Re: And what is mass, really?

Mass and Energy are not the same thing

Mass = E/c^2

You can get a great deal of energy from small amount of mass, but very little mass from Energy because you are dividing by the square of light.

1 kilo if converted to energy (100% conversion rate which is impossible) you get enough energy to power 60 THOUSAND homes for a day.

The opposite is also true, to even generate a small amount of matter from energy requires massive (no pun intended) amounts of energy.

We can also define Mass=F/a, and we use (to make things simple) time of flight as a means to calculate mass, but there are other methods available and they all the findings are consistent.

It's true that relativistic effects are observed, this does not apply to our bodies and certainly not our cells. That is why gravity can be observed from accelerations as well as from masses, and time slows down near large masses as well as during accelerations.

According to science, first molecules were the smallest indivisible particles, then atoms, then electrons/neutrons/protons, now quarks. This is true, but the progression always adopted previous observations into the new theory. So the observations of atoms neutrons... ect still hold true. So any new idea that somebody wants to put forth must adopt all the old, datum and observations that we have.

So, we obviously didn't know very much about chemistry/physics and so what makes us think we are significantly closer to understanding it now?

HOw do we know we have reached the end, and learned everything there is to learn about a subject? This question really has no satisfactory answer.

so they must need to have more energy to be able to change their velocity frequently enough to stay in their place?
I really don't understand what you mean here.

Electrons and P/N are made of different stuff. Its not just a matter of size, in a very basic way they are different. The difference is as obvious as Baryons and Leptons (look them up)- or bananas and ananas. [a little humour for the francophonie]