SURVEILLING THE UNIVERCE FROM THE SOUTH POLE.
Nevertheless, the universe has no edge or center, no particular point of origin, and nothing exists outside it--not even empty space. Does that seem seem strange?--it certainly does. Consider, though, the two-dimensional analogy of a beach ball: the surface of a beach ball has a finite area, but no edge and no preferred center. When the universe was less than 0.001 seconds old, matter burst forth in matter-antimatter pairs, quickly annihilating one another with the emission of gamma rays in a frenzied depopulation. For every 10,000,000,000 annihilations, resulting in 10,000,000,000 residual gamma ray photons, only one particle of matter remained to evolve into the universe we see today--but what happened to the gamma ray photons?
All the space of the nascent cosmos was like the interior of the sun: a plasmatic soup of gamma ray photons, protons, and electrons crowded so close together they constantly bounced off each other like a cosmic billiards game. In these close quarters, photons were unable to travel freely, rendering the early universe opaque like a pea soup fog.
Then, 300,000 years after the Big Bang, the inchoate universe cooled to a temperature of 3,000 Kelvin. At this stage of expansion and cooling, called the last scattering, the universe cooled enough for the electrons and protons whizzing about to combine into hydrogen atoms, creating space for the photons to travel uninhibited in a now transparent universe.
By this stage, because of the expansion and cooling, the initial gamma rays had stretched into the infrared part of the spectrum. Now, 13,000,000,000 years later, the universe has expanded beyond the capacity of our imaginations, and the same initial light has further stretched, or red-shifted, by a factor of 1,000 into microwave radiation, the temperature proportionately decreasing by a factor of 1,000 to the corresponding temperature of 2.7 K.
These same photons, cosmic microwave background (CMB) radiation, still permeate the entire universe with thousands of microwave photons per cubic inch, like the radiation in your microwave oven but at a lower power, and carry a portrait of a baby universe at only 300,000 years old. Because the universe has no center and no edge, the microwave radiation floods us from all directions. Although invisible to our eyes, CMB radiation falls into the television transmission region of the spectrum and contributes to the static snow seen between "The Simpsons" and "Judge Judy."
When discovered in the 1960s, CMB radiation (the embers of the Big Bang) appeared to fill the sky uniformly, which raised a serious question: if CMB is uniform, how can there be galaxies today? Supporters of the Big Bang Theory began to search in earnest for ever-so-slight fluctuations in CMB, because the future of the theory depended on the discovery of these fluctuations.
So, in 1992, the Cosmic Background Explorer satellite (COBE) searched for the predicted fluctuations. They appeared as coarse blobs, like mottled ripples on the surface of a lake. These blobs are hot and cold spots, millionths of a degree warmer or cooler than the 2.7 K background radiation temperature. The image of the blobs--frozen at the time of last scattering and carried by the escaping photons--reveals the incontrovertible conditions that created the universe, as if God left a message for us to discover. Hence, the discovery of CMB radiation ushered in one of the most-compelling frontiers of scientific investigation.
While COBE revealed the fluctuations, the image of the ripples appeared blurry--like looking at a lake through a soda bottle. Following the success of COBE, astrophysicists planned further experiments to produce a clearer image of CMB to show the details of the fluctuations, expecting to find discrete temperature fluctuations at an angular scale of one degree. These astrophysicists built a new generation of radio telescopes for observations from balloons, satellites, and the South Pole. BOOM-ERanG, a two-ton balloon-borne telescope, mapped CMB radiation in greater detail. It rode the polar vortex wind pattern, circumnavigating Antarctica at 79 degrees latitude in 10 days, landing several miles from McMurdo Station. Dangling from a balloon, the telescope floated above the atmospheric water vapor, which absorbs microwave radiation. BOOMERanG discovered the angular size of the largest blobs: one degree, confirming predictions.
What caused the CMB blobs? Before the universe became transparent while the plasmatic soup of photons, protons, and electrons ricocheted off of each other, two forces competed in a tug-of-war: gravity pulling inwards and photons pushing outwards.
Accordingly, these competing forces created oscillations of expansion and contraction, like an oscillating ball suspended between two springs: gravity compressed denser regions into high-density blobs while photon pressure expanded less-dense regions into low-density blobs.
The blobs appear in a range of different sizes, preferentially at particular sizes, up one degree across (300,000 light years), each with different temperature deviations from the average 2.7 K. A graph of the power spectrum summarizes the observations, showing the temperature deviations, or anisotropics, for every detectable blob size; the graph looks like a mountain range, indicating that the largest peak, or temperature deviation, occurs in the one-degree blobs, with lower peaks at smaller angular sizes. These so-called acoustical peaks, analogous to the overtone series of a musical instrument, contain information about the instrument and its maker. Thus, the map of CMB, though appearing as a collection of mere motley blobs, reveals an image of God's fantastic cosmic bell choir ringing in the universe, echoing into eternity.
So, what do these esoteric blobs tell us? The size of the blobs and their temperature deviations convey information about the overall characteristics and evolution of the entire universe, as described by the so-called cosmological parameters--a set of numbers, and the Holy Grail of cosmology. These parameters include the curvature of space; density of ordinary matter and of mysterious, invisible dark matter; the expansion rate of the universe; and the mass of the universe.
How can the size of the blobs tell us the mass of the universe? The same way the amount of weight you put on a spring determines how far it will compress, the density of the universe determines how far the oscillating blobs compressed before internal pressure pushed back. Therefore, the amount of compression in the blobs, revealed by their sizes, tells us the mass of the universe.
How are the other cosmological parameters found? Among the numerous theoretical and experimental approaches, CMB data offers a direct approach. Specifically, mathematical models of the early universe can be adjusted by selecting combinations of values for each of the cosmological parameters until the resulting CMB power spectrum fits the actual CMB power spectrum. The result is further clues to our origin and destiny.
After the last scattering, while CMB carried a frozen image of the baby universe, the primordial blobs themselves continued to evolve. The warmer blobs, just above 2.7 K, corresponding to regions of higher density in the primordial soup, clumped together under their own gravitational attractions--like cumulus clouds appearing in the sky--and amassed yet more gravity, pulling together sufficient matter to spark and stoke the stars and galaxies, leading to our own birthplace, planet Earth.
Ultimately, the blobs seen in CMB led to the emergence of humans who could look into the night sky to appreciate the splendor of the Milky Way and to contemplate our origins. Thus, recognizing the revelations of the early universe manifest by CMB, we stand in a unique position in the history of humanity to bear witness to the echoes of heralds from an eternity ago.
BY JOHN BIRD AND JENNIFER MCCALLUM
John Bird and Jennifer McCallum are coauthors of One Day, One Night: Portraits of the South Pole, from which this article is adapted.
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|Title Annotation:||SCIENCE & TECHNOLOGY|
|Author:||Bird, John; McCallum, Jennifer|
|Publication:||USA Today (Magazine)|
|Date:||Jul 1, 2018|
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