MASS EXPLAINED
You know that energy is an intangible thing. You can’t hold energy in the palm of your hand. Because energy is to do with stress, which is the same as pressure, which is the same as negative tension, and you need a volume of stress to get the dimensionality right.
You know that mass is a tangible thing. You can hold a thing in your hand and feel the mass of it. You even know that E=mc², and that the intangible thing called energy can be used to make the tangible thing called mass. But you don’t know how. I’ll explain how.
The answer is all down to motion. Or the lack of it. You have get relative, and think in terms of momentum and inertia. You have to stop thinking that momentum is something that a mass has, because a thing can have momentum without the thing you call mass. Like a photon. You know this because you’ve read the physics. You also know this because you’ve felt it yourself, down on the beach, playing in the surf. Along comes a massive wave. You know it’s a travelling stress and you think it has no mass because it’s the water that has the mass. But the wave does have momentum, enough to knock you and your girlfriend flat on your back, laughing and screaming with salt water up your nose. You can’t grab hold of it, but it can grab hold of you. And realising this is the first step in grasping how intangible energy can become tangible mass.
You can get a better feel for this with a gyroscope. Waggle it back and forth. See how light it feels. Now wind the string round the spindle, grasp it tight, and pull. You pulled tension out, so you put energy in. Your gyroscope is now humming, maybe precessing a little. When you try to waggle it you can feel the angular momentum working against you. And you’re beginning to get a feel for mass.
You know that energy is an intangible thing. You can’t hold energy in the palm of your hand. Because energy is to do with stress, which is the same as pressure, which is the same as negative tension, and you need a volume of stress to get the dimensionality right.
You know that mass is a tangible thing. You can hold a thing in your hand and feel the mass of it. You even know that E=mc², and that the intangible thing called energy can be used to make the tangible thing called mass. But you don’t know how. I’ll explain how.

The answer is all down to motion. Or the lack of it. You have get relative, and think in terms of momentum and inertia. You have to stop thinking that momentum is something that a mass has, because a thing can have momentum without the thing you call mass. Like a photon. You know this because you’ve read the physics. You also know this because you’ve felt it yourself, down on the beach, playing in the surf. Along comes a massive wave. You know it’s a travelling stress and you think it has no mass because it’s the water that has the mass. But the wave does have momentum, enough to knock you and your girlfriend flat on your back, laughing and screaming with salt water up your nose. You can’t grab hold of it, but it can grab hold of you. And realising this is the first step in grasping how intangible energy can become tangible mass.

You can get a better feel for this with a gyroscope. Waggle it back and forth. See how light it feels. Now wind the string round the spindle, grasp it tight, and pull. You pulled tension out, so you put energy in. Your gyroscope is now humming, maybe precessing a little. When you try to waggle it you can feel the angular momentum working against you. And you’re beginning to get a feel for mass.
