Post by speakertoanimals on Sept 9, 2010 13:46:58 GMT 1
Are you sure?
Has the missing link been found - that between gravity and em?
How can we have momnetum without mass?
Has the gravitational effect of energy been measured?
Has the missing link been found - that between gravity and em?
How can we have momnetum without mass?
Has the gravitational effect of energy been measured?
This is actually totally trivial, in one sense. Relativity says that what we think of as mass is just another way to measure energy content. There is no magic conversion from mass to energy.
And what spacetime cares about is just energy and momentum, not whatever it is that has that energy and momentum.
momentum without mass -- photons, zero rest mass.
Momentum without energy, no.
As I said before, gravitational effect of photons too small to measure, only matters very early on in the universe when things were much livelier. We haven't measured gravitational effect directly, just as we can't measure the gravitational effect of a single atom -- just too small.
Yes, but surely only if they 'condense' into matter?
em waves creating gravity has not been observed unless that em energy is converted into matter and the search for a direct correlation between em and gravity is the Holy Grail of physics
em waves creating gravity has not been observed unless that em energy is converted into matter and the search for a direct correlation between em and gravity is the Holy Grail of physics
No to the first. no to the second as well, since we have never observed that much energy being 'converted' from photons into matter, and measured the gravitational effect of the resulting mass.
What HAS been observed is that the mass of a composite body (for which we DO have a direct observation of gravitational effects) depends on total energy content, and for hydrogen, some of that energy content depends on the exact em interaction between the electron and proton, which is why a hydrogen atom weighs LESS than the sum of the masses of an electron and a free proton.
Hence em contributes to mass, hence em contributes to gravity, even if we haven't been able to measure the gravitational effects of em alone.
I would suggest that the mathematical existence of em waves without a source is such a bucket, interesting but quite useless.
This is utter rubbish. When doing any problem in optics, you start with a lightwave coming of, of a defined frequency and direction. Exactly where that came from doesn't matter, hence the concept of an em wave alone is totally necessary, the source doesn't matter.
I think you don't understand either maths (if you think it is a tautology), OR physics, to be totally frank.............
Em wave aren't just another manifestation of matter. In particle physics terms we have matter particles (electrons, quarks), and force particles (photons, gluons, W and Z). There is a clear distinction (matter half-integer spin, force particles integer spin), which explains why they behave differently. You can't say one lot of a manifestation of the other, since without the latter, matter particles would not interact, hence stuff would be rather boring.
One way to create force particles is by banging matter particles together, but that doesn't make them a manifestation of matter. Just as the fact that you can create matter particles from photons doesn't make matter a manifestation of em energy either................
and the search for a direct correlation between em and gravity is the Holy Grail of physics
Where does em come from? It just is, although in quantum terms, related to the W and Z bosons of the weak force. I don't know why you seem to think em is so fundamental?