I've been reading through this thread and finding it pretty enjoyable, but spent a lot of it thinking that referencing the right experiments could easily disprove this. However, I took the time to look at a couple of the videos posted and noticed some hand waving that conveniently "refuted" some of these results.
(P.S. I realize this is trolling, but its been interesting and funny so far. Hopefully a Flat earther can provide some entertaining and possibly even thought provoking response to what I'm about to post.)
For example, the fact that we can measure the gravitational constant "should" put to rest the idea that there is no such thing as gravity. This is something we've been experimentally able to do for a long time: in the 1790's Cavindish experimentally found the gravitational constant to be G = 6.74×10−11 (m^3 kg^–1 s^−2), which allows for calculations of weight that agree nicely with more "standard" ways of measuring weight. This would seem to "prove" the theory of gravity correct. (more info on the experiment here:
https://en.wikipedia.org/wiki/Cavendish_experiment
)
However, in one of the video series that legit question frequently references (Balls out physics, specifically this video:
https://www.youtube.com/watch?v=heiznYx-Ryk
), there is seemingly serious doubt cast the results of this experiment. The person who made the video claims (around 20 minutes in, I don't feel like rewatching it so if anyone's interested they can find the exact quotes) that nobody has been able to use the same techniques to reproduce the experiment's results and goes on farther to say that Cavindish, being so confident in Newton's equation, just algebraically solved for the value of G based on known weights.
There are several things wrong with what he claims in the video of course. First, he states that Cavindish found our currently accepted value of G. He didn't: the value he calculated is different from the currently accepted value by about 1%. Furthermore, his claim that nobody has been able to replicate the results of this experiment are completely false, and discovering this requires going no farther than a basic wikipedia or google search. This experiment has been repeated several times with increasingly precise equipment, each time refining the value of G be more accurate. This is easily seen just from wikipedia, which talks about a couple experiments of this nature (i.e. a similar, more accurate one carried out by C.V. Boys:
https://en.wikipedia.org/wiki/C._V._Boys#Experimental_physics
, or an earlier but less accurate attempt:
https://en.wikipedia.org/wiki/Schiehallion_experiment
). Of course, if you don't want to trust wikipedia and are looking for more modern versions of the experiment, this is actually still an area of some research (since G is so small, physicists are still refining the results to be accurate past the first several decimal places). Examples of these expirements can be found here:
http://physics.nist.gov/cuu/pdf/RevModPhysCODATA2010.pdf
(pages 49-50) by googling the individual data points and IDs in table XXIV.
So Brian Mullin is seemingly lying about this fact in his video to dupe people not willing to do any research at all. If you don't trust scientists, some of the engineers who claim to be flat earthers could probably build the torsion balance themselves and confirm the results.
A couple other experimental things that support the earth's rotation or gravity include:
The Foucault pendulum, which seems to confirm that the earth rotates (again, just go to a museum or if you're really dedicated you can replicate this yourself):
http://www.animations.physics.unsw.edu.au/jw/foucault_pendulum.html
and
https://en.wikipedia.org/wiki/Foucault_pendulum
The experimental confirmation of the theory of general relativity (which reduces to the classical gravity theory under "normal" conditions:
http://www.bartleby.com/173/a3.html
https://en.wikipedia.org/wiki/Tests_of_general_relativity
Also, it's referenced several times in this thread that density is what causes things to fall or rise and in the quotes provided by legit question its stated that less dense feathers, one blown on or disturbed, won't fall at the same rate as more dense rocks. Even the Balls Out Physics video discusses how ridiculous this is and links the proof that it's wrong:
https://www.youtube.com/watch?v=E43-CfukEgs
Well, reading up on this stuff has been fun and interesting. Hopefully you guys have some good replies.