Timeline for Why doesn't the Earth accelerate towards us?
Current License: CC BY-SA 4.0
31 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Feb 16, 2020 at 6:52 | answer | added | Gilgamesh | timeline score: 2 | |
| Feb 2, 2019 at 14:20 | answer | added | Ed999 | timeline score: 1 | |
| Jan 18, 2019 at 14:30 | vote | accept | whae | ||
| Jan 18, 2019 at 14:30 | vote | accept | whae | ||
| Jan 18, 2019 at 14:30 | |||||
| Jan 18, 2019 at 0:06 | comment | added | Infiltrator | I came here for all of the "it does" answers. | |
| Jan 17, 2019 at 15:46 | answer | added | dexaler | timeline score: 3 | |
| Jan 16, 2019 at 18:36 | comment | added | phoog | @EricLippert I have, to a rather low degree of precision, computed the expected displacement of the earth during a Michael Jordan jump shot, but my budget is certainly insufficient to measure this displacement. | |
| Jan 16, 2019 at 18:33 | answer | added | Mozibur Ullah | timeline score: 3 | |
| Jan 16, 2019 at 18:28 | answer | added | phoog | timeline score: 3 | |
| S Jan 15, 2019 at 20:50 | history | suggested | Peter Mortensen | CC BY-SA 4.0 | Copy edited. |
| Jan 15, 2019 at 20:16 | review | Suggested edits | |||
| S Jan 15, 2019 at 20:50 | |||||
| Jan 15, 2019 at 17:42 | comment | added | Bill N | (continued) There is also an upward force on you due to the electromagnetic interaction of the molecules of your feet with the molecules in the floor. We label this force a "normal" force. and it is NOT a Newton's 3rd law pair with your weight. | |
| Jan 15, 2019 at 17:42 | comment | added | Bill N | @AdityaBharadwaj It seems to me that you are confusing acceleration with gravitational field strength. In a local reference frame fixed to the floor where you are standing, you are not accelerating (and neither is the earth) even though there is a gravitational force on you (due to the earth's gravitational field at your center of mass). The strength of that field is about 9.8 N/kg, but your are NOT accelerating in that reference frame. | |
| Jan 15, 2019 at 17:04 | answer | added | Xosmos | timeline score: 4 | |
| Jan 15, 2019 at 15:46 | comment | added | Eric Lippert | That's great. While you are thinking about this problem: unlike you, the moon is hanging over the earth, and unlike you, the moon does have enough mass to seriously pull on something the mass of the earth. Is the earth observed to accelerate towards the moon? | |
| Jan 15, 2019 at 15:46 | comment | added | JiK | "or explain why such an experiment is infeasible given my budget" I've heard funding of science is being cut all the time, but I hope we can still afford to jump! | |
| Jan 15, 2019 at 15:39 | comment | added | whae | @EricLippert From now I will try to be a better scientists by not making assumptions that are not supported by hard evidence | |
| Jan 15, 2019 at 15:31 | comment | added | Eric Lippert | So how will you do that computation? You'll start by drawing a free body diagram that shows all the relevant forces: the gravity force of the earth on you, the gravity force of you on the earth, the normal force of the ground against your feet, and the normal force of your feet against the ground. When you draw that diagram, what do you predict about the net acceleration? Now do the same process for someone jumping. How do those forces change over time, and what is the effect on the positions of you and the earth? | |
| Jan 15, 2019 at 15:24 | comment | added | Eric Lippert | You say "this thing should happen, but it clearly does not". You should get out of that habit as a scientist. Better: "this thing should happen, I will compute the expected effect and either design an experiment that confirms or denies the expectation, or explain why such an experiment is infeasible given my budget". | |
| Jan 15, 2019 at 15:05 | comment | added | Mazura | I wouldn't call -slightly changing the orbit of Earth because you jumped and then landed, causing some of that energy to convert into heat- a 'force canceling out', but okay ;p | |
| Jan 15, 2019 at 15:00 | history | tweeted | twitter.com/StackPhysics/status/1085189869268135937 | ||
| Jan 15, 2019 at 14:56 | answer | added | Aubreal | timeline score: 14 | |
| Jan 15, 2019 at 14:52 | comment | added | whae | @Mazura Now I understand that even though the acceleration is constant it is so tiny that it would take a really really really long time for the velocity to build up to a quantity that is noticeable. Before getting an answer to this question I thought that the velocity would eventually build up to a noticeable quantity because of a constant acceleration but didn't know that it would take a really long time.But anyways this talk is all useless because there is no acceleration as the force cancels out. | |
| Jan 15, 2019 at 14:38 | comment | added | Mazura | Just because you can't observe something happening doesn't mean it didn't. | |
| Jan 15, 2019 at 11:45 | comment | added | PM 2Ring | Also see physics.stackexchange.com/questions/3534/… | |
| Jan 15, 2019 at 9:53 | vote | accept | whae | ||
| Jan 18, 2019 at 14:30 | |||||
| Jan 15, 2019 at 9:49 | history | edited | Qmechanic♦ | CC BY-SA 4.0 | edited tags |
| Jan 15, 2019 at 9:14 | answer | added | Steeven | timeline score: 112 | |
| Jan 15, 2019 at 8:48 | comment | added | whae | @Steeven Acceleration is indeed exceptionally tiny because of the mass being exceptionally large.In this case the gravitational force that we exert on the Earth is constant.Therefore, there will be a constant acceleration.The acceleration is and will remain tiny but its velocity will slowly build up due to a constant acceleration. That's what I think | |
| Jan 15, 2019 at 8:39 | comment | added | Steeven | What do you mean that it clearly does not happen? If the acceleration is exceptionally tiny (because the mass is exceptionally large), then maybe you just don't notice? | |
| Jan 15, 2019 at 8:33 | history | asked | whae | CC BY-SA 4.0 |