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Comment by danschumann | Hacker News Reader

To really be able to manipulate gravity, you would also need to manipulate mass, and so far nuclear is the only way I know of, in which we do that, but uhh.. I don't think we'll get anti gravity until we can control mini stars... Little nuclear engines.

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It is a common myth that nuclear reactions "turn mass into energy". What actually happens is that the products of the reaction have less binding energy than the initial nucleus. Since energy gravitates, this reduces the mass of the products. The exact same thing happens in chemical reactions. If you burn something, the product are lighter than the initial substances by the mass equivalent of the energy released.

"...energy gravitates, this reduces the mass of the products." "...the product are lighter than the initial substances by the mass equivalent of the energy released."

How are these not restating "turn mass into energy"?

Both scenarios approximate: High Mass => Low Mass + Energy

https://youtu.be/Xo232kyTsO0 check out this PBS spacetime explanation for what it means for energy to have mass. It's impossible to convert energy into mass, adding up all the mass inside a composite does not equal the true mass, because energy itself has mass. When we split an atom, we are releasing some of that extra (energy) that was stored as potential energy holding the parts together, not converting energy into matter, just moving states of energy to other types.

I change the location of my gravitational field every time I move my body. I modify my gravitational field with every breath as I breath out heavier gases and breath in lighter gases.

The thing about gravitational energy is that it's the weakest of all fundamental forces. Nuclear energy is more about releasing the energy stored in the Strong/Weak Nuclear Interaction than it is about gravity.

Gravity is a property of energy, of which mass is one form. That means a laser beam attracts other energy via gravity.

What if gravity isn't always relative to mass? I mean, all of our scientific evidence suggests it is... but I suppose it's possible that's not quite right.

Actually we know that gravity in fact not due to mass. Mass is just one component of what actually interacts with gravity.

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