why i'm confused. My teacher for AS physics informed me that in an EM interaction between two electrically charged objects (such as the north and south pole of a magnet, or an electron and proton), virtual photons pass between the two along the lines shown in that diagram. In repulsion, the virtual photons are recieved and given along the direct routes which causes the movement of the objects away from each other. In attraction, the virtual photons are recieved and given in a looping path that goes from the 'back' of one object to the 'back' of the other, which causes movement of the objects towards each other. My initial question was why the virtual photons looped around in such a way, but it appears either I have been misinformed or I have phrased my question badly.