CPCS581 Test 1

What is the approximate size of a stellar black hole?

About 20-100 km across, roughly the size of a city.

What is the approximate size of a supermassive black hole?

About 3 billion km, roughly from the Sun to Uranus.

How far back in time can current physics models trace the universe's history?

To about 10⁻¹⁰ seconds after the Big Bang, with earlier times remaining uncertain.

What are dark matter and dark energy collectively responsible for?

They make up about 95% of the universe's total content, with dark matter accounting for ~27% and dark energy ~68%.

What is the primary process that powers stars like the Sun?

The proton-proton chain, fusing hydrogen into helium.

What is the key difference between the Big Bang and a traditional explosion?

The Big Bang was an expansion of space itself, not an explosion in space.

Which forces dominate on small scales?

The strong and weak nuclear forces.

What is the Schwarzschild radius?

The radius to which an object must be compressed to become a black hole, where escape velocity equals the speed of light.

What is the approximate age of the universe?

The universe is about 13.8 billion years old.

What does blueshift indicate about a galaxy's motion?

Blueshift indicates a galaxy is moving toward us.

Which fundamental force is stronger on large scales?

Electromagnetic force.

What was the state of the universe during the Planck Era?

A single unified super force with no particles or photons, smaller than a proton.

What is the Chandrasekhar limit?

Approximately 1.4 solar masses, the maximum mass a white dwarf can have before collapsing into a neutron star or black hole.

What does the Bullet Cluster demonstrate about dark matter?

Dark matter does not feel friction and passes through collisions unaffected, unlike gas which slows down.

What is the main method used to prove dark energy?

Studying the accelerated expansion of the universe using supernovae as standard candles.

What is the approximate size of a stellar black hole?

About 20-100 km across.

What is the primary reason nucleus is not a good candidate for dark matter?

Nuclei are baryonic matter, which interacts strongly and electromagnetically, unlike dark matter which interacts weakly.

Can dark matter exist within the solar system or on Earth?

Yes, dark matter could be present and would be invisible and hard to detect.

What evidence supports the existence of dark matter?

Galaxy rotation curves and galaxy cluster orbits show stars far from galaxy centers orbit faster than visible matter can explain.

What fusion process dominates in high-mass stars?

The CNO cycle, which uses carbon, nitrogen, and oxygen as catalysts.

What triggers a Type Ia supernova?

A white dwarf in a binary system accretes mass until reaching 1.4 solar masses, igniting carbon fusion explosively.

What is the size of the observable universe?

Approximately 46 billion light-years in radius.

What was the first confirmed discovery of exoplanets around a pulsar?

Three planets orbiting PSR B1257+12, detected via timing variations in pulsar pulses.

How does inflation explain the uniform temperature of the universe?

Inflation expanded a small, thermally connected region to a much larger size, homogenizing temperature.

Why can we only see about 14 billion light-years into the universe?

Because light from beyond that distance hasn't reached us yet due to the finite speed of light.

What law describes the relationship between a galaxy's distance and its recession speed?

Hubble's Law states that twice as far a galaxy is, twice as fast it recedes.

What is a WIMP wind and why does it occur?

A WIMP wind is the flow of dark matter particles passing through the solar system at 220 km/s due to the Sun's orbit around the galaxy.

What is the key idea behind quintessence in dark energy?

Dark energy is a variable, dynamic field rather than a constant.

What causes pulsars to slow down over time?

Emission of electromagnetic radiation carries away energy and angular momentum, causing gradual spin-down.

What is the main difference between a nova and a supernova?

A nova is a surface explosion on a white dwarf, while a supernova involves the complete explosion of a star.

What is the main principle of Heisenberg's Uncertainty Principle?

The product of the uncertainties in position and momentum of a particle must be greater than or equal to ħ/2.

What are pulsars and how are they detected?

Rapidly rotating neutron stars emitting beams of radiation detected as periodic pulses when the beam points toward Earth.

What does redshift indicate about a galaxy's motion?

Redshift indicates a galaxy is moving away from us.

What is cosmic inflation?

A rapid expansion of tiny regions of space during the GUT Era, faster than the speed of light.

What is the defining feature of a black hole?

Light cannot escape from within its event horizon.

According to MOND

how does gravity behave in the outskirts of galaxies?, Gravity remains strong and does not diminish as Newtonian gravity would predict.

What is the observable universe?

The limited part of the universe we can see, like a visible bubble around us, possibly infinite in size.

What was the initial state of the universe according to the Big Bang theory?

A tiny, hot, dense point that expanded to form everything we see today.

Why are neutrinos unlikely candidates for dark matter?

Because they are too light and fast to account for the gravitational effects attributed to dark matter.

What triggers a Type Ia supernova?

A white dwarf exceeding the Chandrasekhar limit due to accretion, causing core collapse and explosion.

What are bubble universes and how do they relate to inflation?

Regions of space where inflation ended, forming separate 'bubble' universes with potentially different physical laws.

What is the minimum mass of a core remnant that can support itself as a neutron star?

Approximately 1.4 solar masses, known as the Chandrasekhar limit.

How do gravitational waves affect neutron star binaries?

They carry away energy, causing the neutron stars to spiral inward and eventually merge.

What are the two main strategies for simulating reality according to programming hypotheses?

Emergent strategy—building blocks from which reality emerges; and Ultra-reductionist—reducing everything to fundamental rules.

What process powers stars like the Sun?

Hydrogen fusion via the proton-proton chain in the core.

What is a tesseract in four-dimensional geometry?

A tesseract, or hypercube, is a 4D cube made of 3D cubes as its 'sides'.

How do scientists measure the acceleration of the universe's expansion?

Using supernovae as standard candles to observe the increase in their distance over time.

What triggers a Type Ia supernova?

A white dwarf accretes enough mass to exceed the Chandrasekhar limit, igniting carbon fusion explosively.

How does a pulsar produce its characteristic pulsed signals?

Beams of radiation emitted from magnetic poles sweep past Earth as the neutron star spins, creating regular pulses.

What is the primary energy source during the hydrogen-burning phase in stars?

Hydrogen fusion through the proton-proton chain or CNO cycle.

What is MACHO in the context of dark matter?

Massive Compact Halo Objects like brown dwarfs, planets, or black holes, but they are insufficient to explain dark matter.

What is cosmic inflation and when did it occur?

A rapid exponential expansion of the universe occurring during the GUT Era, solving the horizon and flatness problems.

What is a cyclic universe model?

A universe that undergoes infinite cycles of expansion and contraction, with big bang followed by big crunch.

What would a 3D string piercing a 2D Flatland look like?

It would appear as a 2D circle in Flatland.

What is the Schwarzschild radius and how does it relate to black holes?

The radius to which a mass must be compressed to form a black hole; within it, escape velocity exceeds the speed of light.

What major questions does the Cosmic Microwave Background (CMB) analysis reveal about the Big Bang?

Origin of density enhancements, why the universe is so smooth, and why its curvature is so close to flat.

What are magnetars and how do they differ from typical neutron stars?

Neutron stars with extremely strong magnetic fields ($10^8 - 10^{11}$ T) that can cause intense X-ray and gamma-ray bursts.

How many times smaller is a nucleus compared to an electron cloud?

Approximately 10,000 times smaller.

What is the flatness problem and how does inflation address it?

The universe's density is close to critical, indicating flatness, which inflation naturally produces by stretching space.

What is a superposition in quantum mechanics?

A quantum system exists in multiple states simultaneously until measured, like Schrödinger's cat being both alive and dead.

What is the cosmological constant and what role does it play?

A universal force causing the acceleration of the universe's expansion, associated with dark energy.

What is the Schwarzschild radius and how does it relate to black holes?

The radius at which an object must be compressed for its escape velocity to equal the speed of light, defining the event horizon.

What distinguishes a magnetar from typical neutron stars?

Magnetars have extremely strong magnetic fields, 10^8 to 10^11 Tesla, much stronger than typical neutron stars.

What are pulsars and how are they observed?

Rapidly rotating neutron stars emitting beams of radiation aligned with their magnetic poles, observed as regular pulses.

What is the primary reason for the flatness of the universe?

Inflationary expansion drove the universe's curvature close to zero, resulting in a flat geometry.

What is the main purpose of accretion disks in binary systems involving compact objects?

They facilitate mass transfer onto the compact object, producing high-energy emissions like X-rays.

What is the role of accretion disks in binary star systems involving white dwarfs or neutron stars?

They allow material to settle into orbits, heat up via friction, and can lead to phenomena like novae or X-ray bursts.

What does the Holographic Principle suggest about information in a volume of space?

All the information within a 3D volume can be encoded on its 2D boundary surface.

What was the first confirmed discovery of exoplanets around a pulsar?

Three planets detected orbiting PSR B1257+12 via timing variations in pulsar signals.

What is the key difference between cyclic models of the universe and models involving dark energy and inflation?

Cyclic models have no inflation and dark energy is present throughout, while the brief period models involve unrelated, temporary dark energy and inflation.

What evidence supports dark matter from galaxy rotation curves?

Stars far from galaxy centers orbit as fast as those near the center, implying unseen mass or dark matter.

What is the main idea behind the simulated universe hypothesis?

Our reality could be a computer simulation, indistinguishable from real life, with all information processed in the brain.

How does the holographic parallel universe relate to black holes?

The surface of a black hole contains all the information of its interior, creating a duplicate 2D universe.

What is the key characteristic of a black hole?

Light cannot escape from within its event horizon.

What is the main idea behind the Steinhardt-Turok (Ekpyrotic) model?

Two branes collide, causing the big bang, then separate and eventually collide again, leading to cyclic rebirth.

What is the primary process powering stars like the Sun?

Hydrogen fusion via the proton-proton chain.

What is the primary observational evidence for dark matter in galaxies?

Galaxy rotation curves where stars far from the center orbit faster than expected based on visible matter alone.

What is the ultimate fate of a star with a core exceeding the Chandrasekhar limit?

It collapses into a black hole or neutron star, depending on mass.

What does the Copenhagen interpretation of quantum mechanics propose occurs during measurement?

Measurement collapses the wave function into a definite state, requiring an observer.

What causes pulsars to slow down over time?

Emission of electromagnetic radiation carries away energy and angular momentum, reducing their rotation speed.

What is the Schwarzschild radius?

The radius to which an object must be compressed for it to become a black hole, where escape velocity equals the speed of light.

What is the significance of the 'light echo' phenomenon in supernova remnants?

It occurs when supernova light reflects off surrounding dust clouds, allowing us to observe the explosion after the initial event.

What is the core concept of the Many-Worlds interpretation?

All possible outcomes of quantum events occur in separate, branching universes, and the wave function never collapses.

How is time conceptualized as a fourth dimension in cosmology?

Time is a fourth dimension that, along with three spatial dimensions, helps specify when and where events occur in the universe.

What is the significance of the Bullet Cluster in dark matter evidence?

It shows galaxy clusters passing through each other with gas slowed but dark matter unaffected, confirming dark matter's existence.

What is a neutron star supported by?

Neutron degeneracy pressure.

What is the minimum mass for a core remnant to support itself as a neutron star?

Approximately 1.4 solar masses, known as the Chandrasekhar limit.

What is the fate of a star with a core exceeding the Chandrasekhar limit?

It collapses into a neutron star or black hole, often resulting in a supernova explosion.

What is the Chandrasekhar limit?

The maximum mass (~1.4 solar masses) a white dwarf can have before collapsing into a neutron star or black hole.

What causes a neutron star to slow down over time?

Emission of electromagnetic radiation and particle winds carry away angular momentum.

What is the main idea behind the Many-Worlds interpretation of quantum mechanics?

All possible outcomes of quantum events occur in separate, branching universes.

What is the typical size of a supermassive black hole's event horizon?

Approximately billions of kilometers, comparable to the distance from the Sun to Uranus.

How do gravitational waves affect neutron star binaries?

They cause the orbit to decay over time, leading to inspiral and eventual collision, observable as kilonovae.

What is the key concept of the Holographic Principle?

All information within a volume of space can be encoded on its boundary surface.

What is the fate of a star with a core mass exceeding the Tolman-Oppenheimer-Volkoff limit (~3 solar masses)?

It will collapse into a black hole.

What is a magnetar and how does it differ from typical neutron stars?

A neutron star with an extremely strong magnetic field (10^8-10^11 T), much stronger than typical neutron stars.

What is the primary observational evidence for dark matter in galaxies?

Galaxy rotation curves showing stars far from the center orbit at the same speed as nearby stars, implying unseen mass.

What is a cyclic universe model?

A universe that undergoes endless cycles of expansion and contraction, rebounding after each collapse.

What is gravitational wave emission in neutron star binaries and its significance?

Neutron star pairs emit gravitational waves, causing their orbits to decay and eventually merge.

What is the process that powers stars like the Sun?

Fusion of hydrogen into helium in the star's core.