can you formulate the speed and acceleration of a FLRW-universe in human-understandable units? what would be your favourite choice?

# cosmology question of the week

CQW is an educational resource for theoretical astrophysics and cosmology. we post a new question every week for students to get and for teachers to stay in shape.

## Wednesday, January 28, 2015

## Wednesday, January 21, 2015

### Einstein's grandfather clock

the Einstein clock is a set of parallel mirrors with a flash of light bouncing between the mirrors serving as a pendulum. it is a particularly nice way of illustrating time-dilation in special relativity. how would the path of the flash of light look like if the Einstein clock was inside a gravitational field (or was accelerated)?

## Wednesday, January 14, 2015

### fine structure for Keplerium

we wish all CQW-readers a happy New Year 2015:

Keplerium is a gravitationally bound atom with angular momentum quantisation identical to the Bohr-model for atoms. can you draw analogies between atomic fine structure and gravitomagnetic effects arising in weak-field relativity?

Keplerium is a gravitationally bound atom with angular momentum quantisation identical to the Bohr-model for atoms. can you draw analogies between atomic fine structure and gravitomagnetic effects arising in weak-field relativity?

## Wednesday, December 17, 2014

### inertial forces and mechanical work

can you perform work against the centrifugal force? what about the Coriolis-force?

CQW wishes our readers a Merry Xmas and a happy New Year 2015, and we hope to welcome you back on the 14.Jan.2015. if you want to contribute to CQW, please drop us a mail at cosmologyquestionoftheweek["AT"]gmail["DOT"]com.

CQW wishes our readers a Merry Xmas and a happy New Year 2015, and we hope to welcome you back on the 14.Jan.2015. if you want to contribute to CQW, please drop us a mail at cosmologyquestionoftheweek["AT"]gmail["DOT"]com.

## Wednesday, December 10, 2014

### Eddington-limit for muons

the Eddington-limit is defined as the luminosity where gravity is balanced by radiation pressure. imagine now that an astrophysical object contains muons instead of electrons: would the Eddington-limit be higher or lower?

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