Spyman

Around a black hole there is an undetectable surface called an event horizon that marks the point of no return. It is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics. http://en.wikipedia.org/wiki/Black_hole The size of a black hole, as determined by the radius of the event horizon, or Schwarzschild radius, is roughly proportional to the mass M through [math]r_{sh}=\frac{2GM}{c^2}[/math] http://en.wikipedia.org/wiki/Black_hole The appearance of singularities in general relativity is commonly perceived as signaling the breakdown of the theory. This breakdown, however, is expected; it occurs in a situation where quantum mechanical effects should describe these actions due to the extremely high density and therefore particle interactions. To date it has not been possible to combine quantum and gravitational effects into a single theory. It is generally expected that a theory of quantum gravity will feature black holes without singularities. http://en.wikipedia.org/wiki/Black_hole General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1915. It is the current description of gravitation in modern physics. General relativity generalises special relativity and Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time, or spacetime. In particular, the curvature of spacetime is directly related to the four-momentum (mass-energy and linear momentum) of whatever matter and radiation are present. http://en.wikipedia.org/wiki/General_theory_of_relativity In physics, mass–energy equivalence is the concept that the mass of a body is a measure of its energy content. In this concept the total internal energy E of a body at rest is equal to the product of its rest mass m and a suitable conversion factor to transform from units of mass to units of energy. If the body is not stationary relative to the observer then account must be made for relativistic effects where m is given by the relativistic mass and E the relativistic energy of the body. Albert Einstein proposed mass–energy equivalence in 1905 in one of his Annus Mirabilis papers entitled "Does the inertia of a body depend upon its energy-content?". The equivalence is described by the famous equation [math]E=mc^2[/math] where E is energy, m is mass, and c is the speed of light in a vacuum. http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. In other words a photon is a little packet of energy which can carry electromagnetic radiation. It is also the force carrier for the electromagnetic force. The effects of this force are easily observable at both the microscopic and macroscopic level, because the photon has no rest mass; this allows for interactions at long distances. Like all elementary particles, photons are currently best explained by quantum mechanics and will exhibit wave–particle duality, exhibiting properties of both waves and particles. For example, a single photon may be refracted by a lens or exhibit wave interference with itself, but also act as a particle giving a definite result when quantitative momentum is measured. http://en.wikipedia.org/wiki/Photon The photon is massless, has no electric charge, and does not decay spontaneously in empty space. ... In empty space, the photon moves at c (the speed of light) and its energy and momentum are related by E = pc, where p is the magnitude of the momentum vector p. This derives from the following relativistic relation, with m = 0: [math]E^2=p^2c^2+m^2c^4[/math] http://en.wikipedia.org/wiki/Photon

That would depend on what kind of mass and how fast it is added, generally I think the star would burn more intense with more fuel. In theory all that is needed is to accumulate enough mass inside the Schwarzschild radius and supernovas sems to be the common way of nature to achieve this.

alpha2cen I think you need to improve on your english, it is very hard to understand what you are saying. Wikipedia says that the fusion process ends before a core collapse in Type II supernovas: Type II Stars with at least nine solar masses of material evolve in a complex fashion. In the core of the star, hydrogen is fused into helium and the thermal energy released creates an outward pressure, which maintains the core in hydrostatic equilibrium and prevents collapse. When the core's supply of hydrogen is exhausted, this outward pressure is no longer created. The core begins to collapse, causing a rise in temperature and pressure which becomes great enough to ignite the helium and start a helium-to-carbon fusion cycle, creating sufficient outward pressure to halt the collapse. The core expands and cools slightly, with a hydrogen-fusion outer layer, and a hotter, higher pressure, helium-fusion center. (Other elements such as magnesium, sulfur and calcium are also created and in some cases burned in these further reactions.) This process repeats several times; each time the core collapses, and the collapse is halted by the ignition of a further process involving more massive nuclei and higher temperatures and pressures. Each layer is prevented from collapse by the heat and outward pressure of the fusion process in the next layer inward; each layer also burns hotter and quicker than the previous one—the final burn of silicon to iron consumes its fuel in just a few days at most. The star becomes layered like an onion, with the burning of more easily fused elements occurring in larger shells. In the later stages increasingly heavier elements with higher binding energy undergo nuclear fusion. Fusion produces progressively less energy, and also at higher core energies photodisintegration and electron capture occur which cause further energy loss in the core, requiring a general acceleration of the fusion processes to maintain hydrostatic equilibrium. This escalation culminates with the production of nickel-56, which is unable to produce energy through fusion (but does produce iron-56 through radioactive decay). As a result, a nickel-iron core builds up that cannot produce further outward pressure on the scale needed to support the rest of the structure. It can only support the overlaying mass of the star through the degeneracy pressure of electrons in the core. If the star is sufficiently large, then the iron-nickel core will eventually exceed the Chandrasekhar limit (1.38 solar masses), at which point this mechanism catastrophically fails. The forces holding atomic nuclei apart in the innermost layer of the core suddenly give way, the core implodes due to its own mass, and no further fusion process is available to ignite and prevent collapse this time. http://en.wikipedia.org/wiki/Supernova

There would still be a duration of time between the two identical configurations. That duration of time is not more nothing or less something, than the distance of space that separates two exactly identical objects.

If the shuttle is in uprised position as like before a take off, would the shuttle's height be longer or shorter if it was standing on the Moon? (and measured from Earths "rest frame")

Light in water slows down because of interactions with the water and not because time in water is slower. Accelerating more will only bring you more into the future from Earths point of view, not backwards.

Extrapolation of the expansion of the Universe backwards in time using general relativity yields an infinite density and temperature at a finite time in the past. This singularity signals the breakdown of general relativity. How closely we can extrapolate towards the singularity is debated - certainly not earlier than the Planck epoch. The early hot, dense phase is itself referred to as "the Big Bang", and is considered the "birth" of our Universe. http://en.wikipedia.org/wiki/Big_bang The Big Bang is not an explosion of matter moving outward to fill an empty universe. Instead, space itself expands with time everywhere and increases the physical distance between two comoving points. Because the FLRW metric assumes a uniform distribution of mass and energy, it applies to our Universe only on large scales - local concentrations of matter such as our galaxy are gravitationally bound and as such do not experience the large-scale expansion of space. http://en.wikipedia.org/wiki/Big_bang

The Arrow of time is still one of the major unsolved problems in physics, we don't know yet.

Between different gravitationally or accelerating frames. Diagram 1. Changing views of spacetime along the world line of a rapidly accelerating observer. In this animation, the vertical direction indicates time and the horizontal direction indicates distance, the dashed line is the spacetime trajectory ("world line") of the observer. The lower quarter of the diagram shows the events that are visible to the observer, and the upper quarter shows the light cone- those that will be able to see the observer. The small dots are arbitrary events in spacetime. The slope of the world line (deviation from being vertical) gives the relative velocity to the observer. Note how the view of spacetime changes when the observer accelerates. http://en.wikipedia.org/wiki/Special_relativity

Martin has an old LQG thread with links, that he has moved to the Trash Can: http://www.scienceforums.net/topic/33315-quantum-cosmologyquantum-gravity-links/

For other frames, the relativistic mass (of a body or system of bodies) includes a contribution from the "net" kinetic energy of the body (the kinetic energy of the center of mass of the body), and is larger the faster the body moves. Thus, unlike the invariant mass, the relativistic mass depends on the observer's frame of reference. http://en.wikipedia.org/wiki/Mass_in_special_relativity

Sorry if I expressed myself badly, I don't seem to find the correct words to use... I agree with what IGGY says: "It's always the same length in its own frame. It is different lengths in different frames." What I ment is that the rod doesn't grow or shrink, it stays the same size in its own frame. It doesn't suddenly change size because someone is observing it from another frame, but it will be of a different size as measured from the other frame. Likewise the rod can't have more than one length simultaneously, it is the observers rulers that are in different scales and therefore measures the rod's length to be different. But it is more than a optical difference, the physics of every frame demands that the rod is of the measured length in that frame to sustain the laws of nature. I guess one could say that the rod would be in a more relaxed or natural state when measured from its own frame when no forces are acting on it and it might be tempting to argue that it would represent the rods true and not 'warped' size, but every other frame are equaly valid or real and in every frame the laws of physics are preserved. There is no preferred frame where measurements would be special or somehow priviliged. Viewing it as multiple realities might help as long as you remember that they are all observing the ONE and SAME story, there is only one rod which all observers are measuring and it only goes through one set of events once. Although they can disagree on the order of events, timestamps and distances, they are still observing the one and same occurrence from different viewpoints.

Observational evidence Theoretical cosmologists developing models of the universe have drawn upon a small number of reasonable assumptions in their work. These workings have led to models in which the metric expansion of space is a likely feature of the universe. Chief among the underlying principles that result in models including metric expansion as a feature are: the Cosmological Principle which demands that the universe looks the same way in all directions (isotropic) and has roughly the same smooth mixture of material (homogeneous). the Copernican Principle which demands that no place in the universe is preferred (that is, the universe has no "starting point"). Scientists have tested carefully whether these assumptions are valid and borne out by observation. Observational cosmologists have discovered evidence - very strong in some cases - that supports these assumptions, and as a result, metric expansion of space is considered by cosmologists to be an observed feature on the basis that although we cannot see it directly, scientists have tested the properties of the universe and observation provides compelling confirmation. Sources of this confidence and confirmation include: Hubble demonstrated that all galaxies and distant astronomical objects were moving away from us, as predicted by a universal expansion. Using the redshift of their electromagnetic spectra to determine the distance and speed of remote objects in space, he showed that all objects are moving away from us, and that their speed is proportional to their distance, a feature of metric expansion. Further studies have since shown the expansion to be extremely isotropic and homogeneous, that is, it does not seem to have a special point as a "center", but appears universal and independent of any fixed central point. In studies of large-scale structure of the cosmos taken from redshift surveys a so-called "End of Greatness" was discovered at the largest scales of the universe. Until these scales were surveyed, the universe appeared "lumpy" with clumps of galaxy clusters and superclusters and filaments which were anything but isotropic and homogeneous. This lumpiness disappears into a smooth distribution of galaxies at the largest scales. The isotropic distribution across the sky of distant gamma-ray bursts and supernovae is another confirmation of the Cosmological Principle. The Copernican Principle was not truly tested on a cosmological scale until measurements of the effects of the cosmic microwave background radiation on the dynamics of distant astrophysical systems were made. A group of astronomers at the European Southern Observatory noticed, by measuring the temperature of a distant intergalactic cloud in thermal equilibrium with the cosmic microwave background, that the radiation from the Big Bang was demonstrably warmer at earlier times. Uniform cooling of the cosmic microwave background over billions of years is explainable only if the universe is experiencing a metric expansion. Taken together, the only theory which coherently explains these phenomena relies on space expanding through a change in metric. Interestingly, it was not until the discovery in the year 2000 of direct observational evidence for the changing temperature of the cosmic microwave background that more bizarre constructions could be ruled out. Until that time, it was based purely on an assumption that the universe did not behave as one with the Milky Way sitting at the middle of a fixed-metric with a universal explosion of galaxies in all directions (as seen in, for example, an early model proposed by Milne). Yet before this evidence, many rejected the Milne viewpoint based on the mediocrity principle. The spatial and temporal universality of physical laws was until very recently taken as a fundamental philosophical assumption that is now tested to the observational limits of time and space. http://en.wikipedia.org/wiki/Metric_expansion_of_space

Well, if you could leave it like this: Then EVERYONE would be happy!

All 3 are correct, none can claim superiority. They are in different environments where the scale of the metric and seconds differs between them. I say again, empty space is not the same as nothing, empty space can be measured in three dimensions: length, width and height. What can be outside of our dimensions? If I say nothing that is NOT empty space, because space only exists within our three spatial dimensions. If there is something outside of space then it includes a new dimension which would have other properties than distance as we know it. I continue to fail to visualize a saddle shaped Universe, but I have no problems whatsoever to imagine a flat infinite Universe and sometimes I can succesfully create an mental image of a closed finite Universe that curves back on itself like a hypersphere. All three of these shapes of the Universe has boundaries built into them that comes with the dimensions but none of them have boundaries somewhere inside space. The local movement would be in the direction away from the center, wouldn't it? And as such we would be able to point backwards and say that the center should be there. I might read through it later, when I have more time. There might be a 'real' cosmos hiding behind our observations but our measurements describe the reality as we perceive it. The rod does not actually change length but it is measured to have different length from different environments and in each and every one of these environments the measured size of the rod describes the reality exactly as it is, in that environment as the observers there perceive it, as such the rod actually have a real different length in another frame. This is where you clearly disagrees with Relativity which claims that it is the local time/space environment that is different. I think our Universe will continue to exist independently of sentinent observers. The box is not moving relative us and as such it is not subjected to lenght contraction like the fast moving rod.

It seems that you either don't undertand the balloon analogy or have changed it to fit your world view, in mainstream science there is no space inside or outside of the rubber, instead all dimensions of space are on the surface, like a hypersphere. But more importantly you missed my point or at least you don't meantion your view of it clearly, the point is that in the first example we would be able to determine from observation that we and our neighbours are moving outward from a center, even if we are in the middle of the membrane and can't see any edges. Can you explain why we wouldn't be able to determine the direction towards the centre in the first example? Relativity don't need any observers, it is not about optical illusions, equal rods would physically differ in size if one was moving fast, accelerating hard or deep down in a gravity well, totally independently to if someone was watching or not. General Relativity has replaced Newtonian physics and we explain gravity with the dynamical geometry of spacetime, were the curvature of spacetime depends on placement of matter and matter moves as curvature dictates. Like you say: "Things would move around on their own and all events would happen without our observation and measurement." Earth don't stop orbiting the Sun if nobody aren't looking, Earths orbit is not an illusion. The curvature of spacetime exists whether we measure it or not, greater mass have steeper curvature than lesser mass and if we would add or remove mass from a body then the spacetime curvature around it would change likewise. The frame of reference is a real physical 'backdrop' which includes the scale of the metric and the rate of clocks ticks. A fast moving rod will not only look shorter to us, it will also fit inside a shorter box while it passes and if it is subjected to some wear it will be preserved for a longer duration. For example, heavy ions that are spherical when at rest, should assume the form of "pancakes" or flat disks when traveling nearly at the speed of light. And in fact, the results obtained from particle collisions can only be explained, when the increased nucleon density due to Lorentz contraction is considered. http://en.wikipedia.org/wiki/Length_contraction A comparison of muon lifetimes at different speeds is possible. In the laboratory, slow muons are produced, and in the atmosphere very fast moving muons are introduced by cosmic rays. Taking the muon lifetime at rest as the laboratory value of 2.22 μs, the lifetime of a cosmic ray produced muon traveling at 98% of the speed of light is about five times longer, in agreement with observations. http://en.wikipedia.org/wiki/Time_dilation I am not an expert on Relativity but as I interpret what you are saying, you seem to think that the effects of Relativity are some kind of optical illusions and from my understanding that is wrong. You can not cherry pick half of a theory and leave out the other parts. Maybe you need to learn more of Relativity and its features before you make any final conclusions and then make a new judgement whether you accept or reject it when you have reached a better understanding. IMHO, I maintain what I said in my previously post, without accepting that distances and durations actually are physically altered in different frames as Relativity predicts, you are in essence rejecting it.

Sorry Owl, but I have a hard time trying to make head or tail of your post, maybe it's a language problem since I am not a naitive english speaker, so I apologize if I have misinterpreted you somewhere. Your view of Albert Einsteins theory of Relativity seems to be more than a philosopical difference of what the mainstream science hold, I don't think you can accept Relativity and still say that distances stays the same no matter of reference frames. I don't think the consequences of constant lightspeed for all observers allows for rigid absolute distances and durations between different frames. Since I was not able to express my question of observations and trajectories good enough, here is a second try: In a rigid not expandable and absolute space, consider the following two examples: 1) One million spaceprobes are gathered together in a spherical swarm around an explosive device, at time zero the device goes off and launches all the spaceprobes outward in all directions from the center. After a certain amount of time each and every one of the spaceprobes starts to take measurements and observations of all other spaceprobes in the neighborhood. 2) One million spaceprobes are gathered together in a spherical swarm and between every adjacent spaceprobe there is an mechanical extendable arm, at time zero all arms extends simultaneously a equal amount. After a certain amount of time each and every one of the spaceprobes starts to take measurements and observations of all other spaceprobes in the neighborhood. In both examples the size of the swarm would grow an equal amount, but in the first example the swarm would be spread out like a hollow shell of some thickness, whereas the swarm in the second example would spread out homogeneously. The Earth could be viewed as one of the spaceprobes that happens to be deep inside the swarm and not able to view far enough to see any edges of such a swarm, but are still able to observe neighbors and measure their distances and trajectories. Do you agree that in the first example we would be able to pinpoint the center and in the second example we could not? Which one of the two examples does best fit with our current observations?

I don't think he ment that inflation was a method for creating a universe out of nothing, I would guess he ment it more like it is an indication of thats how it did happen, although I don't understand how inflation itself can tell whether the BB started from nothing or from something. Secondly the total energy for an infinite universe is more elusive to define than for a finite closed one, however I must confess I don't understand how he can claim that a closed universe must have definitely zero total energy either.

why? Flying the copter in safe areas removes a lot of potential hazards, prevents unnecessary accidents and limits their consequences. We are all responsible for our actions which also includes our pets and property or like in this case our creations. Engineers have to consider the safety of people, property and nature when they build things, and the things need to stay safe even when they get old and might break or even if they are misused or tampered with by someone clueless, in extreme cases they even need to include deliberate sabotage by skilled criminals or terrorists. What do you think would happen if your oversized RC helicopter with reinforced razorsharp steelblades, fully able to chop off a thick metal wire, suddenly malfunctions and with the powerful engine on maximum throttle goes straight into the face of a young child? What would happen if the powerline falls down on innocent persons walking by under it? Do you think people depending on the electric power like the outage when the line gets downed? How do you think the owner of the powerline reacts to having to pay for expensive repairs? Even a much much less powerful copter can crash down on the windshield of a car and cause the driver to loose control with loss of life or injury as result. It can also cause loss of property or economy, like if onle the car get wrecked or if it crashes through a window and destroys something valuable lika a famous painting. Well a lot of ugly things can happen, try to use your imagination to prevent them. Now I don't have much experience of RC vehicles, but we are talking about small toys here and I hardly think a normal RC copter is anywhere close to even cutting a thin metal wire of a few millimeters diameter, not to mention a thick metal wire that can sustain smaller trees falling or leaning onto them. Also electrical powerlines are mounted quite high and streched very hard, the ends of a chopped wire would snap back and not likely fall down close to where the copter crashes.

Good we' ve had a plagiarizing question recently, but that obtained my idea…The transmission similar news to many news groups must more or less be the chaotic language or plagiarizing. The chaotic language is enough easy to pay attention. Writes the very much good transmission similar news is more difficult to realize to many news groups, but it will probably look like many plagiarizing. Right? (http://babelfish.yahoo.com/ Translated from English to Chinese and back again.)

A collision with anything could cause damage to the helicopter, but a wire in a power line is not likely to do more harm than crashing into a large tree, a high building or simply crashing to the ground. My gut feeling is that in most cases a small remote controlled helicopter will only lose control during a minor collision in the air and more severe damage could rise when it crashes down into the ground. A parachute could save the helicoper when something goes wrong but depending on environment it could also make recovery harder, like if the parachute gets stuck on a branch in a tree top or on a TV antenna placed inaccessible on a large building etc.

My point in post #12 was that if the electricity don't harm the birds then it won't harm the copter either. They don't get hurt because they don't cause a short circuit between two lines or one line and the ground. If a bird or the copter touches two lines simultaneously the electric current would go through the body and cause damage, but as long as they only touch one line they are safe since the electricity don't have anywere to go.

Why would metal take more damage than birds and why would the copter take more damage from colliding with power lines than simply crashing to the ground? BTW I think that both building a helicopter from scratch and constructing an autobot simultaneously would complicate things more than necessary.

Birds don't seem to have any problems sitting on power lines, why would your copter take more damage?

If you take only one dimension, then all you have is a line and dots can move along this line to increase or decrease their relative distance, but if the line itself is able to stretch and contract then distances between dots can change without the dots themselves moving. If we curve this lonely dimension we get a circle where the line becomes the circumference, but the dots can still only move along the line, they can not leave their dimension and neither go inside or outside of the circle. The circumference can still be able to stretch and contract and change distances without movement. If you take two of these dimensions and 'glue' them together we get an area where the dots can roam around but they are still not able to leave their dimensions and visit the outside like above or below. Similar when we curve both of these dimensions we get a sphere where the area becomes the surface, but the dots are still not able to visit the inside or the outside, they are stuck in both of their two dimensions on the surface. This two dimensional sphere is like the balloon analogy, when we blow up the balloon the surface need to stretch and distances between stationary dots would increase even if they don't move relative the surface. Now if you take three dimensions and both curve and 'glue' them together, then you would get a hypersphere with a volume closed around similar to the circle and the sphere. If the radius of this 3-sphere would grow then dots inside this space would be able to observe distances between stationary objects to increase, but they can't leave their dimensions and visit the inside or outside, because all three dimensions: front/back, left/right and up/down are curved around so there is no direction pointing toward neither the inside or the outside.