A Universe Made of Tiny, Random Chunks (2013)
nautil.us
nautil.us
If I have understood the article correctly one would be able to measure the length of a spaceship relative to the Planck length and deduce velocity, entirely locally (i.e. onboard the spaceship).
This is a fundamental departure from general relativity which says there is no special frame of reference.
There are many attempts to combine these theories into a universal theory (pun intended), but it is hard to check the corner cases where those theories differ. That's one of the reasons we build better and better particle accelerators.
Either way, it doesn't make sense to apply (pure) general relativity to the small scale, nor to apply (pure) quantum theory to the large scale. The physicists know for decades about of that issue and are already taking care of that.
For the most part particle accelerators are not needed to explain quantum gravity, we do use them to find "new physics" but this new physics is more in the lines of the known unknowns.
We also do apply relativity to small scales every day, without relativity muons could not be discovered and without relativity to some extent even large particle accelerators would not "work" because the effects of spatial contractions are pretty important for how we predict and analyse the data coming from particle accelerators especially the "messy kind" like the LHC.
As for the large scale stuff as mentioned earlier quantum gravity is pretty compatible with general relativity in terms of explaining how the universe that we see today looks and works, you can easily explain why and how the moon rotates around the earth, it does rely on a massless spin-2 particle called a graviton which is yet to be "discovered" and it does break if the graviton would have a different spin (for example spin-0 graviton).
So I don't really understand the notion of why people still think that quantum gravity and general relativity aren't compatible to the extent of "what the fuck is going on", which is odd since afterall GR isn't 100% compatible with the Standard Model either, since GR is background independent and does not care about the particular state or shape of space-time while SM does.
Not sure at which point you disagree with my statement, though.
Each theory is useful for various things because each theory provides you with certain tools and perspectives that are useful for performing specific tasks.
At the end every theory is a set of laws and abstractions you use theories to change the perspective of how you look at things but these are often abstracts.
You can look at particles as particles, waves or fields it doesn't change reality but every one of these viewpoints comes with its unique benefits and you can chose between them depending on what benefits you most to for a specific task or a situation.
However seeing the quantum effects like a version of compression, dark matter and dark energy which could be an ugly hack to stabilize matter and galaxies, the fractal self similarity of the universe is just too amusing to ignore :)
I feel like the whole "wave-particle duality" is already a hint that the true nature of reality may always remain outside of our observation capability.
In fact, I think that humans may be a little too biased towards picturing everything as made up of discrete parts ("particles"), and that is probably a byproduct of having visual eyesight. Can't wait to meet alien intelligences with completely different senses and see what they think. :)
Wave-particle duality is a bit of a misnomer it's more of a pop-sci concept, all particles are defined by their wave function and there isn't a "particle function".
And if you think that we are too biased towards picturing everything made out of discrete parts then you won't like QM which is basically what the Q stands for which is "quanta" as in the smallest clump-thing-w/e of something.
That said most people that choose to study physics in high school (year 10-12) and or college would be exposed to Quantum Field Theory which makes everything make considerably more sense when you start thinking about everything in terms of fields.
Once you no longer think of an electron as an individual thing but as a electron field that extends through all space and the particles are the quanta of that field as in localized excitations of the field which when they reach a certain amplitude or energy level bring forth something we can measure and identify as an electron.
I wish QFT would be popularized more because it would bring so many important concepts into the common sense realm and it would actually be easier to explain things like why do particle accelerators work.
However this is wrong. The Planck length is the minimal length of a 4-vector (a 4-dimensional vector measuring the distance between two events in space-time). But the length of a 4-vector is invariant under Lorentz transformation, so it also doesn't Lorentz contract. So there is no conflict between special relativity and a constant Planck length.
The arbitrary constant is 1. How is 1 less arbitrary than 2, 42, or 3.14?
I don't get it - is it trying to say objects of Planck length wouldn't contract due to relativity? If so - why?
A different factor, like 2, is more arbitrary, since "* 2" can't be left out without changing the value.
You can make the claim that a "* 1" factor is lurking in there, but even from that perspective it's less arbitrary than "* 2", since we could claim that "* 2" also has a "* 1" lurking in it, and so on :)
Units don't match - ct^2 is in m*s, not m^2.
It's more accurate to talk about Planck scale and not think it as strict limit.
Planck scale is where the structure of spacetime itself becomes dominated by quantum effects and the structure of spacetime may start looking really strange. Strange theories like loop quantum gravity, causal sets, causal dynamical triangulation, fractal cosmology, etc. work at Planck scale. According to fractal cosmology spacetime is 2-dimensional in Planck scale and gradually becomes 4-dimensional in larger scales. Loop quantum gravity sees it as "foamy".
Planck scale is also the area where measuring distances (differentiating with different positions in space) becomes impossible.
Which suggests internal structure of some kind.
I'm wary of any explanation that says "Well, it's just random", because randomness turns out to be a complicated process.
It's hard to imagine that some kind of prototypical base quantum would be inherently random just because.
I suppose it's possible. But it would be unexpected.
These units are very useful in QM and as "constants" (not the best choice of words since Planck units intentionally ignore constant values to some extent) that can be used to describe a relativistic universe.
*You can use Planck Length/Time to put a lower limit on any possible wavelength that below it a wave cannot exist, other Planck units can also be in the ballpark of the smallest possible unit/quanta of various things in various theories.
The uncertainty principle states that the product of the standard deviation of the momentum and posisition of a particle is bounded from below by h/4pi, where h is the plank constant.
This means that, in order to probe small distances, we must have great uncertainty in the momentum invovled, which means that there must be a lot of kinetic energy in the system. As the distances we probe become smaller, we have an increasing amount of energy in a decreasing amount of space.
E=mc^2 tells us that energy and mass are interchangeable. Specifically, energy, like mass, causes gravity. In order to probe below the plank length, we would need to put so much gravity in so small a space that we would form a black hole. However, because we cannot observe the inside of a blackhole, this prevents us from observing anything smaller than the plank length.