I was wondering what is the smallest unit of measurement possible. I found from google that it is Planck length but it was mentioned that any microscope couldn't see it. Then why is it even a unit of measurement? And how did they discover it or made it?

Is there inertia in absence of gravity? If I was in a region of space with zero gravity, would I have to apply some force to accelerate a massive body?

I've watched The Truth About Gravity With Professor Jim Al-Khalili | Gravity And Me | Spark where astronaut Chris Hadfield says at 3:55: To come back to Earth is violent Then after several seconds of music and video of descent it can be five times the force of gravity...for quite a long time ...

I'm aware my question may not even make sense when considering quantum physics, but please excuse my ignorance. We are taught in school that there are basically 3 particles that make up atoms (protons, neutrons, electrons) and that broadly for each 1 proton there will be 1 neutron and 1 electron....

I have heard in popular science that there is a law of "conservation of information." Some times this is described as: for any event that happens, there is enough information to reconstruct the original state. So for example if you knew the exact positions of the atoms that flew off a burning pie...

I was carrying my friend around the other day when I was spinning her she was light but when not spinning her and just carrying her around she was heavy, why is that?