Question

1. What is a particle accelerator?
   How do scientists use particle accelerators to study subatomic particles?
2. What particle is exchanged to generate each of the four fundamental forces?
3. What medical technologies (e.g. PET) rely on the physics of elementary particles?
   What are the benefits of noninvasive procedures such as PET?
4. How is astronomy the oldest science?
5. How does the energy produced at the core of the Sun reach the photosphere?
6. Why won

Answer 1

1)

Particle accelerators use electromagnetic forces to accelerate charged particles (protons or electrons) to
great speeds/energies. This same principle is used in old-style TV tubes to accelerate and steer beams of
electrons to the back of the screen, causing the illumination of the picture tube. Some designs accelerate
the particles along a straight track, and others contain them in a large circular beam line.
Accelerators are used primarily for scientific research, and a number of industrial and medical applications.
Particle physicists use the accelerators to study the interactions of elementary particles by observing the
byproducts of the high-energy collisions. These collisions give clues as to the structure of the subatomic
world.

2)force :   mediating particle
electromagnetic: photon
nuclear weak:W and Z bosons
nuclear strong: gluons
gravitation: gravitons

3)The  medical technologies (e.g. PET) rely on the physics of elementary particles are :

>cancer treatment

> Magnetic Resonance Imaging ( MRI)

>Ion Implantation

>Food Irradiation

PET and PET/CT scans are performed to:

• detect cancer.
• determine whether a cancer has spread in the body.
• assess the effectiveness of a treatment plan, such as cancer therapy.
• determine if a cancer has returned after treatment.
• determine blood flow to the heart muscle.
• determine the effects of a heart attack, or myocardial infarction, on areas of the heart.
• identify areas of the heart muscle that would benefit from a procedure such as angioplasty or coronary artery bypass surgery (in combination with a myocardial perfusion scan).
• evaluate brain abnormalities, such as tumors, memory disorders, seizures and other central nervous system disorders.
• map normal human brain and heart function.

4) People have no doubt tried to understand the movement and behavior of the heavens since the first humans
looked up at the skies. The oldest records of any analytical studies date back to Mesopotamia, over five
thousand years ago. At that point, the study of astronomy was primarily focused on calendrical studies
using it to predict seasons, weather, tides and other natural cycles. It was generally practiced by a select
group of priests.

5)

Photons produced in the solar interior bounce randomly among electrons in the plasma, slowly working
their way outward to the photosphere. Even though they travel at the speed of light, the path they take
through the interior bounces around so much that it takes hundreds of thousands of years to get out! The
reason is that plasma is so dense that photons can only go a tiny distance (less than a millimeter) before
they collide with a particle and get redirected. They continue bouncing around, and eventually, the average
behavior is that they slowly diffuse outward.

6)

The Sun is too small, lacking the critical mass to end in a supernova. Instead, it will turn into a red giant,
end up as a white dwarf. Only high-mass stars (about 8 times as big as the Sun) have sufficient mass to end
their lives with a supernova and subsequently collapse to a black hole.

7)The fact that the universe appears to be expanding in all directions is the logical consequence of an earlier
explosion, and hence supports the conjecture that the universe experienced a