Question about massless things

[Bradfordly1]

Are there any other things/objects in our universe that are massless other than Gluons and Photons? I guess energy is massless, but it's not so much a thing, more-so a property.

 

[Drakkith]

I guess energy is massless, but it's not so much a thing, more-so a property.

Indeed, energy is a property of objects and systems of objects, it is not something in and of itself. But it does have mass. Or, rather, arranging a system such that it has more energy than before will mean it has more mass as well.

 

[mathman]

Mass and energy are equivalent. When you say something is mass-less, it usually means that the rest mass is zero. This applies to photons and gluons and gravitons (if they exist).

 

[Khashishi]

Graviton, if it exists at all.

 

[rkolter]

Don't forget Weyl fermions.

 

[Bradfordly1]

What about a shadow, or digital information?

 

[Khashishi]

Those aren't physical objects.

 

[rkolter]

The OP didn't really qualify what a Thing or an Object was. If you want a macro-sized object, it would have to be an object made of massless particles, like a laser beam.

 

[Austin Z W]

Laser is an acronym for light amplification by stimulated emission of radiation. It is made of photons of a specific wavelength, but photons none the less and it does have mass just as all photons do, however small it is.

 

[Drakkith]

but photons none the less and it does have mass just as all photons do, however small it is.

The mass of the beam is non-zero, but the mass of each photon is zero.

 

[Austin Z W]

Each photon has energy which means it has mass. The mass is usually said to be zero in most cases and equations because it is such a small amount of mass.

 

[Nugatory]

Each photon has energy which means it has mass. The mass is usually said to be zero in most cases and equations because it is such a small amount of mass.

That is not correct. The mass, energy, and momentum of a particle are related by ##E^2=(mc^2)^2+(pc)^2##. For a photon we have ##E=pc## so a bit of algebra will quickly show that the mass of a photon is precisely exactly zero.