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Category Archives: Physics
Surface tension
Surface tension
New section: to be written
MythBusters: Buried Alive & Falling off of a bridge 10/2003
(1) If a person is falling off a bridge, can they save themselves by throwing a hammer ahead of them to break the surface tension of the water prior to their own impact?
How can cliff divers survive their dives?
http://physics.stackexchange.com/questions/9059/jumping-into-water
objects in motion
Kinematics is the study of objects in motion. It allow us to study displacement, velocity, time and acceleration. Check out our introductory lesson on this study of motion here:
https://kaiserscience.wordpress.com/physics/kinematics/
The new Hi-Fi debate and the science of sound
Music today is listened to almost exclusively through digital compression. The most common digital compression format is called MP3 (MPEG-2 Audio Layer III.) A competing digital compression format is FLAC (Free Lossless Audio Codec.)
Many audio enthusiasts believe that FLAC provides significantly more accurate sound reproduction, which can be heard by listeners. Most audio enthusiasts, however, hold that more is not always better, and that the FLAC format does not produce any audible benefits for listeners. PONO is a highly publicized FLAC-based digital music player, a high-tech MP3 player of sorts, that promises significantly better music reproduction.
Both FLAC proponents and skeptics use math and physics based arguments to explain their position. Here’s a brief overview, with links to articles that have more detail.
Our physics article on sound :
Sources of sound
The physics of sound.
On Cnet, Stephen Shankland writes about the science of sound, in the latest generation of audio devices:
Pono Music’s roaring success on Kickstarter, raising $4.3 million so far, shows that thousands of people believe better audio quality is worth paying for. The company — backed by star musician Neil Young and selling a $400 digital audio player along with accompanying music — promises people will hear a difference between Pono Music and ordinary music that’s “surprising and dramatic.” The company’s promise is based in part on music files that can contain more data than not only conventional MP3 files, but also compact discs.
… Just as some skeptics think 4K TVs is wasted on human eyes, which mostly can’t perceive an image quality improvement over mainstream HD 1080p under normal viewing conditions, others think CD audio technology that’s now more than three decades old is actually very well matched to human hearing abilities. For playback, they’re fine with two key aspects of CD audio encoding: its 16-bit dynamic range, which means audio is measured with a precision of 65,536 levels, and its 44.1kHz “sampling” frequency that means those levels are measured 44,100 times each second.
“From a scientific point of view, there’s no need to go beyond,” said Bernhard Grill, leader of Fraunhofer Institute’s audio and multimedia division and one of the creators of the MP3 and AAC audio compression formats. “It’s always nice to have higher numbers on the box, and 24 bits sounds better than 16 bits. But practically, I think people should much more worry about speakers and room acoustics.”
Pono’s recordings will range from CD-quality 16-bit/44.1kHz to 24-bit/192kHz “ultra-high resolution.” To house the data, Pono follows in the footsteps of the digital audiophile industry by sticking with a file format called FLAC (Free Lossless Audio Codec) that compresses files for smaller sizes but not to the degree of alternatives including MP3 and AAC that throw away some of the original data. The company also is betting its success on a player with better electronics and a catalog of HD music designed to let listeners hear music true to its original sound in the recording studio.
…The idea is that more data allows a higher dynamic range — the span between the loudest and quietest passages of music — and comes closer to the detail of live, original sound….
A prominent part of the case against high-resolution audio is a 2007 study by E. Brad Meyer and David Moran of the Boston Audio Society – that concluded listeners couldn’t tell the difference between SACD and DVD-A music on the one hand and CD-quality versions of the same recordings on the other.
Results of a blind audio test. By E. Brad Meyer and David R. Moran
In that experiment’s 554 tests, listeners correctly identified when a SACD or DVD-A recording compared to a CD only 49.8 percent of the time — in other words, they didn’t do better than randomly guessing.…
Another high-profile non-believer is Christopher “Monty” Montgomery, an engineer who writes codec software for the Xiph.Org Foundation and who works for Firefox developer Mozilla. The most prominent part of his effort is a video arguing that CD quality sound is good enough. Montgomery’s video, illustrated with lucid demonstrations and backed by a blog post, persuasively debunks misconceptions such as the idea that encoding music digitally reduces it to a series of jagged stairsteps instead of the original smooth curves.
24/192 Music Downloads …and why they make no sense:
Video on 24/192 music downloads: D/A and A/D | Digital Show and Tell (Monty Montgomery @ xiph.org)
Montgomery and his allies have yet to persuade everyone on two points, including the idea that 16-bit resolution and 44.1kHz is sufficient.
“Monty is wrong. Twenty-four bits does matter — but for a very small sliver of the music business,” said Mark Waldrep, an audio engineer who’s founder and chief executive of AIX Records and iTrax.com and who focuses on high-resolution audio — including efforts of his own to debunk some claims. And of the sampling frequency he said, “I’d rather err on having those frequencies in the signal rather than assuming we don’t need them.”
But Grill thinks any purported benefit would be lost in the real world. “The limiting factor is the loudspeaker, the room acoustics, and the human ear,” he said.
From “The Digital Myth: Why Digital Audio Sounds Better Than You Think”
By Gordon Reid
Now, perhaps the greatest myth in digital audio relates to the misconception that digital signals are shaped like staircases, and that much of their ‘brittleness’ is a consequence of the steps. This is nonsense. Digital signals are not shaped like anything — they are sequences of numbers. Unfortunately, the type of representation in diagram 8 has led many people to confuse graphics with reality.
Let’s be clear. When the samples in a digital signal are converted back into an analogue signal, they pass through a device called a reconstruction filter. This is the process that makes the Sampling Theorem work in the real world. If there are enough samples and they are of sufficient resolution, the signal that emerges is not only smooth but virtually identical to the analogue signal from which the samples were originally derived. Of course, it’s possible to design a poor reconstruction filter that introduces unwanted changes and artifacts but, again, this is an engineering consideration, not a deficiency in the concept itself.
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Source: Sound bite: Despite Pono’s promise, experts pan HD audio
Another great article on this topic
What is FLAC? The high-def MP3 explained. C|Net
Here is a detailed physics experiment showing an analysis of FLAC and MP3 audio files. The result is that there is no audible difference between any of these formats! Each is equally good. There are, however, significant problems in how iTunes engineers (and probably engineers from other companies) are choosing to compress original recordings. many times they make choices which negatively affect the music. However, those errors are independent of whether one ends up using MP3, FLAC or other formats.
Also see “There are no “stair steps” in digital audio ! What The Matrix can teach us about “resolution””
There are no “stair steps” in digital audio ! What The Matrix can teach us about “resolution”
The nature of reality
What is the ultimate nature of reality? This the core questions of physics, as well as of classical, rationalist philosophy. We now know that this question relates to interpretations of quantum mechanics.
“Those are the kind of questions in play when a physicist tackles the dry-sounding issue of, “what is the correct interpretation of quantum mechanics?” About 80 years after the original flowering of quantum theory, physicists still don’t agree on an answer. Although quantum mechanics is primarily the physics of the very small – of atoms, electrons, photons and other such particles – the world is made up of those particles. If their individual reality is radically different from what we imagine then surely so too is the reality of the pebbles, people and planets that they make up.”
The Many Interpretations of Quantum Mechanics, Graham P. Collins, Scientific American, November 19, 2007
To what can we compare our knowledge of the universe?
The allegory of Plato’s cave
The Allegory of the Cave was presented by the Greek philosopher Plato the Republic (380 BCE) He retells an analogy created by Socrates, about people who think that they know the true nature of reality – however, as the analogy progresses, we find that they have no idea what the real world is like at all.
The idea is that most people don’t actually understand our own real world – and that we never will without philosophical and scientific inquiry.
Socrates says to imagine a cave where people have been imprisoned from childhood. They are chained so that their legs and necks are fixed, forcing them to gaze at the wall in front of them, and not look around at the cave, each other, or themselves
Behind the prisoners is a fire, and between the fire and the prisoners is a raised walkway with a low wall, behind which people walk carrying objects or puppets “of men and other living things”
The masters walk behind the wall – so their bodies do not cast shadows for the prisoners to see. But the objects they carry cast shadows. The prisoners can’t see anything behind them : they only able see the shadows cast on the cave wall in front of them. The sounds of people talking echo off the wall, so the prisoners falsely believe these sounds come from the shadows.
The shadows constitute reality for the prisoners – because they have never seen anything else. They do not realize that what they see are shadows of objects in front of a fire, much less that these objects are inspired by real living things outside the cave
The philosopher (or scientist) is like a prisoner who is freed from the cave and comes to understand that the shadows on the wall do not make up reality at all, for he can perceive the true form of reality – rather than the mere shadows seen by the prisoners.
Plato then supposes that one prisoner is freed: he turns to see the fire. The light would hurt his eyes and make it hard for him to see the objects that are casting the shadows. If he is told that what he saw before was not real but instead that the objects he is now struggling to see are, he would not believe it. In his pain the freed prisoner would turn away and run back to what he is accustomed to, the shadows of the carried objects.
Plato continues: “suppose…that someone should drag him…by force, up the rough ascent, the steep way up, and never stop until he could drag him out into the light of the sun.” The prisoner would be angry and in pain, and this would only worsen when the light of the sun overwhelms his eyes and blinds him.” The sunlight represents the new knowledge that the freed prisoner is experiencing.
Slowly, his eyes adjust to the light of the sun. First he can only see shadows. Gradually he can see reflections of people and things in water, and then later see the people and things themselves. Eventually he is able to look at the stars and moon at night until finally he can look upon the sun itself (516a). Only after he can look straight at the sun “is he able to reason about it” and what it is.
- adapted from “Allegory of the Cave.” Wikipedia, The Free Encyclopedia. 29 May. 2016. Web. 3 Jun. 2016
Another illustration of Plato’s cave.
Are the laws of physics really absolute?
One of the major goals of physics is to emerge from the relative ignorance of the cave, and venture out into an understanding of the real world – how our universe really works.
We have made remarkable progress in doing so – everything we have learned in classical physics over the last two millennia is part of the human adventure.
What we have learned is, in an important sense, “real.” Physics lets us ask specific questions and then use math to make specific answers. We then compare our predictions to the way that universe really works.
Yet we need to be careful – we could make the mistake of using physics equations as if they are absolutely true. Yes, they certainly are true in the sense that they work. But are these math equations the absolute truth themselves – or are they really emerging from a deeper phenomenon? See The laws of physics are emergent phenomenon.
Is nature a simulation?
The simulation hypothesis proposes that our reality is actually some kind of super detailed computer simulation. This hypothesis relies on the development of a simulated reality, a proposed technology that would seem realistic enough to convince its inhabitants. The hypothesis has been a central plot device of many science fiction stories and films.
Simulation hypothesis (Wikipedia)
Video Why Elon Musk says we’re living in a simulation: YouTube, Vox
Elon Musk thinks we’re characters in a computer simulation. He might be right.
Is the Universe a Simulation? Scientists Debate
Nick Bostrom: Are you living in a computer simulation?
Is the universe a hologram?
The holographic principle is a principle of string theories and a supposed property of quantum gravity that states that the description of a volume of space can be thought of as encoded on a lower-dimensional boundary to the region—preferably a light-like boundary like a gravitational horizon.
First proposed by Gerard ‘t Hooft, it was given a precise string-theory interpretation by Leonard Susskind who combined his ideas with previous ones of ‘t Hooft and Charles Thorn.
As pointed out by Raphael Bousso, Thorn observed in 1978 that string theory admits a lower-dimensional description in which gravity emerges from it in what would now be called a holographic way. In a larger sense, the theory suggests that the entire universe can be seen as two-dimensional information on the cosmological horizon. – Wikipedia
Our Universe May Be a Giant Hologram
Study reveals substantial evidence of holographic universe
Space’The Holy Grail for Physicists’: First Evidence Universe is a Hologram Uncovered
To learn more about quantum mechanics
The Cosmic Code: Quantum Physics as the Language of Nature, Heinz R. Pagels
One of the best books on quantum mechanics for general readers. Heinz Pagels, an eminent physicist and science writer, discusses the core concepts without resorting to complicated mathematics. He covers the development of quantum physics. And although this is an intellectually challenging topics, he is one of the few popular physics writers to discuss the development and meaning of Bell’s theorem.
Quantum Reality: Beyond the New Physics, Nick Herbert
Herbert brings us from the “we’ve almost solved all of physics!” era of the early 1900s through the unexpected experiments which forced us to develop a new and bizarre model of the universe, quantum mechanics. He starts with unexpected results, such as the “ultraviolet catastrophe,” and then brings us on a tour of the various ways that modern physicists developed quantum mechanics.
And note that there isn’t just one QM theory – there are several! Werner Heisenberg initially developed QM using a type of math called matrix mechanics, while Erwin Schrödinger created an entirely different way of explaining things using wave mechanics. Yet despite their totally different math languages – we soon discovered that both ways of looking at the world were logically equivalent, and made the same predictions. Herbert discussed the ways that Paul Dirac and Richard Feynman saw QM, and he describes eight very different interpretations of quantum mechanics, all of which nonetheless are consistent with observation…
In Search of Schrödinger’s Cat: Quantum Physics and Reality, John Gribbon
“John Gribbin takes us step by step into an ever more bizarre and fascinating place, requiring only that we approach it with an open mind. He introduces the scientists who developed quantum theory. He investigates the atom, radiation, time travel, the birth of the universe, superconductors and life itself. And in a world full of its own delights, mysteries and surprises, he searches for Schrodinger’s Cat – a search for quantum reality – as he brings every reader to a clear understanding of the most important area of scientific study today – quantum physics.”
External links
The Many Interpretations of Quantum Mechanics, Scientific American
Tom’s Top 10 interpretations of quantum mechanics
Learning Standards
SAT Subject Test: Physics
Quantum phenomena, such as photons and photoelectric effect – Atomic, such as the Rutherford and Bohr models, atomic energy levels, and atomic spectra. Nuclear and particle physics, such as radioactivity, nuclear reactions, and fundamental particles.
AP Physics Curriculum Framework
Essential Knowledge 1.D.1: Objects classically thought of as particles can exhibit properties of waves.
a. This wavelike behavior of particles has been observed, e.g., in a double-slit experiment using elementary particles.
b. The classical models of objects do not describe their wave nature. These models break down when observing objects in small dimensions.
Learning Objective 1.D.1.1:
The student is able to explain why classical mechanics cannot describe all properties of objects by articulating the reasons that classical mechanics must be refined and an alternative explanation developed when classical particles display wave properties.
Essential Knowledge 1.D.2: Certain phenomena classically thought of as waves can exhibit properties of particles.
a. The classical models of waves do not describe the nature of a photon.
b. Momentum and energy of a photon can be related to its frequency and wavelength.
Content Connection: This essential knowledge does not produce a specific learning objective but serves as a foundation for other learning objectives in the course.
A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas (2012)
Electromagnetic radiation can be modeled as a wave of changing electric and magnetic fields or as particles called photons. The wave model is useful for explaining many features of electromagnetic radiation, and the particle model explains other features. Quantum theory relates the two models…. Knowledge of quantum physics enabled the development of semiconductors, computer chips, and lasers, all of which are now essential components of modern imaging, communications, and information technologies
Scaling and biophysics
From Math Bench Biology Modules:
Scaling examines how form and function change as organisms get larger – in other words, how do biological features scale across size? Do they change in meaningful ways as organisms get bigger or smaller? Of course, you can’t even ask these types of questions without having a way of measuring how relationships change mathematically.
Why study these relationships? Well, if you understand how form or functions change as organisms get bigger or smaller, it is possible to learn something fundamental about what underlies the processes or learn about what factors place evolutionary limits on organism growth and adaptations. For instance, determining at what size arthropods can no longer support the weight of their exoskeleton gives us clues about the limits of their growth.
Let’s use a concrete example so you’ll know what we mean. Here is some data on body size and metabolic rate for mammals….
- metabolic rate increases as animals get bigger. That’s because we are specifically interested in total energy consumed (here measured through oxygen consumption). Of course, bigger animals will use more oxygen than smaller ones (think about how big a breath a lion takes compared to a mouse).
- But look at the values adjusted for body size (the last value listed for each species). Mice use a lot more oxygen per gram than a lion. This means that lions use oxygen more efficiently than mice.
- As mammals get bigger, this increase in efficiency is not linear (notice how the steepness of the slope decreases as size increases).
- This means that metabolism does not scale linearly with body size.
“Who cares?” Well, it turns out that how metabolism (and other factors) scales with body size can give important information about which factors are most important in limiting these biological functions. If we can understand that, we understand a lot more about biology!
Math Bench Biology Modules, University of Maryland: Scaling and Power laws
– – –
How scaling affects biology
There are species of animals such as the deer and the elk that are closely related but of different size. Galileo took notice that the bones of the elk are not just proportionally thicker to the bones of the deer – but instead the elk’s bones are even much thicker.
The elk’s bone has to be much thicker to lower the stress in the bone below the breaking point of the bone. Even so, elk and all the other large vertebrates are still more likely of breaking their bones than the more active smaller animals.
http://www.dinosaurtheory.com/scaling.html
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External links
http://www.av8n.com/physics/scaling.htm
The Principle of Scale: A fundamental lesson they failed to teach us at school
The Biology of B-Movie Monsters, Michael C. LaBarbera
Scaling: Why Giants Don’t Exist, Michael Fowler, UVa 10/12/06
See the speed of sound
from http://nerdist.com/watch-the-speed-of-sound-ripple-through-queen-fans-at-live-aid-1985/
By Kyle Hill
Queen’s performance at Live Aid 1985 was only 20 minutes, but it lived on forever. Propped up by an infectiously enthusiastic Freddie Mercury and Brian May’s screaming guitar, the performance has gone on to be regarded as one of the best rock concerts of all time. If you haven’t seen it (above), take a little break to appreciate this supernova of a show.
The other thing you’ll notice is the crowd. They are in near-perfect unison, signing along and gesturing with Mercury’s mesmerizing gyrations. The audience was so in sync, in fact, that the only thing separating their movement was the speed of sound itself.
Watch the GIF below. Can you see the rapid, pulsing ripples that radiate through the fist-pumping masses? This is much faster than an organized wave like you’d see during a baseball game. No one is coordinating the movement, so what is going on?
A little math might help. The venue, Wembley Stadium, goes about 115 yards deep. The time it takes wave in the crowd to go from Mercury to the back of the stadium is maybe 0.3 seconds (a rough approximation). Dividing these two values results in a wave velocity of 340 meters per second. That’s almost exactly Mach 1, or the speed of sound.
Think about that! What you are actually seeing is thousands of people reacting reflexively the show, and what pops out is a wave moving at Mach 1. The people are a visual representation of Queen’s music–a unbridled manifestation of sound. It could only have happened at a show like this, yet another testament to Mercury and the band.
What are fields?
What are fields? What is a gravitational field? Electric field? Magnetic field?
To begin, imagine that our universe is flat. We could describe what’s going on at any point by defining a 2D grid, like graph paper.
We could use a 2D field to show the temperature at any location.
We could draw a 2-d field representing wind speed.
But our universe is 3D: We need 3 dimensions – 3 axes – to describe any point in space. Here’s a #D axis.
Now imagine a three-dimensional grid extending through our world.
(indoor 3D climbing array by Croatian-Austrian artists Sven Jonke, Christoph Katzler and Nikola Radeljković.)
Now imagine this 3D field extending through all of space!
Even more, now consider – what if this isn’t just a mathematical tool? What if some kind of (invisible) field is a real thing, filling all of space?
Physics has discovered that all of space is filled with several different fields: they are literally everywhere – on Earth and in space, between you and me.
These fields are within our bodies. They extend to the visible boundaries of the universe
These fields are not a hypothesis or idea; they are absolutely real – Magnetic fields, gravitational fields, and more,
Our universe seems to be made of two basic things:
particles (like protons, electrons, neutrons)
fields
Can we make these invisible fields become visible?
Sure! Throw a handful of magnetic iron filings around a suspended magnet.
Magnify this image, look carefully. We see each tiny piece of metal pulled along the (otherwise invisible) magnetic field lines.
Consider a horseshoe magnet – it’s a 3D object, with a 3D magnetic field invisibly emanating from it.
Toss a few thousand small iron filings at it – and suddenly those invisible fields become apparent!
At every single point in our universe there is an electric field.
And at every single point in our universe there is also a magnetic field, and a gravitational field, and more!
Every planet creates, and is surrounded by, a magnetic field – and we can easily see its effects! See what it does to a compass needle, as you move to different points on the Earth.
This otherwise invisible field clearly grabs small slivers of metal, and orients them N/S.
That’s not just a “concept” – these fields are real.
You can see the effect of invisible fields with the magnetometer built into your cell phone (yes, there’s an app for that!)
Physics Toolbox Magnetometer: google play
Try this app as you walk around indoors, and then outdoors – everyplace you stand is filled with electric fields, magnetics fields.
Oh, and both of those fields are difference aspects of one greater field, the electro-magnetic field. (We’ll get to that later.)
All of space, everywhere, is filled with this!
Oh, and there is more. You know how regular matter – atoms – has mass? How is that possible? Why do any atoms have mass at all? Why do atoms have the mass that they have, and why can’t atoms move at the speed of light?
While we won’t get into the details here, the answers to those questions come from the fact that there is yet another field permeating the entire universe: the Higgs field.
Here are visualizations of how particles moving through space interact with the Higgs field.
and
Putting it all together
As you move around our world, as space probes fly through outer space, it turns out that every point in space has multiple fields, at the same point, at the same time.
Each one of these fields has a separate value, which changes over time.
Although we can’t see fields directly, we know they are real, and we certainly can “feel” them, measure their effect on particles as they pass through them.
If we had a God’s eye view of the universe, everywhere we look we would see these many different fields, changing in time.
Learning Standards
NGSS
HS-PS2-4 – Use mathematical representations of Newton’s Law of Gravitation and Coulomb’s Law to describe and predict the gravitational and electrostatic forces between objects.
Disciplinary Core Ideas PS2.B: Types of Interactions
Newton’s law of universal gravitation and Coulomb’s law provide the mathematical models to describe and predict the effects of gravitational and electrostatic forces between distant objects.
Forces at a distance are explained by fields (gravitational, electric, and magnetic) permeating space that can transfer energy through space. Magnets or electric currents cause magnetic fields; electric charges or changing magnetic fields cause electric fields.
HS-PS3-2. Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motion of particles (objects) and energy associated with the relative positions of particles (objects).
DCI PS3.A: Definitions of Energy
These relationships are better understood at the microscopic scale, at which all of the different manifestations of energy can be modeled as a combination of energy associated with the motion of particles and energy associated with the configuration (relative position of the particles).
In some cases the relative position energy can be thought of as stored in fields (which mediate interactions between particles). This last concept includes radiation, a phenomenon in which energy stored in fields moves across space.
HS-PS2-4. Use mathematical representations of Newton’s Law of Gravitation and Coulomb’s Law to describe and predict the gravitational and electrostatic forces between objects.
HS-PS2-5. Plan and conduct an investigation to provide evidence that an electric current can produce a magnetic field and that a changing magnetic field can produce an electric current.
DCI PS2.B: Types of Interactions – Forces at a distance are explained by fields (gravitational, electric, and magnetic) permeating space that can transfer energy through space. Magnets or electric currents cause magnetic fields; electric charges or changing magnetic fields cause electric fields. (HS-PS2-4),(HS-PS2-5)
AP Physics Learning Objectives
Essential Knowledge 2.A.1: A vector field gives, as a function of position (and perhaps time), the value of a physical quantity that is described by a vector.
a. Vector fields are represented by field vectors indicating direction and magnitude.
b. When more than one source object with mass or electric charge is present, the field value can be determined by vector addition.
c. Conversely, a known vector field can be used to make inferences about the number, relative size, and location of sources.
Content Connection: This essential knowledge does not produce a specific learning objective but serves as a foundation for other learning objectives in the course.
Essential Knowledge 2.A.2: A scalar field gives, as a function of position (and perhaps time), the value of a physical quantity that is described by a scalar. In Physics 2, this should include electric potential.
a. Scalar fields are represented by field values.
b. When more than one source object with mass or charge is present, the scalar field value can be determined by scalar addition.
c. Conversely, a known scalar field can be used to make inferences about the number, relative size, and location of sources.
Content Connection: This essential knowledge does not produce a specific learning objective but serves as a foundation for other learning objectives in the course.
Gravitational waves
Astrophysicists may finally have discovered gravitational waves
In TechInsider, Dave Mosher writes:
Gravitational waves may have been detected for the first time, but we won’t know for sure until February 11, 2016 — when scientists will either confirm or dispel the rumors, sources close to the matter tell Tech Insider.
Detection of gravitational waves would be unprecedented. Whoever finds them is also likely to pick up a Nobel prize, since the phenomenon would confirm one of the last pieces of Albert Einstein’s famous 1915 theory of general relativity.
Confirming they exist would tell us we’re still on the right track to understanding how the universe works. Failing to find them after all these years might suggest we need to revisit our best explanation for gravity or rethink our most sensitive experiments, or that we simply haven’t looked long enough.
“Gravitational waves are ripples in the fabric of space-time, predicted by Einstein 100 years ago,” Szabi Marka, a physicist at Columbia University, told Tech Insider. “They can be created during the birth and collision of black holes, and can reach us from distant galaxies.”
Black holes are the densest, most gravitationally powerful objects in existence — so a rare yet violent collision of two should trigger a burst of gravitational waves that we could detect here on Earth.
Colliding neutron stars and huge exploding stars, called supernovas, are thought to generate detectable gravitational waves, too.
However, any sort of signal has eluded the planet’s brightest minds and the most advanced experiments for decades. Until now — maybe.
Columbia University in New York City is hosting a “major” event the morning of Thursday February 11, 2016, a source who is close to the matter, but asked not to be named, told Tech Insider.
Another source also confirmed the event but downplayed the significance of the event as anything “major.”
Regardless, several physicists and astronomers with expertise in gravitational wave science are scheduled to attend.
The topic? The latest data from the Laser Interferometer Gravitational-Wave Observatory (LIGO), a $1 billion experiment that has searched for signs of the phenomenon since 2002.
LIGO has two L-shaped detectors that are run and monitored by a collaboration of more than 1,000 researchers from 15 nations, and Marka is one of them.
Marka said that he and his colleagues have worked in the field for more than 15 years and that “these are very exciting and busy times for all of us.”
He also said that Advanced LIGO, an upgrade that went online in September 2015, finished a period of hunting for gravitational waves on January 12, 2016. (That was one day after we saw the first alluring rumors of detection.)
Both LIGO instruments are L-shaped arrays of lasers and mirrors that should be able to detect gravitational waves. Szabi Marka compared them to a pair of giant ears that can “hear” the spacetime ripples that result from black hole mergers, or some other catastrophic event in space. The closer a collision is to Earth, the “louder” the signal should be.
LIGO’s hearing is sensitive enough to detect mind-blowingly small disturbances of space, “much smaller than the size of the atoms the detector is built of,” he said. PhD Comics says LIGO’s level of sensitivity is “like being able to tell that a stick 1,000,000,000,000,000,000,000 meters long has shrunk by 5mm.”
Put another way, detecting a gravitational wave is like noticing the Milky Way — which is about 100,000 light-years wide — has stretched or shrunk by the width of a pencil eraser.
It would be no wonder why it has taken researchers so long to find gravitational waves; it’s terribly difficult work. (Even a truck driving on a nearby road can disturb LIGO, despite the instruments having state-of-the-art vibration-dampening equipment.)
It would also be no wonder why scientists might try to stay tight-lipped about the discovery yet “suck at keeping secrets just like everyone else,” as Jennifer Ouellette wrote at Gizmodo.
But at this point, there’s only one way to know for sure if the latest rumors are true: Wait until Thursday.
Einstein’s wildest prediction could be confirmed within days: Tech Insider
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When Einstein’s General Relativity was first proposed, it was incredibly different from the concept of space and time that came before. Rather than being fixed, unchanging quantities that matter and energy traveled through, they are dependent quantities: dependent on one another, dependent on the matter and energy within them, and changeable over time. If all you have is a single mass, stationary in spacetime (or moving without any acceleration), your spacetime doesn’t change. But if you add a second mass, those two masses will move relative to one another, will accelerate one another, and will change the structure of your spacetime. In particular, because you have a massive particle moving through a gravitational field, the properties of General Relativity mean that your mass will get accelerated, and will emit a new type of radiation: gravitational radiation.
This gravitational radiation is unlike any other type of radiation we know. Sure, it travels through space at the speed of light, but it itself is a ripple in the fabric of space. It carries energy away from the accelerating masses, meaning that if the two masses orbit one another, that orbit will decay over time. And it’s that gravitational radiation — the waves that cause ripples through space — that carries the energy away. For a system like the Earth orbiting the Sun, the masses are so (relatively) small and the distances so large that the system will take more than 10^150 years to decay, or many, many times the current age of the Universe. (And many times the lifetime of even the longest-lived stars that are theoretically possible!) But for black holes or neutron stars that orbit each other, those orbital decays have already been observed.
We suspect there are even stronger systems out there that we simply haven’t been able to detect, like black holes that spiral into and merge with one another. These should exhibit characteristic signals, like an inspiral phase, a merger phase, and then a ringdown phase, all of which result in the emission of gravitational waves that Advanced LIGO should be able to detect. The way the Advanced LIGO system works is nothing short of brilliant, and it takes advantage of the unique radiation of these gravitational waves. In particular, it takes advantage of how they cause spacetime to respond.
What Will It Mean If LIGO Detects Gravitational Waves? – Forbes
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Detection range of AdvLIGO
LIGO and Gravitational Waves: A Graphic Explanation
Tesla and wireless power transmission
Nikola Tesla is one of the great scientists of the 20th century. He patented close to 300 inventions in electrical and mechanical engineering.
Many of Nikola Tesla’s inventions actually work. However, there are many urban legends surrounding his work, some of which have become the basis of conspiracy theories. Perhaps the most widely known is related to Tesla’s discovery that electrical power can be transmitted wirelessly, through the air, from one device to another.
Tesla demonstrated that some power from a Tesla coil could effectively be used to power light bulbs tens or hundreds of feet away. He then envisioned extending the power and range of these devices: he wanted to build a remote power station which could wirelessly power entire cities and towns. However, Tesla never actually worked through the math to prove that this would be efficient or possible, nor did he even demonstrate this level of usefulness.
There is a belief that Tesla “proved” that these towers could wirelessly power cities, and that either the government, or power companies, conspired to keep the details of how this works secret. Electrical engineers and physicists, however, hold that not only is there no conspiracy, but that basic laws of physics show that Tesla’s proposal was unworkable in practice. Below you will find details on why it does not work for large geographical areas.
The information below has been excerpted & adapted from https://en.wikipedia.org/wiki/Wireless_power (1/29/16)
Also see “The Cult of Nikola Tesla”
Inventor Nikola Tesla performed the first experiments in wireless power transmission at the turn of the 20th century. He has done more to popularize the idea than any other individual. From 1891 to 1904 he experimented with transmitting power by inductive and capacitive coupling, using spark-excited radio frequency resonant transformers, now called Tesla coils, which generated high AC voltages. With these he was able to transmit power for short distances without wires.
He found he could increase the distance by using a receiving LC circuit tuned to resonance with the transmitter’s LC circuit, using resonant inductive coupling.
At his Colorado Springs laboratory during 1899–1900, by using voltages of the order of 10 mega-volts generated by an enormous coil, he was able to light three incandescent lamps at a distance of about one hundred feet.
The resonant inductive coupling which Tesla pioneered is now a familiar technology used throughout electronics and is currently being widely applied to short-range wireless power systems.
The inductive and capacitive coupling used in Tesla’s experiments is a “near-field” effect, so it is not able to transmit power long distances. However, Tesla was obsessed with developing a wireless power distribution system that could transmit power directly into homes and factories, as proposed in his visionary 1900 article in Century magazine.
He claimed to be able to transmit power on a worldwide scale, using a method that involved conduction through the Earth and atmosphere. Tesla believed that the entire Earth could act as an electrical resonator.
As such, by driving current pulses into the Earth at its resonant frequency from a grounded Tesla coil working against an elevated capacitance, the potential of the Earth could be made to oscillate, and this alternating current could be received with a similar capacitive antenna tuned to resonance with it at any point on Earth.
Another of his ideas was to use balloons to suspend transmitting and receiving electrodes in the air above 30,000 feet (9,100 m) in altitude, where the pressure is lower. At this altitude, Tesla claimed, an ionized layer would allow electricity to be sent at high voltages (millions of volts) over long distances.
In 1901, Tesla began construction of a large high-voltage wireless power station, now called the Wardenclyffe Tower, at Shoreham, New York. Although he promoted it to investors as a transatlantic radiotelegraphy station, he also intended it to transmit electric power as a prototype transmitter for a “World Wireless System” that was to broadcast both information and power worldwide.
By 1904 his investors had pulled out, and the facility was never completed. Although Tesla claimed his ideas were proven, he had a history of failing to confirm his ideas by experiment, and there seems to be no evidence that he ever transmitted significant power beyond the short-range demonstrations above.
The only report of long-distance transmission by Tesla is a claim – not found in reliable sources – that in 1899 he wirelessly lit 200 light bulbs at a distance of 26 miles (42 km).
There is no independent confirmation of this putative demonstration; Tesla did not mention it, and it does not appear in his meticulous laboratory notes. It originated in 1944 from Tesla’s first biographer, John J. O’Neill, who said he pieced it together from “fragmentary material… in a number of publications”.
In the 110 years since Tesla’s experiments, efforts using similar equipment have failed to achieve long distance power transmission, and the scientific consensus is his World Wireless system would not have worked. Tesla’s world power transmission scheme remains today what it was in Tesla’s time, a fascinating dream.
Tesla’s Big Mistake. Amasci.com – William Beaty
The real science of non-Hertzian waves, By Paul Nicholson
Wireless Energy Transfer, By Yue Ma
Advanced materials
Wireless Power Transmission: From Far-Field to Near-Field
KaiserScience 