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 Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...The Space and Astronomy Agora Re: Re: Re: Polar Jets Of Neutron Stars (NS) And Black Holes (BH). Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response ToPosted by Alexander on January 31, 2001 20:45:05 UTC

Well, even c+c=c, meaning that there are no superluminal velocities for materialistic object.

What they saw using VLART (very large array of radio tewlescopes - with base of several thousand miles) as a superluminal is not a jet or a quazar, or any other materialistic object.

It is the following phenomena. Some black holes and neutron stars have visible envelope (shell) of rapidly expanding plasma moving away with a speed close to c. (Usually this is a remnant of explosion when star went supernova in the past). What happens if this fast-moving gas hit a cloud of cold matter. It heats it up and we can see the glowing on the front of shock wave.

Now, imagine that more or less spherical shell hits more or less flat thin cloud which stands on its way as a wall, and you are behind this wall, observing the event from a distance. First you see is sudden glowing in the point of collision. For you it will be seen in the center of expanding shell, because you are perpendicular to the wall. So, you see it as a burst near BH or neutron star. What do you see next? As the shell is moving with close to c speed it reaches other neighboring points on the wall, and you see a circle of glowing expanding rapidly from the point of first contact. How rapidly? You can calculate it, drawing a geometry of the event and using Pithagor theorem. And you find it to be superluminal, especially in the very beginning.

Say, a sphere is 5 light years (l.y.) in radius and eaxpanding with close to c speed. It crosses a plane 5 l.y. away, and an INTERSECTION is a circle expanding with the speed which can be calculated by differentiating Pithagor equation: v=c x R/sqrt(R^2-L^2), where L is distnace to the wall and R-current shell radius (and dR/dt = c). You may see from this equation, that v is always more than c, especially when the circle is small (L=R).Say, when R=1.1L, v=2.4c

So what you see is very rapidly (faster than c) expanding ring of glowing plasma. And the center of this ring is seen (from your perpective) to coinside with the BH (or quazar, or neutron star, etc.), so you may get an impression that something was radiated by BH with superluminal speed.

If shell is not spherical, and a wall (or cloud of cold gas) is irregular, you may see not a circle, but oval or less regular structure(s) yet expanding with superluminal velocities. Ant that is exactly what radioscopes with high resolution saw.

So, non-materialistic object (intersection of materialistic objects) can move with any velocity. Take a flashlight and move your hand in front of it blocking and unblocking light - and a shadow edge crosses the Universe with superluminal velocity. But a shadow edge is not an object.