On Thu, Feb 4, 2021 at 9:13 PM Alan Grayson <[email protected]> wrote:
>>In relativity mass and energy are the same thing, remember E=MC^2, so the >> kinetic energy needed to do work comes from the mass/energy released by >> vacuum potential energy falling outward. In a similar way a hydroelectric >> dam produces electrical energy that can do work from the potential energy >> released by water falling inward. >> > > *> But rest energy is positive whereas potential energy is negative. How > do you expect negative potential energy to transform into positive rest > energy? AG* > You've asked that exact same question before and I've answered it before, it does it the same way a hydroelectric dam transfers negative potential energy into positive energy that can do work; in the case of normal matter like water that's done by falling inward, in the case of vacuum energy that's done by falling outward. *>>> Is this the GR expression for PE, which you earlier stated is >>> different from Newtonian physics? * >>> >> >> >> No. The formula for gravitational potential energy is the same in >> both Newtons and Einstein's theory. >> > > *> I could swear you posted the opposite recently. When I have the > motivation, I'll try to find it. AG * > The formula for gravitational potential energy is the same in both theories, although Newton didn't know about E=MC^2 or vacuum energy so the calculations sometimes differed, sometimes only slightly sometimes by a lot. For example Newton would've said that 2 hot iron cannonballs placed one foot apart and 2 cold cannonballs at the same distance would have exactly the same gravitational potential energy, but Einstein would say they would not because the hot iron cannonballs had more energy and thus have more mass than the cold iron cannonballs. >> If vacuum energy really does exist then It's an intrinsic property of >> space itself and so it doesn't move, it always stays the same, so I >> guess you could call that rest mass if you want but I don't know why >> you'd want to. Light moves as fast as things can go and has zero rest mass, >> but even a photon of light has a gravitational field, in fact if you >> concentrated light enough into a small enough volume it would turn into a >> Black Hole. Such a ball of light is called a "Kugelblitz". >> > > *> Didn't you assume your sphere has some initial mass in the form of > "sand"? * > I gave two examples, the first was a sphere made of normal matter like sand, as the radius R of the sphere got larger the mass stayed the same, so according to the formula for gravitational potential energy PE= (-G*M^2)/R becomes less negative and more positive, and that means it's uphill and so would need work to accomplish. In my second example I considered an expanding sphere of vacuum energy, in that case M does not stay the same but increases to the cube of R, So by using the same formula that means it would be downhill and can produce work. > > *> Or is it now light?* > As I said Newton didn't know about E=MC^2 so he would've said light wouldn't produce a gravitational field no matter how intense it became, Einstein would say something different. The gravitational field produced by an expanding ball of light would behave differently than either a ball of sand particles or a ball of vacuum energy because as R got larger the number of photons in this sphere would remain the same but each individual photon would get stretched, it would get red shifted to a longer wavelength and longer wavelength photons have less energy, so as R increases the mass M would not stay the same as a sphere of sand of would or get larger as a ball of vacuum would but the mass would actually get smaller. > > *Doesn't really matter, except you have to account for positive rest > and kinetic energies equating to negative potential energy, * > The engineers who design hydroelectric dams seem to have no difficulty accounting for that, and neither do I. John K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis> -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAJPayv3y4DzyUBG0g5J6DSd4ztGy%2B4PaBR1zsmXjUdTZ6oWFkw%40mail.gmail.com.
