What's outside the universe? + New insight into how the universe works

[C C]

What’s Outside the Universe?
http://www.universetoday.com/128513/what...-universe/

EXCERPT: A few hundred episodes ago, I answered the question, “What is the Universe Expanding Into?” The gist of the answer is that the Universe as we understand it, isn’t really expanding into anything. If you go in any one direction long enough, you just return to your starting point. As the Universe expands, that journey takes longer, but there’s still nothing that it’s going into. Okay, so, I need to put an asterisk on that answer, and then when you read the fine print it’d say something like, “unless we live in a multiverse”....

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Merging black holes, gravitational waves provide new insight into how the universe works
https://www.sciencedaily.com/releases/20...182749.htm

RELEASE: On Sept. 14, waves of energy traveling for more than a billion years gently rattled space-time in the vicinity of Earth. The disturbance, produced by a pair of merging black holes, was captured by the Laser Interferometer Gravitational-Wave Observatory (LIGO) facilities in Hanford, Washington, and Livingston, Louisiana. This event marked the first-ever detection of gravitational waves and opens a new scientific window on how the universe works.

Less than half a second later, the Gamma-ray Burst Monitor (GBM) on NASA's Fermi Gamma-ray Space Telescope picked up a brief, weak burst of high-energy light consistent with the same part of the sky. Analysis of this burst suggests just a 0.2-percent chance of simply being random coincidence. Gamma-rays arising from a black hole merger would be a landmark finding because black holes are expected to merge "cleanly," without producing any sort of light.

"This is a tantalizing discovery with a low chance of being a false alarm, but before we can start rewriting the textbooks we'll need to see more bursts associated with gravitational waves from black hole mergers," said Valerie Connaughton, a GBM team member at the National Space, Science and Technology Center in Huntsville, Alabama, and lead author of a paper on the burst now under review by The Astrophysical Journal.

Detecting light from a gravitational wave source will enable a much deeper understanding of the event. Fermi's GBM sees the entire sky not blocked by Earth and is sensitive to X-rays and gamma rays with energies between 8,000 and 40 million electron volts (eV). For comparison, the energy of visible light ranges between about 2 and 3 eV.

With its wide energy range and large field of view, the GBM is the premier instrument for detecting light from short gamma-ray bursts (GRBs), which last less than two seconds. They are widely thought to occur when orbiting compact objects, like neutron stars and black holes, spiral inward and crash together. These same systems also are suspected to be prime producers of gravitational waves.

"With just one joint event, gamma rays and gravitational waves together will tell us exactly what causes a short GRB," said Lindy Blackburn, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and a member of the LIGO Scientific Collaboration. "There is an incredible synergy between the two observations, with gamma rays revealing details about the source's energetics and local environment and gravitational waves providing a unique probe of the dynamics leading up to the event." He will be discussing the burst and how Fermi and LIGO are working together in an invited talk at the American Physical Society meeting in Salt Lake City on Tuesday.

Currently, gravitational wave observatories possess relatively blurry vision. This will improve in time as more facilities begin operation, but for the September event, dubbed GW150914 after the date, LIGO scientists could only trace the source to an arc of sky spanning an area of about 600 square degrees, comparable to the angular area on Earth occupied by the United States.

"That's a pretty big haystack to search when your needle is a short GRB, which can be fast and faint, but that's what our instrument is designed to do," said Eric Burns, a GBM team member at the University of Alabama in Huntsville. "A GBM detection allows us to whittle down the LIGO area and substantially shrinks the haystack."

Less than half a second after LIGO detected gravitational waves, the GBM picked up a faint pulse of high-energy X-rays lasting only about a second. The burst effectively occurred beneath Fermi and at a high angle to the GBM detectors, a situation that limited their ability to establish a precise position. Fortunately, Earth blocked a large swath of the burst's likely location as seen by Fermi at the time, allowing scientists to further narrow down the burst's position.

The GBM team calculates less than a 0.2-percent chance random fluctuations would have occurred in such close proximity to the merger. Assuming the events are connected, the GBM localization and Fermi's view of Earth combine to reduce the LIGO search area by about two-thirds, to 200 square degrees. With a burst better placed for the GBM's detectors, or one bright enough to be seen by Fermi's Large Area Telescope, even greater improvements are possible.

The LIGO event was produced by the merger of two relatively large black holes, each about 30 times the mass of the sun. Binary systems with black holes this big were not expected to be common, and many questions remain about the nature and origin of the system.

Black hole mergers were not expected to emit significant X-ray or gamma-ray signals because orbiting gas is needed to generate light. Theorists expected any gas around binary black holes would have been swept up long before their final plunge. For this reason, some astronomers view the GBM burst as most likely a coincidence and unrelated to GW150914. Others have developed alternative scenarios where merging black holes could create observable gamma-ray emission. It will take further detections to clarify what really happens when black holes collide.

Albert Einstein predicted the existence of gravitational waves in his general theory of relativity a century ago, and scientists have been attempting to detect them for 50 years. Einstein pictured these waves as ripples in the fabric of space-time produced by massive, accelerating bodies, such as black holes orbiting each other. Scientists are interested in observing and characterizing these waves to learn more about the sources producing them and about gravity itself.

[stryder]

Re: What’s Outside the Universe?

In the video Fraser Cain within the first 20 seconds states:

"...Go in any one direction long enough,.. you just return to your starting point..."

This unfortunately isn't correct, which pretty much rings alarm bells and raises flags prior to anything else being said.

[C C]

Usually it's intended as a figurative way of expressing a biased opinion about the shape or state of the universe: Imaginatively as if someone could travel faster than the expansion of the universe, and as if these so-called "bubble universes" of inflation theory were really "round" rather than irregular (and as if perfect circles or non-mutable routes like that were really possible over cosmological distances). Also such a bias taking into account all the ways that the universe could illusionally seem to be infinite, flat, or open and yet not really be such.

Or Cain might truly be taking Pamela Gay's speech tropes too literally.

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(BB Concepts) Given the assumption that the matter in the universe is homogeneous and isotropic (The Cosmological Principle) it can be shown that the corresponding distortion of space-time (due to the gravitational effects of this matter) can only have one of three forms, as shown schematically in the picture at left. It can be "positively" curved like the surface of a ball and finite in extent; it can be "negatively" curved like a saddle and infinite in extent; or it can be "flat" and infinite in extent - our "ordinary" conception of space. A key limitation of the picture shown here is that we can only portray the curvature of a 2-dimensional plane of an actual 3-dimensional space! Note that in a closed universe you could start a journey off in one direction and, if allowed enough time, ultimately return to your starting point; in an infinite universe, you would never return. http://map.gsfc.nasa.gov/universe/bb_concepts.html



(Joseph Wang, Ph.D. Astrophysics) An open universe (i.e. one that expands forever) doesn't curve back in on itself so if you go in one direction you'll keep going. [...] Now a closed universe (one that has enough matter to collapse into itself) does curve back itself. However the interesting thing is that it turns out that the time it takes to go "around" the universe is exactly the lifetime of the universe. Put another way, if you go in one direction in a closed universe you will indeed end up back at the point you started, and you will reach that point at the time of the big crunch when everything else in the universe comes back to the same point. https://www.quora.com/If-I-travel-in-a-s...-I-started



Q: Is there such a thing as a straight line or a perfect circle in the entire Universe?
(Frank Heile, PhD in Physics from Stanford University) No. Perfect lines and circles are mathematical abstractions that cannot be implemented by any material objects in our universe. Mathematical lines and circles have zero width whereas atoms, electrons or photons all have some finite width. Electrons are thought to be point particles but they cannot be confined to a single point because of the Heisenberg uncertainty principle, so they must always be spread out over some region of space. Similarly for photons - photons are waves that always travel at speed "c" but when they interact with matter they act like point particles (i.e. the Photoelectric effect). Now, if you try to confine a photon (wave) to a very small region, the photon will diverge dramatically from that small, finite (but non-zero sized) region to form a very large region when the photon propagates away from that confining region at the speed of light. So photons cannot act as a mathematical point object to form even points along a line segment. A photon "beam", such as from a laser, always has a finite width and does eventually diverge with distance. https://www.quora.com/Is-there-such-a-th...e-Universe



(John Rennie) We don't think the universe is like a sphere because for that spacetime would have to have positive curvature, and experiments to date show space is flat (to within experimental error). However spacetime could be positively curved but with such small curvature that we can't detect it. Alternatively spacetime could be flat but have a complex global topology like a torus. The scale of anything like this would have to be larger than the observable univrse otherwise we'd have seen signs of it. http://physics.stackexchange.com/questio...r-infinite



(Cosmology 101) The three plausible cosmic geometries are consistent with many different topologies. For example, relativity would describe both a torus (a doughnutlike shape) and a plane with the same equations, even though the torus is finite and the plane is infinite. Determining the topology requires some physical understanding beyond relativity.

Like a hall of mirrors, the apparently endless universe might be deluding us. The cosmos could, in fact, be finite. The illusion of infinity would come about as light wrapped all the way around space, perhaps more than once--creating multiple images of each galaxy. A mirror box evokes a finite cosmos that looks endless. The box contains only three balls, yet the mirrors that line its walls produce an infinite number of images. Of course, in the real universe there is no boundary from which light can reflect. Instead a multiplicity of images could arise as light rays wrap around the universe over and over again. From the pattern of repeated images, one could deduce the universe's true size and shape.

Topology shows that a flat piece of spacetime can be folded into a torus when the edges touch. In a similar manner, a flat strip of paper can be twisted to form a Moebius Strip.

The 3D version of a moebius strip is a Klein Bottle, where spacetime is distorted so there is no inside or outside, only one surface.

The usual assumption is that the universe is, like a plane, "simply connected," which means there is only one direct path for light to travel from a source to an observer. A simply connected Euclidean or hyperbolic universe would indeed be infinite. But the universe might instead be "multiply connected," like a torus, in which case there are many different such paths. An observer would see multiple images of each galaxy and could easily misinterpret them as distinct galaxies in an endless space, much as a visitor to a mirrored room has the illusion of seeing a huge crowd.

One possible finite geometry is donutspace or more properly known as the Euclidean 2-torus, is a flat square whose opposite sides are connected. Anything crossing one edge reenters from the opposite edge (like a video game see 1 above). Although this surface cannot exist within our three-dimensional space, a distorted version can be built by taping together top and bottom (see 2 above) and scrunching the resulting cylinder into a ring (see 3 above). For observers in the pictured red galaxy, space seems infinite because their line of sight never ends (below). Light from the yellow galaxy can reach them along several different paths, so they see more than one image of it. A Euclidean 3-torus is built from a cube rather than a square. http://abyss.uoregon.edu/~js/lectures/cosmo_101.html



(Joseph Silk) Even if with our Cosmic Microwave Background data we can prove that the Universe is flat, we still won't know whether it's finite or infinite.

ESA: Then how are we going to know whether the Universe is infinite?

Joseph Silk: With great difficulty! We may never know it. If the Universe is finite, that means that in a two-dimensional geometry it would be like a torus. Now, think about a torus. In such a Universe, light travelling on the surface of a torus can take two paths: it can go around the sides but it can also go in a "straight line". This means that if the Universe is like a torus, light can have different ways to get to the same point. You can have a long way and a short way. And that would not be true on a plane. But a torus means that space is more complicated. It would mean that when you measure the CMB you will see strange patterns on the sky, because the light from far away would not have come to us in quite a "straight" line because of the topology of the Universe. So the hope would be, eventually, to look for those strange patterns on the sky. http://www.esa.int/Our_Activities/Space_...oseph_Silk