## Wednesday, September 26, 2012

### uncertainty and inflation

all fields associated with elementary particles fluctuate on the time scale $\Delta t$ by energies $\Delta E$ which can be estimated to be $>\hbar / \Delta t$ according to the uncertainty principle. Why isn't then the inflation field generating inflationary epochs every time (i.e. nowadays too!) if it acquires enough energy by statistical fluctuation?

## Wednesday, September 19, 2012

### planetary atmospheres

why don't planets lose their atmospheres to outer space? one would assume that the Boltzmann distribution would always allow a certain fraction of molecules to have kinetic energies large enough to overcome the gravitational potential.

bonus question: wouldn't the same thing apply to other gravitationally bound equilibrated systems such as open clusters, globular clusters and galaxies?

## Wednesday, September 12, 2012

### Copernican principle

what ways are there for testing the isotropy and homogeneity of the Universe on large scales? to what extend are those symmetry assumption tested and how would a violation impact on FLRW-models?

## Wednesday, September 5, 2012

### atmospheric pressure on Venus

the atmospheric pressure on the surface of Venus is almost 100 times larger than on Earth, despite the fact that the gravitational acceleration is 10% less. how is that possible?

bonus question: why is the pressure on Mars so low? (actual numbers are $p=6\times10^{-3}$ bar at a third of Earth's gravity)