In the most active starburst region in the local universe lies a cluster of brilliant, massive stars, known to astronomers as Hodge 301. Hodge 301, seen in the lower right hand corner of this image, lives inside the Tarantula Nebula in our galactic neighbor, the Large Magellanic Cloud.
This star cluster is not the brightest, or youngest, or most populous star cluster in the Tarantula Nebula — that honor goes to the spectacular R136. In fact, Hodge 301 is almost 10 times older than the young cluster R136. But age has its advantages; many of the stars in Hodge 301 are so old that they have exploded as supernovae. These exploded stars are blasting material out into the surrounding region at speeds of almost 200 miles per second. This high speed ejecta are plowing into the surrounding Tarantula Nebula, shocking and compressing the gas into a multitude of sheets and filaments, seen in the upper left portion of the picture.
Feeding black holes develop a fractal skin as they grow. That’s the conclusion of simulations that take advantage of a correlation between fluid dynamics and gravity.
"We showed that when you throw stuff into a black hole, the surface of the black hole responds like a fluid – and in particular, it can become turbulent," says Allan Adams at the Massachusetts Institute of Technology. "More precisely, the horizon itself becomes a fractal."
Fractals are mathematical sets that show self-similar patterns: zoom in on one part of a fractal drawing, like the famous Mandelbrot set, and the smaller portion will look nearly the same as the original image. Objects with fractal geometries show up all over nature, from clouds to the coast of England.
Adams and his colleagues have now found evidence that fractal behaviour occurs in an unexpected place: on the surface of a feeding black hole. Black holes grow by devouring matter that falls into them; the black hole at the centre of our galaxy is due to feast on a gas cloud later this year. But the details of how feeding black holes grow, and how this might affect their host galaxies, are still unknown.
The standard theory is that the Universe grew from an infinitely dense point or singularity. The standard Big Bang model tells us that the Universe exploded out of an infinitely dense point, or singularity. But it is not known what triggered this outburst. Now, it is proposed that the Big Bang was mirage from collapsing higher-dimensional star.
In a paper posted last week, Afshordi (an astrophysicist at the Perimeter Institute for Theoretical Physics) and his colleagues turn their attention to a proposal made in 2000. In that model, our three-dimensional (3D) Universe is a membrane, or brane, that floats through a ‘bulk universe’ that has four spatial dimensions.
Ashfordi’s team realized that if the bulk universe contained its own four-dimensional (4D) stars, some of them could collapse, forming 4D black holes in the same way that massive stars in our Universe do: they explode as supernovae, violently ejecting their outer layers, while their inner layers collapse into a black hole. When Afshordi’s team modelled the death of a 4D star, they found that the ejected material would form a 3D brane surrounding that 3D event horizon, and slowly expand.
The event horizon of a black hole — the point of no return for anything that falls in — is a spherical surface. In a higher-dimensional universe, a black hole could have a three-dimensional event horizon, which could spawn a whole new universe as it forms.
It could be time to bid the Big Bang bye-bye. Cosmologists have speculated that the Universe formed from the debris ejected when a four-dimensional star collapsed into a black hole — a scenario that would help to explain why the cosmos seems to be so uniform in all directions.
The standard Big Bang model tells us that the Universe exploded out of an infinitely dense point, or singularity. But nobody knows what would have triggered this outburst: the known laws of physics cannot tell us what happened at that moment.
It is also difficult to explain how a violent Big Bang would have left behind a Universe that has an almost completely uniform temperature, because there does not seem to have been enough time since the birth of the cosmos for it to have reached temperature equilibrium.
To most cosmologists, the most plausible explanation for that uniformity is that, soon after the beginning of time, some unknown form of energy made the young Universe inflate at a rate that was faster than the speed of light. That way, a small patch with roughly uniform temperature would have stretched into the vast cosmos we see today. But the Big Bang was so chaotic, it’s not clear there would have been even a small homogenous patch for inflation to start working on.
String Theory predicts the existence of more than the 3 space dimensions and 1 time dimension we are all familiar with. According to string theory, there are additional dimensions that we are unfamiliar with because they are curled up into tiny complicated shapes that can only be seen on tiny scales. If we could shrink to this tiny, Planck-sized scale we could see that at every 3D point in space, we can also explore 6 additional dimensions. This animation shows a Calabi-Yau surface which is a projection of these higher dimensions into the more familiar dimensions we are aware of.
Brian Greene’s book, The Elegant Universe, was made into a documentary and has a chapter that does a good job of explaining this concept. The Elegant Universe [documentary]
Check out the 4-dimensional analogue of the dedocahedron, the hyper-dodecahedron or the 120-cell (or hecatonicosachoron). The image is a projection of this 4-dimensional object, visualised as a Schlegel diagram. The hyper-dodecahedron is composed of 120 dodecahedra, 720 pentagons, 600 vertices and 1200 edges. The thinner the line, the further it is away in 4 dimensions.
Most of us are accustomed to watching 2-D; even though characters on the screen appear to have depth and texture, the image is actually flat. But when we put on 3-D glasses, we see a world that has shape, a world that we could walk in. We can imagine existing in such a world because we live in one. The things in our daily life have height, width and length. But for someone who’s only known life in two dimensions, 3-D would be impossible to comprehend. And that, according to many researchers, is the reason we can’t see the fourth dimension, or any other dimension beyond that. Physicists work under the assumption that there are at least 10 dimensions, but the majority of us will never “see” them. Because we only know life in 3-D, our brains don’t understand how to look for anything more.
In 1884, Edwin A. Abbot published a novel that depicts the problem of seeing dimensions beyond your own. In “Flatland: A Romance of Many Dimensions" Abbot describes the life of a square in a two-dimensional world. Living in 2-D means that the square is surrounded by circles, triangles and rectangles, but all the square sees are other lines. One day, the square is visited by a sphere. On first glance, the sphere just looks like a circle to the square, and the square can’t comprehend what the sphere means when he explains 3-D objects. Eventually, the sphere takes the square to the 3-D world, and the square understands. He sees not just lines, but entire shapes that have depth. Emboldened, the square asks the sphere what exists beyond the 3-D world; the sphere is appalled. The sphere can’t comprehend a world beyond this, and in this way, stands in for the reader. Our brains aren’t trained to see anything other than our world, and it will likely take something from another dimension to make us understand.
But what is this other dimension? Mystics used to see it as a place where spirits lived, since they weren’t bound by our earthly rules. In his theory of special relativity, Einstein called the fourth dimension time, but noted that time is inseparable from space. Science fiction aficionados may recognize that union as space-time, and indeed, the idea of a space-time continuum has been popularized by science fiction writers for centuries. Einstein described gravity as a bend in space-time. Today, some physicists describe the fourth dimension as any space that’s perpendicular to a cube - the problem being that most of us can’t visualize something that is perpendicular to a cube.
Researchers have used Einstein’s ideas to determine whether we can travel through time. While we can move in any direction in our 3-D world, we can only move forward in time. Thus, traveling to the past has been deemed near-impossible, though some researchers still hold out hope for finding wormholes that connect to different sections of space-time.
If we can’t use the fourth dimension to time travel, and if we can’t even see the fourth dimension, then what’s the point of knowing about it? Understanding these higher dimensions is of importance to mathematicians and physicists because it helps them understand the world. String theory, for example, relies upon at least 10 dimensions to remain viable. For these researchers, the answers to complex problems in the 3-D world may be found in the next dimension - and beyond.
Here is a portrait of a man at eight years old, another at fifteen, another at seventeen, another at twenty-three, and so on. All these are evidently sections, as it were, Three-Dimensional representations of his Four-Dimensional being, which is a fixed and unalterable thing.