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

How can we say there is Zero G force in space what about SUN's G ?

  1. Dec 20, 2009 #1

    SBC

    User Avatar

    »

    How can we say there is Zero G force in space what about Sun's G (I mean in our solar system or above Earth )?

    Ok.. General theory of relativity says about bending of space and time. If I throw a rock into space where there is no G force even the small rock should fall towards the Sun(what about Sun's G force it should pull the Rock? ). Does rock stays at same position or it will fall to words the sun according to General theory of relativity (due to bending of space and time )??

    ok... planets revolve around sun (Why planets Revolve around sun why not fall towards sun?)... But the rock doesn't revolve and it should fall towards the sun ... ?

    We say that Suns G force is far Grater that earth and G force of suns range should be high !!
    Than why space shuttle and others don't fall towards the Sun ?

    Than why on earth Zero G force ?

    How can G range be infinity ?

    General theory of relativity says "Force is consequence of Geometry"

    so G range is limited. Why infinite range?
     
  2. jcsd
  3. Dec 20, 2009 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi SBC! Welcome to PF! :smile:
    We don't, we say there is microgravity in space … in a spaceship orbiting the Earth (with its engines off), a book floats because it too is in orbit, and its orbital speed is almost exactly the same as that of the spaceship (exactly exactly only if it is at the same distance from Earth as the centre of mass of the spaceship).

    Using the spaceship as a frame of reference, there is almost zero gravity.

    But in any other frame, there is plenty of gravity, as you say! :smile:
    If you could place the rock stationary, then yes it would fall towards the Sun.

    But if you threw it from Earth, or from a spaceship orbiting the Sun, it would start with all the orbital energy of the Earth or the spaceship, and it would continue to orbit the Sun near the Earth or the spaceship.

    The planets do fall towards the Sun, but they are moving sideways so fast that manage to stay in orbit …

    This is what Sir Isaac Newton realised when he saw the apple fall … if you throw an apple fast enough sideways, it will still fall, but the sideways movement keeps it in orbit. :wink:
    Because the space shuttle orbits the Sun at the same speed as the Earth does.
     
    Last edited: Dec 20, 2009
  4. Dec 20, 2009 #3

    SBC

    User Avatar

    Re: Welcome to PF!

    I like your reply but if planets are not falling towards sun why not stone ?

    How can G range be infinity ?
     
  5. Dec 20, 2009 #4

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Because if the stone is launched from a planet, it will have the velocity of the planet in addition to its launch velocity.
    I don't understand why you're asking this …

    why wouldn't it extend to infinity? why should it stop somewhere? :confused:
     
  6. Dec 20, 2009 #5

    Mentz114

    User Avatar
    Gold Member

    GTR says there is no force, only geometry of space-time, which extends everywhere.
     
  7. Dec 20, 2009 #6

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    Re: Welcome to PF!

    The planets *are* falling towards the Sun. However, their tangential velocities coupled with that inward acceleration makes them orbit the Sun rather than fall straight into it.

    In your original post, you are confusing weight (gravitational force) with apparent weight (everything but gravitational force). We call space a zero-g environment because an astronaut's apparent weight is nearly zero on orbit. An astronaut's actual weight is about 90% that of that on the ground.
     
  8. Dec 21, 2009 #7

    SBC

    User Avatar

    If you are of my age hey BRO !!
    if you are older than me sir,

    2zh01s3.jpg

    look at this .. I don't know why I feel that I found something wrong with sir.isaac newton's Equation.
     
  9. Dec 21, 2009 #8

    russ_watters

    User Avatar

    Staff: Mentor

    I think what you've found is a personal discomfort, nothing more.
     
  10. Dec 23, 2009 #9
    ok... planets revolve around sun (Why planets Revolve around sun why not fall towards sun?)... But the rock doesn't revolve and it should fall towards the sun ... ?


    ------------->it (earth) will fall toward the sun but thats a long time from now


    :wink:
     
  11. Dec 23, 2009 #10

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    No … the Sun will come to meet us! :wink:

    We're so lucky! :tongue2:
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook