Re: Questions (Space)

Gerry Quinn <gerryq@xxxxxxxxx> wrote:

In article <1i4nzsa.1v4hneh15ubd3dN%spam@xxxxxxxxxxxxxxxxxxxx>,
spam@xxxxxxxxxxxxxxxxxxxx says...
Gerry Quinn <gerryq@xxxxxxxxx> wrote:

That's true. It's also irrelevant, unlike my observation, because no
current physics models depend on angels. On the other hand, models
based on particle interactions in flat spacetime work well for all the
other forces, and there seems no reason why they cannot be made work
for gravity.

<surprised> Is that true?? </surprised>

I'm not sure where you get that statement from. AIUI, gauge theories are
complicated (perhaps that should be AI-dont-UI).

All quantum theories of forces are based on a background spacetime,
normally flat. You can build a theory of electromagnetism based om
photons, and you can build a theory of gravitation based on gravitons.

This is merely a repetition of your previous assertion.

AIUI, to calculate the energy leves of a hydrogen atom, relativistic
corrections have to be taken into account.

It's easy enough to construct approximate theories.

Does QED work in flat space time, or is it necessary to make
relativistic corrections? Or is it so different the question doesn't
make sense?

There are certain difficulties unique to gravity, but AFAIK the main
problems are not that they cannot be solved, but that they cannot be
solved elegantly. And that is only because we do not have much
knowledge about physics at an extremely high energy. There's no
conceptual difficulty about treating gravity as an effective field
theory.

My main puzzlement here, though, is why you are so attached to flat
spacetime. I don't see any real reason for it.

Given two theories, I infer that you would prefer one with flat
spacetime over one with some other geometry. But you haven't said why.

As I said in the previous post, it's the simplest possible geometry.

And, as I say in another post (today), no it isn't.

Why do you think it's the simplest?

And even if it were (which I dispute) why would that make it true?

Of course some theorists hope to explain geometry. I would prefer to
explain gravity first, amd then look at explaining geometry. After
all, why should just one of the forces be the cause of geometry?

Well, as I say (also in the other post), I'd rather explain forces by
geometry. Forces as "things in themself" don't make sense.

There are two things here: QM and GR. I can accept the exchange of
virtual particles as a QM explanation of forces (no spooky action at a
distance). I can accept a GR kind of geometrical explanation of forces
(no spooky action at a distance).

I can't accept forces as the primitive concept (too much spooky action
at a distance).

My problem (and everyone else's) is that no one has (yet) unified QM and
GR and the two explanations are incompatible. Some kind of quantum
gravity might do it, but it *must* include all the geometrical
predictions of GR or it won't fly.

That ought to be repeated in flashing neon letters 10 metres high:
***The two best physical theories of the 20th century, QM and GR, have
both proved their usefulness, and made countless successful
predictions. Both seem to be correct. Yet they are profoundly
contradictory. They can *not* both be correct.

I, personally, would prefer a geometrical explanation of QM.
Unfortunately, I don't understand the kinds of theories that might work,
and I don't think many people are working on those kinds of theories
anyway.

Jonathan
(The boyfriend of the daughter of the partner of a friend of mine is a
string-theorist. But apparently he refuses to talk about string theory
to laymen. Probably with good reason <g>.)

--
"There's many a best seller that could have been prevented
by a good teacher." Flannery O'Connor
.

Relevant Pages

  • Re: the basis of relativity
    ... > With regard to the theory of gravity as I described it. ... > one should say gravity is indistinguishable from geometry. ... spacetime being an imaginary frame for solving physics problems, ...
    (sci.physics.relativity)
  • Re: GR ?
    ... Mass distorts spacetime, causing it to curve. ... Gravity ... |> | is described by Euclidean or plane geometry. ...
    (sci.physics.relativity)
  • Re: Questions (Space)
    ... can be successfully modeled on a basis of Euclidean spacetime. ... AIUI, gauge theories are ... conceptual difficulty about treating gravity as an effective field ... My main puzzlement here, though, is why you are so attached to flat ...
    (rec.arts.sf.composition)
  • Re: Questions (Space)
    ... mathematically equivalent model in which spacetime is flat. ... One of the appeals of GR is that it doesn't treat gravity as a ... Electromagnetism isn't spooky: it works by the exchange of virtual ... You appear to have a preferred geometry + ...
    (rec.arts.sf.composition)
  • Re: Questions (Space)
    ... All quantum theories of forces are based on a background spacetime, ... normally flat. ... conceptual difficulty about treating gravity as an effective field ... As I said in the previous post, it's the simplest possible geometry. ...
    (rec.arts.sf.composition)
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