Lazarus

Now I understand. We modified gravity to match our assumptions. An equation can be constructed to match almost any assumption. That seems reminiscent of the equation called the Roulette. It quite accurately predicted the motion of the sun and planets about the earth. Probably doesn't prove the sun rotates around the earth. It seems more logical that the source of the Red Shift was moving at a high velocity many years ago when the light started its journey. The Red Shift itself could be caused by the difference in energy that it takes to change an electron's energy level in the direction of motion of the atom than in the opposite direction. That might even mean the Red Shift is not completely linear. It's a good thing that you can't through things through the internet or I would have to wear my hard hat.

Then where does the gravity that keeps the Milky Way and Andromeda from moving away from each other due to the space expansion come from?

Since gravity exactly matches space expansion up to 200 million light years, that seems to imply that either galaxies further away are not fleeing or space is not homogenious.

Iggy, That is a beautiful explanation gravitational binding of galaxies. I see where the force of gravity can match the expansion of space within a sphere. The force of gravity in a sphere is proportional to the reciprocal of the distance from the center of the sphere. (1/r*r) The effective mass and hence the magnitude of the force of gravity increases by the cube of the distance. (r*r*r) Combining the two, the net gravitational force is proportional to the distance from the center. ® The effect of expanding space is also proportional to the distance to the center. That shows that there can be a balance between them. However, galaxies are more disc shaped than spherical which seems to imply that gravity would be weaker than space expansion at the outskirts of the galaxy. Thank you very much for simplifying the concept for me.

Sorry ACG52, I was going to shut up but I couldn't resist commenting on your post. One tenth of the diameter if a proton is about 10 to the minus 16.meters. The number of seconds in 13 billion years is 60*60*24*365*13000000000 or about 4*10 to the17th power. Which amounts to a few meters in 13 billion years. However, space is supposed to have expanded a few hundred times in 13 billion years. Warm reguards, Me

I will try one more time to get someone to take an objective look at why galaxies don't expand with the expansion of space. It is only logical that if space is expanding the distance between objects should increase. The reasons that I received are: 1. Gravity "overwhelms the expansion of space". "Overwhelms is hardly a measure of anything" 2. At a distance of 199 million light years expansion has no effect. At 201 million light year it has the effect of driving galaxies apart. Weird! 3. Referred to Wikipedia's "ants on arubber band" analogy. As useless as the pennies on a balloon analogy. I didn't think analogies proved much. 4. The distance between objects doesn't change the effect of space expansion. Doesn't set well with the contention effects only occur when objects are 200 million light years apart. 5. You are a dummy, go away. May be so. Can you really accept any of these responses as answering the question?

Dear ACG52, There is no way we are going to agree on this but I thank you and appreciate what you are doing.

There is nothing in Wikpedia article that gives any logical answer to why galaxies are exempt from the expansion of space. The ants on a rubber analogy is as worthless as the pennies on a balloon excuse. I originally asked for a logical explaination of why galaxies don't expand like everything else. No answer was forthcomming. The debating ploy of asking for proof of the question was used. I responded with a straighforward example. The response did not point out an error in my example but used the Athority says so technique. I realize that you all would like to put me in the crackpot column but I am just asking for a believable reason. All of the respondents must know that is not intuitive or kind to common sense that space is expanding along with everything in it except galaxies. My question has not been answered. Thanks to everyone that has posted or read this thread. If you wish to yell at me privately email

I prefer the Day and Night of Brahm where the universe expands and contracts continuously. There is no reason that our universe is the only one. Like we are no longer the center of the universe with the sun and stars rotating around us. The equation called Roulette did a good job of predicting how the sun and planets rotated around us. I don't think that proved the sun rotates around the earth. I also don't thing the good and valid equations of Relativity prove the universe is screwy and incomprehensible.

Even an infintesimal force will change an orbit. The same rules should apply across the universe so the expansion would be there whether one mile or 250 million light years. The effect should be the similar with stars 150 or 250 million light years apart. If this examplle doesn't work for you, please post a link or something that gives a logical explanation of the reason that galaxies do not expand while the space in which they reside is expanding. I have not been able to find anythig but generalizations of the problem. Thanks again for taking the time to reply.

It is very nice to have some feedback from knowledgeable individuals. I appreciate it immensely. Let me try to explain what I meant by the effect of space expansion increases with distance. I would like to push Mars to 186 million miles from the Sun and fatten it to match the mass of earth to make the arithmetic simpler for me. Then use the Sun, Earth and Mars for examples. Even though I majored in mathematics a million years ago, now I have to use a calculator to add two and two so anything that helps is good. The picture: ! ! ! ! S 1 E 1 M 2 Time 1 ! x.................................y..............................z Space ! ! ! ! ! S 1 E 1 M Time 0 ! x...............y................z Space ------------!------------------------------------------------------------------ ! Distance ! At time zero the earth is orbiting with gravity and space expansion in balance. The time scale is such that from T0 to T1 space has doubled. In Newtonian space the gravitational force is proportional to g divided by r squared. In the expanding space model gravity is Newtonian gravity plus the additional amount needed to compensate for the expansion. Say g' = g + a. a is the acceleration needed to move Earth enough to match the expansion. So the force g' on Earth is proportional to (g +a) / r*r. However, the force required to hold Mars in place is (g + 2a) / r*r. Which implies that g' is insufficient to hold Mars in place. Is this wrong?

AG52 & ZAPATOS Of course "failing to orbit" doesn't match observations. That is why there is a question. Do you agree that although the force of gravity decreases with distance, the effect of space expansion increases with distance?

ACG52, If the force of gravity is equal to the space expansion at about 200 million light years and stars orbit the center of the galaxy then anything closer will fail to orbit and be sucked into tthe center. The contention that space is expanding but galaxies are exempt is an extraordinary claim and needs a least ordinary proof. The ball is still in your court.

Zapatos, Thank you for the reply. If gravity is holding the stars to the center of the galaxy at the present distance from the star to the center of the galaxy the increase in the distance weakens the force of the gravity. I don't feel that made a strong case for the galaxy taking exception to the expansion of space. Photons seem to 'hold together" pretty well but still are stretched by the expansion of space.

I have seen comments that galaxies should not exist with the expansion of space. I cornered some Cosmology instructors at Arizona State University and asked the this question: "Since photons expand because of the expansion of space, galaxies separate because of it, two stars in different galaxies separate BUT two stars in the same galaxies do NOT separate. How can that be?" The only answer I could get was that galaxies just hang together. I even mentioned the analogy of pennies on a balloon that is very weak logic. I said if the pennies were painted on the balloon the result would be very different. After a few iterations of the discussion I just said thank you and left disappointed. I would like to hear a believable explanation.