im fucked Flashcards
How do you derive a light year?
A light year is the distance travelled by light in a year
(310^8)606024*365
What is gravitational field strength?
The gravitational force acting on a unit mass
How would you sketch gravitational field lines/field line patters around two astronomical objects
(to be confirmed)
What is the gravitational potential of a point in space?
the work done in moving a unit mass from infinity to that point
What is true about the path taken in relation to moving a mess between two points in a gravitational field?
The energy required is independent of the path taken.
What is escape velocity?
The minimum velocity required to allow a mass to escape a gravitational field to infinity.
What is the difference between special and general relativity?
Special relativity deals with motion in non-inertial (accelerating) frames of reference
what is spacetime?
A unified representation of three dimensions of space, and one dimension of time.
How does general relativity interpret gravity?
Mass curves spacetime, and gravity arises from that curvature of spacetime.
Light or a freely moving object follows what in spacetime?
A geodesic
(the path with the shortest distance between two points)
What is the escape velocity from the event horizon of a black hole? what is the consequence of this?
The speed of light.
Light (or anything) cannot escape a black hole because it needs a velocity higher than the speed of light which is impossible.
What is the Schwarzschild radius of a black hole?
The distance from its centre to its event horizon
what are the following stellar light level units?
b = apparent brightness of the star
L = luminosity of the star
P = power
A = area
σ = stefan boltzman’s constant
T = temperature of star
How are stars formed?
Stars are formed in interstellar clouds when;
- gravitational forces overcome thermal pressure, causing a molecular cloud to contract
- thus core becomes hot enough to sustain nuclear fusion
- thus providing a thermal pressure that balances gravitational force.
