Is there a way to detect the earth’s changing speed as it orbits the sun? I’m thinking of an at home experiment. It would be a plumb bob suspended in a tube about ten feet in length. There would be a laser on the end of the plumb bob that would shine onto an angled mirror at the bottom of the tube. The mirror would cast the reflected image on to a distant wall. Any small movement of the plumb bob would be exaggerated on the wall. Do you think it’s worth my effort to try it, or is it domed to fail. Any ideas/advice will be greatly appreciated. Note: I am aware that other factors will affect the plumb bob, thermal currents being the main one, but I’m hoping that over the course of a year averages/trends would be noticed as a result of earth’s changing speed. I would photograph the image every day for a year.
Asked
Active
Viewed 50 times
1 Answers
1
The force which causes Earth's velocity to change as it goes around the sun is the gravitational force, $$ F_\text{grav} = G M_\text{sun} m_\text{thing} /r^2$$
Since the Earth and your plumb bob both have zero mass relative to the Sun, they will have the same acceleration and no relative movement. So any motion of your plumb bob relative to its mount will be from other sources: vibrations, air currents, etc.
The first-order correction to this fact, where different parts of the Earth are attracted differently to the Sun, causes the difference between "spring tides" and "neap tides."
rob
- 89,569
-
Thanks. You saved me the effort. I’m not sure I understand the “zero mass relative to the sun” part though. Do mean because the masses are so small compared to the sun? – Lambda Aug 11 '18 at 18:12
-
1yes, that is what he means, they are negligible. – Zarathustra Aug 11 '18 at 18:27
-
One way to demonstrate the Earth's rotation is to use the pendulum of Foucault. – my2cts Aug 11 '18 at 21:13
-
@my2cts See https://physics.stackexchange.com/q/415531/44126 – rob Aug 12 '18 at 04:12