Official "Science News" Thread

[Xyzzy]

http://www.latimes.com/science/scien...205-story.html

The latest findings in Earth science are brought to you by ancient astronomers who observed the heavens as much as 2,700 years ago.

[xilman]

Originally Posted by LaurV

The problem is that the methane molecule is not polarized, like the water molecule, for example.

That's completely true, however it is very far from being the complete story. Anyone interested in finding out why water and ammonia have extremely high melting points than, say, hydrogen chloride (which is also a very polar molecule and is much more typical could do worse than learn about hydrogen bonding. I well remember having to write an essay on the subject as an undergraduate chemist.

[kladner]

https://www.theguardian.com/science/...ther-evolution

A length of fluffy plumage discovered within a piece of amber has been identified as part of a dinosaur tail, offering new insights into the evolution of feathers.

Around 3.7cm long, with chestnut-coloured feathers on the top and pale feathers underneath, the tail was found complete with fossilised bones as well as traces of muscles, ligaments and mummified-looking skin.

While researchers say it is not possible to determine the species to which the tail belonged, they say the dinosaur lived around 99 million years ago and was most likely a juvenile, non-avian theropod – a group of dinosaurs that includes velociraptors and tyrannosaurs.

“If you were to hold [an adult] in your hand it would have been about the size of a sparrow,” said Ryan McKellar, co-author of the research from the Royal Saskatchewan Museum, Canada.

[Xyzzy]

http://arstechnica.com/science/2016/...to-the-jungle/

Inland Maya communities knew an awful lot about sharks without ever visiting the sea.

[kladner]

http://arstechnica.com/science/2016/...go-in-jericho/

To flesh out the features on the so-called Jericho Skull, archaeologists at the British Museum have worked for more than two years to reconstruct the face of a man whose skull had been reshaped by ritual throughout his long life. While he was an infant, his head had been bound tightly with cloth to change its shape. After he died at a ripe old age, his skull was then plastered, decorated, and put on display. This Jericho Skull gives us a glimpse of life in the Levant long before the rise of religions that describe a great battle at the city's walls.

Jericho, located today in Palestine, dates back more than 11,000 years and is one of the oldest continuously inhabited cities on Earth. It's very likely that this man lived behind the earliest versions of Jericho's infamous walls, built more than 9,000 years ago, but that doesn't mean he lived a hardscrabble existence threatened by war. Recent archaeological investigation of Jericho's Neolithic walls shows that they were not used for defense. Based on layers of silt that collected around them, researchers surmise that Jericho's first walls were built to prevent the city from being flooded during the rainy season.

[ewmayer]

LIGO black hole echoes hint at general-relativity breakdown | Nature

This sort of first-hint needs to taken with a huge grain of salt. Remember the ‘discovery’ in the late 1990s based on a survey of distant Type 1a “standard candle” supernovae that the universe is expanding at an accelerating rate? The one that earned the researchers a Nobel prize 5 years ago? Cf. the 10/21 phys.org piece “The universe is expanding at an accelerating rate—or is it?” Or the “exotic new particle discovered at CERN” earlier this year? The one hat led to a tsunami of ~500 papes posted to arVix within weeks? Since debunked. In the present case, the ‘evidence’ appears even more tenuous. And it’s a well-known bias that when presented with data which are not instantly explainable by known physics, physicists tend to leap at the most exotic possible explanations. New physics is ‘sexy’, basically.

[flagrantflowers]

Originally Posted by ewmayer

In the present case, the ‘evidence’ appears even more tenuous. And it’s a well-known bias that when presented with data which are not instantly explainable by known physics, physicists tend to leap at the most exotic possible explanations. New physics is ‘sexy’, basically.

Could Gravitational waves act as a trigger for systems that are on the cusp of transition? For example, a mass of gas at near fusion pressures has a strong gravitational wave pass through it. Could this, potentially, lead to triggering supernova for systems near collapse? What about staving off transition and providing energy to persist in the current state?

Does density of an arbitrary mass change with velocity to an observer that is travelling at the same velocity (no, I think)? A 'stationary' observer (possibly yes, I think)? Ramifications (I think these maybe ignorant questions)?

[xilman]

Originally Posted by flagrantflowers

Could Gravitational waves act as a trigger for systems that are on the cusp of transition? For example, a mass of gas at near fusion pressures has a strong gravitational wave pass through it. Could this, potentially, lead to triggering supernova for systems near collapse? What about staving off transition and providing energy to persist in the current state?

Undoubtedly so. A wave transfers energy to matter through which it passes. In particular it stretches alternately stretches space in one direction orthogonal to the direction of propagation and compresses it in the other. If the compression is great enough that could be enough to tip it over into gravitational collapse.

Another way to see it is that non-planar gravitational waves themselves contain energy in a localised region of space-time. If they are appropriately focussed the mass-energy density of the waves is enough to cause gravitational collapse, taking with it any matter that happens to be around. Note that this can't happen for plane waves.

[ewmayer]

Originally Posted by flagrantflowers

Could Gravitational waves act as a trigger for systems that are on the cusp of transition? For example, a mass of gas at near fusion pressures has a strong gravitational wave pass through it. Could this, potentially, lead to triggering supernova for systems near collapse? What about staving off transition and providing energy to persist in the current state?

It's certainly possible, though given the weakness of gravity waves as opposed to hydrodynamic ones - the same reason it took so many decades to bring us LIGO - I would guess that more mundane hydrodynamics (such as a nearby supernova going off) and gravitational perturbations due to passing objects would be far more common triggers for collapse of gaseous nebulae. Triggering of supernovae sounds unlikely to me, since the dynamics in the various types of SN tend to involve very 'strong' physics, as opposed to small perturbations of metastable equilibria.

[fivemack]

Originally Posted by ewmayer

It's certainly possible, though given the weakness of gravity waves as opposed to hydrodynamic ones - the same reason it took so many decades to bring us LIGO - I would guess that more mundane hydrodynamics (such as a nearby supernova going off) and gravitational perturbations due to passing objects would be far more common triggers for collapse of gaseous nebulae. Triggering of supernovae sounds unlikely to me, since the dynamics in the various types of SN tend to involve very 'strong' physics, as opposed to small perturbations of metastable equilibria.

I asked a gravitational-wave physicist about this; the problem is that gravitational waves have an inverse-linear rather than inverse-square law to their propagation, and so even very near the source the amount of strain is so small that even the tenth-power dependency of temperature with density for fusion at the hearts of stars doesn't amplify it to anything significant.

(a strain of 100 microns per parsec at 400 megaparsecs is one kilometre per parsec at 40 parsecs, and one kilometre per parsec is five millimetres per astronomical unit)

[jwaltos]

For anyone wishing to explore (please click the link at the bottom of the page to go to the AEI site which is one of the best in the world):
http://grtensor.phy.queensu.ca/
"Theory and experiment in gravitational physics." by Clifford Will.

The software I've used for years and the book dates from the early '80's with a revised
edition in the early 90's and both editions are a good introduction. Online, there is a good site at Caltech: http://www.tapir.caltech.edu/~teviet/Waves/index.html which has a few "flashy thingies" for those interested in a more dynamic presentation.