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Natural Science Forum / Physics / Particle Physics / September 2004Is light a matter?
Hi, I am a student at Casper College in Wyoming. I am taking a chemistry class and we are talking about light and weather or not it's a particle. If light is not a matter how does gravity affect it? How is it possible that light interacts with matter if it isn't matter? How can light be slowed or bent if it does not occupy space? These are some of the questions that are bothering me. I have been thinking about these questions for years now and I'm wondering how to pursue my knowledge further. As of now it seems to me that light is a matter and that we just don't have the equipment to measure the minute space it takes up. What do you think? : Hi, I am a student at Casper College in Wyoming. I am taking a : chemistry class and we are talking about light and weather or not it's : a particle. If light is not a matter how does gravity affect it? How : is it possible that light interacts with matter if it isn't matter? : How can light be slowed or bent if it does not occupy space? You should read _QED: the Strange Theory of Light and Matter_ by Richard Feynman, which answers your questions (and many others) in very clear non-technical language. ----- Richard Schultz schultr@mail.biu.ac.il Department of Chemistry, Bar-Ilan University, Ramat-Gan, Israel Opinions expressed are mine alone, and not those of Bar-Ilan University ----- There's something I must tell you, there's something I must say: The only really perfect love is one that gets away. > Hi, I am a student at Casper College in Wyoming. I am taking a > chemistry class and we are talking about light and weather or not it's > a particle. If light is not a matter how does gravity affect it? There are two sorts of matter: fermions (spin 1/2) and bosons (spin 1). Electrons are fermions, photons are bosons. Both are quantum mechanical objects, i.e. they sometimes behave like a wave and sometimes like a particle. There is another difference between electrons and photons: Latter are massless, therefore they are forced to move at the speed of light. > How > is it possible that light interacts with matter if it isn't matter? Photons couple to charged fermions, mediating the electromagnetic force. > How can light be slowed or bent if it does not occupy space? Electrons also appear as point-like particles in all experiments we have done so far. Actually already Newton treatet matter as points, that occupy no space. Matter needs to carry some sort of charge or be one of the intermediating bosons to interact. > Hi, I am a student at Casper College in Wyoming. I am taking a > chemistry class and we are talking about light and weather or not it's [quoted text clipped - 6 lines] > and that we just don't have the equipment to measure the minute space > it takes up. What do you think? Many of your questions have to do with preconceptions about nature that simply aren't true. For example, your instinctive guess that only matter can interact with matter is simply wrong, and you need to reorganize your picture of the world. It's actually prettier and simpler than you think, though different. Waves get bent all the time, and now I'm going to ask you to define the region of space occupied by a wave. Be careful here. I can certainly bend sound -- otherwise you wouldn't be able to hear someone talking around a corner. But it's not like a tunnel, moving from someone's mouth to your ear, either -- otherwise you wouldn't be able to overhear someone else's conversation. Think carefully about what you mean by "occupying space". However, there IS a problem with gravity and light. Photons have no mass and so should not interact with gravitons (according to a naive QM model for gravity). Einstein says that NOTHING interacts with gravity per se -- that things travel in straight lines through space. It's the space that gets bent with gravity. Putting QM and General Relativity together even *conceptually*, let alone mathematically, is the tough problem of the day. PD What do they teach you in school ? Irene and Frederic Joliot-Curie already proved this in 1933. They created a wet air cloud chamber and photographed the annihilation of a light particle that yielded its equivalent of particle matter (mass), it can be viewed at http://www.aip.org/history/einstein/ae22.htm. Light energy was photographed as it converted to particle matter (mass) supporting that matter and energy are the same in different manifestations of the same as Einstein suggested. You may wish to visit this website for new Unified Theory www.threexd.com Mark Oliver > > Hi, I am a student at Casper College in Wyoming. I am taking a > > chemistry class and we are talking about light and weather or not it's [quoted text clipped - 30 lines] > > PD |
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