# Tag Info

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It could have been beautiful, and indeed it would have been the case if the Universe consisted of "normal" matter — i.e. baryons and dark matter – above a certain critical density threshold (which you can calculate to $\sim10^{-29}$g/cm$^3$). Unfortunately, as it was realized in 1998, a mysterious "energy" labeled dark energy seems to permeate empty space, ...

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The rotational energy of a body is given by: $$E = \tfrac{1}{2}I\omega^2$$ where $I$ is the moment of inertia and $\omega$ is the angular velocity. For a uniform sphere the moment of inertia is related to the mass of the sphere, $m$, and the radius of the sphere, $r$, by: $$I = \frac{2}{5}mr^2$$ You already have the mass, and you can Google for the ...

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In standard model, the mass of a particle can be explain by either Dirac or Weyl equation. The first thing is that neutrinos are can't be described by any of the above equations (Dirac equation or Weyl equation) in the standard model because no right handed neutrinos are observed. Dirac equation needs four spinors to explain the mass of any particle. But in ...

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In theory, a massive particle can be accelerated asymptotically close to the speed of light. But one can never actually reach the speed of light because the kinetic energy of such a (massive) particle would be infinite. This is because the mass of the particle itself become heavier at higher speeds due to relativistic effects. Specifically: $$\text{Kinetic ... 1 Well, by massive, I assume you mean objects that have non-zero rest mass. In that case, it would take infinite energy for that object to reach the speed of light. However, their speed would get closer and closer to the speed of light as more energy is put in, until their speed was practically (but not exactly) the speed of light. Additionally, the smaller ... 1 No, that's not possible. Even if the two bodies could be compressed to be just larger than their Schwarzschild radius (they can't really, without collapsing further to black holes), their combined Schwarzschild radius, which grows linearly with mass, is twice their individual Schwarzschild radii. That means that even if they effectively rolled on each other ... 3 Far away from a black hole, spacetime is curved only a little bit, and many different things could curve it like that out there. It's like if you had a dollar in your pocket, and it's been there for a long time, and you can't remember if you got it from your boss or from your friend. But a dollar is a dollar. So you could have a massive star, or a black ... 11 Although we don't have a quantum theory of gravity, we think we have some reliable knowledge about the properties of black holes from general relativity. One thing we think we know is the so-called "No-hair conjecture", which says that black holes can be described by just three numbers: mass, charge, and angular momentum (i.e. how much they are spinning). ... 0 The singularity probably does not exist, as GR likely breaks down at those size / energy scales. When we have a full quantum description of gravity we may know what's really there. By the way, the part of the black hole we fully understand is actually the vacuum solution - the Schwarzschild metric - which includes the event horizon but not the source mass. ... 0 It's almost certainly incorrect that the center of a black hole is a singularity as this would be at odds with quantum mechanics. Just how exactly it looks like would be something to ask of a theory of quantum gravity! Regardless of being a singularity or not, the mass is determined by how much mass you stuff into your black hole. Hence black holes of ... 0 The density of black holes isn't infinite. Some black holes have the billionfold density of our sun (like the black holes in center of galaxies). There are big and small black holes. 1 Unfortunately, no, your calculation does not seem to be correct. Your calculation is based on Einsteins famous equation E=mc^2; however, this equation is actually only valid for objects at rest, while all experiments confirm that photons in a vacuum move with a constant speed of 2.99...\times10^8~m/s. The equation Einstein gave for moving particles is ... 0 As stated in the other answers (and your own question), mass and weight (downward force due to gravity) are two distinctly different units, but related via acceleration. So, in the presence of a gravity field such as we experience on the surface of the Earth, it can be convenient and more-or-less reliable to measure the weight of a thing to determine its ... 1 Actually when we measure our weight in a weighing machine, it is a big confusion that it is our mass or weight, because it measures in kg, which is unit of mass. But weighing machine measures our weight and its unit is in kgf (kilogram force) not kg, its a metric unit of weight, and as we know that N (Newton) is a SI unit of weight and 1Kgf = 9.807N So as ... 1 If you calculate the ratio between the proton mass and its constituent quarks, you'll see that the quarks actually account for only 1.0% of the proton mass. A similar calculation for a neutron shows that quark masses account for 1.3% of the neutron mass. Thus for both of these particles, 99% of the mass is not simply the sum of masses of the subatomic ... 1 Both protons and neutrons are made up of two types of quarks: up (u) and down (d). Protons are uud and neutrons udd. QCD, the strong force binds these quarks together into protons and neutrons (technically, the binding involves a "sea" of gluons and quark-antiquark pairs). There is an approximate symmetry of QCD called isospin. Both the u and d quarks are ... 0 The acceleration of any object due to gravity is g = 9.8m/s and this constant does not depend on the mass of the object (or the speed of the object or anything else for that matter, as long as you're on/near earth). Pushing an object away from the earth is another story. While the acceleration of objects towards earth does not depend on their masses, their ... 4 When you are lifting an object, you are exerting a force that balances the force of gravity on the object. By$$ F = m g$$where g is the acceleration due to gravity, you see that a greater mass causes a greater gravitational force that has to be balanced by the force you apply to the object by holding it or lifting it at a constant velocity. Using the more ... 1 I'm not exactly sure what you are asking. If you're wondering about how we know that bodies of different masses fall at the same rate if we ignore other factors like air resistance, then you might want to take a look at experiments like these. If you are interested in how we arrive at the conclusion that the acceleration is equal to gravity, we can ... 0 Based on the simple definition of the Heisenberg uncertainty principal, uncertainty is an inverse ratio between location and velocity, so if you're willing to know very little about location, then you can measure velocity with accuracy. Now, on the quantum level, particles can do strange things like borrow energy from the future so, there's probably a small ... 1 Uncertainty is a property of observables. Mass is not normally taken to be an observable, so it does not obey uncertainty relations. Why isn't mass an observable? There is a superselection rule that forbids it in the presence of reasonable symmetry assumptions. See the discussion here for more. 1 c is not only an invariant speed, c is also a physical constant that factors in many well known formula, e.g., the electromagnetic fine structure constant$$\alpha = \frac{e^2}{4 \pi \epsilon_0 \hbar c}$$In the case of the famous$$E = mc^2 the particle with mass $m$ has zero speed (in this frame of reference). If the particle has a speed $v$ in ...

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$E=mc^2$ is actually not the full equation, although it is clearly the most famous form of it. The full equation is $E^2 = p^2c^2 + m^2c^4.$ This formula says that a particle's energy squared is equal to the sum of the momentum squared and the mass squared (with factors of the speed of light thrown in to make it dimensionally correct). The simple ...

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To push something over, you apply a torque. If the thing you are pushing can provide an equal and opposite counter torque without moving, then it won't move. In your example, torque can be due to one of two things: Gravitational: a heavy object with its center of mass displaced relative to its rear support point needs torque to push over because as it ...

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Mass universe is constituted of micro / macro mass natural bodies/systems. It is known that the mass (micro / macro) natural bodies is concentrated mainly in neutrons, protons and electrons as entities with a certain stability, fig. 3. Fig. 3. (Electro)convergence of the electron/neutron /proton, )[4] 1- Neutron matrix (local substantial body/ local wave ...

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No. Is the temperature constant? We need to know if the spring has any electric or magnetic properties. Is someone touching it and compressing it? Are you doing the experiment on a horizontal table? If vertically, on Earth or Jupiter? Is the mass large enough that it would take the spring out of its Hooke regime? Are you on free fall?

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Graphene is already commercially used in printable, conducting inks (see e.g. here). This application works with small graphene flakes in a liquid solution. For most electronic applications, high-quality, large-area graphene placed on an insulating substrate is needed. The most promising method (in my opinion) for this end is chemical vapor deposition (CVD) ...

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Temperature is a quantity that determines how heat flows into and out of a system of particles when it is placed in contact with other systems. By this definition, measuring the temperature of a system with no mass inside is nonsensical; it's not absolute zero, it's undefined. Temperature can equivalently be defined as being proportional to the average ...

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A cubic metre void of anything cannot be described with a temperature. Spacetime itself does not have the property of temperature, so it would be incorrect to say such a void is at absolute zero. However, it is not necessary that any volume not at absolute zero has mass. The property of temperature could be held by photons or other massless particles. For ...

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As mentioned in the comment above, temperature is defined to be a measure of the average kinetic energy of the particles in a system. So with that definition, the answers to your questions should fall out naturally: If there is no mass in a volume, you could say the temperature is absolute zero. I would say it isn't defined because you cannot take the ...

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Consider this: the space traveler is flying at near light speed relative to you. But for him you are flying at near light speed, just in opposite direction. So he must think then that you have to experience all the "effects of the increased mass", mustn't he? The answer is in the fact that the very basis of Special Relativity is the postulate of ...

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