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Questions tagged [mass-energy]

The special-relativistic relation connecting energy with mass, $ E^2 - (m c^2)^2= (pc)^2 $. May be used to provide accounting constraints in energy and momentum, both conserved in total, even in reactions where $m$ is not.

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Can a big mass defect make the mass negative?

Can two particles with small masses and a strong attractive interaction have a total negative mass when brought together? Let $m_1, m_2$ be the (rest) masses of two particles when infinitely distant. ...
HomoVafer's user avatar
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2 votes
5 answers
451 views

Is a photon truly massless? [duplicate]

First of all, I am not a physicist or mathematician, not even a hobbyist but the following statements have always puzzled me: $E=mc^2$ A photon is a desecrated particle of energy. A photon is ...
AUser's user avatar
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If a proton transforms into a neutron by releasing a positron why should this process create more mass? [duplicate]

If waves can interfere and thats why cancel out or add up why we cannot think the same about the natterial feature called mass as in this explained example in the title of this posted question??Thanks ...
Emilija Bradvica's user avatar
2 votes
1 answer
95 views

Why is the mass-energy graph for atomic mass $A=98$ not quadratic?

For fixed atomic mass $A$ and varying atomic number $Z,$ the mass of the nucleus is quadratic in $Z$. Were it possible for $Z$ to vary continuously, we'd have at most one local minimum. Since we are ...
Display name's user avatar
-1 votes
1 answer
116 views

Why the Sun has a higher temperature than humans?

Why the Sun has a higher temperature than humans if the energy/gramme of matter ratio of humans is greater than that of the Sun?
Aarnihauta's user avatar
1 vote
1 answer
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"Mass Shell" Condition on Euclidean Scalar Field

This is a basic qft question. I am looking for the condition on a free scalar $\phi$ of mass $m$ in Euclidean space such that it satisfies the Klein-Gordon equation. The Euclidean space Klein-Gordon ...
Sam's user avatar
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6 votes
2 answers
291 views

Does life erode Earth's mass over time?

Since life converts matter to energy, and there's no natural process that does the opposite (aside from supernovas), does this mean that the mass of our planet is gradually diminishing? I asked ...
Lynx's user avatar
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1 vote
1 answer
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Why does the mass-energy equivalence apply to binding energy when it is derived purely through kinematic means?

I understand that by defining the four velocity, multiplying it by the rest mass and taking the entire thing's norm we get $E^2=m^2+p^2$, but how does this apply to binding energy, or in general ...
Y G's user avatar
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0 votes
1 answer
85 views

Is the Planck mass the "lower limit" for gravity?

The Planck units are often treated as being the "lower limits" to things: the Planck length for length, the Planck time for time, etc. But the Planck mass, which is about $2.2\times10^{-5}$ ...
Quantum Wonder's user avatar
0 votes
0 answers
19 views

How does mass-energy equivalence work with chemical bonds? [duplicate]

If you have, for instance, 2 oxygen atoms and do E=mc2 to get their equivalent energy, you get about 2.38nJ. However, if you have diatomic oxygen, there's also the energy of the bond; about 0.8aJ. ...
Flamethrower's user avatar
0 votes
1 answer
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What is the total mass-energy of baryonic matter?

From what I understand, conservation of energy does not apply to the total energy of the Universe, because it constantly expands and the new, created space has a constant non-zero energy of its own. ...
Quantum Wonder's user avatar
-1 votes
2 answers
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Rest Mass Energy

What exactly is the Rest mass energy? I know the usual goes Like it is total energy stored in mass $m$ that is in Rest. so for someone moving relative to the frame that the mass $m$ is in (a rest ...
Hello's user avatar
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1 vote
1 answer
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Does dark matter have mass?

When trying to understand what dark matter is, it is helpful to know that some properties of it can already be derived from various observations, such as, it only interacting via gravity and no other ...
Quantum Wonder's user avatar
-1 votes
3 answers
106 views

Suppose a shell of a sphere formed by matter and with large radius, start afterwards to diminish the radius, give $E=mc^2$ the system stops

Thinking in classical mechanics terms but with the knowledge that $E=mc^2$ let's make the below thought: Suppose you have a shell of a sphere formed by a mass uniformly distributed over the surface of ...
George Kourtis's user avatar
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Is the relativistic energy-momentum relation fundamental? [duplicate]

The following relativistic energy-momentum relationship is taken to be fundamental: $$E^2=p^2c^2+m_0^2c^4.\tag{1}$$ Let us specialize to massless particles ($m_0=0$) so that we have: $$E=p\ c.\tag{2}$$...
John Eastmond's user avatar
-6 votes
1 answer
163 views

If a 100,000 ton container ship slams into a bridge at 8.6 knots how much energy was moved into the pylon and at what rate of transfer speed? [closed]

Edit: the entire question is in the title, the answer should be an amount of energy and a value of energy transfer in some unit, but not knowing enough about physics I don’t know what the appropriate ...
MetaGuru's user avatar
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0 answers
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If I burn a log & contain all the matter, will the burned log weigh $E/c^2$ less than the unburned log, with $E$ being the energy from light & heat? [duplicate]

I understand that the change in weight would be tiny even to a physicist and nothing for any practical purpose. I am also not talking about smoke and water vapor. I am only referring to energy given ...
John Bonner's user avatar
0 votes
1 answer
69 views

Why does the total gravitational potential in the universe exactly equal the total mass energy RIGHT NOW? [duplicate]

In the zero energy universe model, the gravitational field has negative energy, and this negative gravitational energy of all the distant mass exactly balances and cancels the positive mass-energy in ...
Miss Understands's user avatar
0 votes
2 answers
61 views

How mass change can be converted to energy? [closed]

Some gas with initial mass $m_{1}$ was put in a container under high pressure and temperature. After some time its mass became a bit smaller ($m_2$). Additionally, some energy was released and it was ...
renathy's user avatar
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0 answers
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How can a proton be stable if binding energy *increases* it's mass? [duplicate]

A hydrogen atom weighs 13.6eV less than a proton + electron. This missing energy, which is tiny compared to the rest mass of almost a GeV, was carried off by a photon when the atom formed. Nuclei show ...
Kevin Kostlan's user avatar
0 votes
1 answer
90 views

$Q$-value (nuclear)

I'm studying principles of physics. I have a question. In my book, they seem to have calculated the Q value in different ways. $$ \begin{align} \rm p + {^{27}_{13}Al} &\rightarrow \rm{^{27}_{14}Si}...
SungJin Park's user avatar
1 vote
2 answers
198 views

Equation for relative Kinetic energy

Relative Kinetic energy is given by K.E = ($\gamma$-1)$m_0$c²; where $m_0$ is rest mass but can it also be given by this K.E= $\frac{1}{2}\gamma m_0v²$; where v is velocity of particle can it?
SHINU_MADE's user avatar
1 vote
0 answers
55 views

Norm for the energy-momentum vector: what meaning/use does it have from the point of view of the energy-momentum tensor?

Many books on relativity define "mass" $M$ as the norm of the energy-momentum vector $\pmb{P} := (E, \pmb{p})$, that is, $M = \sqrt{\lvert \pmb{P}\cdot\pmb{g}\cdot\pmb{P}\rvert}$, where $\...
pglpm's user avatar
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4 votes
3 answers
603 views

Are energy-momentum relation equations still valid with speed of light?

I'm confused about the theory regarding the energy- momentum relation when I consider the speed of an object being $v = c$. Using for example the relations $$E^2 = (pc)^2 + (m_0c^2)^2$$ $$E = \gamma_{...
Axel Togawa's user avatar
0 votes
0 answers
84 views

What is the causation of the mass deficit in atomic nuclei?

I've always heard that when protons and neutrons are combined together into nuclei, the mass of the product is less than the mass of the constituents. And that this mass is called the mass deficit and ...
Wander verse's user avatar
2 votes
8 answers
306 views

If matter is a form of energy, can it be converted into another form of energy?

I have been told that energy and mass are the same. What puzzles me is why don't we use the same units of measure for both if they are the same? The unit of mass is kg and the unit of energy is the ...
Gerry's user avatar
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-1 votes
1 answer
48 views

Mass self-annihilates to violate law of conservation of energy? [closed]

The scenario is this: a large mass $ M $ is made of matter and anti-matter in equal amounts. If given a little energy, it will self-annihilate. Another mass $ m $ is in vicinity. The potential energy ...
Adeel Malik's user avatar
1 vote
1 answer
83 views

Why do ( within my limited understanding.) Energy and matter act in opposite ways [closed]

I would like to preface this by stating this type of research is my hobby not my profession. If I understand the basic explanation correctly, energy tends to spread out evenly within a closed system ...
TylerTheSparky's user avatar
4 votes
3 answers
209 views

Is there a unified conceptual definition of mass?

Last night I posted this question: Since light has inertia and experiences gravity, what does it mean for photons to be massless?, which I now think was overly wordy and didn't properly express what I ...
Mikayla Eckel Cifrese's user avatar
2 votes
1 answer
161 views

How to find rest mass?

I have two identical massess with rest mass $m_0$. One of them is made to move with very high velocity $v$, while other is at rest. At some point in time the moving mass collides with the stationary ...
SHINU_MADE's user avatar
1 vote
4 answers
201 views

Since light has inertia and experiences gravity, what does it mean for photons to be massless?

I've been trying for a long time to figure out what the heck mass even IS. In introductory physics and chemistry, students are told that massive objects are those that are made of matter and take up ...
Mikayla Eckel Cifrese's user avatar
1 vote
2 answers
229 views

In special relativity, is mass considered as $\gamma m$ or is only the momentum considered as $\gamma mv$?

I am trying to solve the equation of motion of free-falling object considering relativistic effects. I am not sure the force on the object is whether $\gamma mg$ or just $mg$ where $m$ is the rest ...
Zjjorsia's user avatar
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6 votes
2 answers
1k views

Why it is the mass instead of the mass distribution used in Schwarzschild metric?

Schwarzschild metric is given by (Carroll, chapter 5) $$ ds^2=-\left(1-\frac{2GM}{r}\right)\mathrm{d}t^2+\left(1-\frac{2GM}{r}\right)^{-1}\mathrm{d}r^2+r^2d\Omega^2 $$ where $M$ is the total mass of a ...
Photon's user avatar
  • 139
0 votes
1 answer
46 views

Eigenvalue in the Energy Derivation from Klein-Gordon Equation

I was watching this video tutorial for the derivation of Energy (chapter 3) from the Klein-Gordon equation where they had taken the two equations of $$(P^\mu P_\mu-m^2)\psi=0$$ and $$(-(K^0)^2+\...
Harshdeep Chhabra's user avatar
0 votes
1 answer
41 views

On Potential Difference

We say that The work done on a coulomb of charge by the electric force from the terminals to move it from one point to another is called Voltage.Then my q is if I increase the length of the wire ...
Pratyush Pandey's user avatar
0 votes
0 answers
47 views

Neutrinos becoming mass eigenstates in the early universe

I have two points where I would need clarification: Neutrinos are present in the early universe as flavor eigenstates and as such they decouple from the thermal bath, I guess. However, today, at ...
user268009's user avatar
0 votes
0 answers
36 views

Gravity Violation of conservation of energy? [duplicate]

If a satellite gains gravitational energy when shot into space but all matter becomes light, what happens to its potential gravitational energy? When matter turns into light, it loses mass, affecting ...
Daniel Blomqvist's user avatar
0 votes
0 answers
32 views

What is the real meaning of energy released in nuclear fission? [duplicate]

In a nuclear fission reaction the total energy and thus the mass of the products are lower than the total energy of the reactants. I understand the the difference in this energy can be used in a ...
Alex's user avatar
  • 79
2 votes
1 answer
237 views

"Pure Energy" in special relativity and why does the rest energy follow from a derivation at the speed of light?

I'm currently studying special relativity by reading through the lecture notes of M. Fowler from the University of Virginia. The famous equation $E=mc^2$ is derived by analyzing the work done by a ...
Mika R.'s user avatar
  • 39
2 votes
1 answer
219 views

Stress-energy-momentum tensor and potential energy

The stress-energy-momentum tensor in General Relativity includes a mass density terms, which is related to energy via $E=mc^2$. How does potential energy figure into this, since potential energy is ...
Stephen Montgomery-Smith's user avatar
6 votes
2 answers
2k views

During fusion, how does mass turn into energy?

This is my (flawed) understanding of how fusion basically works: Let's assume that a fusion reaction has a net gain in energy. First, there is an input amount of kinetic energy to get the two light ...
Edward Chen's user avatar
6 votes
3 answers
781 views

Is the mass of Satellite + Earth system less than their individual masses?

I understand that when a Earth + Satellite system forms (satellite comes into orbit) the total energy is -ve. If the energy of the system when placed at infinity is 0 (assuming P.E and K.E is 0 at ...
Alex's user avatar
  • 79
2 votes
3 answers
833 views

Why isn't total Energy used in Schwarzchild Metric instead of just mass?

The $M$ is Schwarzschild metric comes from Newtonian limit. But in the Newtonian limit the total energy also reduces to $M$. Is there any particular reason for using mass instead of total energy? ...
Nayeem1's user avatar
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3 votes
0 answers
66 views

Discrepancy between theory and real life: spool and mass system connected via pulley

I was given this problem in physics class. My teacher said that they reached the ground at the same time, but when I tested it out (video), I got drastically different results. I showed the professor ...
Christian Vela's user avatar
1 vote
1 answer
103 views

At the TOV limit (almost black hole), how much of a neutron star's primordial mass has been converted to energy?

The following rough approximation seems to show a neutron star at its Tolman–Oppenheimer–Volkoff limit of 2.17 solar masses and 12km radius, has gravitational binding energy on the same order as its ...
James Bowery's user avatar
  • 1,357
-1 votes
3 answers
278 views

What is the difference between mass gained from the Higgs field and relativistic mass gain?

I understand the equation for mass gain in special relativity, but what is physically causing the mass increase? In Higgs theory, mass is said to come from the vacuum potential (VEV). I am assuming ...
user avatar
1 vote
1 answer
690 views

What is Wald talking about here in his book "General Relativity"?

I'm reading General Relativity by Robert Wald and his notation is confusing me. On page $61$ of the book, Wald claims that by setting $c=1$ we can derive $E=mc^2$ from the following information. (1) $...
Nicholas James's user avatar
5 votes
3 answers
1k views

In our known comprehension of physics, is there any way of generating gravitational force apart from creating a concentration of mass?

In our current understanding of physics, is there any way to generate gravity apart from creating a concentration of mass? The only things I could find about this subject were Alcubierre Drives and ...
Fulano's user avatar
  • 277
-2 votes
1 answer
83 views

Why Do 137 Electron-Positron Pairs In Their Compton Wavelength Have Electrostatic Potential About Equal The Mass Energy of One Pair?

Why does taking the ratio of the mass energy of an electron positron pair to their electrostatic potential energy at their Compton wavelength yield a number very close to $\alpha^{-1} \approx 137$: $$...
James Bowery's user avatar
  • 1,357
-1 votes
1 answer
95 views

Is there a path of reasoning where Special Relativity **follows** from General Relativity? [duplicate]

Usually, General Relativity textbooks start with Special Relativity, then come to the Einstein equations followed by some metrics and end up with cosmology. I'm wondering: Is there a way back from ...
MartyMcFly's user avatar

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