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What keeps the stars apart?

  1. Oct 12, 2003 #1
    [SOLVED] What keeps the stars apart?

    I have often looked to the night sky and wondered what keeps all these zillions of stars apart. Centrifuge I feel is not adequate alone. Expansion of the universe doesn't work either

    All the stars are attractive with their inherant gravities and yet there seem to be very rare collisions given the vast number of stars involved.

    I once thought that maybe it was the light they emit that acts as some sort of repulsion and as theorised if a star stops shining it collapses and generates a huge amount of attraction.

    Could it be that the light is in some way an inverse gravity that acts as a repeller on other astral bodies.

    I have always held to the premise that what happens only happens because it HAS to happen. So, what has to be happening to keep the stars apart I wonder?

    Any ideas?
  2. jcsd
  3. Oct 12, 2003 #2
    Well, did you ever see the movie Swordfish, with John Travolta and Hugh Jackman and Halle Berry? You should...for insight into the universe no less :)

    Well, in case you didn't, at the beginning they had what John called the world's largest walking Claymore mines. Claymores have shrapnel you see and John's "mines" were people with explosives and ball bearings strapped to them, little spheres about an inch in diameter. Now the scale isn't going to be nearly right, neither time-wise nor space-wise, but the scene showed a matrix-style panorama of the explosion of one of these things and the ball bearings go everywhere...Now imagine that the explosion was the big bang, and that the ball bearings are like stars (stars formed after the big bang but no movie is perfect eh? :) ) Now, the ball bearings have an attractive force, but they don't clump together because the explosion sent them flying apart so fast.

    Well, the stars are the same, the big bang threw all this stuff out so fast that it is still slowing down. One of the big questions in physics today is what will happen to the universe...is there enough mass to the universe that gravity will be able to slow everything to a stop and then pull everything back into a big crunch...or will the universe keep expanding forever?
  4. Oct 12, 2003 #3
    Well said Zimm.

    scott_sieger, light does not act as a repeller on other astral bodies as far as I understand. Although there was a theory conjured up (I believe it was around 1920) that accounted for the need of a gravity repeller by Einstein called the Cosmological Constant. This was said to be wrong and Einstein claimed it to be the biggest blunder of his life. Although about 70 years later a similar cosmological constant was being entertained. And I understand it is still being studied today. Although I do not know if the reasons for studying the edited version of the cosmological constant are to help understand why bodies dont fall into to each other.

    There are three models that describe how much of a Bang the Big Bang would have to of had to keep the galaxies from falling into one and other: 1) Just enough of a bang that would allow the universe to expand for a limited amount of time until it began to collapse. 2) A bang big enough to cause the universe to expand forever and never collapse, and 3) The precise amount of a bang to allow it to expand but always be on the verge of crossing the limit and begin to contract.

    It is my understanding that the 3rd one is what a good majority of physicist believe (I could be way off, my studies have been on books written in the 80's and 90's, I could be way off)

  5. Oct 12, 2003 #4


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    Its pretty simple really - all the stars we see are in their own orbits around the galactic center. They aren't moving randomly nor are they stationary. Its the same reason why the planets in the solar system don't all crash into each other.

    This also has nothing to do with the expansion of the universe or consmological constant, etc. Those concepts do not apply to something as small as a galaxy.
  6. Oct 13, 2003 #5
    From what I have read, earth and the other plants certainly will crash into our sun, although it will be billions of years from now and our Sun will have burnt out by then and swallowed the earth in its explosion. It is also my understanding that each orbit our earth takes around the sun the closer to the sun the earth gets; the difference is subtle and almost not measurable but indeed happens and is measurable.

    I took scott_sieger's question as having a lot to do with the expansion of the universe and the cosmological constant.

    He asked "what keeps all these zillions of stars apart" I didnt answer this question based on my own thoughts. I answered it based on other peoples' thoughts I have read. This is not the first time the question scott_sienger asked was asked.

  7. Oct 13, 2003 #6
    well.. since everything is soooooo far apart, they dont do much to eachother.. i think? dont mind me, im a newbie at physics.
  8. Oct 13, 2003 #7
    i think my problem is I keep thinking of how a duality can exist in an infinite singularity
  9. Oct 13, 2003 #8


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    That is true, but for different reasons than what is happening with the stars - and it will take so long that it doesn't change my point. Its not relevant to the question asked.
    Yes, I think he was asking that, but the cosmological constant and expansion of the universe aren't relevant to the mechanics of stars orbiting in a galaxy.

    To put it another way, he was asking:
    'How does 'A' affect 'B'.
    And the answer is:
    'It doesn't.'
    Uh huh.... why exactly are you here, Scott?
  10. Oct 13, 2003 #9
    Roger that Russ. I am in agreement with you.

    I first thought Scott was asking why galaxies hadn’t already gathered together. I believe it was the word “zillion” that through me off. I thought of that as being at least more than one galaxy. After rereading his post I see how you took it, and don’t disagree with anything you said.

    And after all the real problem ended up being “how a duality can exist in an infinite singularity?” Lol, is that hogwash? I am an amateur I admit but the original question leading to the answer of “duality in an infinite singularity” is not making sense.
  11. Oct 14, 2003 #10
    Hey guys, thanks for the reponses but not one of you have answered the question.....obviously I have failed in communicating it at the level of the audience...learning, learning all the time ...accept my apologies please.

    The question put in another way is : We know that everything is in a state of some sort of attraction and what I am asking is simply that if this is the case then why doesn't it all fold in on itself and go home.

    If only attraction exists then this is a state of singularity and makes no sense at all. Because it would all just fold in on itself or stars will come together regardless of the "Theoretical" and I repeat "theoretical" Big bang.

    So what keeps it all apart?... " a duality" ....I am not looking for a universal constant. What I am looking for is intelligent discussion hopefully leading to an understanding of a universal constant. I made the mistake of assuming that the audience knew this... sorry I wont make
    that mistake again.

    I am not here to sparr using someone else theories, I am here to increase my understanding and hopefully we can all share in doing so.
  12. Oct 15, 2003 #11
    I would agree with this if you narrowed it down a bit and said “we know that everything is in a state of attraction with gravity”

    Gravity does always act attractive but there are other forces at play. 4 in total: the strong force, weak force, electromagnetic force, and gravity. Gravity is the only of the 4 that always acts “attractive.” It is the weakest of the 4 forces but has the longest range; it is also the least understood.

    Much work has been done to try to unify all four forces. They came close with the “GUT Theory” but that only unified 3 of the 4 forces. The one left out of the GUT Theory was gravity.

    *back track a few years* Interestingly Einstein struggled with gravity as well. He published Special Relativity in 1905 but took him and his buddies 9 more years to figure out how to incorporate gravity into the 1905 Special Relativity paper. They figured it out around 1915 and published the Theory of General Relativity.

    This is not the case unless you are only talking about the Gravity force only. However asking “why everything doesn’t all fold in on itself because of gravity” is a good question. There has been millions of man hours spent in thinking about that exact question.

    Please explain to me your understanding of the word “singularity” and how it applies to stars falling into one and other. I have a presumption that my understanding of the word singularity is different than yours. (If our understandings of the word singularity are completely off then no big deal; who’s to say who is right. For instance, you may think of an Apple to be a computer operating system that rivals Bill Gates’ products, and I may think of an Apple as being a fruit I eat.)

    Good chance this may happen, they have already coined the term “Big Crunch” for it.

    This is a big question and Russ and I tried to answer it in terms of “what keeps two or more orbiting bodies from crashing into each other” And “what keeps all the galaxies from crashing into each other”

    Please explain what a duality means in your terms? I understand it to be something like two ideas that lead to the same result, and have a vague memory of hearing how Plato talked about it in philosophy discussions.

    I apologize if I come across as “sparing” with you, I’m just trying to get on the same page with you. It’s hard to betray your emotions on the Internet ya know… all we have to go by is our typing. Again, …just trying to get on the same page here.

    Thanks for listening,

  13. Oct 15, 2003 #12
    Thank you for you well reasoned approach.

    True my conception of a singularity may be different as I also have a significant phyilisophical background. To me I use the word to suggest that the most overwhelming force is singular in this case gravity between two or more stars. The question of a duality is simply that if one only has an overwhelming attraction that defeats any oposing forces then one has ultimately a singularity fast or slow is not important to me. The ultimate outcome is an overwhelming of opposing forces.

    However the universe is not coming together as such and if anything is observed to be expanding. This suggests to me that there has to be a duality at work in the least. IN fact the opposing forces to gravity appear to be actually overwhelming the forces of attraction.

    Theoretically I use a simple model

    We have absolutely nothing.

    We put two objects in this nothingness that stand apart. Call these stars if you like.

    They are attracted to each other and maintain their distance.

    A state of equalibrium exists but only one force is known to be strong enough to be relevant and that appears to be gravity (the attraction)
    So I question this model.....how are they kept apart for in reality this certainly seems to be the case.

    Maybe the model is unrealistic but I have a real suspicion that at least in theory if we remove as many variables as possible and just look at a very simple state of duality we may find a simple solution.

    We can postulate over the centre of mass being a black hole. a centre of incredible attractive strength and somehow we have a plug around this hole called matter. this matter vibrates and I am trying to see why this vibration may in fact be the key to the question of a duality of interaction between our objects in a sea of nothingness.

    So we have emission and attraction. people have said that the emissions are not any where strong enough to act as a brake on attraction. I am exploring the concept of the emmissions some how gain useful strength at the reflector inverse to what we call gravity where the strength is greater at the source.

    This is conceptually very difficult to explain in words...drawings may help

    please tell me if i am starting to make sense as I am also learning as I go

    a second approach is:

    I have a feeling that the emmissions work with the gravity or space present and some how "hydraulic" the space thus maintaining an opposing force by using the gravity. The emmisions sort of get the space to humm in an alternating sense like a bell would if you hit it.

    Thus creating a strong block between the two theoretical stars. So in essence the emmissions may appear weak but are in fact may turn out to be very strong indeed. Some scientists are theorising about gravity waves and maybe this is relevant.

    any ideas?
  14. Oct 15, 2003 #13

    Your concept of space and matter may be entirely wrong. Perhaps the constituents that make up both are actually the same. What if the entire universe were a bowl of photons, and you stirred them up. I.E.The photons become localized with other photons. Essentially they orbit. Don't ask how. Lets call this the equivalent of matter, and it does the same as the photons (orbits other matter), and so on up to and past the point of galaxy level.

    Lets call these bound up photons christmas presents. They attract each other to the point where they get to close to each other, and to the point where the get opened up. This is what you see.
    They really never are apart. Space is teaming with free ranging photons. The entire universe is represented, and motion presently presents those chistmas presents in a grand presentation.

    To rehash - Gravitation is the photons wrapped up into little christmas presents - You don't get to see whats in them until they get ripped open for your pleasure.

    I hope this helps.
  15. Oct 15, 2003 #14
    I think you have a valid point. Maybe if i shift the terminaology a little and say

    Between the stars we have a photonic hydraulic lock effect therefore applying enough pressure outward to counter the attraction of gravity.

    Ha... a photonic hydraulic lock......sounds good ......ahhh beam me up scotty
    The idea i think may be serious but the words...the words
  16. Oct 15, 2003 #15


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    conservation of angular momentum; as Russ said:
  17. Oct 15, 2003 #16


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    Scott, you are asking what seem at first like complicated questions about concepts you first need a basic understanding of. You may want to pick up a book about basic Newtonian physics and relativity. Hawking's "Universe in a Nutshell" perhaps.

    There are two separate concepts at work here depending on scale: orbits (or conservation of angular momentum, which explains how the objects establih orbits) are what keep the galaxy and solar system stable, and the expansion of the universe (caused by the Big Bang or otherwise) keeps MOST galaxies flying apart.
  18. Oct 18, 2003 #17
    Russ, I am sorry...If I appear to be like a teenager in class throwing silly questions at a university professor. But I am working on a theory of Gravity and my questions are i feel teasing some imaginative responses. For instance Elsa was talking about absolute vacuum the other day when refering to negative mass..this has helped me enormously. Conservation of angular momentum i am finding hard to work with regards to spacial gravity in 3 dim. and even harder with gravitational harmonics, which is something I know in the end will have significance to the finished theory.

    So I suppose in a way I am fishing and I am sorry if this is annoying..I'll be better in the future I promise.

    For instance why do we not simply accept that stars are actually the same gravity pole and are in fact repelling each other?

    Sounds stupid doesn't it?

    Stupid it may be but the question is valid even for a university professor.

    Last edited by a moderator: Oct 18, 2003
  19. Oct 18, 2003 #18


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    The reason we don't assume they are repelling each other is because the motions would be different.

    Over 300 years ago, Newton and Kepler determined the paths that planets take (which is the same situation as stars). They determined that the motion can be accurately explained by a universal gravitational attraction. Every test of this theory has come to the same conclusion: they were right.

    If mass actually repelled itself, then instead of balls of gas and rock seperated by a vast empty space, we'd have a more-or-less uniform distribution of light elements in the universe (and we wouldn't be around to look at it, but that's another subject entirely...)
  20. Oct 18, 2003 #19
    please bear with me if you can

    I need to ask another some what innane question...that you may easily provide the answer to.

    What is the average distance between the stars say in a galaxy like the milky way. Is there a website that has statistical information that I could utilise?

    I really wanted to ask: Apart from minor exceptions what would be the minimum average distance between the stars?

    When i see a picture of a galaxy they do seem fairly even in their distribution say a variation of 10% max...just an observation.

    I'd love to see the figures like standard deviations, modality etc of the statistics. and what sort of distribution curve they would show.

    any web sites you know of?

    oh by the way,

    I would suggest that there is a huge difference between planets and stars not only in mass composition but also function. Maybe in gravity too......
    Last edited by a moderator: Oct 18, 2003
  21. Oct 19, 2003 #20


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    An average would be meaningless

    Scott, While it would be possible to work out such an average, it wouldn't mean much. Average distances between stars depend on their environments - those in the core of a globular cluster are packed many per cubic ly; in open clusters, they are also tightly packed, but not as much as in globulars. In our neighbourhood, stars are 1 to 10 ly apart; in the outer reaches of the Milky Way, they'd be less densely packed by a factor of 10 to 100. In LSB galaxies, the density would be lower still; in the IGM of clusters, maybe stars are, on average, >1,000 ly apart.

    As to a minimum distance, they are as close as is possible, given gravity and density - the 'contact binaries', where one star fills its Roche lobe. I'd have to look it up, but that distance would be <500,000 km
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