An artist’s impression of a jet emanating from NGC 4993
Image credit: J.A. Biretta et al / NASA / ESA / Hubble Heritage Team
/ STScI / AURA / Sci-News.com.
ELECTRIC UNIVERSE PING!
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Posted on 09/13/2018 12:13:34 PM PDT by ETL
Radio observations using a combination of NSF’s Very Long Baseline Array, the Karl G. Jansky Very Large Array and the Robert C. Byrd Green Bank Telescope have revealed that a fast-moving jet of particles broke out into interstellar space after a pair of neutron stars merged in NGC 4993, a lenticular galaxy approximately 130 million light-years from Earth.
-snip-
Called GW170817, the merger of two neutron stars sent gravitational waves rippling through space. It was the first event ever to be detected both by gravitational waves and electromagnetic waves, including gamma rays, X-rays, visible light, and radio waves.
The aftermath of the merger, was observed by orbiting and ground-based telescopes around the world.
Astrophysicists watched as the characteristics of the received waves changed with time, and used the changes as clues to reveal the nature of the phenomena that followed the merger.
One question that stood out was whether or not the event had produced a narrow, fast-moving jet of material that made its way into interstellar space.
That was important, because such jets are required to produce the type of gamma ray bursts that theorists had said should be caused by the merger of neutron-star pairs.
The answer came when Dr. Kunal Mooley of the National Radio Astronomy Observatory (NRAO) and Caltech and co-authors discovered that a region of radio emission from the GW170817 merger had moved, and the motion was so fast that only a jet could explain its speed.
“We measured an apparent motion that is four times faster than light. That illusion, called superluminal motion, results when the jet is pointed nearly toward Earth and the material in the jet is moving close to the speed of light,” Dr. Mooley said.
(Excerpt) Read more at sci-news.com ...
Have no idea what you are talking about.
I merely emphasized that the article was about appearance and illusion.
In 1998, Danish physicist Lene Vestergaard Hau led a combined team from Harvard University and the Rowland Institute for Science which succeeded in slowing a beam of light to about 17 meters per second,[1] and researchers at UC Berkeley slowed the speed of light traveling through a semiconductor to 9.7 kilometers per second in 2004.
Hau and her colleagues later succeeded in stopping light completely, and developed methods by which it can be stopped and later restarted.[2][3] This was in an effort to develop computers that will use only a fraction of the energy of today’s machines.[4]
In 2005, IBM created a microchip that can slow down light, fashioned out of fairly standard materials, potentially paving the way toward commercial adoption.[5]
Background
When light propagates through a material, it travels slower than the vacuum speed, c. This is a change in the phase velocity of the light and is manifested in physical effects such as refraction. This reduction in speed is quantified by the ratio between c and the phase velocity. This ratio is called the refractive index of the material. Slow light is a dramatic reduction in the group velocity of light, not the phase velocity. Slow light effects are not due to abnormally large refractive indices, as which will be explained below.
The simplest picture of light given by classical physics is of a wave or disturbance in the electromagnetic field. In a vacuum, Maxwell’s equations predict that these disturbances will travel at a specific speed, denoted by the symbol c. This well-known physical constant is commonly referred to as the speed of light.
The postulate of the constancy of the speed of light in all inertial reference frames lies at the heart of special relativity and has given rise to a popular notion that the “speed of light is always the same”. However, in many situations light is more than a disturbance in the electromagnetic field.
Light traveling within a medium is no longer a disturbance solely of the electromagnetic field, but rather a disturbance of the field and the positions and velocities of the charged particles (electrons) within the material. The motion of the electrons is determined by the field (due to the Lorentz force) but the field is determined by the positions and velocities of the electrons (due to Gauss’ law and Ampère’s law).
The behavior of a disturbance of this combined electromagnetic-charge density field (i.e. light) is still determined by Maxwell’s equations, but the solutions are complicated because of the intimate link between the medium and the field.
Understanding the behavior of light in a material is simplified by limiting the types of disturbances studied to sinusoidal functions of time. For these types of disturbances Maxwell’s equations transform into algebraic equations and are easily solved. These special disturbances propagate through a material at a speed slower than c called the phase velocity.
The ratio between c and the phase velocity is called the refractive index or index of refraction of the material (n). The index of refraction is not a constant for a given material, but depends on temperature, pressure, and upon the frequency of the (sinusoidal) light wave. This latter leads to an effect called dispersion.
A human perceives the intensity of the sinusoidal disturbance as the brightness of the light and the frequency as the color. If a light is turned on or off at a specific time or otherwise modulated, then the amplitude of the sinusoidal disturbance is also time-dependent. The time-varying amplitude does not propagate at the phase velocity but rather at the group velocity.
The group velocity depends not only on the refractive index of the material, but also the way in which the refractive index changes with frequency (i.e. the derivative of refractive index with respect to frequency).
Slow light refers to a very low group velocity of light. If the dispersion relation of the refractive index is such that the index changes rapidly over a small range of frequencies, then the group velocity might be very low, thousands or millions of times less than c, even though the index of refraction is still a typical value (between 1.5 and 3.5 for glasses and semiconductors).
Different ways to achieve slow light
There are many mechanisms which can generate slow light, all of which create narrow spectral regions with high dispersion, i.e. peaks in the dispersion relation. Schemes are generally grouped into two categories: material dispersion and waveguide dispersion.
Material dispersion mechanisms such as electromagnetically induced transparency (EIT), coherent population oscillation (CPO), and various four-wave mixing (FWM) schemes produce a rapid change in refractive index as a function of optical frequency, i.e. they modify the temporal component of a propagating wave. This is done by using a nonlinear effect to modify the dipole response of a medium to a signal or “probe” field.
Waveguide dispersion mechanisms such as photonic crystals, coupled resonator optical waveguides (CROW), and other micro-resonator structures[6] modify the spatial component (k-vector) of a propagating wave. Slowlight can also be achieved by exploiting the dispersion properties of planar waveguides realized with single negative metamaterials (SNM)[7][8] or double negative metamaterials (DNM).[9]
A predominant figure of merit of slow light schemes is the Delay-Bandwidth Product (DBP). Most slow light schemes can actually offer an arbitrarily long delay for a given device length (length/delay = signal velocity) at the expense of bandwidth. The product of the two is roughly constant.
A related figure of merit is the fractional delay, the time a pulse is delayed divided by the total time of the pulse. Plasmon induced transparency – an analog of EIT - provides another approach based on the destructive interference between different resonance modes. Recent work has now demonstrated this effect over a broad transparency window across a frequency range greater than 0.40 THz.[10]
Potential use
Slow light could be used to greatly reduce noise, which could allow all types of information to be transmitted more efficiently. Also, optical switches controlled by slow light [11] could cut power requirements a million-fold compared to switches now operating everything from telephone equipment to supercomputers.[1] Slowing light could lead to a more orderly traffic flow in networks.
Meanwhile, slow light can be used to build interferometers that are far more sensitive to frequency shift as compared to conventional interferometers. This property can be used to build better, smaller frequency sensors and compact high resolution spectrometers. Also, slow light can be used in optical quantum memory.
> “In their defense they are building data on an event that happened about 140 million years ago.”
I was probably a lot faster when it was younger.
Warp 4
What is the possibility of using something like this to power space craft?
I wonder if the “superluminal motion” defense will work for that speeding ticket.
Captain! I canna na hold her together much longer at this power level!!
“We measured an apparent motion that is four times faster than light. That illusion, called superluminal motion, results when the jet is pointed nearly toward Earth and the material in the jet is moving close to the speed of light,” Dr. Mooley said.
Ok, I’m confused, the material in the jet is moving at
light speed but something ( for want of a better word)
or the appearance of something is moving four times faster?
Didn’t know anything could do that?
Enough with the negative waves, Man!
Just tell the judge, that, since motion is "relative", and not absolute, it is unclear whether you were moving, or if you were sitting still and the road was moving toward you.
Speed of Light May Not Be Constant, Physicists Say - Live Science
https://www.livescience.com/29111-speed-of-light-not-constant.html
*ping*
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Their problem is one of over-reliance on theoretical models, and consensus based paradigms.
Real science should be based on hard facts borne of observed phenomena, not abstract mathematical calculations and theoretical postulates.
Maybe the observers blinked....
“What is the speed minimum of light? How slow can it move?”
Well, c is the speed of light in a vacuum, it always moves at that speed in a vacuum, it never slows down. It can be slowed down when moving through a medium, but I think the individual waves or photons are still moving at c, it is just that they are being absorbed and re-emitted by the matter they move through, so that causes the aggregate speed to drop.
So light can slow as it passes through a medium but then re-accelerate once it clears the medium? At a photon level, what energy causes the re-acceleration?
I am not a physicist and not trying to be coy. But I have questioned some of the science as it pertains to some “known” constants when applied to the whole universe. The age and size of our universe is based on the observable light and the red shift in that light (among other things). If lights path can be altered by gravitational waves (black holes) and magnetic waves and even slowed as it passes through gaseous portions of space, how is the observable light measured accurately? Or is it’s trajectory and speed deviation irrelevant/inconsequential?
“So light can slow as it passes through a medium but then re-accelerate once it clears the medium? At a photon level, what energy causes the re-acceleration?”
No, technically the individual packets or photons of light are never slowing down. What is happening is that the photons are getting absorbed by matter that they pass through, and then other photons are re-emitted, and there is some gap of time between that, so it causes the speed of the entire wave (the phase velocity) to slow down.
Thanks Swordmaker.
The Starship Enterprise can travel at 6,400C or 0.73 light years/light hour.
Which one?...................
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