Astroquizzical: How Does Gravity Escape From A Black Hole?
“Information doesn’t always travel at the speed of light, though — depending on the environment that the information is traveling through, and the form of that information (which is not always light), the speed of information can proceed at speeds that are much slower than the speed of light. The speed of light in a vacuum seems to be a hard upper limit that nothing can surpass, but if your information is in the form of a compression wave, like sound, then the information travels at the speed of sound in that medium.”
There’s something puzzling about black holes, if you stop to consider it. On the one hand, they’re objects so massive and dense — compacted into such a small region of space — that nothing can escape from it, not even light. That’s the definition of a black hole, and why “black” is in the name. But gravity also moves at the speed of light, and yet the gravitational influence of a black hole has absolutely no problem extending not only beyond the event horizon, but infinite distances out into the abyss of space. Jillian Scudder has the answer to this puzzling conundrum!
Nearly a century ago, Edwin Hubble’s discovery of red-shifting of light from galaxies in all directions from our own suggested that space itself was getting bigger. Combined with insights from a handful of proposed non-Euclidean geometries, Hubble’s discovery implied that the cosmos exists in more than the three dimensions we’re familiar with in everyday life.That’s because parts of the cosmos were moving further apart, yet with no physical center, no origin point in three-dimensional space. Just think of an inflating balloon seen only from the perspective of its growing two-dimensional surface, and extrapolate to four-dimensional inflation perceived in the three-dimensional space that we can see. That perspective suggests that three-dimensional space could be curved, folded, or warped into a 4th dimension the way that the two dimensional surface of a balloon is warped into a 3rd dimension.We don’t see or feel more dimensions; nevertheless, theoretical physics predicts that they should exist.
There are three practical implications:
1. Warp Drive The main theory here is called M theory, which is a theory in physics that unites various types of what’s called superstring theory. In M theory there 10 or 11 dimensions. In addition to the three we’re familiar with there are compact dimensions. It’s all related to phenomena called branes that vibrate like strings, but what’s most relevant to this discussion is that the extra or compact dimensions don’t necessarily have to remain compact and it might be possible to unpack the extra dimensions. If an advanced civilization learns how to manipulate higher dimensions, they might use them for technology, including warp drive. The idea being that some kind of controlled decompacting of extra dimensions could have the effect of squeezing or expanding one of the three big dimensions that we know. Engage the compacting effect in front of a starship and the expansion effect to the rear, and you’d have warp drive. So far, we don’t have a shred of evidence that the hypothesized extra dimensions even exist. Someday, soon, we might get some evidence from the Large Hadron Collider.
3. Traversable Wormholes Another means of transport made possible by a multidimensional cosmos is wormholes. Theoretical physicist Kip Thorne worked out the equations showing that there was a stable, traversable wormhole, or even a system of such tunnels linking different areas of space-time. An advanced civilization could build a system of wormhole-dependent tunnels connecting different points of the space-time fabric, essentially drawing the departure and arrival points in the fabric into close proximity to one another through a 4th dimension. If we could do it, we could have an entry portal nearby, somewhere in the inner Solar System, that leads to an exit point at our destination, for instance a nearby star system with an Earth-like planet.
In honour of ASTEROID DAY, here’s our video with Bill Nye, asteroid education activist, that explains how we could go about stopping a threatening asteroid. Sign the petition to help potentially save the world at http://www.asteroidday.org/