Experiment to Turn Light Into Matter
Image: A graphical demonstration of the backg
Watching the Universe Grow Inside a Supercomputer Imagine if you could assemble all known physics, throw it into a powerful supercomputer and watch a virtual universe evolve. Well, that's exactly what a team of physicists at Stanford University's Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) have done. This mammoth task has culminated in a part-physics/part-art exhibit that is being showcased in 3D videos playing at a theater on the SLAC National Accelerator Laboratory and featured at planetariums in New York City and San Francisco. In the videos, everything from dark matter to star formation is simulated. One simulation even demonstrates the majestic collision between two galaxies just as they merge to become one. Here's a sneak peek of a few of the stunning scenes showcased in the simulations.
Image: The large scale structure of the "web"
Dark Matter The KIPAC team have simulated everything from the first few milliseconds of a supernova detonation to the 13.75 billion years of cosmic evolution and condensed the trillions of bytes of data into short animations lasting only minutes. "I'm trying to predict the past -- how the universe came to be the way that it is today," said Tom Abel, an associate professor of physics at Stanford University and head of KIPAC's computational physics department. Of particular interest to cosmologists is the science behind mysterious dark matter -- the "invisible" stuff that is theorized to pervade the whole cosmos, supplying the majority of the Universe's mass. Therefore, to visualize the early formation of large-scale dark matter structure (pictured here) isn't only a beautiful sight, it's also of paramount scientific importance.
Image: When two galaxies collide. Credits: SL
Galactic Mergers In one simulation, the gravitational effects of two spiral galaxies colliding is envisioned. Before they merge as one, the pair undergo an orbital dance, scattering stars as they go. Astrophysicists have predicted and observed rapid star birth inside galactic mergers, so far from being destructive events, galaxy collisions can kick-start star formation.
Image: A dwarf galaxy grows. Credits: SLAC/KI
Dwarf Galaxies Another simulation shows the formation of some of the earliest galaxies. Only a couple of hundred million years after the Big Bang, dwarf galaxies started to appear. It is thought that these galaxies eventually clumped together, forming the foundation of larger galaxies we see today -- like the Milky Way.
Image: Baby stars ignite inside a cloud of de
The First Stars The first stars to form were very massive, feeding off and ionizing their proto-galaxies' supply of hydrogen. These stars lived fast and died young, exploding as powerful supernovae. The KIPAC simulations take the viewer on an immersive tour of these powerful events using computational power that hasn't been available till now. "Creating these animations is a real joy these days because computers and software are so much more powerful today," Abel said. "Not long ago it took us weeks to produce a single animation. Now we can do one in an afternoon. "It's an immersive environment," he continued. "You can explore three-dimensional data, 'Avatar'-style. It's wonderful to have the sensation of being inside the cosmological data."
Image: A protostar forming within a nebula.
Not Just a Pretty Picture Astrophysicists work by taking observations and then they try to understand what they are seeing by creating a model. The model will use known physics in an attempt to replicate the observations. Now researchers have Hollywood budget-busting visualization tools in the laboratory, producing mind-blowing simulations of astrophysical phenomena, they are able to chase-down some of the most complex mechanisms that shape the cosmos. For example, the KIPAC visualizations helped Stanford colleagues understand the formation and structure of galactic clusters by simulating the formation of 100 clusters within a virtual cube measuring 4.5 billion light-years per side. So these may be pretty animations, but there is a strong scientific motivation behind their creation.
Image: The first stars in the Universe doused
"These videos aren't just screensavers. They show us how the universe really works," concluded Oliver Hahn, KIPAC post-doctoral researcher, who is using this visualization tool to support his work.
For more information, images and videos of these simulations, see the KIPAC project pages.
MORE ARTICLES BY IAN O'NEILL
Scientists have worked out an easy way of turning light into matter, a process thought to be impossible when first proposed 80 years ago.
The proposed experiment, reported in the journal Nature photonics, would recreate events that occurred in the first 100 seconds of the big bang, as well as in cosmic rays and gamma ray bursts.
In 1934, scientists Gregory Breit and John Wheeler suggested light can be converted into matter by smashing two photons together to create an electron and its antimatter counterpart, a positron.
Breit and Wheeler's calculations were correct, but they never expected anyone to physically demonstrate their prediction.
"The Breit-Wheeler process is one of the simplest interactions of light and matter and one of the purest demonstrations of E=mc2," said the study's lead author Oliver Pike of Imperial College London.
"However, Breit-Wheeler pair production has never been observed. The experimental design we propose can be carried out with relative ease and with existing technology."
Just add gold
The photon collider would convert light directly into matter by using an extremely powerful high intensity laser to fire electrons at almost the speed of light into a slab of gold. This created a beam of photons a billion times more energetic than visible light.
The next step involves firing a separate high energy laser onto the surface of a tiny gold cylinder called a vacuum hohlraum (German for hollow cavity), to create a thermal radiation field of photons.
The researchers would then direct the photon beam from the gold slab through the center of the hohlraum, causing the photons from the two sources to collide and create electrons and positrons, which could be detected as they beamed out of the device.
Matter was first created out of pure energy in 1997 at the Stanford Linear Accelerator Center when a powerful electron beam was fired into a laser beam of photons.
Occasionally an electron collided with a photon pushing it into other photons with enough force to produce an electron and a positron.
"There was not enough energy at Stanford to observe the Breit-Wheeler process, instead a much more complex process was observed -- high-energy photons interacted with multiple low-energy photons in a strong laser field," said Pike.
"In our work, there are no massive particles present. Our scheme would therefore represent the first proof-of-principle of a pure photon-photon collider."
Associate Professor Martin Sevior, an experimental particle physicist at the University of Melbourne, agrees.
"This new method won't require such high energy electron beams as those used by Stanford," said Sevior, who was not involved in the research.
"The Stanford experiment used the world's most intense and highest energy electron beam. This new system will work with a much lower energy electron beam, and it has a much greater photon yield for the same amount of energy."
According to Sevior, photon colliders will have many applications in physics.
"This will help scientists study how photon-to-photon interactions actually work, and study the details of the theory of quantum electrodynamics," he said.
This article originally appeared on ABC Science Online.