- 3178 - PHYSICS - don’t understand the extremes? This makes quantum physics all about “probabilities“. We can only say which state an object is “most likely” to be in once we look. These odds are encapsulated into a mathematical entity called the “wave function“. Making an observation is said to ‘collapse’ the wave function, destroying the superposition and forcing the object into just one of its many possible states.
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- Albert Einstein won a Nobel Prize for proving that energy is quantized. Energy only comes in multiples of the same "quanta", hence the name quantum physics.
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- The quanta here is the “Planck constant“, named after Max Planck, the godfather of quantum physics. He was trying to solve a problem with our understanding of hot objects like the sun. Our best theories couldn’t match the observations of the energy they kick out. By proposing that energy is quantized, he was able to bring theory neatly into line with experiment.
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- A solar sail in space can exert light pressure like the wind on Earth. J. J. Thomson won the Nobel Prize in 1906 for his discovery that electrons are particles. Yet his son George won the Nobel Prize in 1937 for showing that electrons are waves. Who was right?
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- The answer is both of them. This so-called wave-particle duality is a cornerstone of quantum physics. It applies to light as well as electrons. Sometimes it pays to think about light as an electromagnetic wave, but at other times it’s more useful to picture it in the form of particles called photons.
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- A telescope can focus light waves from distant stars, and also acts as a giant light bucket for collecting photons. It also means that light can exert pressure as photons slam into an object. This is something we already use to propel spacecraft with solar sails, and it may be possible to exploit it in order to maneuver a dangerous asteroid off a collision course with Earth.
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- Objects can be in two places at once. Wave-particle duality is an example of “superposition“. A quantum object can exist in multiple states at once. An electron is both ‘here’ and ‘there’ simultaneously. It’s only once we do an experiment to find out where it is that it settles down into one or the other.
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- This makes quantum physics all about “probabilities“. We can only say which state an object is “most likely” to be in once we look. These odds are encapsulated into a mathematical entity called the “wave function“. Making an observation is said to ‘collapse’ the wave function, destroying the superposition and forcing the object into just one of its many possible states.
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- The idea that observation collapses the wave function and forces a quantum ‘choice’ is known as the “Copenhagen interpretation” of quantum physics. However, it’s not the only option on the table.
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- As far as a quantum particle is concerned, there’s just one very weird reality consisting of many tangled-up layers. As we zoom out towards the larger scales that we experience day to day, those layers untangle into the worlds of the many worlds theory. Physicists call this process “decoherous“.
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- The spectra of stars can tell us what elements they contain, giving clues to their age and other characteristics. Danish physicist Niels Bohr showed us that the orbits of electrons inside atoms are also quantized. They come in predetermined sizes called energy levels.
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- When an electron drops from a higher energy level to a lower energy level, it spits out a photon with an energy equal to the size of the gap. Equally, an electron can absorb a particle of light and use its energy to leap up to a higher energy level.
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- We know what stars are made of because when we break up their light into a rainbow-like spectrum, we see colors that are missing. Different chemical elements have different energy level spacings, so we can work out the constituents of the sun and other stars from the precise colors that are absent.
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- Quantum tunneling is the finite possibility that a particle can break through an energy barrier. The sun makes its energy through a process called nuclear fusion. It involves two protons, the positively charged particles in an atom sticking together. However, their identical charges make them repel each other, just like two north poles of a magnet. Physicists call this the “Coulomb barrier“, and it’s like a wall between the two protons.
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- Think of protons as particles and they just collide with the wall and move apart: No fusion, no sunlight. Yet think of them as waves, and it’s a different story. When the wave’s crest reaches the wall, the leading edge has already made it through.
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- The wave’s height represents where the proton is most likely to be. So although it is unlikely to be where the leading edge is, it is there sometimes. It’s as if the proton has burrowed through the barrier, and fusion occurs. Physicists call this effect "quantum tunneling".
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- Eventually fusion in the sun will stop and our star will die. Gravity will win and the sun will collapse, but not indefinitely. The smaller it gets, the more material is crammed together. Eventually a rule of quantum physics called the Pauli exclusion principle comes into play.
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- This Pauli principle says that it is forbidden for certain kinds of particles, such as electrons, to exist in the “same quantum state“. As gravity tries to do just that, it encounters a resistance called “degeneracy pressure” The collapse stops, and a new Earth-sized object called a white dwarf forms.
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- Degeneracy pressure can only put up so much resistance, however. If a white dwarf grows and approaches a mass equal to 1.4 suns, it triggers a wave of fusion that blasts it to bits. Astronomers call this explosion a Type Ia supernova, and it’s bright enough to outshine an entire galaxy.
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- A quantum rule called the Heisenberg uncertainty principle says that it’s impossible to perfectly know two properties of a system simultaneously. The more accurately you know one, the less precisely you know the other. This applies to momentum and position, and separately to energy and time.
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- This process leads us to virtual particles. If enough energy is ‘borrowed’ from nature then a pair of particles can fleetingly pop into existence, before rapidly disappearing..
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- Stephen Hawking imagined this process occurring at the boundary of a blackhole, where one particle escapes (as Hawking radiation), but the other is swallowed. Over time the blackhole slowly evaporates.
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- Starting out as a singularity, the universe has been expanding for 13.8 billion years.
This is our best theory of the universe’s origin is the Big Bang. Yet it was modified in the 1980s to include another theory called “inflation“.
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- In the first trillionth of a trillionth of a trillionth of a second, the cosmos ballooned from smaller than an atom to about the size of a grapefruit. That’s a whopping 10^78 times bigger. Inflating a red blood cell by the same amount would make it larger than the entire observable universe today.
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- As it was initially smaller than an atom, the infant universe would have been dominated by quantum fluctuations linked to the Heisenberg uncertainty principle. Inflation caused the universe to grow rapidly before these fluctuations had a chance to fade away.
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- This concentrated energy into some areas rather than others acting as seeds around which material could gather to form the clusters of galaxies we observe now.
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- As well as helping to prove that light is quantum, Einstein argued in favor of another effect that he dubbed ‘spooky action at distance’. Today we know that this ‘quantum entanglement’ is real, but we still don’t fully understand what’s going on.
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- We bring two particles together in such a way that their quantum states are inexorably bound, or entangled. One is in state A, and the other in state B. The “Pauli exclusion principle” says that they can’t both be in the same state.
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- If we change one, the other instantly changes to compensate. This happens even if we separate the two particles from each other on opposite sides of the universe. It’s as if information about the change we’ve made has traveled between them faster than the speed of light, something Einstein said was impossible
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--------------------------- Other reviews that are just as confusing?
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- 3131 - PHYSICS - only six fundamental particles? Really! Only six fundamental particles make up our whole world? In our everyday world, when you get down to the fundamentals, everything we see or touch is made of only 6 fundamental particles. That is amazing.
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- 3051 - PHYSICS - mysteries to be solved? - We are all students if we are still learning, Right? Well mysteries in science today are solutions for students in the future. The science I refer to in this review is the broad look at astronomy and physics.
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- 2911 - PHYSICS - unsolved mysteries? 1900, the British physicist Lord Kelvin is said to have pronounced: "There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.” There are many mysteries we need to learn before we get hit by the next asteroid. Our Universe is full of surprises:
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- 938 Universal Constants. What are the natural constants and how do they shape our Universe.
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- 2895 - PHYSICS - mysteries we have yet to solve? We are all students if we are still learning, Right? Well mysteries in science today are solutions for students in the future. The science I refer to in this review is the broad look at astronomy and physics. Astronomy as the science of the very big. Physics as the science of the very small.
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- 2882 - Physics the Way I Learned It.
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- 2386 - The Science of Physics. How all of physics can be narrowed down to two simple topics.
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- 2004 - The Trouble with Physics. How string theory and academics have lead physics astray.
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- 531 Joseph Henry, an American teacher.
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- 532 Robert Millican, a Physics teacher.
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- 524 Physics keeps getting simpler. If you ask a stupid question you feel stupid. If you don’t ask a stupid question you remain stupid.
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- 2220 - The laws of motion.
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- May 31, 2021 PHYSICS - don’t undersrand the extremes? 3178
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