05-07-2003, 05:34 PM
Wha? always gets to it before I can... I was going to respond similarly, that there is no need for a standard. It's just physics. And the comparison to a helium balloon in a large toilet paper tube is a good one the the layman, if you assume there is no friction.
Think of it this way... the liquid is what is being affected by the gravity. If the tube is slightly tipped, the liquid will flow towards the lowest point, just as liquid flows down a slope. As it does so, the bubble is pushed upward by buoyancy, essentially because it is less dense and the liquid is basically heavier. Liquid is filling up where the bubble used to be, being pulled down by gravity, and the gas ends up on the highest point. That's assuming there is a big tip, but you get the idea.
Not sure where this idea of standard comes from... it's the standard set by gravity itself, as Wha said, the axis. I think perhaps the confusion came when maybe someone is thinking that perhaps the picture will be level with gravity, but not necessarily the house... but that's just the thing... houses are level too. So if you have a picture that is level with gravity, it will be even with the floor and ceiling, unless you have a terrible house that has a slope in it.
Put a ball on something that isn't level... it will roll down as gravity pulls it. Same idea. You can feel it when you're on a hill. A level is just simply a more accurate representation of this, when our body can't sense it (either too minute or you aren't standing on it... you're not standing on the picture frame), or when friction prevents it from being noticeable. If the picture frame (an even, rectangular picture frame, not misshapen) was hanging from something and there was no friction, it would settle itself to be perpendicular to the pull of gravity, or parallel if you're referring to the left and right sides of the frame.
Think of it this way... the liquid is what is being affected by the gravity. If the tube is slightly tipped, the liquid will flow towards the lowest point, just as liquid flows down a slope. As it does so, the bubble is pushed upward by buoyancy, essentially because it is less dense and the liquid is basically heavier. Liquid is filling up where the bubble used to be, being pulled down by gravity, and the gas ends up on the highest point. That's assuming there is a big tip, but you get the idea.
Not sure where this idea of standard comes from... it's the standard set by gravity itself, as Wha said, the axis. I think perhaps the confusion came when maybe someone is thinking that perhaps the picture will be level with gravity, but not necessarily the house... but that's just the thing... houses are level too. So if you have a picture that is level with gravity, it will be even with the floor and ceiling, unless you have a terrible house that has a slope in it.
Put a ball on something that isn't level... it will roll down as gravity pulls it. Same idea. You can feel it when you're on a hill. A level is just simply a more accurate representation of this, when our body can't sense it (either too minute or you aren't standing on it... you're not standing on the picture frame), or when friction prevents it from being noticeable. If the picture frame (an even, rectangular picture frame, not misshapen) was hanging from something and there was no friction, it would settle itself to be perpendicular to the pull of gravity, or parallel if you're referring to the left and right sides of the frame.