For ages, people have believed that energy can only be positive. However, recent researches have proven that there is also negative energy, which is more difficult to obtain. Scientists have recently started to ask themselves if it is possible to get energy from space. Read this article to understand the answer to this question.

Researchers from the Universite Libre de Bruxelles in Belgium, TU Vienna in Austria, and IIT Kanpur in India have worked in collaboration to find out more information about negative energy. They have conducted prominent research which proved that it is possible to borrow energy from empty space, but then it needs to be returned.

## Energy according to general relativity

Professor Daniel Grumiller from the Institute of Theoretical Physics at the TU Wien reminds us that according to the theory of general relativity ‘energy is more than zero, at all times and everywhere in the Universe.’ This statement is closely linked to gravity. Imagine that we remove every small part of a specific volume, and we leave nothing that can carry energy, then from what we know, we can conclude that we have reached a limit.

If we continue this flow of thoughts, we will conclude that negative energy is a negative mass. We know that positive masses attract each other, then if a negative mass appears, it will be transformed into repulsive force.

## Energy according to Quantum theory

Professor Daniel Grumiller says that, according to Quantum theory, negative energy is possible, and it is likely to borrow it from a vacuum at a given place.

So if we combine what we know from the theory of general relativity and the Quantum theory, we will find that energy that is lower than zero is possible but only under specific circumstances – in a particular range and within a given limit of time. In 2017 scientists proved the so-called ‘’Quantum Zero Energy Condition’ according to which there should be some limits of the energy borrowed from empty space.

## Entanglement Entropy

It is a quantum physical quantity that determines what the amount of energy that we can borrow from vacuum before it reaches its ‘credit limit’ is. This quantum physical quantity is known as entanglement entropy. It is entanglement entropy that shows to what extent quantum physics influences the behavior of a system.

There is a possibility that entanglement entropy may be of crucial importance somewhere in space, for example, near the rim of a black hole. If this happens, then negative energy can occur for some limited time which means that negative energy is possible at that point in space.

## Physics – the science of contradictions

As a conclusion, we can say that physics has once again proven to be contradictional as we have two theories that collide in the face of the theory of general relativity and the quantum theory. Now we know that negative energy does exist and we can borrow energy from a vacuum, but we should always return it as if we borrow money from the bank.