BB84
@BB84@mander.xyz
- Comment on your mom falls significantly faster than g 2 weeks ago:
even light can stop following null geodesics because the curvature can be too big compared to the wavelength
Very interesting! How do you study something like this? Is it classical E&M in a curved space time, or do you need to do QED in curved space time?
Also, are there phenomena where this effect is significant? I’m assuming something like lensing is already captured very well by treating light as point particles?
- Comment on your mom falls significantly faster than g 2 weeks ago:
So if I have a spherically symmetric object in GR I can write the Schwarzschild metric that does not depend on the radial mass distribution. But once I add a second spherically symmetric object, the metric now depends on the mass distribution of both objects?
Your point about linearity is that if GR was linear, I could’ve instead add two Schwarzschild metrics together to get a new metric that depends only on each object’s total mass?
But even in a situation with one source, does the shell theorem work in GR? Say I put a infinitely light spherical shell around a black hole. Would it follow the same geodesic as a point particle?
- Comment on your mom falls significantly faster than g 2 weeks ago:
For the bowling ball, Newton’s shell theorem applies, right?
- Comment on your mom falls significantly faster than g 2 weeks ago:
Earth is in this case not an inertial reference frame. If you want to apply Newton’s second law you must go to an inertial reference frame. The 9.81m/s/s is relative to that frame, not to earth.
- Comment on your mom falls significantly faster than g 2 weeks ago:
That is one very impressive feather.
Restricting ourselves to feathers made by non-human animals
🤔🤔🤔
- Comment on your mom falls significantly faster than g 2 weeks ago:
the original title was “your mom false significantly faster than g”
- Comment on your mom falls significantly faster than g 2 weeks ago:
Re your first point: I was imagining doing the two experiments separately. But even if you do them at the same time, as long as you don’t put the two objects right on top of each other, the earth’s acceleration would still be slanted toward the ball, making the ball hit the ground very very slightly sooner.
Re your second point: The object would be accelerating in the direction of earth. The 9.81m/s/s is with respect to an reference frame (say the center of mass frame). The earth is also accelerating in the direction of the object at some acceleration with respect to the inertial reference frame.
- Comment on your mom falls significantly faster than g 2 weeks ago:
Nope. The argument only works if you conjured the bowling ball and feather out of
thin airvacuum. lemmy.world/comment/13237315 discusses what happens when the objects were lifted off earth. - Comment on your mom falls significantly faster than g 2 weeks ago:
I didn’t think about that! If the object was taken from earth then indeed the total acceleration between it and earth would be G M_total / r^2, regardless of the mass of the object.
- Comment on your mom falls significantly faster than g 2 weeks ago:
Okay how about now
- Comment on your mom falls significantly faster than g 2 weeks ago:
@WolfLink@sh.itjust.works and @theturtlemoves@hexbear.net are correct
- Comment on your mom falls significantly faster than g 2 weeks ago:
fixed it sorry
- Comment on your mom falls significantly faster than g 2 weeks ago:
I meant cross-section area, not surface area. Sorry. Edited my comment above.
- Comment on your mom falls significantly faster than g 2 weeks ago:
If your bowling ball is twice as massive, the force between it and earth will be twice as strong. But the ball’s mass will also be twice as large, so the ball’s acceleration will remain the same. This is why g=9.81m/s^2 for every object.
But the earth’s acceleration would not remain the same. The force doubles, but the mass of earth remains constant, so the acceleration of earth doubles.
- Comment on your mom falls significantly faster than g 2 weeks ago:
Here’s a problem for y’all: how heavy does someone’s mom have to be to fall 10% faster than g? Just give an approximate.
- Comment on your mom falls significantly faster than g 2 weeks ago:
Even in a perfect vacuum the bowling ball still falls faster. See my comment sibling to yours.
- Comment on your mom falls significantly faster than g 2 weeks ago:
Yes, the earth accelerates toward the ball faster than it does toward the feather.
- Comment on your mom falls significantly faster than g 2 weeks ago:
A feather has smaller surface area than a bowling ball. But drag acceleration is proportional to the surface area divided by the mass (and this quantity is indeed smaller for the bowling ball).
- Comment on your mom falls significantly faster than g 2 weeks ago:
When the earth pulls on an object with some F newtons of force, the object is also pulling on the earth with the same force. It’s just that the earth is so massive that its acceleration F/m will be tiny. Tiny is not zero though, so the earth is still accelerating toward the object. The heavier the object, the faster earth accelerates toward it.
Both the bowling ball and the feather accelerates toward earth at the same g=9.81m/s^2, but the earth accelerates toward the bowling ball faster than it does toward the feather.
- Submitted 2 weeks ago to science_memes@mander.xyz | 120 comments
- Submitted 2 months ago to science_memes@mander.xyz | 4 comments
- Comment on I don’t understand quantum physics 3 months ago:
You should upload this as a post!
- Comment on I don’t understand quantum physics 4 months ago:
Yeah maybe shift the X scale by 40 IQ points and it would be accurate.
- Submitted 4 months ago to science_memes@mander.xyz | 9 comments
