The 2016 Nobel Prize In Physics: It’s Complicated

This year's Nobel Prize in physics highlights the complications of awarding breakthrough achievements. Credit: nobelprize.org

The Nobel Prize in physics is a coveted award. Every year, the prize is bestowed upon the individual who is deemed to have made the greatest contribution to the field of physics during the preceding year. And this year, the groundbreaking discovery of gravitational waves is anticipated to be the main focus.

This discovery, which was announced on February 11th, 2016, was made possible thanks to the development of the Laser Interferometer Gravitational-Wave Observatory (LIGO). As such, it is expected that the three scientists that are most responsible for the invention of the technology will receive the Nobel Prize for their work. However, there are those in the scientific community who feel that another scientist – Barry Barish – should also be recognized.

But first, some background is needed to help put all this into perspective. For starers, gravitational waves are ripples in the curvature of spacetime that are generated by certain gravitational interactions and whic propagate at the speed of light. The existence of such waves has been postulated since the late 19th century.

However, it was not until the late 20th century, thanks in large part to Einstein and his theory of General Relativity, that gravitational-wave research began to emerge as a branch of astronomy. Since the 1960s, various gravitational-wave detectors have been built, which includes the LIGO observatory.

Founded as a Caltech/MIT project, LIGO was officially approved by the National Science Board (NSF) in 1984. A decade later, construction began on facility’s two locations – in Hanford, Washington and Livingston, Louisiana. By 2002, it began to obtain data, and work began on improving its original detectors in 2008 (known as the Advanced LIGO Project).

The credit for the creation of LIGO goes to three scientists, which includes Rainer Weiss, a professor of physics emeritus at the Massachusetts Institute of Technology (MIT); Ronald Drever, an experimental physics who was professor emeritus at the California Institute of Technology and a professor at Glasgow University; and Kip Thorne, the Feynman Professor of Theoretical Physics at Caltech.

In 1967 and 68, Weiss and Thorne initiated efforts to construct prototype detectors, and produced theoretical work to prove that gravitational waves could be successfully analyzed. By the 1970s, using different methods, Weiss and Denver both succeeded in building detectors. In the coming years, all three men remained pivotal and influential, helping to make gravitational astronomy a legitimate field of research.

However, it has been argued that without Barish – a particle physicist at Caltech – the discovery would never have been made. Having become the Principal Investigator of LIGO in 1994, he inherited the project at a very crucial time. It had begun funding a decade prior, but coordinating the work of Wiess, Thorne and Drever (from MIT, Caltech and the University of Glasgow, respectively) proved difficult.

As such, it was decided that a single director was needed. Between 1987 and 1994, Rochus Vogt – a professor emeritus of Physics at Caltech – was appointed by the NSF to fill this role. While Vogt brought the initial team together and helped to get the construction of the project approved, he proved difficult when it came to dealing with bureaucracy and documenting his researchers progress.

As such, between 1989 through 1994, LIGO failed to progress technically and organizationally, and had trouble acquiring funding as well. By 1994, Caltech eased Vogt out of his position and appointed Barish to the position of director. Barish got to work quickly, making significant changes to the way LIGO was administered, expanding the research team, and developing a detailed work plan for the NSF.

Barish was also responsible for expanding LIGO beyond its Caltech and MIT constraints. This he did through the creation of the independent LIGO Scientific Collaboration (LSC), which gave access to outside researchers and institutions. This was instrumental in creating crucial partnerships, which included the UK Science and Technology Facilities Council, the Max Planck Society of Germany, and the Australian Research Council.

By 1999, construction had wrapped up on the LIGO observatories, and by 2002, they began taking their first bits of data. By 2004, the funding and groundwork was laid for the next phase of LIGO development, which involved a multi-year shut-down while the detectors were replaced with improved “Advanced LIGO” versions.

All of this was made possible by Barish, who retired in 2005 to head up other projects. Thanks to his sweeping reforms, LIGO got to work after an abortive start, began to produce data, procured funding, crucial partnerships, and now has more than 1000 collaborators worldwide, thanks to LSC program he established.

Little wonder then why some scientists think the Nobel Prize should be split four-ways, awarding the three scientists who conceived of LIGO and the one scientist who made it happen. And as Barish himself was quoted as saying by Science:

“I think there’s a bit of truth that LIGO wouldn’t be here if I didn’t do it, so I don’t think I’m undeserving. If they wait a year and give it to these three guys, at least I’ll feel that they thought about it,” he says. “If they decide [to give it to them] this October, I’ll have more bad feelings because they won’t have done their homework.”

However, there is good reason to believe that the award will ultimately be split three ways, leaving Barish out. For instance, Weiss, Drever, and Thorne have been honored three times already this year for their work on LIGO. This has included the Special Breakthrough Prize in Fundamental Physics, the Gruber Cosmology Prize, and Kavli Prize in Astrophysics.

What’s more, in the past, the Nobel Prize in physics has tended to be awarded to those responsible for the intellectual contributions leading to a major breakthrough, rather than to those who did the leg work. Out of the last six Prizes issued (between 2010 and 2015), five have been awarded for the development of experimental methods, observational studies, and theoretical discoveries.

Only one award was given for a technical development. This was the case in 2014 where the award was given jointly to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for “the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources”.

Basically, the Nobel Prize is a complicated matter. Every year, it is awarded to those who made a considerable contribution to science, or were responsible for a major breakthrough. But contributions and breakthroughs are perhaps a bit relative. Whom we choose to honor, and for what, can also be seen as an indication of what is valued most in the scientific community.

In the end, this year’s award may serve to highlight how significant contributions do not just entail the development of new ideas and methods, but also in bringing them to fruition.

Further Reading: Science, LIGO, Nobelprize.org

The post The 2016 Nobel Prize In Physics: It’s Complicated appeared first on Universe Today.

Kuiper Belt Objects Point The Way To Planet 9

Artist's impression of Planet Nine as an ice giant eclipsing the central Milky Way. Credit: ESO/Tomruen/nagualdesign

On January 20th, 2016, researchers Konstantin Batygin and Michael E. Brown of Caltech announced that they had found evidence that hinted at the existence of a massive planet at the edge of the Solar System. Based on mathematical modeling and computer simulations, they predicted that this planet would be a super-Earth, two to four times Earth’s size and 10 times as massive. They also estimated that, given its distance and highly elliptical orbit, it would take 10,000 – 20,000 years to orbit the Sun.

Since that time, many researchers have responded with their own studies about the possible existence of this mysterious “Planet 9”. One of the latest comes from the University of Arizona, where a research team from the Lunar and Planetary Laboratory have indicated that the extreme eccentricity of distant Kuiper Belt Objects (KBOs) might indicate that they crossed paths with a massive planet in the past.

For some time now, it has been understood that there are a few known KBOs who’s dynamics are different than those of other belt objects. Whereas most are significantly controlled by the gravity of the gas giants planets in their current orbits (particularly Neptune), certain members of the scattered disk population of the Kuiper Belt have unusually closely-spaced orbits.

When Batygin and Brown first announced their findings back in January, they indicated that these objects instead appeared to be highly clustered with respect to their perihelion positions and orbital planes. What’s more, their calculation showed that the odds of this being a chance occurrence were extremely low (they calculated a probability of 0.007%).

Instead, they theorized that it was a distant eccentric planet that was responsible for maintaining the orbits of these KBOs. In order to do this, the planet in question would have to be over ten times as massive as Earth, and have an orbit that lay roughly on the same plane (but with a perihelion oriented 180° away from those of the KBOs).

Such a planet not only offered an explanation for the presence of high-perihelion Sedna-like objects – i.e. planetoids that have extremely eccentric orbits around the Sun. It would also help to explain where distant and highly inclined objects in the outer Solar System come from, since their origins have been unclear up until this point.

In a paper titled “Coralling a distant planet with extreme resonant Kuiper belt objects“, the University of Arizona research team – led by Renu Malhotra, the Louise Foucar Marshall Science Research Professor – looked at things from another angle. If in fact Planet 9 were crossing paths with certain high-eccentricity KBOs, they reasoned, it was a good bet that its orbit was in resonance with these objects.

To break it down, small bodies are ejected  from the Solar System all the time due to encounters with larger objects that perturb their orbits. In order to avoid being ejected, smaller bodies need to be protected by orbital resonances. While the smaller and larger objects may pass within each others’ orbital path, they are never close enough that they would able to exert a significant influence on each other.

This is how Pluto has remained a part of the Solar System, despite having an eccentric orbit that periodically cross Neptune’s path. Though Neptune and Pluto cross each others orbit, they are never close enough to each other that Neptune’s influence would force Pluto out of our Solar System. Using this same reasoning, they hypothesized that the KBOs examined by Batygin and Brown might be in an orbital resonance with the Planet 9.

As Dr.  Malhotra told Universe Today via email:

“The extreme Kuiper belt objects we investigate in our paper are distinct from the others because they all have very distant, very elliptical orbits, but their closest approach to the Sun isn’t really close enough for them to meaningfully interact with Neptune. So we have these six observed objects whose orbits are currently fairly unaffected by the known planets in our Solar System. But if there’s another, as yet unobserved planet located a few hundred AU from the Sun, these six objects would be affected by that planet.”

After examining the orbital periods of these six KBOs – Sedna, 2010 GB174, 2004 VN112, 2012 VP113, and 2013 GP136 – they concluded that a hypothetical planet with an orbital period of about 17,117 years (or a semimajor axis of about 665 AU), would have the necessary period ratios with these four objects. This would fall within the parameters estimated by Batygin and Brown for the planet’s orbital period (10,000 – 20,000 years).

Their analysis also offered suggestions as to what kind of resonance the planet has with the KBOs in question. Whereas Sedna’s orbital period would have a 3:2 resonance with the planet, 2010 GB174 would be in a 5:2 resonance, 2994 VN112 in a 3:1, 2004 VP113 in 4:1, and 2013 GP136 in 9:1. These sort of resonances are simply not likely without the presence of a larger planet.

“For a resonance to be dynamically meaningful in the outer Solar System, you need one of the objects to have enough mass to have a reasonably strong gravitational effect on the other,” said Malhotra. “The extreme Kuiper belt objects aren’t really massive enough to be in resonances with each other, but the fact that their orbital periods fall along simple ratios might mean that they each are in resonance with a massive, unseen object.”

But what is perhaps most exciting is that their findings could help to narrow the range of Planet 9’s possible location. Since each orbital resonance provides a geometric relationship between the bodies involved, the resonant configurations of these KBOs can help point astronomers to the right spot in our Solar System to find it.

But of course, Malhotra freely admits that several unknowns remain, and further observation and study is necessary before Planet 9 can be confirmed:

“There are a lot of uncertainties here. The orbits of these extreme Kuiper belt objects are not very well known because they move very slowly on the sky and we’ve only observed very small portions of their orbital motion. So their orbital periods might differ from the current estimates, which could make some of them not resonant with the hypothetical planet. It could also just be chance that the orbital periods of the objects are related; we haven’t observed very many of these types of objects, so we have a limited set of data to work with.”

Ultimately, astronomers and the rest of us will simply have to wait on further observations and calculations. But in the meantime, I think we can all agree that the possibility of a 9th Planet is certainly an intriguing one! For those who grew up thinking that the Solar System had nine planets, these past few years (where Pluto was demoted and that number fell to eight) have been hard to swallow.

But with the possible confirmation of this Super-Earth at the outer edge of the Solar System, that number could be pushed back up to nine soon enough!

Further Reading: arXiv.org

The post Kuiper Belt Objects Point The Way To Planet 9 appeared first on Universe Today.

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