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> If we could make an atomically perfect copy of the Mona Lisa, it would be absolutely indistinguishable from the original. "Absolutely"??? The painting is an

> If we could make an atomically perfect copy of the Mona Lisa, it would be absolutely indistinguishable from the original. "Absolutely"??? The painting is an off-axis bump on a slowly rotating roughly spherical planet; consequently it sheds gravitational radiation. The painting is effectively a rigid extended object, and thus the gravitational radiation has a corresponding characteristic mode depending on the painting's position and orientation. The mode propagates to infinity. Sure, it would take an ultra-super-hyper-advanced gravitational wave detector to pick it out at interstellar range, but it is possible in principle. Before forgery: one Mona Lisa mode; after forgery: two Mona Lisa modes. The modes will differ because of different position and/or orientation on Earth. The position and orientation of the "original" has changed over time, pretty substantially; the latter's position and orientation is likely to change over time too. Anyone observing the relevant bits of Earth's gravitational radiation spectrum (over time, if you want to think of it that way) would be able to distinguish the two. Trouble if the buyers are already accomplished gravitational wave astronomers (we've just barely started) and keep detailed records. I think it's easier to handwave an extremely tuned gravitational wave detector than an exact atomic duplicator or a device which determines that a pair of ~ 8kg paintings are atomically identical (especially one that does not render them atomically non-identical).

lisper 8y ago
> I think it's easier to handwave an extremely tuned gravitational wave detector than an exact atomic duplicator Well, lets look at the current state of the art with respect to each. We can make non-destructive 3-D scans of objects, and we can image and manipulate individual atoms. We can fabricate 3-D structures with feature sizes a few atoms wide. That's not quite at the level of a 3-D atomic duplicator, but it seems to me to be well on the way. The machines that do these things are not yet household items, but they are not uncommon, and the technology is improving all the time. By way of contrast, the state of the art in gravity wave detection lets us see nothing less energetic than the collision of two black holes, and there are two devices that can do this on the entire planet. So a 3-D atomic duplicator seems much more plausible than a device that can track an 8kg object through a gravitational field at interstellar distances.
- raattgift 8y ago
  > We can make non-destructive 3-D scans of objects Of their surfaces. What about the internal components? The Mona Lisa is many things but it is not very thin or flat. There are pigments and bindings involved that are sensitive to protein structure, as well; it's not just the count of atoms (and subatomic components; there are metals involved too, and isotope ratios are fingerprints), or even their relative position sensu stricto that matters. I'm not sure how you could go about non-destructively determining (for example) potassium radioisotope differences in the original painting's layers between the optical surface and the canvas. > state of the art in gravity wave detection ... black holes We can detect gravitational waves of much closer much smaller systems just fine, and did so about 105 years before Poincaré proposed them formally. It was almost eighty years later that they were cast into the current perturbative formalism though. The amplitude isn't really the critical factor with LIGO. It's sensitive to a particular frequency band (~ Hz - kHz) that is far from that of a small off-axis bump on a planet (~ microHz). It would totally pick up a set of deadlift weights spun around by a dental drill, if you could make that work in practice. (The amplitude difference between the sites would exclude it as an astronomical signal; the final inspiral of binary black holes and neutron stars have enormous amplitude, but that falls off linearly with distance, and they are very very far away, so the amplitude difference between sites is basically nil). > track an 8kg object through a gravitational field Given that one knows a number of things about the object including rough position and its surrounding environment (notably one wants to know its background metric exactly, or at least the exact model metric for Earth and some subleading-order non-Mona-Lisa contributions to perturbations thereof), it gets much easier. For a painting it's not something we could do today even if we had a spaceborne observatory sensitive to the relevant bits of Earth's GW spectrum, but it is plausible that we could observe the GWs shed by Olympus Mons with current technology, for example. (It'd be expensive to build). We have good lunar masscon data so can watch the GWs shed by those as the moon relaxes into a more spherically symmetric shape; we have decent masscon data for Earth so can in principle with today's technology watch seismic events using gravitational wave Earth observation (as opposed to astronomy) (earthquakes make Earth rounder and spin faster, so the remaining masscons shed even more gravitational radiation).
  - 8y ago

lisper 8y ago

> I think it's easier to handwave an extremely tuned gravitational wave detector than an exact atomic duplicator Well, lets look at the current state of the art with respect to each. We can make non-destructive 3-D scans of objects, and we can image and manipulate individual atoms. We can fabricate 3-D structures with feature sizes a few atoms wide. That's not quite at the level of a 3-D atomic duplicator, but it seems to me to be well on the way. The machines that do these things are not yet household items, but they are not uncommon, and the technology is improving all the time. By way of contrast, the state of the art in gravity wave detection lets us see nothing less energetic than the collision of two black holes, and there are two devices that can do this on the entire planet. So a 3-D atomic duplicator seems much more plausible than a device that can track an 8kg object through a gravitational field at interstellar distances.

raattgift 8y ago
> We can make non-destructive 3-D scans of objects Of their surfaces. What about the internal components? The Mona Lisa is many things but it is not very thin or flat. There are pigments and bindings involved that are sensitive to protein structure, as well; it's not just the count of atoms (and subatomic components; there are metals involved too, and isotope ratios are fingerprints), or even their relative position sensu stricto that matters. I'm not sure how you could go about non-destructively determining (for example) potassium radioisotope differences in the original painting's layers between the optical surface and the canvas. > state of the art in gravity wave detection ... black holes We can detect gravitational waves of much closer much smaller systems just fine, and did so about 105 years before Poincaré proposed them formally. It was almost eighty years later that they were cast into the current perturbative formalism though. The amplitude isn't really the critical factor with LIGO. It's sensitive to a particular frequency band (~ Hz - kHz) that is far from that of a small off-axis bump on a planet (~ microHz). It would totally pick up a set of deadlift weights spun around by a dental drill, if you could make that work in practice. (The amplitude difference between the sites would exclude it as an astronomical signal; the final inspiral of binary black holes and neutron stars have enormous amplitude, but that falls off linearly with distance, and they are very very far away, so the amplitude difference between sites is basically nil). > track an 8kg object through a gravitational field Given that one knows a number of things about the object including rough position and its surrounding environment (notably one wants to know its background metric exactly, or at least the exact model metric for Earth and some subleading-order non-Mona-Lisa contributions to perturbations thereof), it gets much easier. For a painting it's not something we could do today even if we had a spaceborne observatory sensitive to the relevant bits of Earth's GW spectrum, but it is plausible that we could observe the GWs shed by Olympus Mons with current technology, for example. (It'd be expensive to build). We have good lunar masscon data so can watch the GWs shed by those as the moon relaxes into a more spherically symmetric shape; we have decent masscon data for Earth so can in principle with today's technology watch seismic events using gravitational wave Earth observation (as opposed to astronomy) (earthquakes make Earth rounder and spin faster, so the remaining masscons shed even more gravitational radiation).
- 8y ago