Back in 2013, the European Space Agency released its first analysis of the data gathered by the Planck observatory. Between 2009 and 2013, this spacecraft observed the remnants of the radiation that filled the Universe immediately after the Big Bang – the Cosmic Microwave Background (CMB) – with the highest sensitivity of any mission to date and in multiple wavelengths.
In addition to largely confirming current theories on how the Universe evolved, Planck’s first map also revealed a number of temperature anomalies – like the CMB “Cold Spot” – that are difficult to explai. Unfortunately, with the latest analysis of the mission data, the Planck Collaboration team has found no new evidence for these anomalies, which means that astrophysicists are still short of an explanation.
Imagine if you will that your name would forever be associated with a groundbreaking scientific theory. Imagine also that your name would even be attached to a series of units, designed to performs measurements for complex equations. Now imagine that you were German who lived through two World Wars, won the Nobel Prize for physics, and outlived many of your children.
If you can do all that, then you might know what it was like to be Max Planck, the German physicist and founder of quantum theory. Much like Galileo, Newton, and Einstein, Max Planck is regarded as one of the most influential and groundbreaking scientists of his time, a man whose discoveries helped to revolutionized the field of physics. Ironic, considering that when he first embarked on his career, he was told there was nothing new to be discovered!
Early Life and Education:
Born in 1858 in Kiel, Germany, Planck was a child of intellectuals, his grandfather and great-grandfather both theology professors and his father a professor of law, and his uncle a judge. In 1867, his family moved to Munich, where Planck enrolled in the Maximilians gymnasium school. From an early age, Planck demonstrated an aptitude for mathematics, astronomy, mechanics, and music.
He graduated early, at the age of 17, and went on to study theoretical physics at the University of Munich. In 1877, he went on to Friedrich Wilhelms University in Berlin to study with physicists Hermann von Helmholtz. Helmholtz had a profound influence on Planck, who he became close friends with, and eventually Planck decided to adopt thermodynamics as his field of research.
In October 1878, he passed his qualifying exams and defended his dissertation in February of 1879 – titled “On the second law of thermodynamics”. In this work, he made the following statement, from which the modern Second Law of Thermodynamics is believed to be derived: “It is impossible to construct an engine which will work in a complete cycle, and produce no effect except the raising of a weight and cooling of a heat reservoir.”
For a time, Planck toiled away in relative anonymity because of his work with entropy (which was considered a dead field). However, he made several important discoveries in this time that would allow him to grow his reputation and gain a following. For instance, his Treatise on Thermodynamics, which was published in 1897, contained the seeds of ideas that would go on to become highly influential – i.e. black body radiation and special states of equilibrium.
With the completion of his thesis, Planck became an unpaid private lecturer at the Freidrich Wilhelms University in Munich and joined the local Physical Society. Although the academic community did not pay much attention to him, he continued his work on heat theory and came to independently discover the same theory of thermodynamics and entropy as Josiah Willard Gibbs – the American physicist who is credited with the discovery.
In 1885, the University of Kiel appointed Planck as an associate professor of theoretical physics, where he continued his studies in physical chemistry and heat systems. By 1889, he returned to Freidrich Wilhelms University in Berlin, becoming a full professor by 1892. He would remain in Berlin until his retired in January 1926, when he was succeeded by Erwin Schrodinger.
Black Body Radiation:
It was in 1894, when he was under a commission from the electric companies to develop better light bulbs, that Planck began working on the problem of black-body radiation. Physicists were already struggling to explain how the intensity of the electromagnetic radiation emitted by a perfect absorber (i.e. a black body) depended on the bodies temperature and the frequency of the radiation (i.e., the color of the light).
In time, he resolved this problem by suggesting that electromagnetic energy did not flow in a constant form but rather in discreet packets, i.e. quanta. This came to be known as the Planck postulate, which can be stated mathematically as E = hv – where E is energy, v is the frequency, and h is the Planck constant. This theory, which was not consistent with classical Newtonian mechanics, helped to trigger a revolution in science.
A deeply conservative scientists who was suspicious of the implications his theory raised, Planck indicated that he only came by his discovery reluctantly and hoped they would be proven wrong. However, the discovery of Planck’s constant would prove to have a revolutionary impact, causing scientists to break with classical physics, and leading to the creation of Planck units (length, time, mass, etc.).
By the turn of the century another influential scientist by the name of Albert Einstein made several discoveries that would prove Planck’s quantum theory to be correct. The first was his theory of photons (as part of his Special Theory of Relativity) which contradicted classical physics and the theory of electrodynamics that held that light was a wave that needed a medium to propagate.
The second was Einstein’s study of the anomalous behavior of specific bodies when heated at low temperatures, another example of a phenomenon which defied classical physics. Though Planck was one of the first to recognize the significance of Einstein’s special relativity, he initially rejected the idea that light could made up of discreet quanta of matter (in this case, photons).
However, in 1911, Planck and Walther Nernst (a colleague of Planck’s) organized a conference in Brussels known as the First Solvav Conference, the subject of which was the theory of radiation and quanta. Einstein attended, and was able to convince Planck of his theories regarding specific bodies during the course of the proceedings. The two became friends and colleagues; and in 1914, Planck created a professorship for Einstein at the University of Berlin.
During the 1920s, a new theory of quantum mechanics had emerged, which was known as the “Copenhagen interpretation“. This theory, which was largely devised by German physicists Neils Bohr and Werner Heisenberg, stated that quantum mechanics can only predict probabilities; and that in general, physical systems do not have definite properties prior to being measured.
This was rejected by Planck, however, who felt that wave mechanics would soon render quantum theory unnecessary. He was joined by his colleagues Erwin Schrodinger, Max von Laue, and Einstein – all of whom wanted to save classical mechanics from the “chaos” of quantum theory. However, time would prove that both interpretations were correct (and mathematically equivalent), giving rise to theories of particle-wave duality.
World War I and World War II:
In 1914, Planck joined in the nationalistic fervor that was sweeping Germany. While not an extreme nationalist, he was a signatory of the now-infamous “Manifesto of the Ninety-Three“, a manifesto which endorsed the war and justified Germany’s participation. However, by 1915, Planck revoked parts of the Manifesto, and by 1916, he became an outspoken opponent of Germany’s annexation of other territories.
After the war, Planck was considered to be the German authority on physics, being the dean of Berlin Universit, a member of the Prussian Academy of Sciences and the German Physical Society, and president of the Kaiser Wilhelm Society (KWS, now the Max Planck Society). During the turbulent years of the 1920s, Planck used his position to raise funds for scientific research, which was often in short supply.
The Nazi seizure of power in 1933 resulted in tremendous hardship, some of which Planck personally bore witness to. This included many of his Jewish friends and colleagues being expelled from their positions and humiliated, and a large exodus of Germans scientists and academics.
Planck attempted to persevere in these years and remain out of politics, but was forced to step in to defend colleagues when threatened. In 1936, he resigned his positions as head of the KWS due to his continued support of Jewish colleagues in the Society. In 1938, he resigned as president of the Prussian Academy of Sciences due to the Nazi Party assuming control of it.
Despite these evens and the hardships brought by the war and the Allied bombing campaign, Planck and his family remained in Germany. In 1945, Planck’s son Erwin was arrested due to the attempted assassination of Hitler in the July 20th plot, for which he was executed by the Gestapo. This event caused Planck to descend into a depression from which he did not recover before his death.
Death and Legacy:
Planck died on October 4th, 1947 in Gottingen, Germany at the age of 89. He was survived by his second wife, Marga von Hoesslin, and his youngest son Hermann. Though he had been forced to resign his key positions in his later years, and spent the last few years of his life haunted by the death of his eldest son, Planck left a remarkable legacy in his wake.
In recognition for his fundamental contribution to a new branch of physics he was awarded the Nobel Prize in Physics in 1918. He was also elected to the Foreign Membership of the Royal Society in 1926, being awarded the Society’s Copley Medal in 1928. In 1909, he was invited to become the Ernest Kempton Adams Lecturer in Theoretical Physics at Columbia University in New York City.
He was also greatly respected by his colleagues and contemporaries and distinguished himself by being an integral part of the three scientific organizations that dominated the German sciences- the Prussian Academy of Sciences, the Kaiser Wilhelm Society, and the German Physical Society. The German Physical Society also created the Max Planck Medal, the first of which was awarded into 1929 to both Planck and Einstein.
The Max Planck Society was also created in the city of Gottingen in 1948 to honor his life and his achievements. This society grew in the ensuing decades, eventually absorbing the Kaiser Wilhelm Society and all its institutions. Today, the Society is recognized as being a leader in science and technology research and the foremost research organization in Europe, with 33 Nobel Prizes awarded to its scientists.
In 2009, the European Space Agency (ESA) deployed the Planck spacecraft, a space observatory which mapped the Cosmic Microwave Background (CMB) at microwave and infra-red frequencies. Between 2009 and 2013, it provided the most accurate measurements to date on the average density of ordinary matter and dark matter in the Universe, and helped resolve several questions about the early Universe and cosmic evolution.
Planck shall forever be remembered as one of the most influential scientists of the 20th century. Alongside men like Einstein, Schrodinger, Bohr, and Heisenberg (most of whom were his friends and colleagues), he helped to redefine our notions of physics and the nature of the Universe.
Dark Matter has been something of a mystery ever since it was first proposed. In addition to trying to find some direct evidence of its existence, scientists have also spent the past few decades developing theoretical models to explain how it works. In recent years, the popular conception has been that Dark Matter is “cold”, and distributed in clumps throughout the Universe, an observation supported by the Planck mission data.
However, a new study produced by an international team of researchers paints a different picture. Using data from the Kilo Degree Survey (KiDS), these researchers studied how the light coming from millions of distant galaxies was affected by the gravitational influence of matter on the largest of scales. What they found was that Dark Matter appears to more smoothly distributed throughout space than previously thought.
For the past five years, the KiDS survey has been using the VLT Survey Telescope (VST) – the largest telescope at the ESO’s La Silla Paranal Observatory in Chile – to survey 1500 square degrees of the southern night sky. This volume of space has been monitored in four bands (UV, IR, green and red) using weak gravitational lensing and photometric redshift measurements.
Consistent with Einstein’s Theory of General Relativity, gravitational lensing involves studying how the gravitational field of a massive object will bend light. Meanwhile, redshift attempts to gauge the speed at which other galaxies are moving away from ours by measuring the extent to which their light is shifted towards the red end of the spectrum (i.e. its wavelength becomes longer the faster the source is moving away).
Gravitational lensing is especially useful when it comes to determining how the Universe came to be. Our current cosmological model, known as the Lambda Cold Dark Matter (Lambda CDM) model, states that Dark Energy is responsible for the late-time acceleration in the expansion of the Universe, and that Dark Matter is made up of massive particles that are responsible for cosmological structure formation.
Using a slight variation on this technique known as cosmic sheer, the research team studied light from distant galaxies to determine how it is warped by the presence of the largest structures in the Universe (such as superclusters and filaments). As Dr. Hendrik Hildebrandt – an astronomer from the Argelander Institute for Astronomy (AIfA) and the lead author of the paper – told Universe Today via email:
“Usually one thinks of one big mass like a galaxy cluster that causes this light deflection. But there is also matter all throughout the Universe. The light from distant galaxies gets continuously deflected by this so-called large-scale structure. This results in galaxies that are close on the sky to be “pointing” in the same direction. It’s a tiny effect but it can be measured with statistical methods from large samples of galaxies.When we have measured how strongly galaxies are “pointing” in the same direction we can infer from this the statistical properties of the large-scale structure, e.g. the mean matter density and how strongly the matter is clumped/clustered.”
Using this technique, the research team conducted an analysis of 450 square degrees of KiDS data, which corresponds to about 1% of the entire sky. Within this volume of space, the observed how the light coming from about 15 million galaxies interacted with all the matter that lies between them and Earth.
Combining the extremely sharp images obtained by VST with advanced computer software, the team was able to carry out one of the most precise measurements ever made of cosmic shear. Interestingly enough, the results were not consistent with those produced by the ESA’s Planck mission, which has been the most comprehensive mapper of the Universe to date.
The Planck mission has provided some wonderfully detailed and accurate information about the Cosmic Microwave Background (CMB). This has helped astronomers to map the early Universe, as well as develop theories of how matter was distributed during this period. As Hildebrandt explained:
“Planck measures many cosmological parameters with exquisite precision from the temperature fluctuations of the cosmic microwave background, i.e. physical processes that happened 400,000 years after the Big Bang. Two of those parameters are the mean matter density of the Universe and a measure of how strongly this matter is clumped. With cosmic shear, we also measure these two parameters but a much later cosmic times (a few billion years ago or ~10 billion years after the Big Bang), i.e. in our more recent past.”
However, Hildebrandt and his team found values for these parameters that were significantly lower than those found by Planck. Basically, their cosmic shear results suggest that there is less matter in the Universe and that it is less clustered than what the Planck results predicted. These results are likely to have an impact on cosmological studies and theoretical physics in the coming years.
As it stands, Dark Matter remains undetectable using standard methods. Like black holes, its existence can only be inferred from the observable gravitational effects it has on visible matter. In this case, its presence and fundamental nature are measured by how it has affected the evolution of the Universe over the past 13.8 billion years. But since the results appear to be conflicting, astronomers may now have to reconsider some of their previously held notions.
“There are several options: because we do not understand the dominant ingredients of the Universe (dark matter and dark energy) we can play with the properties of both,” said Hildebrandt. “For example, different forms of dark energy (more complex than the simplest possibility, which is Einstein’s “cosmological constant”) could explain our measurements. Another exciting possibility is that this is a sign that the laws of gravity on the scale of the Universe are different from General Relativity. All we can say for now is that something appears to be not quite right!”
Direction is something we humans are pretty accustomed to. Living in our friendly terrestrial environment, we are used to seeing things in term of up and down, left and right, forwards or backwards. And to us, our frame of reference is fixed and doesn’t change, unless we move or are in the process of moving. But when it comes to cosmology, things get a little more complicated.
For a long time now, cosmologists have held the belief that the universe is homogeneous and isotropic – i.e. fundamentally the same in all directions. In this sense, there is no such thing as “up” or “down” when it comes to space, only points of reference that are entirely relative. And thanks to a new study by researchers from the University College London, that view has been shown to be correct.
The team then analyzed it using a supercomputer to determine if there were any polarization patterns that would indicate if space has a “preferred direction” of expansion. The purpose of this test was to see if one of the basic assumptions that underlies the most widely-accepted cosmological model is in fact correct.
The first of these assumptions is that the Universe was created by the Big Bang, which is based on the discovery that the Universe is in a state of expansion, and the discovery of the Cosmic Microwave Background. The second assumption is that space is homogenous and istropic, meaning that there are no major differences in the distribution of matter over large scales.
This belief, which is also known as the Cosmological Principle, is based partly on the Copernican Principle (which states that Earth has no special place in the Universe) and Einstein’s Theory of Relativity – which demonstrated that the measurement of inertia in any system is relative to the observer.
This theory has always had its limitations, as matter is clearly not evenly distributed at smaller scales (i.e. star systems, galaxies, galaxy clusters, etc.). However, cosmologists have argued around this by saying that fluctuation on the small scale are due to quantum fluctuations that occurred in the early Universe, and that the large-scale structure is one of homogeneity.
For the sake of their study, the UCL research team – led by Daniela Saadeh and Stephen Feeney – looked at things a little differently. Instead of searching for imbalances in the microwave background, they looked for signs that space could have a preferred direction of expansion, and how these might imprint themselves on the CMB.
As Daniela Saadeh – a PhD student at UCL and the lead author on the paper – told Universe Today via email:
“We analyzed the temperature and polarization of the cosmic microwave background (CMB), a relic radiation from the Big Bang, using data from the Planck mission. We compared the real CMB against our predictions for what it would look like in an anisotropic universe. After this search, we concluded that there is no evidence for these patterns and that the assumption that the Universe is isotropic on large scales is a good one.”
Basically, their results showed that there is only a 1 in 121 000 chance that the Universe is anisotropic. In other words, the evidence indicates that the Universe has been expanding in all directions uniformly, thus removing any doubts about their being any actual sense of direction on the large-scale.
And in a way, this is a bit disappointing, since a Universe that is not homogenous and the same in all directions would lead to a set of solutions to Einstein’s field equations. By themselves, these equations do not impose any symmetries on space time, but the Standard Model (of which they are part) does accept homogeneity as a sort of given.
These solutions are known as the Bianchi models, which were proposed by Italian mathematician Luigi Bianchi in the late 19th century. These algebraic theories, which can be applied to three-dimensional spacetime, are obtained by being less restrictive, and thus allow for a Universe that is anisotropic.
On the other hand, the study performed by Saadeh, Feeney, and their colleagues has shown that one of the main assumptions that our current cosmological models rest on is indeed correct. In so doing, they have also provided a much-needed sense of closer to a long-term debate.
“In the last ten years there has been considerable discussion around whether there were signs of large-scale anisotropy lurking in the CMB,” said Saadeh. “If the Universe were anisotropic, we would need to revise many of our calculations about its history and content. Planck high-quality data came with a golden opportunity to perform this health check on the standard model of cosmology and the good news is that it is safe.”
So the next time you find yourself looking up at the night sky, remember… that’s a luxury you have only while you’re standing on Earth. Out there, its a whole ‘nother ballgame! So enjoy this thing we call “direction” when and where you can.
And be sure to check out this animation produced by the UCL team, which illustrates the Planck mission’s CMB data:
How was our Universe created? How did it come to be the seemingly infinite place we know of today? And what will become of it, ages from now? These are the questions that have been puzzling philosophers and scholars since the beginning the time, and led to some pretty wild and interesting theories. Today, the consensus among scientists, astronomers and cosmologists is that the Universe as we know it was created in a massive explosion that not only created the majority of matter, but the physical laws that govern our ever-expanding cosmos. This is known as The Big Bang Theory.
For almost a century, the term has been bandied about by scholars and non-scholars alike. This should come as no surprise, seeing as how it is the most accepted theory of our origins. But what exactly does it mean? How was our Universe conceived in a massive explosion, what proof is there of this, and what does the theory say about the long-term projections for our Universe?
The basics of the Big Bang theory are fairly simple. In short, the Big Bang hypothesis states that all of the current and past matter in the Universe came into existence at the same time, roughly 13.8 billion years ago. At this time, all matter was compacted into a very small ball with infinite density and intense heat called a Singularity. Suddenly, the Singularity began expanding, and the universe as we know it began.
From the vantage point of a window in an insane asylum, Vincent van Gogh painted one of the most noted and valued artistic works in human history. It was the summer of 1889. With his post-impressionist paint strokes, Starry Night depicts a night sky before sunrise that undulates, flows and is never settled. Scientific discoveries are revealing a Cosmos with such characteristics.
Since Vincent’s time, artists and scientists have taken their respective paths to convey and understand the natural world. The latest released images taken by the European Planck Space Telescope reveals new exquisite details of our Universe that begin to touch upon the paint strokes of the great master and at the same time looks back nearly to the beginning of time. Since Van Gogh – the passage of 125 years – scientists have constructed a progressively intricate and incredible description of the Universe.
The path from Van Gogh to the Planck Telescope imagery is indirect, an abstraction akin to the impressionism of van Gogh’s era. Impressionists in the 1800s showed us that the human mind could interpret and imagine the world beyond the limitations of our five senses. Furthermore, optics since the time of Galileo had begun to extend the capability of our senses.
Mathematics is perhaps the greatest form of abstraction of our vision of the World, the Cosmos. The path of science from the era of van Gogh began with his contemporary, James Clerk Maxwell who owes inspiration from the experimentalist Michael Faraday. The Maxwell equations mathematically define the nature of electricity and magnetism. Since Maxwell, electricity, magnetism and light have been intertwined. His equations are now a derivative of a more universal equation – the Standard Model of the Universe. The accompanying Universe Today article by Ramin Skibba describes in more detail the new findings by Planck Mission scientists and its impact on the Standard Model.
The work of Maxwell and experimentalists such as Faraday, Michelson and Morley built an overwhelming body of knowledge upon which Albert Einstein was able to write his papers of 1905, his miracle year (Annus mirabilis). His theories of the Universe have been interpreted, verified time and again and lead directly to the Universe studied by scientists employing the Planck Telescope.
In 1908, the German physicist Max Planck, for whom the ESA telescope is named, recognized the importance of Einstein’s work and finally invited him to Berlin and away from the obscurity of a patent office in Bern, Switzerland.
As Einstein spent a decade to complete his greatest work, the General Theory of Relativity, astronomers began to apply more powerful tools to their trade. Edwin Hubble, born in the year van Gogh painted Starry Night, began to observe the night sky with the most powerful telescope in the World, the Mt Wilson 100 inch Hooker Telescope. In the 1920s, Hubble discovered that the Milky Way was not the whole Universe but rather an island universe, one amongst billions of galaxies. His observations revealed that the Milky Way was a spiral galaxy of a form similar to neighboring galaxies, for example, M31, the Andromeda Galaxy.
Einstein’s equations and Picasso’s abstraction created another rush of discovery and expressionism that propel us for another 50 years. Their influence continues to impact our lives today.
Telescopes of Hubble’s era reached their peak with the Palomar 200 inch telescope, four times the light gathering power of Mount Wilson’s. Astronomy had to await the development of modern electronics. Improvements in photographic techniques would pale in comparison to what was to come.
The development of electronics was accelerated by the pressures placed upon opposing forces during World War II. Karl Jansky developed radio astronomy in the 1930s which benefited from research that followed during the war years. Jansky detected the radio signature of the Milky Way. As Maxwell and others imagined, astronomy began to expand beyond just visible light – into the infrared and radio waves. Discovery of the Cosmic Microwave Background (CMB) in 1964 by Arno Penzias and Robert Wilson is arguably the greatest discovery from observations in the radio wave (and microwave) region of the electromagnetic spectrum.
Analog electronics could augment photographic studies. Vacuum tubes led to photo-multiplier tubes that could count photons and measure more accurately the dynamics of stars and the spectral imagery of planets, nebulas and whole galaxies. Then in the 1947, three physicists at Bell Labs , John Bardeen, Walter Brattain, and William Shockley created the transistor that continues to transform the World today.
For astronomy and our image of the Universe, it meant more acute imagery of the Universe and imagery spanning across the whole electromagnetic spectrum. Infrared Astronomy developed slowly beginning in the 1800s but it was solid state electronics in the 1960s when it came of age. Microwave or Millimeter Radio Astronomy required a marriage of radio astronomy and solid state electronics. The first practical millimeter wave telescope began operations in 1980 at Kitt Peak Observatory.
With further improvements in solid state electronics and development of extremely accurate timing devices and development of low-temperature solid state electronics, astronomy has reached the present day. With modern rocketry, sensitive devices such as the Hubble and Planck Space Telescopes have been lofted into orbit and above the opaque atmosphere surrounding the Earth.
Astronomers and physicists now probe the Universe across the whole electromagnetic spectrum generating terabytes of data and abstractions of the raw data allow us to look out into the Universe with effectively a sixth sense, that which is given to us by 21st century technology. What a remarkable coincidence that the observations of our best telescopes peering through hundreds of thousands of light years, even more so, back 13.8 billion years to the beginning of time, reveal images of the Universe that are not unlike the brilliant and beautiful paintings of a human with a mind that gave him no choice but to see the world differently.
Now 125 years later, this sixth sense forces us to see the World in a similar light. Peer up into the sky and you can imagine the planetary systems revolving around nearly every star, swirling clouds of spiral galaxies, one even larger in the sky than our Moon, and waves of magnetic fields everywhere across the starry night.
The Universe is vast bubble of space and time, expanding in volume. Run the clock backward and you get to a point where everything was compacted into a microscopic singularity of incomprehensible density. In a fraction of a second, it began expanding in volume, and it’s still continuing to do so today.
So how old is the Universe? How long has it been expanding for? How do we know? For a good long while, Astronomers assumed the Earth, and therefore the Universe was timeless. That it had always been here, and always would be.
In the 18th century, geologists started to gather evidence that maybe the Earth hadn’t been around forever. Perhaps it was only millions or billions of years old. Maybe the Sun too, or even… the Universe. Maybe there was a time when there was nothing? Then, suddenly, pop… Universe.
It’s the science of thermodynamics that gave us our first insight. Over vast lengths of time, everything moves towards entropy, or maximum disorder. Just like a hot coffee cools down, all temperatures want to average out. And if the Universe was infinite in age, everything should be the same temperature. There should be no stars, planets, or us.
The brilliant Belgian priest and astronomer, George Lemaitre, proposed that the Universe must be either expanding or contracting. At some point, he theorized, the Universe would have been an infinitesimal point – he called it the primeval atom. And it was Edwin Hubble, in 1929 who observed that distant galaxies are moving away from us in all directions, confirming Lemaitre’s theories. Our Universe is clearly expanding.
Which means that if you run the clock backwards, and it was smaller in the distant past. And if you go back far enough, there’s a moment in time when the Universe began. Which means it has an age. The next challenge… figuring out the Universe’s birthdate.
In 1958, the astronomer Allan Sandage used the expansion rate of the Universe, otherwise known as the Hubble Constant, to calculate how long it had probably been expanding. He came up with a figure of approximately 20 billion years. A more accurate estimation for the age of the Universe came with the discovery of the Cosmic Microwave Background Radiation; the afterglow of the Big Bang that we see in every direction we look.
Approximately 380,000 years after the Big Bang, our Universe had cooled to the point that protons and electrons could come together to form hydrogen atoms. At this point, it was a balmy 3000 Kelvin. Using this and by observing the background radiation, and how far the wavelengths of light have been stretched out by the expansion, astronomers were able to calculate how long it has been expanding for.
Initial estimates put the age of the Universe between 13 and 14 billion years old. But recent missions, like NASA’s WMAP mission and the European Planck Observatory have fine tuned that estimate with incredible accuracy. We now know the Universe is 13.8242 billion years, plus or minus a few million years.
We don’t know where it came from, or what caused it to come into being, but we know exactly how our Universe is. That’s a good start.