Evidence to Support Special Relativity

H.5.1 - Discuss Muon Decay as experimental evidence to support special relativity.

Evidence: The evidence to support the Muon experiment is that theoretically, Muon particles should be undetected at the surface of the earth because it has such a short life time.'2.2 x 10^-6 seconds' as measured in actual time. In actuality Muon particles are detected on the Earth's surface, and therefore provides evidence to support special relativity.

Conclusion: For the Muon's frame of reference the muon is experiencing proper time, but the length of the atmosphere is contracted to compensate for its speed.

For the observer on earths frame of reference the muon is is travelling at the proper length, but has an dilated life time.

H.5.2 - Solve problems involving the moon decay experiment


H.5.3 - Outline the Michelson and Morley experiment



The experiment was carried through like the flash animation above. A beam of light would hit a half-mirror which would reflect half the light and let through half the light. By doing so the "aether" would supposedly assist the speed of the light or slow down the speed of light.

The aim of the experiment is to find the speed of the earth travelling through space. They were trying to measure the speed of the Earth through the Aether.

H.5.4 - Discuss the result of the M&M experiment and its implication

In the end, the M&M experiment failed, no matter which orientation or location they performed the experiment in the speed of light always remain consistent. Therefore the scientist disproved the existence of "Aether" as well as provide the evidence to support the first postulate of relativity. "The constancy of the speed of light"

H.5.5 - Outline an experiment that indicates that the speed of light in vacuum is independent of its source

The Pion Decay Experiment:

The experiment analysed the decay of a particle called the Neutral Pion into two gamma-ray photons. The speed of the Neutral Pion was known to be travelling at 99.9% the speed of light, therefore the speed of the two gamma ray photons that are ejected from the neutral Pion must be even faster than that.

In the end the speed of the Photons were measured to be consistent with the speed of light.

This proves that speed of light is constant !

H1 - Introduction to Relativity

Frames of Reference

H1.1 - Describe what is meant by a frame of reference
The point of view of the observer is the frame of reference, When you are standing still and looking at a moving object, you are in the Earth's frame of reference

When a frame of reference is adopted, the position of the observer in that frame becomes the zero of position. If the frame is a moving one, the zero of the position moves with the observer.




Example.

H.1.2 - Describe what is meant by a Galilean Transformation

It is the relationship between two different Galilean transformation. (it does not take the theory of relativity into consideration. 

H.1.3 - Solve problems involving relative velocities using the Galilean Transformation equations.

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G3. This question is about relative velocities.
(a) Describe what is meant by a Galilean Transformation. /1)

Are transformation made under the assumptions that time measurements are independent of the observer

(b) Two electrons travel along the same straight line towards each other. The speed of each electron with       respect to an observer in the laboratory frame of reference is 0.9800 c.

Calculate the relative speed of the electrons using
(I) the Galilean transformation equation. /1]

Speed of the electrion would equal 0.98 c * 2 = 1.86 c

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Option G Relativity

GI. This question is about the speed of light.
A pion is an unstable particle that decays into two photons. A particular pion,   travelling at 0.900 c with respect to an observer at rest in a laboratory, decays into two photons, L and R, travelling in opposite directions as shown in the      diagram.

The speed of both photons as measured by the observer at rest with respect to the pion is e.
(a) Calculate the velocity of photon R with respect to the observer in the        laboratory using
(i) Galilean kinematics.

The Velocity of Photon R using Galilean kinematics would be 1.9c

What is the limitation of Galilean transformation technique? What was 'invented' to overcome this?

E.4 Cosmology

E.4.8 Distinguish between the terms open, flat and closed when used to describe the development of the universe.

A Closed Universe is one that will eventually collapse back on itself

An Open Universe is one that continues to expand. Gravity slows the rate of expansion but is not strong enough to stop it

A Flat Universe is somewhere between the 2 possibilities the force of gravity slows the expansion, but theoretically will take an infinite amount of time to come to rest.

E.4.9 Define the term "Critical density" by reference to a flat model of the development of the universe.

Critical Density - is defined as the theoretical value of the density that would create a flat universe. It is approximately 5 x 10^-26 kg m^-3 (Extremely Small)

E.4.10 Discuss how the density of the universe determines the development of the universe

The Outcome of the universe depends on the Mass Density, the amount of matter available per unit volume available to provide gravitational attraction.

Critical density = Flat Universe

More than Critical Density = Closed Universe

Less than Critical Density = Open Universe

Ω = Density of the Universe / Critical Density

Closed Universe: Ω > 1

Open Universe: Ω < 1

Flat Universe: Ω = 1

E.4.11 Discuss problems associated with determining the density of the universe


The main problem with determining the density of the universe is the fact that we can only 'see' approximately 10% of the universe. This is because the majority of the universe is made up of 'Dark Matter'

Dark Matter - Mass that is too cool for radiation to be detected

Macho's and Wimp's serve as hypothetical particles which serve as an alternate solution to the problem of Dark Matter.

MACHO's - Massive Astronomical Compact Halo Objects

WIMP's - Weak Interacting Massive Particles