That’s a very natural question — and the short answer is:
Yes, gravitational force originates from mass, but in modern physics, especially after Einstein, we need to say more than just that.
Let’s break it down into classical and modern views:
🌍 1.
Newtonian View
(Classical Physics)
In Newton’s law of universal gravitation:
F = G \frac{m_1 m_2}{r^2}
- Gravitational force F is directly proportional to the product of the two masses m_1 and m_2.
- So, in this framework, mass is the source of gravitational force.
- Here, 質量 (mass) is straightforward: it means gravitational mass (which measures how strongly something feels or produces gravity).
✅ So in Newtonian physics, it’s absolutely correct to say:
重力來自質量。
(Gravitational force comes from mass.)
🪐 2.
Einsteinian View
(General Relativity)
Einstein changed the game in 1915 with General Relativity:
“Mass (and energy, and pressure, and momentum…) curve spacetime, and gravity is the effect of that curvature.”
In Einstein’s famous field equations:
G_{\mu\nu} = \frac{8\pi G}{c^4} T_{\mu\nu}
- The left-hand side describes the curvature of spacetime.
- The right-hand side is the stress-energy tensor T_{\mu\nu}, which includes:
- Mass,
- Energy,
- Pressure,
- Momentum, etc.
So:
- Gravity is no longer thought of as a force per se, but as the result of how mass-energy tells spacetime how to curve, and how spacetime tells matter how to move.
✅ Thus, in general relativity, we should say:
Gravitational effects come from mass-energy, not just mass.
🧠 Summary:
|
Framework |
Source of Gravity |
Nature of Gravity |
|
Newtonian |
Mass (質量） |
A force between masses |
|
Einsteinian |
Mass + Energy + Pressure + Momentum |
Curvature of spacetime |
🧲 Analogy:
Just as:
- Electric charge is the source of the electromagnetic force,
- So too, mass-energy is the source of gravitational interaction.
But just as light (photons) is more than “just” charge in motion, gravity is more than “just” mass pulling on mass — it is geometry itself.
Would you like a poetic or visual metaphor for how spacetime bends around mass, à la the “trampoline” image — or something more precise like Einstein’s geodesics?
