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Gregg Jaeger | Entropy | (2019)
Primary Link Pubmed DOI Openalex Full text (OA)

Abstract

, or are dependent on the imposition of classical intuitions on quantum systems, or are simply beside the point. Several reasons are then provided for considering virtual particles real, such as their descriptive, explanatory, and predictive value, and a clearer characterization of virtuality-one in terms of intermediate states-that also applies beyond perturbation theory is provided. It is also pointed out that in the role of force mediators, they serve to preclude action-at-a-distance between interacting particles. For these reasons, it is concluded that virtual particles are as real as other quantum particles.

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Plain English Takeaway

Virtual particles are just as real as other particles, even though we can't see them directly. They play a key role in how forces work between particles.

Study Aim

The paper aims to address whether virtual particles, which appear in quantum field theory as short-lived intermediaries in particle interactions, are less real than other quantum particles. The author examines common arguments against the reality of virtual particles and provides reasons to consider them as real as any other particle described by quantum field theory. Simply put: The paper asks if virtual particles are real and argues that they are just as real as other particles.

Study Design

This is a philosophical and theoretical analysis based on the mathematical and conceptual framework of quantum field theory (QFT). The author reviews how virtual particles are defined and used in calculations, especially in Feynman diagrams, and examines arguments from the scientific literature. The paper does not involve experiments or new data but instead analyzes existing theories and interpretations. Simply put: The author looks closely at how scientists talk about and use virtual particles in theory, not in experiments.

Findings

The paper demonstrates that arguments against the reality of virtual particles are based on misunderstandings or on distinctions that depend on calculation methods, not on physical differences. The author shows that virtual particles have descriptive, explanatory, and predictive value in quantum field theory. They are essential for explaining how forces work without action-at-a-distance and for making accurate predictions in particle physics. The paper concludes that virtual particles are as real as other quantum particles, since their effects can be observed and measured indirectly. Simply put: The study finds that virtual particles are real because they help explain and predict what happens in the world of tiny particles.

Referenced In

StarTalk

Season 17, Episode 24: Why Should Gravitons Even Exist?

Hey StarTalkians! Season 17, episode 24 was another Cosmic Queries edition, where Neil and Chuck sat down to answer viewer questions. This included an absolutely fantastic question about whether gravity is a true force and whether the graviton is even needed:

Cosmic Queries – Total Darkness - StarTalk Radio

(Question starts at 25:50)

Neil’s answer covered the basics but left the core idea hanging. So let’s add to it a little.

Virtual and Free Particles: The Photon and Electromagnetism

As argued in an informative Big Think article, we need to distinguish between free and “virtual” particles to understand why gravitons probably exist.

For electromagnetism, the “free” photon is the thing associated with light waves. Light waves are made of photons, similarly to how water waves are made up of water molecules.

But electromagnetic interactions – like two magnets attracting each other – are mediated by virtual photons. These are “virtual” because they can’t be observed; they’re more like abstractions that help us solve problems and predict experiments . They’re a manifestation of the underlying field.

Virtual and Free Gravitons

So if we can describe gravity in quantum terms – a big “if” – we’d use a virtual particle to carry the force too. This would be exchanged during gravitational interactions, and would arguably only exist in our calculations.

But gravitational waves also exist, and like a light wave, these are probably composed of free gravitons. You can even recreate the famous LIGO result in this framework. It works exactly like the photon example.

Answering the Question

Now we can finally address this fantastic question. It reflects a common misconception about gravity, that it is “not a force” in some way. Neil shared the key quote: “Spacetime tells matter how to move; matter tells spacetime how to curve.”

The thing the question (and Neil’s answer) misses is: how does matter tell spacetime how to curve? Once it is curved, the question is right – there’s no typical force at play. But the fact that matter curves spacetime at all is the effect of the force. Einstein’s equations don’t describe interactions between two masses, but the interaction between mass or energy and spacetime itself.

Matter’s interaction with the Higgs field (via the famous boson) gives it mass. Virtual gravitons, on the other hand, mediate the interaction between that mass and the fabric of spacetime.

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