B Particle behavior and the Doppler effect

The energy of anything is not invariant. Simply changing reference frames can result in a drastic decrease or increase in the energy of an object or wave. For example, a moving car on a highway has a lot of kinetic energy as viewed from a person standing on the side of the road, but has negligible kinetic energy viewed from another car moving alongside the first.

So then your question would become, "How can a car just change energy?" The answer to which is that part of the energy content of an object or wave is frame dependent. For massless particles like photons, all of its energy is frame dependent, whereas for objects with mass part of their energy content is locked up in their mass and thus forms a 'minimum' energy level that the object can never fall under.

 

In general, you need collections of large numbers of particles to exhibit wave properties.

There is no change in any one photon's energy. Some are observed to have a high energy and some a low energy, but that difference is due to the observer's relative motion.

 

No, we just choose to use the Earth as the de facto frame of reference when referring to speed and velocity for most of our everyday lives because it is convenient. However the truth is that in our own frame of reference we simply aren't moving and have no kinetic energy. This is a fundamental principle of physics.

Sure you are. You're asking how a car changes energy because you're asking how a photon changes energy and the two phenomena follow many of the same laws of physics.

The idea that photons have one specific energy is only applicable if you choose to measure from a single frame of reference. If you switch to another the photons may not have the same energy. To put it simply, they don't have a specific energy in general. Energy is conserved, but it is not frame-invariant.

 

You haven't given an example of a photon changing its energy!

Observers can measure the energy of light. Is it hard for you to accept the notion that the energy observed depends on the motion of the observer relative to the source? One observes a beam of light to be blue while another observes it to be red. The light never changed from blue to red, the only thing that changed is the observer's motion relative to the source.

 

I still do not see that you have established the starting point of your entire thread here, i.e. the connection between "particle physics" and "doppler effect". Why do you think particle physics can or should "explain" (whatever that word means) the doppler effect?

Until you can do that, this is similar to asking how particle physics can explain funny.

Zz.

 

You're free to choose any one you like. There is no wrong or right choice.

Sure we do. The energy of what you observe is dependent on your motion because of the way we define energy.

The Doppler effect is something we observe. It is also something that we can explain.

 

When a massive object moves at a speed that's nearly ##c## relative to you, this is what you observe. Very very small changes in the object's speed are associated with very very large changes in the object's energy. It is possible to get so close the speed ##c## that when the energy is increased by orders of magnitude there is a negligible increase in speed.

There are people doing this every day at locations all around the world. It's an undisputed fact.

Just what is it you're trying to understand here?

 

To take for what?

It can be. There's nothing wrong with that. But since the star is moving with respect to us here on Earth, you will get different measurements for the energy of the starlight if you measure in both frames.