This new atomic clock is so exact, it could be used to detect dark matter
Scientists have invented a new clock that keeps time more precisely than any that have come before.
Dec 1, 2018
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271
Engineering
Scientists have invented a new clock that keeps time more precisely than any that have come before.
Dec 1, 2018
1
271
Engineering
Researchers commonly study brain function by monitoring two types of electromagnetism—electric fields and light. However, most methods for measuring these phenomena in the brain are very invasive.
Oct 22, 2018
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133
Hardware
MIT researchers have developed the first molecular clock on a chip, which uses the constant, measurable rotation of molecules—when exposed to a certain frequency of electromagnetic radiation—to keep time. The chip could ...
Jul 16, 2018
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289
Energy & Green Tech
Engineers at the University of Wisconsin-Madison are shining a light on promising new strategies for storing solar power. The efforts could help overcome one major limitation of energy generation from solar sources—namely, ...
Apr 27, 2018
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17
Engineering
Researchers at Case Western Reserve University are developing atomically thin "drumheads" able to receive and transmit signals across a radio frequency range far greater than what we can hear with the human ear.
Mar 30, 2018
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796
Engineering
Cement materials, including cement paste, mortar, and concrete, are the most widely manufactured materials in the world. Their carbon footprint is similarly hefty: The processes involved in making cement contribute almost ...
Oct 2, 2017
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40
Engineering
Researchers at Caltech have developed a prototype miniature medical device that could ultimately be used in "smart pills" to diagnose and treat diseases. A key to the new technology—and what makes it unique among other ...
Sep 12, 2017
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20
Energy & Green Tech
As the most abundant gas in Earth's atmosphere, nitrogen has been an attractive option as a source of renewable energy. But nitrogen gas—which consists of two nitrogen atoms held together by a strong, triple covalent bond—doesn't ...
Apr 13, 2017
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2565
Energy & Green Tech
Scientists from the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have discovered a possible secret to dramatically boosting the efficiency of perovskite solar cells hidden in the nanoscale peaks ...
Jul 4, 2016
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32
The atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen-1, which is the only stable nuclide with no neutron). The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain bound to each other, forming a molecule. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it has a positive or negative charge and is an ion. An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons determines the chemical element, and the number of neutrons determine the isotope of the element.
The name atom comes from the Greek ἄτομος/átomos, α-τεμνω, which means uncuttable, something that cannot be divided further. The concept of an atom as an indivisible component of matter was first proposed by early Indian and Greek philosophers. In the 17th and 18th centuries, chemists provided a physical basis for this idea by showing that certain substances could not be further broken down by chemical methods. During the late 19th and early 20th centuries, physicists discovered subatomic components and structure inside the atom, thereby demonstrating that the 'atom' was divisible. The principles of quantum mechanics were used to successfully model the atom.
Relative to everyday experience, atoms are minuscule objects with proportionately tiny masses. Atoms can only be observed individually using special instruments such as the scanning tunneling microscope. Over 99.9% of an atom's mass is concentrated in the nucleus, with protons and neutrons having roughly equal mass. Each element has at least one isotope with unstable nuclei that can undergo radioactive decay. This can result in a transmutation that changes the number of protons or neutrons in a nucleus. Electrons that are bound to atoms possess a set of stable energy levels, or orbitals, and can undergo transitions between them by absorbing or emitting photons that match the energy differences between the levels. The electrons determine the chemical properties of an element, and strongly influence an atom's magnetic properties.
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