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The books are wrong.
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Ever since I discovered that impacting photons deliver force, I have also believed photons have mass. The force of impact can be calculated as mass * velocity. If you take the force of impact of a photon and divide by the speed of light, the calculated mass is the same as if you convert its energy to mass with E = M * C^2.
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So from that you can calculate how big the photons are. correct???
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My you dismiss a hundred years of physists smarter than you so easily?
The "traditional rules" dealing with physics equations, f=ma and whatnot, only apply to the macroscale world, "big" things. Quite simply, stuff down in the micro and even moreso in the quantum level where you get into the nature of photons... the macroscale rules just don't apply. For instance, electrons which do have mass have no volume.
When things get small, the rules don't apply anymore. The reason why photons can impart momentum is because they transfer the energy directly and are absorbed by atoms, not by collision or reflection with a surface as with other paticles or bits of matter with mass.
The books are right, its just that the universe is a good deal more complex than can be packed into simple macroscale physics equations.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Ooo! Traditional thinking is correct and anyone with a new perspective is wrong! The Earth is flat, the sun revolves around the Earth, and disease causes those funny little things in the blood, not by it. Well, I don't agree. Louis Pasteur was ridiculed when he suggested germs cause disease, but he was right.
When thinking about photons, physics does get tricky. Photons travel at the speed of light, so time dilation causes bizarre effects. Applying this to "macro" or "micro" scale is not a valid distinction (contrary to the belief of many individuals with lots of alphabet soup behind their name). But you do have new considerations when dealing with subatomic particles. First, what is matter? What is mass? That which appears solid, really isn't. Atoms are mostly empty space. Atoms are held together to form molecules by static electricity and the motion of their electrons. Atomic nuclei are held together by the strong and weak nuclear forces. These are all forces. When you push your hand against a table top, you are really pressing one set of static electricity forces against another; like charges repel. Both your hand and the table top are almost entirely empty space. But what are the subatomic particles composed of? Are they some sort of solid billiard balls that somebody rubbed a cat against? No, they are composed of standing waves of energy. The inside of subatomic particles deals with multiple waves interacting with one another, and may involve more than 4 dimensions of space-time. At least some of these waves are traveling at the speed of light, with internal reflection and/or refraction keeping them within the particle. But the particle isn't a solid entity; it's just the collection of entangled waves, so the waves themselves ARE the subatomic particle. There has been an attempt to mathematically model the inside of a proton, and the result was very close to observed result. However, the model was very complex, leading to the conclusion that the inside of a proton is also very complex.
Ok, so there is no such thing as anything that is solid, there are just complex forms of energy. Then why do subatomic particles like protons and neutrons have mass while photons do not? That leads to the question "what is mass"? Without getting into more argument, I'll leave this exercise for the reader: compile a detailed scientific description of mass, then compile a list of those attributes which do or do not apply to protons, neutrons, and photons. Exactly what makes a photon different?
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The mear fact that they carry momentum means they carry mass.Anything that has energy means they have mass.Photons have energy and they carry momentum so they must have mass. Do you believe everything you read?
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I'm almost afraid to ask, but why do you think that the books are wrong? It's an established fact that photons have mass, otherwise they couldn't transfer momentum. They have no rest mass which is fine since they never stand still.
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So from that you can calculate how big the photons are. correct???
Mass doesn't say anything about size. Density could be anything. The size of a photon has been measured by its wavelength. In fact, molecules of a transparent solid can be oriented so as to filter light. Photons with waves oriented in the same direction can pass between the molecules, but photons oriented cross-wise do not. This is a polarized filter. This has even been taken a step further by having molecules oriented so that each layer of material has molecules rotated just a few degrees clockwise or counter-clockwise from the previous layer. Photons will follow the path; this has been used to change polarization of light by 90º.
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Even a photon at rest has mass.
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The books are wrong.
Which books are you referring to?
last year [http://www.aip.org/enews/physnews/2003/split/625-2.html]AIP said the new limit on photon mass, was less than 10^-51 grams, don't know if this has changed since then from further experimentation. Its an area of science that baffles a lot of people, and does require a bit of a change of thinking to get your head around - I mean a mass of less than 0.00000000000000000000000000000000000000000000000001 grams that is tiny by anyones standards.
There was a young lady named Bright.
Whose speed was far faster than light;
She set out one day
in a relative way
And returned on the previous night.
--Arthur Buller--
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Actually, that answer isn't really correct. The polarization of light has nothing to do with how wide it is and its ability to pass through a given space.
Polarization occurs because light can be thought of as an oscillating electric field at a right angle to an oscillating magnetic field. In linearly polarized light, both the electric and magnetic component are also ata right angle to the direction of travel. (imagine two sine waves at right angles to each other - the long axis of the travel is the direction the light is going.)
Polarizing materials have a net imbalance in how easily they intereact with an oscillating magnetic field. This is due to the crystal structure. Most crystalline materials exhibit this behavior to some extent. Materials that act as polarizing filters simply exhibit this property to a greater extent. When light hits a polarizing filter, the electric field interacts with the material depending upon the angle it hits at.
As far as the 'size' of light, it's a poorly phrased question. elementary particles don't really have a size as we know it. a photon has a size of 0. A light wave in the visible range has a size of about half a micron. The currently accepted model (which is likely to be at least partially wrong) is that the wave nature of light is in the form of a probability wave that takes on the form of a photon when it interacts with another particle. The probability wave simply is the proability distribution of where that interaction is likely to take place.
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Even a photon at rest has mass.
What do you base this on?
from [http://math.ucr.edu/home/baez/physics/P … _mass.html]http://math.ucr.edu/home....ss.html
If the rest mass of the photon was non-zero, the theory of quantum electrodynamics would be "in trouble" primarily through loss of gauge invariance, which would make it non-renormalizable; also, charge-conservation would no longer be absolutely guaranteed, as it is if photons have vanishing rest-mass. However, whatever theory says, it is still necessary to check theory against experiment.
There was a young lady named Bright.
Whose speed was far faster than light;
She set out one day
in a relative way
And returned on the previous night.
--Arthur Buller--
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No, a photon has no rest mass since it can never be at rest. Trying to apply standard Newtownian physics to a quantum mechanical concept makes about as much sense as trying to measure speed in liters. The standard mass-kinetic energy equations you are familiar with are wrong. For macroscopic objects, they have been replaced with relativistic equations (which, for everyday objects ends up being almost exactly what Newtonian mechanics predicts) and small particles are governed by quantum mechanics which is a completely different ball game.
Reconcilling the world of the small and large is one of the greatest problems in science. Some recent experiments in quantum decoherence are starting to shed light on the problem but we are still a long ways away from understanding what's going on.
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Great so if a photon hits a H2 atom at rest directly from behind it should propel the H2 atom forward and increase the forward velocity by how much?
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Same thing happens in a black hole light can not escape so the photons are at rest.
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It depends on what wavelength of the light is. Hydrogen will only absorb light of certain, specific frequencies. (hence why spectroscopy works). The absorbtion of a single photon will give some momentum to a hydrogen atom. The higher the frequency, the greater the momentum transferred. I don't have any numbers handy but it won't be much. You need a LOT of light to be able to generate any meaningful light. That's why you can't use a flashlight to fly around.
Solar sails can generate thrust by using light. The best situation is to use a reflective surface. Basically, reflective materials like metas have loosly bound electrons that kinda of float around like an electron gas, not particularly bound to one atom. (it's why metals are conductive) When light hits, the elecrical component causes a reciprocal oscillation in the electron dentisity that basically causes the photon to 'bounce' off. It's kind of like a rope that's attatched to a wall with a spring - if you give the rope a twitch to send a wave down its length, the wave will bounce back off the spring.
In this fashion, the photons are bounced backwards. So not only do you get the momentum of the light hitting the object, you also get the momentum of the photon being redirected in the oposite direction - you've just doubled your thrust. Even so, at the Earth's distance from the sun, a sail with an area of a square kilometer generates about 1 kg of thrust. It's pretty weak. The big problem with solar sails, is that in order to get enough thrust, you need a HUGE sail and the mass of the sail adds so much weight to a spacecraft that it takes forever to get anywhere.
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So if you use a 1mw laser beam to hit a H2 atoms how fast will those atoms go?
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So if you use a 1mw laser beam to hit a H2 atoms how fast will those atoms go?
What frequency of light from the laser?
There was a young lady named Bright.
Whose speed was far faster than light;
She set out one day
in a relative way
And returned on the previous night.
--Arthur Buller--
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As close as it can get.
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Well, it depends on how concentrated the beam is, how well the wavelength coupled to H2 absorbtion, how long you hit the atoms with the light and so on.
For individual atoms, using a laser is a very inefficient way to push them around. In fact, with a regular gas, you'll just heat the gas up. This is because the atoms will bounce off each other and soon, their velocity vectors become randomized. You'll only get significant velocity if the gas is extremely thin. By thin, I mean molecular flow regime which starts at about 1 billionth atmospheric pressure.
So, to answer the question you were about to ask, a laser would push hydrogen up your pipeline - but very poorly and only if you had pretty much no hydrogen in it. You'd get more H2 to orbit if you built a ladder and had a guy carry buckets of the stuff up to orbit by hand.
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Nope, I was going to ask how fast would this propel a spacecraft??
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Hydrogen molecules only absorb at particularly specific wavelengths, that is, the "color" of the light and if it absorbs has nothing to do with the intensity or quantity of the light.
Since photons have little (if any) mass, using them to accelerate your reaction mass (hydrogen) will not get you anywhere.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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How fast it will accelerate the H2 will determine if you can go anywhere.
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No, the quantity of hydrogen you can push to a certain linear velocity determines if you can get some place. If you can push a few molecules of hydrogen up to 0.5C, you still aren't going to get anywhere, because the reaction mass is so small that your thrust is essentially zero. Hydrogen's mass is relativly constant up until relativistic speeds, so that won't help you either.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Exacly what I was saying how fast can it push the H2?
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