# Need help with some questions on relativity please

1. Jul 23, 2010

### ArtStudentEli

1. The problem statement, all variables and given/known data

If you were on Venus instead of on the Earth, using principles of general relativity, would you expect the Sun to appear redder or bluer? Why?

According to Mach's principle how would the rotation of objects differ in a universe with less matter in it? Explain how measurable quantities such as centripetal force, angular momentum, and moment of inertia would change, if at all.

A flashbulb is set off in the center of a car on a moving train. Light sensors on the front and rear walls of the car record the light emitted by the flash bulb. Describe how the light would illuminate the walls of the car as observed by an observer on the train and an observer standing next to the tracks on the ground. Explain the observations.

Solar neutrino deficit is an astrophysics problem. In short the fusion of hydrogen atoms into helium releases neutrinos, which are subatomic particles. The problem is that only one-third of the necessary number of neutrinos is measured. You can solve this problem if the neutrinos are changing their form while traveling between the Sun and the Earth. If they are changing form what are the implications with regard to their velocity? What are the implications with regard to their mass? Justify your answers.

THANKS AGAIN =)

2. Jul 23, 2010

### QuarkCharmer

I believe this one is a relatively simple explanation using the dopplar effect.
http://en.wikipedia.org/wiki/Doppler_effect
Specifically (from that link): "For waves which do not require a medium, such as light or gravity in general relativity, only the relative difference in velocity between the observer and the source needs to be considered." Without giving it away

I believe this one to be explained by the Coriolis effect.

This one is also explained by the Dopplar Effect. Think about how the waves would differentiate between the two observers.

That is, if I am correct at least. I would take my advice with a grain of salt.

3. Jul 23, 2010

### ArtStudentEli

thank you guys a lot! I will take you answers in consideration and it helps a lot by putting me in the right direction for info i need to look up.Thanks again :)

4. Jul 23, 2010

### QuarkCharmer

Anytime,
I'm not sure what course this is for etc. but all the questions pertain to general relativity. You should be able to read the wikipedia (or other) page on the Dopplar Effect and the Coriolis Force/Effect and figure out the solution to those problems.

The Dopplar Effect in particular is a fascinating read anyway. Worth the time.

5. Jul 23, 2010

### dulrich

This is probably asking about gravitational red-shift. Remember that light coming out of a gravitational well appears red-shifted -- light falling into the same gravitational well will appear blue-shifted.
Mach's principle is the conjecture that the inertia of objects is related to mass of the other objects in the universe. How is inertia related to centripetal force, angular momentum, and moment of inertia?
This is the classic set-up to describe the relativity of simultaneity. See http://en.wikipedia.org/wiki/Relativity_of_simultaneity#The_train-and-platform_thought_experiment.
Change implies a progression through time (proper time). Photons never change. Think about this one in relation to the time dilation formula.