The Lagrangian points are the five locations in an orbital system where the combined gravitational force of two large masses is exactly canceled out by the centrifugal force arising from the rotating reference frame.
At these five points, the net force on a third body (of negligible mass) is 0, allowing the third object to be completely stationary relative to the two other masses. That is, when placed at any of these points, the third body stays perfectly still in the rotating frame.
The first image shows the fields due to the first mass, the second mass, and the rotating reference frame. When added together, these fields generate the effective field shown in the second image. The five Lagrangian points are indicated with gray spheres.
The first three Lagrangian points (labeled L1, L2, and L3) lie in line with the two larger bodies and are considered metastable equilibria. L4 and L5 lie 60° ahead of and behind the second body in its orbit and are considered stable equilibria.
Lagrangian points offer unique advantages for space research, and the Lagrangian points of the Sun-Earth system are currently home to four different satellites.Mathematica code posted here.
8 miniature galaxies to shift your cosmic perspective
It’s easy to feel small when pondering the size of the universe and the smallness of Earth in comparison. Imgur user ScienceLlama has taken this existential crisis to the next level with this collection of itty-bitty universe photos.
NGC 6946 The Fireworks Galaxy
NGC 6946 is a medium-sized, face-on spiral galaxy about 22 million light years away from Earth. In the past century, eight supernovas have been observed to explode in the arms of this galaxy.
Image credit: X-ray: NASA/CXC/MSSL/R.Soria et al, Optical: AURA/Gemini OBs
What if the universe had no beginning, and time stretched back infinitely without a big bang to start things off? That’s one possible consequence of an idea called “rainbow gravity” so-named because it posits that gravity’s effects on spacetime are felt differently by different wavelengths of light, aka different colors in the rainbow.
Rainbow gravity was first proposed 10 years ago as a possible step toward repairing the rifts between the theories of general relativity (covering the very big) and quantum mechanics (concerning the realm of the very small). The idea is not a complete theory for describing quantum effects on gravity, and is not widely accepted. Nevertheless, physicists have now applied the concept to the question of how the universe began, and found that if rainbow gravity is correct, spacetime may have a drastically different origin story than the widely accepted picture of the big bang.
According to Einstein’s general relativity, massive objects warp spacetime so that anything traveling through it, including light, takes a curving path. Standard physics says this path shouldn’t depend on the energy of the particles moving through spacetime, but in rainbow gravity, it does. “Particles with different energies will actually see different spacetimes, different gravitational fields” says Adel Awad of the Center for Theoretical Physics at Zewail City of Science and Technology in Egypt, who led the new research, published in October in the Journal of Cosmology and Astroparticle Physics. The color of light is determined by its frequency, and because different frequencies correspond to different energies, light particles (photons) of different colors would travel on slightly different paths though spacetime, according to their energy.
The effects would usually be tiny, so that we wouldn’t notice the difference in most observations of stars, galaxies and other cosmic phenomena. But with extreme energies, in the case of particles emitted by stellar explosions called gamma-ray bursts, for instance, the change might be detectable. In such situations photons of different wavelengths released by the same gamma-ray burst would reach Earth at slightly different times, after traveling somewhat altered courses through billions of light-years of time and space. “So far we have no conclusive evidence that this is going on” says Giovanni Amelino-Camelia, a physicist at the Sapienza University of Rome who has researched the possibility of such signals. Modern observatories, however, are just now gaining the sensitivity needed to measure these effects, and should improve in coming years.
The extreme energies needed to bring out strong consequences from rainbow gravity, although rare now, were dominant in the dense early universe, and could mean things got started in a radically different fashion than we tend to think. Awad and his colleagues found two possible beginnings to the universe based on slightly different interpretations of the ramifications of rainbow gravity. In one scenario, if you retrace time backward, the universe gets denser and denser, approaching an infinite density but never quite reaching it. In the other picture the universe reaches an extremely high, but finite, density as you look back in time and then plateaus. In neither case is there a singularity - a point in time when the universe is infinitely dense - or in other words, a big bang. “This was, of course, an interesting result, because in most cosmological models, we have singularities” Awad says. The result suggests perhaps the universe had no beginning at all, and that time can be traced back infinitely far.
Whereas it is too soon to know if these scenarios might describe the truth, they are intriguing. “This paper and a few other papers show there could be a rightful place in cosmology for this idea [of rainbow gravity], which is encouraging to me” says Amelino-Camelia, who was not involved in the study, but has researched frameworks for pursuing a quantum theory of gravity. “In quantum gravity we are finding more and more examples where there is this feature which you may call rainbow gravity. It is something that is increasingly compelling.”
Yet the concept has its critics. “It’s a model that I do not believe has anything to do with reality” says Sabine Hossenfelder of the Nordic Institute for Theoretical Physics. This idea is not the only way to do away with the big bang singularity, she adds. “The problem isn’t to remove the singularity, the problem is to modify general relativity in a consistent way, so that one still reproduces all its achievements and that of the Standard Model [of particle physics] in addition.”
Lee Smolin of the Perimeter Institute for Theoretical Physics in Ontario, who first suggested the idea of rainbow gravity along with Joao Magueijo of Imperial College London, says that, in his mind, rainbow gravity has been subsumed in a larger idea called relative locality. According to relative locality, observers in different locations across spacetime will not agree on where events take place; in other words, location is relative. Relative locality is a deeper way of understanding the same idea as rainbow gravity, Smolin says. The new paper by Awad and his colleagues “is interesting,” he adds, “but before really believing the result, I would want to redo it within the framework of relative locality. There are going to be problems with locality the way it’s written that the authors might not be aware of.”
In the coming years researchers hope to analyze gamma-ray bursts and other cosmic phenomena for signs of rainbow gravity effects. If they are found, it could mean the universe has a more “colorful” history than we knew.
According to Albert Einstein’s theory of general relativity, black holes are uninhabitable chasms of space-time that end in a “singularity,” or a mass of infinite density. It’s a place so bleak that even the laws of physics break down there. But what if black holes aren’t so forbidding? What…
Researchers Jorge Pullin from Lousiana State University, and Rodolfo Gambini from the University of the Republic in Montevideo, Uruguay, crunched the numbers to see what would happen inside a black hole under the parameters of LQG. What they found was far different from what happens according to general relativity alone: there was no singularity. Instead, just as the black hole began to squeeze tight, it suddenly loosened its grip again, as if a door was being opened.
It might help to conceptualize exactly what this means if you imagine yourself traveling into a black hole. Under general relativity, falling into a black hole is, in some ways, much like falling into a very deep pit that has a bottom, only instead of hitting the bottom, you get pressed into a single point — a singularity — of infinite density. With both the deep pit and the black hole, there is no “other side.” The bottom stops your fall through the pit, and the singularity “stops” your fall through the black hole (or at least, at the singularity it no longer makes sense to say you’re “falling”).
Your experience would be much different traveling into a black hole according to LQG, however. At first you might not notice the difference: gravity would increase rapidly. But just as you were nearing what ought to be the black hole’s core — just as you’re expecting to be squashed into the singularity — gravity would instead begin to decrease. It would be as if you were swallowed, only to be spit out on the other side.
In other words, LQG black holes are less like holes and more like tunnels, or passageways. But passageways to where? According to the researchers, they could be shortcuts to other parts of our universe. Or they could be portals to other universes entirely.
Interestingly, this same principle can be applied to the Big Bang. According to conventional theory, the Big Bang started with a singularity. But if time is rewound according to LQG instead, the universe does not begin with a singularity. Rather, it collapses into a sort of tunnel, which leads into another, older universe. This has been used as evidence for one of the Big Bang’s competing theories: the Big Bounce.
Scientists don’t have enough evidence to decide whether this new theory is actually true, but LQG does have one thing going for it: it’s more beautiful. Or rather, it avoids certain paradoxes that conventional theories do not. For instance, it avoids theblack hole information paradox. According to relativity, the singularity inside a black hole operates as a sort of firewall, which means that information that gets swallowed by the black hole gets lost forever. Information loss, however, is not possible according to quantum physics.
Since LQG black holes have no singularity, that information need not be lost.
"Information doesn’t disappear, it leaks out," said Jorge Pullin.
my theory is that black holes are portals to denser realities until you get to the core where the most dense energy is.. it would be collecting all the energy and at the same expanding the universe in doing so
bro just go in there with a cell phone and call us from the other side.
YTMND’s presentation of our future in all its horrifying glory.
Rare mesons may be influencing particles, but scientists will have to wait until 2015 to fully test their hypotheses.
Wrapping my mind around this
The fusion driven rocket test chamber at the UW Plasma Dynamics Lab in Redmond. The green vacuum chamber is surrounded by two large, high-strength aluminum magnets. These magnets are powered by energy-storage capacitors through the many cables connected to them.
University of Washington researchers and scientists at a Redmond-based space-propulsion company are currently building components of a fusion-powered rocket, which could enable astronauts to travel to Earth’s neighboring planet Mars within weeks instead of months, at speeds considerably faster than feasible until now. The current travel speeds using fuel rockets make Mars travel a journey of about four years but the new fusion technology being tested by researchers at the University of Washington promises that in 30 to 90 days.
The lab tests have proven to be successful on each part of the process and the scientists are now planning to combine the sections into a one final and overall test.
“Using existing rocket fuels, it’s nearly impossible for humans to explore much beyond Earth,” said lead researcher John Slough, a UW research associate professor of aeronautics and astronautics. “We are hoping to give us a much more powerful source of energy in space that could eventually lead to making interplanetary travel commonplace.”
The team has developed a technology using a special type of plasma that will be encased in a magnetic field. When the plasma is compressed with high pressure by the magnetic field, nuclear fusion takes place.
The process has successfully been tested by researchers and they plan on having the first full test to be done by the end of this summer.
In practice the powerful magnetic field causes large metal rings surrounding the plasma to implode which will compress it to the point of fusion. The process takes only a few microseconds but that will be enough to release heat and ionize the rings that form a shell around the plasma. The super-heated ionized metal, in turn, ejects out from the rocket at a high velocity pushing the rocket forward. Repeating the process in intervals of about 30 seconds or more can propel a spaceship.
The research was funded by NASA in hopes that the technology would ultimately replace rocket fuel and yield to much faster spacecrafts that ever built before. Scientist say that just a grain size of the material from the plasma used can equal to a gallon of rocket fuel. That by itself will reduce the size of the spacecraft and the payload considerably making deep space travel much more cost effective.
All I need now is a 3D printer and I’m going to Mars.
This is ridiculous. The nearest star to the Moon is the Sun, which is on average 150 MILLION kilometers away, and has a surface temperature of ~10 million degrees. Have fun landing among that.
The Standard Model is the simplest set of ingredients - elementary particles - needed to make up the world we see in the heavens and in the laboratory
• Quarks combine together to make, for example, the proton and neutron - which make up the nuclei of atoms today - though more exotic combinations were around in the Universe’s early days
• Leptons come in charged and uncharged versions; electrons - the most familiar charged lepton - together with quarks make up all the matter we can see; the uncharged leptons are neutrinos, which rarely interact with matter
• The “force carriers” are particles whose movements are observed as familiar forces such as those behind electricity and light (electromagnetism) and radioactive decay (the weak nuclear force)
• The Higgs boson came about because although the Standard Model holds together neatly, nothing requires the particles to have mass; for a fuller theory, the Higgs - or something else - must fill in that gap.
Scientists say they may be able to determine the eventual fate of the cosmos as they probe the properties of the Higgs boson.
A concept known as vacuum instability could result, billions of years from now, in a new universe opening up in the present one and replacing it.
It all depends on some precise numbers related to the Higgs that researchers are currently trying to pin down.
A “Higgs-like” particle was first seen at the Large Hadron Collider last year.
Associated with an energy field that pervades all space, the boson helps explain the existence of mass in the cosmos. In other words, it underpins the workings of all the matter we see around us.
Since detecting the particle in their accelerator experiments, researchers at the Geneva lab and at related institutions around the world have begun to theorise on the Higgs’ implications for physics.
One idea that it throws up is the possibility of a cyclical universe, in which every so often all of space is renewed.
"It turns out there’s a calculation you can do in our Standard Model of particle physics, once you know the mass of the Higgs boson," explained Dr Joseph Lykken.
"If you use all the physics we know now, and you do this straightforward calculation - it’s bad news.
"What happens is you get just a quantum fluctuation that makes a tiny bubble of the vacuum the Universe really wants to be in. And because it’s a lower-energy state, this bubble will then expand, basically at the speed of light, and sweep everything before it," the Fermi National Accelerator Laboratory theoretician told BBC News.
It was not something we need worry about, he said. The Sun and the Earth will be long gone by this time.
Dr Lykken was speaking here in Boston at theannual meeting of the American Association for the Advancement of Science(AAAS).
He was participating in a session that had been organised to provide an update on the Higgs investigation.
The boson was spotted in the wreckage resulting from proton particle collisions in the LHC’s giant accelerator ring.
Data gathered by two independent detectors observing this subatomic debris determined the mass of the Higgs to be about 126 gigaelectronvolts (GeV).
That was fascinating, said Prof Chris Hill of Ohio State University, because the number was right in the region where the instability problem became relevant.
"Before we knew, the Higgs could have been any mass over a very wide range. And what’s amazing to me is that out of all those possible masses from 114 to several hundred GeV, it’s landed at 126-ish where it’s right on the critical line, and now we have to measure it more precisely to find the fate of the Universe," he said.
Prof Hill himself is part of the CMS (Compact Muon Solenoid) Collaboration at the LHC. This is one of the Higgs-hunting detectors, the other being Atlas.
Scientists have still to review about a third of the collision data in their possession. But they will likely need much more information to close the uncertainties that remain in the measurement of the Higgs’ mass and its other properties.
Indeed, until they do so, they are reluctant to definitively crown the boson, preferring often to say just that they have found a “Higgs-like” particle.
Frustratingly, the LHChas now been shut downto allow for a major programme of repairs and upgrades.
"To be absolutely definitive, I think it’s going to take a few years after the LHC starts running again, which is in 2015," conceded Dr Howard Gordon, from the Brookhaven National Laboratory and an Atlas Collaboration member.
"The LHC will be down for two years to do certain repairs, fix the splices between the magnets, and to do maintenance and stuff. So, when we start running in 2015, we will be at a higher energy, which will mean we’ll get more data on the Higgs and other particles to open up a larger window of opportunity for discovery. But to dot all the I’s and cross all the T’s, it will take a few more years."
If the calculation on vacuum instability stands up, it will revive an old idea that the Big Bang Universe we observe today is just the latest version in a permanent cycle of events.
"I think that idea is getting more and more traction," said Dr Lykken.
"It’s much easier to explain a lot of things if what we see is a cycle. If I were to bet my own money on it, I’d bet the cyclic idea is right," he told BBC News.
Just wanted to let everybody know, some humans are trying to unlock the truths of the universe, in case other humans want to stop killing each other for childish reasons, grow up, learn to share the planet and get along.
Architects Fosters and Partners have revealed designs for a building on the Moon that could be constructed from material already on its surface.
An inflatable structure would be transported from Earth, then covered with a shell built by 3D printers.
The printers, operated by robots, would use soil from the Moon, known as regolith, to build the layered cover.
The proposed site for the building is the southern pole of the Moon.
It is designed to house four people and could be extended, the firm said.
In 2010 a team of researchers from Washington State University found that artificial regolith containing silicon, aluminium, calcium, iron and magnesium oxide could be used by 3D printers to create solid objects.
The latest plans are the result of a collaboration between a number of organisations including the European Space Agency.
The consortium tested the practicalities of using a printer on the Moon by setting up a D-shape 3D printer, which are used to print very large house-sized structures, in a vacuum chamber with simulated lunar material.
"As a practice, we are used to designing for extreme climates on Earth and exploiting the environmental benefits of using local, sustainable materials," said Xavier De Kestelier, a partner in the firm’s specialist modelling group.
"It has been a fascinating and unique design process, which has been driven by the possibilities inherent in the material."
Buildings on this planet by the architect firm include Wembley Stadium, the World Trade Center in New York and Beijing airport.
Last week US company Deep Space Industries (DSI) announced plans to use asteroid material for manufacture by harvesting them and using 3D printers sent into space.
The company is also developing a bespoke 3D printer called MicroGravity Foundry for the purpose, it said, and hopes to be ready to start production by 2020.
Researchers have proposed a new means for getting a measure of just how massive supermassive black holes are.
They are known to exist at the centres of most galaxies, but a puzzle remains as to how they affect galaxy evolution.
The approach, published in Nature, infers a black hole’s mass from the speed of molecules swirling around it.
It could help weigh hundreds of nearby black holes. Its first use suggests a black hole in the NGC4526 galaxy has a mass 450 million times that of our Sun.
Only in a few dozen cases have the masses of supermassive black holes been estimated. Because they cannot be seen directly, astronomers have relied on guessing how large they are based on the motion of objects circling them.
Most estimates have come from gathering up starlight. This can be done by calculating how much faster the stars nearer the black hole are moving relative to those farther away.
However, that is an average measure, and the “random motions” of stars - not necessarily in the same direction as the swirling mass - blurs the measurement.
The movement of electrically charged gas can be tracked in the same way, with slightly less blurring due to random motion.
But these approaches remain painstaking and limited to only the nearest galaxies’ black holes.
The new work focuses instead on cold, dense masses of gas that have markedly less random motion, and which emit their radiation in the microwave part of the electromagnetic spectrum. That allows the use of telescopes and arrays with far better resolution.
Timothy Davis of the European Southern Observatory and colleagues made use of the Carma array of telescopes in California, US, looking specifically for the radiation coming from molecules of carbon monoxide.
They focused their efforts on NGC4526, mapping out the movements of the molecules at various distances from the galaxy’s central black hole.
Using their new technique, they estimated the black hole has a mass of some 900 billion trillion trillion tonnes - on the heavy side even in the supermassive stakes.
Estimates such as this may help finally unravel the interplay between black holes and the galaxies that host them.
"Galaxies and black holes seem to be related to each other; there’s this relation between the mass of the black hole and properties of the galaxy," explained Dr Davis.
"That’s rather weird, because these black holes are tiny compared to galaxies; they don’t weigh that much, and they’re physically small - less than the size of our Solar System in a galaxy that’s billions of times bigger," he told BBC News.
"What we’d really like to understand is how these two components interact; why they care about each other at all. To do that, we need to be able to measure their masses, and compare them in all sorts of different galaxies. That will allow us to start answering these questions."
With the new method in hand, Dr Davis said that next-generation telescopes tuned to these microwave frequencies - such as the Alma telescope in Chile - would be able to easily acquire the masses of hundreds of black holes.
"The observations we present in the paper took over 100 hours on the Carma telescope," he said. "We estimate that with Alma you’ll be able to reproduce those observation in 10 minutes. It’s a real game-changer."