One of the questions I get most often from my readers is this: Since gravity pulls on things proportional to their mass, and since the Higgs field is responsible for giving everything its mass, there obviously must be a deep connection between the Higgs and gravity… right? It’s a very reasonable guess, but — it turns out to be completely wrong. The problem is that this statement combines a 17th century notion of gravity, long ago revised, with an overly simplified version of a late-20th century notion of where masses of various particles comes from. I’ve finally produced the Higgs FAQ version 2.0, intended for non-experts with little background in the subject, and as part of that, I’ve answered this question. But since the question is so common, I thought I’d also put the answer in a post of its own. As preface, let me bring out my professorial training and correct the question above with a red pen: Since gravity pulls on things proportional to their mass to a combination of their energy and momentum, and since the Higgs field is responsible of giving everything not everything, just the known elementary particles excepting the Higgs particle itself its mass, there obviously must be a deep connection between the Higgs and gravity… right? wrong. Now let me explain these corrections one by one. When you first learn about gravity in school, you learn Newton’s law: that the force of gravity between two objects, one of mass M1 and one of mass M2, has a strength proportional to the product M1 M2. But that was true before Einstein. It turns out that Newton’s law needs to be revised: the Einsteinian statement of the law is (roughly) that for two objects that are slow-moving (i.e. their speed relative to one another is much less than c, the speed of light) and have energy E1 and E2, the gravitational force between them has a strength proportional to the product E1 E2. How are these two statements, the Newtonian and the Einsteinian, consistent? They are consistent because Einstein and his followers established that for any ordinary object, the relation between its energy E, momentum p and mass M [sometimes called “rest mass”, but just called `mass’ by particle physicists] is For a slow-moving object, p ≈ Mv (where v is the object’s velocity) and pc ≈ Mvc is much smaller than Mc2. And therefore

]]>The three constants you give illustrate the arbitrariness of units. The magnetic constant $$K_m = 10^{-7} {N\over A^2}$$ serves to define the Ampere. The definiton of the Ampere implied by this (defined) constant is that the force between two long wires carrying one Ampere of current at a separation of 1 meter is 10^{-7} Newtons per unit length. If you change this constant, you redefine the Ampere. the other constant you mention is $$ K_e = 8.996 \times 10^9 {Nm^2\over C^2}$$ This is interesting, because if you just look at the number, forgetting the power of 10, it's the square of the speed of light. The reason for this is that electric and magnetic effects are related by relativity, and the ratio of $K_e$ and $K_m$ is the speed of light squared. Because we choose units where $K_m$ is a power of 10, the $K_e$ is then the same as the square of the speed of light. Since the speed of light, like $K_m$, is defined, thereby setting the standard definition of the meter, the electric constant $K_e$ is also defined- it is $10^{-7}$ times the exact speed of light squared. If you vary it, you can only do so in conjunction with varying the definition of the speed of light, and therefore the meter. The gravitational constant, in an ideal world, would define the unit of mass. But gravity is too weak to measure accurately enough, so we use a block of metal in a vault in Paris for now to define what a "Kilogram" is. This will probably change at some point. But "G" is also a constant that is philosophically incapable of varying, since it defines the system of units. If you want to ask a sensible question, you should ask them of quantities that don't depend on the units. In practice, you ignore $G, \hbar, c, k_b, K_m$ (your stuff, swapping out $K_e$ for c, plus Planck's constant and Boltzmann's constant). These you set to 1 in a reasonable system of units, and then all other quantities become dimensionless and meaningful, so you can ask about why they have the values that they do.

]]>Stephen Hawking bet Gordon Kane $100 that physicists would not discover the Higgs boson. After losing that bet when physicists detected the particle in 2012, Hawking lamented the discovery, saying it made physics less interesting. Now, in the preface to a new collection of essays and lectures called "Starmus, " the famous theoretical physicist is warning that the particle could one day be responsible for the destruction of the known universe. Hawking is not the only scientist who thinks so. The theory of a Higgs boson doomsday, where a quantum fluctuation creates a vacuum "bubble" that expands through space and wipes out the universe, has been around for a while. However, scientists don't think it could happen anytime soon. "Most likely it will take 10 to the 100 years [a 1 followed by 100 zeroes] for this to happen, so probably you shouldn't sell your house and you should continue to pay your taxes, " Fermilab theoretical physicist Joseph Lykken said during a Sept. 2 lecture at the SETI Institute. "On the other hand, it may already have happened, and the bubble might be on its way here now. And you won't know because it's going at the speed of light, so there's not going to be any warning." [Doomsday: 9 Real Ways Earth Could End] The Higgs boson is sometimes referred to as the "God Particle, " much to the chagrin of scientists who prefer the official name. Its discovery lends strong support to the Standard Model of particle physics, which is thought to govern the basic building blocks of matter. The Higgs boson particle is important to the Standard Model because it signals the existence of the Higgs field, an invisible energy field present throughout the universe that imbues other particles with mass. Since its discovery two years ago, the particle has been making waves in the physics community. Now that scientists have measured the particle's mass, they can make many other calculations, including one that seems to point to the end of the universe. Doomsday calculations The Higgs field emerged at the birth of the universe and has acted as its own source of energy since then, Lykken said. Physicists believe the Higgs field may be slowly changing as it tries to find an optimal balance of field strength and the energy required to maintain that strength. [5 Implications of Finding a Higgs Boson Particle] "Just like matter can exist as liquid or solid, so the Higgs field, the substance that fills all space-time, could exist in two states, " Gian Giudice, a theoretical physicist at the CERN particle physics center where the Higgs boson was discovered, explained during a TED talk in October 2013. Right now the Higgs field is in a minimum potential energy state — like a valley in a field of hills and valleys. The huge amount of energy required to change into another state is like chugging up a hill. If the Higgs field makes it over that energy hill, some physicists think the destruction of the universe is waiting on the other side. But an unlucky quantum fluctuation, or a change in energy, could trigger a process called "quantum tunneling." Instead of having to climb the energy hill, quantum tunneling would make it possible for the Higgs field to "tunnel" through the hill into the next, even lower-energy valley. This quantum fluctuation could happen somewhere out in the empty vacuum of space between galaxies and create an expanding "bubble, " Lykken said.

]]>Plancks New Recipe of the Universe: More Matter, Less Dark Energy

]]>File:NewtonsLawOfUniversalGravitation.svg - Wikimedia Commons

]]>2]/2[pi]c) is the reduced sub-Planckian "action" constant, G is the Newtonian gravitational constant, and c is the velocity of light.j] is a random number in the interval [0, 1], G(t) is the gravitational constant at time t, [M.81 (m/(s^2)) Gravitational constant -32 (ft/(s^2)) Gravitational constant [PI]/(dh)=(MRT)/(dh) Gravitational constant w/m Gravitational constant H E+PV Enthalpy E/v Planck's constant E/f Planck's constant (E[lambda])/c Planck's constant =wavelength; c=speed of light] mv[lambda] Planck's constant =wavelength] [lambda][rho] Planck's constant [[lambda]=wavelength; [rho]=momentum] 6.b] is the bulk density of the powder, and g is equal to the gravitational constant.Gravitational constant G is considered as a linear decreasing functionThe underlying measurements for the mass and density of the planets are based on a single assumption that the equation for gravity is correct and the gravitational constant is universal.The point at which a stellar object can no longer escape being swallowed by a black hole is known as the Schwarzschild radius, a quantity whose value depends on the black hole's mass, the speed of light and the gravitational constant.c], [gamma], T, and p denote the gravitational potential, gravitational constant, thermal conductivity, gas constant, velocity of light, density of ionized component, density of neutral components ([rho] > [[rho].The Planck length is derived from Newton's gravitational constant, the speed of light and Planck's own constant from quantum theory.where v is the angular speed of a test particle about a body of mass M, G is the gravitational constant and r is the distance between the test particle and the massive body, a is a coefficient of the order of unity that depends on the exact definitions of v and r, as well as the geometry of the system.where r is the scalar curvature at any point of the space time and K is the gravitational constant [6].In the Einstein's field equations the Gravitational constant G has been introduced via the Newtonian approximation of the Einstein field equation.

]]>Physicists have reasons to look for alternatives to WIMPs. For two decades, astronomers have found less dark matter at the centers of galaxies than what WIMP models suggest they should. The discrepancy is even worse at the cores of the universe’s tiny dwarf galaxies, which have few ordinary stars but lots of dark matter. About four years ago, James Bullock, a professor of physics and astronomy at the University of California, Irvine, began to wonder whether the standard view of dark matter was failing important empirical tests. “This was the point where I really started thinking hard about alternatives, ” he said. Bullock thinks that dark matter might instead be complex, something that interacts with itself strongly in the way that ordinary matter interacts with itself to form intricate structures like atoms and atomic elements. Such a self-interacting dark matter, Bullock suspects, could exist in a “dark sector, ” somewhat parallel to our own light sector, but detectable only through the way it affects gravity. He and his colleagues have created numerical simulations that predict what the universe would look like if dark matter feels strong interactions. They expected to see the model fail. Instead, they found that it was consistent with what astronomers observe. Quanta Magazine spoke with Bullock about complex dark matter, how this mysterious mass might behave, and the best places in the universe to find it. An edited and condensed version of the interview follows. QUANTA MAGAZINE: What do we know about dark matter? JAMES BULLOCK: We are confident that it’s there, that it has mass, and that it tugs on itself and on other things via gravity. That’s about it. While dark matter has a gravitational tug, it doesn’t interact with normal matter—the stuff that makes up you and me—in a very intense way. It doesn’t shine. It’s invisible. It’s transparent. It doesn’t glow when it gets hot. Unfortunately, those are the ways astronomers usually study the universe; we usually follow the light. So we don’t know what it’s made of? We’ve come to understand that we can describe the world that we experience by the Standard Model of particle physics. We think of the particles that make up you and me as being broken down into constituent things, like quarks, and those quarks combine into neutrons and protons. There is a complicated dance that allows these particles to interact in certain ways. It gives rise to the periodic table of elements and all of the vast complexity we see around us. Just 20 percent of the mass of the universe is all of this complexity. On the other hand, dark matter makes up something like 80 percent of the mass. First-guess models for what it is suggests that it is one particle that doesn’t really interact with much of anything—WIMPs. These are collisionless, meaning when two dark matter particles come at each other they basically go through each other. Another possibility is this 80 percent of the universe is also complex. Maybe there’s something interesting going on in what’s called the dark sector. We know that whatever ties us to the dark matter is pretty weak or else we would have already seen it. This observation has led to the belief that all the interactions that could be going on with dark matter are weak. But there’s another possibility: When dark matter particles see themselves, there are complex and potentially very strong interactions. There even could be dark atoms and dark photons. Those two worlds—this dark sector and our own sector—only communicate by gravity and perhaps other weak processes, which haven’t yet been seen. How can you probe this dark sector if you can’t interact with it? Now what we’re talking about doing is not just looking at the gross properties of the dark matter but the very makeup of the dark matter, too. The most obvious place to see those effects is where dark matter is bunched up. We believe the centers of galaxies and galaxy clusters are densest. And so by studying the behavior of dark matter by indirect methods—basically by the dynamics of stars and gas and galaxies in galaxy clusters—we can start to understand how dark matter is distributed in space. To start to discriminate between models, we can compare differences in dark matter’s spatial clumpiness in simulations, for example, and then look for those differences in data. What does the data say? In models using cold, collisionless dark matter—WIMPs—the dark matter is very dense at the middle of galaxies. It appears that those predicted densities are much higher than what’s observed. What might be going on is that something a little more complex is happening in the dark sector, and that complexity is causing these slight disagreements between theory and observation at places where the dark matter is really clumped or starts congregating, like in the centers of galaxies or the centers of galaxy clusters. I’m interested in running cosmological simulations of how the universe should evolve from the very beginning until now. I look at what happens, when I run those simulations forward, if I allow cold dark matter to occasionally collide and exchange energy. The simulations start with a small, almost-smooth primordial universe and end with beautiful agreement with large-scale structure—galaxies stretched out across the universe in the way we observe them. But the hearts of galaxies are less dense in dark matter in my simulations than they are in simulations where the dark matter is cold and collisionless. How long have researchers known about these disagreements between the models and the data?

]]>This lesson defines what a gravitational field is and some practical examples encountered in the real world. We also develop the equations governing the gravitational field and explain what the units of measurement mean. Click "next lesson" whenever you finish a lesson and quiz. Got It You now have full access to our lessons and courses. Watch the lesson now or keep exploring. Got It You're 25% of the way through this course! Keep going at this rate, and you'll be done before you know it. Way to go! If you watch at least 30 minutes of lessons each day you'll master your goals before you know it. Go to Next Lesson Take Quiz Congratulations on earning a badge for watching 10 videos but you've only scratched the surface. Keep it up! Go to Next Lesson Take Quiz You've just earned a badge for watching 50 different lessons. Keep it up, you're making great progress! Go to Next Lesson Take Quiz You have earned a badge for watching 20 minutes of lessons. You have earned a badge for watching 50 minutes of lessons. You have earned a badge for watching 100 minutes of lessons. You have earned a badge for watching 250 minutes of lessons. You have earned a badge for watching 500 minutes of lessons.

]]>A shadow cosmos, woven silently into our own, may have its own rich inner life On September 23, 1846, Johann Gottfried Galle, Director of the Berlin Observatory, received a letter that would change the course of astronomical history. It came from a Frenchman, Urbain Le Verrier, who had been studying the motion of Uranus and concluded that its path could not be explained by the known gravitational forces acting on it. Le Verrier suggested the existence of a hitherto unobserved object whose gravitational pull was perturbing Uranus's orbit in precisely the way required to account for the anomalous observations. Following Le Verrier's directions, Galle went to his telescope that night and discovered the planet Neptune. Purchase to read more You've read the preview. Already purchased? Sign in to access the full article. From this issue SA Special Editions Every Issue. Every Year. 1845 - Present Neuroscience. Evolution. Health. Chemistry. Physics. Technology. Subscribe Now!

]]>Top Question: Define force of gravitation. Answer: The force of attraction which exists between any two objects in the universe is known as force of gravitation. Question: State Newton's law of gravitation. Answer: According to this law, "Every particle in this universe attracts every other particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them". Question: Why is G called a universal constant? Answer: G is known as universal constant, because its value remains the same throughout the universe. Question: List out the physical quantities on which the gravitational force between objects depends. Answer: The gravitational force between two objects depends on a) the mass and b) the distance between them Question: What do you mean by a freely falling object? Answer: An object which moves towards the earth due to force of gravity is described as a freely falling object. Question: What is acceleration due to gravity? Answer: The acceleration produced in a body due to force of gravity is known as acceleration due to gravity. Question: Two bodies of mass 10 kg and 12 kg are falling freely. What is the acceleration produced in the bodies due to force of gravity? Answer: The acceleration due to gravity produced in both the bodies is the same as it is independent of the mass of the body. Acceleration produced in both the bodies 10 kg and 12 kg is 9.8 m/s2. Question: What will happen to the force of gravitation between two objects A and B if the distance between them is reduced to half? Answer: Let d be the distance between the two objects A and B of mass m1 and m2 respectively, The force between A and B when distance between them is reduced to half F1 = 4 F i.e., the force increases. The force of gravitation between any two objects increases by a factor 4 if the distance between the objects is reduced to half. Question: What would you observe if there are two massive bodies A and B of equal masses which experience only force of gravitation? Answer: The objects A and B would be moving around each other.

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