A particle moving in the x-direction has 4-velocity u = (√5, 2,0,0). a. Compute the norm squared of this 4-velocity.
b. Derive the value of the speed V = dx/dt of the particle in the frame in which the components of u have been specified.
c. What is the mass m of the particle if it has energy E = 2mo, where mo is some mass unit?

layers of the earth affect the waves and these effects are seen on instruiments such as seimometers

a lot of it means it can be "burned" for energy and sold at one price. if it is scarce, the price will go up

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia