• Question: If an object has 0 density therefore gravity has no effect on it. So if an object has 0 density it must have no mass, therefore it wouldn't exist. Is it possible to have 0 density and still have mass?

    Asked by curryman96 to Laura, Lily, Mark, Paul, Sarah on 22 Jun 2010 in Categories: .
    • Photo: Paul Roche

      Paul Roche answered on 22 Jun 2010:

      Ooh, tricky one – gravity depends on mass, not density (but density is mass divided by volume, so in effect you can say that gravity and density are related). If you have no mass, you have no gravitational force – but things without mass can still exist!

      Photons (particles) of light have no mass, but they exist – your eye is detecting them now as you look at this screen. Planets, stars and galaxies can affect photons, even though the photons have no mass – but this is because these objects (planets etc.) are so massive that they actually bend the space around them. So as a photon whizzes past them, it’s movement is bent (because the space it is travelling through is bent), and it changes direction.

      So no, it’s not possible to have zero density and still have mass, but things with no mass do exist.

    • Photo: Lily Asquith

      Lily Asquith answered on 22 Jun 2010:

      no it is not possible, density is mass/volume. BUT it is possible for an object to exist if it has no mass. Light particles (photons or x-rays or gamma rays, all the same particle) have no mass but they exist.

    • Photo: Mark Roberts

      Mark Roberts answered on 22 Jun 2010:

      No it’s not possible as an object if it has mass must have atoms and must have some density even if it’s very low

Comments

  • Photo: curryman96

    curryman96 commented on :

    Thanks for that, just was unsure. I now understand what density actually represents, I didn’t realize that density was mass/volume and thought that density was just the amount of gravitational pull an object has.