Janus

Okay, Here's what's happening. Density is mass divided by volume. We can easily find the mass of a black hole, but how do we find it's volume? We can't see anything inside the event horizon. So it is common to define the size of a black hole by its event horizon or Schwarzschild radius . The Schwarzschild radius is the distance from the center of the black hole where the escape velocity equals c. If you compare the Schwarzschild radius with the mass of a black hole, you find that there is a 1 to 1 ratio. If the mass doubles, the radius doubles. Since volume increases by the cube of the radius, as the black hole grows, its increase in volume outpaces its increase in mass, thus we can say that its density decreases. The thing to realize is that the event horizon is not a physical thing, it is just a boundary between what can and cannot escape the black hole. So when we say the density of the black hole decreases, we are comparing the volume defined by the event horizon compared to the mass. it is the "mean" density It says nothing about how that mass is distributed within that volume. We do not consider the mass of the black hole as evenly distributed throughout its volume, but as concentrated at the center. Imagine a lead ball at the center of an inflated balloon. We can inflate the balloon and make it larger, causing the mean density of its interior to go down, but this does not mean that the density of the lead ball itself has changed.

Start with a massive star. At the beginning, the pressure at the center causes it to fuse hydrogen into helium, this releases enough energy to hold the stars upper layers from collapsing further. After a time, this helium ash start to "clog up the center" and the fusion drops off. The star starts to collapse a little. The pressure builds up in the center until it becomes high enough to cause the helium to fuse. Now you Have helium fusing at the core and a layer of Hydrogen fusing above that. The Carbon from the Helium fusing in turn clogs the center. More collapse, more pressure, and the carbon starts to fuse. This continues until Iron forms at the core. Up to now, every stage of fusion produced extra energy to help hold the star up. Though each stage produces less energy than the last. However, Iron is different, it takes a net input of energy to fuse Iron. The Iron just sits there building up, with fusion taking place in the layers above. Eventually, the Iron core becomes so massive that it can't support the weight of the layers above anymore. It collapses, leaving a hollow that all the upper layers rush to fill in. When they crash into the remnant of the iron core, the forces are enough to cause the whole shebang to fuse in a titanic explosion. This causes forces of it own. In one direction, it forces the outer layers outward. In the other, it pushes inward on the core remnant.(It also produces enough energy to force the fusion of elements heavier than Iron, which is where the heavier elements in the universe come from) If the star is large enough, this pushes the remnant past the point where it becomes a black hole. Some of the star escapes outward while some is absorbed by the Black hole. You get an expanding cloud with a black hole at its center.

In theory, it works. You stop the Moon in its orbit, apply a thrust to it that exactly counters its tendency to to fall to Earth, and you have a gravity tug. The problems: 1.The exhaust gasses will be directed at the Earth. Some of them will fan out enough to miss, but the rest will hit the Earth, robbing it of thrust. 2.The thrust needed. At the distance of the Moon the acceleration due to gravity is 0.0029 m/s². Now this might not seem like much, but it has to be multiplied by the moon's mass to get the required force which is 2.1315e+20 N. For comparison, the Shuttle has a thrust of 30 million N. So it would take the thrust of 2e+12 shuttles to provide the needed acceleration. The surface area of the moon is 3.8e+13 m², only half of which you would put your rockets. This means that you would have to squeeze 1 shuttle per every 2 square meters of the Moon's surface to provide the needed thrust. I use the shuttle because it is one of the highest thrust rockets made. Of course, chemical rockets are way too inefficient for our purposes (after all, just because we are using the Moon to Pull the Earth doesn't mean that it will take any less energy to move the Earth) Ion engines help with efficiency, but at the price of a lower thrust. If you can't squeeze enough shuttles onto the Moon to do the job, you'll never squeeze enough ion engines onto the moon. 3. You still need the same amount of reaction mass for any given type of engine. since the Moon only masses 1/81 that of the Earth, ion engines would use up that mass before we got to escape velocity. So once again, without a revolutionary new propulsion system, we come up short of doing the job.

That's about what I come up with.

Then we won't worry about it that would make things damn near impossible, I'll explain below. It can be determined by using the rocket equation: [math]\Delta V = Ve \ln(MR)[/math] A problem here is that in order to do matter to energy conversion you need to combine matter and antimatter. Since we have no supply of antimatter, we'd have to make it, and it takes more energy to make it that we'd get out of it.

That figure was obtained by finding the escape velocity from the Sun at the Earth's distance and then subtracting the Earth's orbital velocity. Then you find out how much energy it takes to get a mass the size of the Earth up to this speed. Note: it does not matter how you move away from the Sun, this is the amount of energy it will take. This is also a lower limit, assuming 100% of the energy is converted to Earth movement and no losses. That also assumes that you are applying that energy in the same direction as the Earth orbits. With your plane of placing the engines at the South pole, you lose this advantage, increasing the amount of velocity change you'll need. You can't use the Sun to boost our velocity. (I assume you are thinking about a gravity slingshot, and they just don't work like that.) You'd have to use a body that has a velocity with respect to the Sun, like Jupiter. Now while it would be possible to use Jupiter in a slingshot maneuver to trim some of that energy in theory, it is not very practicable. You'd have to swing pretty near to Jupiter to get a good boost, and since Jupiter is some 26973 times more massive than our Moon you are going to get some huge Tides.( as in continent swamping). Since your propulsion system is a action-reaction system, you will have to figure in the reaction mass into the problem. Now, assuming you only have to achieve that minimum velocity change mentioned above, and you could achieve a exhaust velocity of 10% of c(much better than anything we can achieve now), then you would exhaust all of the Earth's oceans as reaction mass before you got up to solar escape velocity. And that is not factoring in the fact that you are going to lose some of the effect of the exhaust velocity due to the fact that it will lose energy climbing out of Earth's gravity. And that is not even considering the climatic effect of punching matter through the atmosphere at 10% of c. Assuming that your propulsion system was 99.9% efficient, this means it would still end up pumping 12,000 times the total energy absorbed by the Earth from the Sun in a year into the atmosphere. All in all, not a practicable exercise. Merged post follows: Consecutive posts merged The difference here is that they are talking about incrementally moving the Earth out from the Sun over 100's of millions of years.

The reason that particles increase in inertia as they reach the speed of light is because they have gained energy, and energy itself adds to the inertia of the particle. If you have some device that accelerates a mass to near the speed of light, that object itself is a part of the system, and the energy stored in it needed it accelerate the mass adds to the inertia of the system. The total inertia/momentum of this system will not change if you accelerate the mass. So no, you cannot create momentum this way; its conservation still stands.

Yes, the higher person will hear the lower one talking slower, and the lower one will hear the upper one talking faster. However, unless the gravitational potential between them is really large, this difference is going to be really small.

Time dilation takes effect at any speed, it is just that it takes high speed for it to become significant. For instance: At 30 km/sec (.01% of c) the dilation factor is 1.00000005 at 1% of c it is 1.00005 10%c = 1.005 50%c = 1.15 75% = 1.5 90% = 2.29 99% = 7 99.9% = 22 99.99% = 71 etc. So if you were trying to get to Andromeda, accelerating a 1g halfway there and then decelerating the rest of the trip , it would take about 19 yrs, for you, and you would reach a top speed of 99.9999995655% of c. The trick is finding a propulsion system that allows you to reach those speeds while using a reasonable amount of fuel.

To go from geostationary orbit to one that would brush the atmosphere requires a delta v of about 1.5 km/sec. A tiny nudge would just put into an elliptical orbit with a slightly smaller period(it would no longer be geostationary) and with a perigee a little closer to Earth. It takes the 1.5 km/sec change to get that perigee to be within the Earth's atmosphere.

But only if placed on a Ley line.

Nobody feels time dilation. It is something that you measure as happening to someone else. You can never say which twin is "really" moving. Since both points of view are valid what decides which one's time dilation is real. Or maybe how do they tell wich one is moving so that only one experinces time dilation? One twin stays in the same inertial frame, the other changes inertial frames. This is important. One of the effects of Relativity is the "Relativity of Simultaneity" Imagine two clocks, one with the "stationary twin" and one at the point where the "traveling twin" turns around to make the return trip. According to the Stationary twin, these tow clocks read the same time. However, according to the traveling twin on the outbound trip, the clock at the end point reads a later time than the stationary twin's clock( for example if the stationary twin's clock reads 2009, the end point clock would read sometime in 2010. Both clocks run slow according to him. When he reaches the endpoint, he stops ans heads back toward his brother. At this point he has changed inertial frames, and in his new inertial frame, it is the stationary twin's clock that reads later than the end point. So if for instance the endpoint clock read 2011 and the stationary twin's clock read 2010 when he first reached the end point, the endpoint clock will read 2011 and the stationary clock will read 2012 after he turns around. by his reckoning, the stationary twin;s clock jumps forward 2 yrs as he himself changes frames. If you add up the time that elapses on the Stationary twin's clock; running slow on the outbound trip, jumping forward on turnaround, running slow on the return trip, more total time elapses on the stationary twin's clock than on his when they meet up again. The stationary twin, who never changes inertial frame, just sees his brother as aging slower during the entire round trip. I am sorry if this is stupid way of looking at it but it's the best I can do.

Newton's law of F=maEvery thing has inertia, or the tendency to keep doing what it is doing. If it is sitting motionless, it stays motionless until you apply a force to change that. This inertia is related to the mass of the object. (In one way it is this resistance to change of motion that defines the mass of the object). The more massive the object, the harder it is to effect a change. On the Earth, there are other forces (friction for example) that also have an effect. So if you want to move a large refrigerator, you have to overcome its inertia and the friction between it and floor. In this case, the friction is the larger of the two. If you stop pushing on the refrigerator, it stops moving because the friction drags it to a stop. I assume you mean vacuum, not non vacuum. If you you eliminate friction, you still have to overcome inertia. You still have to apply more force to get a massive object to move a given speed than you would to get a smaller object to move at that same speed. The difference will be that once moving, there is nothing to stop the object from continuing to move, and it will keep going until another force is applied to change this. One point, this has nothing to do with gravity, as the other poster said. However, gravity can provide the "force" which alters the object's motion.

Frederik Pohl takes an interesting twist on on this in Wall Around a Star. In it, he uses tachyon transmission for teleporting over interstellar distances. The rub is that you only send a copy; the original stays home. The moral dilemma comes in the fact that the copy can never return home, and in the story gets sent somewhere that is not too desirable to be. Thus when you use it, you are exiling a version of "you" to a distant world. Also, when the original steps into the device he does so with the expectation that he will just step back out without have gone anywhere, so the when the copy steps out of the other end with that same expectation, only to find himself on another world, it is quite a shock.

This video is a version of the light clock scenario. The "resolution" is time dilation. Light must travel at c regardless of whether you are in the ships or watching them go by. Since the path taken by the light is longer for the observer watching the ships go by, it takes longer than 1 sec to traverse the path for him. What this means is that the same time period that the ship's measure as one second, the external observer measures as being longer than one second. As far as the external observer is concerned, time runs slower for the ships. One point. The ships cannot travel at the speed of light, only at some speed less than c.

Ib order for that to be true, there would have to be a fixed, absolute frame of rest against with one measures their speed. But, modern day particle acclerators bely that assumption. Consider this. If there is a fixed frame of rest, the Earth moves with respect to it. Today's particle accelerators can get electrons up to very high fractions of c. If the particle accelerator is pointed in the direction of the Earth's motion these two velocities will be added together. If it is pointing in the opposite direction, you will get the difference for the final velocity of the electron. This woud mean that particle accelerators would get different results, depending upon which direction they were facing. They don't. No matter what direction they point they get exactly the same results for any particles moving at the same speed with respect to the Earth.

Wrong. The model of the atom with electrons whizzing around the nucleus like little planets was abandoned decades ago. Even if the electrons orbiting the nucleus model were accurate, the electrons would not be using or losing energy. Their energy would remain constant. Nothing is needed to keep them orbiting, their own inertia would do that. If they lost energy, it would be at the expense of their speed and they would spiral in to the nucleus. (Actually, it is for this reason that the orbiting electron model was abandoned. Being electric charges, orbiting electrons should radiate. if they radiate, they give up energy and after a very short time would fall into the nucleus. Since atoms neither radiate nor collapse, electrons can't be classical bodies orbiting a nucleus)

But physics itself does demand that PM of the the type you are discussing is impossible. In your first post you said that energy is never destroyed but only changes to other forms. This is true, but only a part of the story; neither is energy created. Let's use an example: Energy is money, and for simplicity, let's say the different forms are check, cash, and in an account. You can convert from one ot another, but you start with a fixed amount in total. As long you you don't spend any of the money, The amount will stay the same. What PM devices claim to be able to do is essentially this: By being real clever in the order in which you convert the money between different forms, You can end up with "extra money"; Money you can spend without reducing the amount of money you have. Remember, no money is coming in from an outside source, you are just moving the money you have around. This, of course, is silly. If I have X number of dollars, just moving it around will not change how much I have. And this is not even considering the fact that, in real life, there would be transaction fees, etc. Just by moving the money around, you would be slowly depleting it, without getting anything for the money you are losing.

The force acting between poles of two magnets is proportional to the product of the strength of the two poles. IOW, if one pole is 1 and the other is 1, the force is 1x1=1, if one pole is 1 and the other 2, the force is 1x2=2, if one is 1/2 and the other is 2 the force is 1/2 x 2 =1. This is the force acting on both magnets. There is no stronger force and weaker force, there is only one force due to the combination of the two poles.

It won't work. What will happen is that the magnets on the rotor will just settle in positions halfway between the outer magnets. But what you really have to ask yourself is: If free energy were as simple to achieve as this device, why hasn't anyone one else already built one? Magnets have been around for a long time and there have been some pretty clever people during that time. The truth of the matter is that this is not anything new. I can't count the times I've heard this idea already.

The presence of mass or energy warps space-time. The result of this warping is what we call gravity. Gravity doesn't affect time, it is the warping of space-time by mass and energy that is gravity.

There are a lot of factors that have an effect on the Earth's orbit, so there is actually more than one answer to that question. For instance, during the period of 1800-2050 AD, the Earth's orbits on average increases in size. However, during the period of 3000 BC- 3000AD, it on average decreases in size On this time scale, a contributing factor is that the Sun loses mass as it ages, which would tend to increase the size of the Earth's orbit.

Let's see, the best telescope has a resolution of 0.05 arc sec. This means that looking at a galaxy 200 million parsecs away, the smallest "piece" of the galaxy that it can resolve is about 5 parsecs across. A parsec is 2.26 light years and A light year is 9,460,800,000,000 km, so 5 parsecs is 153788544000000 km The Hubble constant which determines how fast an object is moving away from us is 75 km/sec/million parsec. So a galaxy 200 parsec away would be moving at 1500 km/sec. That means over a two week exposure, the galaxy will have moved 1,814,400,000 km. This is 1/847787 of the smallest part of the galaxy that the best telescope can resolve. So it would take a exposure time of over 32,000 years for the galaxy to move enough to produce a blur that could be resolved by our telescopes. Picking a further galaxy to get a higher speed of movement doesn't make any difference because you are also increasing the size of the smallest bit of the galaxy that can be resolved by the same factor.

Ignoring air drag and wind, there is another thing to consider. At such a range, the curvature of the Earth comes into play. Using your example with no wind and no drag, you get a time of flight of 288s, and a horiz speed of 1414m/s for a distance or 408,040 m To take curvature in to account you have to do it somewhat differently. You have to treat the trajectory as a highly eccentric orbit which intersects the Earth's surface at two points. To do this, you need to find the semi-major axis(a), period(P) and eccentricity(e) of said orbit. You can find "a" by noting that the total energy of the bullet at launch is: [math]E = \frac{mv^2}{2}-\frac{GMm}{r}[/math] Where m is the mass of the bullet, G the gravitational constant, M the mass of the Earth, and r the radius of the Earth(from where the bullet is fired.) And also is: [math]E=-\frac{GMm}{2a}[/math] Combining these two equations eliminates "m". So using 5.97e24kg for M, 2000 m/v for v, and 6.673e-11 for G we get: a=3294489m P can be found by [math]P= 2 \pi \sqrt{\frac{a^3}{GM}}[/math] thus P= 1882. sec e can be found from the expression: [math]\frac{Ar}{2}= \frac{ \pi a^2}{P} \sqrt{1-e^2}[/math] where A is the Areal velocity, which in this case is the horizontal velocity of the bullet. solving for e gives us: e = 0.96852 The focus of this orbit is the center of the Earth. We can find the radial vector (distance from the focus) at any point of the orbit from: [math]R = a \frac{1-e^2}{1+e\cos \theta}[/math] Where theta is the angle between perigee and the point of the orbit. From the information we have, we can rearrange and solve for theta when R = 6367000m (the radius of the orbit) . Subtracting this from 180° and doubling it gives us the arc it covers during its trajectory. This comes to 3.79°. There are 111317 m to every degree on the Earth's surface, which gives a total distance traveled of: 421,798 m compared to the 408,040 m you get neglecting the Earth's curvature. Note that the above doesn't take into account the Earth's rotation. To do so, you have to adjust v and A accordingly. For instance, for firing Eastward at the Equator, you adjust A to 1414+464 =1878 m/s and v to [math]\sqrt{1414^2+1878^2} = [/math]2351 m/s Which increases the range to 574,509 m. Firing Westward decreases it to 278,192 m

7 days, 2 hrs, 7 min and 53.36 sec