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Author Topic:   The expanding Universe and Galactic collisions
Rahvin
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Posts: 4032
Joined: 07-01-2005
Member Rating: 9.2


Message 38 of 76 (430100)
10-23-2007 11:55 AM
Reply to: Message 1 by Spektical
10-22-2007 2:24 PM


I have mediocre knoweldge about astronomy and physics, but for some reason the Big Bang theory doesn't quite sit well with me. If according to the BB theory the universe is in fact expanding and bodies of matter are moving away from each other, how do you explain galactic collisions?
Of course one answer could be that the relative mass and proximity of two galactic bodies attract one another to the point of collision. This would also mean that the expansion of the universe is slowing/cooling down.
Another question is: could the universe have originated from a gigantic Black hole, and if so could that be where this universe is heading to?
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?

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

This message is a reply to:
 Message 1 by Spektical, posted 10-22-2007 2:24 PM Spektical has replied

Replies to this message:
 Message 43 by Spektical, posted 10-23-2007 12:55 PM Rahvin has replied
 Message 50 by Kitsune, posted 10-23-2007 3:24 PM Rahvin has replied

  
Rahvin
Member
Posts: 4032
Joined: 07-01-2005
Member Rating: 9.2


Message 49 of 76 (430155)
10-23-2007 3:11 PM
Reply to: Message 43 by Spektical
10-23-2007 12:55 PM


Yes I understand. So just as the north pole is a characteristic of the earth, time is a characteristic of 'this' universe.
More like the way length, width, and height are characteristics of the Universe, but yes.
However, this implies that just like the earth, the universe is a quantified closed system of a different quality.
No, it doesn't, because the Earth is not a closed system. If you mean that the similarity is "North/South is to Earth as Time is to the Universe," I suppose that's a good enough approximation, and you could say that those specific directions (North/South/East/West) are "closed in reference to the Earth as time and the other dimensions are closed in reference to the Universe.
I'm not sure what you mean when you say "of different quality," or that the system is "quantified," however. The Universe encompasses all that exists - that's it's definition (and of course the Universe is a closed system). Other Universes have been hypothesized, most popularly through Brane Theory, but that particular theory is a mathematical hypothesis only. We lack the technology to test any predictions from the hypothesis, and so the existence of other Universes is more of a thought exercise than anything else.
Is it the same as comparing a hydrogen atom to the earth?
I'm not sure what you're getting at here, either. A hydrogen atom can be part of the Earth, but it's not a basic property of the Earth like dimensions are of the Universe.

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

This message is a reply to:
 Message 43 by Spektical, posted 10-23-2007 12:55 PM Spektical has not replied

  
Rahvin
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Posts: 4032
Joined: 07-01-2005
Member Rating: 9.2


Message 51 of 76 (430165)
10-23-2007 3:43 PM
Reply to: Message 47 by Spektical
10-23-2007 2:19 PM


what is the definition of matter?
...anything that has mass and takes up space.

This message is a reply to:
 Message 47 by Spektical, posted 10-23-2007 2:19 PM Spektical has replied

Replies to this message:
 Message 52 by Spektical, posted 10-23-2007 3:44 PM Rahvin has replied

  
Rahvin
Member
Posts: 4032
Joined: 07-01-2005
Member Rating: 9.2


Message 53 of 76 (430174)
10-23-2007 3:59 PM
Reply to: Message 48 by Spektical
10-23-2007 2:39 PM


You said that time is something that belongs to the universe, just like the north pole belongs to the earth. However time does not denote a location or co-ordinate, it denotes itself really. In other words the north pole exists as opposed to the south pole or the equator or the tropic of cancer. You're also saying that the north pole can only be applied to the earth, which means you're limiting yourself to the confines of the earth itself.
The North Pole is to direction as the singularity is to Time. Asking "what is North of the North Pole" is just as meaningless as "What was the Universe like before the singularity." Time is not the pole, it's the direction - it's just another dimension like width and height."
And of course we are limiting the North/South comparison to Earth - North/South/East/West are directions that exist solely on a planetary body that possesses a magnetic field, like Earth.
My question considers that if the universe is in fact expanding in a particular direction, an outward one, then this implies a beginning which denotes a point in time (t=0).
Yes. That's exactly how we extrapolate the existence of the singularity.
But t=0 only applies to the UNIVERSE, not anything BEFORE that.
Again, "before the Universe" is inherently contradictory. The Universe is inclusive of time - asking what came "before" is like asking where a circle begins. The question is meaningless, because at T=0, time has no more meaning than the length or width of a single point. Think Geometry. Time is just another one of the lines like height, width, and length that intersect to describe the set of our Universe. It's only difficult to comprehend because we can only move one-way linearly through time, but can move through the spacial dimensions at will.
Thus time is eternal and there is no beginning.
Kind of. This is the sort of thing best described by mathematics, not the English language, and so any description we can offer is base metaphor. The words "always" and "eternal" typically mean "for all of time," which means something that is eternal exists at every point on the line we could use to represent time. Saying "time is eternal" is like saying "length is infinitely long." That's true, but the English language suggests terms like the word "before" that simply don't exist in this case. "What came before T=0" is exactly like asking "What is shorter than a single point?"

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

This message is a reply to:
 Message 48 by Spektical, posted 10-23-2007 2:39 PM Spektical has replied

Replies to this message:
 Message 56 by Spektical, posted 10-23-2007 4:08 PM Rahvin has replied

  
Rahvin
Member
Posts: 4032
Joined: 07-01-2005
Member Rating: 9.2


Message 54 of 76 (430175)
10-23-2007 4:00 PM
Reply to: Message 52 by Spektical
10-23-2007 3:44 PM


so space can exist without matter?
Of course. Atoms, in fact, are mostly empty space that contains no matter or energy. Simply space.

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

This message is a reply to:
 Message 52 by Spektical, posted 10-23-2007 3:44 PM Spektical has replied

Replies to this message:
 Message 57 by Spektical, posted 10-23-2007 4:12 PM Rahvin has replied

  
Rahvin
Member
Posts: 4032
Joined: 07-01-2005
Member Rating: 9.2


Message 55 of 76 (430176)
10-23-2007 4:01 PM
Reply to: Message 50 by Kitsune
10-23-2007 3:24 PM


That's beautifully worded. You should be writing textbooks LOL.
Thanks!

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 Message 50 by Kitsune, posted 10-23-2007 3:24 PM Kitsune has not replied

  
Rahvin
Member
Posts: 4032
Joined: 07-01-2005
Member Rating: 9.2


Message 58 of 76 (430179)
10-23-2007 4:22 PM
Reply to: Message 56 by Spektical
10-23-2007 4:08 PM


But I wasn't asking this. I am asking what was before the singularity. Did the singularity itself exist in an environment?
The singularity is the environment. It's the Universe. There is nothing "outside" of the Universe - by definition, it encompasses all that exists, including the whole of the dimensions time, width, height, and length. Asking "what came before the singularity" is asking "what was the Universe like before the singularity."
What I am suggesting is infinte largeness as well as infinte smallness.
Infinite largeness and infinite smallness approaches the problem - as you could guess, math can break down when certain values are either infinite or zero (for speed, for instance, time can be neither). The singularity was an infinitely small point, so small that all four dimensions we are consciously aware of were equal to 0. Think Geometry again. A point is dimensionless, and this is why the singularity is so mysterious and interesting - our math breaks down, and we lose our ability to mathematically model its conditions. At t=0, you could simultaneously say that the singularity existed forever, and for only an infinitely small moment.

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

This message is a reply to:
 Message 56 by Spektical, posted 10-23-2007 4:08 PM Spektical has replied

Replies to this message:
 Message 60 by Spektical, posted 10-23-2007 4:32 PM Rahvin has replied

  
Rahvin
Member
Posts: 4032
Joined: 07-01-2005
Member Rating: 9.2


Message 59 of 76 (430180)
10-23-2007 4:27 PM
Reply to: Message 57 by Spektical
10-23-2007 4:12 PM


So did the singularity take up space? And you do have talent for explaining things
Thanks!
As to your answer, again, think of Geometry. We have lines, which denote one dimension, planes, which denote two...and points, which have zero dimensions. The singularity was a single, dimensionless point, where all dimensions were equal to zero. So no, the singularity had no space - that's the whole point. The expansion of space backwards leads us to the point where space was, essentially, nothing, with all that exists occupying the same, single point at once.

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

This message is a reply to:
 Message 57 by Spektical, posted 10-23-2007 4:12 PM Spektical has not replied

  
Rahvin
Member
Posts: 4032
Joined: 07-01-2005
Member Rating: 9.2


Message 61 of 76 (430183)
10-23-2007 4:52 PM
Reply to: Message 60 by Spektical
10-23-2007 4:32 PM


So the singularity is, and always was until it decided to expand? How's that?
There is no "decide," just as there was no "cause." The universe has always been expanding. For as long as time existed, it has been expanding. When time = 0, "cause" is meaningless, because time itself doesn't exist as we know it. You're trying to apply the human linear experience of time, where we move steadily from past to future, to the point at which there was nothing but present. It's comparing apples to oranges.
The singularity existed for only a single point of time. We can say it was infinite, because time really had no meaning when t=0, but it also existed only for an instant, because as soon as t=0.0000...1, the universe was already expanding.
Think of the expansion of the dimension we call time as the very movement of time we experience. As the dimension expands with the others, we move further into the future. When you go all the way back to when t=0, all of our words, "before," "after," "eternal," all become useless.

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

This message is a reply to:
 Message 60 by Spektical, posted 10-23-2007 4:32 PM Spektical has not replied

Replies to this message:
 Message 63 by Phat, posted 10-23-2007 5:15 PM Rahvin has replied

  
Rahvin
Member
Posts: 4032
Joined: 07-01-2005
Member Rating: 9.2


Message 65 of 76 (430200)
10-23-2007 7:05 PM
Reply to: Message 63 by Phat
10-23-2007 5:15 PM


Re: What came first? Creator or Matter?
where did the singularity come from?
Meaningless question. We have no evidence to suggest that the Universe ever did not exist, and plenty of evidence that it does. And as I said previously, the nature of the singularity means that asking for what "came before" it, or what "caused" it are all meaningless questions. You're asking for the origin of a mathematical curiosity theorized by the extrapolation of observed facts back so far that math breaks down. What's farther North than the North Pole, Phat?
was the singularity the uncaused first cause?
The singularity was the state of the universe when time was equal to zero. That is all. It can't have a "cause" because time was zero - "before" zero would have to be negative time, and that doesn't make any sense. We have evidence that the Universe exists, and that the universe existed as the singularity when time=0. Your "uncaused first cause" terminology is meaningless - it's like asking if liquid is a cause.
why do people always ask "who created God"
Because we like to point out the foolhardiness of insisting that everything requires a cause in order to invoke a deity, when the deity itself must be uncaused. We aren't agreeing with you that everything needs a cause, Phat, we're taking your logic to it's conclusion to demonstrate that it's nonsense.
yet seem unable to address "how did the singularity originate"?
The answer is that the singularity is not a "thing." It's the state of the universe when time = 0, as I've said. It's like asking "what is the origin of solid?" We call it "the singularity" because we don't have much of a way to describe it other than "wow, none of our equations work when there all the dimensions = 0 and all matter/energy is packed into a single point."
What you're really asking, Phat, is how the Universe originated. In the earliest state we can describe it, all the way back to T=0, the universe existed as a singularity. It has always existed, for literally all of time.
Humans seem to sit better with explainable and definable origins rather than unexplainable, undefinable (or controllable) origins.
Sure. We like to know what's going on. That's why ancient people made stuff up, like Zeus ruling the sky, or Apollo riding his chariot across the sky as the sun...or a Great Flood, 6-day Creationism, etc.
"I don't know" is an acceptable response to some questions, Phat, and saying "goddunnit" doesn't simplify anything. It adds an extraneous entity into the equation, and fails to answer the question anyway. What came before the singularity? What caused it? The questions, as I've pointed out, are meaningless because they rely entirely on the perspective of time that we experience, when time is actually just another dimension of space.
And this also fits quite nicely with allowing humans to explain their origin...thus creating a theory
No, Phat, that would be "pulling an explanation out of your ass," which is quite a bit different from a Theory. Theories, for example, require evidence. They can be falsified. Using the term in that way is irresponsible.

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

This message is a reply to:
 Message 63 by Phat, posted 10-23-2007 5:15 PM Phat has not replied

  
Rahvin
Member
Posts: 4032
Joined: 07-01-2005
Member Rating: 9.2


Message 69 of 76 (430293)
10-24-2007 10:40 AM
Reply to: Message 68 by jar
10-24-2007 10:31 AM


Re: What came first? Creator or Matter?
Nope, that was a Taz quote.

This message is a reply to:
 Message 68 by jar, posted 10-24-2007 10:31 AM jar has not replied

  
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