CWL

Galaxy Collisions: Simulation vs Observations

The folks over at NASA apod just put up an awesome galaxy collisions, simulations and observations video for the public. I made a little gif set to go along with the video which can be found here.

What happens when two galaxies collide? Although it may take over a billion years, such titanic clashes are quite common.

Images Credit: NASA, ESA; Visualization: Frank Summers (STScI);

Simulation: Chris Mihos (CWRU) & Lars Hernquist (Harvard).

Since galaxies are mostly empty space, no internal stars are likely to themselves collide. Rather the gravitation of each galaxy will distort or destroy the other galaxy, and the galaxies may eventually merge to form a single larger galaxy.

Expansive das and dust clouds collide and trigger waves of star formation that complete even during the interaction process. Pictured above is a computer simulation of two large spiral galaxies colliding, interspersed with real still images taken by the Hubble Space Telescope.

Our own Milky Way Galaxy has absorbed several smaller galaxies during its existence and is even projected to merge with the larger neighboring Andromeda galaxy in a few billion years.

A Spacetime Magnifying Glass

This Hubble image shows the galaxy cluster Abell S1077. Galaxy clusters are large groupings of galaxies, each of them including millions of stars. They are the largest existing structures in the Universe to be held together by their gravity.

The amount of matter condensed in such groupings is so high that their gravity is enough to warp the fabric of spacetime, distorting the path that light takes when it travels through the cluster. In some cases, this phenomenon produces an effect somewhat like a magnifying lens, allowing us to see objects that are aligned behind the cluster and which would otherwise be undetectable from Earth. In this image, you see stretched stripes that look like scratches on a lens but are, in fact, galaxies whose light is heavily distorted by the gravitational field of the cluster.

Astronomers use tools like the NASA/ESA Hubble Space Telescope and the effects of gravitational lensing to peer far back in time and space to see the furthest objects located in the early Universe. One of the record holders is MACS0647-JD, a galaxy seen by Hubble (heic1217) and the Spitzer Space Telescope with the help of a gravitational lens much like this one in the galaxy cluster MACS J0647.7+7015. Its light has taken 13.3 billion years to reach us.

This image is based in part on data spotted by Nick Rose in the Hubble’s Hidden Treasures image processing competition.

8 Baffling Astronomy Mysteries

We’ve seen a lot of information explaining the wonders of astronomy and space, but what of the mysteries? The realm scientists have yet to fully understand. SPACE has this awesome article getting into a few, 8 in total, of those very areas in the study of the stars that continue to baffle scientists:

The universe has been around for roughly 13.7 billion years, but it still holds many mysteries that continue to perplex astronomers to this day. Ranging from dark energy to cosmic rays to the uniqueness of our own solar system, there is no shortage of cosmic oddities.

The journal Science summarized some of the most bewildering questions being asked by leading astronomers today. In no particular order, here are eight of the most enduring mysteries in astronomy:

8 What is Dark Energy?

Dark energy is thought to be the enigmatic force that is pulling the cosmos apart at ever-increasing speeds, and is used by astronomers to explain the universe’s accelerated expansion.

This elusive force has yet to be directly detected, but dark energy is thought to make up roughly 73 percent of the universe.

7 How Hot is Dark Matter?

Dark matter is an invisible mass that is thought to make up about 23 percent of the universe. Dark matter has mass but cannot be seen, so scientists infer its presence based on the gravitational pull it exerts on regular matter.

Researchers remain curious about the properties of dark matter, such as whether it is icy cold as many theories predict, or if it is warmer.

6 Where are the Missing Baryons?

Dark energy and dark matter combine to occupy approximately 95 percent of the universe, with regular matter making up the remaining 5 percent. But, researchers have been puzzled to find that more than half of this regular matter is missing.

This missing matter is called baryonic matter, and it is composed of particles such as protons and electrons that make up majority of the mass of the universe’s visible matter.

Some astrophysicists suspect that missing baryonic matter may be found between galaxies, in material known as warm-hot intergalactic medium, but the universe’s missing baryons remain a hotly debated topic.

5 How do Stars Explode?

When massive stars run out of fuel, they end their lives in gigantic explosions called supernovas. These spectacular blasts are so bright they can briefly outshine entire galaxies.

Extensive research and modern technologies have illuminated many details about supernovas, but how these massive explosions occur is still a mystery.

Scientists are keen to understand the mechanics of these stellar blasts, including what happens inside a star before it ignites as a supernova.

4 What Re-ionized the Universe?

The broadly accepted Big Bang model for the origin of the universe states that the cosmos began as a hot, dense point approximately 13.7 billion years ago.

The early universe is thought to have been a dynamic place, and about 13 billion years ago, it underwent a so-called age of re-ionization. During this period, the universe’s fog of hydrogen gas was clearing and becoming translucent to ultraviolet light for the first time.

Scientists have long been puzzled over what caused this re-ionization to occur.

3 What’s the Source of the Most Energetic Cosmic Rays?

Cosmic rays are highly energetic particles that flow into our solar system from deep in outer space, but the actual origin of these charged subatomic particles has perplexed astronomers for about a century.

The most energetic cosmic rays are extraordinarily strong, with energies up to 100 million times greater than particles that have been produced in manmade colliders. Over the years, astronomers have attempted to explain where cosmic rays originate before flowing into the solar system, but their source has proven to be an enduring astronomical mystery.

2 Why is the Solar System so Bizarre?

As alien planets around other stars are discovered, astronomers have tried to tackle and understand how our own solar system came to be.

The differences in the planets within our solar system have no easy explanation, and scientists are studying how planets are formed in hopes of better grasping the unique characteristics of our solar system.

This research could, in fact, get a boost from the hung for alien worlds, some astronomers have said, particularly if patterns arise in their observations of extrasolar planetary systems.

1 Why is the Sun’s Corona so Hot?

The sun’s corona is its ultra-hot outer atmosphere, where temperatures can reach up to a staggering 10.8 million degrees Fahrenheit (6 million degrees Celsius).

Solar physicists have been puzzled by how the sun reheats its corona, but research points to a link between energy beneath the visible surface, and processes in the sun’s magnetic field. But, the detailed mechanics behind coronal heating are still unknown.

Cecilia Payne-Gaposchkin

Cecilia Payne was born in Wendover, England in 1900. In 1919 while at Newham college at Cambridge, she became interested in astronomy after hearing a lecture by Professor Eddington about his eclipse expedition to Brazil.

Because astronomy continued to be seen as a branch of mathematics she was unable to change her major field of study to astronomy from physics. She continued however to attend Eddington’s lectures. When she finally confessed her wish to become an astronomer to Eddington his response was, “I can see no insuperable objections.” After graduating from Cambridge she became concerned about the future for women in astonomy careers in England. She chose to head toward the United States where she thought a woman might be more accepted. She received a fellowship to study at Harvard Observatory and so she headed across the seas to continue her career.

Payne quickly settled in among the women at the Harvard Observatory, working there under the director Harlow Shapley. She quickly began an investigation of the stellar spectra being compiled for the Henry Draper catalog. In 1925 Cecilia Payne became the first person, woman or man, to receive an Ph.D. in astronomy from Harvard. Shapley had attempted to get her a Ph.D. in the already existing physics department, but the chair refused. To get around this roadblock she received her Ph.D. in astronomy instead.

Her thesis, later published as the observatory’s first monograph, Stellar Atmospheres, A contribution to the Observational Study of High Temperature in the Reversing Layer of Stars was labeled at the time and for many years afterwards as “the most brilliant Ph.D. thesis ever written in astronomy.” In this thesis Payne calculated a temperature scale to match the classification system which Annie Cannon had developed.

She also theorized about the composition of the stars. She suggested that the stars were mostly hydrogen. However, when Eddington heard this theory he told her that she was wrong because astronomers at the time felt that all celestial bodies had very similar compostions. As a result, Payne wrote in her thesis that her results were improbable and probably wrong. Today, of course, we know her results were actually fairly accurate.

After her fellowship was finished, Payne was hired by Harvard and worked with the various other women then employed at the Harvard Observatory. In 1932 Payne began a tour of Europe visiting various observatories around the continent. Her final destination was Berlin for the meeting of the Astronomische Gesellschaft. She documents in her autobiography the conditions both in Russia and in Nazi Germany at the time. While in Berlin she met a young Russian Astronomer Sergei Gaposchkin and heard his plight as a Russian Astronomer in Nazi Germany. She resolved to help him get out of Europe. She found him a position at Harvard and he arrived in November 1932. Less than two years later in March 1934 Sergei and Cecilia were married.

Cecilia continued to publish and wrote several other books, some of them coauthored by her husband. Payne, with Annie Cannon, eventually received the title of Astronomer from Harvard . Despite the fact that she lectured at the University, it was not until the 1950s that Payne received the title of Professor and eventually Chair of the Astronomy Department at Harvard. Cecilia Payne-Gaposchkin is one of the great women astronomers of this century.

Are We Living Inside a Computer Simulation?

The popular film trilogy, The Matrix, presented a cyberuniverse where humans live in a simulated reality created by sentient machines.

Now, a philosopher and team of physicists imagine that we might really be living inside a computer-generated universe that you could call The Lattice. What’s more, we may be able to detect it.

In 2003, British philosopher Nick Bostrom published a paper that proposed the universe we live in might in fact really be a numerical computer simulation. To give this a bizarre Twilight Zone twist, he suggested that our far-evolved distant descendants might construct such a program to simulate the past and recreate how their remote ancestors lived.

He felt that such an experiment was inevitable for a supercivilization. If it didn’t happen by now, then in meant that humanity never evolved that far and we’re doomed to a short lifespan as a species, he argued.

To extrapolate further, I’d suggest that artificial intelligent entities descended from us would be curious about looking back in time by simulating the universe of their biological ancestors.

As off-the-wall as this sounds, a team of physicists at the University of Washington (UW) recently announced that there is a potential test to seen if we actually live in The Lattice. Ironically, it would be the first such observation for scientifically hypothesized evidence of intelligent design behind the cosmos.

The UW team too propose that super-intelligent entities, bored with their current universe, do numerical simulations to explore all possibilities in the landscape of the underlying quantum vacuum (from which the big bang percolated) through universe simulations. “This is perhaps the most profound quest that can be undertaken by a sentient being,” write the authors.

Before you dismiss this idea as completely loony, the reality of such a Sim Universe might solve a lot of eerie mysteries about the cosmos. About two-dozen of the universe’s fundamental constants happen to fall within the narrow range thought to be compatible with life. At first glance it seems as unlikely as balancing a pencil on its tip. Jiggle these parameters and life as we know it would have never appeared. Not even stars and galaxies. This is called the Anthropic principle.

ANALYSIS: Building the Universe Inside a Supercomputer

The discovery of dark energy over a decade ago further compounds the universe’s strangeness. This sort of “antigravity” pushing space-time apart is the closest thing there is to nothing and still is something. This energy from the vacuum of space is 60 orders of magnitude weaker that what would be predicted by quantum physics.The eminent cosmologist Michael Turner ranks dark energy as “the most profound mystery in all of science.”

We are also living at a very special time in the universe’s history where it switched gears from decelerating to accelerating under the push of dark energy. This begs the question “why me why now?” (A phrase popularly attributed to Olympic figure skater Nancy Kerrigan in 1994 when she was attacked and crippled by an opponent.)

If dark energy were slightly stronger the universe would have blown apart before stars formed. Any weaker and the universe would have imploded long ago. Its incredibly anemic value has been seen as circumstantial evidence for parallel universes with their own flavor of dark energy that is typically destructive. It’s as if our universe won the lottery and got all the physical parameters just right for us to exist.

Finally, an artificial universe solves the Fermi Paradox (where are all the space aliens?) by implying that we truly are alone in the universe. It was custom made for us by our far-future progeny.

Biblical creationists can no doubt embrace these seeming cosmic coincidences as unequivocal evidence for their “theory” of Intelligent Design (ID). But is our “God” really a computer programmer rather than a bearded old man living in the sky?

Currently, supercomputers using a impressive-sounding technique called lattice quantum chromodynamics, and starting from the fundamental physical laws, can simulate only a very small portion of the universe. The scale is a little larger than the nucleus of an atom, according UW physicist Martin Savage. Mega-computers of the far future could greatly expand the size of the Sim Universe.

ANALYSIS: Artificial Universe Created Inside a Supercomputer

If we are living in such a program, there could be telltale evidence for the underlying lattice used in modeling the space-time continuum, say the researchers. This signature could show up as a limitation in the energy of cosmic rays. They would travel diagonally across the model universe and not interact equally in all directions, as they otherwise would be expected to do according to present cosmology.

If such results were measured, physicists would have to rule out any and all other natural explanations for the anomaly before flirting with the idea of intelligent design. (To avoid confusion with the purely faith-based creationist ID, this would not prove the existence of a biblical God, because you’d have to ask the question “why does God need a lattice?”)

If our universe is a simulation, then those entities controlling it could be running other simulations as well to create other universes parallel to our own. No doubt this would call for, ahem, massive parallel processing.

If all of this isn’t mind-blowing enough, Bostrom imagined “stacked” levels of reality, “we would have to suspect that the post-humans running our simulation are themselves simulated beings; and their creators, in turn, may also be simulated beings. Here may be room for a large number of levels of reality, and the number could be increasing over time.”

To compound this even further, Bostrom imagined a hierarchy of deities, “In some ways, the post-humans running a simulation are like gods. However, all the demigods except those at the fundamental level of reality are subject to sanctions by the more powerful gods living at lower levels.”

If the parallel universes are all running on the same computer platform could we communicate with them? If so, I hope the Matrix’s manic Agent Smith doesn’t materialize one day.

To borrow from the title of Isaac Asimov’s novel I Robot, the human condition might be described as I Subroutine.