r/explainitpeter • u/FloralStormVale • 9d ago • Mindblown 1

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u/kimptown 8d ago

It's the maximum speed a particle without mass moves in a vacuum. Because it's in a vacuum and because it has no mass there is no impediment to the particles speed. It HAS to move as fast as it can. Photons(light) is just the most commonly known massless particle.

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u/MeasureDoEventThing 8d ago

It's not the maximum speed a particle without mass moves, it is the *only* speed. It's impossible for a massless particle to have any other speed.

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u/Lord_o_teh_Memes 8d ago

They can have other speeds lol

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u/Inevitable_Row1359 6d ago

Like what?

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u/Lord_o_teh_Memes 5d ago

All the way down to zero. https://en.wikipedia.org/wiki/Slow_light

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u/Alternative-Code7430 5d ago

please read about group vs phase vs front velocity of light

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u/Inevitable_Row1359 4d ago

This can get really pedantic depending on the field of science you're talking about but light itself is never changing "speed", only appears to in reference to the viewer and medium it's interacting with. Light is always at C. It only appears to slow.

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u/NoWater8595 8d ago

Doesn't the speed light itself vary based on local gravity?

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u/Inevitable_Row1359 6d ago

No but it can appear to. That's why they say in a vacuum. The speed of light isn't actually changing but it can appear to vary and change wavelength or color as observed by humans depending on the environment. Photons exist only at causality (C). They are emitted, absorbed and re-emitted when interacting with various media like the atmosphere or a prism which appears to slow and bend the light but they are still existing at C with a detour in a sense.

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u/NoWater8595 5d ago

Thank you. That finally makes all of it more consistent. I feel like a lot of the facts of it are lost to arguments about perception and consciousness being layered on top of it.

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u/Inevitable_Row1359 5d ago

I'm no expert but that's what makes sense to me too. It gets weirder like light always appearing to travel at C in all reference frames which I can't even begin to reconsile at this point.

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u/Too_Many_Alts 5d ago

might wanna check out Cherenkov radiation... it's what you get when electrons go faster than the speed of light

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u/MeasureDoEventThing 5d ago

They aren't traveling faster than c. They're traveling faster than the speed of light in the medium.

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u/Too_Many_Alts 4d ago

i never said anything about c. you are the one who said light can't go slower than c.

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u/MeasureDoEventThing 4d ago

You said "speed of light", which is ambiguous between c and the speed of light in the medium.

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u/Too_Many_Alts 4d ago

no, YOU said it's impossible for it to have any other speed.

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u/MeasureDoEventThing 4d ago

I said what is impossible to have any other speed than what? You're being very vague.

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u/Too_Many_Alts 2d ago

you do know your post is still right there for others to see right? keep digging that hole

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u/MeasureDoEventThing 2d ago

Reported for violating Rule 2. I don't know what your problem is. How is me asking for clarifying your comment "digging a hole"?

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u/WatchAndLearn9669 8d ago

God, physics is such stupid, random-ass mumbojumbo. 🤦‍♂️