I have always studied that where there is a body with mass, there is gravitational pull.

So can small chunks (or dust) of cosmic matter revolve around artificial satellites in space? Or rather are they? Haven't seen traces of them in space movies or space photos though.

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    $\begingroup$ Radiation pressue (and perhaps eventual collisions with the particles in solar wind) is larger and blows such dust out of these orbits, at least if you imagine them far enough from earth that our magnetosphere deflects much of the solar wind by even stronger forces on moving ions. Dust does exist in all sizes, though, usually speeding past satellites at speeds where the rare impact of almost anything of human-perceptible size can be dangerous. Operational risk, and apparently a calculable one. $\endgroup$
    – pyramids
    Feb 27 '15 at 9:25
  • $\begingroup$ So, there can be orbits, but theoretically. The weak gravity is not a reason, because of the low mass of the cosmic matter. But the speed at which they travel in space prevent them from forming orbits, and also even if their velocity can be less, which is only possible in theory, they will be blown away by radiation pressure. It's simply as if an ant can't run on the surface, because it is being blown away by strong gust of wind. Have I got the facts right? $\endgroup$ Feb 27 '15 at 9:34
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    $\begingroup$ You might be interested to calculate the orbital velocity for some sample systems. The equation is $$v = \sqrt{\frac{GM}{r}}$$ where $M$ is the mass of the artificial satellite, $r$ is the radius of the orbit and $G$ is Newton's constant. $\endgroup$ Feb 27 '15 at 10:11

Yes everything with mass has it's own gravitational pull, but it's very very tiny that we never see it in our daily life.

To see the difference let's estimate the acceleration that act on some object which is one meter away from a mass of 1000 kg compare to gravity of the Earth:

$$ \begin{align*} M_E &\approx 10^{24} kg\\ R_E &\approx 10^6 m\\ g&=\frac{GM_E}{R_E^2}\approx 10 \:m/s^2 \end{align*} $$

now for our example: $$ \begin{align*} a &= \frac{Gm}{r^2}\\ &= \frac{G(10^3 kg)}{(1\:m)^2}\\ &\approx \frac{G(10^{-21}\:M_E)}{(10^{-6}R_E)^2}\\ &\approx 10^{-9}g \approx10^{-8}\:m/s^2 \end{align*} $$

You can see that even when you stand at only 1 meter away from a ton of mass, you will still feel nothing at all. That's why you never see the effect of gravity of any object in your daily life.


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