Skip to comments.Proton's radius revised downward - Surprise measurement may point to new physics
Posted on 01/25/2013 11:04:41 PM PST by neverdem
Only in physics can a few quintillionths of a meter be cause for uneasy excitement. A new measurement finds that the proton is about 4 percent smaller than previous experiments suggest. The study, published in the Jan. 25 issue of Science, has physicists cautiously optimistic that the discrepancy between experiments will lead to the discovery of new particles or forces.
Poking at small effects you cant explain can be a way of unraveling a much bigger piece of physics, says Carl Carlson, a theoretical physicist at the College of William and Mary in Williamsburg, Va., who was not involved in the study. And this case is particularly intriguing.
For years, physicists have used two indirect methods to determine the size of the proton. (Unfortunately, there is no such thing as a subatomic ruler.) They can fire an electron beam at protons and measure how far the flying particles get deflected. Alternatively, physicists can study the behavior of electrons in hydrogen atoms. They shoot a laser at an atom so that the one electron jumps to a higher, unstable energy level; when the electron returns to a low-energy state, it releases X-rays whose frequency depends on the size of the proton. Both methods suggest the proton has a radius of about 0.88 femtometers, or 0.88 quadrillionths of a meter.
That measurement was not in doubt until 2010, when physicist Aldo Antognini at ETH Zurich and his team developed a new technique to probe proton size. They also used hydrogen atoms, but replaced the electrons with muons particles similar to electrons but more than 200 times as massive. Muons additional heft enhances their interaction with protons and makes their behavior more dependent on proton size. After measuring the X-rays emitted by muons shifting between energy states, Antogninis team published a paper...
(Excerpt) Read more at sciencenews.org ...
What's next? Planck's constant?
It so a cook can't keep up with physics anymore.
Odd how this ‘measurement’ of the proton is very similar to our claims of the size, orbit, and viability of planets around other stars.
We can’t see the planets.
We only have light detectors that give us a reading of very minute dimming in the light, which we assume to be a planet.
Based on the length and extent of the dimming, we claim to know the planet’s size and orbit.
Amazing how continuously wrong we are about things we search for the truth.
Amazing how continuously wrong we are about things AS we search for the truth.
(that’s a sign I should go to bed. Goodnight all)
So ..... How long before they realize that it isn’t really there at all?
GPS is based on an earth centered concept... Not true, but it does get us within a few meters of where we want to go.
They will just come out with a Planck’s Constant Compensator to account for the difference.
It's a working theory. That's all we have. I gripe, but that's a good-natured swirly.
We see through a glass, darkly. I seem to recall someone saying that...
FReepmail me if you want on or off my health and science ping list.
FReepmail me if you want on or off my health and science ping list.
First: The Standard Model doesn't describe gravity, period.
Second: Physicists aren't desperate to "discover new physics." We're desperate to wring information out of experimental physics in new ways because the approach of reaching ever higher energies in our accelerators is simply not viable. We can't even get within orders of magnitude needed to investigate most speculative theories in high energy physics, and there is no prospect for doing so in sight.
We need new experimental results and we just aren't getting any. Hence micro-measurements of the difference between c and the speed of neutrinos in vacuum or anomalous results like this start to look intriguing. They seldom turn out to be anything but experimental artifacts.
And no, we aren't changing Planck's constant. In fact, in the new SI proposal, Planck's constant, the electric charge, Boltzmann's constant, and Avogadro's number are going to be set as defined constants; they will never change. What will happen instead is that the basic practical units (second, meter, kilogram, ampere, kelvin, mole, and candela) will change and we will be looking for ever sharper definitions of the practical units in terms of the atomic ones, instead of the other way around as we did in the past.
High energy physicists and cosmologists have been doing that for a long time already. In their unit system ħ = (h/2π) = c = 1.
Question for Physics majors....
Is Particle Physics built on the idea that EVERY similar particle in the universe has EXACTLY the same weight, dimension, and charge as every other similar particle?
Or, is there some level of acceptable deviation?
Only the Japs could possibly make a caliper that small.
In a quantum mechanical Three Card Monte Game, you cannot be cheated, because all three cards are the same, and all three cards occupy all three positions at the same time.
And one of those times, it turned out the dishwasher was twins that were switching out when I was expediting.
SC - In case no one informed you of this new science post.
The reason is that in classical physics, when you reconstruct a person out of all of the constituent leptons and quarks, it is not the same person, because even though the particles are the same mass, charge, density, and so on, it's still possible to say the reconstructed person is nothing more than a very precise clone.
But in quantum physics, if I have two leptons (electrons for example) or two down quarks and an up quark (neutron, for example) those particles are in a much deeper sense identical: there is no physical experiment that can "label" two electrons as distinct particles in a two electron system. There is no electron-1 and elecvtron-2. There is just "two electrons."
So (his argument goes) when God reconstructs a person from quantum particles (all questions of whether he has a soul or not aside), it isn't just a perfect identical twin. It is literally the same person.
It’s a fundamental asymmetry in the universe: I, on the other hand have had to cook quite often.
2 before breakfast...or at least before the week ends. BAM!!!
Remember the blog about quarks? I figure that’s next up.
I realize that the natural world obeys different laws than the atomic world.
However, given the proper tools, would man ever be able to construct, say, one ball bearing that was absolutely identical to a second ball bearing?
You answered my next question before I asked it!
I assume the same rules apply to human beings and ball bearings?
The requirement that every diameter even of something weighing on the order of as little as a gram must be the same to within 1 atom is literally an astronomically difficult requirement.
A ball-bearing the size of a BB pellet has on the order of 10^21 atoms. If you started counting those atoms now, it would take you north of 100 trillion years just to account for them all. That is about 1000 times the age of the universe. Machining a 1 gram ball-bearing to within an Angstrom (which is around the size of an iron atom) on every diameter? Possible in pure principle. Impractical in every sense.
And actually that is the way most high energy guys think about quantum particles: As entities which contain state information whose changes must obey probabilistic rules.
Naw, they will just dub something as the "Dark Planck's Constant" ... that 'dark' nomenclature let's 'em explain anything ;-)
Well, your 1st person experience with that over enough time, I suppose, is inevitable. So would be reincarnation and anything.
It really is meaningless, the odds of it just ‘happening’ per person is like hitting the lottery every time from begining of the universe until the end, and then some.. Each time if they ran it per microsecond.
But it’s nice to think about the odds of that. *if* the universe is infinite, it’ll happen inifitely many times. My belief is the universe is finite though, but amazingly huge heh.
This is a relatively minor change, but it’s still exciting to me. Accuracy of this sort is very important.
or, perhaps, way beyond the limits we can measure today each lepton is different in some minute way so only God can resurrect the same person since only God will know which ones to use!
Yeah, I guess we'd better just give up and go back to living in caves.
Amazing how, as we search for the truth, our understanding of the Universe is continuously improved - as demonstrated by our continually advancing technology.
Today, the radius of the proton has been revised downwards, by 4%, from 0.88 femtometers. A hundred years ago, Ernest Rutherford had just discovered the atomic nucleus.
A hundred years hence? It boggles the imagination.
Dr. McCoy might have a problem with that.
There certainly is a lot of room for interpretation in the exoplanet data. Observational changes resulted in the Hubble Constant itself being off by about an order of magnitude. With in recent times it becoming possible to get peer reviewed papers published questioning if the Hubble constant is even correct, naturally a non majority view but apparently sane enough to be published.
We are always “improving” or “advancing” in knowledge but we often lack the humility to realize the implication of that is that we are just as wrong today as our ancestors were yesterday, just in different ways and with more precision.
And real cynic might observe, that the rephrase of “Always correcting our beliefs based on new data” is “We are reliable because we are constantly changing our minds”.
In the end.... Now that I have discovered how to make my own hooch.... I don’t care to much who wins this debate :-)
I can’t tell when you’re joking.
Relax. The entire physical universe is an illusion. We perceive what we project.
Protons have been on a diet so that they will look good in a swimsuit this summer.
Of course, the ship's computer, which would crank along " ... working ... working ... " on calculations that my phone can perform instantaneously would never cut it calculating the state vector of a system of even a few atoms, let alone an entire human being. [And to be fair to the poor old gal, a computer would have to be roughly the size of the universe in order to calculate the state vector of a human being.]
Tipler's point was, if you know a person's state vector, you can create the person, because that's all a quantum mechanical system is. But only God is smart enough to do that.
Quantum indistinguishability is as well established as the fact that the earth is round. Not just exotic and still slightly controversial things like quantum teleportation require it.
It's well verified by the structure of atoms (Pauli Exclusion Principle), the properties of metals (Fermi temperature and conductivity, based on the fact that electrons are identical fermions), the properities of liquid 4He (Bose-Einstein condensation), most of the properties of light... All of these require quantum indistinguishability.
Use millimeters so you are closer to actual size. This would be using Euro's to determine our national debt.
To the degree we can perceive.
To the same degree that we can perceive that the world is round.
Fascinating link in a very interesting/humorous thread. Thanks, lneisone (and thanks for the ping, neverdem).
Music to read this thread by...