Time, causality, and prime movers

What's beyond the sky used to be a reasonable question.Sometimes we ask the wrong questions, and answer them with bad answers. One particularly bad question is: “what was there before the Big-Bang?” There are many others, but this one requires a little mental gymnastics in order to get used to modern ideas of time and understand what the consequences are.


More fundie fun

snakeThere is an article on stupid Conservapædia (that I won't grace with a link) that rants about the theory of Relativity because apparently it contradicts the Bible. Well, what doesn't? Even the Bible contradicts the Bible...
Anyways, here is how that fantastic piece of entertainment begins:

"The theory of relativity is a mathematical system that allows no exceptions."


Wild non-scientific musings: extra dimensions and parallel universes

fig. 8Amy was asking me some questions on "alternate dimensions" and "parallel universes". Here's my answer, which is entirely non-scientific although it is based on a few things I know (or think I know) about physics. I'm suspecting for example that the string theory stuff is a little shaky as I never really studied the math in there.


Black hole evaporation paradox?

I just sent this letter to Scientific American. I'd be interested to have any informed opinion on the matter.

I’ve read the article about black hole computers with great interest, but there are still a few questions that I think remain unanswered.

The article makes it quite clear how black holes could be memory devices with unique properties, but I didn’t quite understand what kind of logical operations they could perform on the data.

But another, more fundamental question is bugging me ever since I read the article. From what I remember learning about black holes, if you are an observer outside the black hole, you will see objects falling into the black hole in asymptotically slow motion. The light coming from them will have to overcome a greater and greater gravitational potential as the object approaches the horizon, losing energy along the way and shifting to the red end of the spectrum. From our vantage point, it seems like the object does not reach the horizon in a finite time.

From a frame that moves with the object, though, it takes finite time to cross the horizon.

This is all very well and consistent so far. Enter black hole evaporation.

From our external vantage point, a sufficiently small black hole would evaporate over a finite period of time. So how do we reconcile this with the perception that objects never actually enter the horizon?