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Cindy
36 Posts |
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Larry Burford
USA
1355 Posts |
 Posted - 13 Sep 2005 : 13:24:54
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Cindy,
From the home page on this site go to the Cosmology tab. There is another cosmology tab when you get there (it is the default) and on that page there are several articles on the BB.
Most of us here do not think the BB is a viable theory.
Regards,
LB |
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Cindy
36 Posts |
Posted - 13 Sep 2005 : 16:49:28
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| Do they try to establish a relation between red shift and age or between red shift and mass of stars, don't they ? |
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PhilJ
USA
269 Posts |
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JMB
France
202 Posts |
Posted - 14 Sep 2005 : 02:24:57
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quote:
Originally posted by Larry Burford
Most of us here do not think the BB is a viable theory.
Unhappily the most renowned astrophysicists do not think so !
Every day , the users of optical fibres and other laser sets observe frequency shifts by light-matter interactions, without blur of the images and the spectra, but the use of their theories of light-matter interactions is forbidden because all people who describe strange, marvelous, mysterious effects in the Universe would lose their credibility.
The last "discovery" is the "anomalous acceleration" of the Pioneer probes beyond 5 UA.
No more evolution in biology, incoherent physics, ... Back to the middle ages ! |
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Cindy
36 Posts |
Posted - 16 Sep 2005 : 02:24:04
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quote:
Originally posted by Larry Burford
Cindy,
From the home page on this site go to the Cosmology tab. There is another cosmology tab when you get there (it is the default) and on that page there are several articles on the BB.
Most of us here do not think the BB is a viable theory.
Regards,
LB
If BB is not a right answer, then what is preventing galaxies from getting closer each other under effect of gavity ? |
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Larry Burford
USA
1355 Posts |
Posted - 17 Sep 2005 : 08:36:45
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[Cindy] " ... what is preventing galaxies from getting closer each other under effect of gavity ?"
Gravity, of course.
Suppose that Newton/Einstein are correct and gravity's range is infinite. In a universe of infinite extent (most of us here take this as a given) there will be equal amounts of mass in all directions so the net gravitational force on a particular galaxy is zero. Except for the occasional chance collision with another galaxy.
But most of us here lean toward Meta Model's concept of a limited range for the force of gravity. Once again net external force on a particular galaxy (absent collision) is zero.
LB |
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Cindy
36 Posts |
Posted - 17 Sep 2005 : 11:00:09
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quote:
In a universe of infinite extent (most of us here take this as a given) there will be equal amounts of mass in all directions so the net gravitational force on a particular galaxy is zero. Except for the occasional chance collision with another galaxy.
We know that in the univer, there are zones in which density of galaxies is very high. Now we consider galaxies in such a zone. Are these galaxies getting closer under the effect of gvavity ?
quote:
But most of us here lean toward Meta Model's concept of a limited range for the force of gravity.
Can you tell me where the concept comes from ? Other words, What makes you think the range for the force of gravity is limited ? And, within the concept, what is the fomula of the force of gravity ?
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Larry Burford
USA
1355 Posts |
Posted - 18 Sep 2005 : 08:42:12
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You will need to do some homework to come up to speed on the latest thinking about gravity. In addition to a dozen or so gravity related articles available via the page tabs mentioned before there are two books you need to read: Dark Matter, New Comets and Missing Planets by Tom Van Flandern and Pushing Gravity edited by Matthew Edwards (containing an article by TVF). Both are available via this Website's store or from places like Amazon.com. They are also available at many libraries.
But the really short version goes something like this:
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The universe is filled with a lot of very small particles flying around in all directions. The vast majority of these particles pass through normal matter w/o interaction, but a few will either bounce or stick. These interactions result in a slight attenuation of particles comming from the direction of any nearby mass and that attenuation creates a net force toward the nearby mass.
Also, these particles can travel about 5,000 lightyears on average before they hit another similar particle and scatter. This is the source of the range limit for gravitational force. Once you get more than about 5 to 10 thousand lightyears away from a mass the attenuation of particle flux from the direction of that mass is filled in by scattered background particles and the net force drops toward zero.
Galaxies would thus have to be very close to one another for them to feel each other's gravity.
At distances of less than a few thousand lightyears the formulas of Newton (or Einstein if you need to consider relativistic effects) are used for computing trajectories. As distance from a mass approaches the average scattering distance for the particles that cause gravitational force these equations would be modified by a distance-dependant-exponential-decay term.
Meta Model is not a new mathematical description of gravity. (The math we already have is more than adequate.) It is a new physical explanation of what gravity is and how it works.
Regards,
LB |
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Michiel
Netherlands
73 Posts |
Posted - 19 Sep 2005 : 16:29:48
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Assuming gravity has a finite propagation speed can have consequences. Here's an example.
When two equal masses are in circular orbit their orbital speed is given by:
vo = sqr( m * G / (2 * r) ) [m/s]
m is the mass of each body
G is the gravitational constant
r is the distance between the bodies
Let vg [m/s] be the speed of gravity then the time it takes for gravitation to travel from one body to the other is:
Tg = r / vg [s]
During that time each body will move a certain distance:
d = Tg * vo = r * vo / vg [m]
The force caused by gravity will now have a different direction as compared to gravity without propagation delay. The new force component is in the direction of vo, the orbital speed. The orbit will slowly get wider.
The ratio d / r is a measure for the 'error angle' but only if it's really small.
d / r = vo / vg = sqr( m * G / (2 * r) ) / vg [m/m]
We can see that the angle gets smaller with higher values of vg , no surprise there.
When r increases the angle gets smaller too. But higher m will give a bigger error angle.
Or you could say: all systems with a certain m / r will have the same error angle.
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What this means in practice depends on vg , I think. The effect may not be that big after all. |
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Larry Burford
USA
1355 Posts |
Posted - 20 Sep 2005 : 10:10:36
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If you set vg equal to c, the speed of light, and run your calculation you will find that all orbits controlled by gravity are unstable. In just few tens of thousands of years or so all of the planets in our solar system would be boosted to escape velocity.
If vg is set to several million times c, the time required for detectable orbital changes in our solar systm rises to several billion years. But there are some other objects we have observed that would still have unstable orbits unless vg is at least 20 billion c.
LB |
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Michiel
Netherlands
73 Posts |
Posted - 20 Sep 2005 : 16:23:55
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I agree that vg = c is right out of the question (although I don't think planets would reach escape velocity).
And even Isaac Newton couldn't accept gravity being an instantanious action at a distance - still we don't have an upper limit.
At least we do seem to have a lower limit.
Larry, do you know if this lower limit is low enough to have a significant effect on two orbiting galaxies? |
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Larry Burford
USA
1355 Posts |
Posted - 20 Sep 2005 : 16:34:30
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I'm not convinced that galaxies can orbit anything. The range of gravitational force is limited and that limit is small compared to the size of a galaxy. When two galaxies collide, however, or have a near miss, the parts of each one come close enough to the parts of the other for gravitational interactions to occur.
LB |
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Michiel
Netherlands
73 Posts |
Posted - 20 Sep 2005 : 16:50:44
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| Hmm yeah, but if the range of gravity wasn't limited, then could the low limit have a significant effect? |
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Larry Burford
USA
1355 Posts |
Posted - 20 Sep 2005 : 22:03:23
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Yes. For galaxies to be able to orbit each other the minimum speed for the propagation of gravitational force would have to be large enough for that force to travel between them in a time period that is very very short compared the orbital period.
20 trillion times c ?
LB |
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Michiel
Netherlands
73 Posts |
Posted - 21 Sep 2005 : 15:53:45
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Well, I picked some numbers, I hope they are realistic.
Assuming the range of gravity is unlimited:
Two galaxies with combined mass 2*10^40 kg
Distance 400,000 Ly (about 4*10^21 m)
Orbital speed is app. 10^4 m/s
Orbital period in the order of 10^18 s (that's ehrr 3*10^10 year, hehe)
For gravity to travel 400,000 Ly at 2*10^10 c takes 2*10^-5 year or 630 seconds.
My guess is you'ld need some patience if you want to watch these galaxies spiral away from each other. |
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Iaminexistance
USA
13 Posts |
Posted - 23 Sep 2005 : 15:17:58
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I don't know about you, but I don't think gravity is as far reaching as is said. Now, I may just be dumb here, so just bear with me. In my opinion(be it right or wrong) is that gravity is not the cause, but the effect. Due to mass bending space and time, gravity is created. If there is no mass in a general area, there is no gravity. This applies to several parts of the universe, so I would think, because if every part of space had mass, then it would be one huge heap of mass and the gravity would be so intense we would be crushed. I believe that electro-magnetism has a far greater say and command as to what is happening in the universe than gravity. In my opinion electro-magnetism is the cause of placement of everything, and gravity is merely an after-thought. Therefore if you were to look at the movement and positions of the galiaxies and how it is reacting with everything else, you would need to look at electromagnetism. They have been able to re-create in labratories "spiral galaxy-like" creations by shooting electromagnetism through plasma. It is very interesting indeed. These are just my thoughts... what do you think?
US AIR FORCE - Korean Linguist for life |
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Michiel
Netherlands
73 Posts |
Posted - 23 Sep 2005 : 20:53:58
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What do I think?
Cindy raised the question why galaxies don't just clot together. Larry pointed out that the range of gravity may be limited. Then I brought a possible finite propagation speed of gravity. Which doesn't seem to have a lot of impact unless m/r is very high, IOW if very heavy masses are in a very tight orbit.
Personally I like the idea of a limited gravity range and this is why: When we look out of our hubble window, we see galaxies,galaxies and more galaxies. On a rare occasion we see two galaxies collide (falling through eachother). We might as well build a model that allows for all those galaxies.
Dutch bum. |
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Larry Burford
USA
1355 Posts |
Posted - 24 Sep 2005 : 08:47:31
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[Michiel] "Well, I picked some numbers, I hope they are realistic."
400,000 LY is not much more than the diameter of an average galaxy. I would be inclined to characterize two galaxies with a center to center distance of 400,000 LY as being in collision, or perhaps a very near miss, rather than as orbiting. Some individual stars from each will be close enough for direct gravitational interaction.
Try 4 million LY. Or 40.
LB |
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Michiel
Netherlands
73 Posts |
Posted - 24 Sep 2005 : 12:15:26
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| Yes, 400,000 Ly is pretty close to touching. Of course when we enter a higher number, the orbital speed would be even less. The influance of the propagation speed of gravity on the orbit would be smaller too. |
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rush
74 Posts |
Posted - 29 Sep 2005 : 07:19:48
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A friend of mine told me the CMB is an absolute reference frame where galaxies it is clear that globular clusters and galaxies are at rest with respect to it. He says that this proves space is expanding but not matter.
What do you think? Any references where I could check if cosmologist really do this and how they verify that globular clusters and galaxies are at rest?
Thank you all. |
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Big Bang and Alternatives
