Einstein's Theory

Question 1

Explain Yukawa’s model.

Answer 1

• As the electrons approach each other both would emit photons which would, not only cause the emitting electron to recoil, but would also cause the receiving electron to retreat in the opposite direction under the impact.
• So, repulsion of the two like charges comes about by the exchange of photons.

Question 2

What are Gravitons ?

Answer 2

It has now been proposed that the very weak gravitation force is mediated through particles called gravitons, however, so far, these have never been detected.

Question 3

What is an Antiparticle?

Answer 3

• A subatomic particle having the same mass as a given particle but opposite electric or magnetic properties.
• Every kind of subatomic particle has a corresponding antiparticle.
  e. g. the positron has the same mass as the electron but an equal and opposite charge.

Question 4

What are Neutrinos?

Answer 4

• The very small particle emitted in addition to the proton and B particles was detected and was named the neutrino.
• Neutrinos (an antineutrinos) had to have zero charge and an extremely small (if not zero) mass, with the ability to pass right through the Earth without interacting with it at all.
• This made the neutrino’s initial detection extremely difficult and hence they were not detected until the 1960s.

Question 5

Summaries all the sub-atomic particles.

Answer 5

The lighter particles were considered to be truly elementary (e.g electron and the neutrinos) but other, heavier, particles, called hadrons, seemed to posses some finer, internal composite structure.

Question 6

How did the Quark Theory come about?

Answer 6

Because of the sheer number of these hadrons, it was thought that they might be made up of smaller, truly elementary particles, thus the Quark Theory was evolved.

Question 7

What are Quarks?

Answer 7

-Quarks were deemed to have either 1/2 or 2.3 of an electronic charge which, when combined, could produce either a full negative or positive charge or a zero charge.

Question 8

What are 3 attributes that give Quarks different properties?

Answer 8

1. Up or down quarks (Up=+2/3 charge, Down = -1/3 charge.)
2. Strange or charm quarks (s,c)
3. Bottom or top quarks (b, t)

Question 9

What are gluons?

Answer 9

They are particles exchanged by quarks themselves to produce the forces holding them together and hence to hold the larger composite particles (hadrons) together.

Question 10

Summaries all the Existing Particles.

Answer 10

1. Those existing within the nucleus, called Hadrons that are all made up from quarks.
2. Fundamental particles existing outside the nucleus, called Leptons (light particles).
3. Particles responsible for the 4 main forces existing in nature (electromagnetic, gravitational, strong nuclear and weak nuclear forces.)

Question 11

What is the standard model?

Answer 11

It is the combination of ideas laid out in this section, plus some later modifications, such as the ‘coloured’ and ‘charmed quarks’, which explain the nature and properties of the basic forces and particles of matter.

Question 12

How are there different realities?

Answer 12

On the Earth we have different Frame of reference to that of the star and so there are different realities, depending on where an observer is situated.

Question 13

What did Einstein explained?

Answer 13

That there is not absolute frame of reference as everything is relative - time, distance and mass.

Question 14

What does E=mc*2 show?

Answer 14

This equation shows the amount of energy that could be obtained from a mass of matter if it were to be completely converted.

Question 15

What is Space-Time?

Answer 15

The concepts of time and three-dimensional space regarded as fused in a four-dimensional continuum.

Question 16

What did Einstein propose about Space-Time?

Answer 16

• Space-time is a single entity.

- Space-time was distorted by large masses, such as the Sun or black hole.

Question 17

We would say that a meteor passing close to the Sun would have its path bent by the gravitational pull of the Sun’s mass. However,

Answer 17

Einstein explained it a different way by saying that the meteor moved in a straight light through space-time but the space-time itself was bent by the Sun’s mass.

Question 18

What conclusion does the ‘curvature of space’ leads us to ?

Answer 18

That space-time must be curved around the total mass of the Universe, so much so that, if we travelled in what we could think is a straight line for long enough, we would come back to where we started.

Question 19

What is a postulate?

Answer 19

It is a claim or assumption made without proof.

Question 20

What was the first postulate made in Einstein’s Special Theory (SR)?

Answer 20

That the laws of physics would be the same, regardless of the frame of reference.

e.g. in a car crash the Law of Conservation of Energy would apply to the crash to an observer in the car or by the side of the road.

Question 21

What is the second postulate made in Einstein’s Special Theory (SR)?

Answer 21

• This postulate caused a lot of dissent in the scientific community at the time Einstein revealed it in the early 1900s.
• This postulate was that the speed of light remained constant to an observer, regardless of his frame of reference.

Question 22

What are the two errors that results from the two postulates due to our system of understanding or “common sense’?

Answer 22

1. Our equations for relative velocity are only correct for the slow moving objects that we have experience with,
2. Something was wrong with traditional basic ideas of space and time.

Question 23

What is Time Dilation?

Answer 23

In the theory of relativity, time dilation is a difference of elapsed time between two events as measured by observers either moving relative to each other or differently situated from a gravitational mass or masses.

Question 24

What is the Inertial Frame of Reference?

Answer 24

1. On the surface of it, this does not seem logical, as the twin left behind could just as well be viewed by the other twin as moving backwards at close to the speed of light.
2. Einstein resolved this dichotomy by proposing that the twin left behind was defined as being an Inertial Frame of Reference (i.e. had not accelerated), whereas it was the twin who had left Earth who had undergone acceleration and had therefore experienced the time dilation.

Question 25

The equation predicts that a spaceship moving at the speed of light would appear to have no length at all! Explain this in other words.

Answer 25

If you were on a spaceship travelling at the speed of light all distances would shrink to zero and so it would take you zero time to move to anywhere in the Universe!

-You can’t get there any quicker that that, so you cannot exceed the speed of light!