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Cherenkov Radiation

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Re: Cherenkov Radiation

#71

Post by chucksmash »

04rob wrote: post #68
molyss wrote: post #63

Earlier quoted context omitted.

I don't think the title is that misleading. We talk about the sonic boom as something that happens when we travel faster than the speed of sound. We don’t specify “in the same medium you’re traveling in”, and noone reasonable thinks “it’s really hard to travel faster than the sound in carbon”. You’ve added “speed of light” in your reading and concluded that’s what the OP wanted to imply. I think that was unfair, and…

One difference is sound can only travel through a medium, so that bit is always implied. Not so with light.

Nothing can travel faster than light through vacuum, so that bit is implied as well.

I disagree with their quibble about the title being intentionally misleading but, meh, I've picked stranger technically correct hills to die on, the rest of their comment is interesting, it's fine.

Re: Cherenkov Radiation

#72

Post by toolsmax »

rbanffy wrote: post #67

A general rule of thumb is that if something is glowing blue or has a blue halo around it, you should run in the opposite direction. Unless you saw it from really close, in which case it's too late and you should probably relax, sit down, have a drink, call your loved ones...

In that case, I'm afraid your phone possibly won't function

Re: Cherenkov Radiation

#73

Post by delecti »

rbanffy wrote: post #67

A general rule of thumb is that if something is glowing blue or has a blue halo around it, you should run in the opposite direction. Unless you saw it from really close, in which case it's too late and you should probably relax, sit down, have a drink, call your loved ones...

Or unless it's in water, in which case you're actually probably fine.

Re: Cherenkov Radiation

#74

Post by xattt »

rbanffy wrote: post #67

A general rule of thumb is that if something is glowing blue or has a blue halo around it, you should run in the opposite direction. Unless you saw it from really close, in which case it's too late and you should probably relax, sit down, have a drink, call your loved ones...

Short of LINAC irradiator ride-through videos on YouTube, are there any photos of this effect in air from a point source?

Re: Cherenkov Radiation

#75

Post by a022311 »

nuccy wrote: post #3

The title (likely intentionally) is misleading, it should say "travelling faster than light in a medium". Nothing here travels faster than light in vacuum. BTW there are special types of telescopes used to observe gamma rays - they cannot see gamma ray directly but observe a flash of Cherenkov light of a cascade of charged particles created when gamma ray hits atoms in the atmosphere. Those telescopes are Imaging Atm…

It's funny because I was reading about Cherenkov radiation just yesterday and the same statement was made (although with a proper clarification afterwards).

Re: Cherenkov Radiation

#76

Post by loopies »

post-it wrote: post #55
bit_rot73 wrote: post #42

Light still propagates at c inside a medium; the apparent slowdown is just phase kickback from re-emission.

We know light is not being absorbed and re-emitted, because re-emission sends light in a random direction.

That is interesting. But then what is the explanation? Medium is not really anything concrete, we call that a collection of atoms isn't it? By default there is only one medium, the vacuum of space, in which there can be various densities of "stuff", particles/atoms/molecules. So then, it becomes some sort of quantum thing, a probability of photons bumping/being captured/emitted or?

Re: Cherenkov Radiation

#77

Post by lazide »

xattt wrote: post #74
rbanffy wrote: post #67

A general rule of thumb is that if something is glowing blue or has a blue halo around it, you should run in the opposite direction. Unless you saw it from really close, in which case it's too late and you should probably relax, sit down, have a drink, call your loved ones...

Short of LINAC irradiator ride-through videos on YouTube, are there any photos of this effect in air from a point source?

All the ones I see are reactors through water shielding, in which case you’d be fine.

If you see a noticeable cherenkov effect from something that close that wasn’t heavily shielded by something like water, your camera sensor will likely be destroyed and you’d be dead pretty soon.

Re: Cherenkov Radiation

#78

Post by aftbit »

nuccy wrote: post #3

The title (likely intentionally) is misleading, it should say "travelling faster than light in a medium". Nothing here travels faster than light in vacuum. BTW there are special types of telescopes used to observe gamma rays - they cannot see gamma ray directly but observe a flash of Cherenkov light of a cascade of charged particles created when gamma ray hits atoms in the atmosphere. Those telescopes are Imaging Atm…

-1 for Pedantic, but +1 for cool links to telescopes

Re: Cherenkov Radiation

#79

Post by GlobalFrog »

Several comments here mention that nothings goes faster than light in a vacuum, which is right. But... Putting aside all considerations of causality, if a particle was to go faster than light, it would also emit a vacuum Cherenkov radiation, as this particle would go faster than light. That would be a kind of supersonic bang. Some theories about this say that when a particle going faster than light, it loses its energy and emits photons. IANAP (yes, I am not a physicist), but I would love to hear a theory about how those FTL particles could be detected if they were to exist, and what could be the observation, probably coming the this vacuum Cherenkov effect. Again, I know this is against all physics, but the theory would be cool!

Re: Cherenkov Radiation

#80

Post by voxleone »

nuccy wrote: post #3

The title (likely intentionally) is misleading, it should say "travelling faster than light in a medium". Nothing here travels faster than light in vacuum. BTW there are special types of telescopes used to observe gamma rays - they cannot see gamma ray directly but observe a flash of Cherenkov light of a cascade of charged particles created when gamma ray hits atoms in the atmosphere. Those telescopes are Imaging Atm…

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