Galaxy and universe question?

Question

1. what holds a galaxy together? is there like a super giant star in the middle that holds every star system in its gravitational pull or something?

2. if the universe is expanding like a balloon, what is outside of the balloon?

please answer in own words and not too long.

Answer 1

1) The mutual gravitational attraction of all the matter in galaxies holds them together. Imagine a trampoline with lots of bowling balls on it. They would tend to all roll to the center, creating a depression in the trampoline much larger than any one ball alone would.

2) If you consider the closed universe, I would think this means that there is a higher dimension of space that we simply cannot interact with, and our universe is the 3-dimensional sheet wrapped around in 4 (or more) dimensions. Imagine a fiberoptic cable being bent around. Inside the fiber, to the light there is only "forward" and "backward" and bends in the cable appear simply as regions more difficult to traverse than regions where it's straight.

If it's an open universe, it's even harder to grasp. In this case, space is just getting larger - just because something's infinitely large doesn't mean it contains everything. (weird but true). Consider the set of positive integers: 1,2,3,4,5..... it's infinite, but there are lots of numbers not included in it. If this set were to start gaining negative integers one at a time, it would be expanding, but it would be no more or less infinitely large than it was when you started with just the positive integers.

Bizarre, but true!

Answer 2

Many are confused.To understand u need simple language and for that then see!!! 1)A system of millions or billions of stars, together with gas and dust, held together by gravitational attraction. 2)All existing matter and space considered as a whole; the cosmos. The universe is believed to be at least 10 billion light years in diameter and contains a vast number of galaxies; it has been expanding since its creation in the big bang about 13 billion years ago. 3) Not understood yet? ans:- A galaxy is a collection of billions of stars. The galaxy that Earth and our Sun is in is called the Milky Way Galaxy. Now if you can imagine, there are billions of galaxies as well. The universe is like the giant container of all the galaxies. THUS, u can imagine that galaxy is small whereas the universe is so big! Hope you understood. google and yahoo answers resolved questions.

Answer 3

It is likely that most galaxies have a large black hole at their center, but this is not enough to hold the stars together. Neither is the mass of the stars enough, which is why the existence of 'dark matter' is postulated out of necessity. Dark matter could in fact compose as much as 90% of the universe!

The *entire* universe is expanding, and that includes space itself - there is no outside or that would be part of the universe too. So the universe is expanding only "kind of" like a balloon.

Answer 4

The gravity of all the stars and dust in a galaxy holds it together. The black hole in the center, if there is one, is a very very very small part of the galaxy.

The universe is NOT expanding like a balloon. That story is often told, but it is misleading. The universe is not expanding "into" anything, and there is no "outside" of the universe. The universe is expanding, because the space between super-clusters of galaxies is expanding; so the universe is expanding into itself.

Super-cluster = a group of 1000's of galaxies.

Answer 5

Unfortunately I have no idea how to answer either question, but I do have a comment on #2.

#2 is a misconception -- the universe is not "expanding like a balloon". The universe is (at least) 3-dimensional and the surface of a balloon is 2-dimensional.

Some elementary articles say that the universe is expanding like a balloon because they are trying to come up with an illustration that sort-of resembles what's happening. The true concept is that two objects in the universe, even if they are at rest relative to each other, will get farther and farther apart, not because they're moving, but because space itself is stretching and all distances are getting larger. It's sorta similar to two ants on the surface of an inflating balloon, but it's really quite different because of 2-d vs. 3-d.

Answer 6

1. galaxies are held together by the combined mass of the stars, which may or may not include a larger mass in the middle, maybe a black hole.
The stars themselves have been calculated not to be enough to hold stars together. this was a bit of a mystery for a while, and dark matter was invented to explain the problem. Later, dark energy (energy with mass) was also proposed. Identifying the dark matter and energy has proved vaguely successful.

2. there is no such thing as outside the universe bubble, let alone anything there.

for more information, My source is a good book.

Answer 7

1. mostly the black hole in the center of most galaxies. also the combined gravity of the stars and dark matter.

2. one of the most popular theories if that the universe is 4 dimensional, so it has an end but the end would just bring you back to the beginning. because if space was created by the big bang it has to have speed, which means it has an endpoint, which means there has to be something outside of it, and there cant be because theres no space. and there cant just be a point where you cant go any further, like a big wall at the end of space, thats idiotic. so basically the idea is that its a hypersphere, so once you reach the end you also reach the beginning.

Answer 8

The Lord holds the universe together.

Answer 9

1.) Currently, we think there is a black hole at the center of most galaxies. Other than that, the collective mass of all the starts would basically hold each other in place relative to each other.

2.) Nothing

Answer 10

i dont want to waste your time as u have mentioned
morningfoxnorth is right
i have starred your question because its too gooooooood!!!!!