anna v

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Retired experimental particle physicist

	26,776 reputation	bio	website		visits	member for	2 years, 5 months
21944 badges		location	Greece		seen	8 hours ago

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8h	comment	Measuring extra-dimensions what do you mean positive result? They see no deviation from newtonian physics.from abstract of your link " We improved previous short-range constraints by up to a factor of 1000 and find no deviations from Newtonian physics. "
10h	comment	Under what conditions is a pure fusion nuclear bomb possible? @dmckee Right . It is the ignition, further confinement designs would be needed for rapid chain reaction. I am just pointing out that the non Abomb solutions for ignition are too large for a bomb.
1d	comment	Best way to chill a cup of coffee with cold water and 5 minutes well I always use three ice cubes to bring my tea to drinkable temperature. takes 30 seconds.
1d	comment	Do small-angle coherent scattering experiments really see coherent effects over arbitrarily large distances? I would expect that the answer would be yes except the amplitude would fall to be undetectable, mainly based on the double slit experiments which show macroscopic coherence of individual particles.
2d	comment	Is energy simple or composite? In the first feynaman diagram, the photon, the quarks are off mass shell, virtual. the heisenberg uncertainty and any other manifestation of particles follows similar feynman diagrams. Some particle, off mass shell or on, carries the energy. The energy is not a particle.
2d	comment	Is energy simple or composite? Not exactly. A particle carries energy, as the protons in the LHC. Interacting with other particles part of that energy is converted to new particles . There is no point in spacetime that is just energy. Have a look at Feynman diagrams, which are the mathematical description of what happens en.wikipedia.org/wiki/Feynman_diagrams : in the figure an electron meets a positron and their combined energy via an off mass shell photon makes a quark antiquark pair and a gluon. There is not "pure energy"
2d	comment	Is energy simple or composite? well I would add that the particles in the table in the link I gave are distinguished because each has many different quantum numbers plus a characteristic rest mass, which is also a similar attribute.
2d	comment	Is energy simple or composite? What David says. If you study the table of elementary particles in the link you will see that the photon is a particle.
Jun 16	comment	Ball jumping from water Ball was deflated and I could not find the inflating thingamajig . My view is that when you put the ball down with enthusiasm you give it more potential energy ( including the elasticity of the ball) and it bounces out high. When you dive, rather a friend dives, to three meters the ball is released at rest except the potential from the buoyancy. My analysis is that going up the three meters the ball gets a limiting velocity ( viscosity) and this is what is seen which obviously in your case is less than the 50cm one. I would try to have the ball at rest at 50cm and then release it to measure.
Jun 15	comment	Fusion vs. Fission This wiki article may help you understand, en.wikipedia.org/wiki/Nuclear_binding_energy, particularly the binding energy per nucleon plot.
Jun 15	comment	Ball jumping from water I am going swimming in an hour or so and will try your experiment.
Jun 15	comment	What made up light photons? In ancient times were hand waving and philosophy physics. Physics since Newton advances with mathematical models that fit existing data and predict future behaviors. At the moment the photon is an elementary particle. There exist compositeness theories but at the moment are marginalized because they cannot really fit the data summarized in the standard model of physics which has been verified over and over.en.wikipedia.org/wiki/Standard_Model . This is a big load to carry for any competing theory of compositeness and nobody has succeeded up to now.
Jun 15	comment	What made up light photons? A photon is one of the elementary particles we have found out in nature. en.wikipedia.org/wiki/Elementary_particle Nothing makes up a photon, that is what elementary means. Ensembles (i.e. very large numbers) of photons make up light as we see it. Photons have energy= h*nu (nu is the frequency) . Energy is a much larger concept than photons.
Jun 15	comment	Is light particle of wave? continued: How can the keyboard be a keyboard and also be composed of atoms is the corresponding question. Now if you ask why photons and electrons are also waves and particles that is another question. you can read an answer to this last in physics.stackexchange.com/questions/46237/…
Jun 15	comment	Is light particle of wave? The light we see is composed of photons, elementary particles of light, zillions of them. In a similar way this keyboard I am typing on is composed of atoms, which are composed of nucleons and electrons which nucleons are composed of quarks. A solid we can weight and feel is much more nested than the light we see .
Jun 15	comment	Does shadow have mass? This question mixes apples and oranges. subatomic particles are not the shadow of anything.
Jun 15	comment	Does shadow have mass? It does show that to first order a shadow does not affect mass by its size, as it should by any definition of mass.
Jun 15	comment	Born rule for photons: it works, but it shouldn't? Lubos has an interesting article in his blog of how photons build up the classical field motls.blogspot.com/2011/11/…
Jun 14	comment	Surviving under water in air bubble +1 for calculating. So my estimate of about 883 meters of surface air trapped dominates the reason he was saved. a diameter of 400 meters is no go on a tugboat.
Jun 14	comment	Surviving under water in air bubble @Ariel the limit I estimate can be considered a lower limit, at least 6000 cubic feet of surface air. If Co2 can be reabsorbed so much the better. But the numbers are not so discrepant to require thinking of complicated exchanges.