Cosmology Final

how many dimensions is the universe

4

what is the absolute in spacetime

separation

what things are not absolute in spacetime

time and space

what are time and space dependent on

relative velocities of observers

what are the three possibilities for the spacetime geometry of the universe

spherical, aka positive curvature and closed universe

euclidian, aka flat and no curvature

hyperbolic, aka open with negative curvature

what are the two postulates of general relativity

principle of equivalence, aka the effects of gravity are indistinguishable from acceleration, and general covariance, aka laws of physics are the same for all observers regardless of where they are located

what is the experimental evidence for general relativity

Experimental evidence for general relativity includes the bending of light around the sun observed during the 1919 solar eclipse, matching Einstein’s predictions. The precise orbit of Mercury shows a precession that Newtonian physics can't fully explain but general relativity does. More recently, gravitational waves detected by LIGO in 2015 confirmed another key prediction of the theory.

what is the cosmological principle

the universe is isotropic, looks the same in every direction, and the universe is homogeneous, looks the same at every point

under what conditions does the cosmological principle apply

large scale

time dependent solutions of the GR equations allow a universe in which…

spacetime is expanding

because spacetime is expanding

why is the universe expanding

is the galaxy expanding

no

what is a black hole

a region in space where gravity is so strong that not even light can escape it. it forms when a massive star collapses under its own gravity after running out of fuel

under what conditions can a black hole be created

a star with enough mass, about twenty times mass of sun, collapses at the end of its life

how can a black hole be observed

by looking at how they affect nearby objects, such as stars being pulled toward them or light bending around them. we can also detect x rays and other radiation emitted as matter falls into the black hole.

how do you measure the cosmic elemental abundance

each element has unique orbital structure that leads to distinct emission and absorption lines. if you look at light from a nebulae, you see individual emission lines that tell you its composition. this is called spectroscopy

why is the cosmic elemental abundance important

it is a cosmic fingerprint, it helps us understand how stars form, origins of universe, and structures of planets and galaxies

what is the value of elemental abundance of hydrogen, helium, and everything else

90% hydrogen, 9% helium, and 1% everything else

how does temp and energy density of the universe behave during expansion and contraction

as the universe expands, temp and energy density decrease, and vice versa. When space stretches, photons lose energy and cool down

what happens to an atom and a nucleus if you heat it enough

if you heat an atom enough, eventually the electron and nucleus will break free, and the nucleus will break into protons and neutrons. When the electron is stripped, that means the atom is ionized.

when did particle physics, nuclear physics, and atomic physics each dominate the universe, respectively

<1s, 1s to 300000 years, 300000 years and on

what is alpha radiation

low energy helium nuclei are ejected from an unstable atomic nuclei during radioactive decay. it has low penetration power and can be stopped by paper or skin, but is damaging if ingested

what is beta radiation

medium energy electrons are emitted during radioactive decay. it has moderate penetration power and can be stopped by aluminum or plastic, and can cause damage if absorbed

what is gamma radiation

high energy photons are emitted from an unstable nucleus after radioactive decay, it is highly penetrative and can cause serious biological damage, most harmful

which radiation is most dangerous to humans

gamma

explain the model of the atomic

most of the atom is empty space

what is the size of an atom

ten to neg ten m

what is the size of a nucleus

ten to neg fifteen m

how does a cloud chamber work to detect radiation

when vapor condenses along the tracks, these tracks can be bent using magnetic fields, and then energy can be measured that way

how does a geiger counter work to detect radiation

a tube is filled with gas, and when radiation enters the tube, the gas is ionized and pulses. the counter detects these pulses and counts them, thus providing a measure of radiation intensity

what is the form of the electric force law

force between 2 objects is proportional to product of their charges, and inverse to square of distance. Force is equal to couloumbs constant times the product of the charges divided by the distance squared

what is an isotope

a variant of an element that has the same number of protons but a different number of neutrons, resulting in a different atomic mass, or think of it as same atomic number and different neutrons, because atomic number, electrons, and protons should all be equal, can be formed by bombarding an element with neutrons

how do you interpret the symbol from an isotope, specifically determining neutrons, protons, and electrons

protons are equal to the atomic number, and the electrons are equal to the number of protons. The number of neutrons is found by subtracting the atomic number from the mass number. Mass number will be written on top of atomic number

define half life

the time it takes for half of the atoms in a sample of a radioactive substance to decay

how are radioactive decays used to date carbon base materials and rocks

carbon fourteen and potassium forty, how much of a sample remains, half life, and work backwards

how old is the earth

4.54 billion yrs

how old is the universe

13.8 billion yrs

what binds the nucleus

energy that comes from the difference between the mass of the nucleus and the mass of the parts, which holds protons and neutrons together despite repulsive forces between positively charged protons

what is binding energy

energy required to separate the particles in a nucleus, or the energy released when the nucleus is formed

what is the difference between nuclear fusion and fission

fission is the process where a heavy atomic nucleus splits into two smaller nuclei, releasing energy. fusion is the process where two light atomic nuclei combine to form a heavier nucleus, also releasing energy

what elements are used for fission based on the binding energy curve

for fission, uranium and plutonium are typically used because their large nuclei release a lot of energy and they have low binding energy, meaning they can split easily. for fusion, hydrogen isotopes are normally used because they have low binding energy and combining them releases energy, and when they combine the binding energy increases, which is why the process yields energy

how does a chain reaction occur in the process of nuclear fission

when nuclei split into smaller nuclei, these nuclei can hit other nuclei and split as well, causing a chain reaction

list the applications of fission

powerplants, medical radiation, and atomic bombs

list the applications of fusion

energy research and hydrogen bombs

how does the expansion of the universe lead to production of hydrogen and helium

big bang nucleosynthesis. the universe was hot and dense after big bang, which allowed protons and neutrons and protons to collide and form light elements. universe expanded and cooled, and protons combined to form hydrogen. some of these combined with neutrons to form helium. this all happened very quickly which is why those elements are 99% of the universe

what is the big bang theory

universe began as a singularity, evidence includes cmb, redshift, and abundance of light elements

what is the steady state theory

universe has always existed in a constant, even though the universe is expanding, there is no beginning and end. new matter is create to fill the void when expansion causes galaxies to move, and the energy of the universe appears gradually at the same rate throughout time

how does the big bang theory predict the distribution of the age of galaxies

most galaxies would be created at the beginning of the universe in big bang, and looking at distant objects means we look back in time, so younger galaxies should be further away

how does the steady state theory predict the distribution of the age of galaxies

steady state would have younger galaxies distributed everywhere, because they are being created everywhere

what is the cosmic microwave background

he faint glow of light left over from the early universe, just after the Big Bang

how do you test for the cosmic microwave background with observations

herman and alpher showed that if the big bang occurred then there should exist a residual weak electromagnetic radiation, called cmb. It would have been possible to detect if anyone looked for it. scientists look for a uniform glow because it should be isotropic and homogenous

what is recombination

for the first 300,000 years after the big bang, nuclei and electrons exist as a sort of gas called plasma. after 300,000 years, atoms form because the temp dropped below 300,000 years, and this is called recombination

when did recombination happen

300,000 years after big bang

why did the universe become transparent to electromagnetic radiation at the time of recombination

Before recombination, the universe was filled with free electrons that scattered photons, making it opaque like a fog. When electrons combined with protons to form neutral hydrogen atoms, photons could travel freely without constant scattering, making the universe transparent to electromagnetic radiation.

how were elements other than hydrogen and helium created

elements heavier than hydrogen and helium were created through nuclear fusion and supernova explosions. inside stars, lighter elements fuse under higher pressure and temperature to form heavier ones like carbon, oxygen, and iron. when massive stars explode in supernovae, they release enough energy to create heavier elements like gold and uranium, scattering them into space to form new stars and planets

how is a star formed

when a cloud of gas and dust in space collapses under its own gravity. as the cloud shrinks, it heats up and forms a protostar. when the core becomes hot and dense enough, nuclear fusion begins, turning hydrogen into helium and releasing energy, thus marking the birth of a star

how does the mass of a star determine its future

The bigger a star the shorter its lifetime and the more violent its death

what is a protostar

a young, forming star that is still gathering mass from a collapsing cloud of gas and dust but has not yet started nuclear fusion in its core.

what is a brown dwarf star

less than 0.08 Mass of sun then no nuclear fusion. Becomes a failed star called…

what is a red giant star

After 10 Billion years, core Hydrogen is burnt so fusion zone moves outwards making star more luminous , larger and cooler. then, helium in center has no fusion to counteract gravity so it collapses getting hotter

what is a white dwarf star

small, hot, and dense leftover core of a low- or medium-mass star after it has exhausted its nuclear fuel and shed its outer layers. center of a planetary nebula

what is a supernova

powerful and explosive death of a massive star, occurring when it runs out of fuel, causing its core to collapse and its outer layers to explode, often leading to the creation of a neutron star or black hole.

what is a neutron star

dense, compact remnant of a massive star that exploded in a supernova, consisting mostly of tightly packed neutrons and having an extremely strong gravitational field.

what is a pulsar

a rotating neutron star that emits beams of electromagnetic radiation from its magnetic poles, which can be detected as regular pulses when the beams sweep across Earth.

how are supernova used to determine the accelerating nature of the universe

supernovae, specifically type la supernovae, act as "standard candles" because they have a known brightness. By measuring their observed brightness and comparing it to their expected brightness, scientists can determine their distance. When they find that these supernovae are farther away than expected, it indicates that the universe's expansion is accelerating.

what is equilibrium radiation

radiation that is in a state of balance, where the amount of energy being absorbed is equal to the amount being emitted, resulting in a stable temperature. aka atoms are all same temp

why should the cosmic microwave background be in the form of equilibrium radiation

Cosmic microwave background (CMB) radiation should be in the form of equilibrium radiation because it originated from the early universe when matter and radiation were in thermal balance. As the universe expanded, this radiation cooled while maintaining its blackbody spectrum, which is a key characteristic of equilibrium radiation.

who formulated the theory of stellar nucelosynthesis

fred hoyle, 1946

who predicted the cmb

alpher

who first observed the cmb

alpher and herman

who proved the cmb is equilibrium radiation

mather and smoot

protons and neutrons are made of smaller particles called…

quarks

how are we able to study the smallest scale of matter and why do we use high energy beams

the uncertainty principle tells you the momentum and energy needed to look at small scales, higher energy corresponds to shorter wavelengths, allowing us to resolve smaller structures

what is the size of a quark

ten neg fifteen m

what is the size of a nucleon aka proton or neutron

1.6 times ten neg 15

how does a particle accelerator work

electric fields are used to speed up charged particles and use magnetic fields to steer them. they can be steered in straight or curved lines, and then smashed into things to understand forces

most elemental particles are…

quarks and electrons

how do particles interact at the quantum level

they exchange messenger particles, like tossing a football

what are the four forces of nature and their messenger particles

strong, gluon

electromagnetic, photon

weak, wz

gravity, graviton

why is an electron not pulled into the nucleus by its strong force

The strong force mainly acts between quarks inside protons and neutrons, not between electrons and nuclei. Electrons are bound by the electromagnetic force, but quantum mechanics (specifically the uncertainty principle) prevents them from collapsing into the nucleus.

antimatter is a consequence of…

combining relativity and quantum mechanics

how can antimatter be created

Antimatter is created when high-energy processes, like particle collisions (e.g., in accelerators or cosmic rays), produce particle-antiparticle pairs from pure energy, following Einstein’s E=mc2E = mc^2E=mc2

beams of antimatter and matter can be collided to create…

other high mass pairs of matter and anti matter

how were higher mass quarks and leptons discovered

Higher-mass quarks and leptons were discovered by smashing particles together at high energies in accelerators and detecting the new, heavier particles produced in the collisions using sensitive detectors.

what are the six types of quarks

The six types of quarks are: up, down, charm, strange, top, and bottom.

what are the six types of leptons

The six types of leptons are: electron, muon, tau, electron neutrino, muon neutrino, and tau neutrino

what is a lepton

a fundamental particle that does not undergo strong interactions. They include charged particles like the electron, muon, and tau, as well as their corresponding neutrinos.

under what possible combinations of quarks do stable particles form

Baryons: Composed of three quarks (e.g., proton: up, up, down; neutron: up, down, down).

Mesons: Composed of one quark and one antiquark (e.g., pion: up, anti-down)

with separation, what happens to strong force

increases

what is the higgs field

field that is all over the universe

how does the higgs field give rise to the mass of particles

idea that there is a field everywhere, and all particles with mass interact. interaction causes mass. particles are like a boat moving through water, and resistance to motion is the origin of mass

what is the higgs boson

the observable that confirms the existence of the higgs field

a subatomic particle behaves as what two things

wave and particle

explain the two slit experiment

The two-slit experiment shows that quantum particles like electrons and photons can behave as both particles and waves. When not observed, they create an interference pattern, acting like waves going through both slits at once. But when we observe which slit they go through, the interference disappears, and they behave like individual particles. This reveals the strange nature of wave particle duality, that quantum objects don’t fit neatly into either category and seem to change behavior based on observation.

what is the wave function

mathematical description of a quantum system that contains all the information about a particle's possible states. Its squared magnitude gives the probability of finding the particle in a particular location or state

how does the wave function relate to the probability of a physical outcome

it is the probability, it contains all possible outcomes and likelihood

what did bohr contribute to quantum mechanics

copenhagen interpretation

what did heisenberg contribute to quantum mechanics

copenhagen interpretation, there is a finite limit to which the position and velocity of a particle can be measured simultaneously.

what did schrodinger contribute to quantum mechanics

Equation that the wave function obeys., tells you everything you need to calculate the probability of what a particle will do . It is really a statement of the conservation of energy.

what did pauli contribute to quantum mechanics

In atoms, this means no two electrons can have the exact same set of quantum numbers — which is why they fill up different energy levels and orbitals, giving atoms their structure, exclusion principle