一个质子由三个带电的夸克通过强相互作用力结合而形成，它的半径是由电荷密度降到某一确定值的距离来确定的。
A proton contains three charged quarks bound by the strong force and its radius is defined as the distance at which the charge density drops below a certain value.
对于任何一个物体，都存在一个被称为史瓦西半径的临界半径，在这个半径以内的质量将形成一个黑洞。
For any object, there is a critical radius, called the Schwarzschild radius, at which its mass will form a black hole.
这是很容易形成正确的半径，钉焊接两端。
This is easily formed to the correct radii, tack weld both ends.
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