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Janus

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Janus last won the day on October 24

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  1. While there is an argument for putting one more color beyond blue, Newton's reason for adding 2 had to do with his religious belief that the number 7 held a special significance.
  2. Janus

    Black holes

    More correctly, it would have to have this radius with it present mass. As indicated by others here, this won't ever happen. Stars all have life cycles which they follow and the staring mass of the star determines the end state. For example, as our star fuses hydrogen, helium builds up in its core. Eventually, all the hydrogen at the core is used up, the remaining helium cools and collapses. This allows the hydrogen in the shell surrounding the core to fuse. The Sun swells in to a Red giant. At some point after that enough pressure builds up in the core to cause the helium to fuse into Carbon. But that's the end of it. The remaining mass of the Sun just isn't enough to cause the Carbon to fuse. The Sun shrinks, slowly using up its remaining fuel. But it never gets small enough to form a black hole. The forces between the atoms are always going to be enough to prevent this. By this time, the Sun will have lost almost 1/2 of its mass, and will have shrunk to about the size of the Earth (well short of what is needed to form a black hole). If a star is massive enough, it will not only fuse the carbon, but it continue to fuse the elements that build up in its core all the way up to Iron*. Now up to Iron fusion releases energy, which helps support the weight of the star. From Iron upwards, it takes a net input of energy for fusion to occur. With these stars, the Iron core will build up larger and larger. eventually it gets so big, that it is forced to fuse. This sucks energy from the star, which was previously "holding up" the outer layers. These outer layers crash down on to the suddenly shrunken, which cause them to ignite in a huge supernova explosion, both blowing away a good part of the star and exerting lot of pressure on the core, collapsing it even further. If the core is massive enough to start with, it can be compressed enough to reach a point where no known force will hold it up against it own gravity and it collapses into a black hole (if it not quite that massive, the process stops with the formation of a neutron star.) *Keep in mind that this is a somewhat of a "Cliff notes" version of what happens, the actual dynamics are a bit more complicated.
  3. Since my last post, I've done a few more, Each one is a recreation of a matte painting used for the original Star Trek series. All but the last one have an element of "whimsy" added. at the end of the post I've added some comments and notes for each image. 1. Not exactly the reception Kirk and the landing party were expecting. 2. Duck Dodgers in the 23rd and 1/2 century. 3.The "Devil" in the Dark 4. Starbase XI Note: 1. Rigel VII fortress used in "'The Cage" ( first pilot) and later seen in "The Menagerie". It was also later used for Flint's home in "Requiem For Methuselah" My first try at using the "fur" feature of Blender to simulate ground cover/vegetation. 2. Eminiar VII from "A Taste of Armageddon". This was also used as Scalos for " Wink of an Eye". While Duck Dodgers is my self-created model, the other people in the scene are posable models imported from Daz-3D. About the only modifications I made with them were in the poses and coloration of clothing. 3. Underground mining facility from The episode of the same title as the caption. This one was also later reused for "The Gamesters of Triskelion" 4. Starbase XI from "Court Martial". Again, the base figures were imported from Daz-3D, though this time I had to do a bit more to make uniforms for them to be wearing. This one also offered some additional challenges. The perspective lines in the original matter painting were not exactly consistent. So in order to keep things looking as close as possible to the painting, Some of the objects in this scene are not "square".
  4. An object less than 1 tenth the mass of the Moon with a relative velocity of 50 km/sec would have about ~ 9e30 joules of KE, which is some 76 times the gravitational binding energy for the Moon. An extra-solar object would be moving at least 42 km/sec relative to the Sun at Earth orbit distance. At the right approach angle, a 50 km/sec relative velocity with respect to the Earth-Moon system is not unreasonable. The Gravitational sphere of influence( the distance at which its gravitational effect is significant compared to the Sun's) for a object 1/10 the mass of the Moon is actually quite a bit less than the Earth-Moon distance, so I don't see its hitting the Moon as having much of an effect on the Earth's orbit.
  5. The Moon already produces tides in both the Oceans and the Earth itself. If something with a significant amount of energy where to hit the Moon, there are a few possibilities: 1. Moon shatters, but the resultant pieces do not have enough energy to overcome the gravitational binding energy of the Moon. The pieces separate and the then fall back together to reform a moon-massed object. The Moon's orbit will likely be changed. 2. Moon shatters with enough energy to it from reforming but not enough for them to escape the Earth's gravity. The pieces end up forming a ring around the Earth. 3. Moon shatters with enough excess energy to knock the pieces completely free of the Earth entirely. The tidal effects caused by case 1 depends on the new orbit. If the collision alters the orbit so that on average it is closer to the Earth, we would get larger lunar tides, the closer to the Earth it gets, the stronger the tides. For them to be Armageddon scale would require it to get really close. Case two would have the tides caused by the Moon weakening as the ring formed. We'd still have solar tides. This could take a fare bit of time, so I don't see this as being a sudden change. The Earth is already used to being flexed on a 12 hr or so cycle, so I don't see it reacting violently to having this flexing weakening over time. With case three, the Lunar tides would weaken as the debris field gets further from the Earth. Again this will not be fast, and not cause much stress on the Earth. So really, only case 1, where the collision robs the Moon of enough orbital energy to give it a close perigee would produce greater tidal forces. I think it would be difficult for such an impact to have enough energy to lower the perigee significantly without imparting enough energy to shatter the Moon into a ring.
  6. Somehow, He found his way into the ST universe also. (during the course of the cartoons featuring him, the colors of his outfit changed, this is one of the early color schemes)
  7. It's just a new twist on an old running gag.
  8. Thanks this one did give me a few headaches. It turns out that the original artwork had some Escheristic qualities to it, with pipes and columns connecting in ways that that they couldn't in reality
  9. Many Bugs Bunny cartoons began with Bugs popping popping out of the ground expecting to to be at some vacation spot, but instead finding himself at some other remote lcoation. This would result in him pulling out a map and quipping " I knew I shoulda taken that left turn at Albuquerque!" The background here, as noted by Phi for All, is a Litihum cracking station as depicted in the original Star trek series. Specifically, the one on Delta Vega, located at the edge of the galaxy (from the episode "Where No man Has Gone Before"). Risa is a planet from ST the Next Gen known as a prime place to go for R&R. Switching "Aldebaran" for "Albuguerque" was poetic license on my part. The 3D rendering of the station is based on the matte painting used for the episode.
  10. In both cases you would visually record events on the Sun as occurring at a faster rate due to Relativistic Doppler shift. For the accelerating case, this increased rate would start out slow and then increase as your velocity with respect to the Sun increased. What you would determine as actually happening to clocks on the Sun would be different. At a constant velocity you would determine that the Sun's clock was running slow by a constant rate, due to your relative velocity. With the acceleration you have two competing effects: The normal relative velocity time dilation which starts out at zero ( if you started at rest with respect to the Sun) and has the Sun clock run slower and slower as your velocity towards the Sun increases. The other effect is due to your measuring from an accelerated frame, where the Sun clock runs fast by a rate that is determined by the magnitude of the acceleration and the distance to the Sun. Greater accelerations and larger distances both lead to faster Sun clock rate. Assuming a constant acceleration, the changing variable is distance. So this effect would have the Sun clock running fastest when you are at the start of your trip and far away, and decreasing it rate as you got closer. You have to compound the two above effects together to get the net result. So the Sun clock could start off running fast and then transition to running slow during your trip.( though it will always turn out that more time will have past on the Sun clock during the trip than it did on yours.)* * with a constant velocity, less time passes on the Sun clock, but it had a "head start" due to the relativity of simultaneity.
  11. Sorry, that should be The receiver changing its velocity, either with respect to the source or with respect to the absolute frame would result in a change in the measured speed of the light relative to itself Point 1 is like light being bullets where all guns have the same muzzle velocity. Thus as measured relative to any gun, all bullets leave the gun at the same speed. However, if you are moving towards the gun, you would measure the speed of the bullets relative to you as being different than you would if you were moving away from the Gun. Your relative speed with respect to the Gun effects the relative speed of the bullets you measure the bullets having with respect to yourself. If you have two observers, One moving towards and one moving away, they would measure a different speed for a given bullet relative to themselves. If you fire a bullet from a gun, the gun will measure the bullet leaving the gun at c relative to the gun. If you then accelerate the gun and then fire it again, it will again measure the bullet leaving the gun at c. However, as long as you don't change the speed of the target between the firing of the bullets, the target will measure the two bullets moving at different speeds relative to itself. Also, if you don't accelerate the gun but accelerate the target instead, then the target will still measure different speeds for the bullets relative to itself. Point 2 is like all bullets leaving the gun with a fixed speed relative to the air (behaving more like the sound waves referred to by Swansont). Changing the velocity of the gun doesn't change how fast the bullets move relative to the air, nor will it change the relative speed they have with respect to the target, but it does change the speed that the gun will measure the bullets have with respect to itself, if the gun velocity with respect to the air changes. And if the target changes it velocity with respect to the air, then it will measure a difference in the speed of the bullets relative to itself( regardless of what the gun did). An invariant speed means that no matter how much you change the velocity of gun or target, both gun and target always measure the bullets as traveling at c relative to themselves. The difference between Newtonian and Relativistic physics as far as this is concerned is that for Newton, the invariant speed is infinite, and in Relativity, it is finite.
  12. In a Newtonian universe, there was just two possibilities for the way light behaves.* 1. It's measured speed depends on the relative velocity of the source. It may have a fixed speed relative to the source (c), but someone moving relative to the source would measure it as having some other speed with respect to themselves. 2. It's speed is constant with respect to some "preferred" absolute reference frame( like an aether) It would not have a fixed speed relative to either the source or receiver, and its speed measured by either relative to themselves would depend on their relative motion with respect to the absolute frame. Einstein postulated a third behavior. Neither the source nor receiver could measure light as traveling at anything but c relative to themselves, regardless of relative velocity between source and receiver, or any changes in velocity either has undergone. The source measures the speed of light it emits as being c relative to itself, accelerates to a new velocity, emits light and still measures it as being c relative to itself. (this fits option 1 above) The source receives the light and measures it as having a speed of c relative to itself. It accelerates to a new velocity, and still measures the light as having a speed of c relative to itself. (not compatible with either option above. The source changing its velocity, either with respect to the source or with respect to the absolute frame would result in a change in the measured speed of the light relative to itself.) This is what an invariant speed of light means. * assuming light has a finite and not infinite speed.
  13. No. If you plot distance against measured red-shift you get a straight line if the universe has been expanding at a constant rate. If the expansion had been slowing down, this plot would curve slightly in one direction (this is what the study expected to find, and they were interested in how much it curved.) If the rate of expansion where speeding up over time, the plot would curve in the other direction ( which is what the study actually found). It is the equivalent of tossing a ball up into the air on a small moon which you don't know the mass or radius of. As the ball climbs, it loses speed. By noting how fast it loses speed, you can tell if the ball is moving at escape velocity or not. You can tell whether it will eventually fall back down to you or will just keep climbing away. What you would not expect is for the ball to pick up speed as it climbed. This is essentially what the study found. It was because this result was so contrary to what was expected that this study became so important. It's not that it was "unnatural"( anything the Universe does is "natural"), but more that it uncovered something about the universe that we did not suspect. The most exciting words in science are not "Aha, just as I expected!", but "Huh, that's odd!"
  14. Janus

    It's About Trash

    It's run by Waste Management, the same company that does normal garbage pickup. It's covered in our normal garbage fees. The city does regulate them (in order to operate a garbage collection company, you have to do recycling and compost/yard debris). The compost/yard debris is taken to a composting facility and the finished compost is sold to landscapers, agriculture, and residents. Because of the recycling, which is picked up every week, our actual garbage is only picked up every two weeks, and even then, most times my wife and I don't fill the garbage can between pick-ups.
  15. Janus

    It's About Trash

    If I understand correctly, some "compostable" plastics are meant to go to a commercial composting facility rather than thrown in with regular compost. In other words, you can't just toss them in the compost pile with the banana peels and coffee grounds and expect to them to decompose in the same way. Where we live we do have compost/yard debris pickup and you can throw the compostable plastic bags* in with it ( but not other types of compostable plastic items). I think a lot has to do with the thickness of the plastic. *We have a small compost pail lined with one of these types of bag. When full, we just tie up the bag and toss it into the yard debris can.
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