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Posts Tagged ‘Dark Matter

“I’m sure the universe is full of intelligent life. It’s just been too intelligent to come here.”*…

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A new computer simulation shows that a technologically advanced civilization, even when using slow ships, can still colonize an entire galaxy in a modest amount of time. The finding presents a possible model for interstellar migration and a sharpened sense of where we might find alien intelligence.

Space, we are told time and time again, is huge, and that’s why we have yet to see signs of extraterrestrial intelligence. For sure, the distances between stars are vast, but it’s important to remember that the universe is also very, very old. In fact, I’d go so far as to say that, in terms of extremes, the Milky Way galaxy is more ancient than it is huge, if that makes sense. It’s for this reason that I tend to dismiss distances as a significant variable when discussing the Fermi Paradox—the observation that we have yet to see any evidence for the existence of alien intelligence, even though we probably should have.

New research published in The American Astronomical Society is bolstering my conviction. The new paper, co-authored by Jason Wright, an astronomer and astrophysicist at Penn State, and Caleb Scharf, an astrobiologist at Columbia University, shows that even the most conservative estimates of civilizational expansion can still result in a galactic empire.

A simulation produced by the team shows the process at work, as a lone technological civilization, living in a hypothetical Milky Way-like galaxy, begins the process of galactic expansion… Things start off slow in the simulation, but the civilization’s rate of spread really picks up once the power of exponential growth kicks in. But that’s only part of the story; the expansion rate is heavily influenced by the increased density of stars near the galactic center and a patient policy, in which the settlers wait for the stars to come to them, a result of the galaxy spinning on its axis.

The whole process, in which the entire inner galaxy is settled, takes one billion years. That sounds like a long time, but it’s only somewhere between 7% and 9% the total age of the Milky Way galaxy.

As noted, the new model is constrained by some very conservative rules. Migration ships are launched once every 10,000 years, and no civilization can last longer than 100 million years. Ships can travel no farther than 10 light-years and at speeds no faster than 6.2 miles per second (10 kilometers per second), which is comparable to human probes like the Voyager and New Horizons spacecraft. 

“This means we’re not talking about a rapidly or aggressively expanding species, and there’s no warp drive or anything,” said Wright. “There’s just ships that do things we could actually manage to do with something like technology we can design today… Even under these conditions, the entire inner part of the simulated galaxy became settled in a billion years. But as Wright reminded me, our “galaxy is over 10 billion years old, so it could have happened many times over, even with those parameters.”…

A new simulation published by the American Astronomical Society suggests that aliens wouldn’t need warp drives to take over an entire galaxy in (relatively) short order, as George Dvorsky (@dvorsky) explains.

[Image above: Andromeda Galaxy, source]

* Arthur C. Clarke

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As we spread out, we might spare a thought for Jacobus Cornelius Kapteyn; he died on this date in 1922. An astronomer, he used photography and statistical methods to determine the motions and spatial distribution of stars (especially with the Milky Way), the first major step after the works of William and John Herschel. He introduced absolute magnitude and color indexing as standard concepts in cataloguing stars.

Kapteyn was also among the first to suggest the existence of dark matter (which he deduced from examining stellar velocities).

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“Everything we know and love about the universe and all the laws of physics as they apply, apply to four percent of the universe”*…

 

dark matter

 

In 1969, the American astronomer Vera Rubin puzzled over her observations of the sprawling Andromeda Galaxy, the Milky Way’s biggest neighbour. As she mapped out the rotating spiral arms of stars through spectra carefully measured at the Kitt Peak National Observatory and the Lowell Observatory, both in Arizona, she noticed something strange: the stars in the galaxy’s outskirts seemed to be orbiting far too fast. So fast that she’d expect them to escape Andromeda and fling out into the heavens beyond. Yet the whirling stars stayed in place.

Rubin’s research, which she expanded to dozens of other spiral galaxies, led to a dramatic dilemma: either there was much more matter out there, dark and hidden from sight but holding the galaxies together with its gravitational pull, or gravity somehow works very differently on the vast scale of a galaxy than scientists previously thought.

Her influential discovery never earned Rubin a Nobel Prize, but scientists began looking for signs of dark matter everywhere, around stars and gas clouds and among the largest structures in the galaxies in the Universe. By the 1970s, the astrophysicist Simon White at the University of Cambridge argued that he could explain the conglomerations of galaxies with a model in which most of the Universe’s matter is dark, far outnumbering all the atoms in all the stars in the sky. In the following decade, White and others built on that research by simulating the dynamics of hypothetical dark matter particles on the not-so-userfriendly computers of the day.

But despite those advances, over the past half century, no one has ever directly detected a single particle of dark matter. Over and over again, dark matter has resisted being pinned down, like a fleeting shadow in the woods. Every time physicists have searched for dark matter particles with powerful and sensitive experiments in abandoned mines and in Antarctica, and whenever they’ve tried to produce them in particle accelerators, they’ve come back empty-handed. For a while, physicists hoped to find a theoretical type of matter called weakly interacting massive particles (WIMPs), but searches for them have repeatedly turned up nothing…

Dark matter is the most ubiquitous thing physicists have never found. Is it time to consider alternative explanations? “Does dark matter exist?

[image above: source]

* Neil deGrasse Tyson

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As we interrogate the invisible, we might recall that it was on this date in 1944 that one of the worst fire disasters in U.S. history occurred; the blaze broke out during an afternoon performance of the Ringling Bros. and Barnum & Bailey Circus that was attended by an estimated 7,000 people.  It killed 167 people; more than 700 were injured.

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Because of the paraffin wax waterproofing of the tent, the flames spread rapidly

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Emmett Kelly holding a water bucket on what became known as “the day the clowns cried

 

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July 6, 2020 at 1:01 am

“Oh, there you are Peter”*…

 

The missing links between galaxies have finally been found. This is the first detection of the roughly half of the normal matter in our universe – protons, neutrons and electrons – unaccounted for by previous observations of stars, galaxies and other bright objects in space.

You have probably heard about the hunt for dark matter, a mysterious substance thought to permeate the universe, the effects of which we can see through its gravitational pull. But our models of the universe also say there should be about twice as much ordinary matter out there, compared with what we have observed so far.

Two separate teams found the missing matter – made of particles called baryons rather than dark matter – linking galaxies together through filaments of hot, diffuse gas

Get galactic at: “Half the universe’s missing matter has just been finally found.”

* meme

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As we heed E.M. Forster, we might recall that it was on this date in 1843 that Sir William Rowan Hamilton conceived the theory of quaternions.  A physicist, astronomer, and mathematician who made important contributions to classical mechanics, optics, and algebra, he had been working since the late 1830s on the basic principles of algebra, resulting in a theory of conjugate functions, or algebraic couples, in which complex numbers are expressed as ordered pairs of real numbers.  But he hadn’t succeeded in developing a theory of triplets that could be applied to three-dimensional geometric problems.  Walking with his wife along the Royal Canal in Dublin, Hamilton realized that the theory should involve quadruplets, not triplets– at which point he stopped to carve carve the underlying equations in a nearby bridge lest he forget them.

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October 16, 2017 at 1:01 am

“The missing link in cosmology is the nature of dark matter and dark energy”*…

 

Familiar visible matter can be thought of as the privileged percent—actually more like 15 percent—of matter. In business and politics, the interacting 1 percent dominates decision making and policy, while the remaining 99 percent of the population provides less widely acknowledged infrastructure and support—maintaining buildings, keeping cities operational, and getting food to people’s tables. Similarly, ordinary matter dominates almost everything we notice, whereas dark matter, in its abundance and ubiquity, helped create clusters and galaxies and facilitated star formation, but has only limited influence on our immediate surroundings today…

The common assumption is that dark matter is the “glue” that holds together galaxies and galaxy clusters, but resides only in amorphous clouds around them. But what if this assumption isn’t true and it is only our prejudice—and ignorance, which is after all the root of most prejudice—that led us down this potentially misleading path?…

Indeed,  Harvard theoretical physicist and cosmologist Lisa Randall asks, “Does dark matter harbor life?

* Stephen Hawking

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As we reach reflexively for a flashlight, we might send particular birthday greetings to Abraham Pais; he was born on this date in 1918.  After earning his Ph.D. in physics in Holland five days before a Nazi deadline banning Jews from receiving degrees, he went into hiding– and worked out ideas in quantum electrodynamics (later shared with Niels Bohr) that became the building blocks of the theory of elemental particles.  He was later a colleague of Robert Oppenheimer and Albert Einstein at the Institute for Advanced Studies at Princeton.

Pais was also an widely-respected historian of science.  Among his many works were a biography of Bohr and (the work for which he’s best remembered as a historian) Subtle Is the Lord: The Science and Life of Albert Einstein, which is considered the definitive Einstein biography.

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May 19, 2017 at 1:01 am

“When the going gets weird, the weird turn pro”*…

 

An international study claims to have found first observed evidence that our universe is a hologram.

What is the holographic universe idea? It’s not exactly that we are living in some kind of Star Trekky computer simulation. Rather the idea, first proposed in the 1990s by Leonard Susskind and Gerard ‘t Hooft, says that all the information in our 3-dimensional reality may actually be included in the 2-dimensional surface of its boundaries. It’s like watching a 3D show on a 2D television…

Just when one thought that things couldn’t get any stranger: “Scientists Find First Observed Evidence That Our Universe May Be a Hologram.”

Pair with this piece on recent experimental confirmation of what Albert Einstein called “spooky action at a distance.”

* Hunter S. Thompson

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As we batten down the hatches, we might send shady birthday greetings to Fritz Zwicky; he was born on this date in 1898.  A distinguished astronomer who worked at Cal Tech most of his life, Zwicky is best remembered for being the first to infer the existence of “dark matter“: while examining the Coma galaxy cluster in 1933, he used the virial theorem to deduce the existence of what he then called dunkle Materie. Colleagues knew him as both both a genius and a curmudgeon. One of his favorite insults was to refer to people of whom he didn’t approve as “spherical bastards”– because, he explained, they were bastards no matter which way you looked at them.

[For more on dunkle Materie:Will We Ever Know What Dark Matter Is?“]

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Written by (Roughly) Daily

February 14, 2017 at 1:01 am

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