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Gnargenox
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18 Jul 2017 14:32

DoctorOfSpace wrote:
Source of the post New breakthrough discovery—every quantum particle travels backwards

Dr Gandalf? Really? lol ok
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18 Jul 2017 18:06

DoctorOfSpace wrote:
Source of the post New breakthrough discovery—every quantum particle travels backwards

Ah, this is bad/sensationalist science reporting.

1)  Every quantum particle is not travelling backwards.  

What they are showing is that the probability current can be opposite the direction of the particle's momentum.  However, probability current density is a tricky concept.  The definition would suggest that it tells you the rate at which particles are moving through a region (like number of particles per area per time), similar to the rate of fluid flow in a river.  But this can be misleading, and in fact cannot be directly measured due to the uncertainty principle.  What is prone to measurement is the plain probability density, which indicates the probability of finding the particle in some region of space.

2)  In their paper they calculate the effect of a particle encountering a potential barrier (i.e. being quickly subjected to some force) on the current density.  What one can find is that there is a probability that particles will be reflected backwards when struck by a force pushing them forwards.  The analogy is to roll a ball toward a cliff, and find that instead of going over the cliff, it gets reflected back at you.  

This is really weird and there is no analogue for it in classical physics.  It is purely quantum mechanical.  But this discovery is not new, though it is not very well known.  I actually stumbled across it myself in a homework problem in my first quantum mechanics course.  I thought that I must have misunderstood my calculation, asked the professor about it, and he said "no, that actually happens."

Paradoxical Reflection in Quantum Mechanics
 
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Zymoox
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19 Jul 2017 00:56

Have you heard about the unusual signals from Ross 128 star?
http://phl.upr.edu/library/notes/ross128
 
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Zymoox
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19 Jul 2017 00:58

Zymoox wrote:
Have you heard about the unusual signals from Ross 128 star?
http://phl.upr.edu/library/notes/ross128

Don't mind. I just saw you were already talking about it.
 
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21 Jul 2017 13:39

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21 Jul 2017 15:27

PlutonianEmpire wrote:

Wow! Good stuff :D. Hope it's going to be added to Space Engine.
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26 Jul 2017 15:36

Destructor1701 wrote:
Planet detection by their radio emissions is pretty fantastic. I hope this technique can be refined to stand alongside transit and radial velocity as a reliable detection method for exoplanets.

i agree, the construction of the one the Square kilometre array will definitely help to listen to signals
 
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27 Jul 2017 16:12

Another search for extrasolar planet moons in Kepler data:

By folding photometric data for 284 Kepler planets (and planet candidates), with radii from ~Earth to ~Jupiter, and at separations from their star of 0.1 to 1.0 AU, they find that analogues of Jupiter's Galilean moons are around less than 38% of these planets (95% confidence). There is a *slight* hint in the data of the existence of a population of "super-Ios," ~half-Earth sized moons orbiting close to their planets (perhaps the exomoon equivalent of hot Jupiters in terms of mass ratio and separation).

Group statistics aside, they find evidence for an exomoon candidate orbiting Kepler-1625b. The possible existence of a "Kepler-1625b I" would be a ~Neptune-sized moon orbiting a 10 Jupiter-mass planet at a distance of ~20 planetary radii. The orbit would be tidally stable.

Since transits of Kepler-1625b have been observed only three times by Kepler (due to its long orbital period of 287 days), it's really hard to be sure that this moon exists. They note that it's possible the "evidence" is an artifact of the data processing. Remember the last exomoon candidate at Kepler-90g turned out to be caused by a pixel sensitivity dropouts in the CCD of Kepler's camera. That being said, the next transit of Kepler-1625b will be in October 2017, and they've secured HST observations to confirm the existence of the moon.

HEK VI: On the Dearth of Galilean Analogs in Kepler and the Exomoon Candidate Kepler-1625b I
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28 Jul 2017 01:04

Finding clear evidence of an exomoon would be amazing. Our instruments and methods are not powerful enough though, there is too much measurement uncertainty to say for sure it's not an artifact...

Could we hope to directly observe one of those with better cameras?
The universe is not required to be in perfect harmony with human ambition.

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Watsisname
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28 Jul 2017 01:55

It is not a problem of cameras so much as a more fundamental problem of optics.  To give an idea, in order to distinguish the Moon from the Earth from a distance of just 4 light years, you require a telescope at least 60 meters in diameter!  For something 10 times farther away, the required telescope size also grows by a factor of 10.  You will also need to block out the glare of the sunlight.

It could be tempting to think that interferometry could help reach the required resolution, but then the problem is that the limiting magnitude isn't good enough.

So discovering exo-moons really is difficult no matter how you try to approach it.  Photometry actually seems like the most plausible way.
 
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28 Jul 2017 02:23

i hope to see more exomoons discovered in the next years with the new telescopes like james webb, Tess and the huge ones on the ground. the next generation of telescopes's first light will be around 2018-2025  :)
i hope that one day soon we will find rocky-earth sized moons around gas giants or just small rocky moons like europa or genymad and titan 
"Exploration is in our nature. We began as wanderers, and we are wanderers still"
-carl sagan
 
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28 Jul 2017 11:37

"Exploration is in our nature. We began as wanderers, and we are wanderers still"
-carl sagan
 
A-L-E-X
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09 Aug 2017 15:04

https://www.forbes.com/sites/brucedorminey/2017/07/21/how-aliens-might-use-network-theory-for-galactic-communications/#25770d002c6e

How Aliens Might Use 'Network Theory' For Galactic Communications

Bruce Dorminey ,

Contributor

I cover over-the-horizon technology, aerospace and astronomy.

Advanced technological civilizations looking for efficient communication from one end of a galaxy to another would best be served by tapping into a network of transiting extrasolar earths. That is, extrasolar earths capable of being observed transiting across the face of their parent stars. Or so says an exoplanet researcher in the U.K.

Kepler-type space observatories out looking for transits of extrasolar earths, could also look for the telltale signatures of optical lasers or even alien macro-engineering projects that might be manipulated to signal another civilization.

pulated to signal another civilization.
Last edited by A-L-E-X on 09 Aug 2017 15:06, edited 1 time in total.
 
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09 Aug 2017 15:05

https://www.scientificamerican.com/arti ... b-crystal/

Exotic Physics Glimpsed for First Time in Lab Crystal

Researchers create a bizarre effect once thought to only occur in intense gravitational fields

• By Philip Ball, Nature magazine on July 21, 2017

Credit: Cláudio Policarpo Getty Images
An exotic effect in particle physics that’s theorized to occur in immense gravitational fields—near a black hole, or in conditions just after the Big Bang—has been seen in a lump of material in a laboratory, physicists report.

A team led by physicist Johannes Gooth at IBM Research near Zurich, Switzerland, say they have seen evidence for a long-predicted effect called the axial–gravitational anomaly. It states that huge gravitational fields—which general relativity describes as the result of enormous masses curving space-time—should destroy the symmetry of particular kinds of particles that usually come in mirror-image pairs, creating more of one particle and less of another.

The kinds of conditions needed to prove this unusual breakdown of a fundamental ‘conservation law’ can’t be created in a laboratory. But the researchers exploited a peculiar parallel between gravity and temperature to create a lab analogue of the anomaly in niobium phosphide crystals. “This anomaly is so hard to measure that even indirect evidence is a major breakthrough,” says team member Adolfo Grushin of the University of California, Berkeley.

Inside the crystal, the effect is as if a drawerful of pairs of gloves were suddenly to acquire an excess of right-handed gloves because some of the left-handed ones had switched handedness. The result, published in Nature, bolsters an emerging view that quantum materials—crystals whose properties are dominated by quantum-mechanical effects—can act as experimental test-beds for physics effects that could only otherwise be seen under exotic circumstances.
 
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09 Aug 2017 15:07

http://www.abc.net.au/news/2017-07-21/g ... ns/8731806

Great Filter theory could explain why we're yet to make alien contact

The World Today
By George Roberts
Updated yesterday at 11:37pm

Photo: Professor Ward says there are hundreds of billions of galaxies like ours, and therefore potentially planets that could sustain life. (ABC North Coast: Samantha Turnbull)
Related Story: Plan to launch rockets in NT being 'seriously' considered, Chief Minister says
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Map: Australia
As humans continue to search for life in space, some experts speculate the so-called Great Filter theory lies behind why nobody is responding to our call.

Why has there never been contact?

• Civilisations likely destroy themselves before mastering communication, travel
• Climate change, over-population may well be Great Filter for humans
• Distances communication must travel to connect with other lifeforms make it unlikely
Despite decades of scanning the skies, so far there has been total radio silence in the human effort to make contact with intelligent alien life forms.

But experts said in the end, humans would likely wipe themselves out before managing to make any contact.

Professor Peter Ward, astrobiologist at the University of Washington, said there were hundreds of billions of galaxies like ours, and therefore potentially billions of planets like Earth, that could sustain life.

"I absolutely believe that in our galaxy alone there are certainly other civilisations," he said.

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