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Everything posted by Janus

  1. The maximum mass for a neutron is star is ~2.17 solar masses, and one that massive would have a radius of ~15 km. The event horizon for a BH with that mass is ~6.43 km, and has a photon sphere at ~9.65 km. At the surface of the Neutron star, escape velocity would be ~ 0.463 c and orbital velocity would be ~0.33 c, both well short of c.
  2. They say it this way when trying to communicate the idea of non-euclidean spacetime to a general populace that has no idea what non-euclidean geometry is. The animation is not meant to represent "reality", it is a "translation" of non-euclidean geometry using euclidean geometry. It is an attempt to represent an abstract concept in a way that is easier to visualize.
  3. Well, for one, the mechanism you use to explain this frequency shift ( quoted above) would not result in the type of frequency shift we see. All these types of interactions are wavelength dependent, meaning that the effect you get from them depends on the wavelength of the light (An example of this type of wavelength dependent effect would be light at the blue end of the spectrum being scattered more by our atmosphere*) Thus you would see different amounts of shift in spectral lines at different points of the spectrum, and not the uniform shift we see across the whole spectrum. It's not enough to say you can relate energy to frequency when the mechanism that you attribute this change to would not produce the results we observe. * In fact, the very mechanism you base your argument on would also produce scattering. We do not see significant scattering in light from distant galaxies. (because, quite frankly, there isn't enough stuff out there between our galaxy and them to produce it. The amount of material a photon passes on its way between a galaxy 13 billion ly away and our galaxy is roughly equivalent to the amount it passes crossing 1 meter of air at sea level.)
  4. Exactly, a lot of this background on " how things work" on a starship(BTW, the info I provided came from the Star Trek The Next Generation Technical Manual by Rick Sternbach and Micheal Okuda ) are loose guidelines to maintain some continuity, but they are not allowed to get in the way of a good story line.
  5. Most likely by magnetohydrodynamic generator. Where you pass plasma through a magnetic field to generate electricity. This seems to fit with other nomenclature in the franchise. There are references to the EPS (electro plasma system), which seems to be how they tap energy for running ship systems from the PTC (power transfer conduit), which contains and carries plasma from the matter-antimatter reaction chamber to the warp field generator coils.
  6. Moon's don't just "fall" or "lose orbit", as that is not how orbits work. As far as arriving at a conclusion via "common sense" goes, in my experience, it very often is actually arriving at a conclusion by starting with insufficient or just plain incorrect information, and then applying faulty logic to it.
  7. And then there is the fact that Pangaea is just the most recent of a series of super-continents that formed and then broke up.
  8. The second image is an analogy which visualizes space as being 2 dimensional and bent through a third dimension. It is not representative of reality. In it all of space is the surface shown as a grid. And while the diagram shows the Sun and planets as solid objects sitting on that grid, they would better be represented as circles on the surface. Like already stated in order to make it simpler to present, 2 of the spatial dimensions are removed. Here's am animation that gives an idea of what this same analogy would look is you included the other two dimensions The other thing to keep in mind is that the "Curvature" of space-time is not an actual bending of anything. It is a term used to convey the idea that space-time deviates from the rules that govern Euclidean geometry in the presence of mass. It is called curvature because it gives results like those you would get if you try to do plane geometry on a surface that is not flat.
  9. To build on exchemist's point. Let's assume your flywheel is a magnet, and you've placed a coil nearby, but not touching it in any way. Essentially making a "frictionless" generator. Your flywheel will continue to rotate unabated until you attach some type of load( say a light bulb) to the leads of your generator. When you do this, current begins to flow through the wires including the coil. This, in turn turns the coil into an electromagnetic, the polarity of which will apply an opposing force to the flywheel, slowing it down. Keep the light hooked up long enough, and the wheel will stop spinning entirely. Even there were no losses in the system, the total light energy produced by the bulb could only ever equal the total KE stored by the flywheel (which you would have had to have added to spin it up)
  10. The point is that this "down" is the same for everything in the solar system and they all react equally to it. While the planets do "fall" towards the center of the galaxy, they do not tend to do so any more than the Sun does. The solar system is so small compared to the distance to the center of the galaxy, that any difference in gravity acting over it caused by the galaxy's mass is insignificant. ( a quick calculation indicates that some nearby stars would have a larger effect.) Secondly. Even if there was a measurable differential across the solar system, it would not cause the orbital plane to align with it. The solar system is a rotating structure, and when you apply a force in order to try to change the axial orientation of a rotating structure you get a precession instead. (the axis "wobbles") Now, since the rate of this precession depends on a number of factors, including the angular velocity of the rotating structure, and each planet orbits the Sun at different angular velocities, each planet's orbit acts as a singular rotating structure with its own independent precession rate. Thus, over time, you would end up with planets orbiting at all kinds of orientations to each other and not nearly in the same plane as we have now. The fact that all the major planets, for the most part, share the same orbital plane shows that there has been no significant force acting on it in this way. If Saturn's rings were oriented toward the Sun, then we would not see them as well as we can from Earth (since we'd always be looking at them nearly edge on.) Sure, twice an orbit, the ascending or descending nodes of the rings align with the Sun, But since the ring orientation remains nearly fixed relative to the stars as it orbits, this has to happen no matter how they are oriented.
  11. The only effect the gravity well of another body would have on the orientation of the orbital plane of our solar system would be through tidal forces( the part of the solar system closest to the body being pulled on more than the part further away)* Tidal forces fall off by the cube of the distance. This means that the mass causing them generally need to be fairly close. For example, even though the Sun is nearly 27 million times more massive than the Moon, the fact that the Moon is 1/400 the distance of the Sun results in it having the larger tidal effect on the Earth. There are no bodies with the right combination of mass and distance to produce any significant tidal effect on the Solar system. The galaxy itself is very massive, but its center is so far away that, for all intents and purposes, all parts of the solar system are an equal distance from it. The perihelion and aphelion of the various planets do shift over time, but that's due to interactions between the planets themselves. They also do not line up with each other. In addition, while the major planets do tend to orbit in almost the same plane, there are plenty of bodies that do not, asteroids, comets, etc. Comets in particular have large, very elliptical orbits, and because of this, they would be much more prone to be effected by external tidal forces acting on the solar system as a whole. We do not see any pattern to them that would suggest that they are being effected in such a way.
  12. To expand of swansot's post: When you look at the spectrum of a distant light source like a star or galaxy, the spectrum will contain bright and dark lines. These are the emission and absorption lines from the different elements in the source. Every element has a distinct pattern of lines that occur at a particular point of the spectrum. If the light from the source is absorbed/scattered, you will see a dimming of a certain part of the spectrum, but those lines will still be there, in the same pattern and same part of the spectrum because all that is happening is that you are receiving a smaller proportion of light from one end of the spectrum. With red/blue shift, what we see is all these spectral lines shifted to new positions in the spectrum. So for example, a pattern that normally is in the yellow part of the spectrum will move towards the orange. You may not even notice much of a change in the overall "redness" or "blueness" in the spectrum as a whole, as non-visible frequencies shift into the visible at the red end, and visible light at the blue end shifts into the non-visible range.
  13. Masks serve a dual purpose: Protection of the user from others who may be infected, and protection of others from the user if he/she is infected. And of the two, they are more effective with the later. Valves in the mask work to defeat this by allowing more water droplets to escape the mask. People need to to stop thinking of masks in terms of something they wear to "just protect themselves", and more as something that we, as a community, should wear to protect each other.
  14. 10,000 meters in the track frame. If the lightning strikes occur 100 m apart in the train frame, then scorch marks they leave on the tracks are 100 m apart as measured from the train frame. Since the train measures the track as being length contracted by the same factor ( 1/100) as the track frame measures the train, then the proper distance between the scorch marks as measured from the track frame is 100m x 100 = 10,000 m. Of course this means that the rear of the train ( being only 1 m long as measured from the tracks) reaches the point on the tracks where it and the tracks are hit by lightning while the front of the train is still 9,999 m short of where it will be struck by lightning, making the lightning strikes non-simultaneous in the track frame.
  15. While a Moon's tidal influence can dominate, the star will have a tidal influence. For example. Let's start with a planet-moon system tidally locked to each other, The star will still will still produce tidal effects that will produce drag on the Planet's rotation. If this were allowed to happen, then the Moon would orbit faster than the planet rotates. In this situation, the Moon would spiral in, transferring rotational energy to the planet, speeding up its rotation. So what happens is while the Moon does end up keeping the planet tidally locked to itself, it does so at the expense of it's own orbital energy. Both it's orbital period and the rotational period of the planet shorten. However, this can't be maintained forever, as eventually the moon would spiral inside the Roche limit and break up. How long this would take depends on the tidal influence of the star. For example, Proxima Centauri B orbits so close to its star that the stellar tidal forces on it are roughly 1000 times that of the Sun on the Earth.
  16. Magnetic fields have polarity. You have a North and South pole. Like poles repel each other and unlike poles attract. The poles always occur in pairs (a magnet will always have both North and South poles) Because of this, it is possible to arrange the poles in such a way that all the poles cancel each other out and you get no net attraction or repulsion. Gravitational fields have no polarity. They are purely attractive; mass attracts mass. The more mass, the greater the attraction. There is no way to arrange things to get a repulsion or cancellation. But, compared to magnetic fields, gravity is very weak, and it take a considerable amount of mass for this attraction to be easily measured. But, as swansont has already noted, we have measured gravitational attraction between relatively small masses. The earliest such measurement was done by Henry Cavendish in 1797. He took two brass* spheres which were placed on the ends of a long rod which, in turn, was hung from a piano wire at its midpoint. Two more larger Brass spheres were placed near the suspended spheres so that any attraction between them would rotate the rod and twist the piano wire. Then, by measuring how much rod rotated, and knowing how much torque it would take to twist the wire by that amount, he could work out just how much force was attracting the spheres to each other. And since he also knew the mass of the spheres, he was able to derive the constant of proportionality for gravity. This, in turn allowed him to work out the mass of the Earth. Up until then, while we could measure how much gravitational force there was between the Earth and an object of a known mass, and we knew how far the object was from the center of the Earth, we were still left with two unknowns: the mass of the Earth, and the gravitational constant of proportionality. Knowing either one would allow us to work out the other. Cavendish's experiment gave us the value of the gravitational constant, which meant he could now calculate the Earth's mass. Because of this, Cavendish has been referred to as "The man who weighed the Earth". *he used brass as it had no magnetic properties that could have skewed the results.
  17. When we say that gravity has an effect on time, it is important to understand, that is a difference in gravitational potential that is important and not any difference in local gravity strength. A clock at the top a mountain runs faster than one at sea level because it is higher in the gravity well of the Earth, not because gravity is a bit weaker there. If fact, if gravity didn't decrease with altitude, and remained the same at the mountain top as at sea level, not only would the mountain clock still run faster, but the difference between its tick rate and the sea level clock would be even larger. This is despite the fact that both clocks would experience exactly the same magnitude of gravity.
  18. I'm going to focus on this, Others have already explained that you would see the both the Moon and smaller Sun as they were ~8 min prior to the moment you see them. But, just because you "see" them that way, doesn't mean they are in a "different time-frame" from you. So, for example, if the Moon has large clock face on it, and you, from your position, see it reading 11:52, while your clock reads 12:00, you can't conclude that is is 11.52 on the Moon when your clock reads 12:00. The Moon clock ticked off 8 min in the time the light reflected off it left. So, When you see it read 11:52, it actually reads 12:00 just like your own clock. The reason I bring this up is that you mentioned Relativity, and many people get confused about this. They think time dilation etc, is all just related to what we visually see. This is not however the case. In Relativity, we factor out any time difference caused by the time it took the light to travel the intervening distance, and are only concerned with what is left over after that. With your Moon example, we, for the sake of making it simple, assume that the Moon is not moving relative to you, and are ignoring any effects caused by gravity. In this case, there is no net time difference between you and the Moon ( even though the image you see of the Moon is ~8 min delayed)
  19. I've seen a few YouTube videos discussing its release. It seems that the PC requirements for installing it are quite stringent. Only pretty recent CPUs are compatible. (Microsoft has release an "approved CPU" list). MS had also put out a "Health Checker" do you could see if your PC was up to the task, But the backlash from it telling so many people that their PC couldn't run Windows 11 caused them to pull it. Out of curiosity, I checked my CPU against the approved list, and it was on it (my PC is less than a year old), But like @StringJunky, I'll think I'll wait and see.
  20. This is what the Moon as a mirror would look like viewed from the Earth with a telescope. That small bluish dot in the center is the Earth's reflection.
  21. Hal Clement wrote a short story dealing with telepathic aliens communicating with Human. The basic outline was a spaceship containing renegades from their own race, has to do a forced landing on Earth. They are a telepathic race. They land in a remote place where they contact a single human, and they spend a good time learning how to read and interact with his mind. (The idea being that once they learn to do this they can use it to control all humans. And their plans were not good. Once they succeed with this one person, they try and implement their plan, only to have it fail. The problem was, that Humans, not being a naturally telepathic race, had thought patterns that varied from individual to individual. The mental link they had formed with the one human didn't translate into forming it with any others.
  22. Since a TASER doesn't use the Earth ground as part of its circuit, touching a metal pole while being hit by one will make no difference. If the TASER hits the pole: For one thing, the darts won't stick and would glance off, and even if they stuck, the circuit would be completed through the pole and not the person touching it, so they would not be effected by it.
  23. Your last fact is open to what definition of "day" you use. You are using the sidereal day or the rotation relative to the stars. However, the usual use of "day" refers to the Solar day which is the time it takes for the Sun to go from noon to noon. Since Venus' rotation is retrograde (its rotates in the opposite direction to that it orbits the Sun, it's Solar day is only 116 day, 18 hours long.
  24. The disparity between the clocks at any given moment fully depends on the the Frame of reference from which it is being measured. There is no "universal, actual" disparity. The importance of bringing the clocks back together is that this produces a situation where all reference frames agree on the exact amount of disparity between the clocks. In other words, all frames agree that the clocks read the same when initially separated, and all frames agree on the difference between the clocks when reunited, but they will not all agree as to how the difference between the clocks accumulated during the period between those two events.
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