>>What exactly 'exists' in the Quantum Vaccum (If that is even the proper question to ask)?
It would be amazing to discover that this so-called vaccuum is actually filled with something, or a plethora of different things, which have a major bearing on how those things we DO perceive now behave. That's kind of what I was getting at when I compared reality as we see it to a shadow play behind a translucent screen.
It is filled with 'something,' so to speak. This is really one of the great triumphs of quantum field theory: it tells what we call the vacuum is really an incredibly complicated set of fluctuating fields. And, in fact, these vacuum fluctuations have a very real, noticeable effect on particles.
To greatly simplify, the vacuum is 'polarized' by particles, the same way ordinary metal can be polarized by a magnet. If you take a little piece of iron, it normally has no magnetization at all; it won't stick to other pieces of iron for example. But if you bring a magnet near it, the iron gets magnetically polarized and turns into a magnet itself, so it "sticks to" the original magnet! This is how magnets stick to a refrigerator, for example -- the fridge magnets polarize the nearby part of the fridge, and the two magnets stick to one another. It's also why most electromagnets are built around an iron core -- the electromagnet polarizes the iron in the center, which adds up with the electromagnetic's own magnetism to create a much stronger magnetic field. (Similarly, electric charges will electrically polarize materials surrounding them, but the polarization is opposite to the original charge, so it has the effect of making the electric field weaker.)
In a similar but much more complicated fashion, charged particles polarize the vacuum near them, which then alters their apparent charge. The effect of this vacuum polarization can either be to increase the particles' effective charge (as in the magnetic case above) or to reduce their effective charge ('shielding' them, as with electric case above.) By measuring this effective charge of a particle, and comparing it with the original "bare" charge, we can actually see the effect of the quantum vacuum!
Now you might object that we don't what the bare charge of a particle is, because we can't very well get rid of the vacuum after all, so how could we ever measure it? For most things that's true. But there's one exception: the magnetic moment (just think of this as magnetic charge, tho it's slightly different.) The magnetic moment of a particle comes from its
spin, which in quantum mechanics
must be either an integer or half-integer value: 0, 0.5, 1, 1.5, 2, .... (Spin has to do with how a particle looks from different angles, and it's straightforward to prove it cannot be anything other than these values.) So we know what the "true" bare value of the magnetic moment of a spin-1/2 particle, like the electron or muon, is: it's
precisely 2. (Actually this is what's called the Lande g-factor; to get the magnetic moment you have to multiply it by q/4m, but that's not important.) We can see how different this is from the measured "effective" value. And we can calculate how much the vacuum polarization should change it using quantum field theory.
This has been done, and the effect of the vacuum polarization has been measured to
amazing precision. I am not exaggerating when I say this is one of
the most precise experiments ever done in physics. The measured and theoretically calculated values of the magnetic moment for the electron are:
2.00231930437 (expt)
2.00231930435 (theory)
and for the muon:
2.002331842 (expt)
2.002331838 (theory)
Without the effect of the vacuum, they would be precisely 2. So the QFT calculations of the vacuum's effect are right to
8 decimal places!!! It's amazing.
There are many other ways we can see the effects of the vacuum, too. For example, we can collide particles together so they approach
very close to one another, so close that there's not enough space between for the 'shielding' effect of vacuum polarization to have its full effect. If they are close enough they will see each other's "bare" charges. We do indeed see this -- at very high energy collisions, the charges etc. of particles
change from what they are for particles further away from one another. We say that charge, mass, coupling constants and so on "run" with energy, thanks to the effect of the vacuum. This running of parameters is extremely important in quantum field theory.
And the vacuum acts in more fundamental ways, too -- for example, that's where (most) mass comes from. By themselves, electrons, for example, would be massless and so travel at the speed of light. The reason they don't is because of interaction with part of the vacuum (the vacuum Higgs field.) You can think of the Higgs vacuum as "clumping" around electrons and "dragging" them and slowing them around -- much the same way as a beautiful woman walking through a crowded room might be slowed down by people gathering around her to try and to talk to her.
One more way -- if the total energy density of the vacuum is nonzero (we don't know what it is) that would act as a sort of "dark energy" (or "cosmological constant") which would cause the expansion of the universe to accelerate. This is, in fact, just what cosmologists have discovered in recent years! But no one knows yet whether the dark energy causing our universe to expand faster and faster is caused by the vacuum energy or by something else.
complexPHILOSOPHY said:
I am fairly certain that our brains are composed of 10% neurons and 90% glial cells. I am also fairly certain that neuron's through out the body, 'encode' electrobiochemical messages which are transmitted or fired from the synapse of one neuron (the area which encompasses the axon, synaptic cleft and axon terminals) to the dendrites of another neuron. Whether or not local or nonlocal groups of neurons fire in patterns, I do not know. Although I am not an expert in bio/organic chemistry, I believe that peptides are involved in 'peptide synthesis' which is involved in the formation of amino acid's and proteins.
True. The way it normally works is that an electrochemical signal called the "action potential" propagates down the length of a neuron. The action potential is a spike in voltage, which causes
voltage-gated ion channels (think of them as doors in the side of the neuron which open when the voltage changes) to open up and let certain (sodium) ions into the cell. These incoming ions cause the voltage to increase even more, which opens more voltage-gated ion channels nearby, which further increases the voltage, and so on. So you get a constantly-regenerating pulse of voltage (and ion concentration) travelling down the neuron.
Once the pulse reaches the end of the neuron (the axon terminal), something different happens. There is a narrow gap, the synapse, between the end of the neuron and the next neuron. The action potential can't directly travel to the next neuron because of this gap. Instead, the neuron has a bunch of "messenger" molecules (called neurotransmitters) sitting around pre-made next to the synapse. When the action potential reaches the synapse, it causes a different set of voltage-gated channels to open up, and these channels cause the neuron to dump its neurotransmitter into the synapse. The neurotransmitter molecules then bind to receptors on the neuron at the other end of the synapse, which causes
something to happen. In the simplest case they just cause that neuron to fire an action potential itself. But they can also have more complicated effects, like making that neuron easier to fire, or making it less likely to fire, or changing the frequency at which it fires, or even causing a sort of 'learning' mechanism in it to kick in.
Anyways, the most common neutrotransmitter is called
glutamate, but there are many different neurotransmitters in use by different kinds of neurons -- GABA, acetylcholine, serotonin, endorphins, vasopressin, just to name a few. Some of these are "peptides" (another word for "proteins") and so are called
neuropeptides -- eg, endorphins, dynorphins, vasopressin, oxytocin, neuropeptide Y, and substance P, to name a few well-known ones.
Much of GG's info about "peptides" seems dubious or bogus. Neuropeptides are involved in cognition and emotion, certainly, and many drugs work by imitating various neuropeptides (or other neurotransmitters.) But they have no special connection with acupuncture or suchlike, they don't mean emotions are stored in the bodies' tissues, and they certainly aren't in your "chakras" for God's sake.
Well, this vacuum can be thought of as a 'pool of energy' filling the entire universe which is invisible in the same way the water in a transparent pond is. In order to see the water, you throw a stone in and waves ripple out. This is exactly how we 'view' the quantum vacuum, we perturb it using high energy magnetic fields. At this level, no physical matter exists, however, virtual particles and antiparticles appear and annihilate in plank time.
Actually we see the effect of the vacuum on any particle (of course it's usually not large so to see it precise experimental conditions are needed) not just on photons (which make up magnetic fields.) Physical particles are "ripples" on the quantum fields that make up the universe. The vacuum is simply the lowest-energy state of these fields -- clasically that would mean no motion, field strength, or energy at all, but in quantum mechanics there is some even in the lowest-energy state -- and the excited states have additional waves in the fields, corresponding to one or more particles.
Also, virtual particles exist much longer than the Planck time -- generally speaking, they will exist a time T=hbar/E, where E is the "extra" (or "missing") energy of the virtual particles. Remember that in a sense "virtual particles" are just a convenient way to think of the complex quantum field interactions that are really going on. As long as those interactions are sufficiently "weak," we can represent them as taking place by the exchange of these virtual particles (doesn't work well for strong interactions). Whether you think of virtual particles as "really existing" or not is a matter of personal preference.
While QM does invoke ontological status between waves and particles, it doesn't necessarily invoke mysticism. QM embodies the philosophy of Holism, the antithesis of atomism.
It CERTAINLY doesn't involve any sort of mysticism! Far from it. The connection between waves & particles isn't mysterious at all, though we often unfortunately make it sound so. In fact, electrons, photons, etc. are neither waves nor particles. Instead they are
quantum waves (or excitations of quantum fields, to be more accurate.) These quantum waves behave according to the rules of quantum mechanics (quantum field theory, to be more accurate) which are very complex and very weird but well-known. It turns out that in certain conditions, quantum waves act very much like regular waves. In other conditions, quantum waves act very much like regular particles. Sometimes they act like neither. This is what people mean when we say things are "both" particles and waves -- both are approximations and are each useful in different circumstances, though sometimes you have to use the full rules of quantum mecahincs.
I wouldn't say that QM is especially "holistic." True, particles can be entagled and correlated across vast distances in a bizarre manner. But the working philosophy of physicists studying QM/QFT/etc is still reductionism, still splitting things up into simple pieces and figuring out how each one of them works. In fact QFT is a fully "local" theory -- events cannot causally affect things far away except by sending them signals, which travel no faster than the speed of light.
Alphanumeric's list is a good one, though very fast-paced -- if you get through all that coursework in four years you are hard-core. I didn't take quantum field theory or GR until grad school and I'm no slouch. Anyways, the best thing to do is to look in your course catalog for the math & physics majors (or talk to profs/advisors in those departments.) There's usually a pretty standard 'track' that takes up most of your time through the first three years -- especially if you take both math & physics courses, which I highly recommend.
![:\](https://bluelight.org/xf/BL_Images/Orig_Emoji/wrygrin.gif "wry grin :\")
