The Limitless Universe
Up, down, sideways, and all around, there is a limit: the planet Earth. It can be the atmosphere, the oceans, the mountains or even the home. Resulting from this, one idea holds constant: the feeling of enclosure. Earth is the environment perfectly suited for mankind. Yet, when looking through those two glass pieces of a telescope, a terrifying truth unravels. The sense of enclosure is lost in an instant.
The Earth’s size compared to the solar system is small, compared to the Milky Way Galaxy it is almost nothing, but compared to the universe, well, the Earth appears to be nothing. The frightening reality is that our universe is 93 billion light years across (Siegel, “Redshift”), and this is an intimidating number! A light year is about 6 trillion miles, which puts these measurements at an incomprehensible level. However, contemporary life is marked by controversy, and this matter certainly falls under these circumstances. Therefore, this matter should not be simply put aside. The actual controversy derives from the fact that the universe was once, at the big bang, “infinitesimally small and infinitely dense” (Hawking 9).
How then, have scientists determined that our universe is so vast today and how do scientists know that the universe is still in a state of expansion? It is imperative to acknowledge the importance of this issue because cosmology is a front of the scientific world that is very minimally understood. The questions above are answerable through today’s scientific knowledge, but more remains unknown about the universe than known. For this reason, the controversy is sparked, but the truth remains: our universe is still expanding. To understand expansion today, it is necessary to have a theory of the beginning of the universe. The most common one is the Big Bang Theory.
As Stephen Hawking put it, “Under [the big bang] conditions all the laws of science, and therefore all ability to predict the future, would break down. If there were events earlier than this time, then they could not affect what happens at the present time. Their existence can be ignored because it would have no observational consequences” (9). So, the big bang would mark the origin of the universe for our circumstances. In the beginning, the universe was extremely hot and small.
It is impossible to tell what was happening at the time 0 seconds, but at the Planck time (10-43 seconds) the universe was at subatomic sizes and the temperature was around 1.832 degrees Fahrenheit. The inflation period ended at 10-35 seconds and this, almost instantaneous, time period marked the expansion of space at speeds faster than the speed of light (Wright). To make sense of this in easier numbers, the universe expanded about 200 trillion miles in one second! Matter formed and the great battle began. Each particle contained a tremendous amount of energy and was trying to fly away from every other particle and causing a stretch.
On the other side, gravity was “fighting to pull everything back together, and trying to re-collapse matter” (Siegel “The Last 100 Years”). Therefore, knowing that these were the two opposing sides, energy and gravity, it is perceived how the universe expanded. Energy had won the battle, the particles spread out, and an increasing amount of space came to be between them. Later on, gravity would win on a smaller scale in forming stars, planets, solar systems, and galaxies, but would never win on a large scale. The universe, thankfully, would not re-collapse on itself. It is evident that from the beginning of its time, the universe had to expand to reach its current size.
How exactly do astronomers know that there was an expansion and that there is still growth today? This is where the red-shift light spectrum and Cepheids come into play, which will be explained momentarily. First, the philosophy behind what is seen in space needs to be understood. Once again, Stephen Hawking provides a simple, understandable explanation: “The light that we see from distant galaxies left them millions of year ago, and in the case of the most distant object that we have seen, the light left some eight thousand million years ago. Thus, when we look at the universe, we are seeing it as it was in the past” (28). This explanation alone contributes to controversy itself: we are in the present but see light coming from the past.
However, returning to the main focus, scientists are able to tell that stars and galaxies are moving away from Earth through analyzing the wavelength of the light emitted from them. The light emitted from particles travels in waves and it is the distance between each wave that determines the color on an emission spectrum. When the distance is shorter the color on the emission spectrum will be more blue, and when the distance is longer the color will be more of a red. This also means that a stretched out wave will have a red-shift. There are three things that happen to light to change wavelength: gravitational red-shift, red-shift due to motion, and red-shift due to expanding space.
The last one is precisely why our universe is expanding. Space expanding creates longer wave lengths and that is why measuring light from distant objects gives the results of a red-shifted emission spectrum (Siegel, “Redshift”). Another helpful tool for measuring expansion has been NASA’s Spitzer Space Telescope. “Unlike [the] Hubble Space Telescope that views the cosmos in visible and short-wavelength infrared light, Spitzer took advantage of long-wavelength infrared light for its latest Hubble constant measurement, [universe expansion], of 74.3 kilometers per second per mega parsec, [74.
3 km / 1 sec / 3 million light years],” NASA has reported (Dunbar). The Spitzer Telescope has helped scientists observe Cepheids, variable stars that are an important part of the cosmic distance ladder. These Cepheids have known distances from the Earth and by measuring their speeds it is possible to calculate an expansion rate. The measurements are like that of a candle. The farther the candle, or Cepheid, the less apparent brightness it has.
The apparent brightness can be compared to known brightness and distance can be determined (Dunbar). In the 1990s two things were certain about the universe’s expansion. Either there would be enough energy density to stop the expansion or to slow it down as time progressed. However, towards the end of the decade this idea was going to change. With the new Hubble Space Telescope, in 1998, the occurrence of an accelerating expansion could be proved.
Yet another explanation for why the universe is growing arose: dark energy. NASA researchers explain that it is dark energy that it pushing the universe apart. Considered a property of space, it accounts for 68% of the universe, 27% is dark matter, and the remaining 5% is what is considered the normal matter (Erickson). Einstein predicted that empty space has the ability to possess energy, and this is the possible explanation today. As more space is created through expansion, more energy makes it expand faster and faster resulting in an acceleration. On the other hand, dark matter is “matter in galaxies, clusters, and possibly between clusters, that can not be observed directly but can be detected by its gravitational effect” (Hawking 200).
The understanding of the universe has come a long way: from a geocentric model to dark matter. It is important to note that today, even though things might be invisible, they are still considered as existing. Up until Nicholas Copernicus’s description,the universe was believed to be centered around Earth. Shortly, there came Galileo’s confirmation of Copernicus’s observation with the telescope and further mathematical proof from Johannes Kepler of elliptical orbits. However, these discoveries were made in the 16th and 17th century.
It was Harlow Shapley’s observation three centuries later that revealed that the Sun was not the center of the Milky Way Galaxy. Edwin Hubble then discovered other galaxies and astronomy progressed further (GaBany). This shows how important the current issue of an expanding universe is. People have discovered so much up until this point, but much more remains to be discovered. The universe is amazing, complex, confusing, and enormous. It is a popular topic for debate and is an issue being solved by scientists all over the world.
CNN’s latest report on how quickly the universe is expanding shows that there is public interest and the subject is gathering attention very quickly as new technology is being developed. In the report, David Schlegel of the Lawrence Berkley National Laboratory states, “When the universe was a few billion years old, it was getting bigger in every dimension by 1% for every 44 million years. Today, it takes 140 million years to get bigger by 1%” (Landau). This explains how big the universe must already be if it takes that long to expand by 1%. It also makes mankind ponder about its meaning and future. Hawking says the big bang occurred so many million years ago because it takes that long for intelligent beings to evolve (128).
Expansion and evolution occurred, but what lies in the future of the universe? Will an accelerated expansion continue or will gravity win someday, resulting in a big crunch? The possibilities are limitless!