General Relativity says that acceleration = weight. Suppose I am sitting on the Earth's
surface. I weigh 200 pounds. I seem to myself to be motionless. Nor does my
weight appear to be changing. Where and how am I accelerating?
.
Now suppose I am in free fall. I think I am accelerating. Relativity says I
might as well think of myself as adding weight. But I think I weigh nothing.
What have I got wrong?
I do not understand General Relativity?
- Posted:
- 3+ months ago by fhapgood
- Topics:
- general relativity
Details:
Answers (2)
Your stationary weight, or more accurately mass, has nothing (as such) to do with GR and a lot more to do with gravitational attraction. Your mass increases as you accelerate so if you sat on a pair of scales and went up in a rocket under acceleration you would see your mass increase. If the rocket didn't launch your weight would remain the same.
If you are in free fall you have acheived terminal velocity under the effect of gravitation and as such you weigh nothing, you are in effect weightless. During the initial acceleration to terminal velocity your mass would have increased but once acheived it would drop back to your normal mass. Consider if you were in free fall with no external stimuli, if you were in a cardboard box for example, you would feel weightless and that is exactly what astronauts on the international space station experience.
Ok well - "I am interested in issues around weight, not mass" - Mass and weight are the same thing with the distinction that weight is determined by mass under the influence of gravity. For example a 1 kg (mass) object on earth weighs 1 kg, if it was in space it would weigh nothing but it's mass would still be 1 kg. This distinction is important when discussing your original question.
"I have no interest in inertia." - I made no mention of inertia.
"Are you saying that there is more than one explanation for weight?" - weight is relative, your mass is not. A 1 kg object on Earth weighs 1 kg. The same object on the moon weighs 170 grams (approx. 1/6th), if you took that 1 kg object to Saturn it would weigh 8 kgs all simply because of the effect of gravity on mass.
"How do people tell the difference?" - See this: physics.stackexchange.com/questions/179269/how-do-we-measure-mass
I'm sorry. I think neither one of us is understanding the other.
Neither does anybody else. That theory has never been fully accepted. Einstein said once "If you can't explain what you know so a bar maid understands it, you don't know it." Oddly, he never offered an explanation on that level, and everybody else only wants to baffle the bar maid with baloney.
My. I am more confused than ever. First of all, I am interested in issues around weight, not mass. I care about the interaction of matter and gravity. I have no interest in inertia. Or so I think. (I could be persuaded otherwise.) Second, and more important, are you saying that there is more than one explanation for weight? Some of which have something (or everything) to do with GR and some which have "nothing" to do with GR? Wow. I thought there was only one explanation for weight, the GR one, ever. Is this really what you are saying??? How do people tell the difference??