Exploring the Mysterious Planck Scale: The Secrets of the Smallest Unit of Space

[oquen]

It will take a particle accelerator that size of the solar system or more to peek inside the Planck scale.. does this mean the Planck scale is a no man's land.. or empty? but for a passing electromagnetic field or strong field.. doesn't it pass thru or touch the Planck scale at all?

If it doesn't.. and since space is composed of many tiny Planck scale.. how does any field exist at all since the Planck made up space? Like how can you walk in the ground but avoiding each air molecular or atoms?

 

[Drakkith]

It will take a particle accelerator that size of the solar system or more to peek inside the Planck scale.. does this mean the Planck scale is a no man's land.. or empty? but for a passing electromagnetic field or strong field.. doesn't it pass thru or touch the Planck scale at all?

Does the Earth 'touch' a meter? Not a physical meter-stick or other measuring device, but the scale itself?
No, because the meter is a unit of distance, not a physical object. Similarly, the Planck scale (or Planck length rather) is a unit of distance just like the meter.
Fields, such as the EM field, are continuous and occupy all of space. There is no distance scale where they simply stop existing. The Planck length is just a convenient unit of distance to use in certain circumstances.

If it doesn't.. and since space is composed of many tiny Planck scale..

Space is not divided into little Planck-length segments. General Relativity models space as being part of spacetime, which is represented by a smooth and continuous manifold (something which specifies the geometry of spacetime at every point). Note that when I say that space is smooth and continuous, I mean that in a mathematical sense, meaning that there are no breaks, gaps, holes, or other discontinuities in it (singularities aside). This includes sharp edges or corners like what would be found at the vertex or between two sides of a polygon.

As far as science knows, and certainly as we model it now, there is no distance at which space becomes disjointed or segmented.

 

[oquen]

Does the Earth 'touch' a meter? Not a physical meter-stick or other measuring device, but the scale itself?
No, because the meter is a unit of distance, not a physical object. Similarly, the Planck scale (or Planck length rather) is a unit of distance just like the meter.
Fields, such as the EM field, are continuous and occupy all of space. There is no distance scale where they simply stop existing. The Planck length is just a convenient unit of distance to use in certain circumstances.
Space is not divided into little Planck-length segments. General Relativity models space as being part of spacetime, which is represented by a smooth and continuous manifold (something which specifies the geometry of spacetime at every point). Note that when I say that space is smooth and continuous, I mean that in a mathematical sense, meaning that there are no breaks, gaps, holes, or other discontinuities in it (singularities aside). This includes sharp edges or corners like what would be found at the vertex or between two sides of a polygon.

As far as science knows, and certainly as we model it now, there is no distance at which space becomes disjointed or segmented.

But physicists report it takes a solar system size particular accelerator to probe the Planck scale.. if any electromagnetic field can access or probe it.. then why don't they?

 

[Drakkith]

But physicists report it takes a solar system size particular accelerator to probe the Planck scale.. if any electromagnetic field can access or probe it.. then why don't they?

What they mean is that the interaction of particles/fields with other particles/fields changes as your distance or energy scales change and they want to know how the laws of physics work at this scale. To do that, they need to smash particles together at incredibly high energies, which would require an accelerator far bigger than anything we have now.

 

[oquen]

What they mean is that the interaction of particles/fields with other particles/fields changes as your distance or energy scales change and they want to know how the laws of physics work at this scale. To do that, they need to smash particles together at incredibly high energies, which would require an accelerator far bigger than anything we have now.

so the natural electromagnetic field passing through the Planck scale can itself momentarily create positron/electron pair inside the Planck scale? I'm aware that as the length scale gets smaller.. the wavelength needs to become smaller and you can do it by very powerful energies to satisfy debroglie equation. But the natural electromagnetic field is weak yet can reach the Planck scale.. can somebody please elaborate where I may not understand it well? Thank you!

 

[Drakkith]

Fields do not have wavelengths. They exist everywhere. It is the disturbances in these fields, which manifest as waves, that have wavelengths.

 

[oquen]

Fields do not have wavelengths. They exist everywhere. It is the disturbances in these fields, which manifest as waves, that have wavelengths.

But the wavelengths part of the electromagnetic field still pass through the Planck length.. correct? So it puzzles me quite why physicists have to build solar system size accelerator to send the wavelengths into the Planck scale when natural electromagnetic field can do that? What part of the arguments escape me??

 

[rootone]

Electromagnetic wavelength which we can possibly detect with present technology ends with observation of the most energetic 'cosmic rays', or gamma ray bursts.
Nothing we can construct on Earth approaches the ability to reproduce those,
yet their wave length still is a lot longer than Planck scale.

 

[Drakkith]

But the wavelengths part of the electromagnetic field still pass through the Planck length.. correct? So it puzzles me quite why physicists have to build solar system size accelerator to send the wavelengths into the Planck scale when natural electromagnetic field can do that? What part of the arguments escape me??

Because of what I already told you. The interactions between particles and fields changes with distance and energy and we need high-energy colliders to find the way they interact at these high energy scales. For example, at extremely short distances and very high temperatures the protons and neutrons making up nuclei "decompose" and become a quark-gluon plasma. Who knows what happens at even higher energies?

 

[oquen]

Does the Earth 'touch' a meter? Not a physical meter-stick or other measuring device, but the scale itself?
No, because the meter is a unit of distance, not a physical object. Similarly, the Planck scale (or Planck length rather) is a unit of distance just like the meter.
Fields, such as the EM field, are continuous and occupy all of space. There is no distance scale where they simply stop existing. The Planck length is just a convenient unit of distance to use in certain circumstances.
Space is not divided into little Planck-length segments. General Relativity models space as being part of spacetime, which is represented by a smooth and continuous manifold (something which specifies the geometry of spacetime at every point). Note that when I say that space is smooth and continuous, I mean that in a mathematical sense, meaning that there are no breaks, gaps, holes, or other discontinuities in it (singularities aside). This includes sharp edges or corners like what would be found at the vertex or between two sides of a polygon.

As far as science knows, and certainly as we model it now, there is no distance at which space becomes disjointed or segmented.

Returning to this first reply of yours. Recall Superstring theory describes Planck scale as unknown and it may not even contain space. And just like liquid and the atoms inside it. Space can be like the liquid and there are atoms of space which may not contain space. Hence Space is indeed or can be divided into little Planck-length segments. I think you know Lee Smolin?

 

[Drakkith]

Returning to this first reply of yours. Recall Superstring theory describes Planck scale as unknown and it may not even contain space. And just like liquid and the atoms inside it. Space can be like the liquid and there are atoms of space which may not contain space. Hence Space is indeed or can be divided into little Planck-length segments. I think you know Lee Smolin?

Unlike GR, superstring theory is not a well accepted way to the universe at this time, so whatever it may say is mostly irrelevant. There are many possible theories that go beyond what GR says, but until we know which one is correct we can't take any of their predictions as fact.

 

[ChrisVer]

There are just so many misconceptions in the initial post that it's almost impossible answering anything.
Particle physics: how do we probe higher energies to search for new physics? At the moment we build accelerators, which accelerate particles to high velocities [energies] and by colliding them we can see what the products of those collisions are; we compare those to our current models and decide whether there's something new or not. Then the point is that the highest energy you can reach depends on the center-of-mass energy of the colliding particles (you can't produce more than you give)... LHC best reach would be of TeV, since the protons collide at 13 (14) TeV center-of-mass energy ... but they are not elementary particles, so the elementary particles such as quarks or gluons will have less than 13 (14)TeV energy...
What does it mean that we need an extremely large accelerator: well the more you accelerate the particles the more difficult it gets to keep bending them inside the accelerator till they reach your desired energy (you need extremely large magnets to do that)... One way to increase the energy would then be to increase the radius of the accelerator... higher radius = less bending needed to keep them inside.
If you have a photon with energy ~ 10^19 GeV , you get what is happening at the Planck scale. Otherwise it's like asking why you can't see atoms with your eyes (photon detectors at the visual energies range)...

 

[nikkkom]

It will take a particle accelerator that size of the solar system or more to peek inside the Planck scale..

It looks like you don't know _why_ a large accelerator is necessary to probe properties of interactions on very short scales.

It's simple, but not often spelled out in pop-sci: high energy corresponds to small distances.

Consider the very first discovered "quantum formula" (by Planck himself): energy of a photon = (Planck constant) * frequency. This means that more energetic photons have higher frequency. Higher frequency means that peaks of electromagnetic wave in this photon are closer together, they are not "smeared" around a large region of space. Low energy photons such as radio waves have huge peak-to-peak distances of centimeteres to meters, while high-energy gamma rays have peaks closer than atom radius. As a result, for a radio wave even a macroscopic metal mesh looks like "solid wall", while gamma rays are used for crystallography.

Low-energy particles (any particles, not only photons) all have their waves "smeared" way too much for probing really small scales particle physicists are interested in. That's why we build accelerators which give us high-energy particles.

 

[oquen]

When we are sending radio waves.. can anything in the Planck scale picks it up. The radio waves wavelength is way much larger than the Planck scale.. but note some submarines are designed to pick up ELF (Extremely Low Frequency) radio wave. So the Planck can pick it up too in principle?

In essence. The Planck can spy on us.. but we normally can't spy on the Planck because we need wavelengths that can fit inside it and this needs huge particular accelerator to create the necessary energy. Is this a correct way of saying it?

 

[nikkkom]

When we are sending radio waves.. can anything in the Planck scale picks it up. The radio waves wavelength is way much larger than the Planck scale.. but note some submarines are designed to pick up ELF (Extremely Low Frequency) radio wave.

Picking up a radio wave requires an antenna not much smaller than the wavelength. ELF transmitters are huge installations; subs need to use a very sophisticated processing to pick ELF signals up since they can't afford having multi-kilometer antennas.

Planck-scale receiver trying to detect radiowave is like amoeba trying to detect a tsunami wave by measuring pressure difference across its body.

 

[oquen]

There is a saying "do not mistake the map for the territory".. and I'm kinda confused what is the map and territory in the Planck scale.

Let's say spacetime as model is the map. And real space is the territory.
In Loop quantum gravity, it is the spacetime which is the map which has spin networks in the Planck scale. And real space is the territory. So someday if we can probe Planck scale for instance directing gamma ray burst to the target sensors. Can we see loops or strings which are located in the maps or the territory which hasn't got this? Or are the spin networks in LQG located in the territory and not the maps?

 

[ChrisVer]

So the Planck can pick it up too in principle?

planck is not a detector... it's just a unit of something (if not the physicist)...
You can't say that the meter picks up the a wavelength...

"do not mistake the map for the territory"

this saying is irrelevant...

directing gamma ray burst to the target sensors

The photons from gamma ray bursts are not so energetic as you imagine: As far as I know they can reach up to ~100TeV and those I would guess are outliers... GRBs are a natural phenomenon that doesn't occur in laboratories but in space.

Can we see loops or strings which are located in the maps or the territory which hasn't got this?

?

 

[oquen]

planck is not a detector... it's just a unit of something (if not the physicist)...
You can't say that the meter picks up the a wavelength...this saying is irrelevant...The photons from gamma ray bursts are not so energetic as you imagine: As far as I know they can reach up to ~100TeV and those I would guess are outliers... GRBs are a natural phenomenon that doesn't occur in laboratories but in space.?

Map is spacetime model which contains the spin networks or quantum fluctuations in the Planck scale.

Territory is the real space in the Planck scale which doesn't contain any spin networks.

Someday let's say we can probe the Planck scale using wavelength that can fit inside it. Would we able to detect any spin networks (or quantum fluctuations) inside it? But spin networks are located in the maps, not the territory. Or if I'm confused. What is the map and territory in the case of general relativity and quantum spacetime and Planck scales?

 

[nikkkom]

Map is spacetime model which contains the spin networks or quantum fluctuations in the Planck scale.

Territory is the real space in the Planck scale which doesn't contain any spin networks.

It is not known for sure that space "really" exists down to those tiny scales. LQG and other "geometrodynamical" theories start with the idea that "maybe space is _not_ infinitely divisible?"

Someday let's say we can probe the Planck scale using wavelength that can fit inside it. Would we able to detect any spin networks (or quantum fluctuations) inside it?

If we would be able to probe smaller scales, we would be able to detect what's happening there. That's the story of the last 100+ years of particle physics.

But spin networks are located in the maps, not the territory. Or if I'm confused.

What is this "maps and territory" analogy? Maps = theories, territory = reality?

 

[oquen]

It is not known for sure that space "really" exists down to those tiny scales. LQG and other "geometrodynamical" theories start with the idea that "maybe space is _not_ infinitely divisible?"
If we would be able to probe smaller scales, we would be able to detect what's happening there. That's the story of the last 100+ years of particle physics.
What is this "maps and territory" analogy? Maps = theories, territory = reality?

There is an expression "don't mistake the maps for the territory". I don't know how to apply it to physics models. So maps = theories, territory = reality? Is that correct, or is that your guess? And does physics models fall under the "maps=theories" or "territory=realities"? If it's the former. But right now our physics models are our realities because we don't have other realities so what is officially the maps and territory here?

 

[Drakkith]

If it's the former. But right now our physics models are our realities because we don't have other realities so what is officially the maps and territory here?

Physics models are not realities. They are just models. They help us make predictions about what will happen within the universe under a certain set of rules, assumptions, etc.

 

[oquen]

Physics models are not realities. They are just models. They help us make predictions about what will happen within the universe under a certain set of rules, assumptions, etc.

Spacetime is a physics model and not realities as you say. So spacetime is the map. But what is the territory analogy equivalent? Is it Space? Or is Spacetime both the Map and Territory. I'm quite confused about this. Thanks in advanced to those who can help.

 

[nikkkom]

Spacetime is a physics model and not realities as you say. So spacetime is the map. But what is the territory analogy equivalent? Is it Space? Or is Spacetime both the Map and Territory. I'm quite confused about this.

I'm confused why you insist that phrase "don't mistake the maps for the territory" must be applicable to particle physics in some way, and demand that we explain it to you.

 

[oquen]

I'm confused why you insist that phrase "don't mistake the maps for the territory" must be applicable to particle physics in some way, and demand that we explain it to you.

Because whenever I asked physicists whether spacetime or space was the primary. They always said "don't mistake the maps for the territory" and I didn't understand what they meant. Now pondering on LQG with its spin networks. I don't know if spin networks are the territory or the maps.

 

[ChrisVer]

The phrase "don't mistake the maps for the territory" as far as I know, is coming from a fallacy in considering that what a model describes has some reality into it... Models are mathematical constructs, they don't illustrate anything about reality- they only let you describe or predict what is happening.

 

[nikkkom]

Since quantum physics appeared, we are no longer sure what "reality" is, what is "real" and what is not.
Numerous threads about various interpretations of QFT are the proof of that.

 

[oquen]

Ok.. that's clear. Thanks.

Now back to Planck scale dynamics. We may not have instruments to probe Planck scale yet but do we have detector to detect them? For instance, it is agreed that Planck mass (mass equivalent to the energy inside a Planck scale) is the mass of a flea.. so by detecting fleas.. we know the Planck length is occupied. Also in Superstring theory, the strings fit inside the Planck length, does it mean superstrings has the mass of a flea (planck mass). But since the air we breath has oxygen and superstrings.. why don't I feel the resistance of flea in the air when I'm walking in the ground?

 

[ChrisVer]

Again I am going to say that the Planck quantities are just convenient units for when you deal with particle physics at those energy scales.
Strings don't necessarily fit in that length - it is the natural length to measure things at that regime, as the natural length to measure distances in nuclear physics is the femtometers.
No strings don't need to have mass=planck mass.
Since you are bombarded by billions of particles from the outerspace, why don't you get crushed? Don't try to bring macroscopic world in here- when you speak for Planck mass for example you are considering a single particle with that mass not any big structure such as atoms or molecules...

 

[nikkkom]

Ok.. that's clear. Thanks.

Now back to Planck scale dynamics. We may not have instruments to probe Planck scale yet but do we have detector to detect them? For instance, it is agreed that Planck mass (mass equivalent to the energy inside a Planck scale) is the mass of a flea.. so by detecting fleas.. we know the Planck length is occupied.

"by detecting fleas.. we know theplanck length is occupied"? This is some weapon-grade nonsense.

 

[oquen]

Again I am going to say that the Planck quantities are just convenient units for when you deal with particle physics at those energy scales.
Strings don't necessarily fit in that length - it is the natural length to measure things at that regime, as the natural length to measure distances in nuclear physics is the femtometers.
No strings don't need to have mass=planck mass.
Since you are bombarded by billions of particles from the outerspace, why don't you get crushed? Don't try to bring macroscopic world in here- when you speak for Planck mass for example you are considering a single particle with that mass not any big structure such as atoms or molecules...

To clarify:
https://en.wikipedia.org/wiki/Planck_mass
"In physics, the Planck mass, denoted by mP, is the unit of mass in the system of natural units known as Planck units. It is approximately 0.0217651 milligrams—about the mass of a flea egg."
"The Planck mass can be derived approximately by setting it as the mass whose Compton wavelength and Schwarzschild radius are equal.[3] The Compton wavelength is, loosely speaking, the length-scale where quantum effects start to become important for a particle; the heavier the particle, the smaller the Compton wavelength. The Schwarzschild radius is the radius in which a mass, if it were a black hole, would have its event horizon located; the heavier the particle, the larger the Schwarzschild radius. If a particle were massive enough that its Compton wavelength and Schwarzschild radius were approximately equal, its dynamics would be strongly affected by quantum gravity."

It's saying if the Planck length is occupied by energy, it's like the mass of a flea egg. What detector do we have that measure it and distinguish if it's a real flea egg or a Planck length energy??

But the flea mass is not the maximum that can fit inside the Planck length, correct? because in the big bang.. all the universe was once the size of a Planck length.. so I figure the mass can be higher. Back to the flea egg. If our detector can detect the mass of a flea egg in the accelerator sensor, then it means we can measure the Planck length? or no way to know if the flee egg is a real egg or mass from the Planck length?

 

[nikkkom]

To clarify:
https://en.wikipedia.org/wiki/Planck_mass
"In physics, the Planck mass, denoted by mP, is the unit of mass in the system of natural units known as Planck units. It is approximately 0.0217651 milligrams—about the mass of a flea egg."
"The Planck mass can be derived approximately by setting it as the mass whose Compton wavelength and Schwarzschild radius are equal.[3] The Compton wavelength is, loosely speaking, the length-scale where quantum effects start to become important for a particle; the heavier the particle, the smaller the Compton wavelength. The Schwarzschild radius is the radius in which a mass, if it were a black hole, would have its event horizon located; the heavier the particle, the larger the Schwarzschild radius. If a particle were massive enough that its Compton wavelength and Schwarzschild radius were approximately equal, its dynamics would be strongly affected by quantum gravity."

It's saying if the Planck length is occupied by energy, it's like the mass of a flea egg.

No. You are reading it wrong.

It's saying that if you take some particle (say, an electron) and accelerate it so much that its wavefunction can be localized to fit entirely in just one Planck length, the necessary energy for such acceleration is equivalent to a mass of a flea egg. Which is an enormous energy for an electron. We are very far from being able to give electrons (or any other particles) that much energy.

 

[ChrisVer]

But the flea mass is not the maximum that can fit inside the Planck length, correct? because in the big bang.. all the universe was once the size of a Planck length.. so I figure the mass can be higher. Back to the flea egg. If our detector can detect the mass of a flea egg in the accelerator sensor, then it means we can measure the Planck length? or no way to know if the flee egg is a real egg or mass from the Planck length?

The movement of your fingers while you typed this message produced several orders of magnitude more energy than the Planck mass. However they are interactions happening on a lot of particles (well atoms) and not on single particles (as eg an electron).
The string mass can be lower as well...

 

[oquen]

No. You are reading it wrong.

It's saying that if you take some particle (say, an electron) and accelerate it so much that its wavefunction can be localized to fit entirely in just one Planck length, the necessary energy for such acceleration is equivalent to a mass of a flea egg. Which is an enormous energy for an electron. We are very far from being able to give electrons (or any other particles) that much energy.

But if someday we could accelerate particles and collide them and acquire enough energy to focus them in the Planck length with energy equal to the Planck mass.. ain't the effect the same as accelerating the electron itself to make its wavefunction be localized to fit entirely in just one Planck length??

At present.. what is the resolution of our sensor that we can distinguish whether the particles are blob or distinguish shape? is this entirely related to how much we can localize or make the wavelength smaller (by high energy) or is there other way?

 

[nikkkom]

But if someday we could accelerate particles and collide them and acquire enough energy to focus them in the Planck length with energy equal to the Planck mass.. ain't the effect the same as accelerating the electron itself to make its wavefunction be localized to fit entirely in just one Planck length??

I will try one last time. There is only ONE method to "focus particles into" very small spaces - to accelerate them.

At present.. what is the resolution of our sensor that we can distinguish whether the particles are blob or distinguish shape? is this entirely related to how much we can localize or make the wavelength smaller (by high energy) or is there other way?

There is no other way.

 

[oquen]

I will try one last time. There is only ONE method to "focus particles into" very small spaces - to accelerate them.
There is no other way.

Ok. Thanks. That's very clear now. So it is the quantum bullet that we must aim to reach Planck mass energy by accelerating it... I thought it was a particular Planck target that we must aim using different projectiles from all angles to reach Planck energy. No doubts about it now.

Early. It was stated the Planck area couldn't detect our radio waves because it was like amoeba feeling the wave of a tsunami. But let's say there are Calabi–Yau manifolds (or other dynamics) inside the Planck length that can transmit signal.. can they transmit it with wavelength bigger than them like as big as radio waves? Or are radio transmitters limited to the length of their antenna... In our cellphones.. we can only send microwaves the length of our cellphone antenna? but then the submarine are able to receive ELF.. can the submarine transmitter able to send ELF too.. if true.. then the Planck scale Calabi-Yau or whatever can also send radio waves (or illustrative of any wavelength larger than the Planck length?) This is just for sake of illustration.. of course I'm not implying there is radio station inside the Planck length