# Negative energy

#### Kolten

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 research negative energy properly?

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#### kaplan

All forms of energy bend spacetime.

But if you want you can pretend gravity doesn't exist, or consider a situation where general relativistic effects are negligible. In that case, there are lots of examples of negative energy. For example gravitational binding energy is negative in Newton's theory, as is the electric potential energy between two opposite charges. In general you can add or subtract any overall constant you want from all potential energies without changing anything (so you could make all energies negative if you really wanted to).

#### WannabeNewton

I don't know why this is in QM, it should be in GR but anyways: there is a very famous result in GR that was proven most elegantly by Ed Witten which addresses your question. It is called the positive energy (mass) theorem: http://en.wikipedia.org/wiki/Positive_energy_theorem

This is unlike Newtonian gravitation theory wherein the total energy of a system has no lower bound in the reals.

#### ZapperZ

Staff Emeritus
2018 Award
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 research negative energy properly?
The problem whenever we get a question like this is that (i) there is a proper and clear idea of "negative energy" as used in physics; and (ii) it is unclear what you mean by "negative energy".

First of all, where did you get the idea of "negative energy"? Did you hear it from somewhere or read about it somewhere? A valid reference would be nice.

Secondly, based on what you read, what exactly do you think you understand as being "negative energy"?

It is essential that we clear this up because what you mean by negative energy might not be what physicists consider to be negative energy. Without that clarification, we could be talking about two different things and all our responses and discussion will simply miss each other.

Take note that just in classical mechanics alone, "negative energy" is rather common. An attractive field such as gravity is often designated as a negative potential energy. This is because we can always move the reference "zero" level to where ever we wish, since in practically all instances, it is the CHANGE in the energy that matters, rather than the absolute value.

So it is unclear if you are aware of this, or if you have something in particular in mind. Thus, we need a lot more explanation from you.

Zz.

#### Kolten

Alright, well I heard about it when reading up on one of NASA's projects the Quantum Thruster. Negative energy used by the quantum thruster bend both space in front of it and behind of it. But since my understanding of the energy is so limited, I can't describe is anymore.