Kvantfysik odödlig
For example, a fluctuating metric would seem to imply a fluctuating causal structure and spatiotemporal ordering of events, in which case, how is one to define equal-time commutation relations in the quantum theory? Why not just follow the model of QED and quantize the gravitational field, similar to the way in which the electromagnetic field was quantized? Other approaches are more modest, and seek only to bring general relativity in line with quantum theory, without necessarily invoking the other interactions.
Jag tror att vi halvt omedvetet behandlar hela vår omgivning inklusive oss själva som om vår omgivning och vi själva vore objektiva. A model of the world according to general relativity consists of a spacetime manifold with a metric, the curvature of which is constrained by the stress-energy-momentum of the matter distribution. Thus general relativity is a classical theory in the sense given above. If the latter is true, then the construction of a quantum theory of gravity may demand entirely unfamiliar elements.
However, philosophers who have a taste for a broader and more open-ended form of inquiry will find much to think about, and it is entirely possible that future philosophers of physics will be faced with problems of a very different flavour as a result of the peculiar nature of quantum gravity. This approach asks for an analysis of the ontological pictures of the two ingredient theories of quantum gravity, so that their consistency the consistency of the resulting synthesis can be properly assessed.
These quantities are represented by tensor fields, sets of real numbers associated with each spacetime point. For example, in quantum mechanics, the position of an electron may be specified with arbitrarily high accuracy only at the cost of a loss of specificity in the description of its momentum, hence its velocity. Insofar as all extant physical theories rely on a classical non-quantum spacetime background, this presents not only extreme technical difficulties, but also profound methodological and ontological challenges for the philosopher and the physicist.
Or it may be more like Ascending and Descending , an impossible construction which looks sensible in its local details but does not fit together into a coherent whole when using presently existing building materials. Though quantum gravity has been the subject of investigation by physicists for almost a century see Rickles , philosophers have only just begun to investigate its philosophical implications.
Dutch artist M. Some of his work, for example Ascending and Descending , relies on optical illusion to depict what is actually an impossible situation. On the surface, the incompatibility between general relativity and quantum theory might seem rather trivial. See the Other Internet Resources section below for images.
Historia och tankar kring kvantfysiken
Theories of quantum gravity, on the other hand, are bedeviled by a host of technical and conceptual problems, questions, and issues that make them largely unsuited to this kind of interpretive approach. That is: we cannot ignore the problem of quantum gravity. Other works are paradoxical in the broad sense, but not impossible: Relativity depicts a coherent arrangement of objects, albeit an arrangement in which the force of gravity operates in an unfamiliar fashion.
Given that quantum gravity does not yet exist as a working physical theory, one might legitimately question whether philosophers have any business being involved at this stage. In doing so, they manage to encompass traditional, Newtonian gravitational phenomena such as the mutual attraction of two or more massive objects, while also predicting new phenomena such as the bending and red-shifting of light by these objects which have been observed and the existence of gravitational radiation until very recently, with the direct detection of gravitational waves by LIGO, this was, of course, only indirectly observed via the decrease in the period of binary pulsars-see the Physics Nobel Prize presentation speech by Carl Nordling.
Den formulerades under talets första hälft och är en framgångsrik beskrivning av materiens och energins beteende i mikrokosmos. Många uppfattar kvantfysiken som icke-intuitiv. The problem is that our fundamental theories of matter and energy, the theories describing the interactions of various particles via the electromagnetic force and the strong and weak nuclear forces, are all quantum theories. Whence the incompatibility?
In such cases, one typically proceeds by assuming the physical soundness of the theory or theoretical framework and drawing out the ontological and perhaps epistemological consequences of the theory, trying to understand what it is that the theory is telling us about the nature of space, time, matter, causation, and so on.
Quantum Gravity
At the same time, in the quantum theory of the electromagnetic field known as quantum electrodynamics QED , the electric and magnetic fields associated with the electron suffer an associated uncertainty. However, these technical problems are closely related to a set of daunting conceptual difficulties, of interest to both physicists and philosophers. Hence, the problem of quantum gravity can mean very different things to different researchers and what constitutes a possible solution to one group might not qualify as such to another.
Kvantmekanik, även kallad kvantfysik eller kvantteori, är en övergripande teori inom den moderna fysiken och även inom kemin. Whatever the final outcome, the situation at present is one of flux, with a great many competing approaches vying for the prize. For example, in canonical quantizations of gravity one isolates and then quantizes geometrical quantities roughly the intrinsic and extrinsic curvature of three dimensional space functioning as the position and momentum variables.
See the section on the Lagrangian formulation in the entry on quantum field theory. In most, though not all, theories of quantum gravity, the gravitational field itself is also quantized. In quantum theories , these physical quantities do not in general have definite values. When one attempts to quantize gravity, one is subjecting some of the properties of spacetime to quantum fluctuations. Cao believes that the conceptual nature of the problem demands a conceptual resolution.
Häri startar de upplevda paradoxerna och svårigheterna med att förstå fenomenen som kvantfysiken påvisar. Likewise, if one focusses in on the spatial geometry, it will not have a definite trajectory. Since the contemporary theory of gravity, general relativity, describes gravitation as the curvature of spacetime by matter and energy, a quantization of gravity seemingly implies some sort of quantization of spacetime geometry: quantum spacetime.
Quantum gravity itself may be like this: an unfamiliar yet coherent arrangement of familiar elements. In general, physical quantities are described by a quantum state which gives a probability distribution over many different values, and increased specificity narrowing of the distribution of one property e. This is more or less the path that was taken, but it encounters extraordinary difficulties. Given the uncertainty principle and the probabilistic nature of quantum theory, one has a picture involving fluctuations of the geometry of space, much as the electric and magnetic fields fluctuate in QED.
But ordinary quantum theory presupposes a well-defined classical background against which to define these fluctuations Weinstein, a, b , and so one runs into trouble not only in giving a mathematical characterization of the quantization procedure how to take into account these fluctuations in the effective spacetime structure? However, it is also important to note that the prize is not always the same: string theorists seek a unified theory of all four interactions that has the power of explaining such things as the numbers of generations of elementary particles and other previous inexplicable properties.