"A 90-pound "folded-box-structure" backbone of aluminum honeycomb composite panels. Interior panels are glued to this chassis to create a tub within a tub. The monocoque is then surrounded front and back with subframes of chromoly. [...] Scissor doors, deep side-air intakes, fender louvres, and a low fighter-plane-style greenhouse complete the racetrack-ready purrfection."
Carbon-fiber body, low-weight V8 engine, six-speed manual transmission --- and no fuzzy dice unless you put them there yourself.
The fundamental nature of the photon is believed to be understood
theoretically; the prevailing Standard Model predicts that the photon is a gauge boson of spin 1, without mass and without charge, that results from a local U(1) gauge symmetry and mediates the electromagnetic interaction.
However, physicists continue to check for discrepancies between experiment and the Standard Model predictions, in the hope of finding clues to physics beyond the Standard Model.
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Photon structure
Main article: Quantum Chromodynamics
According to Quantum Chromodynamics, a real photon can interact both as a point-like particle, or as a collection of quarks and gluons, i.e., like a hadron. The structure of the photon is determined not by the traditional valence quark distributions as in a proton, but by fluctuations of the point-like photon into a collection of partons.
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Contributions to the mass of a system
See also: Mass in special relativity and Gravitation
The energy of a system that emits a photon is decreased by the energy E of the photon as measured in the rest frame of the emitting system, which may result in a reduction in mass in the amount E / c2. Similarly, the mass of a system that absorbs a photon is increased by a corresponding amount.
This concept is applied in a key prediction of QED, the theory of quantum electrodynamics begun by Dirac (described above). QED is able to predict the magnetic dipole moment of leptons to extremely high accuracy; experimental measurements of these magnetic dipole moments have agreed with these predictions perfectly. The predictions, however, require counting the contributions of virtual photons to the mass of the lepton. Another example of such contributions verified experimentally is the QED prediction of the Lamb shift observed in the hyperfine structure of bound lepton pairs, such as muonium and positronium.
Since photons contribute to the stress-energy tensor, they exert a gravitational attraction on other objects, according to the theory of general relativity. Conversely, photons are themselves affected by gravity; their normally straight trajectories may be bent by warped spacetime, as in gravitational lensing, and their frequencies may be lowered by moving to a higher gravitational potential, as in the Pound-Rebka experiment.
Wikipedia
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They are still spending time and money on this question, right? That means the issue is not settled; there is still debate going on.
