Is the Big Bang in the Bible?

[Lorizael]

BB Theory is not at all 'useful', indeed no Cosmology of any culture or any times has ever been useful in the material way that we expect 'science' to be, the satisfaction of 'knowing' is all we ever get from cosmology which makes all cosmology dangerously close to philosophy.  I think this is why we consistently feel TOO confident in our cosmology theories, they are not theories which ever get put to work like a real theory should, cosmology isn't allowed to have rough edges (and if it dose it's an observational problem never the fault of the theory).

In contrast GR is actually being used to do stuff like GPS satellites in which time-dilation is critical to the calculations that makes the system work.   Quantum Mechanics is used to design every Solar-Panel and is increasingly becoming relevant in Integrated circuits.  These theories don't need to be monolithic explanations of everything because they work in their respective territories, and the admission that GR is false doesn't prevent us from using it. 

I said Big Bang theory is useful for doing work in astronomy and cosmology, not that it was useful application-wise. That said, it can be argued that the Big Bang theory does have value to physics generally, and thus conceivably to things ordinary people might care about. For example, baryogenesis places constraints on C-symmetry and CP-symmetry, which could aid researchers in discovering post-Standard Model physics.

Also, QM has been useful for computers for 80 years now. Semiconductors wouldn't exist without our understanding of QM.

But we do one more very important think because of falsification, we ACTIVELY search for replacement theories.  People who want to work on Quantum Gravity are not scoffed at and told 'that's impossible' the way anyone who dares to question BB theory is.  So I see a big difference in the kind of attitude that should exist around a falsified (but still taught and studied) BB theory vs the currently unquestionable status it has within the astronomical community.

I'm not inclined to argue this point very strenuously, because I think it's largely one of perception. Before the CMB (and even after it) there was considerable debate about whether the theory was true within the astronomical community. Debate waned as more and more evidence came in. Yeah, scientists shouldn't be ostracized for their views, but at the same time science has limited resources that shouldn't be "wasted."

This is why serious scientists don't spend time trying to come up with free energy machines. Yes, it's possible thermo is wrong, but there's a great deal of evidence to support it so it's probably not worthwhile to waste resources pursuing alternatives. The Big Bang theory is not as solid as the laws of thermodynamics, but doing serious research into astronomy is somewhat more limited than other fields because there are only so many telescopes. I understand why scientists are hesitant to give up telescope time for less well regarded theories.

I agree with eternal meta-stability because I find a 'beginning' of time without an end asymmetrical and illogical (closed universes and eternal ones are both acceptable).

With all due respect, I think this is a terribly unscientific attitude. In fact, it's these kinds of demands about how reality must behave that have, in my opinion, led to the worst mistakes in science. See my earlier discussion about ideas such as the aether and vitalism. They were all based on ideas that reality couldn't possibly be X, and those beliefs ultimately turned out to be a failure of imagination. This is almost precisely why Einstein called his cosmological constant his "greatest blunder." It's a shame he continued to believe that God couldn't possibly throw dice, because as you would seem to agree, QM has been an enormously successful theory.

A far better way to approach is to go piece-meal with theories that explain particular things better then some aspect of BB theory.  The best example of this is MOND which can predict with incredible accuracy all the velocity and structure in galaxies without the freedom of putting dark matter wherever we wish, and on a cluster scale is only needs modest quantities of normal gas between galaxies to work at that level too.  MOND dose not presume to explain the whole cosmos, it just knee-caps one leg of the BB theory with a single very tight observation/model linkage that makes Dark matter look useless by comparison.  I foresee more such little theories emerging and a sticking, then only once these pieces are in place will they be fitted together into a new cosmology.

I'm gonna have to disagree with you here. I don't think approaches like MOND are really a good idea because MOND as described is almost undeniably falsified by other observations, despite its success at describing velocities in galaxies. I don't think it's necessary for astronomical theories to have universal scope, but they must still fit into the broader framework of what is known observationally.

[Rusty Edge]

Reminds me of an old friend of mine, who used to refer to the "Laws of Thermodynamics restated"-

"You can't win. You can't win by cheating. And you're not allowed to quit!"

[Buster's Uncle]

Experts cast doubt on Big Bang bolstering discovery
AFP
By Jean-Louis Santini  11 hours ago



A NASA image shows hundreds of thousands of stars crowded into the swirling core of the Milky Way galaxy (AFP Photo/)



Washington (AFP) - Astrophysicists are casting doubt on what just recently was deemed a breakthrough in confirming how the universe was born: the observation of gravitational waves that apparently rippled through space right after the Big Bang.

If proven to be correctly identified, these waves -- predicted in Albert Einstein's theory of relativity -- would confirm the rapid and violent growth spurt of the universe in the first fraction of a second marking its existence, 13.8 billion years ago.

The apparent first direct evidence of such so-called cosmic inflation -- a theory that the universe expanded by 100 trillion trillion times in barely the blink of an eye -- was announced in March by experts at the Harvard-Smithsonian Center for Astrophysics.

The detection was made with the help of a telescope called BICEP2, stationed at the South Pole.

"Detecting this signal is one of the most important goals in cosmology today," John Kovac, leader of the BICEP2 collaboration at the Harvard-Smithsonian Center for Astrophysics, said at the time.

The telescope targeted a specific area known as the "Southern Hole" outside the galaxy where there is little dust or extra galactic material to interfere with what humans could see.

By observing the cosmic microwave background, or a faint glow left over from the Big Bang, the scientists said small fluctuations gave them new clues about the conditions in the early universe.

The gravitational waves rippled through the universe 380,000 years after the Big Bang, and these images were captured by the telescope, they claimed.

If confirmed by other experts, some said the work could be a contender for the Nobel Prize.


- 'Serious flaws' -

But not everyone is convinced of the findings, with skepticism surfacing recently on blogs and scientific US journals such as Science and New Scientist.

Paul Steinhardt, director of Princeton University's Center for Theoretical Science, addressed the issue in the prestigious British journal Nature in early June.

"Serious flaws in the analysis have been revealed that transform the sure detection into no detection," Steinhardt wrote, citing an independent analysis of the BICEP2 findings.

That analysis was carried out by David Spergel, a theoretical astrophysicist who is also at Princeton.

Spergel queried whether what the BICEP2 telescope picked up really came from the first moments of the universe's existence.

"What I think, it is not certain whether polarized emissions come from galactic dust or from the early universe," he told AFP.

"We know that galactic dust emits polarized radiations, we see that in many areas of the sky, and what we pointed out in our paper is that pattern they have seen is just as consistent with the galactic dust radiations as with gravitational waves."

When using just one frequency, as these scientists did, it is impossible to distinguish between gravitational waves and galactic emissions, Spergel added.

The question will likely be settled in the coming months when another, competing group, working with the European Space Agency's Planck telescope, publishes its results.

That telescope observes a large part of the sky -- versus the BICEP2's two percent -- and carries out measurements in six frequencies, according to Spergel.

"They should revise their claim," he said of the BICEP2 team. "I think in retrospect, they should have been more careful about making a big announcement."

He went on to say that, contrary to normal procedure, there was no external check of the data before it was made public.

Philipp Mertsch of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University said data from Planck and another team should be able to "shed more light on whether it is primordial gravitational waves or dust in the Milky Way."

"Let me stress, however, that what is leaving me (and many of my colleagues) unsatisfied with the state of affairs: If it is polarized dust emission, where is it coming from?" he said in an email.

Kovac, an associate professor of astronomy and physics at Harvard, declined to respond to requests for comment.

Another member of the team, Jamie Bock of the California Institute of Technology, also declined to be interviewed.

At the time of their announcement in March, the scientists said they spent three years analyzing their data to rule out any errors.

http://news.yahoo.com/experts-cast-doubt-big-bang-bolstering-discovery-060400200.html

[Lorizael]

This is science in action as far as I'm concerned.  I'll note that the article's headline is slightly wrong, though. Experts are casting doubt on a discovery that supports inflation specifically, not the Big Bang more generally.

[Buster's Uncle]

As science journalism goes, that's not too bad...

[Lorizael]

I'm totally lost when it comes to the part about dark energy having negative pressure. What does that mean in this context? I assume they aren't comparing it to Earth's atmosphere.

So, near as I can tell, the part about dark energy having negative pressure is just a way to explain it that might make sense without using math. It doesn't really have anything to do with an atmosphere, and I don't think it really gives a good explanation of why dark energy causes the universe's expansion to accelerate. I've been studying up on this, though, and I think I can give a reasonably good explanation.

The universe is composed of essentially three things: matter, radiation, and vacuum. All of these have mass that contributes to the gravity of the universe. In this context, though, it's useful to think of gravity not as a force that pulls things together but as a field with a certain amount of energy (gravitational potential energy). As a rule, fields don't like having energy stored in them. They'd much rather transfer that energy somewhere else.

Think about the electromagnetic field. When you put energy into the electromagnetic field, its response is to generate photons that carry the energy away and hopefully smack into something else. The same happens with gravity. When gravity has energy in its field, it releases it by giving kinetic energy to objects--causing those objects to fall.

Now, as the universe expands, the density of matter and radiation drop. Matter drops at the cube of the expansion rate (because volume is proportional to r^3), and radiation drops at the 4th of the expansion rate (because radiation is also affected by gravitational redshift). The vacuum, however, does not drop with the expansion, because the mass of the vacuum is associated with space itself and doesn't "spread out" as the universe does. The end result is that, eventually, the density of the universe is dominated by vacuum energy.

So, the energy of the gravitational field is defined by this equation: E = -GMm/r. This equation means that at any point a distance r from the center of mass M, there is an amount of energy equal to the mass enclosed in that radius times the mass at the point times the negative of Newton's gravitational constant. Normally, in a system with just mass, increasing the denominator r means the term gets closer to 0, which means the energy in the gravitational field is increasing. This is why r usually shrinks. When r shrinks, the term gets bigger overall, which means it's more negative, which means there's less energy in the gravitational field, which is just the way the field wants things to be.

But there's another way to look at this. The more mass enclosed within the radius r, the more negative the gravitational energy, which again is what the field wants. In a universe dominated by vacuum energy, this has an interesting effect. As r grows, the amount of space grows, so the amount of mass from the vacuum also grows. Specifically, it grows with the cube of the radius, because the volume of space is increasing. So, in that case, when r grows, M grows faster than r does, which means that the numerator grows faster than the denominator, which means the energy becomes even more negative. So in a universe dominated by vacuum energy, the way for the gravitational field to get rid of its energy is by expanding at an exponential rate.

Phew. Hope that makes some sense.

[Rusty Edge]

Thanks, Lorizael.

After two read-throughs, some of the paragraphs make sense alone. The entire post is still confusing to me, but new cosmic concepts generally aren't something which I can grasp at first glance. I'll read it again tonight if I get the chance. Maybe I'll have an intelligent question tomorrow.

[Rusty Edge]

If a vacuum is a void, why does it have mass?..... unless it's not really void and it's full of "Grey dust"?

[Lorizael]

The vacuum has mass because it has energy. It has energy because of quantum mechanics.

To explain in a little more detail, theoretical physics currently operates under a paradigm known as quantum field theory. I mentioned above that "the electromagnetic field" creates photons and sends them off. This is because, in QFT, the fields that transmit forces are said to permeate all of space. So all of space contains the electromagnetic field which wiggles in response to the movement of charged particles. Having fields permeate all of space is the only way to get away from "spooky action at a distance" and the seeming impossibility of faster-than-light communication.

Now, at each point in a field, there is an energy level associated with that field. But because of the Heisenberg uncertainty principle, that energy level can have a minimum but can never be zero. More generally, the uncertainty principle forbids constant energy levels, and zero is obviously a constant. Instead, fields must fluctuate around their lowest energy level, which might be quite close to zero. What those lowest energy levels are has to do with the mass of the particles those fields create and gets into some sticky quantum mechanics. In fact, the the current understanding of the vacuum is that pairs of virtual particles are being created and annihilated constantly in the vacuum.

The point of all that, however, is that even the vacuum is filled with fields that possess an average minimum energy level which contributes to the mass of the universe. This isn't just theoretical rubbish, btw. The "vacuum energy" of the universe has been observed in the Casimir effect, which causes a slight attraction between two closely spaced plates. The reason for this is that the very small width between the two plates places wavelength limits on the particles that can spontaneously manifest, meaning there is less energy between the plates, leading to a lower pressure inside than outside, leading to an attractive force.

But it isn't all as nice as it sounds. Cosmological models put limits on the energy of the cosmological constant (it's very low). And QFT gives a theoretical estimate of what the energy level of the vacuum should be. The estimate it gives is something like 107 orders of magnitude too high. This is known as the vacuum catastrophe and quite possibly the worst prediction in the history of physics. It's obvious that the vacuum isn't that powerful (we would notice), but there isn't yet a good explanation as to why it isn't that powerful and what's going on instead. Nevertheless, QFT has been stupendously accurate in pretty much every other prediction it's ever made, so scientists are sticking with it for now.

[Buster's Uncle]

Nearly a Century Later, Edwin Hubble's Legacy Lives On (Op-Ed)
SPACE.com
By Patrick McCarthy, director, Giant Magellan Telescope Organization  6 hours ago



In this space wallpaper, astronomers using NASA's Hubble Space Telescope have assembled a comprehensive picture of the evolving universe among the most colorful deep space images ever captured by the 24-year-old telescope.


     
Patrick McCarthy was part of the Wide Field Camera 3 science team and currently serves as director of the Giant Magellan Telescope Organization. He contributed this article to Space.com's Expert Voices: Op-Ed & Insights.

In the fall of 1917, after a decade of labor, the 100-inch (2.5-meter) telescope at Mount Wilson in Southern California was dedicated. Edwin Hubble would spend many cold nights at the Newtonian focus of the instrument, which was the world's largest telescope at that time. Now, nearly a century later, another 100-inch telescope — the aptly named Hubble Space Telescope (HST) — has just provided the most complete, informative and breathtaking image of the deep universe.

Hubble and his assistant, former mule skinner Milton Humason, made painstaking, long exposures to obtain the sharpest images and spectra of the spiral nebula. Hubble showed that nebulae are "island universes" like Earth's own Milky Way galaxy, but at vast distances. Hubble improved scientists' understanding of the size of the cosmos by orders of magnitude. More remarkably still, he discovered that the universe of galaxies is not static, but rather expanding at an astonishing rate.

The new Hubble Ultra-Deep Field is humanity's first truly "full color" image of the cosmos. By combining deep ultraviolet with visible light and near-infrared images of distant galaxies, the pan-chromatic deep field allows scientists to trace the birth, life and death of stars across the full span of cosmic time. The Ultra-Deep Field provides an awe-inspiring view of more than 100,000 galaxies — a small but representative sampling of the more than 100 billion galaxies in the observable universe.

Galaxies like Earth's own Milky Way are composed of roughly 100 billion stars. Some, like the sun, emit most of their radiation in the visible band — with wavelengths between 0.3 and 1.0 microns. Others, like the red giant Betelgeuse in Orion, emit copious radiation in the infrared, while the massive young star Rigel, also in Orion, pumps much of its prodigious output of photons in the vacuum ultraviolet, light with wavelengths less than 0.3 microns that is absorbed by ozone in the Earth’s upper atmosphere.

To assemble a full census of the stellar content of a galaxy, and a full census of the contents of the universe, astronomers must sample a broad spectral range — from the deep ultraviolet to the thermal infrared.



Patrick McCarthy was part of the Wide Field Camera 3 science team and currently serves as director of the Giant Magellan Telescope Organization.


If you think of a galaxy as an orchestra — an ensemble of players that work in harmony to produce a whole greater than its parts — the visible light samples the violins and the brass, the infrared captures the bass and kettle drums, while the ultraviolet picks out the flutes, piccolos and triangles.

In the case of galaxies, the ultraviolet-bright stars carry the tune of creation — they trace the formation of stars and the conversion of hydrogen to helium, and then helium to carbon, nitrogen and oxygen, and on through the periodic table to iron. The white-to-yellow stars, the midrange of the galaxy spectral band, is filled by middle-mass and middle-aged stars. The long-lived low-mass dwarf stars are vast in number, and like the bass viola, provide a foundation to the orchestra out of the limelight occupied by the brighter instruments. The young massive stars shine brightly in the ultraviolet for a short time and then exit the stage via spectacular supernova explosions.

The first Hubble Deep Field image, captured in 1994, changed scientists' view of the universe by revealing a rich tapestry of galaxies with shapes and structures foreign to the galaxy shapes that are seen in the universe today. Many are in the throes of violent collisions and mergers that may transform them from one type of galaxy — such as spirals like the Milky Way — into other types, like the massive elliptical galaxies that are dominated by random orbits rather than orderly rotation.

A major technical addition to Hubble's suite of cameras has allowed astronomers to first add the infrared, and now the ultraviolet, to create the Hubble Ultra-Deep Field images. For the first time, astronomers can hear the full orchestra of galaxies and their constituent stars. Wide-Field Camera 3, the instrument that revitalized HST in 2009, is a marvel of technology. It contains two separate cameras — one optimized for the ultraviolet, and the other for the infrared. Each uses optics crafted to optimize performance in the selected waveband and focused on state-of-the-art detectors. The ultraviolet camera uses a charge coupled device (CCD) similar to that found in handheld digital cameras, but optimized for low-light-level work in the harsh environment of space. The infrared camera uses a diode array that is only sensitive to light in the range from 0.6 microns to 1.7 microns. This makes it blind to the thermal radiation from the warm optics on Hubble. By staring deeply into space for hundreds of hours, the camera collected a handful of photons per galaxy — photons that have traveled for billions of years before reaching Hubble's mirror.

The Deep Field provides a rich image of the distant cosmos, but many of the key questions regarding the evolution of the universe require spectroscopy — the dispersal of the light into its constituent colors — to reveal their distances, masses and internal dynamics. Fortunately, there is a new generation of telescopes on the horizon, both in space and on the ground, that promise to revolutionize our understanding of the distant universe.

NASA, the European Space Agency (ESA) and the Canadian Space Agency are poised to launch the successor to Hubble — the James Webb Space Telescope — in 2018. The Webb is optimized for the near- and mid-infrared, and will produce redshifts and internal dynamics for many thousands of galaxies. With its 21-foot-diameter (6.5 meters) primary mirror, cooled to the frigid temperature of minus 387 degrees Fahrenheit (minus 233 degrees Celsius), Webb will have unmatched sensitivity at wavelengths longer than 2 microns.

A new generation of giant telescopes are also under construction here on Earth. These "extremely large telescopes" will have 100 times the light-gathering power and 10 times the angular resolution of Hubble. I am involved in the development of one of these, the Giant Magellan Telescope, being designed by an elite engineering team in Southern California, while its giant mirrors are taking shape in a high-tech optics laboratory in Arizona. Our team has already prepared its future home high in the Chilean Andes, and over the next several years, hundreds of scientists, engineers and construction workers will assemble the 82-foot-diameter (25 m) telescope so that, as the next decade starts, astronomers will have a new tool for exploring the first few hundred million years after the Big Bang. Two other giant telescopes are also under development: the Thirty Meter Telescope in Hawaii, and another in the far north of Chile, the European Extremely Large Telescope.

Newton once wrote, "If I have seen further it is by standing on the shoulders of giants." The next generation of astronomers will, indeed, see further by standing on the shoulders of giants — telescopes like Hubble, Webb and the Giant Magellan Telescope and its brethren. The view will be spectacular.

http://news.yahoo.com/nearly-century-later-edwin-hubbles-legacy-lives-op-192323608.html

[Lorizael]

The JWST has something of a rocky history, btw. Every once in awhile it looks like it's not actually going to get into space. But it has to. It is the (near) future of astronomy.

[Buster's Uncle]

They gotta launch the Webb - this space telescope thingy has really panned out.

[Buster's Uncle]

Universe's Expansion Measured With Unprecedented Precision
SPACE.com
by Nola Taylor Redd, SPACE.com Contributor  2 hours ago



An artist's view of how quasars and BOAs work together to measure the expansion of the universe. Light from distant quasars is absorbed by gas, which is imprinted with a pattern of BOAs from the early universe.



Scientists studying more than 140,000 extremely bright galaxies have calculated the expansion of the universe with unprecedented accuracy.

The distant galaxies, known as quasars, serve as a "standard ruler" to map density variations in the universe. Physicists were able to extend their calculations almost twice as far back in time as has been previously accomplished.

Using the Baryon Oscillation Spectroscopic Survey (BOSS), two teams of physicists have improved on scientists' understanding of the mysterious dark energy that drives the accelerating universe. By nearly tripling the number of quasars previously studied, as well as implementing a new technique, the scientists were able to calculate the expansion rate to 42 miles (68 kilometers) per second per 1 million light-years with greater precision, while looking farther back in time. [8 Baffling Astronomy Mysteries]

Andreu Font-Ribera, of the U.S. Department of Energy's Lawrence Berkeley National Laboratory, led one of the two teams, while Timothée Delubac of EPFL, Switzerland, and France’s Centre de Saclay headed the other one. Font-Ribera presented the new findings in April at a meeting of the American Physical Society in Savannah, Georgia.

The new research "explores a region of the universe that was not explored before," Font-Ribera said.


Stretching the standard ruler

The expanding universe stretches light waves as they travel through it, a process astronomers refer to as redshifting. An object's physical distance from the observer depends on how quickly the universe is expanding.

Baryon acoustic oscillations (BAOs) are sound waves imprinted in large structures of matter in the early universe. Competing forces of inward-pushing gravity and outward, heat-related pressure cause oscillations similar to sound waves in the baryonic, or "normal" matter in the universe.

Dark matter, which interacts with normal matter only gravitationally, stays at the center of the sound wave, while the baryonic matter travels outward, eventually creating a shell at a set radius known as the sound horizon.

Quasars, like other galaxies, are surrounded by dust. Light leaving galaxies streams through that dust, revealing the imprint of the BAOs. Studying this light allows researchers to map the distribution of quasars, as well as the gas in the early universe.

By using BOSS, the largest component of the third Sloan Digital Sky Survey, to map BAOs, scientists can determine how matter is distributed in the early universe. When it comes to measuring the expansion of the universe, BAOs serve as a "standard ruler."

"We think we know its size, and its apparent size depends on how far away it is," Patrick McDonald, of the Canadian Institute for Theoretical Astrophysics, said at the conference.

Previously, astronomers have used BAOs to measure the distances to galaxies in order to determine the distribution of mass in the universe, and thus the universe's expansion rate. But galaxies grow fainter at greater distances, so previous studies were limited to looking back only 6 billion light-years into the universe's 13.8-billion-year lifetime.

Font-Ribera and his team, which included McDonald, pioneered a method of measuring BAOs by using quasars, which are galaxies that are far brighter than normal due to the activity of a supermassive black hole at their center. As matter falls into the black hole, it grows extremely hot, radiating light at far brighter wavelengths and over farther distances than conventional galaxies. This allowed the scientists to measure the mass distribution of the universe out to 12 billion years.

Font-Ribera's research involved approximately 50,000 quasars. The new study published by Delubac's team reviewed nearly three times as many sources, more precisely calculating the expansion rate to an accuracy of 2.2 percent.

"If we looked back to the universe when it was less than a quarter of its present age, we'd see that a pair of galaxies separated by a million light-years would be drifting apart at a velocity of 68 kilometers a second as the universe expands," Font-Ribera said in an accompanying press release.

"The uncertainty is plus or minus only a kilometer and a half per second."


The expanding universe

In the early twentieth century, astronomer Edwin Hubble determined that the galaxies in the universe are all moving away from the Milky Way because the universe is expanding. Further studies led astronomers to conclude that the rate of expansion is speeding up rather than slowing down.

McDonald compared the process to a ball thrown in the air.

"Acceleration is like you throw the ball up, and it starts going up faster and faster," McDonald said. "No normal attractive gravity will do that."

   Astronomers determined that an unseen force, dubbed "dark energy," causes the acceleration. McDonald calls dark energy a "placeholder" because scientists aren't certain what, precisely, it is.

"To me, it seems quite possible that it's related to some fundamental hole in our understanding of physics," he said.

In order to patch that hole, scientists must continue to learn more about dark energy, including its role in accelerating the expansion of the universe.

http://news.yahoo.com/universes-expansion-measured-unprecedented-precision-145252498.html

[Buster's Uncle]

'Big G': Scientists Pin Down Elusive Gravitational Constant
LiveScience.com
By Tia Ghose, Staff Writer  54 minutes ago



A painting of Sir Isaac Newton by Sir Godfrey Kneller, dated to 1689.



A fundamental constant that sets the size of the gravitational force between all objects has finally been pinned down using the quirky quantum behavior of tiny atoms.

The new results could help set the official value of the gravitational constant, and may even help scientists find evidence of extra space-time dimensions, said study co-author Guglielmo Tino, an atomic physicist at the University of Florence in Italy.


Elusive value

According to legend, Sir Isaac Newton first formulated his theory of gravity after watching a falling apple. In Newton's equations, the force of gravity grows with the mass of two objects in question, and the force gets weaker the more distant the objects are from each other. The English polymath knew the object's masses had to be multiplied by a constant, or "big G," in order to arrive at the gravitational force between those two objects, but he wasn't able to calculate its value. ("Big G" is different from "little g," which is the local gravitational acceleration on Earth.)

In 1798, scientist Henry Cavendish calculated big G in order to determine Earth's mass. To do so, Cavendish suspended dumbbells on a wire, with enormous lead spheres placed at different distances nearby, and then measured how much the dumbbells rotated in response to the attractive pull of gravity from the neighboring dumbbell. [6 Weird Facts About Gravity]

Since then, almost every attempt to measure big G has used some variation of Cavendish's method. Many of those experiments got extremely precise values — which didn't agree with one another. That's because it was too difficult to identify all potential sources of error in the complicated systems used, said Holger Müller, an atomic physicist at the University of California, Berkeley, who was not involved in the new study.

"The gravitational force is just super tiny, so anything from air currents to electric charges can give you a false result," Müller told Live Science.

As a result, big G is known with much less precision than other fundamental constants, such as the speed of light or the mass of an electron, Tino told Live Science.


Keeping cool

The big systems didn't seem to be working, so the researchers decided to go very small.

The team cooled rubidium atoms to just above the temperature of absolute zero (minus 459.67 degrees Fahrenheit, or minus 273.15 degrees Celsius), where atoms hardly move at all. The researchers then launched the atoms upward inside a vacuum tube and let them fall, in what's called an atomic fountain.

They also placed several hundred pounds of tungsten nearby.

To see how the tungsten distorted the gravitational field, they turned to quantum mechanics, the bizarre rules that govern subatomic particles. At small scales, particles such as atoms can also behave like waves — meaning they can take two different paths at the same time. So the team split the paths the rubidium atoms took as they fell, and then used a device called an atomic interferometer to measure how the waveforms of those paths shifted. The shift in the peaks and valleys of the paths when they recombined was a result of the gravitational pull of the tungsten masses.

The new measurement of G — 6.67191(99) X 10 ^ -11 meters cubed / kilograms seconds ^2 — isn't as precise as the best measures, but because it uses single atoms, scientists can be more confident the results aren't skewed by hidden errors that foiled the more complicated setups of past experiments, Tino told Live Science.

The achievement is impressive, Müller said.

"I thought this experiment would be close to impossible, because the influence of those masses [on gravitational pull] is just very small," Müller told Live Science. "It's really a great breakthrough."


New value

The new experiment raises the hope that future measurements can finally settle on a more precise value for big G.

The findings also could help scientists discover if something more bizarre is at play. Some theories suggest that extra dimensions could warp the gravitational fields in our own four-dimensional world. These distortions would likely be very subtle and would only be noticeable at very small distances. In fact, others have suggested that the different results other labs have gotten were caused by this extradimensional intrusion, Tino said.

By ruling out methodological errors, the new technique could be used to find evidence of extra dimensions, he said.

The new value of G was published today (June 18) in the journal Nature.

http://news.yahoo.com/big-g-scientists-pin-down-elusive-gravitational-constant-171614687.html

[Buster's Uncle]

Just One Type of Blazar? How Jet-Spewing Galaxies Evolve Over Time
SPACE.com
By Joseph Castro, Space.com Contributor  5 hours ago



Scientists now think that two kinds of active galaxies known as blazars actually represent a hybrid kind of blazar that evolves from one type into the other. Image uploaded June 17, 2014.



The two different classes of jet-spewing active galaxies called blazars may, in fact, be a single hybrid type that evolves over time, according to new research.

The luminous cores of most if not all galaxies contain a supermassive black hole, which is millions or even billions of times more massive than the sun. In some "active galaxies," gas trapped by the black hole's gravity forms a hot accretion disk as it spirals down.

Before crossing the point of no return (the event horizon), this material generates huge amounts of electromagnetic radiation and, in the case of quasars, blasts out two jets of subatomic particles that travel in opposite directions at nearly the speed of light.

Blazars appear to produce more gamma radiation than other types of active galaxies, but this may be because one of their jets is pointed toward Earth. (Blazars are generally defined as quasars that are viewed jet-on).

Astronomers currently recognize two types of blazars. Those known as flat-spectrum radio quasars (FSRQs) have smaller black hole masses and weaker jets but strong accretion disk emissions and much higher luminosities. On the other hand, the type known as BL Lacs are completely dominated by their jets, with accretion disk emissions either being weak or nonexistent.

"We can think of one blazar class as a gas-guzzling car and the other as an energy-efficient electric vehicle," study lead researcher Marco Ajello, an astrophysicist at Clemson University in South Carolina, said in a statement. "Our results suggest that we're actually seeing hybrids, which tap into the energy of their black holes in different ways as they age."

Ajello and his team came to this conclusion after studying how the distribution of blazars changed over time. They collected redshift data on BL Lacs using numerous instruments, including the Hobby-Eberly Telescope at McDonald Observatory in Texas, the Keck Telescope in Hawaii and NASA's Swift satellite. (To measure distances of faraway objects, astronomers rely on redshift, or how much the expansion of space has stretched an object's light to redder wavelengths).

They obtained the distances of about 200 BL Lacs and compared the galaxies' distribution across time with a similar sample of FSRQs. They found that FSRQs began to decline in number around 5.6 billion years ago — the same time at which BL Lacs, particularly those with the most extreme energies, steadily increased in numbers.

"What we think we're seeing here is a changeover from one style of extracting energy from the central black hole to another," said team member Roger Romani, an astrophysicist at the Kavli Institute for Particle Astrophysics and Cosmology in California. That is, the FSRQs became BL Lacs over time.

The idea goes like this: Early in the universe's history, large galaxies grew out of collisions and mergers of smaller galaxies. The activity provided the supermassive black holes with bountiful gas, which resulted in large, bright accretion disks. Some of that gas powered the jets of the "gas-guzzling" FSRQs, while the rest fell into the black holes, increasing their spins.

The galaxy collisions eventually slowed as the universe expanded, leaving less spiraling material for the black holes. The accretion disks became depleted, and the resulting black holes were fast-spinning and more massive than ever.

The accretion energy the FSRQs once had was stored in the increasing rotation and mass of the supermassive black holes. That stored energy allowed the blazars to continue shooting out their particle jets and high-energy emissions as BL Lac objects, even without large accretion disks.

This hybrid blazar idea implies that the luminosity of BL Lacs should decrease as their core black holes continue to lose energy and spin. The researchers hope to test this hypothesis with larger blazar samples.

http://news.yahoo.com/just-one-type-blazar-jet-spewing-galaxies-evolve-171719801.html