Cosmology April 3

what is the big bang theory of the universe

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

what is the steady state theory of the universe

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

what is the difference between the big bang and steady state theories of the universe

constant existence vs. instant creation

what does the steady state theory and the big bang theory say respectively for the distribution of 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. steady state would have younger galaxies distributed everywhere, because they are being created everywhere

how to test the cosmic microwave background

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 recombinationp

when did recombination happen

300,000 years after big bang

why does the universe become transparent to electromagnetic radiation during 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 in stars and supernova explosions. Inside stars, lighter elements fuse under high pressure and temperature to form heavier ones like carbon, oxygen, and iron. When massive stars explode in supernovae, they release enough energy to create even heavier elements like gold and uranium, scattering them into space to form new stars and planets

how is a star formed

A star forms 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—this marks 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 prostar

A protostar is 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 coole. 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 supernovae

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 supernovae used to determine that the expansion of the universe is accelerating

Supernovae, specifically Type Ia 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

adiation 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 cosmic microwave radiation 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 nucleosynthesis

Fred Hoyle in 1946.

who first observed the cmb

alpher and herman

who proved the cmb is equilibrium radiation

mather and smoot