person rather new to physics here, and I just started on a rather simple book on particle physics, but I was flustered to learn that there are particles without mass enforcing the fundamental forces (Like the gluon or the Higgs boson). There is some Greek term for it but I don't remember. I just can not comprehend this because my idea of a particle is something like a grain of sand floating in space: You can fiddle around with it and it can interact with other particles. But how can a particle exist without mass? Or how can it interact with other particles if it does not have mass? What even is a particle at this point? I'm sorry if its a stupid question but this just bothers me.
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3The intuitions of everyday life are not necessarily valid at other scales, either large or small. – Aug 10 '21 at 20:56
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3Massless particles still carry energy and momentum. – md2perpe Aug 10 '21 at 21:07
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This may help - How can a red light photon be different from a blue light photon? – mmesser314 Aug 10 '21 at 23:54
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If you learned about the Higgs then should have gone through the Higgs mechanism that states that particles with mass oscillate in the Higgs potential, while massless particles do not. https://en.wikipedia.org/wiki/Higgs_mechanism. Correct me if I am wrong if you have not learned this yet. If not, then is quite interesting to know where mass comes from and you should read up on it. – Tachyon Aug 11 '21 at 01:47
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1The Higgs boson is not massless. In fact, it has one of the higher masses among elementary particles. – Sandejo Aug 11 '21 at 05:43
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Closely related: If photons have no mass, how can they have momentum? – ACuriousMind Aug 11 '21 at 08:48
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1See The Higgs Field, explained - Don Lincoln for an intuitive explanation of how the Higgs Mechanism gives mass to some particles, but not to others. It is a bit old. The Higg particle has been discovered since it came out. – mmesser314 Aug 11 '21 at 14:10
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This is not a stupid question and you are not alone. Many have struggled with the same concern when first introduced to the idea of a massless particle. In physics today, we use the word mass in association with the properties of a particle that is at rest (not moving). However, it is also true that mass is associated with energy through Einstein's famous equation: E = mc2. This introduces the idea that as the energy of an object increases with its velocity that this will result in an increase in the overall energy content of the object. This energy content can be thought of as being partly made up from the object's mass (when it is at rest) and partly from the mass associated with the energy required to provide motion to the object. There is no requirement that both of these conditions must contribute to the overall energy content. For example, an object sitting on the table has only mass (from being at rest) and no additional mass (energy) associated with its motion (because it is at rest). Likewise, it is possible for an object to get all of its mass from the energy of its motion with no contribution from an at rest state. This is what is meant by a massless particle. Generally speaking, a massless particle cannot exist at rest, it must be moving to achieve a property of mass that comes from the energy of its motion.
JRL
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4a massless particle cannot exist at rest, it must be moving: more precisely, it must be moving with the speed of light. – Thomas Fritsch Aug 10 '21 at 23:18
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2'moving to achieve a property of mass' The concept of relativustic mass is obsoletele. Please don't spread this concept. – my2cts Aug 11 '21 at 08:19
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3Echoing my2cts comment, we have another popular question on why "relativistic mass" is obsolete in modern parlance. – ACuriousMind Aug 11 '21 at 08:53
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As for the title question, massless particles are useful because despite being massless they still carry information. Individually it's a tiny amount but added up it can be any amount needed.
SoronelHaetir
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