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RECENT POSTS IN THIS TOPIC

Edwin Pole II: on 4/15/17 at 1:32am UTC, wrote A few questions that are pertinent to another that I might post later. If...

Thomas Ray: on 4/14/17 at 13:01pm UTC, wrote Zeeya, I have read the first chapter (“God’s Billboard: the Cosmic...

Jonathan Dickau: on 4/14/17 at 5:18am UTC, wrote Part of the reason is this.. Yes there are extreme energy densities and...

Jonathan Dickau: on 4/14/17 at 4:43am UTC, wrote Not quick but fun Karl! It's really simple Karl! There are no definitive...

Karl Coryat: on 4/11/17 at 21:56pm UTC, wrote Thank you for this thread! One thing I've wondered is what precisely...

Thomas Ray: on 4/7/17 at 21:39pm UTC, wrote I will, Zeeya. This subject is a tough one, and I congratulate you for...

Steve Dufourny: on 4/7/17 at 19:46pm UTC, wrote :) but all is sciences Zeeya .All is Inside a science.Determinism...

Zeeya Merali: on 4/7/17 at 18:44pm UTC, wrote Thanks Tom! Be interested to know if you think the book makes the case for...



FQXi FORUM
December 11, 2017

CATEGORY: Cosmology [back]
TOPIC: Quickfire Cosmo Qs [refresh]
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FQXi Administrator Zeeya Merali wrote on Apr. 7, 2017 @ 12:52 GMT
This is a place where you can post quick queries about cosmology.

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Thomas Howard Ray wrote on Apr. 7, 2017 @ 15:56 GMT
Is cosmology a science? Why?

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Thomas Howard Ray wrote on Apr. 7, 2017 @ 16:58 GMT
P.S. -- ordered your book. :-)

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Steve Dufourny replied on Apr. 7, 2017 @ 18:39 GMT
Hi Tom :)

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FQXi Administrator Zeeya Merali replied on Apr. 7, 2017 @ 18:44 GMT
Thanks Tom! Be interested to know if you think the book makes the case for or against cosmology being a science. :)

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Steve Dufourny replied on Apr. 7, 2017 @ 19:46 GMT
:) but all is sciences Zeeya .All is Inside a science.Determinism determinism when it tells to rationalism that Copenaghen school is objective like all proportional causes and effects after all :) cosmology is a science...

best

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Karl H Coryat wrote on Apr. 11, 2017 @ 21:56 GMT
Thank you for this thread! One thing I've wondered is what precisely physicists mean when they talk about the first second after the big bang, or the first minute. Naïvely perhaps, it seems that these intervals would not be even remotely close to "Earth seconds," given that shortly after the big bang, the energy-density of the universe was immensely greater, with time dilated accordingly, from our perspective in a much lower-density region of spacetime. Sorry if this is not a quick query!

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Jonathan J. Dickau replied on Apr. 14, 2017 @ 04:43 GMT
Not quick but fun Karl!

It's really simple Karl! There are no definitive answers. I've thought about the primal instant and the first few moments for years now, and it's like the proverbial rabbit hole that just keeps getting deeper the farther down you go. I've heard folks like Gerard 't Hooft and Lee Smolin expound somewhat on in it in their lectures, and even talked with them afterward, but there is so much to learn! In short; the answer differs, depending on which scenario your working theory favors, in terms of the dimensionality of the universe and so on. Or there may have been more than one start, as with "Out of the white hole.." where our present-day cosmos arises from a black hole in an earlier 5-d universe.

Your query was actually one of my driving concerns, for the questions I asked of Tevian Dray at the end of GR21. Certain mathematical complications come into play, whenever we deal with the very smallest levels of scale, and to an even greater degree (or unavoidably) when we crank back the clock to the first instant. This makes non-commutative and then non-associative geometry dominant as we approach the limit. So the number of dimensions and degrees of freedom appear to be greater. But paradoxically; the folks in CDT and Quantum Einstein Gravity get good results (matching our cosmos) assuming that spacetime is initially 2-d evolving to 4-d smoothly, with fractal transitions.

More later,

Jonathan

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Jonathan J. Dickau replied on Apr. 14, 2017 @ 05:18 GMT
Part of the reason is this..

Yes there are extreme energy densities and gradients. Relativity becomes undefined where there are no structures existing independently, that can move relative to one another - because the universe is too small. Time, space, and energy, all flow away from the Planck-scale domain, because there is no effective angle of approach past the first instant. It is that way by definition. And the onset of inflation does create a time-dilation effect for observers wrt adjoining regions of spacetime - assuming inflation is the scenario you favor.

Andy Beckwith's essay touched on a possibility I like, that it's a minimum extent of time that gets things going - something from nothing. I talked about this with him, and I wrote something suggestive of it years ago, in my very first FQXi essay. But if time is primal; perhaps once there is a certain amount of it, space, energy, and matter, must emerge. This is precisely what Beckwith's result appears to indicate.

The era of geometrogenesis is somewhat a mystery to Physics. We know that it happened. What happens once particle production begins can be reverse-engineered to an extent, using the data about specific energies and transitions from particle accelerators and so on. The transition time for various energy binding processes, that create various sub-atomic particles, sets the time scale. And the half-life duration of particles sets other time base parameters at that juncture.

All the Best,

Jonathan

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Edwin James Pole II wrote on Apr. 15, 2017 @ 01:32 GMT
A few questions that are pertinent to another that I might post later.

If something falls into a black hole, at what speed does it cross the event horizon? I note that an outside observer sees time slow down for a falling object and never sees the object meet the event horizon.

If something falls into a black hole on a path not directly to the singularity, ie not perpendicular to the horizon, at what angle does it enter the event horizon (note max v in normal space is c.) Not perpendicular?

When two black holes merge, what paths do the two associated singularities take once the two event horizons meet?

If a massive object (one with mass) is accelerated to c, it's mass increases. Does this mass increase result in a higher gravitational attraction due to the object?

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