- 3430 - PHYSICS - energy and massless particles? There could be a lot of massless things out there that either there’s no way to look for them, or rather we haven’t figured out how to look for them. It could be that there’s this whole other world out there?
------------- 3430 - PHYSICS - energy and massless particles?
- In the field of physics we have waves and we have particles. Imagine the particle. What comes to mind? If you aren’t a theoretical particle physicist, chances are you picture a tiny ball, bobbing in space.
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- But that’s not quite correct. One way to prove it: Try to imagine that tiny ball as a particle with no mass. How can a particle not have mass?
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- Sometimes the word “mass” is used interchangeably with the word “weight.” That’s not entirely wrong. The mass of an object is measured by its resistance to a force. When you pick something up to test its weight, it is resisting the Earth’s gravity, so an everyday object’s weight on Earth is indeed one measurement of its mass.
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- But there’s more to mass than just a resistance to gravity, especially on the scale of the smallest pieces of matter. So physicists’ definition of mass gets a little more complicated.
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- Most fundamental matter particles, such as electrons, muons and quarks, that are present in all atoms get their mass from their resistance to a field that permeates the universe called the Higgs field. The more the Higgs field pulls on a particle, the more mass it has.
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- When it comes to composite particles like protons and neutrons, which are made up of quarks, most of their mass comes from the pull of the “strong force” that holds the quarks together.
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- Photons and gluons, two force-carrying particles, are fundamental, so they don’t host the internal tug-of-war of a composite particle. They are also unaffected by the Higgs field. Indeed, they seem to be without mass. Massless force carriers. And they always travel at the speed of light, 186,000 miles per second.
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- Massless particles are pure energy. These quanta of energy don’t have edges, and they don't have surfaces.
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- A better way to think of particles is as ripples on a “quantum field“. A quantum field has vibration modes like the harmonics on a guitar string. Pluck it with the right frequency and you get a particle.
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- The two particles physicists know to be massless—photons and gluons—are both force-carrying particles, also known as “gauge bosons“. Photons are associated with the electromagnetic force, and gluons are associated with the strong force. Tey are force carriers.
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- The graviton, a gauge boson associated with gravity, is also expected be massless, but its existence hasn’t been confirmed yet. We are still working on gravity.
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- These massless particles have some unique properties. They are completely stable, so unlike some particles, they do not lose their energy decaying into pairs of less massive particles.
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- Because all their energy is “kinetic“, they always travel at the speed of light. And thanks to special relativity, things traveling at the speed of light don't actually age. So a photon is actually not aging relative to us. It’s timeless, in that sense.
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- Gravity affects anything with energy, even a particle that has no mass at all. That’s why the gravitational attraction of objects like galaxies and clumps of dark matter curves the path of light passing by them in space. This is called “gravitational lensing“.
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- It could be that the photon and the gluon are not the only massless particles in the universe. Scientists could one day find the aforementioned “graviton“. Or it could turn out that the lightest of the three types of neutrinos has zero mass.
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- There could be a lot of massless things out there that either there’s no way to look for them, or rather we haven’t figured out how to look for them. It could be that there’s this whole other world out there.
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- There is Dark Energy and Dark Matter that makeup 95% of the mass/energy in the Universe. Everything we know and understand is a mere 5%. Hardly even the tip of an iceberg of unknowns.
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January 24, 2022 PHYSICS - energy and massless particles? 3430
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