The Universe: Rushing To Nothingness
It is generally thought that the Universe was born almost 14 billion years ago in the wild, faster-than-the-speed-of-light inflation of the Big Bang, starting out as an unimaginably small Patch that was smaller than an elementary particle–and then, in the smallest fraction of a second, expanded exponentially to attain macroscopic size. Something mysterious and unknown caused that tiny, tiny, and very hot and dense Patch–that was almost, but not precisely nothing–to become the Cosmic Wonderland that we see today. Everything we are, everything we know, originated from that mysterious Patch that started out smaller than a proton. The newborn Universe was filled with energetic radiation–a violent, stormy sea of searing-hot particles of light (photons), and here we stand now upon our small and rocky world watching helplessly as the raging fire of our dying Cosmos cools and fades away to ash–lam bang dai hoc to go out like a blown candle in the barren desert of unimaginable Nothingness. In June 2016, astronomers announced that they have used the Hubble Space Telescope (HST) to measure the distances to stars inhabiting nineteen galaxies–discovering, to their surprise, that the Universe is currently expanding faster than the rate derived from measurements of the Universe shortly after its birth in the Big Bang.
If this finding is confirmed, this apparent contradiction may provide a precious clue concerning our scientific understanding of three of the Universe’s most mysterious and elusive components: dark energy, dark matter, and neutrinos.
The team of astronomers, led by Nobel Laureate Dr. Adam Riess of Johns Hopkins University and the Space Telescope Science Institute (STSI) in Baltimore, Maryland, used the NASA/ESA HST to make their discovery indicating that the Universe is expanding between five and nine percent faster than previously determined. This finding is clearly in conflict with the rate predicted earlier from measurements of the newborn Universe.
“This surprising finding may be an important clue to understanding those mysterious parts of the Universe that make up 95 percent of everything and don’t emit light, such as dark energy, dark matter, and dark radiation,” Dr. Riess explained in a June 2, 2016 STSI Press Release. Dr. Riess received the Nobel Prize in Physics for his role in the original 1998 discovery of the dark energy.
The favored model indicates that, at the very instant of its birth, the Universe experienced an exquisitely brief period of exponential expansion called inflation. Indeed, the most recent observations and measurements show that inflation is the most likely explanation currently known that could have caused the Universe to evolve in the way that it apparently has over the course of almost 14 billion years. In the smallest fraction of a second, it is thought that inflation blew up–like an extraordinary bubble–literally every region of the tiny Patch of Space by a factor of at least 10 to the 27th power–that is, 10 followed by 26 zeroes. Before inflation blew up this unimaginably tiny Patch to macroscopic proportions, the domain of the Universe that we can see today–the observable Universe–was a smooth elementary particle-size entity. During its most ancient era, our Cosmos was made up of a bizarre plasma composed of elementary particles. Very fast and energetic high-energy photons gradually lost their energy as time passed and began to move more slowly through Space. In other words, they cooled off as the Universe continued to expand. The energy produced poured into the expansion, and in the 13.8 billion years since our Cosmos was born, it has expanded by yet another 10 to the 27th power.
Through The Universe Darkly
What is dark energy? Scientists do not know. This mysterious substance seems to contract current scientific understanding concerning the way that the Universe operates. One thing that can be suggested, however, is this: Because Space is everywhere, the dark energy must be everywhere–because it seems to be a property of Space itself. The effects of the dark energy become increasingly more powerful as Space expands. On the other hand, the force of gravity becomes more powerful when objects are close together and weaker when they are farther apart. Because the force of gravity grows weaker as Space expands–pulling objects farther and farther apart–dark energy now composes more than 2/3 of all the energy in the Universe. This basically means that about 74% of the Universe is unexplained.
Scientific detective stories, such as the quest to find the true identity of the dark energy, are captivating. That is because this sort of question reveals to scientists that there is a gap in their knowledge that needs to be explained–singing a siren’s song that there is a new physics awaiting discovery. This means that the Universe may really be very different from what has been imagined.
Scientists know that light waves–radiation–carry energy. Albert Einstein’s famous equation, E=mc squared, states that energy and matter are the same, and interchangeable–that they are simply different manifestations of the same thing. For example, our own Sun, and other stars are all powered by the conversion of mass into energy.
However, energy is supposed to have a source–either matter or radiation. The concept here is that Space, even when barren of all radiation and matter, nonetheless possesses its own supply of residual energy–the energy of the vacuum. This “energy of space”–the vacuum energy–when considered on a cosmological scale, results in a force that speeds up the expansion of the Universe.
Once idea is that energy can cause some very strange behavior on scales that are smaller than atoms. The physics here, termed quantum mechanics, enables matter and energy to appear out of nothingness–but only for the briefest instant. The perpetual brief appearance and disappearance of matter could be providing energy to otherwise seemingly empty Space. Empty Space is not really empty after all, it is a churning sea of virtual particles that pop into existence, meet up, and then annihilate each other in tiny bursts of energy–the vacuum energy.
It is also possible that the dark energy forms a new, unknown, fundamental force in the Cosmos–something that only first begins to show up when the Universe reaches a certain size. Scientific theories permit the possibility of such unknown forces. The force here might even be transient–thus causing the Universe to accelerate for billions of years before it finally grows weak and essentially vanishes.
A third suggestion is that the answer to this mystery resides within yet another long-standing, nagging question–how to reconcile the physics of the large with the physics of the small. Albert Einstein’s theory of gravity, the Theory of General Relativity (1915), very well explains everything from the motions of the planets to the physics of black holes. Alas, General Relativity does not seem to work on the tiny scale of the particles that compose atoms. In order to predict how particles will behave, scientists need the theory of quantum mechanics. Quantum mechanics explains how particles behave–but it fails to explain what occurs on any scale larger than an atom. The very troubling, intriguing, bewildering mystery that can provide an answer to this puzzle, and combine the two conflicting theories of General Relativity and quantum mechanics–that work well alone, but not together–might finally yield a natural explanation for dark energy.
At the end of the 20th century, astronomers, including Dr. Riess, first observed that the Universe is speeding up in its expansion–instead of slowing down as a result of gravity. as expected. The earlier viewpoint proposed that, because the Universe is filled with matter–and the attractive force of gravity pulls all matter together–the expansion rate of the Cosmos had to be slowing down as time went by. But the discovery of the Universe’s accelerating expansion, based on HST observations of remote Type Ia supernovae, indicated that the Universe is really being pushed apart by a ghostly, unseen pressure filling all of Space.
Rushing To Nothingness
One potential explanation for the surprisingly rapid expansion of the Universe proposes that a new type of subatomic particle exists that may have altered the balance of energy in the ancient Universe–the so-called dark radiation. The dark radiation is a hypothetical particle that mediates interactions in the “dark” components of the Cosmos–dark energy and dark matter. Just as photons mediate electromagnetic interactions between atomic particles (baryonic matter) in the Standard Model, dark radiation would mediate interactions occurring between dark matter particles. In a way that is comparable to the way hypothetical dark matter particles would behave, the dark radiation would also not interact with Standard Model particles. Even though there has been no observation of such a species of particle, since the atomic sector accounts for many interacting species, it is reasonable to consider that the dark component of the Cosmos does so as well.
The dark matter is much more abundant than the “ordinary” atomic matter that composes our familiar world. The most recent measurements of the composition of our Cosmos indicate that 68% of it is dark energy, 27% of it is dark matter, and only 5% of it is “ordinary” atomic matter. “Ordinary” atomic matter accounts for all of the elements listed in the familiar Periodic Table–the rest of the Universe is “dark”.
The team of astronomers, led by Dr. Riess, made their most recent discovery of the faster-than-expected rate of Cosmic acceleration by refining their measurement of the expansion rate of the Universe–a value that is termed the Hubble constant. The astronomers measured the Hubble constant to an unprecedented accuracy, reducing the uncertainty to only 2.4 percent.
However, this more recent measurement creates a problem. This is because it is not in agreement with the expansion rate found by astronomers studying the moments shortly after the Big Bang. Measurements of the afterglow of the Big Bang–the Cosmic Microwave Background (CMB) radiation–derived from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) and the European Space Agency’s (ESA’s) Planck satellite mission show smaller predictions for the Hubble constant.
Comparing the Universe’s rate of expansion as calculated by WMAP and Planck (for the time after the Big Bang) and HST (for our Universe today), is like building a bridge, Dr. Riess explained in the June 2, 2016 STSI Press Release. “You start at two ends, and you expect to meet in the middle if all of your drawings are right and your measurements are right. But now the ends are not quite meeting in the middle and we want to know why,” he noted.
The newly refined calculation of the Hubble constant was made possible by obtaining very precise measurements of the distances to both distant and nearby galaxies using HST. These greatly improved distance measurements were made by strengthening and streamline the cosmic distance ladder, which astronomers use in order to measure the distances to galaxies accurately. The team of astronomers compared these measured distances with the expansion of Space as measured by the stretching of light from receding galaxies (redshift), and these two values were then used to calculate the new Hubble constant.
The team is continuing to make use of the HST with the goal of reducing the uncertainty of the Hubble constant even further, and the scientists aim to reach an uncertainty of only 1%. Telescopes that are currently available, such as the ESA’s Gaia satellite, and upcoming telescopes such as the NASA/ESA/CSA James Webb Space Telescope (JWST) and the European Extremely Large Telescope (E-ELT) could also help astronomers make improved measurements of the expansion rate of the Universe, resulting in a better understanding of our Cosmos and the laws that govern it.