Per XKCD, nothing significant would happen. Even if all the people were standing in roughly the same area, the Earth would be moved by "less than an atom's width." If people were spread out randomly across the Earth, all the forces effectively cancel, and even less happens.

https://www.youtube.com/watch?v=p2M8Y0z9Rl0

Splash.

If 8 billion humans displace 50 gallons each, thats 400 billion gallons. The volume of all oceans is about 1.5 billion cubic kilometers, which is 3.96258e20 gallons.

Eh, I got tired of trying to do that math, but thats a big frickin difference. I dont think the sea level rise would be measurable.

Actually, I’m a physicist from the world famous ETH in Zürich Switzerland, and my team and I have been working on exactly that question for the past five years! We have created an exciting theoretical model (manuscript has been submitted to PNAS, in second round of corrections). We are now focusing on a series of experiments to substantiate our theoretical findings. Alas, Switzerland is a notoriously landlocked country, due to which such experiments are hard to realize. In addition, strict nudity in public laws apply. As a result, all our grants were canceled, and we are now unemployed.

Would there be a difference if we voting slowly, one by one?

Could you explain this sentence like I'm dumb?

Nothing noticeable. Eight billion people times 100kg average mass, divided by 360 million square kilometers of ocean surface equals 2222kg/square kilometer. Or, assuming the density of a human being 1, a 2.22mm height difference. Ah, the joys of metrical calculations.

If you liquefied every human on earth and poured them all into one cube, it would only be about 800M per side. Humans collectively aren't that significant.

For comparison all insects would take up a 1km cube.

There'd be a lot of piss mixed in.