Naturvitenskap er spennende. Ikke minst i disse tider hvor man innen fysikk gjør stadig nye oppdagelser innen kvantemekanikk, kosmologi og ikke minst forsøk på å bekrefte Einsteins betraktninger. Ofte leser jeg et fysikk kapittel eller hører en podcast om fysikk. Informasjon jeg synes er interessant vil jeg samle i denne posten.
Dark matter
Some of the first inklings astronomers had that there might be more mass in the universe than just the stuff we can see came in the 1960s and 1970s. Vera Rubin, a young astronomer at the Department of Terrestrial Magnetism at the Carnegie Institution of Washington, observed the speeds of stars at various locations in galaxies. Simple Newtonian physics predicted that stars on the outskirts of a galaxy would orbit more slowly than stars at the center. Yet Rubin’s observations found no drop-off at all in the stars’ velocities further out in a galaxy. Instead, she found that all stars in a galaxy seem to circle the center at roughly the same speed. But research by other astronomers confirmed the odd finding. Ultimately, based on observations and computer models, scientists concluded that there must be much more matter in galaxies than what’s obvious to us. If the stars and gas that we can see inside galaxies are only a small portion of their total mass, then the velocities make sense.
NASA. What Is Dark Matter? By fitting a theoretical model of the composition of the universe to the combined set of cosmological observations, scientists have come up with about 68% dark energy, 27% dark matter, 5% normal matter. What is dark matter? We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the universe to make up the 27% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter.
Livescience. Light 14 billion-year-old from the turbulent aftermath of the Big Bang, so produced just 380,000 years after the Big Bang, was warped by the universe’s dark matter exactly the way Einstein predicted it would be. In his theory of general relativity.
Dark energy
It all started in the mid-1990s, when two teams of researchers were trying to figure out how fast the universe was expanding, in order to predict whether it would keep spreading out forever, or if it would eventually crumple back in on itself in a “Big Crunch.” To do this, scientists used special tricks to determine the distances of many exploded stars, called supernovas, throughout the universe. They then measured their velocities to determine how fast they were moving away from us. When we view very distant stars, we are viewing an earlier time in the history of the universe, because those stars’ light has taken millions and billions of light-years to travel to us. Thus, looking at the speeds of stars at various distances tells us how fast the universe was expanding at various points in its lifetime. Astronomers predicted two possibilities: either the universe has been expanding at roughly the same rate throughout time, or that the universe has been slowing in its expansion as it gets older. Shockingly, the researchers observed neither possibility. Instead, the universe appeared to be accelerating in its expansion. That fact could not be explained based on what we knew of the universe at that time. All the gravity of all the mass in the cosmos should have been pulling the universe back inward, just as gravity pulls a ball back down to Earth after it’s been thrown into the air. “There’s some other force out there or something on a cosmic scale that is counteracting the force of gravity,” writer Richard Panek explained. “People didn’t believe this at first because it’s such a weird result.”
Elektronkonfigurasjon fysikk møter kjemi
In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon atom is 1s2 2s2 2p6, meaning that the 1s, 2s and 2p subshells are occupied by 2, 2 and 6 electrons respectively. pi bond.
Double slit experiment quantum mechanics
Lys sendt gjennom en spalte eller dobbelspalte. Fermilab youtube Don Lincoln. Viser at lys (og elektroner) både kan oppføre seg som partikler (fotoner) og bølger. Eller kanskje er lys partikler styrt av en sannsynlighetsbølge. Målinger gjør at sannsynlighetsbølgen kollapser. Hvorfor dette skjer er ikke klart.
Double slit experiment fourth dimension
Double slit experiment recreated in fourth dimension. Ved å sende lyset i meget korte pulser (femtosekunder) oppsto en ny type interferensfenomen. Instead of interference patterns showing up as bands of bright and dark, they showed up as changes in the frequency (colour) of the beams of light.
Quantum eraser experiment
Et eksperiment som viser at fortiden kan endres. Kanskje det er en effekt av quantum entanglement. How the Quantum Eraser Rewrites the Past.
Quantum entanglement og Clauser-Freedman
nytimes Quantum Trickery: Testing Einstein’s Strangest Theory. Einstein called the synchronized movement of particles “spooky action at a distance”. He described it as a result of quantum physics and saw it as evidence quantum physics theory was wrong or incomplete. Today it is called Entanglement. The first experiments to confirm Einsteins theory were performed in the 1970’s by John Clauser and Stuart Freedman at the University of California, Berkeley. (Alain Aspect and colleagues at the University of Orsay in France carried out more refined and comprehensive versions of these experiments in 1982.)
The Freedman–Clauser experiment was the first test of the CHSH inequality. It has now been tested experimentally hundreds of times at laboratories around the world to confirm that quantum entanglement is real. Clauser’s work earned him the 2010 Wolf Prize in physics.Sep 20, 2022.
Kan ikke brukes til å sende meldinger: The effects of spooky action, or entanglement, as Schrödinger called it, only show up in retrospect when the two participants in a Bell-type experiment compare notes. Beforehand, neither has seen any violation from normal. Each sees the results of his measurements of, say, whether a spinning particle is pointing up or down, as random.
Two particles, once linked quantum mechanically, or entangled, can be separated by large distances, even the diameter of the universe, and still “know” what happens to one another. The experiment involved the decay of excited calcium atoms to produce two photons of light, which, because of the law of conservation of the angular momentum, must have opposite polarizations to make the net angular momentum zero. Since the photons are emitted simultaneously, they are entangled. According to quantum mechanics, measuring the polarization of one should tell you the polarization of the other, even though, in this experiment, the measurements were taken 10 feet apart. If quantum mechanics is incomplete, the correlations between the polarization measurements should be within limits set by Bell’s inequality.
Relativitet
This teenager Won $250,000 for Her Short Video Explaining the Theory of Relativity. The winning video was called Relativity & The Equivalence of Reference Frames.
Sean Carroll og Brian Greene youtube
Veldig bra youtube kanal Sean Carrol som tar opp The Biggest Ideas in the Universe. Eksempelvis tid, time. Og gravitasjon. Sean Michael Carroll (born October 5, 1966) is an American theoretical physicist and philosopher who specializes in quantum mechanics, cosmology, and philosophy of science. Kaluza–Klein theory is a classical unified field theory of gravitation and electromagnetism. Gunnar Nordström had an earlier, similar idea. Nordström was a Finnish theoretical physicist best remembered for his theory of gravitation, which was an early competitor of general relativity. Nordström is often designated by modern writers as The Einstein of Finland due to his novel work in similar fields with similar methods to Einstein.
Brian Greene har tilsvarende youtube videoer. En ting som er litt spesielt å notere med dagens teoretiske fysikerne er at de i veldig stor grad lener seg på Einstein. Når noe skal forklares refererer de enten til Einstein eller så finnes ingen god teori for et fenomen men en mengde halvgode konkurerende teorier.
Max Planck grunnla kvantefysikk 1900
Gustav Kirchhoff discovered in the mid-19th century that “heat rays are … the same in nature as light rays, in fact a particular type. Invisible heat rays are only different from light rays in their period of oscillation or wavelength.”
A black body not only emits radiation at a particular wavelength, but over the entire wavelength spectrum. The distribution of radiation over the spectrum depends entirely on temperature.
En black-body konstrueres som en hul kule (cavity) som er helt sort innvendig. Kulen varmes opp. Man har et lite hull i kulen og studerer strålingen som kommer ut av hullet.
The challenge that faced experimental physicists was to create, as far as possible, an ideal black body and to measure its spectrum at various temperatures.
On Oct. 19, 1900, Planck announced to the Berlin Physical Society that he had obtained a formula that nicely fitted the results of the experiments. E=hf.
In working to explain the physics behind his formula, Planck was led to the radical assumption that atoms do not give radiation away continuously, but in discrete multiples of a fundamental amount. Atoms deal with energy as we deal with money, always in multiples of a smallest quantity. One dollar equals 100 cents, and ten dollars equals 1,000 cents. All financial transactions in the U.S. are in multiples of a cent. For the black-body radiation with its many waves of different frequencies, each frequency released relates to a minimum proportional “cent” of energy. The higher the frequency of the radiation, the larger its “cent.” The mathematical formula for this “minimum cent” of energy reads E = hf, where E is the energy, f is the frequency of the radiation, and h is Planck’s constant.
Lev Landau lærebøker og Leonard Susskind
Oppdatering 22. april 2023. Den russiske fysikeren Lev Landau med medforfatter skrev en bokserie som dekker hele fysikkfeltet. Bøkene finnes fortsatt. Jeg kjøpte den første i serien igår om Mekanikk på ebay. Som papirbok, ikke ebok, mye bedre og sunnere å lese papirbøker. Jeg leste de første sidene online. Boken bygges opp gjennom resonnementer og ikke bare gjennom gjengivelse av fakta. Den inneholder endel matematikk men ikke for avansert for en som meg. Gleder meg til den kommer i posten. Boken er oversatt til engelsk. Blir spennende å få et innblikk i russisk tankegang på dette området. Etterhvert ønsker jeg å lære meg russisk og lese på originalspråket.
Leonard Susskind er en nålevende amerikansk fysiker. Han har laget et online program bygget på Lev Landau malen.
The Theoretical Minimum is a series of Stanford Continuing Studies courses taught by world renowned physicist Leonard Susskind. This website presents those courses. He is writing a series of companion books to the courses also called The Theorectical Minimum. These courses collectively teach everything required to gain a basic understanding of each area of modern physics including all of the fundamental mathematics. The term Theoretical Minimum originated with renowned Russian physicist Lev Landau. Landau developed a comprehensive exam called the “Theoretical Minimum” which students were expected to pass before admission to the school. The exam covered all aspects of theoretical physics, and between 1934 and 1961 only 43 candidates passed.
Stephen Hawking
nytimes A Black Hole Mystery Wrapped in a Firewall Paradox.
Gravitasjon
There is an enormous gravity hole in the middle of the Indian Ocean. Here sea levels are about 300 feet lower than nearby areas. Local gravity is slightly lower.
