The dumb questions thread

[fast]

Dumb question time.

Assuming I'm wrong, I ask, "why isn't the smallest possible object not perfectly shaped like a cube?

What I'm envisioning is that the smallest possible object is 1 Planck length in length, width, and height.

In fact, if we were take an object (any object) and separate each divisible part, we would be left with an exact number of perfectly shaped cubes.

Dumb, I know, but if I'm wrong (which ha ha, how couldn't I be?), WHY am I wrong?

So, what you're envisioning is a cube with eight corners--each of which is smaller than a Plank length. Do I have that right?

Partly yes. There is a cube with eight corners. Basically, a block. A block of substance. If you are above it looking down, you'll see four corners. The distance from one point to the second point is exactly 1 Planck length. Well, not diagonally, but if we're to measure the perimeter (of the top view) it would equal 4 Planck lengths.

 

[bilby]

Dumb question time.

Assuming I'm wrong, I ask, "why isn't the smallest possible object not perfectly shaped like a cube?

What I'm envisioning is that the smallest possible object is 1 Planck length in length, width, and height.

In fact, if we were take an object (any object) and separate each divisible part, we would be left with an exact number of perfectly shaped cubes.

Dumb, I know, but if I'm wrong (which ha ha, how couldn't I be?), WHY am I wrong?

So, what you're envisioning is a cube with eight corners--each of which is smaller than a Plank length. Do I have that right?

Partly yes. There is a cube with eight corners. Basically, a block. A block of substance. If you are above it looking down, you'll see four corners. The distance from one point to the second point is exactly 1 Planck length. Well, not diagonally, but if we're to measure the perimeter (of the top view) it would equal 4 Planck lengths.

How could you see a corner? Given that the corner is necessarily smaller than the smallest thing possible?

 

[fast]

Partly yes. There is a cube with eight corners. Basically, a block. A block of substance. If you are above it looking down, you'll see four corners. The distance from one point to the second point is exactly 1 Planck length. Well, not diagonally, but if we're to measure the perimeter (of the top view) it would equal 4 Planck lengths.

How could you see a corner? Given that the corner is necessarily smaller than the smallest thing possible?

Eh, I can see this ain't gonna take long, lol. I couldn't find the "ridiculously stupid" thread

But, while I'm here, let me go a tad bit further down the rabbit hole.

What I'm picturing isn't that the corner isn't smaller but rather the cube is indivisible. Imagine a 16 inch ruler (that's 1 inch thick) that could not be broken anywhere except at the inch increments, no matter how much force was applied. We could break the ruler in half and have two 8 inch pieces. We could take one of those and break it in half and have two 4 inches. We could do it again but then only once more. Then, we'll be left with an object with length, width, and height measuring 1x1x1.

So, it's not that there isn't anything smaller than an inch, just that nothing that size can be divided any further.

 

[skepticalbip]

But then a Planck sphere would be smaller since it would be able to fit inside the Planck cube.

 

[fast]

But then a Planck sphere would be smaller since it would be able to fit inside the Planck cube.

okay, but we aren't told the smallest substance is a Planck sphere but a Planck length.

We live in a 3D world, and we cannot literally have true 2d objects. Even the thinnest string (if it's in fact real) has depth.

ETA: I didn't say that to suggest a sphere is 2d.

 

[Jokodo]

But then a Planck sphere would be smaller since it would be able to fit inside the Planck cube.

okay, but we aren't told the smallest substance is a Planck sphere but a Planck length.

We live in a 3D world, and we cannot literally have true 2d objects. Even the thinnest string (if it's in fact real) has depth.

ETA: I didn't say that to suggest a sphere is 2d.

No, we don't live in a 3D, not the way you seem to believe. The universe doesn't have a privileged x, y, and z axis, it doesn't have a an equatorial plane, it doesn't have up and down (for all we know). "3D" is just a model useful for describing and naming points in space. Three coordinates is the minimum required to uniquely identify a spot in space, but it should be rather trivial to come up with a system that requires 5 or 23.

Since the universe (probably) doesn't have intrinsic up, down, north, west, south, east, your idea that a planck volume should be a cube begs the question: how would it be oriented?

 

[fast]

But then a Planck sphere would be smaller since it would be able to fit inside the Planck cube.

okay, but we aren't told the smallest substance is a Planck sphere but a Planck length.

We live in a 3D world, and we cannot literally have true 2d objects. Even the thinnest string (if it's in fact real) has depth.

ETA: I didn't say that to suggest a sphere is 2d.

No, we don't live in a 3D, not the way you seem to believe. The universe doesn't have a privileged x, y, and z axis, it doesn't have a an equatorial plane, it doesn't have up and down (for all we know). "3D" is just a model useful for describing and naming points in space. Three coordinates is the minimum required to uniquely identify a spot in space, but it should be rather trivial to come up with a system that requires 5 or 23.

Since the universe (probably) doesn't have intrinsic up, down, north, west, south, east, your idea that a planck volume should be a cube begs the question: how would it be oriented?

Maybe it's the word "length" in the term, "Planck length" that is throwing me off base.

What would the dimensions of the smallest object possible be? Could we have an object 256 Planck length long, high and wide? I was making the jump that as we went down in size, there is a limit-- a limit to what can actually be the case no matter our technological advances. Right now, the actual measurable size might be substantially higher, but if one Planck length is the shortest something can be divided (and no more), then that's the limit.

I might not be able to force upon the world my notions of up and down or left and right or forward and back, but my delusions aside of how things are, I thought the Planck length would be the smallest length an object can have.

 

[George S]

More like: Two things which are within a Planck length nature considers them at the same place.

 

[Wiploc]

Partly yes. There is a cube with eight corners. Basically, a block. A block of substance. If you are above it looking down, you'll see four corners. The distance from one point to the second point is exactly 1 Planck length. Well, not diagonally, but if we're to measure the perimeter (of the top view) it would equal 4 Planck lengths.

How could you see a corner? Given that the corner is necessarily smaller than the smallest thing possible?

How could there be a corner ... smaller than the smallest thing possible?

 

[fast]

Partly yes. There is a cube with eight corners. Basically, a block. A block of substance. If you are above it looking down, you'll see four corners. The distance from one point to the second point is exactly 1 Planck length. Well, not diagonally, but if we're to measure the perimeter (of the top view) it would equal 4 Planck lengths.

How could you see a corner? Given that the corner is necessarily smaller than the smallest thing possible?

How could there be a corner ... smaller than the smallest thing possible?

Smaller than the smallest indivisible thing possible--not smaller than the smallest thing possible.

 

[beero1000]

The Planck length is not the shortest possible length - it's the length scale at which quantum mechanics and general relativity stop being copacetic. Presumably, that's where a good theory of quantum gravity will come in to unify them and describe what would happen.

We don't know what that theory of quantum gravity would look like yet.

 

[fast]

Oh

 

[steve_bank]

The Planck length is not the shortest possible length - it's the length scale at which quantum mechanics and general relativity stop being copacetic. Presumably, that's where a good theory of quantum gravity will come in to unify them and describe what would happen.

We don't know what that theory of quantum gravity would look like yet.

I believe that is incorrect. Conceptually without a min step you end up with Zeno's paradox.

So far everything appears quarantined, both energy and matter. Continuous is an aggefate of quantum conditions, like Newtonian mechanics.

In practice in the limit as making changes get very small energy needed tries to go to infinity,

 

[beero1000]

The Planck length is not the shortest possible length - it's the length scale at which quantum mechanics and general relativity stop being copacetic. Presumably, that's where a good theory of quantum gravity will come in to unify them and describe what would happen.

We don't know what that theory of quantum gravity would look like yet.

I believe that is incorrect. Conceptually without a min step you end up with Zeno's paradox.

So far everything appears quarantined, both energy and matter. Continuous is an aggefate of quantum conditions, like Newtonian mechanics.

In practice in the limit as making changes get very small energy needed tries to go to infinity,

No, you are wrong. As far as we can tell, space and time are continuous and, thus far, every attempt at formalizing a discretized model of spacetime has failed.

The Planck length is what I said; it is the length where general relativity and quantum mechanics can no longer be reconciled. In particular, because we know that the two theories can't possibly both be right at that scale and the Planck length calculation requires them both, we know that the specific predicted Planck length value is irrelevant. All that matters is the approximate scale, to an order of magnitude or so, beyond which we cannot trust the predictions from either theory.

The Planck scale then isn't a fixed number at all, it's the neighborhood of sizes where the two theories clash, and the predictions of one cause the other to go haywire. In other words, it's the approximate scale where the currently missing theory of quantum gravity would need to become relevant.

The notion of the Planck length as the 'smallest possible length' is pop-science hand-waving to the point of nonsense.

 

[steve_bank]

In Newtonian mechanics we treat morels as mathematically continuous because we are so far above quantum effects. In principle, the velocity of a rocket can only change in discrete steps of energy.

Back again to what is space and what is time?

We observe change and distance, quantified by seconds and meters. Time is clock ticks.

As you try and reduce the increment of tine electronically or mechanically you will eventually run into quantum limitation, atoms and particles. Same with the meter.To our current state of science everything is quarantined held together by fields, which are also quarantined.

elaborate what you mean by quantum physics no longer applying, we can say simply we do not know.

 

[beero1000]

In Newtonian mechanics we treat morels as mathematically continuous because we are so far above quantum effects. In principle, the velocity of a rocket can only change in discrete steps of energy.

Back again to what is space and what is time?

We observe change and distance, quantified by seconds and meters. Time is clock ticks.

As you try and reduce the increment of tine electronically or mechanically you will eventually run into quantum limitation, atoms and particles. Same with the meter.To our current state of science everything is quarantined held together by fields, which are also quarantined.

elaborate what you mean by quantum physics no longer applying, we can say simply we do not know.

All current physics treats space and time as continuous, including quantum mechanics.

 

[bilby]

In Newtonian mechanics we treat morels as mathematically continuous because we are so far above quantum effects. In principle, the velocity of a rocket can only change in discrete steps of energy.

Really? What principle tells us this?

Back again to what is space and what is time?

We observe change and distance, quantified by seconds and meters. Time is clock ticks.

No. Clock ticks measure time, but clock ticks are not time, and time is not clock ticks, any more than graduations on a ruler are distance. We can have distance without a ruler, and we can have time without a clock.

As you try and reduce the increment of tine electronically or mechanically you will eventually run into quantum limitation, atoms and particles. Same with the meter.To our current state of science everything is quarantined held together by fields, which are also quarantined.

elaborate what you mean by quantum physics no longer applying, we can say simply we do not know.

We can. But you don't. You say "As you try and reduce the increment of tine electronically or mechanically you will eventually run into quantum limitation, atoms and particles. Same with the meter.To our current state of science everything is quarantined held together by fields, which are also quarantined.". You don't say "I do not know". Why not?

 

[Juma]

The Planck length is not the shortest possible length - it's the length scale at which quantum mechanics and general relativity stop being copacetic. Presumably, that's where a good theory of quantum gravity will come in to unify them and describe what would happen.

We don't know what that theory of quantum gravity would look like yet.

I believe that is incorrect. Conceptually without a min step you end up with Zeno's paradox.

So far everything appears quarantined, both energy and matter. Continuous is an aggefate of quantum conditions, like Newtonian mechanics.

In practice in the limit as making changes get very small energy needed tries to go to infinity,

Zenos paradox is just a paradox, a wrong-think, not some physical law.
It is totally possible to move through an infinity of positions.

 

[steve_bank]

The Planck length is not the shortest possible length - it's the length scale at which quantum mechanics and general relativity stop being copacetic. Presumably, that's where a good theory of quantum gravity will come in to unify them and describe what would happen.

We don't know what that theory of quantum gravity would look like yet.

I believe that is incorrect. Conceptually without a min step you end up with Zeno's paradox.

So far everything appears quarantined, both energy and matter. Continuous is an aggefate of quantum conditions, like Newtonian mechanics.

In practice in the limit as making changes get very small energy needed tries to go to infinity,

Zenos paradox is just a paradox, a wrong-think, not some physical law.
It is totally possible to move through an infinity of positions.

I was making a point.If distance is infinitely divisible you can end up with the paradox.

People use the words space and time without definition as some metaphysical obstruction. In relativity space is in meters and time is in seconds. The meter is defined as an integer number of wavelengths of light.

What space 'is' for me has no meaning. Unless we can quantify something we can not scientifically describe it. Space is separation in meters.

 

[steve_bank]

Really? What principle tells us this?No. Clock ticks measure time, but clock ticks are not time, and time is not clock ticks, any more than graduations on a ruler are distance. We can have distance without a ruler, and we can have time without a clock.

As you try and reduce the increment of tine electronically or mechanically you will eventually run into quantum limitation, atoms and particles. Same with the meter.To our current state of science everything is quarantined held together by fields, which are also quarantined.

elaborate what you mean by quantum physics no longer applying, we can say simply we do not know.

We can. But you don't. You say "As you try and reduce the increment of tine electronically or mechanically you will eventually run into quantum limitation, atoms and particles. Same with the meter.To our current state of science everything is quarantined held together by fields, which are also quarantined.". You don't say "I do not know". Why not?

A Socratic attack?

I'd have to look it up, I believe the PL in part rests on the quantification of energy.

If you believe reality is continuously divisible, describe it.