The singulary at the start of the Universe.

[xelasnave]

At the start I read that we have a singularity.
This I gather is where GR may not be applicable

Is the start an object as a very small point or is it expected that there may be a certain size, say a golf ball .. Does GR give room for something larger than the term singularity suggests..at least to me.
Is there an anology one could apply that could communicate the models suggestion of reality to a lay person...
I tried thinking of an infinitely dense alka selsa tablet but if it's infinitely dense it will fizz forever...so my attempt does not work.
I suspect our observation only goes back as far as the background radiation

[Eratosthenes (Peter)]

Alex, although string theory is best described as a mathematical philosophy due to its lack of supporting experimental evidence, it has made some useful head way into tackling two problematical areas of gravity as described by Einstein's GR. Firstly the issue of highly curved space-time and secondly the infinities that emerge as gravity plunges into the world of the "very small scale".

Orbifold singularities are a specific case where String Theory works and GR fails. String theory does however fail when applied to Conifold singularities(although D-brane theory can handle Conifold singularities by imposing smooth changes on space-time. Again we are talking about Mathematical Philosophy here, rather than a discipline of Science, even though the motivations and implications are driven by Scientific goals).

Many of the infinities emerge because particles are usually modeled as points, whereas String Theory enables particles to be considered as extended strings. The scale becomes "blurred" in a sense, so the infinities vanish for units of length smaller than this "extended string" scales (probably not explaining this clearly - most likely because I dont understand it fully)

If I understand your OP correctly, I think you are more interested in the nature of Cosmological singularities - and I believe all our theories including string and D-brane theory fail here(welcome any input on this point)c

cheers

I am on Holidays as of today, so the holiday house will be getting some ventilation and hopefully my old reflector and refractor will have clear skies

[RB (Andrew)]

Some off topic posts deleted.
Please stay on topic.

RB

[xelasnave]

Thank you Peter.
Enjoy your holiday.

[g__day (Matthew)]

Ponder it this way maybe. At the start you have an absurdly high energy density come into existence before / marking the creation of space-time and its dimensions. The environment is perhaps mathematically modeled or under the "laws" (if they exist) of Quantum Gravity - General Relativity simply breaks down when the energies are so huge as to totally warp space-times topology. The Four force model we see all around us doesn't hold any sway at this creation moment.

Your modelling must really be all about topology - the newly formed curvature of the space-time field, far more I posit than newly arrived energy ball within it, is what defines what happens next. Things rapidly go Bada boom, but rather than envisage a decent boom in a large room, consider it is space-time itself being created and dimensionally unwrapping that is the dominant factor in the event; not the energy concentration spreading its thing around this newly formed space-time. The space-time field itself is spewing out and the laws of GR don't direct it very tightly.

By the time inflation ends, some 10 ^ -34 seconds after the existence event occurs, space-time may have inflated way faster than the speed of light in a vaccuum and the entire universe in this model is now maybe the size of a basketball with all the energy clumps in it are travelling apart by this "topology explosion" so fast that they are all casually disconnected from each other - as the force carriers that dominant our reality simply can't travel fast enough to compensate for that brief period when lightspeed wasn't the fastest thing around. These departing clumps of energy are cooling rapidly to the point where quantum gravity as the dominant environment controller is breaking down force at a time until you get to the four force model that rules most of the universe today (black holes and a few other exotics still excluded). Some models say our universe is one of these clumps.

During that first stint its really the medium - the topology of space-time itself - which is shaped by any matter or energy in it - that is the most important thing to analyse - rather than any specific things within in!