Category: General AS/A2

What are Maxwell’s Equations?

What are Maxwell’s Equations?

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The Higgs boson particle – digested

The Higgs boson particle – digested

The Higgs boson particle – digested
The secret of life and the universe, explained by our science editor

An experimental result in the search for the Higgs boson particle, released by Cern.

In the aftermath of the big bang that flung the universe into existence 13.82bn years ago, the forces of nature were one. But as the universe expanded and cooled, they separated out into the four seen today. The electromagnetic force, which is carried by photons, allows you to see, and stops you falling through your chair.

The strong force holds atomic nuclei together. The weak force goes to work in the sun and helps to make it shine. Then there is gravity, which is not really a force at all, but that is for another time.

One trillionth of a second after the big bang, an invisible field that spread throughout space switched on. This Higgs field wrenched two intertwined forces apart – the weak force and the electromagnetic force. How? By making the particles that carry the weak force heavy, while leaving the photon weightless.

The weak force travels less than the width of an atom, but the electromagnetic force ranges over an infinite distance.

The Higgs field gives mass to other particles too, such as quarks and electrons, the building blocks of atoms. The Higgs boson comes with the field, a subatomic smoking gun that proves the field is there.

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New Scientist: Drone-wrecking laser gun to sail on US warship

New Scientist: Drone-wrecking laser gun to sail on US warship.

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‘Viking sunstone’ found in shipwreck

‘Viking sunstone’ found in shipwreck

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Diamond to shine light on infections

Diamond to shine light on infections

The UK’s national synchrotron facility – the Diamond Light Source near Oxford – is to become a world centre for studying the structure of viruses and bacteria that cause serious disease.

Diamond uses intense X-rays to reveal the molecular and atomic make-up of objects and materials.

It will now use this capability to image Containment Level 3 pathogens.

These are responsible for illnesses such as Aids, hepatitis and some types of flu.

Level 3 is one step down from the most dangerous types of infectious agent, such as Ebola, which can only be handled in the most secure government facilities.

“Viruses, as you know, are sort of tiny nanomachines and you can’t see them in a normal microscope.

“But with the crystallography and X-ray techniques we use, we are able to get about 10,000 times the resolution of the normal light microscope,” explained Dave Stuart, the life sciences director at Diamond and a professor of structural biology at Oxford University.

“This takes us from the regime of not being able to see them to being able to see individual atoms.

“And if we can look at ‘live’ viruses and get an atomic-level description of them, it opens up the possibility of using modern drug-design techniques to produce new pharmaceuticals.”

Prof Stuart was speaking in Boston at the annual meeting for the American Association for the Advancement of Science (AAAS).

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Has Dark Matter Finally Been Found? Big News Coming Soon

Has Dark Matter Finally Been Found? Big News Coming Soon.

If we can work this out then we can start to think about the end of the universe and also what is going to happen in the meantime  🙁

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Bose-Einstein condensate (BEC)

This is a fantastic article I wanted to share…

Bose-Einstein condensate (BEC), a state of matter in which separate atoms or subatomic particles, cooled to near absolute zero (0 K, − 273.15 °C, or − 459.67 °F; K = kelvin), coalesce into a single quantum mechanical entity—that is, one that can be described by a wave function—on a near-macroscopic scale. This form of matter was predicted in 1924 by Albert Einstein on the basis of the quantum formulations of the Indian physicist Satyendra Nath Bose.

Although it had been predicted for decades, the first atomic BEC was made only in 1995, when Eric Cornell and Carl Wieman of JILA, a research institution jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder, cooled a gas of rubidium atoms to 1.7 × 10−7 K above absolute zero. Along with Wolfgang Ketterle of the Massachusetts Institute of Technology (MIT), who created a BEC with sodium atoms, these researchers received the 2001 Nobel Prize for Physics. Research on BECs has expanded the understanding of quantum physics and has led to the discovery of new physical effects.

BEC theory traces back to 1924, when Bose considered how groups of photons behave. Photons belong to one of the two great classes of elementary or submicroscopic particles defined by whether their quantum spin is a nonnegative integer (0, 1, 2, …) or an odd half integer (1/2, 3/2, …). The former type, called bosons, includes photons, whose spin is 1. The latter type, called fermions, includes electrons, whose spin is 1/2.

As Bose noted, the two classes behave differently (see Bose-Einstein and Fermi-Dirac statistics). According to the Pauli exclusion principle, fermions tend to avoid each other, for which reason each electron in a group occupies a separate quantum state (indicated by different quantum numbers, such as the electron’s energy). In contrast, an unlimited number of bosons can have the same energy state and share a single quantum state.

Einstein soon extended Bose’s work to show that at extremely low temperatures “bosonic atoms” with even spins would coalesce into a shared quantum state at the lowest available energy. The requisite methods to produce temperatures low enough to test Einstein’s prediction did not become attainable, however, until the 1990s. One of the breakthroughs depended on the novel technique of laser cooling and trapping, in which the radiation pressure of a laser beam cools and localizes atoms by slowing them down. (For this work, French physicist Claude Cohen-Tannoudji and American physicists Steven Chu and William D. Phillips shared the 1997 Nobel Prize for Physics.) The second breakthrough depended on improvements in magnetic confinement in order to hold the atoms in place without a material container. Using these techniques, Cornell and Wieman succeeded in merging about 2,000 individual atoms into a “superatom,” a condensate large enough to observe with a microscope, that displayed distinct quantum properties. As Wieman described the achievement, “We brought it to an almost human scale. We can poke it and prod it and look at this stuff in a way no one has been able to before.”

BECs are related to two remarkable low-temperature phenomena: superfluidity, in which each of the helium isotopes 3He and 4He forms a liquid that flows with zero friction; and superconductivity, in which electrons move through a material with zero electrical resistance. 4He atoms are bosons, and although 3He atoms and electrons are fermions, they can also undergo Bose condensation if they pair up with opposite spins to form bosonlike states with zero net spin. In 2003 Deborah Jin and her colleagues at JILA used paired fermions to create the first atomic fermionic condensate.

BEC research has yielded new atomic and optical physics, such as the atom laser Ketterle demonstrated in 1996. A conventional light laser emits a beam of coherent photons; they are all exactly in phase and can be focused to an extremely small, bright spot. Similarly, an atom laser produces a coherent beam of atoms that can be focused at high intensity. Potential applications include more-accurate atomic clocks and enhanced techniques to make electronic chips, or integrated circuits.

The most intriguing property of BECs is that they can slow down light. In 1998 Lene Hau of Harvard University and her colleagues slowed light traveling through a BEC from its speed in vacuum of 3 × 108 metres per second to a mere 17 metres per second, or about 38 miles per hour. Since then, Hau and others have completely halted and stored a light pulse within a BEC, later releasing the light unchanged or sending it to a second BEC. These manipulations hold promise for new types of light-based telecommunications, optical storage of data, and quantum computing, though the low-temperature requirements of BECs offer practical difficulties.

Sidney Perkowitz

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Dark matter tracks could give earliest view of Universe

Researchers have come up with a way to glimpse the infant Universe by decoding the earliest ripples in its light.

They say this can be achieved by capturing the specific radio wavelength of 21cm from the heavens.

The trick is to tell the difference between 21cm waves from our galaxy and those from distant, ancient sources.

The fact that “dark matter” moved faster than normal matter in the early Universe should help amplify the distant signal, they report in Nature.

That could yield a look at the Universe when it was just 1% of its current age.

The scientists first revealed their 3-D computer simulations on Monday at the Gamma Ray Bursts in the Era of Rapid Follow-up conference, hosted by Liverpool John Moores University.

The current record-holder for the oldest object ever spotted is a galaxy named UDFy-38135539, seen in an optical image captured by the Hubble telescope. Its light escaped more than 13 billion years ago, when the Universe was already a youth of less than 700 million years.

Continue reading the main story

What is redshift?

Diagram of Doppler shift

  • The term “redshift” arises from the fact that light from more distant objects shows up on Earth more red than when it left its source
  • The colour shift comes about because of the Doppler effect, which acts to “stretch” or “compress” waves from moving objects
  • It is at work in the sound of a moving siren: an approaching siren sounds higher-pitched and a receding one sounds lower-pitched
  • In the case of light, approaching objects appear more blue and receding objects appear more red
  • The expansion of the Universe is accelerating, so in general, more distant objects are moving away from us (and each other, and everything else) more quickly than nearer ones
  • At cosmic distances, the shift can profoundly affect the colour – the factor by which the wavelength is “stretched” is called the redshift

Scientists measure these literally astronomical distances with the “redshift” of a given light source; it is a measure of how much the source’s light is stretched as it races away from us in the ever-expanding Universe.

UDFy-38135539 has a redshift of 8.55, but the new work shows promise for looking at stars and galaxies at a redshift of 20.

However, if it works, the view will be a statistical one – astronomers will not actually see individual stars and galaxies, but rather be able to estimate how many objects of what sizes were around in those early days.

But instead of seeing only the largest and brightest objects, as studies with telescopes such as Hubble typically do, it should work down to galactic haloes as small as a millionth the mass of the Milky Way’s halo.

“It’s very small galaxies from very far away; it’s completely hopeless to see them individually with any telescope in the next few decades,” said Rennan Barkana of Tel Aviv University, a co-author on the study.

“That’s why this is so interesting – it’s an indirect detection of the whole population of these galaxies, but it would be a very clear confirmation that these galaxies are there,” Prof Barkana told BBC News.

Dark materials

The 21cm wavelength arises from changes within the atoms of hydrogen, the Universe’s most abundant element, and one that can tell us much about the early Universe before heavier elements were formed.

A key insight lies in the different speed limits for dark matter and normal matter in the early Universe, first pointed out in a 2010 Physical Review D paper.

The early Universe was shaped in part by pressure waves – just like sound waves – created in the wake of the Big Bang. Like air molecules shifted around by sounds, these waves carried and distributed normal matter in regular patterns we can now observe.

Murchison Widefield Array Low-frequency radio telescopes such as the Murchison array could help spot the 21cm waves

But dark matter, because it does not interact with normal matter, was not swayed by the waves, responding only to gravity.

The distributions of dark and normal matter in the early Universe changes just where the matter – mostly hydrogen – ended up, in turn changing where the 21cm emission should come from, and how intense it should be.

Averaged over the sky, there should be a greater variation in this signal than we see locally, and the new paper makes the case that heating by X-ray radiation in those early days should make this statistical fluctuation even easier to spot.

Prof Barkana said that although there are no current radio telescope arrays designed to catch these 21cm waves, several are under construction that could be put onto the task.

“This whole subject of 21cm cosmology is about to open up; there are at least four different groups building radio telescope arrays focussing on about redshift 10,” he said.

“But until now no one has had the incentive to build an array optimised for this (redshift 20) wavelength range.”

By Jason Palmer Science and technology reporter, BBC News

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