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23
The Endless Supply of Energy Hunt
July 23, 2010 | 11 Comments
It’s out there, or so they say in the cosmic physics community. There is a mysterious “dark energy” believed to constitute nearly three-fourths of the mass and energy of the Universe out there. That’s a lot of power.
Dark energy is the label scientists have given to what is causing the Universe to expand at an accelerating rate. The acceleration was discovered in 1998, but its cause remains unknown. Physicists have advanced competing theories to explain the acceleration with the necessary dark energy the current leader.
The numbers are just comprehendible in order of magnitude ranges – leaving estimations in the pure supposition mode. Its safe to say that once dark energy is nailed down the amount from a species point of view looking out from a small planet will be ‘endless’.
There are major problems. As much as there should be out there, it’s going to be widely dispersed – and even if there are concentrations, these will be thin pickings. The energy will likely be quite far away, too. Yet, something is pulling the Universe apart, and figuring out what and how might have important implications for energy in general.
That makes news on the dark energy front interesting, maybe useful and certainly instructive.
Pioneering observations with the National Science Foundation’s giant Robert C. Byrd Green Bank Telescope (GBT) have given astronomers a new tool for mapping large cosmic structures. Physicists believe the best way to test the competing theories to explain the acceleration is to precisely measure large-scale cosmic structures.
Green Bank Telescope. Click image for the largest view. Image Credit: The National Science Foundation.
The thinking is sound waves in the matter-energy soup of the extremely early Universe are thought to have left detectable imprints on the large-scale distribution of galaxies in the Universe. The GBT researchers developed a way to measure such imprints by observing the radio emission of hydrogen gas. Their technique, called intensity mapping, when applied to greater areas of the Universe, could reveal how such large-scale structures have changed over the last few billion years, giving insight into which theory of dark energy is the most accurate.
Imagine you’re in space with a wee explosive charge where the gravity is about uniform in all directions. Set the explosive off and the instant the chemical energy is expended maximum velocity would be achieved. Assuming your explosive isn’t too vigorous the exploded bits would be overcome by there own gravity and clump back together if the gravity around isn’t too powerful. There’s your recurring big bang theory in the ultra simplified mode.
That’s not what’s happening out there.
There isn’t enough matter with gravity to slow the whole thing down.
Some kind of energy is pushing things ever faster and further apart – some 14 or 15 billion years later.
Inquiring mind are intrigued. What is that energy? Can it be put to use? First it has to be found. Science is still in ‘clue’ mode on this one.
To get their results, the researchers used the GBT to study a region of sky that previously had been surveyed in detail in visible light by the Keck II telescope in Hawaii. This optical survey used spectroscopy to map the locations of thousands of galaxies in three dimensions. With the GBT, instead of looking for hydrogen gas in these individual, distant galaxies — a daunting challenge beyond the technical capabilities of current instruments — the team used their intensity-mapping technique to accumulate the radio waves emitted by the hydrogen gas in large volumes of space including many galaxies.
Jeffrey Peterson, of Carnegie Mellon University explained, “Since the early part of the 20th Century, astronomers have traced the expansion of the Universe by observing galaxies. Our new technique allows us to skip the galaxy-detection step and gather radio emissions from a thousand galaxies at a time, as well as all the dimly-glowing material between them.”
Tzu-Ching Chang, of the Academia Sinica in Taiwan and the University of Toronto comes to the point, “Our project mapped hydrogen gas to greater cosmic distances than ever before, and shows that the techniques we developed can be used to map huge volumes of the Universe in three dimensions and to test the competing theories of dark energy.”
The astronomers also developed new techniques that cleaned up both man-made radio interference and radio emission caused by more-nearby astronomical sources, leaving only the extremely faint radio waves coming from the very distant hydrogen gas. The result was a map of part of the “cosmic web” that correlated neatly with the structure shown by the earlier optical study. The team first proposed their intensity-mapping technique in 2008, and their GBT observations were the first test of the idea.
Ue-Li Pen of the University of Toronto said, “These observations detected more hydrogen gas than all the previously-detected hydrogen in the Universe, and at distances ten times farther than any radio wave-emitting hydrogen seen before.”
Where does that get us? Closer by some clues. The theories that explain the Universe flying apart at ever faster speeds involves a great deal of power. Accelerating a baseball is one thing, moving up to a galaxy and then the whole universe something entirely different.
Just what the energy is will the precious answer. Then the questions really get fascinating. Has anyone put a calculation to the power required to accelerate the Universe? It will be a big number – an energy source well worth understanding even if not collected.
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Has anyone put a calculation to the power required to accelerate the Universe? – Interesting question.