Science and Exploration

[dreadgeek]

It was pointed out to me that 2.5 orders of magnitude might be a little difficult for people to grasp intuitively so to give you a sense of scale I'll use this. I live in Portland, OR but I work in Hillsboro, OR. That's about 20 miles one-way, door-to-door from home to office. One order of magnitude would be ten times that far or 200 miles. That would put me in Grants Pass, OR or just north of Seattle, WA. Two orders of magnitude would be 2000 miles away so that would be in the Detroit, MI region. Two and half orders of magnitude would be 3000 miles or somewhere in northern Maine.

So to understand the scale of distance between the Moon and Earth compared to Mars and Earth, do this; take a city that is around 25 miles from you. Find a city that is ten times that distance (one order of magnitude) away. Now, find a city that is 100 times further away (two orders of magnitude). Now find another city that is half-again as far away (two and half orders of magnitude) and THAT is the ratio of distance scaled down to terrestrial scales. . So, to scale, the Earth is as far away from Mars as Portland, OR is from northern Maine. The Earth is as far away from the Moon as Portland, OR is from Seattle WA.

Originally Posted by dreadgeek

As Phil Plaitt points out in this article, every year around this time people start spreading this Internet meme that Mars will look as large as the Moon in the night sky. It's a hoax. It will always be a hoax because Mars *never* gets close enough to Earth to look as large as the Moon. At its closest pass Mars gets within 35 million miles of Earth. At its farthest point (where it is now) it is about 210 million miles from Earth (it's currently on the far side of the Sun from us). Mars is a relatively small planet. It is half the size of Earth. The moon is about half the size of Mars. The moon is just next door (250,000 miles) compared with with the 35 million miles between Earth and Mars at their closest. So in order for this meme to be true, an object only twice the size of our moon would have to appear to be the same size even though Mars is two and a half orders of magnitude farther away from Earth! That's not optically *possible*. With the naked eye Mars can only ever look like a tiny dot in the sky. If it ever *were* in an orbit that would make it look the same size as the Moon that would be a very interesting day on Earth (interesting, here, in the "Oh God, Oh God, we're all gonna die" sense).

So if you see a meme on Facebook telling you that if you go outside sometime in the next week it'll appear as if the planet has two moons, know that someone is pulling your leg because they are.

Cheers
Aj

[Hollylane]

The Tamu massif is comparable in size to Olumpus Mons on Mars

Scientists say that they have discovered the single largest volcano in the world, a dead colossus deep beneath the Pacific waves.

A team writing in the journal Nature Geoscience says the 310,000 sq km (119,000 sq mi) Tamu Massif is comparable in size to Mars' vast Olympus Mons volcano - the largest in the Solar System.

The structure topples the previous largest on Earth, Mauna Loa in Hawaii.

The massif lies some 2km below the sea.

It is located on an underwater plateau known as the Shatsky Rise, about 1,600km east of Japan.

It was formed about 145 million years ago when massive lava flows erupted from the centre of the volcano to form a broad, shield-like feature.

The researchers doubted the submerged volcano's peak ever rose above sea level during its lifetime and say it is unlikely to erupt again.

"The bottom line is that we think that Tamu Massif was built in a short (geologically speaking) time of one to several million years and it has been extinct since," co-author William Sager, from the University of Houston, US, told the AFP news agency.

"One interesting angle is that there were lots of oceanic plateaus (that) erupted during the Cretaceous Period (145-65 million years ago) but we don't see them since. Scientists would like to know why."

Prof Sager began studying the structure two decades ago, but it had been unclear whether the massif was one single volcano or many - a kind that exists in dozens of locations around the planet.

While Olympus Mons on Mars has relatively shallow roots, the Tamu Massif extends some 30 km (18 miles) into the Earth's crust.

And other volcanic behemoths could be lurking among the dozen or so large oceanic plateaux around the world, he thought.

"We don't have the data to see inside them and know their structure, but it would not surprise me to find out that there are more like Tamu out there," said Dr Sager.

"Indeed, the biggest oceanic plateau is Ontong Java plateau, near the equator in the Pacific, east of the Solomons Islands. It is much bigger than Tamu -- it's the size of France."

The name Tamu comes from Texas A&M University, where Prof Sager previously taught before moving to the University of Houston.

[Hollylane]

A crater lake at the summit threatens to create dangerous mud flows in the event of an eruption

Scientists from the UK, US and North Korea have joined forces to monitor the volcano responsible for one of the largest eruptions in history.

The volcano straddles the border between North Korea and China, and has been largely dormant since erupting a little over a thousand years ago.

Despite being at the top of the list of big eruptions, Mount Paektu remains obscure and enigmatic.

Details of the collaborative effort have been outlined in Science journal.

The international group of geologists has begun working on the volcano following a spate of recent earthquake activity that could indicate it is waking from slumber.

Surprisingly, the volcano is relatively unknown in the West, not helped by the fact that it takes a confusing array of names. In China it is known variously as Tianchi or Changbaishan, but its Korean name is Baegdu-san or Mount Paektu, while the Japanese call it Hakuto-san.

Around two thirds of the volcano lies in North Korea, with the remainder is in Chinese territory, and an estimated 30,000 tourists visit its Chinese flank each day, around twice the number visiting Mount Fuji in Japan.

In 940 AD, the volcano exploded in a huge eruption, known as the "millennium eruption" that threw ash vast distances. Measurements of ash deposits from that eruption measured in Japan indicate that this was one of the two largest known volcanic eruptions on Earth since that period, matched only by the Tambora eruption in Indonesia, in 1815 AD.

Dr James Hammond from Imperial College London, and Prof Clive Oppenheimer from the University of Cambridge have begun a collaborative study with North Korean scientists, aiming to understand the structure of the subterranean magma chamber lying beneath the volcanic mountain.

Explaining the origins of the project, Dr Hammond told BBC News: "The whole region is quite worried about the volcano because it has shown signs of activity, so the North Koreans put a lot of effort into watching it, and basically said 'do you want to come to Korea, could you bring some equipment?'"

UK seismometers, deployed on the volcano's flanks, will reveal its structure and activity

The team has deployed a set of seismometers that can record earth tremors associated with the movement of magma beneath the volcano.

Organising a scientific collaboration in North Korea has not been without logistical and bureaucratic hurdles, but Dr Hammond continued: "What made it possible was having great people involved who were passionate about doing this, at all levels, from the scientists on the ground to those higher up where the decisions get made."

The study will help scientists understand why the volcano is there, which is something of a geological mystery, and why rock is melting at its heart, possibly stoking a future threat.

"This project is not about monitoring the volcano or predicting when the eruption will happen, but is about understanding what happened during the millennium eruption and also looking at what its state is now, using geophysical techniques. This will help us understand what is driving the volcano," Dr Hammond explained.

Prof James Gill, from University of California, Santa Cruz, has been working on the Chinese side of the volcano for some years, but is not involved in the new study. He told BBC News: "The volcano has erupted big time in the past, and were it to happen again, the Chinese, South Korean and Japanese economies could all be affected.

"There was a crisis in 2002-2005 when the seismicity picked up, the gas chemistry of the fumaroles changed, the volcano inflated, and it might have erupted. It may still be dangerous.

"The North Korean underground nuclear test site is only 70km or so away, so when the last test took place, the South Koreans were concerned that this might set off the volcano.

"One of the world's biggest volcanoes is sat in a backwater of the Cold War."

Prof Gill described some of the difficulties of carrying out field work at a militarised border, sampling rocks under armed escort. The new collaboration with the North Koreans is something of a landmark in current scientific co-operation with the isolated state.

This is not the only volcano that Prof Oppenheimer and Dr Hammond have worked on in difficult circumstances. They have previously studied volcanoes that straddle the border of Eritrea and Ethiopia. Like Mount Paektu, that investigation also ran into challenges due to the local political situation, but underlines the fact that natural hazards pay no attention to political differences.

[Smiling]

I am certainly not a scientist, but holy crap; I can see a lot of possibilities in this discovery! Absolutely incredible....


http://www.eurekalert.org/pub_releas...-sli092513.php

Seeing light in a new light

Scientists create never-before-seen form of matter

Harvard and MIT scientists are challenging the conventional wisdom about light, and they didn't need to go to a galaxy far, far away to do it.

Working with colleagues at the Harvard-MIT Center for Ultracold Atoms, a group led by Harvard Professor of Physics Mikhail Lukin and MIT Professor of Physics Vladan Vuletic have managed to coax photons into binding together to form molecules – a state of matter that, until recently, had been purely theoretical. The work is described in a September 25 paper in Nature.

The discovery, Lukin said, runs contrary to decades of accepted wisdom about the nature of light. Photons have long been described as massless particles which don't interact with each other – shine two laser beams at each other, he said, and they simply pass through one another.

"Photonic molecules," however, behave less like traditional lasers and more like something you might find in science fiction – the light saber.

"Most of the properties of light we know about originate from the fact that photons are massless, and that they do not interact with each other," Lukin said. "What we have done is create a special type of medium in which photons interact with each other so strongly that they begin to act as though they have mass, and they bind together to form molecules. This type of photonic bound state has been discussed theoretically for quite a while, but until now it hadn't been observed.

"It's not an in-apt analogy to compare this to light sabers," Lukin added. "When these photons interact with each other, they're pushing against and deflect each other. The physics of what's happening in these molecules is similar to what we see in the movies."

To get the normally-massless photons to bind to each other, Lukin and colleagues, including Harvard post-doctoral fellow Ofer Fisterberg, former Harvard doctoral student Alexey Gorshkov and MIT graduate students Thibault Peyronel and Qiu Liang couldn't rely on something like the Force – they instead turned to a set of more extreme conditions.

Researchers began by pumped rubidium atoms into a vacuum chamber, then used lasers to cool the cloud of atoms to just a few degrees above absolute zero. Using extremely weak laser pulses, they then fired single photons into the cloud of atoms.

As the photons enter the cloud of cold atoms, Lukin said, its energy excites atoms along its path, causing the photon to slow dramatically. As the photon moves through the cloud, that energy is handed off from atom to atom, and eventually exits the cloud with the photon.

"When the photon exits the medium, its identity is preserved," Lukin said. "It's the same effect we see with refraction of light in a water glass. The light enters the water, it hands off part of its energy to the medium, and inside it exists as light and matter coupled together, but when it exits, it's still light. The process that takes place is the same it's just a bit more extreme – the light is slowed considerably, and a lot more energy is given away than during refraction."

When Lukin and colleagues fired two photons into the cloud, they were surprised to see them exit together, as a single molecule.

The reason they form the never-before-seen molecules?

An effect called a Rydberg blockade, Lukin said, which states that when an atom is excited, nearby atoms cannot be excited to the same degree. In practice, the effect means that as two photons enter the atomic cloud, the first excites an atom, but must move forward before the second photon can excite nearby atoms.

The result, he said, is that the two photons push and pull each other through the cloud as their energy is handed off from one atom to the next.

"It's a photonic interaction that's mediated by the atomic interaction," Lukin said. "That makes these two photons behave like a molecule, and when they exit the medium they're much more likely to do so together than as single photons."

While the effect is unusual, it does have some practical applications as well.

"We do this for fun, and because we're pushing the frontiers of science," Lukin said. "But it feeds into the bigger picture of what we're doing because photons remain the best possible means to carry quantum information. The handicap, though, has been that photons don't interact with each other."

To build a quantum computer, he explained, researchers need to build a system that can preserve quantum information, and process it using quantum logic operations. The challenge, however, is that quantum logic requires interactions between individual quanta so that quantum systems can be switched to perform information processing.

"What we demonstrate with this process allows us to do that," Lukin said. "Before we make a useful, practical quantum switch or photonic logic gate we have to improve the performance, so it's still at the proof-of-concept level, but this is an important step. The physical principles we've established here are important."

The system could even be useful in classical computing, Lukin said, considering the power-dissipation challenges chip-makers now face. A number of companies – including IBM – have worked to develop systems that rely on optical routers that convert light signals into electrical signals, but those systems face their own hurdles.

Lukin also suggested that the system might one day even be used to create complex three-dimensional structures – such as crystals – wholly out of light.

"What it will be useful for we don't know yet, but it's a new state of matter, so we are hopeful that new applications may emerge as we continue to investigate these photonic molecules' properties," he said.