Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is Negative Mass

  1. Oct 9, 2003 #1

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper

    I remember one of the speculative ideas kicking around a while ago was the notion that mass, like charge, could be "positive" or "negative." This was different from matter and anti-matter in that "negative mass" would be made up of "negative energy."

    I know that negative energy can be produced in tiny quantities, and I also know that negative energy is part of Kip Thorne's theory of expanding quantum foam into "time portals."

    So what is the theoretical status of negative mass? Still speculative? Unsupportable? totally bogus?
  2. jcsd
  3. Oct 14, 2003 #2

    I am not able to answer the question about the status of research or thinking on the subject of negative matter in the context you propose.

    How ever. one thng I have learned over the years is that everything can be found in some way to be inverseable. And I tend to think that if something can't be inverted then it aint real. So as far as I am concerned the concept of negative matter is a very real possibility and certainly worth consideration. But possibly i would use the words Inverse matter rather than negative matter because converse matter as such has both negative and positive polarities and therefore so to would inverse matter. (negative matter)

    I have been exploring the concept of dimensional reflections. That matter can be seen from the inside as it can from the outside. A bit like an inverse sphere if you can imagine it.

    Another way of describing it is like when you face a mirror and imagine what you see to be a reality in the mirror. The story of Alice in wonderland comes to mind. Now if we allow this to sink in for a moment you will see that inverse matter could be what you are seeing in the mirror. If you think of all positive or converse matter as being a mirror even though you can't see it you can understand what I am writing about.

    Because it is negative or inverse matter how else would you expect to experience it?
  4. Oct 14, 2003 #3

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper

    I am presently attempting to contemplate an inverse sphere. Any suggestions as how to model such a thing?

    And on the subject of using the term "inverse," would it follow that the charge of the proton would be the "inverse" of the charge of an electron?
  5. Oct 14, 2003 #4
    To model an inverse sphere I think can only be done conceptually with the imagination. Because of it's nature it would be impossible to draw or build. with out some really heafy dimensionalism.

    I think a negative charge could be considered as inverse to the positive. However to inverse both one would not use the word negative to describe the inversion of both positive and negative charges as I would think this as confusing...My opinion only
  6. Oct 15, 2003 #5
    Might an inverse sphere be like an antibubble? An antibubble is like a normal bubble of gas in a liquid, but it then has a small bubble of liquid in its center, very weird, but they do exist. Apparently they are small, that way the surface tension of the gas is enough to keep the little bubble of liquid inside it from hitting an edge and becoming part of the liquid the now normal bubble is in.
  7. Oct 15, 2003 #6


    User Avatar

    In general relativity/cosmology there are things which behave like they have a negative active gravitational mass. One such thing is a Vacuum Domain Wall.

    See -- http://www.geocities.com/physics_world/domain_wall.htm

    The dark energy, that which is causing the universe to expand at an accelerating rate, acts like a negative active gravitational mass too.

  8. Oct 15, 2003 #7

    I think what you are describing is a converse sphere inside a converse sphere. If I understand correctly. Mind you the anti bibble insight was very interesting all the same
  9. Oct 15, 2003 #8

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper

    I figured that much, but what parameters does the inverse have? Consider a bubble: is an inverse bubble the same but with a negative radius?

    Or perhaps it is the same bubble with the inner surface on the outside and outer on the inside?

    Or perhaps it is the same bubble but with the two mediums reversed?

    DO you have a mathematical model? Would the surface be determined by hyperbolic sine and cosine functions (sinh and cosh) rather than sine and cosine funtions?

    just trying to try to picture it
  10. Oct 15, 2003 #9

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper

    Re: Re: Negative Mass

    Thanks Pete, that's what I was looking for!
  11. Oct 16, 2003 #10


    User Avatar

    Re: Re: Re: Negative Mass

    You're welcome. For more on this see


    And especially see the famous article by Hermann Bondi, "Negative Mass in General Relativity", Reviews of Modern Physics 29, 423 (1957).

    If you'd like I can scan this article in and e-mail it to you. Just send me an e-mail at peter.brown46@verizon.net

  12. Oct 16, 2003 #11

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper

    Thanks again. I'll take a look around for the article. I might come back to you in a while if I can't locate it.
  13. Oct 16, 2003 #12

    some thoughts that may be interesting.

    Imagine we have a star and a planet orbiting the star. and that's all we have.

    The planet is orbiting and because of this it is applying a centrifugal pressure on the star. The stars position always being relevant to the planet.

    Logically this would not work to well if we want the star to stay relatively still in its role as fulcrum.

    Logically we would have to have a counter balance on the planet on the other side of the star.

    Negative mass comes to the picture. but inversley applied..( I looove that word...inverse)

    So we have this phantom negative mass on the other side of the star but to countwieght the planet it has to have mass ( a centre of attraction) in this dimension so it's mass attraction is inverse to the negative mass.

    Or for a better way to describe it exists in the realms of neg mass dimension but it's actual mass value and not the negative physical mass is in the planets positive dimension. so we have a counterbalance to the planets pull on the star. And theoretically this could be applied to all planets so that when the planets lign up there is no effect on the suns position as the counter balancing would neutralise it.
    May be if we look for a counter balance for Mars when it is in a good position we may detect something...just an idea.

    I do remember reading some where some one working on this possibility but I can't remember the details
    Last edited by a moderator: Oct 16, 2003
  14. Nov 24, 2003 #13
    I hope this addresses the above mentioned 'thoughts'.

    An orbiting star/planet pair does not require any negative mass or anti-matter counter weight, since both objects actually orbit the centre of mass between them.

    The centre of mass can be anywhere from close to the centre of the star to somewhere upto, say, a third of the way from the star to the orbiting planet, depending on the mass ratio of the two.

    It is this fact that causes distant stars to appear to 'wobble' at the rate of the period of rotation of the planet. This has allowed astronomers to identify systems that contain orbiting planets in the hope of finding other planets similar to our own.

    The only thing you will find on the opposite side of the Sun from Mars is an infintesimally small increase in gravity due to the tiny increase in mass as seen in the direction of the Sun from the point.

    In fact, I once read that the increase in the gravitational pull on the Earth due to a complete line up of all the planets (not actually possible due to offsets in their orbits) would be less than the pull due to a fully laden 737 flying at 30,000 feet.

    So, no counter ballance, and, since there is no lever, I guess that means no fulcrum!

    I believe a search for negative mass in the real world will only lead to a reduction of the time you could be doing more fruitful things with. Good luck.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook