For many centuries, we arrogantly believed that he had found almost all the answers to the deepest questions. Scientists thought that Newtonian mechanics describes everything, until he discovered the wave nature of light. Physics thought when Maxwell unified the electromagnetism, it was the finish, but then came relativity and quantum mechanics. Many thought that the nature of matter is fully clear, when we found the proton, neutron and electron, but then stumbled on the high-energy particles. Just 25 the last five years of incredible discoveries changed our understanding of the Universe, and each of them promises a Grand revolution. We live in exciting times: we have the opportunity to look into the depths of the mysteries of all things.
The neutrino mass
When we started to calculate on paper the neutrinos coming from the Sun, we've got a number based on the synthesis that must occur inside. But when we started in fact to count neutrinos coming from the Sun, we saw only a third expected. Why? The answer came only recently, when a combination of measurements of solar and atmospheric neutrinos have shown that they can oscillate from one type to another. Because they have mass.
What does this mean for astrophysics. Neutrinos are the most common massive particle in the Universe: they are a billion times more than electrons. If they have mass, it follows that:
- they make up a fraction of dark matter
- get into galactic structure,
- perhaps form a strange astrophysical condition known as fermionic condensate
- can be associated with dark energy.
If neutrinos have mass, they can also be Majorana particles (rather than the more common particle Dirac) to provide a new type of nuclear decay. Also they can be superheavy fellow lefties, which could explain dark matter. Neutrinos also carry most of the energy in a supernova, are responsible for cooling of neutron stars affect the afterglow of the Big Bang (CMB) and are an essential part of modern cosmology and astrophysics.
The Accelerating Universe
If the universe begins with a hot Big Bang, it will have two important properties: the initial expansion rate and the initial density of matter/radiation/energy. If the density was too large, the universe would be reunited again; if too small, the universe is forever expanding. But in our Universe, the density and the expansion is not only perfectly balanced, but a tiny part of this energy comes in the form of dark energy, and that means that our universe began to rapidly expand after 8 billion years and since then continues in the same spirit.
What does this mean for astrophysics. For the first time in human history we got the opportunity to learn a little about the fate of the Universe. All objects that are not linked gravity, will eventually diverge, so everything beyond our local group will one day fly away. But what is the nature of dark energy? Is it really a cosmological constant? Whether it is connected with the quantum vacuum? Could it be a field whose strength is changing with time? Future missions like ESA's Euclid, WFIRST, NASA and the new 30-meter telescopes will allow more accurate measurements of dark energy will allow us to accurately describe how the universe is accelerating. In the end, if the acceleration is increasing, the universe will end in a Big Gap; if it falls, Great Compression. At stake is the fate of the entire Universe.
A generation ago we thought we were near other star systems have planets, but we had no evidence to prove this thesis. Currently, largely because of the mission of NASA "Kepler", we found and tested thousands of them. A solar system different from our own: some contain super-earths or mini-Neptune; some contain gas giants in the inner solar system; most contain worlds the size of Earth at the right distance from the tiny, dim, red dwarf stars, on the surface could be water in a liquid state. Still, a lot remains to be seen.
What does this mean for astrophysics. For the first time in history, we have found worlds that could be potential candidates for life. We are closer than ever before to detect signs of alien life in the Universe. Many of these worlds may someday be home to human colonies if we want to go this route. In the 21st century we will begin to explore these opportunities: to measure the atmosphere of these worlds and search for signs of life, send space probes at a substantial speed, to analyze their similarities with Earth on grounds such as oceans and continents, cloud cover, the oxygen content in the atmosphere, the seasons. Never in the history of the Universe was not more appropriate for this moment.
The Higgs Boson
The discovery of the Higgs particle in the early 2010s, completed, finally, the Standard model of elementary particles. The Higgs boson has a mass of about 126 GeV/C2, decays after 10-24 seconds and decays exactly with the predictions of the Standard model. The behavior of this particle there are no signs of the existence of new physics beyond the Standard model, and this is a big problem.
What does this mean for astrophysics. Why the mass of the Higgs is much smaller than the Planck mass? This question can be formulated differently: why is the gravitational force so much weaker than other forces? There are many possible solutions: supersymmetry, extra dimensions, the fundamental excitation (conformal solution), the Higgs as a composite particle (Technicolor), etc. But until these solutions no proof, and sufficiently thorough you were looking for?
On some level there must be something fundamentally new: new particles, new fields, new force, etc they will have astrophysical and cosmological consequences, and all these effects depend on the model. If particle physics, for example, on the TANK, will not provide any new hints, maybe astrophysics will provide. What happens when the most high energies and on very short distances? The big Bang and cosmic rays — bring us the highest energy than could our most powerful particle accelerator. Following the key to solving one of the biggest problems in physics can appear from space, not on Earth.
For 101 years it was the Holy Grail of astrophysics: the search for direct evidence of the biggest unproven predictions of Einstein. When Advanced LIGO reached out in 2015, she managed to reach the sensitivity required to register a ripple of space-time from a very high source of gravitational waves in the Universe: a twisting spiral, and merging black holes. Having two confirmed detections in the zone (and how many more will), brought Advanced LIGO gravitational-wave astronomy from science fiction to the reality.
What does this mean for astrophysics. All astronomy up to the present time was dependent on light, from gamma rays to the visible spectrum, microwave and radio frequencies. But the discovery of ripples in space-time is a completely new way of studying astrophysical phenomena in the Universe. Having the right detectors with the required sensitivity, we can see:
- the merger of neutron stars (and find out whether they are gamma-ray flash);
- the merger of white dwarfs (and associate them with the supernova type Ia);
- supermassive black holes devouring other mass;
- gravitational-wave signature of supernovae;
- signatures of pulsars;
- the residual gravitational wave signatures of the birth of the Universe, perhaps.
Now gravitational-wave astronomy is at the very start of development, it is hardly becoming a tested area. The next steps will be to increase the range of sensitivity and frequencies, as well as the comparison seen in the gravitational sky with optical sky. The future is coming.
And we are not talking about other great puzzles. There is dark matter: more than 80% of the mass of the Universe is completely invisible to light and ordinary (atomic) matter. There is a problem of baryogenesis: why our universe is full of matter and not antimatter, even though every reaction that we have ever seen, completely symmetric in matter and antimatter. There are paradoxes of black holes, cosmic inflation, have not yet created a successful quantum theory of gravity.
There is always the temptation to believe that our best days are behind you, and the most important and revolutionary discoveries have already been made. But if we want to understand the biggest question of all — where did the universe what it actually is appeared and where it will end — we still have a lot of work. With unprecedented size, range and sensitivity of the telescopes, we will be able to learn more than ever knew. Winning is never guaranteed, but every step that we take brings us one step closer to the place of destination. No matter where this journey takes us, the important thing is that it will be incredible.
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