Physics 7 homework #8

        Due 5/26/09

 

1.      Where in the universe did the Big Bang happen?

a)       Near our galaxy, the Milky Way

b)      At the center of the universe

c)      Everywhere in the universe

d)     In the region the most distant galaxies form the Milky Way are located

2.      All far-away galaxies are seen to recede from the Milky Way. How does the General Theory of Relativity explain this?

a)      By assuming there is a repulsive force emanating form our galaxy

b)      By noting that space is expanding so that the distance between any two far-away galaxies is steadily increasing

c)      By assuming that there is an attractive force from the other side of the universe

d)     By noting it is a consequence of the centrifugal force generated during the Big Bang

3.      Does the General theory of Relativity predict a precession of Earth's orbit (beyond the one predicted by Newtonian mechanics)? If yes, why is this not used to test this theory?

a)      No, the theory predicts precisely zero additional (that is non-Newtonian) orbital precession

b)      The general theory predicts a very large additional precession, currently being looked for by various satellites

c)      The general theory does predict a very small additional precession, but it is too small to be measured (at least by current technology)

d)     The general theory does predict exactly the same additional precession for all the planets, but it has not been observed for any planet but Mercury. This represents a failure of this one aspect of the theory

4.      In a homogeneous and isotropic universe regulated by the General Theory of Relativity, what determines whether it will re-contract or expand forever?

a)      The average amount of matter and energy per unit volume in the universe

b)      The speed at which it is expanding

c)      The pressure exerted by matter

d)     Whether the electromagnetic forces are strong enough (for example, if there are large number of charges in the universe)

5.      What is the equivalence principle? What does it imply when considering the motion of objects under the influence of gravity?

a)      The equivalence principle states that inertial and gravitational masses are identical, it implies that all objects experience the same acceleration under gravity

b)      The equivalence principle states that all inertial observers are equivalent, and it implies that gravity is absent in all inertial frames

c)      The equivalence principle states that gravitational and inertial masses are identical  only in inertial reference frames; and it implies that gravitational acceleration is proportional to the square of the mass

d)     The equivalence principle states that speed of light is absolute, and it implies that mass and energy are equivalent

6.      Two bugs move along the surface of a sphere from the equator to the north pole, they find that

a)      They move apart as the proceed, precisely as if they were experiencing en electrostatic repulsion

b)      They move steadily closer together even though according to each their trajectory is straight

c)      They remain at the same distance form one another

d)     They move closer together because they purposefully do not move along a straight line

7.      The Cosmological Constant

a)      Was proposed as a way of balancing the predicted expansion of the universe, rendering it static

b)      Was proposed as a way of explaining the expansion of the universe

c)      Was shown by Einstein to be the reason general relativity predicted an expanding universe.

d)     Was an addition to Newton’s equations shown by Einstein to be unnecessary to produce a static universe.

8.      If we could add matter to the present universe, and we do so continuously, eventually  the result would be

a)      That the universe would eventually stop expanding and will re-collapse

b)      Nothing really interesting

c)      That the rate of expansion would increase

d)     That the universe would start expanding and contracting periodically

9.      The Andromeda galaxy is 106 light years away and the distance form the Earth to the Sun is about  1.5 x1011 m. Imagine now that whole universe shrinks, so that Earth’s orbit is now 30 cm across (assume it is a circle). Then, how far away will Andromeda be?(assume a light year is exactly  1016 m)

a)      About  1022 m

b)      About  106 light years

c)      About 30 cm.

d)     About  1010 m

10.  Dorothy and Toto are caught up right in the middle of a tornado; to a good approximation their environment is

a)      Not homogeneous but isotropic

b)      Homogeneous but not isotropic

c)      Both homogeneous and isotropic

d)     Neither homogeneous nor isotropic