Preface. The public has become more interested in science. In addition, science fiction films help to generate even more interest. Astrophysics has always been on people’s minds. This book summarizes the major ideas and discoveries.
‘The Universe is under no obligation to make sense to you.’ Neil Degrasse Tyson
The Greatest Story Ever Told. Almost 14 billion years ago, the Big Bang occurred and matter and energy expanded. Scientists have worked to try to combine the understanding of the general theory of relativity with quantum gravity. Max Planck is the father of quantum mechanics. Currently, we have no known laws of physics to predict the behavior of the universe over time. The Universe split into the electroweak and the strong nuclear forces. The electroweak forces split into the EM and weak nuclear forces. All this happened in less than a trillionth of a second. Photos can convert their energy into matter-antimatter particle pairs under intense energy. After the interaction of electroweak forces, the universe was a soup of quarks, leptons, antimatter siblings etc. The photon belongs to the boson family. The electron and neutrinos belong to leptons. There are 6 different types of quarks (up and down, strange and charmed, top and bottom). Quarks have fractional charges that come in thirds. Now, a millionth of a second has passed. New heavy particles called hadrons started to form. Now, protons and neutrons started to form. The LHC attempts to collide hadrons to create larger particles. Matter and anti-matter will annihilate one another, but there will one single hadron will survive. Electrons annihilate with positrons, and only 1 electron out of a billion survive. Eventually, elements like helium, deuterium and tritium are formed. Below 3000K, electrons stop combining with nuclei. For the first billion years, our universe expands and cools, while galaxies are formed. More than a hundred billion of them are formed, each containing billions of stars. Some stars explode. Our Sun is simply an undistinguished star. Wayward debris would orbit and form large bodies. These formed planets and the matter would start to cool. Earth is in a Goldilocks zone where oceans are in liquid forms. The early organisms on Earth were simple anaerobic bacteria, which excretes oxygen as its by-product. Ozone was also formed and these protected us from the Sun’s UV photons. We are thankful for the existence of carbon and the various simple/complex molecules. However, often, there are asteroids that hit Earth and cause havoc to our ecosystem. There was one which made dinosaurs extinct. Did our Universe just pop into existence from nothing? The Universe will continue to evolve.
We are stardust brought to life, then empowered by the Universe to figure itself out – and we have only just begun. – Neil Degrasse Tyson
On Earth as in the Heavens. Some of the religious people criticized Newton when he discovered gravity. The 19th century was a time of invention. The Sun contained a lot of similar elements as Earth. Helium was discovered too. Do the law of physics apply to the whole Universe? We sent out the Pioneer 10 and 11 and the Voyager 1 and 2 in the 1970s to look for outside life. All these spacecraft used gravity assists to escape the solar systems. It is not clear whether aliens would understand them. The Big G is the constant of gravitation. Our Universe is indeed very uniform. The speed of the light is one of the most famous constants. It is simply a law of physics. It is not time or location dependent. The conservations laws of mass and energy, linear and angular momentum and electric charge are all very important. Most of the gravity in the Universe is the form of dark matter, which is difficult to detect. Should Newton’s law of gravity be adjusted to account for dark matter? Einstein’s theory of relativity builds on Newton’s law of gravity as it applies to objects of extremely high mass like black holes. The Universality of physical laws make the cosmos very appealing.
Let There Be Light. The cosmos expanded rapidly after the Big Bang. Cosmic background radiation can still be detected. Photons can lose energy and form infrared photons, sliding down the spectrum. When something glows, it emits light in the full spectrum, but there will be a noticeable peak. Cosmic background radiation (CMR) was already predicted into the 1940s. In 1948, scientists predicted what the temperature of the cosmic background should be. Their answer was unerringly accurate. The first cosmic microwave background (CMB) was observed in 1964. They developed an antenna to detect microwaves. There was a constant leftover signal in their measurements. The signal came from every direction in the sky. When we out into space, we are looking back in time as light takes time to travel. Depending on the time that the photons that scattered off electrons, a different colour profile would be registered. The CMB will have spots that are slightly hotter or cooler. Analyzing the CMB will enable you to determine how quickly matter accumulated etc. Dark matter has gravity but does not interact with light. It forces the Universe to expand faster.
Between the Galaxies. There are over a hundred billion of them. How much void is there in space? Our galaxy is the Milky Way. The nearest one to us is over 180,000 light years away. The nearest one which is larger than ours is the Great Nebula in Andromeda, over 2 million light years away. Our detectors have enabled us to detect many more objects. Dwarf galaxies contain only up to a million stars, and they are hard to detect. They are also dim. Often, these dwarf galaxies may get eaten up by the main galaxy. Galaxies can collide and clusters will be formed. There is also the possibility of homeless stars, which are not in any galaxy. Supernovas have been found exploding away from their host galaxies. Supernovas are stars which have increased their luminosity over a billion fold. There are also intra-cluster gas that is so hot and can form stars. Quasars are super-luminous galaxy cores and are extremely distant. These are fascinating due to their huge mass. There are hydrogen clouds everywhere in the Universe. These light also passes through huge sources of gravity. Light that appears to us might have experienced curvature due to gravity etc. There are plenty of cosmic rays in the Universe, which are horrible, and move almost at the speed of light. There are plenty of particle collisions in intergalactic space.
Dark Matter. Gravity is difficult to understand. It has the ability to warp space-time at a distance. For example, light rays bend as they pass by a massive object. The bulk of the gravity in the Universe cannot be explained. Fritz Zwicky analysed this problem in 1937. He noticed some galaxies had a very high average velocity. However, it does not account for the speeds measured. Newton’s laws show that it is possible to achieve an orbital speed to escape the clutches of gravity. Other galaxy clusters also reveal this same problem. This supports the existence of ‘dark matter’ in the Universe. Cosmic dark matter seems to have at least 6 times the gravity of visible matter. It is not matter that happens to be under-luminous or non-luminous. It turns out that dark matter and nuclear fusion do not mix. Dark matter does not seem to do very much. Dark matter only comes into play for large bodies, like the motion of stars around the centre of the galaxy. It seems to be well spread across the Universe. The Universe is expanding, but gravity wants to make things coagulate. We do not know what dark matter is, just that we know that it is real. Skeptics tend to slam dark matter’s existence. Dark matter is real, as it has been deduced from its effects on visible matter. We are trying our best to detect the presence of dark matter. Right now, we just have to be happy with our understanding of dark matter.
Either dark matter particles must wait for us to discover and to control a new force or class of forces through which their particles interact, or else dark matter particles interact via normal forces, but with staggering weakness. – Neil Degrasse Tyson
What we know is that the matter we have come to love in the Universe – the stuff of stars, planets, and life – is only a light frosting on the cosmic cake, modest buoys afloat in a vast cosmic ocean of something that looks like nothing. – Neil Degrasse Tyson
Dark Energy. Einstein perfected the thought experiments in his head and was very successful. His theories withstood the test of time. The general theory of relativity (GR) was published in 1916. Everything in the Universe moves under the influence of gravity. In 2016, gravitational waves were discovered, as were predicted by Einstein 100 years ago. These are created from major events, like the collision of 2 black holes. They first arose almost 1.3 billion years ago, during a collision of 2 black holes. In the 16th century, it was a heliocentric model. However, in truth, the planets revolve the star in ellipses. There was a cosmological constant in his equations of gravity. In his equations, the universe neither expands nor contracts. The masses move along straight-line geodesics. The Universe is never static. The cosmological constant was a big blunder as it was proven that the Universe was still expanding. There are ways to measure the distance from a supernova, for example, from its decreasing luminosity over time. Hubble telescope shows that distant objects race away from us further than nearby ones. Dark energy was present, but scientists could not explain it. Dark energy comprises of 68% of all mass-energy, dark matter only 27% and regular matter only 5%. The predicted shape for the Universe would be a one-way saddle. There is simply not enough mass to explain the Universe’s expansion. This was when dark matter came about. Dark energy helped to raise the mass of ordinary energy and dark matter to the mass-energy density. Dark energy helped to reconcile the differences. These could be simply virtual particles in a vacuum, which can’t be measured. It turns out that there was a place for lambda in Einstein’s equations. Do we need an alternative to GR? The repulsive forces are present in the vacuum, and will grow ever more with increasing vacuum. The fabric of the Universe can carry material faster than the speed of light. In a trillion years, you might not know other galaxies existed. As a result of dark energy, future generations will not understand our Universe. What else should we be looking for?
GR regards gravity as the response of a mass to the local curvature of space and time caused by some other mass or field of energy. – Neil Degrasse Tyson
Matter tells space how to curve; space tells matter how to move. – John Archibald Wheeler
Keep a lookout for Part 2! 🙂