If you put a *really* heavy marble on a taut (but infinitely stretchy) rubber sheet, it will pull the sides of its depression down until, near the marble, the sides are vertical.

There’s no way you can flick another ball horizontally along the sheet in such a way that it would roll down the curve of the sheet, hit the heavy marble and bounce back out: anything you flick into that area of vertical walls will just never come out.

So obviously, there’s a certain distance from that hole where stuff you flick can come out (somewhat deflected by the curvature of the rubber sheet), and any closer, it won’t come back, and instead will fall down the hole. The “Event Horizon” of the vertically-walled “singularity”.

A concentration of gravity can’t suck in all the gravity. If gravity is just the curvature of spacetime, it seems obvious that a really large curvature in the rubber sheet can’t make the curvature of the rubber sheet become zero.

Except… what happens if the heavy marble is really infinitely heavy? The vertical walls get really long. Infinitely long. And the tube narrows even smaller than the marble. What happens if, then, where the tube’s size becomes zero, the rubber snaps? The marble is then in its own separate micro-universe, and the curvature of the sheet where it used to be connected, springs back to zero.

Can the fabric of spacetime snap? I dunno.

: D

The submillimeter telescope that I work on is here:
 http://aro.as.arizona.edu/smt_docs/smt_telescope_specs.htm

here’s a titanium physicists podcast about quazars
http://titaniumphysicists.brachiolopemedia.com/2012/04/30/episode-14-how-do-you-spell-quasar/

happy birthday

Compare *that* to your digital camera.

Digital cameras – the kind we point at each other here on Earth every day – don’t collect images, they collect information.  Photons pass through the lens, pass through a filter which separates the incoming light into red, blue, and green wavelengths, and the red, blue, or green light strikes pixels, generating an electrical impulse which is converted into digital value corresponding to how much light struck each pixel. 

With a radio telescope, photons at radio wavelengths strike an antenna, generating an electrical impulse, which is amplified and converted into a digital value corresponding to how much struck the antenna. 

So I guess what I’m saying is I’m curious as to what distinction you’re trying to make here.  Even film cameras don’t collect images, the collect information about what grains of silver halide crystals were struck by how much light, there’s no image there until you take the film and do a lot of stuff to it, just like there’s no image from a digital camera or radio telescope until you take the recorded data and do a lot of stuff to it. 

In response to the article, love the Niagara falls analogy.