The expanding Universe and Galactic collisions

lol.So if the universe is unbounded than its not expanding. And if its not expanding than there is a different reason or cause for the movement of galactc bodies. This again brings me to my original question if everything is moving away from everything else, than why or how is andromeda is on a collision course with the Milky way?

There is no "outside the universe"; the concept is meaningless.

Imagine a big sheet of rubber being stretched. Now imagine two ants crawling towards each other across that sheet. Each point on the sheet is moving away from each other, but the ants are moving with respect to those points. Providing the ants are crawling faster than they're being moved apart by the sheet they can still reach each other.

ok I understand that the galaxies are moving faster than the universe' rate of expansion thus they're getting closer to each other, which makes sense. However, why is it meaningless to think of a medium outside the universe? I mean if 'something' is expanding, then it must be quantified. Maybe I'm misconceiving the universe itself. It just doesn't make any sense to me that u can use the baloon example and refute the idea of quantity.

Vacuum appears to be the likely candidate for this. The expansion of the universe isn't just about the materials of the universe expanding, but the 'bubble' that contains the universe as well. (I am sure someone will crawl up my ass for that term.) As the outer reaches of the universe move away, there is emptiness that grows larger. Before someone else says it, I know there can never really be 'nothing' in physics(see below). That vacuum pulls the matter of the observable universe outward.Dark energy may be vacuum | EurekAlert!

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"Debate is an art form. It is about the winning of arguments. It is not about the discovery of truth. There are certain rules and procedures to debate that really have nothing to do with establishing fact ” which creationists have mastered. Some of those rules are: never say anything positive about your own position because it can be attacked, but chip away at what appear to be the weaknesses in your opponent's position. They are good at that. I don't think I could beat the creationists at debate. I can tie them. But in courtrooms they are terrible, because in courtrooms you cannot give speeches. In a courtroom you have to answer direct questions about the positive status of your belief. We destroyed them in Arkansas. On the second day of the two-week trial we had our victory party!"
-Stephen Jay Gould

Please don't be another "I don't understand it, ergo God (of the Christian bible)"Because you don't understand something, it doesn't follow that its not understood.

Agreed..That's why I posted the OP. Its stimulating discussing these things with you guys and girls.Edited by Spektical, : No reason given.

Hi Skektical,It looks like you're taking the simplified, made-for-TV version of the Big Bang theory a little too seriously.The model of the Big Bang taught up to High School levels is drastically simplified for consumption by chinldren with very little or no prior physics training, and it takes at most a week of 45-minute classes or so for the entirety of its instruction.Popular media portrays the Big Bang even worse - TV documentaries like on the Science channel, or in some of the more popular "science" magazines, dumb it down a lot so that the average person can grasp the basics, and they try to cram the whole thing into an hour (including commercials!) or a few paragraphs. This just isn't possible.When you say you think the Big Bang Theory is far too simple to account for the modern universe...well, if you're referring to the way the Big Bang is taught in high school or lower, or the way it's portrayed on TV, you'd certainly be correct.Oh...and even the term "Big Bang" is inaccurate. It was coined by a scientist who opposed the model when it was first hypothesized, as a way to ridicule it. It was catchy, so it stuck.The reality of the Big Bang is something more complex than a simple "explosion from nothing," like some ridiculous ex nihilo stick of dynamite springing everything into existence.The universe has been observed to be expanding. The greatest evidence for this is the redshift in the light spectrum of distant stars (its something like the doppler effect, which you can hear at a race trach - the frequency of the sound coming from the cars is noticibly different depending on whether the car is coming toward you or away from you. Light behaves the same way). But this doesn't just mean galaxies are moving away from each other, like from an explosion. Think of space and time itself as a balloon that is slowly being blown up, and all matter is a series of dots on the balloon. As the balloon (space and time) expands, the dots (matter) will move farther and farther apart. This is the expansion of the universe, and it is essentially a direct observation. The singularity, the single point from which the universe spread, is not a location, or really an object - it's an extrapolation to a point at which our math can no longer be used to model anything. Basically, we extrapolate the expansion backwards and say "if everything is expanding, then a long, long time ago everything must have been closer together becasue space was 'smaller.' If we go back far enough, everything must have been in a single, dimentionless point!" In this point, there would be no length, no width, no time (which is just another dimention like the others), and so equasions like (speed = distance/time) suddenly look like (x = 0/0), which is mathematically impossible. This is why the singularity is so odd, and where it gets it's name - it's the point at which math as we know it would no longer make sense.I also mentioned ex nihilo. The way cosmic origins are most commonly explained, it does indeed sound like scientists propose that the universe came from nothing. This isn't true. The universe existed as the singularity and expanded from there. It has always existed - remember that time is another dimention just like the spacial ones. Time existed as a single point in the singularity, just as the other dimensions did. Asking what came "before" this point is like asking what is north of the North Pole - the question is flawed, becasue the term "before" refers to a point earlier in time. For all of time, the universe has been expanding from a singular point. Asking what came "before" that is meaningless, because time had no meaning in the singularity, when all dimensions would have been 0, and single point. This is probably the most difficult of the concepts to grasp.That just takes care of the expansion of space/time. Your next question is likely "if everything is moving apart, then why do galaxies collide? Why do they even form?"That's an excellent question, and once again it springs from an oversimplified model. The expansion of the universe is not nearly the only force at work. We have the Strong and Weak Atomic forces, the Electromagnetic force, and Gravity, all of which involve matter acting upon other matter, pushing and pulling all at the same time with different strengths. Gravity, of course, is the most relevant over stellar distances. Gravity is what causes the formation of stars and galaxies. To expand on our balloon model, imagine "tying" our dots together with some sort of string holding them together. The dots that are connected will stay together, while the ones not connected will move away from the expansion. Gravity is more complex than that, of course, but this is why everything isn't just moving apart. Sometimes gravity is not strong enough to cause two bodies to draw in to each other, or enter an orbit - we use this in space exploration all the time, to "slingshot" probes using the gravity of planets. This also happens with larger bodies like galaxies, and can cause near-misses to completely redirect both bodies.There's far, far more to it than this. But the basic misconception that the Big Bang was an "explosion" is an inaccuracy propagated by popular TV, simplified education, and the name of the Theory itself. That inaccuracy is what causes the most misunderstanding in those who think about it further, like you have.Does that help?

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

Your question starts with a false premise, that the big bang starts with a black hole. This is in fact wrong. FAQ in cosmologyViasat Internet New York | Satellite Internet Provider NY For a starting point. Mediocre doesn't begin to describe you knowledge of Cosmology(and Astronomy) or physics.

So many questions...We cannot speak of energy without matter and matter without energy. The two are interchangable. When cosmologists refer to dark energy, they are referring to the missing roughly 2/3 of the overall energy observed in the visible universe.Let's summarize how how all of these mumble jumbles came about. In the 20's and 30's, Fritz Zwicky painstakingly observed and calculated the revolution of the stars in relative of the galactic center. Now, remember that he had to do all of these without modern computers to do the calculations for him. Anyhow, what he found was that the galaxies were behaving more like a solid object than what the laws of gravity tell us.Imagine it this way. If you have a solid disk and you rotate it, every point on the disk would have the same angular velocity with each other. If you look at a planetary system like our solar system, you find that the farther out an object is from sol, the slower its angular velocity is. The stars of the galaxy, however, almost have the same angular velocity as each other. From what we know of gravity, the further the stars are from the galactic center the slower it should be travelling. In other words, there must be a hell of a lot more mass in the galaxy than what we can see, mainly the stars.Not counting the non-visible baryonic matter like MACHOs and WIMPs, there is still 2/3 of the total mass missing. Hence, we call it dark matter because we don't have a clue what it is.I believe it was in 1996 or 98 that 2 independent astro groups attempted to calculate the rate of expansion of the universe by tracing the rate of recession of certain super novas. They discovered that not only is the universe expanding, it is expanding at an accelerated speed.But hang on. We know of 4 fundamental forces in the universe. The strong nuclear force, the weak nuclear force, gravity, and electromagnetism. So, what's responsible for the accelerated rate of expansion? Is there another force we don't know about, some kind of repulsion force?The energy responsible for the outward acceleration is called dark energy because, like dark matter, we can observe what it does but we don't have a clue what the hell it is. At this point in time, we might as well attribute it to the tooth fairy.Now, it had been known for a very long time that if there was enough matter in the universe gravity will eventually win out and the universe will begin to contract. If, however, there isn't enough matter in the universe then the expansion will continue on forever. The discovery of accelerated rate of expansion pretty much told us what it's gonna be.PS - Jon, sometimes I wonder how you are able to pass your English classes. Your reading comprehension is sometimes impressively lacking.Added by edit.To add to what Rahvin was saying, if I were to explain the BB to you in a less popularized way, I'd have to fill this forum up with math equations. Even what we have explained to you so far doesn't even come close to how this info would be presented in physics 101 (let alone upper classmen level). Just remember this much. These theories didn't just come out of people's asses. We are oversimplifying whole lifetimes' work here.Edited by Taz, : No reason given.

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Disclaimer:

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Occasionally, owing to the deficiency of the English language, I have used he/him/his meaning he or she/him or her/his or her in order to avoid awkwardness of style.

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He, him, and his are not intended as exclusively masculine pronouns. They may refer to either sex or to both sexes!

Because the universe is by definition all things and all wheres that obey the same natural laws that we observe. If you want to wander outside of the universe, go right ahead. Noone is going to stop you. In fact, I dare you to. Ask yourself this question. Can you at least conceptualize more than the 3-dimensional space you live in plus time? You are having trouble conceptualizing this stuff because, as the borg queen once said to Captain picard, "You think in such 3 dimensional term."

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Disclaimer:

​

Occasionally, owing to the deficiency of the English language, I have used he/him/his meaning he or she/him or her/his or her in order to avoid awkwardness of style.

​

He, him, and his are not intended as exclusively masculine pronouns. They may refer to either sex or to both sexes!

how can the universe be unbounded if that means its endless, and there is no outside of it because of thisThat means the universe expands into nothing. But then what is that nothing that it is expanding into, since there can't exist a place where there truly is "pure nothing"

Yes I understand. So just as the north pole is a characteristic of the earth, time is a characteristic of 'this' universe. However, this implies that just like the earth, the universe is a quantified closed system of a different quality. Is it the same as comparing a hydrogen atom to the earth?

Time is not a tangible thing..its a unit of measure. It should be applied to anything. But if the universe always existed, then time is irrelevant and non-existant.

Just because the universe always existed, it doesn't follow that all the matter in the universe always existed. This seems to be the primary cause of your misunderstanding.-x