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An Experiment Could Determine Whether Gravity Is Quantized (forbes.com)
TheAlexKnapp writes: Physicist Brian Koberlein explains an experimental proposal by Großardt et al, which would attempt to determine whether gravity is quantized. "Their idea," explains Koberlein, "is to take a charged disk of osmium with a mass of about a billionth of a gram and suspend it an electric field. This is small enough that its energy levels in the electric field would take on quantum behavior when cooled to temperatures a fraction of a Kelvin above absolute zero, but its also massive enough that its gravitational pull would affect the quantum behavior."
The two primary approaches to a quantum gravity, the "perturbative approach" and "the semi-classical method," predict different results from this type of interaction. So the results of the experiment, could, in principle, elucidate the right approach for developing future theories of quantum gravity.
The two primary approaches to a quantum gravity, the "perturbative approach" and "the semi-classical method," predict different results from this type of interaction. So the results of the experiment, could, in principle, elucidate the right approach for developing future theories of quantum gravity.
Just to be clear, Planck units have no physical significance. They're just a convenient way of doing physics calculations because when you use Planck units, you can treat some fundamental constants as equal to 1.
So Planck time isn't the frame rate of reality, it's just a really small unit that makes some calculations easier.
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Well, electron states being quantized has helped us to (truly) understand chemistry and create transistors as well as LEDs. By realizing that things are only allowed to make certain transitions under certain conditions, you can "cheat" and build up high-energy states that are far more stable than they really should be. I am not saying we would get macroscopic anti-gravity or a "Faraday cage for gravity", but this is kind of the space where we would get more specific explanations for how you might be able to accompish those things in theory. For very delicate experiments (similar to the one described!) and possibly sub-nanoscale manufacturing procedures, an understanding of a quantized nature of gravity influences might be useful, if only for better understanding the noise in measurements and tolerances.
There is a huge difference between something being smaller than any single event and it being quantized by that amount. Even if you can't find an event quicker than that, it is possible time is continuous in such a way that the spacing between events is not an integer number of Planck time. In fact, there isn't really anything in quantum mechanics that says that time behaves that way at all, unless you want to tack on additional hypotheses (and it makes a mess of things).
The Planck units are just multiplying fundamental constants together so that you get some value with the right units, and the significance of that is not necessarily quantization, but limits where extreme gravity and quantum mechanics would be present in the same setup. This either means we can speculate that such situations would require an understanding of quantum gravity, or would do something based on GR instead of quantum mechanics. The Planck mass is nothing extremely large or small for example, at a couple nanograms, although could be the largest mass a point particle can have before being a black hole (with some speculation).