Search PBS Space Time


2022-08-24: What Makes The Strong Force Strong?

  • 17:53: ... Jahrmarkt and Gabriel Monteiro de Castro Both ask the same question: if virtual particles don’t actually exist, but instead are a calculation tool to describe ...
  • 18:07: After all, Hawking radiation is sometimes portrayed as a virtual particle-antiparticle pair being separated by a black hole event horizon.
  • 18:15: ... the answer is that the story about separation of virtual particles by the event horizon is a meant to be an intuitive picture of what’s ...

2022-08-17: What If Dark Energy is a New Quantum Field?

  • 00:36: ... Empty space buzzes with random activity that we sometimes describe as virtual particles popping into and out of existence, driving accelerated expansion. But ...

2022-08-03: What Happens Inside a Proton?

  • 07:53: ... are way too tumultuous to be easily   approximated by virtual particles. Instead we have to try to model the field more ...
  • 08:30: ... reduce the number of field configurations by approximating them as virtual particles.   But for QCD we have to stick with fields, so we need a different ...
  • 14:08: ... quantum field more directly. That helps us put to bed the idea that virtual particles are   more than an approximation of what these ...

2022-06-22: Is Interstellar Travel Impossible?

  • 19:10: Otinane Yos asks whether we can be sure that virtual particle - antiparticle pairs get separated near a Black Hole event horizon.
  • 19:36: ... virtual particle picture is a sort of colloquial interpretation of what’s going on, ...

2022-06-15: Can Wormholes Solve The Black Hole Information Paradox?

  • 03:20: ... radiation is that the black hole is swallowing and emitting virtual particles. We can think about the vacuum   of space as being filled with ...

2022-04-27: How the Higgs Mechanism Give Things Mass

  • 16:02: ... model  particles that could have a ghostly presence   as virtual particles in the energy field of  the boson. The fact that FermiLab ...

2022-02-10: The Nature of Space and Time AMA

  • 00:03: ... vacuum energy density the old one has the same kind of behavior of virtual particles uh it has the same amount of dark energy quickly okay the density of ...

2022-01-27: How Does Gravity Escape A Black Hole?

  • 06:54: There’s a bit of a misconception in how we think about virtual particles.
  • 07:02: Virtual particles aren’t localized like that.
  • 07:55: That’s easy - these are virtual particles, and in quantum field theory, virtual particles are not restricted by the speed of light.
  • 08:06: ... between particles result from the sum of all virtual particle interactions, possible and Impossible, and the speed of light limit ...

2021-12-10: 2021 End of Year AMA!

  • 00:02: ... or repelled from each other are so influenced by the exchange of virtual particles virtual bosons um in the case of say an electron and a proton the uh ...

2021-10-05: Why Magnetic Monopoles SHOULD Exist

  • 07:56: ... and Dirac argued that this makes it a mathematical figment, kind of like virtual particles. ...

2021-06-16: Can Space Be Infinitely Divided?

  • 09:58: ... is fundamentally uncertain.   In the same way that you get virtual particles on subatomic scales, on the Planck scale you   get virtual ...

2021-04-21: The NEW Warp Drive Possibilities

  • 14:18: The probability that a particle will interact with other massive virtual particles is proportional to the square of that particle’s own mass.
  • 14:52: That said, there are other ways to track a particle’s interactions with virtual particles.
  • 15:01: ... of those decays products are sensitive to the complex interactions with virtual particles that happen during the ...

2021-04-07: Why the Muon g-2 Results Are So Exciting!

  • 05:14: For a deeper dive in Feynman diagrams, virtual particles, and quantum electrodynamics, we have you covered, episode list in the description.
  • 07:43: The quantum vacuum is seething with an incredible variety of possible virtual particles.
  • 08:19: The probability of interaction between a particle and some massive virtual particle is proportional to mass squared.
  • 08:39: And it's 40,000 times more likely to encounter any completely unknown virtual particles that might be hiding out there.

2020-06-22: Building Black Holes in a Lab

  • 05:25: ... mass as a type of radiation. The popular description is that pairs of virtual particles appear near the event horizon and are separated - one escapes and one ...

2020-05-27: Does Gravity Require Extra Dimensions?

  • 11:58: This is the negative pressure due to the exclusion of quantum vacuum modes, or virtual particles, between two very closely separated plates.

2020-04-28: Space Time Livestream: Ask Matt Anything

  • 00:00: ... if I can describe how dark energy and evaporating black holes with virtual particles do not violate conservation laws so let's start with let's start with ...

2020-02-03: Are there Infinite Versions of You?

  • 15:42: ... t channel is where 2 particles scatter off each other by exchanging a virtual particle, while the s-channel is where the particles annihilate each other into a ...

2020-01-27: Hacking the Nature of Reality

  • 02:16: ... are calculated by adding up the exchanges of infinite number of virtual particles. ...
  • 08:05: ... ways this can happen as follows: 1) the ingoing particles exchange a virtual particle which deflects or transforms them into the outgoing particles - this is ...
  • 10:33: And as we discussed in our episode on virtual particles, the physical-ness of these states are questionable at best.

2019-08-19: What Happened Before the Big Bang?

  • 02:58: You can think of a field with a high field strength as being full of virtual particles.

2018-11-07: Why String Theory is Right

  • 14:14: ... one of the most misunderstood concepts in quantum mechanics, the idea of virtual particles and their tenuous connection to ...
  • 14:44: ... fluctuations can be approximated as the sum of many virtual particles, but the particles themselves are just convenient mathematical building ...
  • 14:56: Eddie Mitch asked whether the virtual particles are required to explain the Casimir force.
  • 15:02: ... Casimir effect is sometimes explained as resulting from the exclusion of virtual particles between two very closely separated conducting plates which results in ...
  • 15:14: ... it isn't-- but if it is, then it's still misleading to attribute it to virtual particles. ...

2018-10-31: Are Virtual Particles A New Layer of Reality?

  • 00:02: Let me tell you a story about virtual particles.
  • 00:29: And every time two particles interact, an infinite number of virtual particles mediate infinite versions of that one interaction.
  • 00:39: Virtual particles sound pretty cool, I guess, but is this really how they work?
  • 00:45: Seriously, what are virtual particles?
  • 01:26: A more recent mathematical hack is the virtual particle.
  • 01:41: So will virtual particles also prove to represent a new underlying aspect of reality?
  • 01:57: First, let's get to the origin of virtual particles.
  • 03:12: Those interactions are mediated by virtual particles.
  • 03:16: In that sense, virtual particles are the building blocks of our approximation of the behavior of quantum fields.
  • 03:54: Every one of these interactions is described with a simple excitation and transfer of particles-- virtual particles.
  • 04:22: The virtual particles never exist independently.
  • 04:25: Instead, virtual particles are the mathematical building blocks we use to approximate the complex states of interacting fields.
  • 04:53: All those that both start and end within the diagram are virtual particles.
  • 04:58: ... field theory calculations, but they also add to the misconception about virtual particles. ...
  • 05:09: They sure make it look like virtual particles are doing regular particle stuff like traveling through space but that's just not the case.
  • 05:18: ... Virtual particles share some properties with their real counterparts-- in particular, ...
  • 05:45: Virtual particles are our mathematical representation of the quantum mechanical behavior of fields, and that behavior is weird.
  • 07:03: These virtual particles sort of exist everywhere at once, which is confusing.
  • 07:09: ... one of these infinite possible virtual particles represents a quantum of energy in a single possible vibrational mode of ...
  • 07:20: In a way, a virtual particle represents a pure excitation of the field, an idealized case of perfectly defined momentum.
  • 07:29: The Heisenberg uncertainty principle tells us that the perfectly defined momenta of virtual particles means completely undefined position.
  • 08:42: So that's the deal with virtual particles in particle interactions, but we also hear about the role of virtual particles in a complete vacuum.
  • 08:52: ... might have heard the quantum vacuum described as his roiling ocean of virtual particle-antiparticle pairs popping into and out of existence, the so-called vacuum ...
  • 10:48: Virtual particles are not popping into and out of existence in the absence of any else.
  • 11:03: Stephen Hawking himself was the first to use virtual particles as an intuitive way to describe his radiation.
  • 11:50: ... on these, and just like with Hawking radiation, you don't need for virtual particles to have an independent existence to explain these ...
  • 12:00: So to recap, virtual particles are best thought of as a mathematical device to represent the behavior of quantum fields.
  • 12:08: ... original idea of virtual particles came about as a calculation tool in perturbation theory as we tried to ...
  • 12:42: So what about virtual particles?
  • 12:53: It turns out there is a version of quantum field theory that doesn't use virtual particles at all.
  • 13:05: It doesn't rely on perturbation theory, and so it doesn't use virtual particles while ultimately giving the same results.
  • 13:13: Ergo, virtual particles are probably just a mathematical artifact.
  • 13:17: There is no good reason to believe that virtual particles exist outside the math we use to approximate the behavior of quantum fields.

2018-09-20: Quantum Gravity and the Hardest Problem in Physics

  • 15:01: VoodooD0g points out that the vacuum isn't really empty, what, with all the virtual particles popping into and out of existence.
  • 15:16: The phantom virtual particles represent both the absence of particles and every possibility of particles.

2018-08-23: How Will the Universe End?

  • 16:20: ... fit maths randomly to the observations when we come up with stuff like virtual particles and that it's so weird that that actually ...

2018-08-15: Quantum Theory's Most Incredible Prediction

  • 09:50: ... ways the electron can interact with the EM field, with crazy networks of virtual particles and virtual matter, anti-matter loops between the real ingoing and ...

2018-06-20: The Black Hole Information Paradox

  • 14:11: Virtual particles in general are just a way to mathematically account for the infinite ways a quantum field can communicate its influence.
  • 14:19: Virtual particles don't have the same restrictions as regular particles.
  • 14:35: ... this picture, virtual particles can escape a black hole to communicate the influence of the charge ...

2018-03-15: Hawking Radiation

  • 01:54: ... pairs of virtual particles, matter and antimatter, spontaneously appear and then annihilate each ...
  • 03:17: And those fluctuations give us what we think of as virtual particles.
  • 03:21: Now don't take the existence of virtual particles too seriously.
  • 08:19: It's fair to interpret this mixing as the promotion of what were once virtual particles into reality.

2018-01-17: Horizon Radiation

  • 09:22: As discussed in a previous episode, we can think of the vacuum as a sea of virtual particles.

2017-11-22: Suicide Space Robots

  • 12:46: Hawking radiation is related to this whole vacuum energy virtual particle thing.

2017-11-08: Zero-Point Energy Demystified

  • 04:22: If you bring a pair of conducting plates very close together, a proportion of the virtual particles will be excluded from between them.
  • 06:02: The fact is, any acceleration of a real particle involves a transfer of momentum between real particles via virtual particles.
  • 06:10: Virtual particles, and hence, the quantum vacuum, mediate all forces.

2017-11-02: The Vacuum Catastrophe

  • 00:35: Virtual particles appear and vanish from nowhere in seeming violation of our intuitions about the conservation of mass and energy.

2017-10-25: The Missing Mass Mystery

  • 11:02: Last week, we talked about virtual particles, zero point energies and the nature of nothing.
  • 12:21: ... also asks, if virtual particles control faster than the speed of light, can't they escape the event ...

2017-10-19: The Nature of Nothing

  • 04:20: ... call these virtual particles, and they seem to be the machinery under the hood of all particle ...
  • 04:41: Virtual particles are the links governing all particle interactions in the famous Feynman diagrams.
  • 04:48: But to properly calculate an interaction of real particles, every imaginable behavior of the connecting virtual particles must be accounted for.
  • 05:01: For example, in QFT, virtual particles can have any mass and any speed, including speeds faster than light, and can even travel backwards in time.
  • 05:16: The ambiguous realness of virtual particles seems to grant them some surreal freedoms, but there are restrictions.
  • 05:24: For example, quantum conservation laws must be obeyed, so most virtual particles are created in particle-antiparticle pairs.
  • 05:33: But the ultimate price is that virtual particles can exist only for the instant allowed by the Heisenberg uncertainty principle.
  • 06:23: ... can be argued that virtual particles are just a mathematical tool to describe the behavior of a dynamic ...
  • 07:10: ... first hint of the existence of virtual particles came in 1947, when Willis Lamb and Robert Rutherford noticed a tiny ...
  • 07:50: Virtual particle-antiparticle pairs in the space between the orbitals and the nucleus align themselves with the electric field.
  • 08:15: Another way to hunt for virtual particles is through their bulk effect on the vacuum.
  • 10:53: ... field theory, with its dependence on virtual particles and vacuum fluctuations, is one of the most successful theories in all ...

2017-08-10: The One-Electron Universe

  • 06:49: That virtual particle in the middle may be an electron traveling forwards or backwards in time.

2017-07-26: The Secrets of Feynman Diagrams

  • 06:15: The particles that have their entire existence between vertices within the diagram but don't enter or leave are called virtual particles.
  • 08:56: ... that intermediate stage between vertices, the electron is a virtual particle, which means we include all possible paths it might take, as long as they ...

2017-07-12: Solving the Impossible in Quantum Field Theory

  • 02:55: There are other types of virtual particle whose existence is similarly ambiguous.
  • 08:21: ... so-called loop interactions, like when a photon momentarily becomes a virtual particle-anti-particle pair and then reverts to a photon again, or when a single electron emits ...
  • 10:27: ... theory-- for example, the infinite shielding of electric charge due to virtual particle-anti-particle pairs popping into and out of ...

2017-01-11: The EM Drive: Fact or Fantasy?

  • 07:28: To exchange momentum with virtual particles over a distance longer than a Planck length, those particles need to become real.
36 result(s) shown.