circular cause

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Permalink Reply by Humble Pie on January 12, 2013 at 9:53am

This reminds me a little of my favorite response to the cosmological argument:

Everything that exists has a beginning.

God has no beginning.

Therefore, God does not exist.

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Permalink Reply by Luara on January 12, 2013 at 10:08am

Everything that exists has a beginning.

You or anyone would have a hard time proving that I think! 

How about space and time, how about the laws of physics?  Did they have a beginning? 

I read a SF story once about some plans for a time machine that appeared mysteriously.  So a time machine was made.  Then someone traveled to a time before the time machine was made, and left the plans for the time machine in the past ...

Spacetimes with timelike loops, where you can travel around the loop, always in the direction of increasing time, are often ruled out because of this kind of problem. 

But cause might come from outside of spacetime somehow. 

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Permalink Reply by Humble Pie on January 12, 2013 at 5:11pm

Of course.  It's an absolutely ridiculous premise.  But it's the same first premise that the cosmological argument uses.  We all know that the cosmological argument is bunk.  But if it weren't,  this wouldn't be either.  It's sort of a way to show a theist how silly that particular argument really is.

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Permalink Reply by Luara on January 12, 2013 at 7:37pm

Yes, when someone like William Lane Craig talks about cosmology, any physics gremlins* around will be facepalming in a big way. 

There are spacetimes that are solutions to Einstein's equations, that have closed timelike curves.  Such as the Goedel solution, which describes a rotating universe.  The events on a closed timelike curve evolve according to the laws of physics, but when you travel around the loop, you have to end up in the same state as when you started!

The physicist Ronald Mallett found that a closed timelike curve could be generated by a helical light beam - if the light had enough mass, I guess. 

Closed timelike curves seem to be generated by rotation, but it has to be very drastic.  

*physics gremlin:  impish personification of the laws of physics.  Only visible late at night. 

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Permalink Reply by Humble Pie on January 13, 2013 at 11:02am

*physics gremlin:  What happens if you feed astronomy grad students after midnight.

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