Actually my question is more: what is a force?
I know that, for example, gravity is due to the so-called gravitons, but how can a massless thing attract something? And does that thing have energy?
Answer
Dear Koen,
Your “what is” questions are the kind for which there is no real answer.
“what is a force”? I only know an indirect definition: F=m*a, or: a force is something that can give an acceleration to a mass. And if there is no acceleration, it means that the sum of all the acting forces is zero. For example: we experience gravity, and if we were to jump out of an airplane, we would fall down with an acceleration g(=9.81m/s2). On the ground, however, an opposing force arises between the soles of our feet and the ground that precisely cancels out the force of gravity.
Gravity (gravity) is the attraction between massive particles. “Gravitons” are hypothetical particles that, like photons for electromagnetism, “would transmit” gravity. But gravitons have never been observed (and what about gravity itself? 🙂 nor have they been fitted into a consistent scientific framework or model. All that is roughly known is that they themselves must be massless if they existed, just as photons are chargeless.
Indeed, a massless thing cannot attract.
Energy: Supply of energy is the result of displacement with a force. E=F*s, energy is force * displacement. If you fall out of your plane and accelerate with gravity, you get “kinetic” energy, which you lose in one fell swoop when landing.
Answered by
Engineer Bart Dierickx
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