zero G

[stones1]

Are we, that is the earth, freefalling through space thus enducing the effect of weightlessness. Just wonderin if anyone knows. thanks

[ydoaPs]

Free falling toward what?

[swansont]

As a whole, we are in freefall with respect to the sun, just as the ISS is in freefall about earth, owing to the orbit.

[liber_scientia]

I don't understand.

The Earth's gravity is what acts against weightlessness for us. Beyond that, the Earth is trapped in orbit by the sun's gravity.. so what weightlessness do you mean?

[spirytus]

Are we, that is the earth, freefalling through space thus enducing the effect of weightlessness. Just wonderin if anyone knows. thanks

 

The earth is not freefalling through space. The word freefall is misleading.

 

The earth is falling into the sun while at the same time hurdling perpendicularly to the sun at aprox 30 km per second - effectively establishing an Orbit.

 

An orbit around an object in space is essentially when the perpendicular velocity counters the pull of gravity (of said object). At this point you no longer feel the effect of gravity, hance you achive weightlessness.

 

You could say the earth is caught in an free fall towards the sun, but because of its current orbital velocity its esencially an infinite free fall hance we dont feel sun´s gravity.

 

Imagine a ball (earth) attached to a string (force of the suns gravity) while you spin it above your head (the sun) at a constant speed (a steady orbit).

 

If the ball slows down, it will smack you in the face. If it speeds up the string will break and the ball will hurdle off into space.

 

Note, this is a very basic model. What actually happens in space is a bit more complicated.

 

So, basically, the ISS is in orbit around the earth, the earth is in orbit around the sun, the sun is in orbit around the core of our galaxy, while the galaxy itself is hurdling away from the point of the big bang.

Edited December 22, 2008 by spirytus

[D H]

The earth is not freefalling through space. The word freefall is misleading.

In what sense? The Earth is perpetually accelerating sunward due to gravity, impeded only by an immeasurably small drag against the interplanetary medium. Freefall.

 

An orbit around an object in space is essentially when the perpendicular velocity counters the pull of gravity (of said object). At this point you no longer feel the effect of gravity, hance you achive weightlessness.

There are at least a couple of misunderstandings here. (1) The perpendicular velocity does not counter the pull of gravity. That pull is always there. (2) Weightlessness (the feeling of weightlessness) results whenever the acceleration of some body is (nearly) equal to the acceleration induced by gravity. This condition is the norm in outer space but can also be forced (e.g., the Vomit Comet and some amusement park rides).

 

You could say the earth is caught in an free fall towards the sun, but because of its current orbital velocity its esencially an infinite free fall hance we dont feel sun´s gravity.

The Sun raises tides. While we can't feel tides in our body (too small), they do exist, and Sun-induced tides can be seen in larger bodies of water.

[Kyrisch]

The earth is not freefalling through space. The word freefall is mislewhile the galaxy itself is hurdling away from the point of the big bang.

 

And, while we're picking nits, there is technically no "point of the big bang".

[spirytus]

And, while we're picking nits, there is technically no "point of the big bang".

 

Curious, I was under the impression that the cosmos is currently expanding outwards in all directions - an expanding sphere.

 

An expansion would imply an explosion (event). You telling me there is no spatial point of origin?

 

I hope I dont come out defensive, I´m honestly curious...

[Sisyphus]

Curious, I was under the impression that the cosmos is currently expanding outwards in all directions - an expanding sphere.

 

An expansion would imply an explosion (event). You telling me there is no spatial point of origin?

 

I hope I dont come out defensive, I´m honestly curious...

 

This is obviously OT, but quickly: That's a common misconception. The cosmos is indeed currently expanding. However, it's not exapnding "outward," and there is no point of origin. Stuff in the universe isn't "moving" overall, per se, it's just getting farther apart, because space itself is expanding. It's difficult to visualize, since it doesn't really work in the normal 3D way we're hardwired to think in, but there have been plenty of topics here about it.

[Davros]

A simple way to look at the expansion is to drop down one dimensional level. (saw this metaphoric example in New Scientist many months ago) ....

 

Imagine a 2D world on the surface of a 3D balloon. A spider sits on the surface. Expansion takes the form of the balloon enlarging .... resulting in all 'space' on the surface moving away from each other at the same time (but the spider not pulled apart - as in our 3D universe, we and the galaxy have enough gravity to 'fight' expansion for the time being).

[Pete]

Are we, that is the earth, freefalling through space thus enducing the effect of weightlessness. Just wonderin if anyone knows. thanks

By definition the term freefall means that the only force acting on a body is the force of gravity. Thus one body orbiting another is in freefall (as in falling freely). In such cases one can construct a locally inertial frame of reference with the body in freefall at the origin. The term weight refers to the force that supports a body in a gravitational field. If there is no supporting force then the body is weightless.