Albert Einstein once said that "The most beautiful thing we can experience is the mysterious. It is the source of all true art and all science. He to whom this emotion is a stranger, who can no longer pause to wonder and stand rapt in awe is as good as dead: His eyes are closed."
Today our Universe is star-blasted with light--billions upon billions of incandescent stars set the more than 100 billion galaxies of our visible Universe on fire. The visible Universe is that relatively small portion of the Cosmos that we can observe, both with our unaided eyes and with the help of some very sophisticated telescopes. We cannot observe objects that may (or may not) exist beyond the edge--the horizon--of our visible Universe. This is because the light of whatever may exist beyond the horizon has not had sufficient time to reach us since our Universe came into existence in the Big Bang almost 14 billion years ago. The speed of light, the universal speed limit, has rendered this impossible. When we look deep into Space, we look back in Time, because the farther away a luminous object is, the longer it takes for its light to reach us.
No signal in the Universe can travel faster than light and the light from distant objects in Spacetime can travel to us no faster than that universal speed limit. Time is considered to be the fourth dimension. The three spatial dimensions of our familiar world are up-down, back-and-forth, and side-to-side. One cannot locate an object in Space without also locating it in Time.
Just after the Big Bang birth of the Universe so many billions of years ago, there was an era without stars; without light. This ancient era is called the Cosmic Dark Ages. It came to an end when the first generation of stars were born. Many astronomers believe that the stars were born before the galaxies, although this viewpoint is controversial. The first galaxies were dark and opaque blobs of gas, pooling at the centers of dark-matter halos, until they pulled in the first batches of enormous fiery baby stars with their intense gravitational grip. The dark-matter is mysterious stuff. It is probably composed of some unidentified exotic particles that do not interact with light, and are therefore invisible. The dark matter is much more abundant than the so-called "ordinary" matter that we can see--the "ordinary", familiar matter that composes the incandescent stars, their retinue of planets and moons, and creatures like us. "Ordinary" matter is atomic matter; the dark matter is not composed of atoms. Atomic matter composes all of the elements of the Periodic Table.
The Universe was a witch's cauldron of searing-hot plasma for about three hundred thousand years after the "Bang". At last, protons (which along with neutrons compose atomic nuclei) and electrons (which surround the nuclei of atoms in a cloud) combined to form hydrogen--the lightest "ordinary" atomic element in the Universe, as well as the most abundant. About 700 million years or so after the birth of the first generation of stars and galaxies, the Universe was mysteriously reionized. That is, something tore the atoms apart, converting hydrogen back into its constituent protons and electrons.
Little is known about that ancient and mysterious era when the first galaxies were born. However, sometimes Mother Nature provides us with a gift--and gravitational lensing is such a gift. Gravitational lensing is a prediction of Albert Einstein's Theory of General Relativity, stating that the presence of matter (energy density) can curve Spacetime. Therefore, the path that a light ray travels will be deflected due to this curvature.
Einstein's first theory of Relativity, his Special Theory of Relativity (1905), describes a Spacetime that has frequently been likened to an artist's canvas. The artist paints lines and points on this marvelous canvas that displays all that has ever occurred, is occurring, will occur. This canvas is the stage where the drama is being played out, rather than the drama itself. The great achievement uniting the stage with the drama came later when, in 1915, Einstein presented to the world his revolutionary Theory of General Relativity. Spacetime becomes a star actor in this greatest of all stage plays. In this play, Spacetime tells mass how to move, and mass tells Spacetime how to curve. Spacetime is as flexible as a trampoline onto which you toss a bowling ball. Imagine that ball to be a heavy mass, just like a star. It creates a dimple on the fabric of the trampoline. If you then throw a handful of marbles onto that marvelous trampoline, they will travel curved paths around the "star", just as if they were planets orbiting a real star. Take the bowling ball away, and the marbles follow straight paths. The trampoline is Spacetime, and it curves accordingly when the mass of the bowling ball, or "star", warps it. The marbles, or the "planets", obey the dictates of the more massive "star's" warpage of Spacetime. The trampoline is just as much of an actor in the play as the bowling ball and the marbles. The drama will go on as long as the main performers exist.
Gravitational lensing refers to the path that light takes when it has been deflected. It occurs when the mass of a foreground object bends and distorts the light of a background object--the foreground object is the lens. The light need not be exclusively visible light--it can be any type of radiation. As a result of lensing, light rays that would normally not have reached the observer are bent from their paths in such a way that they move towards the observer. Likewise, light can also be bent away from an observer. There are different types of lenses: strong lenses, weak lenses, and microlenses. The differences between these three different types of gravitational lenses depends on the position of the background source, lens and observer, and the mass and shape of the foreground lens. The foreground lens determines how much light is deflected and where this light goes.
Dr. Wen Zheng, of Johns Hopkins University, and his colleagues, announced the discovery of the most distant and, therefore, most ancient galaxy spotted so far. Their discovery was announced in September 2012 in the journal Nature. The researchers discovered the galaxy using gravitational lensing--warped light revealed the existence of this very remote object. The galaxy dates back to a trifling 500 million years after the "Bang", and it is about 13.2 billion light-years from Earth. One light-year is the distance that light can travel in a vacuum in one year, which is 5,880,000,000,000 miles! Such extremely remote and ancient objects are technically beyond the reach of existing telescopes. Capturing images of the very ancient Universe is the main quest of the upcoming James Webb Space Telescope (JWST), expected to launch in 2018.
But Zheng and colleagues got a haunting glimpse into the mysteries of this ancient era courtesy of gravitational lensing. In this case, gravitational lensing converted a foreground galaxy cluster into a magnifying glass for the ancient galaxy behind it. The very remote and ancient galaxy was revealed in pictures taken by the venerable Hubble Space Telescope (HST) because the massive gravity of the foreground cluster magnified it more than 15 times.
The astronomers estimate that the ancient background galaxy is a bouncing baby at less than 200 million years of age, and that it was born about 300 million years after the "Bang". Also, the remote galaxy's approximately 100 million solar-masses of stars render it a mere 1% as massive as our own large spiral Galaxy, the Milky Way.
Investigations of the Cosmic Microwave Background (CMB) radiation, the relic afterglow of the "Bang", indicate that the mysterious era of reionization was caused by the ultraviolet (UV) radiation emitted by ancient galaxies such as this one. This discovery strengthens that interpretation.
Dr. Abraham (Avi) Loeb, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, explained in the 21 September 2012 issue of the journal Science that "Theoretical models of reionization associate most of the UV production with galaxies of this or somewhat lower masses in exactly the same cosmic time. However, with only one galaxy at hand, it is difficult to draw robust statistical inferences." Loeb added that current lensing observations or upcoming telescopes, such as the JWST, will help scientists determine whether or not such ancient galaxies really were the primary sources of the ionizing radiation.
As that great scientific detective, Albert Einstein, once said: "The eternal mystery of the world is its comprehensibility."
I am a writer and astronomer whose articles have been published since 1981 in various newspapers, magazines, and journals. Although I have written on a variety of topics, I particularly love writing about astronomy because it gives me the opportunity to communicate to others the many wonders of my field. My first book, "Wisps, Ashes, and Smoke," will be published soon.