Would magn. pole reversal actually mess up electronic equipment?
in [Design]
|
Prev: Integrated AGC 100kHz-10MHz
Next: Piezo Amplifier
From: Martin Brown on 5 Jan 2010 04:52 John Fields wrote: > On Sun, 3 Jan 2010 07:31:18 -0800 (PST), MooseFET <kensmith(a)rahul.net> > wrote: > >> You are correct that the motions are relative to other bodies and not >> relative to some >> mythical fixed frame of reference in space. We are part of a group at >> appears to be >> gathering together amidst the greater collection that is flying apart. > > --- > Which leads to my favorite hypothesis; that there was no big bang, but > rather a big bubble which came about much like a bubble appears in a > cavitating medium. Big Bang was a derogatory term invented by the Steady State Cosmologist Fred Hoyle to disparage the new theory where the universe had a point in time where its entire radius was miniscule. Although it is possible that universes look big and long lived when you are inside them they could just be quantum fluctuations in some other larger object. It isn't a scientific theory unless you can test the hyposthesis. Some multiverse proposals do make testable predictions. > If that were the case, then the medium surrounding our bubble would be > the Universe, while what was bounded by the walls of our bubble would be > our universe. The distances are far greater than that. Exponential inflation has made a very large universe, we can only hope to see a fraction of it, and to a very good approximation it looks similar in all directions. And amazingly smooth at the furthest extremes in the CMB wavelengths. > > Looking at it from the point of view that matter is accelerating away > from us as its distance from us increases makes no sense in a big bang > universe since, after the initial acceleration, nothing would be driving > the mass and one would expect that matter would either recede at a > constant velocity if the universe was open, stop if the universe was > static, or accrete if the universe was closed. Not quite. Open universes expand forever and matter still has a finite velocity at infinity, and closed or bound ones it reaches zero and moves in again at some period - cyclic if you allow it to rebound. > > Such is not the case however, and for matter to accelerate as it gets > farther way from us requires that some force be attracting it. Or some force to be repelling it which is how the field equations represent dark energy (not a term I like). > > If that force is gravitational and our universe is bubble-like, then the > tug must be exerted by something external to our universe: the mass > peculiar to that part of the Universe which is attracting it, causing > matter on this side of the wall to hurtle toward it. If the universe outside our visible horizon is as uniform and smooth as it looks from the microwave background then it is difficult to see how this would work. It might explain our peculiar velocity relative to the CMB if there was something massive accelerating us in the very early universe but is presently beyond beyond our observable horizon. NB Cosmological expansion of space itself at large distances is not limited by the SR restriction of being less than c. This means there are or could be parts of our universe moving away so fast that they can never be reached even at the speed of light. You cannot have uniform shells of external matter accelerating things towards them Gauss's Theorem prohibits that entirely. > > As you say, there are, interestingly, blue shifts in our local group > which indicate that some of our members are being attracted to each > other. It is called gravity. Our local cluster is gravitationally bound. It is no more surprising than finding the solar system with the odd comet hitting Jupiter. The heavyweights mop up the smaller stragglers and if you wait long enough either settle into a nice mutual orbit or collide. Galaxy collisions are fairly rare but very pretty. http://antwrp.gsfc.nasa.gov/apod/ap001113.html Like atoms galaxies are mostly open space so they pass through each other but drag stars and gas into complex patterns. > > Even as that happens, though, we're _all_ accelerating toward the wall, > sort of like people walking toward each other on a train accelerating > toward a mountain. You seem to be using the word "wall" in a non-standard way. Observations of galaxy distributions have put some pretty tight constraints on what is possible. http://en.wikipedia.org/wiki/Galaxy_filament The string theorists might just be right - the distribution is suggestive - although it can also be simulated with conventional theory - Durham University have a super computer doing exactly this. Some of the more interesting simulations are online at: http://www.dur.ac.uk/n.s.holliman/CosmicOrigins.html Regards, Martin Brown
From: Archimedes' Lever on 5 Jan 2010 05:40 On Tue, 05 Jan 2010 15:30:07 +1100, Sylvia Else <sylvia(a)not.at.this.address> wrote: >>> No - they still have differing orbital periods, even though they move at >>> about the same velocity, because those further out have further to >>> travel to make one orbit. >>> >>> Sylvia. >> They travel a LOT faster. D'oh. Jeez, any 13 year old watching natgeo can remember that episode.
From: GregS on 5 Jan 2010 09:42 In article <00a0d326$0$16928$c3e8da3(a)news.astraweb.com>, Sylvia Else <sylvia(a)not.at.this.address> wrote: >John Fields wrote: >> On Fri, 01 Jan 2010 21:36:18 +1100, Sylvia Else >> <sylvia(a)not.at.this.address> wrote: >> >> >>> Objects at different distances from the centre of the galaxy will have >>> different orbital periods. The time the Earth takes to go around the >>> galaxy will be different the time other objects take. There is no reason >>> to deem that the Earth's orbital period is the period of rotation of the >>> galaxy, and since different objects have different periods, the galaxy >>> does not have a rotational speed. >> >> --- >> Surprise!!! :-) >> >> http://en.wikipedia.org/wiki/Galaxy_rotation_curve >> >> JF > >No - they still have differing orbital periods, even though they move at >about the same velocity, because those further out have further to >travel to make one orbit. > I was wondering why most things rotate inline bunched up, around the axis in the same direction. What starts this process ? greg
From: Tim Williams on 5 Jan 2010 11:43 "GregS" <zekfrivo(a)zekfrivolous.com> wrote in message news:hhvivs$ebi$2(a)usenet01.srv.cis.pitt.edu... > I was wondering why most things rotate inline bunched up, around the axis > in the same direction. What? > What starts this process ? If you mean the rotation of galaxies, it's the compression of a ball of gas with a small amount of initial angular momentum. Size goes down, speed goes up, L stays constant. The extreme case is a black hole, which can rotate very fast indeed (think inertial frame dragging). Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: John Fields on 5 Jan 2010 13:21
On Mon, 04 Jan 2010 16:58:14 -0800, The Great Attractor <SuperM(a)ssiveBlackHoleAtTheCenterOfTheMilkyWayGalaxy.org> wrote: >On Mon, 04 Jan 2010 13:22:32 -0600, John Fields ><jfields(a)austininstruments.com> wrote: > >>Which leads to my favorite hypothesis; that there was no big bang, but >>rather a big bubble which came about much like a bubble appears in a >>cavitating medium. > > > I think of it as a big cheese ball, and a black hole places matter >"outside" the bubble. --- I like to think of the Universe as a more or less infinitely large and massive Swiss cheese with lots of bubbles in it, one of which is our local universe. --- > After all, where does all that matter go that they swallow up? --- It returns to the Universe. Since we observe galaxies with larger and larger red shifts as they hurtle toward whatever is accelerating them toward the "wall" until eventually they hit it, leave our universe, and become part of the Universe. Another possibility (among any number of others) is that they could accelerate without bound until they go transluminal and then wink out of existence when their mass turns into energy. --- > Once enough of it ends up outside the bubble, it will collapse the >bubble, in a time frame quick enough that we may not see it coming. --- True. Since what we see when we look as far as we can out into space is what was happening billions of years ago, what happened more recently, at the cosmological horizon, will tag along behind that early light. Then, if our bubble is collapsing at less than the speed of light we'll never be able to detect it except, perhaps, for galactic and stellar extinction events which occur closer and closer to us in time as the horizon (wall) approaches us. Just as an aside, if the bubble was collapsing and the infinitely massive Universe was on the other side of the wall, we would expect to see objects accelerate toward the wall as it approached them. Maybe the collapse will engulf us in 2012? JF |