Massless particle

Some tiny things have no weight. Scientists call these massless particles.

One known thing is light. We call light a photon. It has no weight. Light helps us see.

Another thing is a gluon. It helps hold small things together. We think it has no weight. We cannot see it alone.

Some things might have no weight too. A graviton might carry gravity. No one has seen it yet.

Other tiny things do have weight. Neutrinos were once thought to be weightless. Now we know they have mass.

Some tiny things have no weight. Scientists call these massless particles. A massless particle has zero mass. This means it has no weight at all.

The photon is a known massless particle. It is a gauge boson, which is a carrier of a force. The photon carries electromagnetism. We know for sure that it has no mass.

There is another particle called a gluon. It carries the strong force. Scientists think it has no mass. However, they have not proven this yet. They cannot see a gluon alone. It stays inside other tiny parts.

Some people think a graviton might exist. It would carry the force of gravity. But no one has seen it. We do not know if it has mass.

Scientists also study quasiparticles. These are not real particles. They are motions found in the structure of matter. In 2015, people found Weyl fermions. These are a type of quasiparticle. They act like particles, but they are not real.

Long ago, people thought neutrinos had no mass. Now we know they do. They change type as they move. This is called neutrino oscillation. This discovery won a Nobel Prize in 2015.

In particle physics, some tiny things have no weight. Scientists call these massless particles. These are elementary particles with zero invariant mass. One very important type is called a gauge boson. These particles act as carriers for different forces. They help the universe work in specific ways. Understanding these particles helps us see how forces move. They are a key part of the Standard Model.

One particle we know is the photon. It carries the force of electromagnetism. We have confirmed that the photon is massless. Another particle is the gluon. It carries the strong force. Scientists think the gluon has no mass. They see it through the decay products of collisions. However, they cannot see a gluon alone. It is always confined within hadrons. This makes it hard to test its mass.

Scientists have also studied other tiny particles. For a long time, people thought neutrinos were massless. They thought neutrinos might be Weyl fermions. A Weyl fermion is a type of particle. But we learned that neutrinos actually have mass. They do this through neutrino oscillation. This means they change flavor as they travel. This discovery was very important for science. Arthur B. McDonald and Takaaki Kajita won the Nobel Prize in 2015 for this work.

There are also things called quasiparticles. These are not real, fundamental particles. Instead, they are composite motions. They happen within the structure of molecular lattices. In 2015, scientists found Weyl fermions in matter. These act like particles but are not real. They are similar to things called phonons. Some theories also suggest a particle called a graviton. It would carry the force of gravity. No one has ever observed a graviton. We do not know if it has mass.

We can compare these ideas to things we know. A gluon is like a part of a team. It stays inside a group and cannot be alone. Other particles, like W and Z bosons, are different. These are known to be extremely massive. They are even heavier than iron nuclei. This shows how different tiny particles can be. Some carry forces and have no weight. Others are heavy and stay together. The study of these particles reveals the secrets of our world.

In the field of particle physics, scientists study the smallest building blocks of our universe. Some of these building blocks are known as massless particles. An elementary particle is considered massless if its invariant mass is zero. This means the particle has no rest mass. Understanding these particles is vital for understanding the forces of nature. They help explain how energy and matter interact across the cosmos.

Many of these particles are classified as gauge bosons. A gauge boson is a particle that acts as a carrier for a fundamental force. These particles mediate interactions between other particles. For example, they transfer energy and momentum to make forces work. Without gauge bosons, the fundamental forces would not function. This mechanism allows the universe to hold together in a structured way.

The most famous massless particle is the photon. The photon is the gauge boson that carries the electromagnetic force. Scientists have confirmed through direct observation that the photon is massless. It is one of two known gauge bosons thought to be massless in the Standard Model. The other is the gluon, which carries the strong interaction. The gluon's existence is inferred from the decay products of particle collisions.

While the photon is confirmed, the gluon is a bit more mysterious. Scientists expect the gluon to be massless due to compelling theoretical reasons. However, we have not confirmed a zero mass for gluons through experiment. This is because gluons are confined within hadrons. This means they can never be observed as free particles. Because they stay trapped, we cannot perform feasible experiments to test their rest mass.

Other gauge bosons exist, but they are very different from photons and gluons. The W and Z bosons are also gauge bosons within the Standard Model. However, experiments show that these particles are extremely massive. In fact, they are even heavier than iron nuclei. This contrast highlights the variety of particles that carry forces. Some are weightless, while others are incredibly heavy.

Scientists also study hypothetical particles like the graviton. The graviton is a proposed tensor boson. It is thought to be the carrier of the gravitational force in some quantum theories. However, the Standard Model does not predict or require the graviton. No experiment has ever indicated the existence of a gravitational quantum particle. Because it has never been observed, we do not know if a graviton would be massless.

There is also a distinction between real particles and quasiparticles. A quasiparticle is not a fundamental particle. Instead, it is a composite motion found within the structure of molecular lattices. These motions behave like particles, but they are not real particles. In 2015, scientists discovered Weyl fermions in matter. These are quasiparticles, similar to phonons, rather than fundamental particles.

History shows that our understanding of particles can change. For a long time, scientists thought neutrinos might be massless Weyl fermions. However, researchers discovered a phenomenon called neutrino oscillation. This is when neutrinos change flavor as they travel. This change proves that at least two types of neutrinos must have mass. This discovery was so important that Arthur B. McDonald and Takaaki Kajita shared the 2015 Nobel Prize in Physics.