Owner: future of physics URL:http://softcracked.googleapges.com/pb.html Join Date: Thu, 11 Oct 2007 04:25:46 -0500 Rating:0 Site Description: Discipline of Science dealing with the properties of matter and energy. !!!---This blog is particualy for question that will be asked and their answers!!! It is not for journal and research work or an article. Site statistics:Click here
Why does hot air escape things? 2007-10-15 02:00:00 I'm going to address some other cases in addition to the one you've proposed in order to hopefully make the concepts clearer. First I want to talk about hot air inside a container with no holes, then air at any temperature in a container with holes, and then finally the situation you're asking about: hot air inside a container with holes. Even if your container had no holes and was perfectly sealed, the air trapped inside it would eventually equilibrate to equal the temperature of the container's surroundings. In this situation, the air inside the container is what is called a "closed system", but even closed systems can exchange heat with their surroundings. The same air molecules would remain inside the container over time, but their temperature would be affected by the temperature outside the container. This is because heat can be conducted through solid objects. If we assume the air inside the container is hotter than the air outside it, the inside air will transfer heat to the Read more:things
Is there any practical or theoretical limit to electrical potential? 2007-10-12 03:19:00 Electrical potential is the potential energy of some charge(s) (thepotential that charge has to do work) divided by the number of coulombs ofcharge. It is referenced to an arbitrary zero reference point. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elevol.html#c1 http://regentsprep.org/Regents/physics/phys03/apotdif/default.htmThe electrical
potential energy between two like charges is proportional tothe amount of charge and inversely proportional to the distance between them. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elepe.html http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/ElectricPotential/PotEnergy.htmlSo to increase the electrical potential energy we can either increase thenumber of charges or reduce the distance between them (for like charges).For unlike charges we need to move the charges further apart to increasepotential energy (an analogy would be moving a weight higher above a planetto increase gravitational potential energy)Firstly let's look at the pos
speed of rotating electrons 2007-10-12 03:18:00 At zero degrees Kelvin, if I were able to stop an electron from orbiting itsnucleus, then I let it go again, would it start orbiting again?If yes – where does the energy come from? Does it reach its fixed angularvelocity instantaneously or does it accelerate? What controls its rate oracceleration?If no – does it just sit there? Does it fall off? Does it fly into space?It is not possible to "stop" an electron in an atomic state.Even at 0 K, the electron will remain in its usual motion.Changing the temperature does not affect the electron's orbit.Temperature is related to the motion of molecules.
"Why do planets spin?" 2007-10-11 04:41:00 "Why do planets spin?" and had us all stumped. Why? Why was the matter that formed the Earth spinning? Why does every-thing in the universe, from galaxies down to atoms, spin? I think it is related to the effect that we haveseen when a skater who has arms extended and is slowly spinning suddenlypulls the arms into the body surface. The result is that spin rate increas-es. To even spin faster the skater will be standing straight with the armsup over the head. This makes the distributions of mass as close toe thespin axis as possible and makes the spin as large as possible. The mainidea is that angular momentum is conserved, i.e., cannot change. Angularmomentum is the product of the spin rate and the moment of inertia (ameasure of the distribution of the mass about the axis of rotation). Theproduct is constant. If mass is widely dispersed as before condensing intoa planet, and is very slowly rotating, then when it condenses into a planet(making a small moment of inertia) the rat
What is an aurora borealis made of and why does it only appear sometimes? 2007-10-11 04:38:00 What is an aurora borealis made of and why does it only appear
sometimes?Why do aurorae appear near the magnetic poles? What is the ionosphere?Aurora Borealis is made of charged particles moving in Earth's magneticfield. These particles emit light as they interact with the ionosphere. These particles are emitted by Sun in small quantities (as compared to Sun'smass) and whenever these cross Earth, we see the display. Solar activityhas an 11 year period so the Auroral activity also varies over this period.The ionosphere is the uppermost layer of atmosphere. It is completelyionized (hence the name ionosphere) by the radiation from the Sun and cosmicrays. Near magnetic poles, the lines of magnetic field (of Earth) enter theatmosphere. Charged particles emitted by the Sun move along the lines ofmagnetic field. Therefore they enter the atmosphere where the lines enterthe atmosphere -- at the magnetic poles. Here they interact with a atmo-sphere and produce Aurora.The Sun is continu
how does the eye focus on a 'to the eye' digital viewfinder 2007-10-20 03:32:00 The short answer is that lens(es) is(are) used to present to the eye an object at infinity, much like a simple magnifying glass works. Our eyes are most comfortable when viewing objects at (or near) infinity, so this arrangement makes for easy viewing. Even pentaprism viewfinders usually incorporate lenses to allow users to see the focusing screen, in the same manner. See the various sketches at photographer.org. Notice that there is at least one lens between the focusing screen and the eye. I have not been able to find any schematics of viewfinders for video cameras but the same principle is used: the LCD (or tube) viewing screen is at the effective focal length of the lens(es) that are between the screen and the eye. On the better viewfinders the viewing lens system can be adjusted for the individual viewer's eye.
Questions on photon 2007-10-17 23:10:00 --------------------------------------------------------------------------------1. What and why changes the shape of the the object as it comes closer to the speed of light.2. Why does the time slow down when something travels closer to the speed of light?3. Why is light absolute from all pts. of references?4. What is the rest mass photon?(since photons can be slowed down if they travel underwater, etc, Is it possible...and what would happen if we can...slow down the photon to 0 velocity from our reference?I do not want mathematical proof...but conceptual answer such as: the reason an object can not travel to the speed of light is b/c it will take infinite energy for it to speed up to there.(why btw?)1) Because all distances in one direction (along the direction of movement) are contracted. You should probably study (special) relativity to understand it.2) Again, you should study special relativity. The effect of time dilation makes clocks in relatively moving frames run slower. You ca
When did the first plants appear? 2007-10-17 09:03:00 The answer is “about 2.5 Billion years ago”.But to answer your question we need to be sure we agree about “When is a plant not a plant”! For example if you believe all living things are either plants or animals, we have to decide what bacteria and viruses are. How many cells have to live together, and do what, to be a plant?Photosynthesis began, on earth, we think, about 3 Billion years ago.The first plants ON LAND began much later – only 475 Million years ago!The timeline is rather interesting:The basic timeline on our 4.6 billion year old Earth, is very approximately: 4 billion years of simple cells (prokaryotes), 3 billion years of photosynthesis, 2 billion years of complex cells (eukaryotes), 1 billion years of multicellular life, 600 million years of simple animals, 570 million years of arthropods (ancestors of insects, arachnids and crustaceans) 550 million years of complex animals 500 million years of fish and proto-amphibians, 475 million years of lan Read more:appear
Why does a hammer fall head first? 2007-10-17 09:01:00 There are a few assumptions to the situation which are not explicitly stated, and one almost correct statement. It is not actually correct that "objects all fall to the Earth at the same speed regardless of mass, providing they are the same shape." It is more correct to specify that they must be the same shape and the same density. The major assumptions are that the hammer is not falling very far, and that the hammer starts with its head down. In fact, because the hammer head and the handle are not the same shape, that's a clue to why the head might fall slightly faster than the handle (If they weren't connected!). I will say a bit more about this later in the answer. But a hammer does not actually always fall with the head first when the distance is small, for instance if you drop it from your hand to the floor. It might do so because of the fact that the heavy head causes a torque (and thus a spin) to the hammer as it leaves your hand on the way to the floor, but if you purposely d
What is the probability of life in Universe? 2007-10-25 10:43:00 at least 99.999 % if you consider the entire observable universe (just an informal guess).but we still might be the only life in our GALAXY, at least that has evolved to the point of being able to measure the speed of light and imagine inhabiting other planetary systems and stuff like that.there are billions of galaxies, and each galaxy contains billions of stars (actually more in both cases, like hundreds of billions, but not to be overprecise)so if life is extremely rare for some reason we don't understand, then it's conceivable that Earth might be the only planet with life in the Milkyway galaxy. (I can hardly see how life could be so rare, but let's pretend we are alone in the galaxy).even then, you still have all those billions of other galaxies. but we may never interact with life in other galaxies because they are so far away. in some sense it seems almost not to matter.what seems to matter to me is what other life and what other civilizations are there in the Milkyway. they Read more:Universe
What is the probability of life in Universe? 2007-10-25 10:43:00 at least 99.999 % if you consider the entire observable universe (just an informal guess).but we still might be the only life in our GALAXY, at least that has evolved to the point of being able to measure the speed of light and imagine inhabiting other planetary systems and stuff like that.there are billions of galaxies, and each galaxy contains billions of stars (actually more in both cases, like hundreds of billions, but not to be overprecise)so if life is extremely rare for some reason we don't understand, then it's conceivable that Earth might be the only planet with life in the Milkyway galaxy. (I can hardly see how life could be so rare, but let's pretend we are alone in the galaxy).even then, you still have all those billions of other galaxies. but we may never interact with life in other galaxies because they are so far away. in some sense it seems almost not to matter.what seems to matter to me is what other life and what other civilizations are there in the Milkyway. they Read more:Universe
Speed of a Gamma Ray Burst 2007-10-24 11:36:00 Gamma-ray bursts (GRBs) "hit" Earth pretty much every day. That's how we know they exist. Space observatories detect the intense temporal gamma-ray emission, then space and ground observatories detect the broadband afterglow (gamma, X-ray, UV, visible, and radio). We observe GRBs frequently, sometimes multiple times a day.We humans don't see GRBs as dim light; our eyes only see visible light, and GRB afterglows are too weak in the visible range for our eyes to see. Gamma-ray detectors see a GRB as the brightest object in the sky, for a very short time (less than a second to a few minutes). There are models that predict that GRBs emit isotropically, that is, the central engine (the source) will emit light in all directions, so we should see it if it's in our line of sight and not too far away. There are also models that predict bimodal beaming, that is, we only see a GRB if one of the two narrow jets are pointed at us.Our atmosphere protects us from cosmic gamma- and X-rays. For a GR Read more:Speed
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BOUNCE IS BETTER THAN BANG 2007-10-23 04:02:00 The Schwarzschild radius of our universe is greater than the present size of our universe. It does not expand. It was always the same size. Changing the position of the particles inside the Scharzschild radius does not change the radius. What those particles are doing does not change the size of the radius. So, if you want to pretend that they all got together and made a big bang or that they all got together and bounced it still does not change the radius of the gravity. (Scharzschild radius)What is important is how far away is another universe. After all, none of them have come crashing into our universe. (A black hole) There is no evidence that even one particle is falling into our universe. Or, ???? is there? (Fred Hoyle would have liked to know.)The universe is expanding into it’s Scharzschild radius and by black hole logic it cannot expand any farther.If you want to use the logic of big bang then gravity cannot spread faster than the speed of light therefore, expansion, inflati
Can resonance explain the origin of the Universe? 2007-10-23 04:00:00 Traditionally the word "resonance" is used when there is an object exposed to some energy source (like an antenna exposed to a field of radio waves, or a nucleus exposed to the fields of passing photons or neutrons). If the object and the source are "tuned" somehow, the object can become very good at absorbing the field's energy. In order to describe the Universe
this way, you'd have to say several things: 1) that there is some energy source outside of the Universe; 2) that the Universe absorbs this energy in some way, and 3) that the absorbed energy has something to do with the observed expansion. Unfortunately we cannot say any of these things; we're not aware of any general energy source; we have no evidence that the Universe is absorbing energy from such a source (either at a "resonance" or otherwise). It is also not clear that it is possible to describe cosmology by saying that the Universe is simply "absorbing energy"---you would have to specify when it absorbs this energy, an Read more:explain
Would a pinewood derby racer go faster if it had more weight? 2007-10-28 08:20:00 Well, itmight go a little faster, because the forcepulling on it (gravity) would be strongerrelative to the air resistance, but I thinkthe strongest source of resistance for pine-wood derby
cars is friction in the wheels,and that should get bigger just as theweight gets bigger. What I would recommendis an experiment - if you can get a slightlysloped surface to race your car down, andtime it carefully. You might find that itwent faster with some extra weight. Youmight also figure out other ways to improveyour car.=========================================================Here are some suggestions thatmight help you out:1) Make sure the wheels are round andsmooth2) If your track starts on an incline,(most do) put as much weightas you can near the rear of the car.You do not want to make it unstable,but you do want as much potentialenergy as possible. It will only helpat the bottom of the track.3) Try to make sure that the axles arestraight.
does the length of a pendulum affect its amplitude? 2007-10-26 11:02:00 The question: "Does the length of a pendulum affect its amplitude? Suppose there are two pendula, both have bobs of equal mass attached to them. But one pendulum has a longer string than the other. Now I know that the length of the pendulum will affect the time period of each. But how can we prove that the length also affects the amplitde? My intuition says that the pendulum with the longer string will have a smaller amplitude." Notice the equation for the total energy of a simple-harmonic-motion (S.H.M.) system: E = 0.5 k A2 where "k" is a force constant that depends on some characteristics of the system (such as a spring) and "A" is the amplitude. The period, "T", of the S.H.M. is T = 2 PI sqrt (M/k) where "sqrt" is the squareroot operation, M is the mass of the oscillator, and k is the force constant. A pendulum with sufficiently small amplitude approximates a true S.H.O. (simple harmonic oscillator), so the equations are approximately applicable for sufficiently small amplitude of
Why have we made only small amount of antimatter? 2007-10-26 11:01:00 Antimatter is being produced all the time. It's one of the interactions of high energy gamma rays with normal matter called Pair Production. What happens is a gamma ray with an energy greater than 1.02 Mev nears a nucleus, and in some cases a positron and an electron appear, each with an energy of 0.51 Mev. The lifespan of the positron is short as it is annihilated by contact with ANY form of normal matter. And, that is the problem with making any large quantity of antimatter: what do you store it in? How can we store large amount of antimatter safely? You can't, at least not on earth. Perhaps in space, but even there, there will be random hydrogen atoms interacting with your antimatter such that it will always be "disappearing". The storage problem is about the same as the problem of containing plasma only worse. Plasma has been contained for short periods in a magnetic bottle, but no practical method of long-term storage has been attempted. Plasma, because of it's high te
How does a CE mode single stage transistor used as an amplifier ? 2007-10-31 09:32:00 The answer lies in the fact that the transistor used in the single
-stage CE amplifier is *biased*; that is, DC levels are established (using resistors) so that the base-emitter junction is always forward biased and the collector-base junction is always reverse biased. The AC signal is then capacitively coupled into the base. This causes a large AC current to flow from the collector to the emitter in accordance with basic bipolar transistor theory and the output is taken from the collector. The AC gain is given by the formula Av = KRc ; where K is a constant (easily determined) and Rc is the value of the collector resistor.
How does a CE mode single stage transistor used as an amplifier ? 2007-10-31 09:32:00 The answer lies in the fact that the transistor used in the single
-stage CE amplifier is *biased*; that is, DC levels are established (using resistors) so that the base-emitter junction is always forward biased and the collector-base junction is always reverse biased. The AC signal is then capacitively coupled into the base. This causes a large AC current to flow from the collector to the emitter in accordance with basic bipolar transistor theory and the output is taken from the collector. The AC gain is given by the formula Av = KRc ; where K is a constant (easily determined) and Rc is the value of the collector resistor.
Can low power laser outputs be combined for greater cumulative output? 2007-10-31 09:31:00 The basic answer to your question is, "yes, but...". There is no fundamental reason why one would not be able to combine two beams of light together, and get an increase in laser power
-after all, lasers are nothing but special beams of light. Furthermore, if we increase the laser power in a point, so does the heat, as heat is simply the energy from the laser being converted. Let's first concentrate on the easiest and most common way of combining laser beams, namely to focus multiple laser beams in a single spot. This way, the spot gets the combined power of all the lasers, and the power density is increased locally. This is for instance performed in laser fusion experiments such as the Shiva laser1. This does mean that the laser power is distributed around the target, rather than focused on the target, which may or may not be better, depending on the goal. For intertial laser fusion, it is the method of choice, and some of the largest and most expensive laser systems are built using t Read more:greater
What would happen to matter if it entered a weaker Higgs field? 2007-11-07 10:42:00 I think the issue here is what is meant by a "field". In particle physics, a field is not something whose "value can drop" . One general-audience description I've seen for a "field" is that of a mattress. Picture an array of springs, all at rest. Now push on the mattress at one point. You create an indentation, and somewhere else on the mattress a spring pops up, making a bulge. The "bulge" is one kind of particle; the "indentation" is another. Those particles can move around the mattress in a wave- like manner -- and if they "collide", they can "destroy" each other. (This is a very loose description of matter
and antimatter, with all sorts of flaws in the analogy). So, if you think of this as a "field", what does it mean to have the value of the field "drop"? I don't know. Different mattresses will produce different kinds of particles, with different masses, charges, and spins. Every type of particle has its own field, including things like electron and photons. So think carefully
What is the proposite of observing the sun spots? 2007-11-07 10:39:00 Sunspots
are small dark areas on the surface of the Sun- They are causedby magnetic storms on the surface of the Sun, and they last for a few days up to many weeks. In an 11-year cycle the number of sunspots varies -every 11 years there are many more sunspots than a few years earlier andsome years later. When there are few sunspots there may even be longperiods with not a single sunspot.Sunspots are a little difficult to see because they are small and theSun is VERY bright. This is why they were not discovered in the Westuntil about 400 years ago by Galileo Galilei. Later it was discoveredthat Chineese and asian astronomers had been aware of spots on the Sunfor many thousand years.YOU MUST NEVER LOOK AT THE SUN DIRECTLY, OR USE AN ORDINARY TELESCOPETO LOOK THROUGH AT THE SUN! You can damage your eyesight forever bydoing this.Safe ways to observe the Sun and its spots are to use a telescope toproject an image of the Sun onto a flat white surface and then focus thetelescope until you can
Can oil and water mix at 0 gravity? 2007-11-08 22:05:00 Gravity really isn't that important in whether or not oil and water
will mix. If we take two fluids that do like to mix (say ethanol and water) and carefully layer the lighter (density 0.8 or so) ethanol on the water, they will, with time, mix evenly throughout in spite of the fact that gravity is 'against' it. This is because the chemical nature of the two materials is such that they readily dissolve into each other. Oil and water, on the other hand, are not happy mixing with each other because their internal chemical natures are pretty different. In a zero-gravity environment, the water will probably form blobules that will bounce around all over before finding something (like cloth) that it can easily wet and soak into, while the oil (which has a low surface tension, usually) will form blobules for a while, but eventually is likely to stick to and coat almost every exposed surface. They won't mix intimately with each other; if a piece of cloth got hit with oil blobs first, the w
If a limiting case black hole was formend from X kg of normal matter 2007-11-15 07:28:00 Once the antimatter
(which has mass) falls into the black hole, it no longer matters that it is antimatter insofar as the hole is concerned. The exact nature of what happens to matter once inside the event horizon is an open question (and one that is, by definition, unobservable and thus guidance to theoretical modles by experimental results can not occur). However, let's just for the sake of argument say that somehow the original matter "survived" in some form reasonably akin to regular, outside-the-event-horizon matter. Then, perhaps, inside the event horizon, the matter and antimatter do react and turn into pure energy (gamma rays). The total mass/energy is still conserved, so that from outside the hole's event horizon, we see nothing different because the hole's total mass/energy does not change. Nor can we ever tell if the reaction took place, because the gamma rays can not escape the event horizon any more than the original matter and antimatter could.
Do any two pieces of matter ever touch, or are they simply repelled from a 2007-11-15 07:27:00 At normal (to us) Earth-surface type temperatures and pressures, the interactions of atoms are almost exclusively between the electron clouds of same, and the very large percentage of the matter
of the atoms (the atomic nuclei) do not interact with each other. You do have a few processes, things like cosmic rays bashing into atomic nuclei in the atmosphere, that have nuclei reacting together, but they are the rare exception. So yes, in general for the conditions we exist in, almost all interactions are between the electron clouds, and not the atomic nuclei. Go to conditions inside a star, especially a massive star, however, and things change. First you have nuclear reactions, and in these atomic nuclei are certainly being brought together close enough to interact via nuclear fusion. Eventually, the star will consume its initial fuel, its core will compress even more and, given the star is massive enough, it will react the core material all the way to iron and then collapse. That collap Read more:pieces
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Is it possible to have an electric motor that has only one pole? 2007-11-13 08:31:00 There are several reasons that motor efficiencies change with angular velocity of the rotor. You are correct that the interaction of the magnetic fields of the rotor and stator is one source of inefficiency, both from the energy losses in expanding and collapsing the fields and in small variations in timing the interactions of those fields. Other sources of efficiency loss are bearing and bushing friction, resonances in the motor at different rotational frequencies, and the natural property of spinning machinery to have a speed where power transfer i most efficient.Your thought of having a single magnetic pole is an interesting one, but so far no one has observed a single-pole magnetic field: they always occur in north-south pairs. It is possible to align the poles in a magnet so that all the same-polarity poles of the stator point, but half the energy stored in the magnetic field of the motor would be wasted, doing no work because it isn't interacting with the rotor. Imperfections as
Is the cosmic wave background unique? 2007-11-13 08:30:00 You have actually asked about two different aspects of the CMB (Which, by the way, stands for "cosmic
microwave background
"!). The CMB is static on short time scales ("short" here means hundreds or thousands of years) if measured from a particular place in the cosmos (Our galaxy, for instance). But the CMB is not static spatially if one were to be at a widely separated place in the cosmos from our galaxy. However, large-scale features of the CMB would not be much different unless one were very very far from our galaxy. It is the same type of question as asking what the universe would look like today at visual wavelengths from different vantage points, because the distribution of galaxies in the universe was determined early in the universe's history and follows in large part the distribution of matter represented by the CMB. Read more:unique
What causes the sound when a piece of paper is torn in two? 2007-11-22 01:27:00 The origin of sound from ripping paper
is an intriguing question… and a current research topic for several groups! It’s not my area of research, but a quick look into the literature indicates that the sound is not molecular in origin. In a 2001 paper, Sethna et al. argue that since the sound emitted demonstrates the same "crackling" behaviour as much larger systems, such as earthquakes, the "behaviour is likely to be independent of microscopic and macroscopic details".Paper is composed of a mishmash of fibres running in different directions. When we rip it, we stress the fibres causing them to rupture. These ruptures release potential energy, which is converted into pressure (or sound) waves. (References: Physicists tell ripping yarns and Acoustic Emission from Paper Fracture.) Read more:causes
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Why don't length contraction and time dilation cancel one another out? 2007-11-22 01:27:00 A hurdle to get over when first learning relativity is the inertial reference frame, sometimes referred to as the observer. If the observer is sitting on the train, the length of the train does not contract. There are numerous references to observers and inertial reference frame in the MadSci archives
What is the practical difference between a star's R, O, and E temperatures? 2007-11-19 01:31:00 First, let's add one more definition of temperature, the gas temperature. This is the temperature you would measure if you stuck a thermometer in the photosphere of a star. (The photosphere is that part of the outer layers of a star where most of the light comes out.) This is a measure of the average speed of motion for the atoms of a gas (or a liquid or solid - but we're discussing stars). From now on I'll call this the physical temperature of a star. Objects of any physical temperature emit light, and the amount of light at each wavelength depends on the temperature. So if we measure the emitted spectrum of an object we have another measure of the temperature, which we can call the radiation temperature. The radiated spectrum for many stars is approximately that of a blackbody. (Links are to articles on Wikipedia, which I have read and which seem quite accurate; they are, however, rather more technical than this discussion.) In particular, the wavelength at which a blackbody emits Read more:difference
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