Recent content by Paulibus

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    I 7 exoplanets around TRAPPIST-1

    The Trappist discovery has caught the attention of the world outside Physics Forums to an extent which could justify calling this discovery bizarre. How justified is such a label? Enough to mention a bizarre possibility? One which in another context would surprise few -- namely that maybe...
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    A Gravity as a non renormalizable theory

    Could you give an observed example of such a system? It is an example beyond the scope of any kind of physics.
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    A Where are the Higgs particles?

    I've been reading Jim Baggott's book "Higgs -- The Invention and Discovery of the 'God Particle' "and have a rather elementary question, easily answered, I'm sure, by folk that contribute to this forum: is the Higgs only associated with the inner machinations of other 'elementary' particles, or...
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    I Inflation and the false vacuum

    Fields are mathematical constructs, useful in physics, that assign scalar, vector, tensor quantities to each and every point in spacetime. The convention has developed in quantum physics of ending the names of the quanta of fields with "-on"; for example photon, electron and so also inflaton...
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    Hype about gravitational waves

    There seems to be considerable interest in the recent detection of gravitational waves. For the physics community this interest is fully justified. But in the popular press it seems to me to be reaching unjustified and perhaps harmful levels. When one reads overblown hype like: " A giant...
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    Is String Theory Testable?

    Quantum Field Theory agrees with observation to an extent not quantitatively matched by any other human mental construct. Doesn't this answer your question in the affirmative, Haushofer?
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    POLL: How do you think of the Hubble rate?

    Thanks especially for post #5. And Schiller was a contemporary of one of my great-something grandfathers, Lessing; so I prefer to think of cosmic expansion like matter in rising dough, rather than quantitatively, and vote #6.
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    Equivalence of inertial and gravitational mass

    Thanks for your reply #15, ohwilleke. You wrote : "The difference between mass and mass-energy, however, is not just semantics. It is a fundamental concept that you need to understand the question you are asking in the first place in a way that has a meaningful answer." Yes, mass is an...
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    Equivalence of inertial and gravitational mass

    Thanks, Haushofer. It's time that we got away from semantics. I would still like to know whether the photons that comprise a beam of radiation attract one another, or not, and to have the reasons for the reply, whatever it is, spelled out.
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    Equivalence of inertial and gravitational mass

    I seem to have worded my question in an irritating way. But I take issue with the statement in post #6 that photons don't have 'gravitational' mass. They don't have 'rest' mass, but they do gravitate: their geodesic trajectories through spacetime are indeed affected by matter concentrations...
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    Equivalence of inertial and gravitational mass

    Still puzzling. Consider photons -- entities without rest mass that are nevertheless endowed with energy E = just because they wobble in time. And energy is mass, given by m = E/c^2. I guess this mass should be labelled 'gravitational' because photons gravitate and light is known to be...
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    Equivalence of inertial and gravitational mass

    Is there any credible hard evidence that this equivalence extends to all moving bodies? We accept on good grounds that the apparent mass of moving objects is enhanced by motion, to a measurable degree that increases indefinitely as observed speeds of relative motion approach c. Likewise...
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    Why is the Universe (nearly) flat?

    strikes me as something not answerable by Physics, which doesn't answer "why" questions --it tells only "how" stuff came to be; here via the agency of a scalar inflaton field. But I'd like to know whether such a field is a logically inevitable ingredient of any extensive universe's initial...
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    Smolin: Extending dualities to trialities (deepens dynamics)

    Please, somebody, translate for me what seems to me to be an illiterate phrase in an interesting article.