Shortest distance you can travel?

[AtomicJoe]

Another example, you eliminate some matter on earth, does the moons orbit change?

Of course you can eliminate a small amount such it will not move a plank length, and keep going until the earth
is eliminated!

 

[mishrashubham]

I think you have to consider the centre of gravity and say applying a small force to large object. I mean like you apply a small force to a large object, if you apply half the force it will move half the distance. You can repeatedly halve the force.

You didn't get the point. Atoms are constanly moving distances many orders of magnitude greater than Planck length naturally. You applying a force does not change anything.

Another example, you eliminate some matter on earth, does the moons orbit change?

Of course you can eliminate a small amount such it will not move a plank length, and keep going until the earth
is eliminated!

The Law of conservation of mass does not allow that. You simply cannot eliminate matter.

 

[bp_psy]

I mean like you apply a small force to a large object, if you apply half the force it will move half the distance. You can repeatedly halve the force.

No.You don't understand what a force is. If you apply a force F on an object of mass m it will accelerate with a=F/m.If you apply F/5 then it will accelerate with a=F/5m.You can't say absolutely nothing about how much it will move. Also you can't physically halve a a force indefinitely the electromagnetic force depends on charge and distance between the charges.Charge is quantized it only comes in integer multiples of 1.60217×10^(−19) Coulombs.Distance between particles also can't be reduced indefinitely for obvious reasons so you certainly can't halve your force indefinitely.The same is true for the other forces but EM is pretty much the only force that counts in this case .

Read this very very carefully before continuing :
http://en.wikipedia.org/wiki/Newton's_laws_of_motion

 

[AtomicJoe]

You didn't get the point. Atoms are constanly moving distances many orders of magnitude greater than Planck length naturally. You applying a force does not change anything.



The Law of conservation of mass does not allow that. You simply cannot eliminate matter.

As I said you take the centre of gravity which is fixed.

Matter is eliminated in nuclear reactions, as you eliminate it the moons orbit will change.

If you eliminate it in chunks small enough to not move it a plank length then effectively you could eliminate the entire planet and the moon would orbit nothing.

 

[AtomicJoe]

No.You don't understand what a force is. If you apply a force F on an object of mass m it will accelerate with a=F/m.If you apply F/5 then it will accelerate with a=F/5m.You can't say absolutely nothing about how much it will move. Also you can't physically halve a a force indefinitely the electromagnetic force depends on charge and distance between the charges.Charge is quantized it only comes in integer multiples of 1.60217×10^(−19) Coulombs.Distance between particles also can't be reduced indefinitely for obvious reasons so you certainly can't halve your force indefinitely.The same is true for the other forces but EM is pretty much the only force that counts in this case .

Read this very very carefully before continuing :
http://en.wikipedia.org/wiki/Newton's_laws_of_motion

You don't have to half the force indefinitely you only have to keep halving until you move something less than a plank length, so your point is mute and I don't need to read your link
as I understand the content.

 

[mishrashubham]

As I said you take the centre of gravity which is fixed.

What do you mean by "taking" the centre of gravity? Let me get this straight once again; You cannot apply things such as centre of gravity to atoms or subatomic particles. Those apply to macroscopic objects. Anyways gravity has little if not no effect on interactions at the atomic scale.

Matter is eliminated in nuclear reactions, as you eliminate it the moons orbit will change.

If you eliminate it in chunks small enough to not move it a plank length then effectively you could eliminate the entire planet and the moon would orbit nothing.

You must even know then that thousands of tonnes of dust from outer space also falls on earth. Even that is not enough to significantly change the orbit of the moon. Anyways I did not understand the bit about eliminating the planet.

 

[AtomicJoe]

What do you mean by "taking" the centre of gravity? Let me get this straight once again; You cannot apply things such as centre of gravity to atoms or subatomic particles. Those apply to macroscopic objects. Anyways gravity has little if not no effect on interactions at the atomic scale.



You must even know then that thousands of tonnes of dust from outer space also falls on earth. Even that is not enough to significantly change the orbit of the moon. Anyways I did not understand the bit about eliminating the planet.

Every particle has a statistical centre of gravity.
How do you know dust does not change the moon?

Mass is converted into energy in nuclear reactions so in theory you could change the mass of the Earth to make it lighter and hence change the moons orbit.

Thus you have a small force change on a huge object which could move it less than a plank distance.

If you disagree with that then I can continue eliminating mass until the Earth is effectively eliminated and you have to argue what is stays in the same orbit with no gravity holding it in that orbit, which is clearly a ridiculous argument.

 

[AstrophysicsX]

Matter isn't eliminated in nuclear reactions. It's just converted to a huge amount of energy. As stated above, Lol.

 

[bp_psy]

You don't have to half the force indefinitely you only have to keep halving until you move something less than a plank length, so your point is mute and I don't need to read your link
as I understand the content.

Well you certainly do not understand what a force is and you stubbornly refuse to actually figure out such a basic concept so there is no point in wasting more time with you.

 

[raul_l]

If you think about the wave function and what it represents I think it's pretty clear that the notion of distance becomes meaningless at such short distances. As was already mentioned, very small movements simply don't exist.
If you still want to ask the question of shortest distances you would need to forget about quantum mechanics for a moment, assume classical mechanics works all the way down to the Planck scale and then analyze the situation. Then you might arrive at some answer, but it would only be valid in some fictional Universe with completely different laws of physics and so the original question would not be interesting anymore.
Another method would be to do a statistical analysis. Take a huge number of particles and subject half of them to a very small force. Then use some very precise interferometry method for example to see if the average distance between the two bunches of particles has changed by a Planck distance or not. But such method would first of all be impossible with current technology and secondly would only be able to give an indirect answer (at best) to your question.

 

[Pengwuino]

Unfortunately I lost track of this thread but it looks like a theme is apparently coming to light. You have to stop thinking about the quantum world in terms of classical physics and "the everyday world". You can't just say "Well, assume *classical idea*, can't I do *classical action* and deduce something at the quantum scale?". It's like saying that if you have a macroscopic electric field that you can cut in half by reducing the charge, why can't you get a photon and cut it in half?

 

[mishrashubham]

Unfortunately I lost track of this thread but it looks like a theme is apparently coming to light. You have to stop thinking about the quantum world in terms of classical physics and "the everyday world". You can't just say "Well, assume *classical idea*, can't I do *classical action* and deduce something at the quantum scale?". It's like saying that if you have a macroscopic electric field that you can cut in half by reducing the charge, why can't you get a photon and cut it in half?

Precisely

 

[AtomicJoe]

Matter isn't eliminated in nuclear reactions. It's just converted to a huge amount of energy. As stated above, Lol.

Well that is playing with words, matter is eliminate and converted into energy, the matter no monger exists as matter, with the properties of matter, ie gravity.

 

[AtomicJoe]

Well you certainly do not understand what a force is and you stubbornly refuse to actually figure out such a basic concept so there is no point in wasting more time with you.

I'm fine with that, well the last part of it.

 

[AtomicJoe]

Unfortunately I lost track of this thread but it looks like a theme is apparently coming to light. You have to stop thinking about the quantum world in terms of classical physics and "the everyday world". You can't just say "Well, assume *classical idea*, can't I do *classical action* and deduce something at the quantum scale?". It's like saying that if you have a macroscopic electric field that you can cut in half by reducing the charge, why can't you get a photon and cut it in half?

The way I described it the only thing which has to be cut in half is the distance. this done by apply in a relatively small force to a large object.

I am making the point that if you repeatedly apply the force the object must move eventually because you end up applying a very big force in total eventually. Hence I ask what happens when you apply the smaller force which is not great enough to move the object a plank distance. I maintain that the object must move in steps of less than one plank distance.

 

[AstrophysicsX]

I understand what you're trying to describe. On the macroscopic scale, physics is completely different than on the microscopic scale. Planck Length is actually the one point where quantum mechanics takes over and classical physics is cut out of the picture. And since Planck Lengthis still a topic in theoretical physics, it's pretty hard to deduce what would happen at such a small scale.

 

[AtomicJoe]

I understand what you're trying to describe. On the macroscopic scale, physics is completely different than on the microscopic scale. Planck Length is actually the one point where quantum mechanics takes over and classical physics is cut out of the picture. And since Planck Lengthis still a topic in theoretical physics, it's pretty hard to deduce what would happen at such a small scale.

I know they are different on the macroscopic and macroscopic scale, well...I also know they are the same, it is just man's careless lackadaisical approach which makes him think things are different.

All macroscopic events are just a huge number of microscopic events.

It seems to me it moves a distance smaller than the plank length but we just can't detect it.
I don't really see what else it could be.

 

[AstrophysicsX]

That's the beauty of theoretical physics. There is absolutely no way to prove that you're right. You could be right, but you could also be wrong. So it's pointless to argue about things that can't be experimented.

 

[AtomicJoe]

Well if I am wrong them it seems perhaps that things have the ability to remember forces applied to them in the past and then make a response 5 time the value of the currently applied force.

 

[mishrashubham]

I also know they are the same, it is just man's careless lackadaisical approach which makes him think things are different.

Correction; it is man's practical approach.

All macroscopic events are just a huge number of microscopic events.

Agreed. But think it this way. If I am suppose a person who simply wants to calculate the trajectory of a thrown ball or the speed of the ball when it hits the bat; can I go and consider every single particle that makes the ball, try to understand and calculate the complex interactions between the atoms and molecules and then pass my result? It is far easier to understand the behaviour of a system of particles as it exists as a whole, not the individual particles inside them.

Apart from that, a single particle does not show the properties of a bulk system because macroscopic properties arise due to particle-particle interaction. A single particle cannot interact with anything and hence does not show macroscopic behaviour.

You cannot say that if I go down to the atomic scale and squash a gold atom it will flatten because, don't we know that gold is very malleable.

 

[AtomicJoe]

Correction; it is man's practical approach.



Agreed. But think it this way. If I am suppose a person who simply wants to calculate the trajectory of a thrown ball or the speed of the ball when it hits the bat; can I go and consider every single particle that makes the ball, try to understand and calculate the complex interactions between the atoms and molecules and then pass my result? It is far easier to understand the behaviour of a system of particles as it exists as a whole, not the individual particles inside them.

Apart from that, a single particle does not show the properties of a bulk system because macroscopic properties arise due to particle-particle interaction. A single particle cannot interact with anything and hence does not show macroscopic behaviour.

You cannot say that if I go down to the atomic scale and squash a gold atom it will flatten because, don't we know that gold is very malleable.

Well whilst I agree with all of that I don't see it as an argument against mine.
I just maintain there are movements we cannot measure, but that does not mean there was no movement.

 

[mishrashubham]

I just maintain there are movements we cannot measure, but that does not mean there was no movement.

I agree with that too. But the movements that you are specifically referring to (about the moon's orbit and stuff) are not simply theoretical predictable using F=ma. What I am saying is that F=ma does not apply to things that are very very small (subatomic scale) and hence cannot be used to justify statements such as yours (about things moving half a Planck length etc).

I do not deny that a thing can move half a Planck length (though we still need to ask the experts). It is just that thought experiments should be formulated taking appropriate things into consideration.

 

[Gabe21]

so if we can't put a limit on the size of the universe and it is accepted that space is infinitive in size then y can't space also be infinitely small? there is a limit on how far we can see into space so y don't we assume the same in relation to how small something is? so if the theoretical largest distance travelable is infinite y isn't the theoretical smallest distance travelable infinite also.

 

[JaredJames]

so if we can't put a limit on the size of the universe and it is accepted that space is infinitive in size then y can't space also be infinitely small?

Doesn't that contradict itself?

there is a limit on how far we can see into space so y don't we assume the same in relation to how small something is?

Surely we do. Planck length?

1. Capital letters.
2. It's 'why' not 'y'.

 

[Gabe21]

so grammatical errors aside, u r saying that smaller distances do exist but we can't see on a scale smaller than Plancks?

and its more redundant than contradictory. not being able to put a definite size on the universe means its infinite. a shorter version would be" if space is infinitely large y can't it also be infinitely small."

 

[mishrashubham]

so grammatical errors aside, u r saying...

https://www.physicsforums.com/showthread.php?t=414380

In the interest of conveying ideas as clearly as possible, posts are required to show reasonable attention to written English communication standards. This includes the use of proper grammatical structure, punctuation, capitalization, and spelling. SMS messaging shorthand, such as using "u" for "you", is not acceptable.

 

[JaredJames]

so grammatical errors aside, u r saying that smaller distances do exist but we can't see on a scale smaller than Plancks?

I don't see why distance can't be zero - but we have a limit for what we can measure.

You said:

there is a limit on how far we can see into space so y don't we assume the same in relation to how small something is?

We do. The limit on how small we can measure is the Planck length.

Note, our ability to see a certain distance does not limit the maximum size something can be, only what we can measure. The inverse with 'small' is exactly the same.

and its more redundant than contradictory.

You are either infinitely big or you have a limited size. The limit you keep referring to is purely our ability to measure (or see that far). It has nothing to do with the size of the universe.

not being able to put a definite size on the universe means its infinite.

I can't put a definite size on my car, that doesn't mean it's infinite. Again, the inability to measure does not imply an infinite size.

a shorter version would be" if space is infinitely large y can't it also be infinitely small."

No, you can only get to zero in size. That is as small as something can be (well there abouts) so unlike space which could go on infinitely, you could only tend to zero with size.

 

[physiqueper4]

since the universe is continum, then maybe no limit.
If it is descret it may be h (planck cst)
I say maybe