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Science

Quantum Coherence Found Fueling Photosynthesis 135

Posted by samzenpus
from the spooky-energy dept.
Gaygirlie writes "Ars Technica has posted an interesting article about new findings regarding quantum physics and photosynthesis. Their excerpt for the article: 'Physicists have found the strongest evidence yet of quantum effects fueling photosynthesis. Multiple experiments in recent years have suggested as much, but it has been hard to be sure. Quantum effects were clearly present in the light-harvesting antenna proteins of plant cells, but their precise role in processing incoming photons remained unclear.' Here's a little background info for those unaware of what coherence and quantum coherence are."
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Quantum Coherence Found Fueling Photosynthesis

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  • Re:But wait (Score:5, Informative)

    by lennier (44736) on Wednesday December 07, 2011 @05:18PM (#38296232) Homepage

    A) The "what if" scenarios that have the Earth being destroyed, if we aren't off the Earth by then humankind is done.

    The problem is that even if we have off-Earth colonies, humankind will still be in just as much danger as if we didn't. Consider the most likely scenarios:

    1. Asteroid impact. Extensive damage to population and biosphere, but nothing that would render Earth less habitable than Mars. If we had the ability to colonise Mars, we'd certainly have the ability to build shelters on Earth. Result: no need to colonise Mars, just build greenhouses on Earth.

    2. War, social unrest, mass insanity. Possible huge damage to Earth's population, depending on how crazy things get. However, space structures will be launched by nation-states and large commercial combines with ties to Earth and will therefore surely be part of the wider Sol system social fabric and will take part in the war. Possibly they'll be the first to be destroyed. For example, World War II began in the core European nations but quickly swept up all European colonies, and some of them such as North Africa and the Pacific became key battlegrounds. Also, the technologies which launched human spaceflight were the flip-side of Earth's worst weapons of mass destruction - the ICBM program. Result: little shelter from a war by extending human culture into space, and a lot of actual danger created by doing so.

    3. Plague (including aliens and zombies). A fast spreading virus could conceivably take out most of the human population on-planet, but is unlikely to take out the biosphere or even all of the human population. Earth's survivors will still vastly outnumber any reasonably expected number of space colonists, and will still inherit a much more robust ecosystem than anything on Mars. Worse, any space colonisation program will involve constant resupply and then travel and trade between Earth and the colonies, which will be vectors for transmission of disease. Space colonies themselves will be tightly-packed and fragile, vastly more dangerous places in terms of plague. Result: no survival advantage in space colonies, in fact the colonies will probably die first.

    4. Environmental collapse. We're certainly degrading Earth's environment, but space won't help us - all other planets are far worse environmentally than we could conceivably ever make Earth. All space colonies will need either constant resupply from Earth, or the environmental skills to be completely self-sustaining. And if we had those skills, we could just build greenhouses on Earth. Terraform Mars? Well, if we could terraform anywhere reliably, we could start doing it on Earth and fix all our environmental problems in one hit. Result: no environmental disadvantage to going into space, but no advantage either.

    5. Ore depletion. Okay, so let's assume we fix the biosphere, but we're still running out of metals to make iPods. We can mine those in space, right? Well, yes and no. If we mine vast quantities of metal and introduce that into Earth's biosphere, that might mess up the biosphere (see 4). Moving asteroid-sized rocks around the system introduces huge military problems (see 2) as they'll be more dangerous than nukes. Space mining is also likely to be be more expensive than just recycling landfill, so where's the commercial advantage? Result: a commercial non-starter and a major military threat, best avoided really.

    6. Supernova, red giant. The big one, a complete solar-system destroying event with no chance of sheltering in place. This is the only scenario where conceivably we could improve our chances by going into (interstellar) space. Problem is, to get out of range of Sol going boom we'd need to have either a generation ship going for several hundred years and having already solved the closed life support problem (see 1, 4), so this will be a long-term rather than short-term capability. Best estimates for Sol going boom are millions to billions of years, so again, this is not a pressing human need. Result: maybe worth look

  • by FrootLoops (1817694) on Wednesday December 07, 2011 @07:20PM (#38297648)

    Seriously guys if somebody doesn't understand quantum physics reading the wiki page isn't going to do it.

    More than that, the first paragraph of the linked explanation is misleading, and the rest essentially requires an understanding of quite a bit of quantum mechanics to have a chance of following it. I have difficulty imagining somehow who actually understood the concepts involved linking such a poor explanation.

    Quantum coherence has to do with multiple particles. If most of the particles are in roughly the same (quantum) state, the system is called coherent. Otherwise, it is not coherent. To give an (oversimplified) example, take a bunch of electrons. Through a clever experiment, we may measure an individual electron's "spin", and the result will either be "up" or "down"--an understanding of spin is immaterial here; feel free to replace "spin" with "mood" and "up"/"down" with "happy"/"sad" if it scares you. The unintuitive part of quantum mechanics is that even if we performed the experiment twice with two indistinguishable electrons, our experiment may well come out differently. The crucial thing, though, is that each outcome has a fixed probability of occurring. Suppose, then, that we've prepared 100 electrons in such a way that if we perform our spin experiment, 30% of the time the electron will have spin up, and 70% of the time it will have spin down. An electron's quantum state for this experiment is (sweeping wavefunctions under the rug...) given by the probability of each outcome. Each of our 100 electrons has the same quantum state as the others, so the system is called (perfectly) coherent. If, however, we prepared 50 of the electrons to come out with the above probabilities and the remaining 50 electrons to come out with 100% spin up, the system is not coherent.

    (Disclaimer: I am not a physicist, but rather a mathematician with some interest in quantum physics. Please feel free to correct or supplement the above.)

  • by harryjohnston (1118069) <harry.maurice.johnston@gmail.com> on Wednesday December 07, 2011 @08:59PM (#38298520) Homepage

    No, quantum coherence is not about the electrons all having the same quantum state as one another; it's about the system as a whole having a single quantum state.

    An example of a coherent system would be one in which the electrons all have the same spin; say a 50% chance that they are all up and a 50% chance that they are all down, but zero chance that some are up and some are down. Another example would be a 50% chance that the odd-numbered electrons are up and the even-numbered onees down, a 50% chance they're the other way around.

Loose bits sink chips.

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