Physical representation of direction

In summary, the conversation explores the concept of how particles remember and store information about their direction of movement. The momentum vector is the mathematical representation of direction, but the physical representation is still a mystery. In classical mechanics, particles simply move in the direction they are pushed due to Newton's first law. In quantum mechanics, particles do not have a fixed direction and can travel in multiple directions at the same time. The idea of "inertial reflection" or changing direction without changing magnitude is not possible according to the conservation of momentum.
  • #1
ealbers
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Please forgive such a simple question, but how does a particle 'remember' what direction to travel in from instant to instant?

I mean, say we take 2 particles way out in space, we kick one say along a +x axis, and the other with the same force along the -x axis...

How is the Direction information physically represented in each particle, I mean, we give each the same energy, only difference is the vector, where is that direction vector physically stored from moment to moment?

Thanks, apologies again for the basic question.

Eric
 
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  • #2
It's the momentum vector, which in the absence of forces is a constant.
 
  • #3
Yes, the momentum vector is the mathematical representation of the direction, my question is, what is PHYSICALLY different between the two particles? How is that mathematical vector represented?
My guess is some kind of spacetime curvature storing the vector info??
From each particles perspective, it can be viewed as 'stationary' and the other 'moving'...but having both particles have this view does not represent the manner in which the direction of motion is 'stored' by the universe...and stored it must be, for from moment to moment forever (without outside forces), the particles will continue on their path...so perhaps when you impart motion to one, it somehow stores its direction vector into the curvature of space around it? i.e. energy given (and vector direction) is stored into a 'field' or 'virtual direction particle' around the moving particle??

I know it seems a senseless question at first...and perhaps that's more due to the senselessness of the person asking the question :-)

Thanks
Eric
 
  • #4
Well the simple answer is the two particles are different because one is moving one way and one is moving the other. There is no 'knowing' or 'storing' of information in the universe. If you push it one way it goes that way because (simply) Newton's first law.
 
  • #5
There appears to be a void of how 'particles' move, esp, in vacuum. I don't think anyone can explain how this technically happens. The deep nature of motion is a mystery but if you use Newton's laws and/or the equations of SR(say in the LHC), you'd be able to predict their behavior.
 
  • #6
This comes from right out of nowhere, so it may be total nonsense:

With reading your mention of a curve I thought that perhaps you might be thinking of a General Relativity formula for the path of a massive object in a gravitational field (does GR cover that?), but solved with a value of zero for the gravitational field. Sounds like taking a long way to get back to Newtonian as mentioned above.

Perhaps your question is "What causes inertia?"

DC
 
  • #7
The picture of 2 particles moving in opposite directions on the x-axis is more classical that QM.

In QM, there is no knowing of info from "moment to moment". If, at one time, you measure the momentum of the above 2 particles precisely then their position (along the x-axis) is completely unknown, i.e. they do not "know" where they are.

Also, for individual particles traveling freely, you get wave packet spreading. So, in a sense, they are traveling in many directions at the same time.

If you want to also consider Feynman's Path Integral Formulation of QM, in the absence of other info, particles travel all possible paths between 2 (space-time) points. An equivalent statement is that the particles don't "know" what direction their traveling in.
 
  • #8
Sorry for the strange question, I was curious if the direction information could be modified without the magnitude being effected...so the vector 1,0,0 could somehow be reflected to be -1,0,0 without the magnitude of the motion being effected. Understanding how direction is stored would give some insight into the ability to do 'inertial reflection'

If we ever want to really travel in space, we need some way to change the direction of incoming particles without having to absorb and re-emit their energy, finding a 'cheap' way to modify the direction vector alone would do this, though the how is tied to the how direction being represented...

Thanks
Eric
 
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  • #9
Science doesn't work like that. The magnitude of two equal and opposite vectors is the same, but that's purely a mathematical similarity, the two vectors are completely different. This 'inertial reflection' you speak of simply isn't possible.
 
  • #10
ealbers said:
Sorry for the strange question, I was curious if the direction information could be modified without the magnitude being effected...so the vector 1,0,0 could somehow be reflected to be -1,0,0 without the magnitude of the motion being effected. Understanding how direction is stored would give some insight into the ability to do 'inertial reflection'

If we ever want to really travel in space, we need some way to change the direction of incoming particles without having to absorb and re-emit their energy, finding a 'cheap' way to modify the direction vector alone would do this, though the how is tied to the how direction being represented...

Thanks
Eric

You can't get away from the conservation of momentum, it is built into the homogeniety of space. Anything that moves and has energy has momentum. Change in direction = change in momentum. There is no "cheap" way to change the direction of an incoming particle. The "cost" is always equal to the net change in momentum (direction and magnitude).
 

1. What is physical representation of direction?

The physical representation of direction refers to the ways in which we perceive and understand the direction of objects or movements in space. This can include visual cues, such as arrows or maps, as well as physical sensations like balance or proprioception.

2. How do our brains process direction?

Our brains process direction through a combination of sensory information and cognitive processes. This includes visual and auditory cues, as well as our internal sense of balance and proprioception. The information is then integrated and interpreted by the brain to give us a sense of direction.

3. Can direction be represented differently in different cultures?

Yes, direction can be represented differently in different cultures. For example, some cultures may use cardinal directions (north, south, east, west) while others may use relative directions (left, right, front, back). Additionally, cultural perceptions and interpretations of direction may vary based on social and environmental factors.

4. How does the physical representation of direction affect our daily lives?

The physical representation of direction plays a crucial role in our daily lives. It helps us navigate our surroundings, understand maps and directions, and perform tasks that require spatial awareness. It also influences our sense of balance and coordination, and can impact our perception of time and space.

5. Are there any limitations to our understanding of direction through physical representation?

While physical representation of direction can be highly effective, it does have some limitations. For example, some individuals may have difficulties with spatial awareness and interpreting visual cues, making it more challenging for them to understand direction. Additionally, physical representation may not always accurately reflect the complexities of directional concepts, such as time or abstract concepts.

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