AH 1.5 General Relativity Flashcards
In the spacetime diagram below, the blue shaded region is called time like.
What do the world lines on this diagram represent?
Light, travelling at 3 x 108 ms-1.
What is meant by inertial mass ?
Inertial mass measures a body’s resistance to being accelerated (i.e. have its momentum changed) and is the ‘m’ in mv = momentum.
Notice that inertial mass makes no reference to gravity.
What is the relationship between gravitational mass and inertial mass ?
Inertial and gravitational mass are equivalent
Explain what is meant by the equivalence principle.
The Equivalence Principle (EP) states that inertial mass is equal to gravitational mass. Or, put another way, there is no experiment that will discern the difference between the effect of gravity and the effect of acceleration.
Einstein used the equivalence principle to show that the path of a ray of ligth woud be affected by what?
Einstein used the equivalence principle to show that the path of a ray of ligth woud be affected by gravity.
Copy and complete this statement:
Einstein used the equivalence principle to show that the stronger the ……………………. …………………………. the more ……………………. a clock would run.
Einstein used the equivalence principle to show that the stronger the gravitational field the more slowly a clock would run.
Which clock runs mores slowly - one at sea level or one at the top of Ben Nevis? Explain your answer.
The clock at sea level runs more slowly.
This is because it is closer to the Earth’s centre (i.e. at lower altitude) and so is in a stronger gravitational field.
The stronger the gravitational field, the more slowly a clock runs.
Look at the spacetime diagram below and identify the motions of each line (a), (b) and (c).
(a) stationary
(b) uniform speed
(c) iniform acceleration
What are the lines drawn on a spacetime diagram called?
World lines (or geodesics).
Copy and complete the following statement.
Euclidean space has co-ordinates which uniquely specify a point in space – a location.
Spacetime locates not points in space but ………………………… i.e. not just ……………………… something happens but also ……………………..
Spacetime locates not points in space but events i.e. not just where something happens but also when.
How can gravity be explained ith refrenece to spacetime?
The presence of a massive object, like the earth, curves the ‘fabric’ of space-time. So gravity warps spacetime, as shown below.
By referring to spacetime, explain what is happening in the diagram of the Earth and the Sun below.
The Earth follows the curvature of the spacetime which has been curved by the mass of the sun.
Look at the diagram below.
Explain what is going on.
General Relativity suggests that photons are affected by gravity, meaning that light from distant stars is bent as it passes a massive object like the sun.
This results in the apparent (observed) position of the star being different form its actual position in the sky.
With the aid of a diagram, explain how gravitational lensing occurs.
Massive cosmic objects, such as a galaxy bend and focus the light that flows around them using their gravity, acting like giant magnifying glasses. This effect is called gravitational lensing.
The diagram below shows the effect.
Describe in words what is meant by a black hole.
A black hole is a star of such high density that it’s escape velocity is greater than the speed of light. So, not even light can escape it’s gravitational pull.