# Tag Info

### Could inhomogeneities or topological defects break the fundamental symmetries of the Universe?

The answer to your question is affirmative. In principle, the Poincare invariance may be violated at cosmic scales. A possibility for this may be coming from theories more fundamental than Relativity ...
• 570

### How much of the variance of matter is due to scales

I'll assume $\mathcal{P}(k)$ is the "dimensionless" power spectrum (also known as $\Delta^2(k)$), i.e. $\mathcal{P}(k)\equiv k^3/(2\pi^2) P(k)$. The density variance is \sigma^2=\int_0^\...
• 1,343

### Will the Milky Way galaxy revolve around the Andromeda galaxy or vice versa?

(because we have the supper massive black hole in our Milky Way galaxy) This is not correct. The supermassive black hole is a very small part of the total mass of the galaxy. Then solar system ...
• 103k

### Will the Milky Way galaxy revolve around the Andromeda galaxy or vice versa?

The statement that one thing revolves around another isn't true in a 2-body system. Both objects orbit their common centre of mass. When one object is much more massive than the other, then the centre ...
• 131k
Accepted

### Conditions in the Early Universe

Here are some plots, calculated as described here. I assume no physics beyond the Standard Model and the concordance cosmological model. The temperature The horizontal lines are: The temperature of ...
• 1,343

### What equation tells you how far in space you can go from a point and return?

sten's answer is excellent and beautifully analytical; I just wanted to illustrate the journey and show that neglecting matter (and radiation) is a good approximation. Spacetime diagram To do this, I ...
• 35.6k
Accepted

### What equation tells you how far in space you can go from a point and return?

Preparation Let $a(t)$ be the cosmic expansion factor. Let $x$ be a comoving coordinate, so two objects (like galaxies) that are separating solely due to the expansion of the universe have a constant ...
• 1,343
Different data sets, analysis methods, and statistical interpretations will give different limits on the ratio $\Omega$ between the density and the critical density. However, let's adopt \$\Omega=1....