Feynman & Time: Exploring the Physics of Perception

In summary, according to Feynman, the path integral method is a way of calculating a result of a process without actually seeing the process. It's based on the principle of least action, which is a classical mechanics principle that underlies the Lagrangian/Hamiltonian approach to classical mechanics.
  • #1
prj45
17
0
Can I run something by you all please?

Feynman asks us to believe that calculating where a photon goes involves us suspending our perception of nature, and that only by working out every path it could take are we able to actually work out where it will end up.

We're also told that time slows down the faster things go, so photons traveling near the speed of light experience no time.

Is this why we have to consider every possible path a photon travels to work out where it ends up? Is it because it's got all the time in the universe, and actually does go everywhere, interfering with itself in the world as we perceive it?
 
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  • #2
The path integral method of Feynman is not connected to the time dilation of special relativity. In fact when Feynman first published his method, it "didn't do" relativity; it applied to non-relativistic quantum mechanics. It was a German physicist, Wick, who showed how to use a mathematical device (replacing t by [tex] i\tau [/tex] plus analytic continuation), to make Feynmann's integrations converge in relativistic spacetime.
 
  • #3
prj45 said:
... time slows down the faster things go, so photons traveling near the speed of light experience no time.

Is this why we have to consider every possible path a photon travels to work out where it ends up?
I suspect not. It is my understanding that the photon actually takes all possible paths due to uncertainty. First, we need to decide what we're talking about when we say "photon." If this is an amount of propagated electromagnetic energy, then what is the spread we allow? If we require that the energy is at a definite value, then we arrive at a definite magnitude for momentum. This leads to quite an uncertainty in position. I don't know all that much about it, though.
 
  • #4
you cannot say or know anything about a photon in between the time it is emitted and the time it is absorbed. it is a crazy world.
 
  • #5
selfAdjoint said:
The path integral method of Feynman is not connected to the time dilation of special relativity. In fact when Feynman first published his method, it "didn't do" relativity; it applied to non-relativistic quantum mechanics.
Yup!The Feynman method is excellent for calculation of the result of processes.That was trully example of a quantum physicist's work motto "shut up and calculate!". But if one starts think about details and what happens underneath ,nasty question arrive to his mind.
time-emit-time-emit/emit-time-time-emit/emittime/
This is a little english word palindrom game appropriate to introduce when thinking over Feynman method (read backwards) :smile:
 
  • #6
What if the photon physically splits into smaller photons which really do take all the Feynman paths simulataneously?
 
  • #7
I think that the one thing that is missing in this discussion about Feynman's path integral method is that this technique has very strong underpinnings based on the CLASSICAL mechanics principle of least action. The Lagrangian/Hamiltonian approach to classical mechanics came logically out of this principle. Unless one spend time to understand that first, then Feynman's path integral method may appear odd or as if it came out of nowhere.

http://www.eftaylor.com/pub/FmaAJPguest5.pdf

Zz.
 
  • #8
Huygen's principle in fact, was said to be its inspiration.
 
  • #9
selfAdjoint said:
Huygen's principle in fact, was said to be its inspiration.

Actually, the "action" in least action principle can have several meanings. It depends on what quantity in a particular problem that you want to "minimize". In Huygen's and Fermat's least time, it is the time quantity that you want to find the stationary solutions for. Thus, the principle of least action when applied to optics now becomes the principle of least time. This then gives you the classical trajectory of light paths across various index of refraction materials.

Zz.
 
  • #10
kurious said:
What if the photon physically splits into smaller photons which really do take all the Feynman paths simulataneously?

Don't think it needs to do that. If it travels at the speed of light through space, but the speed of zero through time then it could go on every path; it's got all the time in the universe to do so. ... ?
 

FAQ: Feynman & Time: Exploring the Physics of Perception

How did Richard Feynman contribute to our understanding of time and perception?

Richard Feynman was a renowned physicist who made significant contributions to our understanding of time and perception. He developed the theory of quantum electrodynamics, which explains the behavior of particles at the atomic level. In addition, he also proposed the concept of Feynman diagrams, which are visual representations of particle interactions and helped to simplify complex equations in quantum mechanics. His work laid the foundation for our modern understanding of time and perception.

What is the connection between time and perception?

Time and perception are closely connected as our perception of time is influenced by our senses, emotions, and external stimuli. Our perception of time can vary depending on the situation, such as when we are having fun time appears to pass quickly, but when we are bored, it seems to drag on. Similarly, our perception of time can be distorted by factors such as adrenaline, stress, and memory. Understanding the physics behind time and perception can help us better understand our subjective experience of time.

How does quantum mechanics play a role in our perception of time?

Quantum mechanics is the branch of physics that deals with the behavior of particles at the atomic and subatomic level. It has shown that time is not a constant and can be influenced by factors such as gravity and speed. Additionally, quantum mechanics has revealed that particles can exist in multiple states at the same time, challenging our traditional understanding of cause and effect. This has implications for our perception of time, as it suggests that future events can influence the present moment.

Can we control our perception of time?

While our perception of time is largely influenced by external factors, there are ways we can control and manipulate it. Studies have shown that activities such as meditation, mindfulness, and engaging in new experiences can alter our perception of time. Additionally, learning to manage stress and emotions can help us feel more in control of our time and reduce the feeling of time passing too quickly or too slowly.

How does the study of time and perception impact our daily lives?

The study of time and perception has numerous implications for our daily lives. It helps us understand why time seems to fly by when we are having fun and drag on when we are bored. It also sheds light on how our perception of time can be distorted by external factors and how we can control it to some extent. Additionally, research in this field has practical applications in fields such as psychology, neuroscience, and technology, leading to advancements in areas such as virtual reality, human-computer interaction, and cognitive therapies.

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