# Tag Info

## New answers tagged galaxies

12

Observing planets in other galaxies is really hard to do because they are so far away and planets are so small. One of our closest neighbors, the Andromeda Galaxy (also called M31), is about $10^{19}$ km away (just under 780 kpc), so finding a planet the size of Jupiter (roughly $10^5$ km diameter) is pretty tough (radius to distance is very small). Even the ...

2

Galaxies would appear stretched along the line of sight, not jumbled. Let's say a galaxy is ten million light years away and, as you proposed, is 100,000 light years across and we see it nearly edge on. The front of the galaxy will appear to us as it did ten million years ago and the back of the galaxy as it did 10,100,000 years ago. Thus, if the galaxy ...

1

I think the very short answer is: galaxies are very small, indeed tiny, compared to how far away they are, and secondly, compared to the size of the universe. The answer to the spirit of your question, is that simple! "Galaxies are tiny." You're used to hearing "galaxies are 100,000 light years across!" but that's a piffle compared to either the size of ...

0

I suspect that the nice rotational formations of galaxies we see come from galaxies that are oriented in parallel with our solar plane so that the light arrives almost synchronously. Considering we are talking of gravitational forces the "almost" could cover a large window, the distortions not being too great to lose track of the shape. A galaxy whose ...

3

Galaxy rotation happens at a very slow rate (compared to the speed of light). Let's suppose you are observing a galaxy edge-on that the delay from the farthest point is $\Delta t = d/c$, where $d$ is the galaxy diameter. If we take the lag from one extreme point to the other as D: $D = vt = \frac{v}{c}t$ (where $v$ is the rotational speed). You can see ...

0

Let's assume that the anti-matter galaxy is well isolated from galaxies consisting of ordinary matter (you could assume that at the boundary the annihilation reactions would have proceeded very fast and matter and anti-matter don't come into contact at the time we see the anti-mater galaxy). Then the telltale sign would come from supernova neutrinos, ...

-2

Because we can only speculate and guess (although they are very educated speculations and guesses) we don't know anything for certain. In the Universe, anything can happen. Anything. Which is why you never rule something out until you've actually ruled it out- if that makes sense. I'm going to go with Tobias' response that Anti-Matter Galaxies could possibly ...

-2

According to the contemporary but standard mathematics of AIAS.US, a Physics site dedicated to the revision and particularly, the rebuilding of false axioms of physics across the board; and according to my own research [largely consisting of the physical building of 3D models that mimic accordingly, the rotation and dispersion of stellar nebulae about the ...

1

Just remember that a Black Hole doesn't have infinite gravity - it just has however much mass created it in the first place. Yes, anything that gets within the event horizon is trapped forever, but that event horizon will actually be smaller than the size of the equivalent amount of mass composed of ordinary matter. This is also why "microscopic black holes" ...

1

The Jeans equations can be a bit tricky. Their simplest form (in cartesian coordinates, with no particular assumptions) is: $$\frac{\partial\nu}{\partial t}+\frac{\partial(\nu\bar{v_i})}{\partial x_i} = 0$$ \nu\frac{\partial\bar{v_j}}{\partial t}+\nu\bar{v_i}\frac{\partial\bar{v_j}}{\partial x_i} = -\nu\frac{\partial\Phi}{\partial ...

3

Generalizing the term "orbit" to mean some larger object / collection of objects to which the object in question is gravitationally bound, I'd say that the Milky Way "orbits" the Local Group, which in turn "orbits" the Virgo Supercluster. Beyond that, the expansion of the universe starts to dominate over gravitation. There are larger structures than ...

4

The term "orbit" means that an object moves around a point in space on a certain path. Generally, this center point is an object - like your examples - or, in a binary system, a point in space called a barycenter, around which both bodies orbit. The barycenter is located at the system's center of mass. Commonly cited examples of orbiting objects are the ones ...

3

I will select quotes from the wiki article on structure formation, bold mine: The very early Universe In this stage, some mechanism, such as cosmic inflation, is responsible for establishing the initial conditions of the Universe: homogeneity, isotropy and flatness.3[6] Cosmic inflation also would have amplified minute quantum fluctuations ...

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