Some questions for better understanding of Main Stream Cosmology

Discussion in 'Astronomy, Exobiology, & Cosmology' started by RajeshTrivedi, Aug 28, 2014.

  1. RajeshTrivedi Valued Senior Member

    Hubble's law and postulates of Big Bang says that all the Galaxies are moving away from us. The general mapping of universe around us (barring the Milky Way Obstruction area) also confirms that our universe is Isotropic and Homogeneous, it is also well settled that we occupy no special place in the Universe.

    Our Galaxy is moving with reference to some Extra Galactic Reference at a speed of around 600 Km / Sec, based on Hubble Law and Red shift observed we have concluded that a few distant Galaxies are moving away from us at a speed of around 30000 Km/Sec.

    Since our Universe is Isotropic and Homogeneous, so it does not matter if we are observing from Earth or from any point on any other Galaxy which is moving away at a speed of 30000 Km/Sec from us. Since we are moving at a speed of 600 Km/ sec, the least speed of this Galaxy would be around 29400 Km/Sec. Now if we put an observer somewhere on this Galaxy, then also we will see the same kind of isotropic and Homo map of galaxies and stars around it. So…

    a. Applicability of Hubble's law will soon make a Galaxy run away at a speed of light. That’s some speed for such a huge mass. Here comes Gravity Red Shift?

    b. We would be a very remote Galaxy for this shifted observer, so how come we are travelling at a very low speed (leave aside the relative aspect). This observation indicates that there got be some special place.

    c. There are few blue shifted Galaxies also, including our Andromeda, wherein we expect to collide in next 4 b years? Why ? The explanation is that they are all in local groups and have some peculiar velocity. Universe is Homogeneous and Isotropic, so why this peculiar velocities for our Local Group. Even some of very far Galaxy or cloud systems are giving blue shift that directly violates Hubble law.

    d. The balloon analogy of space expansion does not explain this vast difference in the speed of Galaxies, moreover if the space itself is expanding, then how can we collide with Andromeda in 4b years, fine there must be some Gravitational pull between the two, but was it present from the day these Galaxies were born, because new pull can only become effective if the rate of amassing the peripheral mass is much faster then the rate of space expansion.

    e. Why there is a total absence of expansion of inside of Galaxy or Solar System. A dot on the baloon surface expands with its skin. An expansion which can cause huge speeds for Galaxies, cannot per say disturb the internal arrangement ? It is also not the case that Gravitational pull of constituents is a very strong force?

    f. Why is that our Solar System which has passed many a times (around 20?) through the Density Wave Arms region of our Galaxy, and still surviving with its planets? Density wave region is supposed to be great breeding place for new stars, obviously its not a smooth high speed expressway for our solar system? Or we can say that it ducks or jumps this region and gets out of the plane and moves either up or down?

    g. How can a Galaxy maintain its basic structure with an observation that the orbital speeds of all the stars is almost same (leave aside near to center stars)? The closer stars will move faster angular-ly leaving behind the distant stars, thus changing the basic structure of the Galaxy. So the shape we see today of our galaxy (in photo of course), is it the same when our Sun was born (around 4b years ago)? The point is what are we seeing in the photo (the present or may be few billion years ago shape?)

    h. Gravitational lensing is a great observation, great analysis. My only question is if you bend the light angular-ly, that means some deceleration has taken place. How does it justify the constancy of light? I can tell you fall below c and Energy is no longer Energy, it becomes Mass+Energy, and then the poor combo cannot make it to Earth.

    i. Inflation is supposed to be microscopic expansion from a singular particle of infinite density with a faster than light speed. Relativity is violated even after t = 0?

    j. And by the way if it was faster than light, why no traces of anything moving at faster than light (even if we take relative speeds can we get more than 2c?)
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  3. origin In a democracy you deserve the leaders you elect. Valued Senior Member

    I don't have much time but I will comment on a few of your statements.
    Galaxies that are beyond a certain distance will have a recession velocity exceeding c. You are making the mistake of equating recession velocity with velocity through space. The galaxies are not moving at these great speeds, the universe is expanding. Using the old analogy of the raisin cake, as the cake expands the raisins get farther apart but they are not moving THROUGH the cake.

    No that is not true. A far distant galaxy that we observe with a recession velocity of almost c could in fact be not moving at all relative to to it's local region of space.

    The rate of expansion is about 74 kilometers per second per megaparsec, which is not much unless we are talking about huge distances. In our local area gravity overcomes the expansion. That is important, strong gravity overcomes the expansion of space. This is true in every area of the universe. As far as very distant galaxies having a blue shift I do not think this is correct please site a source for this claim.

    The balloon anology is 2d but it does explain the differences in the speed of the galaxies. If the expansion is uniform and doubles then 2 dots .5 inches apart intially will now be 1 inch appart and 2 dots intially 2 inches apart will now be 4 inches apart.

    As I said local gravity will overcome the expansion.


    It is because the distances between the star is so great. The movement through the arms is responsible for the dispersion of the open star cluster that the sun probably formed in. The chance of the solar system being disrupted by coming too close to another star is extremely remote. The gravity from other stars we pass will cause changes in the orbits of comets though.

    Not sure what your point is here. Since the rotation is relatively constant for the stars why would it change significantly over time?

    The light is not bent, space is bent the light is moving in a straight line through the bent space.

    Relativity says nothing can move THROUGH space faster than light, the expansion of space faster than c is not a violation.

    Again nothing in the universe was moving faster than light just the expansion of the universe was faster than light. There is no limit on the recession velocity of distant galaxies AFAIK. Of course once they exceed c we won't ever see them again.
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  5. paddoboy Valued Senior Member

    Hard to go past origin's full reply....
    A few summation points may help though.
    Relativity tells us that nothing can travel at or faster then the speed of light......referring of course to anything with mass. Spacetime has no mass so in effect is not hobbled by this law.
    That also explains the Inflationary epoch, when spacetime underwent an incredible expansion rate.

    Very distant galaxies are observed to have all three redshifts....Doppler, a relatively small amount due to local galactic movements governed by gravity, in association with its own local group.........Gravitational redshift, again a small amount caused by light from a distant galaxy, climbing out of its local gravity well.......and thirdly, the vast majority caused by cosmological redshift due to the expansion of spacetime between them and us.

    I'm totally sure no distant galaxy over large universal scales has been ever observed to have any cosmological blueshift.

    Local groups, of which there are millions just like our own local group, see their own spacetime expansion nullified by the force of gravity.
    It is only over large scales that the accelerated expansion is observed.

    As local groups merge over billions of years, and distant expansion rates approach "c" over large scales, in eons to come, there will in effect be very few distant galaxies visible from Earth, as they move beyond the observable universe.

    In effect it is logical to assume, that in many hundreds of billions of years hence, as distant galaxies move beyond our observable horizon, the evidence we have now for the expansion of the Universe, will not be evident in those distant times.

    Light also travels in geodesics, and follows the topology of spacetime it is passing through

    Finally, when M31 [Andromeda] and the other galaxies within our local group merge in a few billion years, any stellar collisions will really be quite rare, due to the vast astronomical distances between stars.
    Galaxy shape will change over many eons as gravity works its magic, but stellar collisions will not be any where near as frequent as a merger might suggest at first glance.
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  7. LaurieAG Registered Senior Member

    What about clouds of hydrogen?

  8. RajeshTrivedi Valued Senior Member

    For better clarity lets start with the simplest of all::

    You mean to say that the spatial arrangement of stars (thus shape of Galaxy) would not change due to this constancy in orbital speed? For example if we are at x distance from our GC, and there is another star system at 2x from GC [in the same radial line], then by the time we complete one revolution around GC, the other star has completed only the half. Won't that change the shape of Galaxy?
  9. RajeshTrivedi Valued Senior Member


    Thats copy book answer. The point is under which category of physics you would put this motion of -no particle no energy-. It is also stated (copy book) that it was an accelerated expansion of spacetime in a span of 10^-35 to 10^-32 seconds at some phenomenal speed. Acceleration and speed deserves the attention of Physics, which Physics?? Do we understand this Physics or as you may say that this was also a fudge factor but now well established and well accepted.

    And Incidentally, some of the radiations are considered to be massless, why they do not accelerate to this kind of speed ??
  10. paddoboy Valued Senior Member


    Yes, certainly is "copy book"mainstream accepted answer, simply because that's what relativity says...another "copy book" mainstream answer.....The reason why nothing with mass can obtain "c" is because the closer to "c" it gets, the more massive it becomes, and the more energy is required to push it speeds approach "c'mass approaches infinity, so requiring infinite energy.
    spacetime has no mass and as I said is not curtailed by the speed limit.
    It's called SR.
    BTW, theories and models obtain mainstream acceptance, because they align with observational and experimental evidence better and are more logical.
    Woo science and pseudoquackery are easily revealed when put to the tests of scientific methodology and peer review.

  11. RajeshTrivedi Valued Senior Member

    Where is the mass ??? Still they are curtailed by SR ??

    If the spacetime can travel beyond c, why not these radiations ?? You did not answer which physics is applicable to spacetime expansion beyond c.
  12. origin In a democracy you deserve the leaders you elect. Valued Senior Member

    The question was why is the solar system intact after it passes through a spiral arm, hydrogen and dust in the arms will in general have not effect on the solar systems survival.
  13. origin In a democracy you deserve the leaders you elect. Valued Senior Member

    Huh? You had a whole thread addressing the fact that this doesn't happen; the stars at x and the stars at 2x complete an orbit in about the same amount of time..:shrug:
  14. Janus58 Valued Senior Member

    No, because the density waves don't move. It works like this video, the inner stars do take less time to orbit, but the regions in which the stars are closer together don't.
  15. paddoboy Valued Senior Member

    Are you familiar with the Einstein mass energy equation?
    The speed of the Inflationary epoch of spacetime, and the accelerated expansion we observe at this time is achieved because it is space that is expanding. It has no mass, only an unknown component we dub DE.
    This DE seems to act as opposite to gravity.

    FTL travel also appears to exist at the quantum level in a process we call quantum entanglement, which shows that quantum particles react to changes in one another instantly, even when separated by the size of the Universe itself.
    Why? We don't really know.
    But herein is where science trumps all other mythical assumptions, in that it always strives to find these answers, via our scientific method and peer review system.

    When you ask why cannot other forms of energy travel FTL, you are asking why is the Universal speed limit what it is. We don't know, other than "c" is a universal constant.
    Otherwise your questions now seem to be questioning accepted mainstream cosmology.....nothing wrong with that in itself, but certainly then questions need to be asked as to why you are questioning such scenarios that are near factual as one could get, with the data generally commonly known, such as E=Mc2.
  16. RajeshTrivedi Valued Senior Member

    So as per mainstream cosmology, the answer to the question is (Please correct me if I am wrong):

    1. There was no physics before t<0, and even singularity was beyond Physics.
    2. There was Physics from t = 0 to t= 10^-35 sec (Start of Inflation).
    3. Suddenly Physics vanished and there was no Physics between 10^-35 sec to 10^- 32 sec (The Inflation).
    4. Now also there is no Physics (for) as Spacetime can expand at a speed > c.

    Or should we say:

    1. There is Physics (except t<0) but Spacetime is not well understood and It is beyond the scope of SR/GR/Newtonian as Spacetime is massless concept. For distant Galaxies Spacetime can decide to move faster than c.
  17. RajeshTrivedi Valued Senior Member

    Thats great

    So we can say as per Mainstream Cosmology

    Stars change their Spatial Position but Density Waves (Arms) do not. Again some kind of convenient hypothesis, for the simple reason that the GC is too strong, we are agreeing that there is some kind of mega Black Hole there, and this Black Hole cannot make Hydrogen Gas Clouds in the Density Waves to move.

    Fair enough, the another part of the question is how do we survive our travel through this Density wave Region? It is mega production factory for stars, it certainly can be thought as Pit Shop for our Sun to refuel itself, but what about us. Can we survive such hostility? I do not know when we are going to enter into this segment (or if we are already there?) but that would be sure shot complete extinction.
  18. RajeshTrivedi Valued Senior Member

    Quantum Entanglement: Calls for a big discussion, let us flag it for sometime.
  19. paddoboy Valued Senior Member

    There was no time nor space [as we know them] before t=0

    The period between t=0 and t+10-43 seconds is not covered by present standard cosmology or GR.
    A future QGT may shed light on that epoch one day.

    Refer to 1 and 2/
    NB: Our certainties on what occurred diminish the closer we get to t+10-43 seconds. We still have a good handle on what is covered by those theories, and plenty of research in particle accelerators like the LHC, are revealing more data.

    'That's a weird convoluted way of putting it.
    Again, spacetime being massless, is not inhibited by any speed limit.
    The reason why nothing with mass can obtain "c" is because the closer to "c" it gets, the more massive it becomes, and the more energy is required to push it speeds approach "c'mass approaches infinity, so requiring infinite energy.
    spacetime has no mass and as I said is not curtailed by the speed limit.
    It's called SR.

    SR has stood the tests of time, experiments and observations for more than 100years.
    It is a scientific theory that is near certain in its applicability.
  20. origin In a democracy you deserve the leaders you elect. Valued Senior Member

    RajeshTrivedi, you are arguing against mainstream theories that you clearly do not understand. I find it strange that you are so dead set agains ideas of which you are largely ignorant. Why wouldn't you learn a little bit of the actual physics and then see if you disagree?
  21. wellwisher Banned Banned

    Einstein via relativity, discusses how mass; GR, and motion;SR, impact space-time. He never defined space-time as something that can expand or contract all by itself without mass or velocity playing the lead role. Space-time leading is an extrapolation that Einstein never made.

    One can prove motion can cause time to slow and one can prove that mass can contract space-time, but how do you prove space-time can lead both mass and velocity? Why did Einstein ignore this since it was a simple perturbation?

    The theory of space-time leading uses dark energy, which has also never been seen on the lab. This appears to be trick science where math can be used to model game engines.
  22. origin In a democracy you deserve the leaders you elect. Valued Senior Member

    Another example of your lack of knowledge and confusion on relativity and science in general.
  23. Janus58 Valued Senior Member

    Who said anything about the hydrogen gas in the spiral arms not moving. Everything moves in and out of the spiral arms. It's just that as matter passes through the spiral arms it is more densely packed together than it is outside the spiral arms. It is something like a slowdown on the highway, when cars reach it the traffic becomes denser and as it leaves its it thins out again. The point of the slow down doesn't move even though the cars in it are constantly entering and leaving.

    As far as this increase in density goes, the average density of the galaxy is so low to begin with, any slight increase when in the spiral arms would have no real effect on the solar system. Here's what I mean by how low the density is even in the spiral arms. If you take the average density of the matter contained within the spherical volume enclosed by Pluto's orbit, and compare it to the average density of a 100 light year radius volume of a spiral arm, the average density of the Solar system is much much greater.

    Now while the increased density on the Spiral arms does increase star formation, this only happens in those regions where the density was already greater than average before entering the spiral arm. The solar system is not in or near any of these stellar nurseries, so is unaffected by the increase in star formation.

    Another thing to consider is that the reason that spiral arms look so bright compared to the gaps between is not entirely due to stars being packed tighter. As mentioned above, these regions also have greater rates of star births, which includes massive stars. Massive star are very bright. they also have short lifespans. These massive stars tend to burn out before they leave the spiral arms. It is only the smaller dimmer stars that live long enough to reach the "gaps". So the spiral arms tend to have more young bright stars and thus look brighter. If you were to just the relative densities of the spiral arms vs, the gaps, it would not look as distinct as it does by visible light.

    Our Solar system is in the midst of a spiral arm right now. The only real difference between being in one versus not being in one would be the number of stars visible to the unaided eye.

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