Astrophysics for People in a Hurry by Neil Degrasse Tyson (Part 2)

The Cosmos on the Table. How did the Earth’s crust acquire the materials? The answer is astronomical. Only 3 elements were natural in the big bang process. The table is a cultural icon for humanity. The periodic table is very interesting indeed as each element has different characteristics. Hydrogen has only one proton in its nucleus, and is the lightest and simplest element. It also forms the core of Jupiter. In the sun, hydrogen collide to form helium. It is not so combustible in nature as hydrogen. It is the second most common element in our Universe. On average, it is about 10% of all atoms. It has 92% of hydrogen’s buoyancy, but without its explosive characteristics. Lithium has 3 protons in its nucleus, and was made in the big bang. Carbon is found in all kinds of molecules and is very abundant. This is the basis of chemistry and all diversity of life. Is it possible to have life forms based on silicon? Sodium is a common glowing gas in street lamps. Aluminium occupies 10% of the Earth’s crust. Titanium is twice as strong as aluminium. It is mostly used for military aircraft etc. The number of oxygen atoms exceed that of carbon. Excess oxygen might bond with titanium to form titanium oxide etc. Iron is one of the most important elements in our universe. It has 26 protons. Gallium is a soft metal that has a low melting point. Technetium is radioactive in nature and is artificial. The book features other interesting metals, like osmium and iridium. It is very dense indeed. Most atoms actually come from Greek names, like Phosphorus, Selenium etc. Ceres and Pallas are asteroids found in the asteroid belt. Uranium is a radioactive element named after Uranus. Neptunium is named after Neptune in 1940. Pluto was eventually dismissed a planet. Plutonium is named after Pluto and was used by the US to bomb Japan in WWII.

On Being Round. Most objects are spherical in nature. It is affected by surface tension. Due to gravity pulling at every area, the Earth is largely spherical in shape as the mountains are very low compared to how big the Earth is. Olympus Mons on Mars is 65,000 feet tall and 300 miles wide at its base. The weaker the gravity on an object, the taller the mountains can form. Non-spherical shapes on Phobos and Deimos form because of the low surface gravity. Stars are near perfect gaseous spheres. However, if it is too close to a massive star, some material can be stripped away. Our Milky Way galaxy is more flat, than spherical. It used to be a spherical, but collapsed at its poles as it spun faster and faster. The Milky Way is neither collapsing nor expanding. It is a gravitationally mature system. Saturn looks like a hamburger and is flattened because of its fast rotating speed. A pulsar is like squeezing the mass of a Sun into a ball the size of Manhattan. The pulsars are the most perfect spheres due to their huge mass and small space. Different galaxy clusters have different shapes and there are no fixed shapes. The entire observable Universe seems like a massive sphere as it is receding in every direction we look. However, as the Universe is expanding faster than the speed of light, there will be some galaxies whose light will not reach us and we will know nothing about them.

Invisible Light. Not all light is visible. There are 7 different colours to the visible spectrum. Different colours have different temperatures. Herschel was the first man to discover infra-red light. UV light was also discovered soon after. Low energy and low frequency to high energy and high frequency is radio waves, microwaves, infrared, ROYGBIV, ultraviolet, X-rays, and gamma rays. There are countless applications for such different spectra of light. Eventually, we built telescopes to detect parts of the EM spectrum. The Universe is actually sending light that our eyes cannot see and we would be dumb not to see it. Even long after supernovas explode, infrared red and radio waves get emitted. There needs to be different mirrors and detectors to detect all light bands. Radio telescopes are extremely large. China has built the world’s largest radio telescope, ranging over 30 football fields large. Humans also developed interferometers. We have 66 large antennas of ALMA to detect microwaves. There are high frequency, high-energy gamma rays with wavelengths measured in picometres. They are measured using a scintillator and we can pump out electrically charged particles that collide with gamma rays and produce light. There were frequent flashes of gamma rays near the Earth which could not be explained. Radio telescopes can detect gas among stars in the galaxies. The different types of light can tell us so much about star formations etc.

Between the Planets. There are plenty of chunky rocks, pebbles, charged particles in between planets. A lot of the small meteors burn up in our Earth’s atmosphere. This helps to protect Earth from such impact. Long ago, a lot of debris hit the Earth, causing our hot and molten core. A lot of junk led to the formation of the moon. Many of the other planets like Mercury, Mars received bombardments, as per the craters in the ground. When a meteor strikes, the impact can cause rocks to emerge up as well. Some of the Moon’s rocks also hit our surface. The asteroid belt is between Mars and Jupiter. Some of them are really large and might destabilize the Earth if it hits the Earth. The Kuiper belt is located after Neptune. Halley’s comet is from this belt. There are some comets between our solar system and the nearest star. These are known as the Oort cloud. The magnetic force on Jupiter is simply tremendous. Some of the planets’ moons are really interesting to study. Io is tidally locked and interacts with other moons. It is the most volcanically active place in our solar system. Pluto and Charon have tidally locked each other. Moons are named after Greek personalities. The sun releases solar wind, which is a release of material from its surface at a rate of a million tons per second. These causes the beautiful aurora on Earth. Jupiter is our big gravitational shield from comets as it helps to defect them away. We also exploit their gravitational field when we launch probes to space.

Exoplanet Earth. There are plenty of beautiful things on Earth. You could probably observe many structures from up in space. Natural scenery and hurricanes, volcanic eruptions should be visible. Earth is just a pale blue dot from Neptune, 3 billion miles away. Earth appears blue due to two-third being covered by water. Once there is liquid water, there will be a stable pressure and temperature. Aliens can notice our weather patterns and even see our polar ice caps. The nearest star is Alpha Centauri, nearly 4 light years away and often visible at night. As Earth is not bright, it will be hard to detect via visible light. However, if you notice a star jiggle, it could mean that an object/planet has just orbited around it. The Kepler telescope is meant to detect other Earth like planets. It detects stars whose total brightness drops slightly and at regular intervals. From this, it can detect multi-planet star systems. Aliens might be able to detect the multiple radio waves that we emit. Light, throughout the Universe, behaves in the same way. Hence, it can be detected through a spectrometer. Methane is a molecule which indicates life stock. The alien’s best bet would be to detect oxygen in our atmosphere. Oxygen bonds readily with other atoms. We have discovered more than 3000 exoplanets.

Latest estimates, extrapolating from the current catalogs, suggest as many as 40 billion Earth-like planets in the Milky Way alone. Those are the planets our descendants might want to visit someday, by choice, if not by necessity. – Neil Degrasse Tyson

Reflections on the Cosmic Perspective. Learn to enjoy the pleasure of intellectual pursuits. Despite all the cosmic wonder, there are still horrible things happening on Earth. Some people are also selfish and do not help others. The world is big, but so should our hearts and minds be. Some adults feel that the world revolves around them and are very self-centered. People hold an expanded view of the cosmos. Humans experience a sense of smallness and insignificance after watching a show where they see Earth in the grand scheme of the Universe. However, I feel large and important. Human beings are not the most important thing in the Universe. Powerful forces make us susceptible. We are all part of this stream of human consciousness. The air and water you consume might have come from ages ago. We are largely made from the same atoms as when the Universe was formed. They are hydrogen, oxygen, carbon and nitrogen. We have to remain open to the concept of multiverses. The cosmos are humble, spiritual etc. They allow us to be more open to knowledge and to accept new ideas. There is no air in space, but yet we can admire its beauty from afar. Astronomy is good because it makes us more curious, and hungrier for knowledge.

Of all the sciences cultivated by mankind, Astronomy is acknowledged to be, and undoubtedly is, the most sublime, the most interesting, and the most useful. For, by knowledge derived from this science, not only the bulk of the Earth is discovered…; but our very faculties are enlarged with the grandeur of the ideas it conveys, our minds exalted above low contracted prejudices. – James Ferguson

Time to get cosmic. There are more stars in the Universe than grains of sand on any beach, more stars than seconds have passed since Earth formed, more stars than words and sounds ever uttered by all the humans who ever lived. – Neil Degrasse Tyson

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The End!

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