# What is Negative energy: Definition and 91 Discussions

Negative energy is a concept used in physics to explain the nature of certain fields, including the gravitational field and various quantum field effects.
In more speculative theories, negative energy is involved in time travel to the past, creation of artificial wormholes, which may also allow for time travel, Krasnikov tubes, Alcubierre drive, and potentially other types of warp drives for faster-than-light space travel.

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1. ### A Negative energy in Hawking radiation

At a descriptive level, negative energy quanta enter a black hole during Hawking radiation. But when one tries to understand it mathematically, it seems that negative "energies" appear in two very different senses, which seem to be totally unrelated to each other. At one level one has Bogoliubov...
2. ### I Negative energy when a laser goes through lithium niobate crystal?

A screenshot from a book which describes it: So I am trying to picture this one: 1. A laser is "pumped" through a cylinder made from lithium niobate which is placed at 90 degrees, perpendicularly...so that the laser passes through the body of the cylinder (and not through the 2 round ends)...
3. ### B Exploring Negative Energy at the Big Bang: A Non-Mathematical Explanation

I was reading "Brief answers to big questions" By Hawking, the above pic is from a page of the book, it says that at the time of the big bang there was an equal amount of positive and negative energy, and that the negative energy never went anywhere, the space-time itself is a store of negative...
4. ### B Energy & Pendulums: Is Negative Energy Real?

Does "absorbing" negative energy from gravity cancel the upward momentum of the pendulum? Or what? Where can I see energy being negative? Does it repel stuff? It sounds impossible.
5. ### A How Does the Anomalous Doppler Effect Work?

From what I understand, the anomalous Doppler effect can occur when a charged particle moves through a medium faster than light would move through that medium; however in the paper, The Doppler Effect in a Warm Uniaxial Plasma, it mentions that this effect can occur when a dipole moves faster...
6. ### Physics C: Mechanics - Negative Energy and Potential Energy Curves

I'm currently taking a course where we are working to teach older physics concepts and combine them with calculus. I was assigned to work on teaching a unit about energy; for the most part, it stays relatively consistent and can be solved algebraically. Another topic in this unit is Potential...
7. ### I Exploring Negative Energy Density and its Impact on Universe Models

There are some universe models where ##\Lambda < 0##. In this case, the energy density of the dark-energy becomes negative. At this point, does it make sense to talk about "negative dark energy density"? Or is it possible to think of this energy as curvature on space-time? Such that, ##\Lambda <...
8. ### I Zero-Energy Universe: Reliable Source?

In https://en.wikipedia.org/wiki/Zero-energy_universe and in https://en.wikipedia.org/wiki/Negative_energy, the idea of a negative energy balancing out the positive energy in the universe is advanced. However, these two sites use descriptions of "quantum fluctuations", "virtual particles"...
9. ### I Negative Energy -- Are QI/QEI's Real?

Hello all I wasent sure if I should post this here or in GR. I was wondering anyone could help clear something up. In my research of negative energy, the idea of QI or QEI (Quantum Energy Inequalities) has come up, limits on negative energy. I have seen many papers showing mathematical...
10. ### What hypothetical properties would negative energy have?

I would like to know about the hypothetical properties of hypothetical negative energy--most especially the properties that would be useful for a science fiction writer to know. If such energy existed, could it be used in a drive for space craft? An FTL drive? For a weapon? A safety...
11. ### I Detect Negative Mass Matter: Experiments in Solar System

How could we detect negative mass matter? The only proposal I've ever heard of is that we could detect there's a cutoff frequency in the gravitational waves we receive, due to attenuation of those lower frequency waves by negative matter. Are there more experiments that could be conducted...
12. ### I Is there a mechanism for creation of negative energy density

Excuse me for bad wording in the title, but there is only so much you can do with the character limit. So, has there ever been a proposal for a mechanism through which negative energy density could be created? Or the only possibility considered so far was that it would have been created in the...
13. ### I Hawking Radiation and the Negative Energy Particle

The following from Wiki re Hawking Radiation:“... vacuum fluctuations cause a particle–antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole while the other escapes. In order to preserve total energy, the particle that fell into the...
14. ### I Wormholes & Arbitary High Energy: Exploring Possibilities

Could we hypothetically use it to create a region of space with the magnitude of the stress component of stress energy tensor greater than magnitude of mass denisty component?
15. ### I CMB and the reference point for vacuum energy

From the basic definition of vacuum energy as being tied in with the Uncertainty principle, I would expect this not to include the Cosmic Background Radiation. Right? On the other hand, in figuring out (a) the Casimir effect, one attributes the force to the field between the plates carrying...
16. ### A Negative mass and antimatter

In physics we cannot easily imagine “negative” energy for a particle (not a field) in order to have “negative” mass, although the first concept of Dirac for antiparticles was that they were “holes” that were opposite to particle existence and there was a minus in front of mc2.Regardless of...
17. ### I Relationship between negative mass, energy and antimatter

What is the relationship between negative energy, negative mass and antiparticles? I have read some articles but I am still confused. Does negative mass exist? Does negative energy exist with the exception of the Kasimir effect which I understand. Are antiparticles really only the negatice...
18. ### I Calculation of negative energy density in a Casimir cavity

Hello, I would like to know how to calculate the negative energy density in the region between two Casimir plates, given a distance between two parallel plates. Thanks, much appreciated!
19. ### B Does physics allow us to create large amounts of negative energy?

Hello. Casimir effect allows to create negative-energy-density (NED), but ONLY SMALL AMOUNTS of it. I wonder if physics generally allows for the existence of negative energy in large quantities. I think that if the negative energy can be produced in small quantities, it can also occur in larger...
20. ### B Exploring Negative Energy in the Universe: Examples, Evidence, and Impact

Hawking and others have claimed that there's a negative energy associated with gravitation that makes the universe's total energy balance -- including all the energy in all the mass in all the matter in the universe -- zero. But there was no such thing as negative energy in any type of physics...
21. ### Question: Accelerating Universe = Net Positive Energy?

Physicists have observed the cosmic radiation background to conclude that the universe is flat (or within the margin of error of being flat). This means that the Universe contains the critical density needed to keep it flat, which is a mix of ordinary matter, dark matter and dark energy (I...
22. ### Negative Energy Density in EM Waves?

Homework Statement The problem I have is that we are asked to show the complex relative permittivity of a good conductor is erc = 1 + i(sigma)/(omega*epsilon_0) where sigma is the conductivity and omega is the frequency of an electromagnetic wave in the medium. This is fine, I calculated it...
23. ### Traversable wormhole without negative energy (paper)

I'd like to know your views. Is it too good to be true? Or is there any obvious blunder?http://arxiv.org/abs/1509.07854 NUT wormholes Gérard Clément, Dmitri Gal'tsov, Mourad Guenouche (Submitted on 25 Sep 2015) We show that supercritically charged black holes with NUT provide a new setting for...
24. ### Negative energy is repulsive, but PE is negative, so?

I am missing something basic here. In https://en.wikipedia.org/wiki/Negative_energy, it is stated that "a universe in which negative energy dominates will either expand indefinitely or..." But gravitational potential energy is negative, so if I make the substitution, I would get "a universe in...
25. ### Universe: Is it Nothing? | Steven

Dear PF forum, I once read that the universe IS nothing. And "FROM", too. But I like to ask about "IS". They say that "Gravity" is negative energy. So if you add all the masses and energies and gravity, it would be zero. What I'd like to ask is this. A. Is all Mass + Energy + Gravity = 0? B. Is...
26. ### Negative energy wave

I'm reading Padmanabhan's Gravitation. In section 3.4, at some point he writes the Lagrangian below: ## L=-\frac 1 2 \partial_\sigma V_\rho \partial^\sigma V^\rho-J_\rho V^\rho ## He then says that the sign of the kinetic term causes the time component of the V field to propagate as a wave with...
27. ### Forming Stars: 2 Conditions and Criteria Explained

2 conditions to form a star - all atoms in the gas cloud must be gravitationally bound to each other (so the virial theorem applies) - the cloud must permanently lose overall energy E=-GMm/2R therefore R=-GMm/2E, so for R to become smaller and the energy to also become smaller the energy needs...
28. ### Negative Energy in Quantum Mechanics: Can Particles Exist?

I'm coming here from going through the Dirac delta potential in QM to clear my mind about the case when E < 0, which as a result produces the single bound state solution in that potential. The thing that's vexing my soul(if we have one anyways) is the fact that a particle is taken to be in...
29. ### Question about an Alcubierre warp drive's negative energy requirement

I've been reading Dr. Harold G. White's work on recent developments in Warp Field Mechanics, and thought up the following question: Could a proof of the Alcubierre warp drive concept be made by using a warp bubble energy differential whose flat-space energy density level was positively offset...
30. ### Alan Guth thought experiment about negative energy and gravity

Recently, I watched a lecture with Alan Guth. He made an interesting statement. He said that to create an electric field requires work, because the like-charges prefer to repel one another, therefore this requires energy to bring them together. However; because gravity is attractive, it requires...
31. ### Defining negative energy of gravitational field

I have been learning that gravity has a negative energy associated with it. I've heard this stated a couple different ways, but I would like to understand a distinction. One line of thought declares that the potential energy of an object within a gravitational field is negative. Another line...
32. ### Negative gravitational energy - negative energy gravitons?

We know that gravitational energy is negative (zero energy universe theory). If the mediator particles (bosons) of the gravitational interaction are gravitons, then the energy of the gravitons would be negative?
33. ### Understanding Negative Energy in Earth-Satellite Systems

the potential energy of a earth-satellite system is -U. the kinetic energy of the satellite is K = -U/2. the mechanical energy M = -K. this is not true. the satellite is in equilibrium and the ∂θ change caused is limits to zero. the PE of the satellite cannot cause acceleration...
34. ### Regarding graviton and negative energy

Hi. I recently listened to a lecture by Alan Guth, speaking about cosmological inflation. He made the statement that the energy of a gravitational field is negative (followed by a great thought experiment with a collapsing shell of matter to demonstrate this). I am curious; does this mean that...
35. ### Boltzmann vs. Gibbs entropy, negative energy

This article insinuates that the physics community had forgotten Gibbs entropy long ago and has used Boltzmann entropy since. Isn't this nonsense? For me it was always clear that Boltzmann entropy is problematic...
36. ### Researching Negative Energy: Where to Start?

Hello, I apologize if this is not posted in the right section. I've been trying to learn about negative energy, the kind that can't bend space-time, though when I try to search it, it mostly shows random sites on mythical negative spirtits being negative. So does anyone know a place I can...
37. ### Negative energy capacitor?

The electrostatic energy in a capacitor is negative is it not? If one had enough positive and negative charge on the plates so that the electrostatic energy was greater in magnitude than the rest mass energy then the system as a whole would have a negative total energy. Would this be possible...
38. ### Space and Negative Energy

I watched Stephan Hawking's into the universe, I know it's more of a way to make science mainstream than to educate people, but in the episode about is there a god, he said that space was a negative energy and that it equaled the same amount as the energy of the universe. I haven't looked into...
39. ### How negative energy solution has positive energy in lab?

In QFT equations, there are not only positive energy solutions, but negative ones as well. Dirac had the hole theory. But the sea may have infinite charges and gravity effects. And then QFT textbooks just explain the negative solution as anti-particle. But in the lab, we measure the...
40. ### Photon with negative energy, Compton Scattering

Hello PF people, Homework Statement In a Compton scattering event, after the collision, the Photon has an energy of 0.12 MeV and the Electron has an energy of 0.04 MeV. Find the following: i) The Wavelength of the photon before the collision. ii) The scattering angle for the photon...
41. ### Quantity of negative energy

At what amounts can negative energy be produced by the Casimir effect? I know these are very small, but I am curious to know how small.
42. ### Negative energy in the Schrödinger equation

When my book deals with bound states and scattering states it puts: E<0 bound state, E>0 scattering state. What reference for the potential have been used for these?
43. ### Negative energy eigenvalues of Hamiltonian

Homework Statement If I have a Hamiltonian matrix, \mathcal{H}, that only depends on a kinetic energy operator, do the energy eigenvalues have to be non-negative? I have an \mathcal{H} like this, and some of its eigenvalues are negative, so I was wondering if they have any physical...
44. ### Negative energy: same in Casimir, Hawking rad, & spherical space?

The term "negative energy" is used (a) for the energy below the vacuum energy between the two plates in the Casimir effect, (b) the energy carried by the sister particle to the radiated particle in Hawking radiation, that is, the particle from the matter-antimatter pair which goes into the...
45. ### Why is a gravitational field negative energy ?

Why is a gravitational field "negative energy"? The idea about the universe having zero net energy, as explained for instance in http://en.wikipedia.org/wiki/Zero-energy_universe, seems to be that gravity has 'negative energy', which offsets the positive energy of all the matter and radiation...
46. ### Negative Energy and Mass Symmetry

I was wondering about a system, specifically quantum, though classical solutions are still welcome, which was resisting all applications of Noether's Theorem, and related techniques. If a system is invariant under a switch from E→-E AND m→-m, then what are the conserved quantities (in analogy to...
47. ### Exploring the Dirac Equation: Positive & Negative Energy Solutions

Hi! Homework Statement 1. Substituting an ansatz \Psi(x)= u(p) e^{(-i/h) xp} into the Dirac equation and using \{\gamma^i,\gamma^j\} = 2 g^{ij}, show that the Dirac equation has both positive-energy and negative-energy solutions. Which are the allowed values of energy? 2. Starting...
48. ### What is negative energy and how does it relate to the capacity for work?

If the positive energy is the capacity to perform work what about the negative energy?
49. ### Negative Energy in Particles: A Conundrum

I'm kind of struggling with the concept of energy. A particle in a conservative field has kinetic and potential energy (E=T+U), but I can always choose an inertial frame where the motion of the particle is zero, which means I can change the the particle's kinetic energy by just switching frames...
50. ### Why Does Electron Energy Have Negative Values?

hi, why are the energy levels of electrons in say a hydrogen atom -13.6ev, -3.4 eV etc ? i thought energy is always positive? what does the negative mean? thanks!