Cardiology

Mobile device to provide instant diagnosis of heart diseases

Cardiovascular diseases (CVDs) continue to be a leading cause of death. According to the World Health Organization, more people die annually from CVDs than from any other cause. Since their diagnosis might require specialised ...

Neuroscience

Scientists grow human 'mini brains'

Birmingham scientists who are growing human brain cells in the laboratory say their work could one day help combat the damage caused by Alzheimer's and other brain traumas.

Cardiology

New handheld scanner to give instant heart disease diagnosis

With worldwide cardiovascular deaths at an all-time high, European scientists have developed a new handheld scanner that can read your heart's vital signs like a supermarket barcode reader can scan items at the checkout, ...

Medical research

Research teams unite for research on Lou Gehrig's Disease

Lisa Miller and Paul Gelfand, biophysical chemists at the U.S. Department of Energy's Brookhaven National Laboratory, recently visited the Advanced Photon Source at Argonne National Laboratory to supplement their research ...

HIV & AIDS

How HIV infects cells

In a long-awaited finding, an international team of scientists using high-brightness x-rays from the U.S. Department of Energy Office of Science's Advanced Photon Source at Argonne National Laboratory has determined the high-resolution ...

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Photon

In physics, a photon is an elementary particle, the quantum of the electromagnetic field and the basic "unit" of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force. The effects of this force are easily observable at both the microscopic and macroscopic level, because the photon has no rest mass; this allows for interactions at long distances. Like all elementary particles, photons are governed by quantum mechanics and will exhibit wave-particle duality – they exhibit properties of both waves and particles. For example, a single photon may be refracted by a lens or exhibit wave interference, but also act as a particle giving a definite result when its location is measured.

The modern concept of the photon was developed gradually by Albert Einstein to explain experimental observations that did not fit the classical wave model of light. In particular, the photon model accounted for the frequency dependence of light's energy, and explained the ability of matter and radiation to be in thermal equilibrium. It also accounted for anomalous observations, including the properties of black body radiation, that other physicists, most notably Max Planck, had sought to explain using semiclassical models, in which light is still described by Maxwell's equations, but the material objects that emit and absorb light are quantized. Although these semiclassical models contributed to the development of quantum mechanics, further experiments proved Einstein's hypothesis that light itself is quantized; the quanta of light are photons.

In the modern Standard Model of particle physics, photons are described as a necessary consequence of physical laws having a certain symmetry at every point in spacetime. The intrinsic properties of photons, such as charge, mass and spin, are determined by the properties of this gauge symmetry.

The photon concept has led to momentous advances in experimental and theoretical physics, such as lasers, Bose–Einstein condensation, quantum field theory, and the probabilistic interpretation of quantum mechanics. It has been applied to photochemistry, high-resolution microscopy, and measurements of molecular distances. Recently, photons have been studied as elements of quantum computers and for sophisticated applications in optical communication such as quantum cryptography.

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