Viruses can be fairly complex, but imagine the very basic form of what they are: A string of DNA floating around and getting into cells, and causing them to produce more copies of itself. Obviously viruses are more than just rogue DNA, but that's their function - they corrupt other cells. They don't eat, photosynthesis, reproduce, etc. They're much closer to a chemical reaction, like how fire causes wood to create more fire, except orders of magnitude more complicated.

There's lots of interesting details about planetary mass and radius that others have mentioned but I have to wonder... if the question is simply "how strong is the gravity of this planet" then shouldn't that be measurable by simply examining a single orbiting body's velocity and distance, or just dropping something in vacuum and observing the acceleration, or even just taking your kitchen scale to the planet and putting a calibration weight on it?

>meet several friends and infect them. None of them are inclined to quarantine

I don't know if it would be helpful or not, but this argument is a little questionable. You have seen several friends rather than a second gathering, reducing the number of people you infect. Plus you implied that someone cannot opt to see nobody in a social manner for the two days.

Who knows, it could be a waste of time still, but I would give it a little more credit.

Could we make a big difference by encouraging people to reduce contact with others for a couple days after being part of a get together or large, packed event?

Even if it doesn't mean a quarantine, just not going right from one social event to another and saving the next shopping trip for a couple days after you get back should have an impact on virus spread, right?