Cosmology Quiz March 21

________’s theory of gravity gives the correct predictions in conditions of low gravity. (and also if spacetime is flat)

Newton

______’s Theory gives correct predictions in all strengths of gravity and so is the most general theory

Einstein

the bending and magnification of light from a distant object due to the gravitational field of a massive foreground object, often creating distorted or multiple images of the background source, helpful for identifying dark matter

gravitational lensing

is a nearly perfect circular image of a distant object(quasar or galaxy) formed when its light is gravitationally lensed by a massive foreground object due to precise alignment with the observer.

einstein ring

what are the two components of the cosmological principle

1. The universe is isotropic : It looks the same in every direction

2. The universe is homogeneous: It looks the same at every point

Einstein assumed that the universe was _______. Einsteins assumption was made before the discovery of Hubble expansion

static

Einstein assumed the solution is symmetric in space-time interval, but it collapses in on itself because of the effect of _______

gravity

einstein added the _________ ______ to oppose the gravitational collapse, he eventually called this his biggest mistake

cosmological constant

The Galaxies are receding because spacetime is expanding. As spacetime expands it stretches the ________ __ _____ as shown causing redshift

wavelength of light

The _______ density of the universe determines whether the universe will collapse on itself or expand for ever.

energy (matter)

is the universe open, closed, or flat

flat (spacetime is curved locally around massive objects but this is describing the Universe as a whole)

The accelerating expansion of the universe implies that something is….

powering the expansion

in einsteins equation, what percent of the energy of the universe is coming from the cosmological constant

72

what extremely strong case of gravity is newtonian gravity not applicable to

black holes

what balances the gravitational attraction that balances nuclear fusion

photon pressure

A dying large mass star (> 25 solar masses) will collapse and then explode as a Supernovae, the exterior of the the star is blown away but the interior keeps collapsing and a highly compact object is remnant

stellar evolution

Earth will not compress to 1cm because of xxxxxx xxxxxxx but a supernovae creates the necessary force to compress a star remnant

nuclear repulsion

what size would the sun need to be to be compressed to a black hole, and would it cause a supernova, and how many masses would be needed

3 km, no it would die slowly, 25

As matter gets xxxx dense the spacetime around it becomes more warped, and eventually Spacetime “xxxx” over on itself and sealed bubble of spacetime is formed

more, folds

tter is torn apart and heated as it falls in. It emits energetic what-rays as it falls in

x rays

can you orbit a black hole

only at a distance

can we see x rays in earths atmosphere

no

a system of two black holes orbiting around their common center of mass due to their mutual gravitational attraction, x ray radiation has an observable time dependence

black hole binary

what does a lorentz transformation refer to

things like time dilation, length contraction, etc

the shortest path between two points in a curved space or spacetime, generalized from a straight line in flat space to account for gravitational effects in general relativity.

geodesic

what are the two axioms of general relativity

equivalence principle and general covariance

Locally, the effects of gravity are indistinguishable from acceleration, meaning that free-falling observers experience no gravitational force

equivalence principle

The laws of physics take the same form in all coordinate systems, meaning they are independent of any specific choice of reference frame

general covariance

who discovered the solutions of general relativity that proved an expanding universe

lemaitre and friedman