Babies are always more trouble than you thought–and more wonderful–Charles Osgood
We think that our Universe was born almost 14 billion years ago in the inflationary Big Bang. It started as an exquisitely small Patch, and then–in the smallest fraction of a second–expanded exponentially to attain làm bằng đại họcsize. Something, we do not know precisely what, made that tiny Patch undergo this runaway inflation. That tiny Patch, far too small for a human being to see, so small that it was almost, but not exactly, nothing, was, in fact, so dense and hot that all that we are and all that we can ever know, sprung from it. Space and Time were born together in the wildly expanding fireball of the Big Bang. The baby Universe was filled with extremely energetic radiation, a writhing sea of hot particles of light (photons). The entire baby Universe glowed brilliantly. What we now see almost 14 billion years later is the fading, greatly expanded and expanding, aftermath of that initial burst of brilliance. As our Universe grew to its present enormous size, the flames of its formation faded. And now we watch from our small, obscure, rocky little planet as our Universe grows larger and larger, colder and colder, darker and darker, dimming eerily to ash.
Georges Henri Joseph Edouard Lemaitre (1894-1966) was a Belgian priest, astronomer, and professor of physics at the Catholic University of Louvain. Lemaitre was one of the first to propose that our Universe is expanding, as well as formulating the theory that would eventually be called the Big Bang Universe. Once Lemaitre observed that “The evolution of the world may be compared to a display of fireworks that has just ended: some few wisps, ashes, and smoke. Standing on a cooled cinder, we see the slow fading of the suns, and we try to recall the vanished brilliance of the origins of the worlds.”
Almost 14 billion years ago, all of Spacetime emerged from a tiny primordial brew of searing-hot, densely packed particles, that we commonly call the “fireball”. Spacetime has been expanding from this initial incandescent state, and cooling off, ever since. All of the galaxies are floating away from each other and away from our own large barred-spiral Galaxy, the star-fired Milky Way–but our Universe has no center, everything is moving away from everything else, due to the expansion of Spacetime. The expansion of the Universe is often compared to a loaf of rising raisin bread. The dough expands, carrying the raisins along with it for the ride. The raisins become ever more widely separated from each other because the dough is expanding.
On the largest scales, the Universe looks the same wherever we observe it: from all directions and all regions of mysterious Spacetime. The most widely accepted theory, based on observations and measurements, suggests that the inflation is the most credible event known that could have caused our Universe to evolve in the way that it has apparently evolved. In the tiniest fraction of a second, inflation is thought to have literally blown up like a balloon or bubble, each and every region of Space by a factor of at least 10 to the 27th power (10 followed by 26 zeroes). Before inflation blew up this fantastic, mysteriously enchanting, and beautiful Patch that is our home, the region of the Universe that we can observe today was a smooth speck much smaller than a proton. Although our visible Universe has expanded like a balloon or bubble, what we can now see of it is flat and open, rather than closed, spherical, and bubble-like. After the inflation ceased its ferocious fury of wild expansion, that original tiny, tiny seed had grown to macroscopic size. At this point our Universe was a soup–more precisely a plasma–of elementary particles. Photons and other quickly zipping hot little particles, generically termed radiation, gradually lost energy (cooled off) as the Universe continued to expand at a more stately pace.
When we refer to the visible Universe, we are referring to that relatively small part of the entire Universe that we can observe. The rest of it–the lion’s share of it–resides beyond what we term the cosmological horizon. The light from these remote regions, beyond the horizon, has not had time to reach us since the Big Bang birth of our Universe so many billions of years ago. No signal in our Universe can travel faster than light, and this Universal speed limit has made it impossible for us to directly observe these very distant portions of Space.
The temperature throughout that original primordial fireball was almost, but not precisely, uniform. This lack of complete and precise uniformity is the key to everything; everything that we are, and that we know of in our Universe, sprung from this barely existing lack of perfect uniformity. Before the inflation, that exquisitely tiny primordial Patch was completely smooth, homogeneous, and looked exactly the same in all directions. Inflation, it is believed, explains how this entirely homogeneous little Patch began to ripple.
The tiny fluctuations, the primordial ripples that occurred in the smallest units we can measure (quantum), the infinitesimal ripples in Spacetime, were born as a result of the inflation. The inflation explains how these quantum fluctuations, in the smooth and isotropic newborn Universe, would eventually grow into galaxies and other large-scale structures. To paraphrase the late Dr. Carl Sagan of Cornell University, we are the eyes of the Universe seeing itself. But, of course, nothing with eyes to see lived as yet in these first moments of our Universe’s existence.
The weird world of the quantum is a jittery, foamy arena, where nothing can be perfectly still. The originally smooth and isotropic Universe developed tiny hills and valleys. The valleys gradually became emptier and emptier; the hills heavier and heavier, higher and higher, because of gravity. Gravity relentlessly drew the original stuff of the baby Universe into the heavier hills, that ultimately accumulated more and more of the matter composing the primordial soup. The impoverished plains, that lacked the gravitational lure of the heavier hills, became increasingly depleted of this primordial broth. Over time, larger and larger structures grew in our Universe’s wealthier and heavier hills, because they exerted an increasingly more powerful tug on the primordial matter–the heavier they became, the greater their gravitational lure. The large-scale structure of our Universe originated as tiny variations in the density of matter in the ancient Universe. Gravitational attraction made more and more matter clump together.
You Must Have Been A Beautiful Baby!
In December 2012, astronomers released a new and beautiful “baby picture” of the Universe. The all-sky image was derived from nine years’ worth of accumulated data from NASA’s recently retired Wilkinson Microwave Anisotropy Probe (WMAP), launched back in 2001. WMAP, from where it floated about a million miles away from our planet–in the direction opposite the Sun–searched the sky, mapping out the distant relic afterglow of the ancient, hot Universe. The spacecraft did its job with admirable accuracy.
The new beautiful “baby picture” is actually a map showing the temperature of the relic radiation of the Big Bang–the Cosmic Microwave Background (CMB) radiation. This new map records the remote era when our baby Universe was “only” 375,000 years old. The picture displays temperature fluctuations of the CMB as variations in color, with a temperature range of +/- 200 microKelvin.
These subtle patterns enable astronomers to make predictions about what happened even earlier in the history of the ancient Universe–as well as what has occurred since. “We are just a speck in the vastness of the Universe, so it is amazing that we have the ability to answer fundamental questions about the vast Universe around us, but the WMAP team has done just that,” Dr. Charles Bennett noted in the December 21, 2012 Space.com. Dr. Bennett, an astrophysicist at Johns Hopkins University in Baltimore, Maryland, who leads the team, added that “It was possible because we can detect and study the ancient light, the oldest light in the Universe.”