# Do all the objects in the universe exert force on all other objects?

Do all the objects in the universe exert force on all other objects? Like a type of gravity; also, how much does it decrease as it gets farther away?

-
Curious about your thinking behind the wording "like a type of gravity". Are you seeking a force with infinite reach other than gravity? –  BobStein-VisiBone Sep 24 '13 at 23:51
@BobStein-VisiBone Maybe magnetism? –  Timtech Sep 24 '13 at 23:52

Yes - this is the formula:

$$F = G\frac{m1 * m2}{r^2}$$

Using this equation, we can say that all atoms in the universe exert force upon eachother. One carbon-12 atom has a mass of $1.660538921(73)\times10^{-27} kg$. That's a crazy small mass.

Now let's say that these two atoms are 100,000,000 light years apart. That's $9.461\times10^{23} m$, which is a very long distance.

Now, if we plug these values into our equation, we get that the force is: $1.709191430132 \times 10^{-59} N$

That's a very, very small amount of force. But it's still force.

-
So do I emit a gravitational force? –  Timtech Sep 24 '13 at 23:53
@Timtech Yes - every atom (that we know of) does. –  Undo Sep 24 '13 at 23:54

All objects in the universe exert a gravitational force on all others - the farther away an object is, the smaller is the force it exerts. (The force is inversely proportional to square of the distance from the object, so an object twice as far away means only 1/4 the amount of force). Furthermore, the more massive the object, the greater the force it will exert on other objects - twice the mass means twice the force. So nearby, massive objects, dominate the gravitational force on other objects.

Source: Frequently Asked Questions About General Astronomy, Compiled by Dr. John Simonetti of the Department of Physics at Virginia Tech.

-
I completely agree with @TildalWave. This arguably lowers the quality of Q&A sites like these. It is not our place to restrict or police all questions or answers on this site, but you do the community a huge disservice by doing things like this. –  astromax Jan 14 at 19:22
@astromax I'm sorry, I'll refrain from doing it again. –  Timtech Jan 14 at 22:04

No. It's impossible for every object to interact with every other object, due to the assertion by general relativity, that the universe can, and is, expanding faster than the speed of light.

I then assume that the universe initially was expanding at, or close to the speed of light, and that it immediately after the big bang was expanding faster than the speed of light.

Some of the particles/forms of energy that would have reached us are also bound to have been "held back or deflected", even in the young stages of the big bang, and are now at a distance at which they can never reach us. They could have been held back by for example a black hole.

Potentially, if the expansion of the universe at one point was so slow that gravity from every particle had time to propagate to every other particle, then yes - every particle and energy in the universe affects every other particle.

-
This is incorrect. The prediction from General Relativity is that the graviton is massless, and therefore travels at the speed of light. Additionally, the universe is not expanding faster than the speed of light within our cosmological horizon. –  astromax Jan 14 at 19:19
@astromax But there are objects outside of our cosmological horizon? The diameter of the universe is estimated to be some 93 billion light years. –  frodeborli Jan 14 at 23:48
The graviton is also a hypothetical particle which has yet to be observed, and it will most likely never be observed unless it has mass. –  frodeborli Jan 15 at 0:04
The graviton has not yet been discovered directly, but I don't know why you say it will most likely never be observed unless it has mass. It is believed to be a massless particle, and this is why it travels at the speed of light. However, there is indirect evidence that gravitational radiation (gravitons) do in fact exist, and a nobel prize(nobelprize.org/nobel_prizes/physics/laureates/1993/illpres/…) was awarded for this work. We do not know whether or not there are things outside of our horizon. We can neither see them nor feel their effects since all particles are.. –  astromax Jan 15 at 0:27
restricted to traveling at the speed of light. Your original statement remains incorrect. –  astromax Jan 15 at 0:28