|
| Thread: Some facts |  This thread is pages long: 1 2 · NEXT» |
|
Seraphim
Supreme Hero
Knowledge Reaper
|
posted March 12, 2011 06:41 PM |
bonus applied by angelito on 13 Mar 2011. |
Edited by Seraphim at 19:01, 12 Mar 2011.
|
Some facts
http://www.cfa.harvard.edu/seuforum/faq.htm#top
I encourage everybody to check this.It is really nice and educative.
WARNING wall of text...
Structure of the Universe
Does the Universe have an edge, beyond which there is nothing?
Galaxies extend as far as we can detect... with no sign of diminishing.There is no evidence that the universe has an edge. The part of the universe we can observe from Earth is filled more or less uniformly with galaxies extending in every direction as far as we can see - more than 10 billion light-years, or about 6 billion trillion miles. We know that the galaxies must extend much further than we can see, but we do not know whether the universe is infinite or not. When astronomers sometimes refer (carelessly!) to galaxies "near the edge of the universe," they are referring only to the edge of the OBSERVABLE universe - i.e., the part we can see.
Are the galaxies arranged on the surface of a sphere?
No. Galaxies are not actually arranged on the surface of a sphere. Many students and teachers mistakenly believe that the galaxies in the universe are arranged on the surface of a sphere. One origin of this misconception is the common demonstration of blowing up a balloon to model the expansion of the universe. Another is the (mistaken) belief that during the Big Bang, matter expanded into space from a point (see below). A third is the finding that many clusters of galaxies appear to be arranged around the outside of "bubble-like" voids in the universe. But on the largest scales that astronomers have observed, each chunk of space appears to have just as much matter as any other equivalent chunk.
Why can't we see the whole universe?
We can see just about as far as nature allows us to see. Two things prevent us from seeing further. First, the universe has been evolving with time. Stars and galaxies did not always exist. Therefore light from MOST of the galaxies in the universe has not yet had time to reach us. Second, the universe has been expanding with time. Again, light from MOST of the universe has not yet had time to reach us.
If you could suddenly freeze time everywhere in the universe, and magically survey all of creation, you would find galaxies extending out far beyond what we can see today. But how far, no one knows.
Does the term "universe" refer to space, or to the matter in it, or to both?
Just a hundred years ago, scientists thought of the universe in terms of matter. Space was just the "emptiness" in which matter lived.
Today, the situation is reversed. During the twentieth century, scientists learned that space is not "nothingness." First, Einstein showed that space has structure: It is flexible and can be stretched. (In fact, when astronomers talk about the "expansion of the universe," they are referring to the stretching of space between clusters of galaxies - NOT to the motion of galaxies through space.) Later, scientists found other properties of space. For example, matter and anti-matter are routinely created in the laboratory from space itself (and an energy source); the kinds of particles that can exist reflect the structure of space. In fact, there is now evidence that space itself MAY possess some slight amount of energy of its own, of a form previously unknown. If so, space may actually have weight!
Discovering the properties of space remains one of the deepest and most important problems in modern science.
Evolution of the Universe
Did the Universe expand from a point? If so, doesn't the universe have to have an edge?
No. The Big Bang was not an explosion IN space. It was a process that involved ALL of space. This misconception causes more confusion than any other in cosmology. Unfortunately, many students, teachers, and scientists(!) mistakenly picture the "Big Bang" as an explosion that took place at some location in space, hurtling matter outward.
In reality, ALL of space was filled with energy right from the beginning. There was no center to the expansion, and no magical point from which matter hurtled outward. The confusion arises in part because of the amazing conclusion that the OBSERVABLE portion of the universe was once packed into an incredibly tiny volume. But that primordial pellet of matter and energy was NOT surrounded by empty space... it was surrounded by more matter and energy (which today is beyond the region we can observe.) In fact, if the whole universe is infinitely large now, then it was always infinite, including during the Big Bang as well.
To put it another way, the current evidence indicates only that the early universe - the WHOLE universe - was extremely DENSE - but not necessarily extremely small. Thus the Big Bang took place everywhere in space, not at a particular point in space.
Then where did the idea that the universe was once a point come from?
For much of the twentieth century, astronomers and physicists believed that space might NOT be infinitely large - that is, space might actually curve around on itself to form a "closed universe." This unusual three-dimensional shape was discovered in the mid-1800's by the great mathematician Bernhard Riemann. The shape was later favored by Einstein as a possible shape for the universe. Such a closed universe would have a finite volume, yet no boundaries or edges. Although closed universes cannot be visualized from the outside, they CAN be visualized from the inside. For example, the image at right gives an idea of what a tiny closed universe might look like. (In a real closed universe, you cannot see the back of your head, the way you can here.) If you shrink such a space down, then everything in it gets closer together, and the volume of the closed universe gets closer and closer to zero. But there is still nowhere OUTSIDE the space for an observer.
Current evidence shows that our part of the universe appears not to be curved. This tells us that either the universe is infinitely large, or else is so large that we cannot detect its curvature from the tiny portion we can observe -- just as we could not tell that the Earth was curved if our measurements were confined to a sandbox!
If the universe started out so dense, why didn't it collapse into a black hole?
A large enough clump of matter will collapse to form a black hole, but ONLY if it is surrounded by (relatively) empty space. During the Big Bang, there WAS NO empty space: ALL of space was filled more or less uniformly with matter and energy; there was no "center of attraction" around which matter could coalesce. Under these circumstances, a cosmic-scale black hole will not form (and lucky for us!).
Why does looking out in space mean looking back in time?
Because it takes time for light from distant objects to reach us. We see the sun as it looked about 8 minutes ago... other stars as they looked years ago... and distant galaxies as they looked millions or even billions of years ago.
I've heard the expansion of the universe may be speeding up. Is there an "anti-gravity" force?
Current studies of distant exploding stars have led astronomers to conclude that the universe is not only expanding - the expansion may be accelerating with time. This is not due to an "anti-gravity force" but rather to gravity itself. In fact, the effect was predicted as a possibility on the basis of Einstein's theory of gravity.
(It may seem strange that gravity can be "repulsive" as well as attractive. The secret is that the expansion applies to the fabric of space itself - not to the matter within it; space behaves very differently from matter. For example, no chunk of matter can travel through space at the speed of light. Yet SPACE itself can expand faster than the speed of light. Similarly, while matter is attracted to other matter by gravity, space behaves differently: Space can either expand or contract as a consequence of gravity.)
More about the Big Bang
When they say "the universe is expanding," what exactly is expanding?
As bizarre as it may seem, space itself is expanding - specifically, the vast regions of space between galaxies.
But if you can't see space, or feel it or touch it - how can it be expanding?
According to Einstein, space is not simply emptiness; it's a real, stretchable, flexible thing. In fact, understanding the properties and behavior of space is a major goal of modern physics.
Why did anyone ever think that space should be expanding? Isn't it a far-fetched idea?
The notion that space is expanding is a prediction of Einstein's theory of gravity, which describes a simple but universal relationship between space, time, and matter. But it was a prediction that Einstein didn't believe; in fact, he tried to modify his theory to get rid of it.
Then how do we know that space really is expanding?
In the late 1920's, the astronomer Edwin Hubble first observed that distant galaxies are moving away from us, just as would be expected if the space between galaxies were growing in volume - and just as predicted by Einstein's theory of gravity. Since then, astronomers have measured this recession for millions of galaxies. But there's other evidence as well.
Are the galaxies in the universe moving through space?
No, the galaxies sit more or less passively in the space around them. As the space between galaxies expands, it carries the galaxies further apart - like raisins in an expanding dough.
But I heard that our Milky Way galaxy may one day collide with a neighboring galaxy. If galaxies are all moving apart from each other, how can they collide?
The universe is a chaotic place - and the gravity from one galaxy, or from a group of galaxies, may disturb the motion of its near neighbors, causing them to collide. However, on average, when you compare two large enough chunks of space, the galaxies in one are moving away from the galaxies in the other.
Where did the Big Bang scenario come from?
If space (and everything with it) is expanding now, then the universe must have been much denser in the past. That is, all the matter and energy (such as light) that we observe in the universe would have been compressed into a much smaller space in the past. Einstein's theory of gravity enables us to run the "movie" of the universe backwards - i.e., to calculate the density that the universe must have had in the past. The result: any chunk of the universe we can observe - no matter how large - must have expanded from an infinitesimally small volume of space.
How do we know when the Big Bang took place?
By determining how fast the universe is expanding now, and then "running the movie of the universe" backwards in time, using Einstein's theory of gravity. The result is that space started expanding about 15 billion years ago, give or take a few billion years. This number is uncertain, in part because of uncertainties in our current measurements of how fast the universe is expanding, how much matter and energy there is, and even what kind of energy there is in the universe.
Do we know where, in space, the Big Bang took place?
It's a common misconception that the Big Bang was an "explosion" that took place somewhere in space. But the Big Bang was an expansion of space itself. Every part of space participated in it. For example, the part of space occupied by the Earth, the Sun, and our Milky Way galaxy was once, during the Big Bang, incredibly hot and dense. The same holds true of every other part of the universe we can see.
Artists may find it more dramatic to draw a "fireball" expanding into space, but as far as we know, there would have been no such "ball."
How do we know there really was a Big Bang?
As mentioned above, we observe that galaxies are rushing apart in just the way predicted by the Big Bang scenario. But there are other
Astronomers have detected, throughout the universe, two chemical elements that could only have been created during the Big Bang: hydrogen and helium. Furthermore, these elements are observed in just the proportions (roughly 75% hydrogen, 25% helium) predicted to have been produced during the Big Bang. This prediction is based on our well-established understanding of nuclear reactions - independent of Einstein's theory of gravity.
Second, we can actually detect the light left over from the era of the Big Bang. The blinding light that was present in our region of space has long since traveled off to the far reaches of the universe. But light from distant parts of the universe is just now arriving here at Earth, billions of years after the Big Bang. This light is observed to have all the characteristics expected from the Big Bang scenario and from our understanding of heat and light.
But I've heard on the news there are problems with the Big Bang theory. Is it still just a "theory"?
The Big Bang is actually not a "theory" at all, but rather a scenario about the early moments of our universe, for which the evidence is overwhelming. But the Big Bang scenario cannot be the whole story, and its details are a subject of intense research.
Was the Big Bang the origin of the universe?
It is a common misconception that the Big Bang was the origin of the universe. In reality, the Big Bang scenario is completely silent about how the universe came into existence in the first place. In fact, the closer we look to time "zero," the less certain we are about what actually happened, because our current description of physical laws do not yet apply to such extremes of nature.
The Big Bang scenario simply assumes that space, time, and energy already existed. But it tells us nothing about where they came from - or why the universe was born hot and dense to begin with.
Are there theories that go beyond the Big Bang?
Yes, there are theories that build on the Big Bang scenario by adding insights from physics about the structure of space itself. Watch this space for more details.
|
|
Adrius
Honorable
Undefeatable Hero
Stand and fight!
|
|
posted March 12, 2011 07:14 PM |
|
Edited by Adrius at 19:15, 12 Mar 2011.
|
Very interesting.
One thing I don't get though..
What was beyond the pre-Big Bang blob of matter? Nothing? Then the universe was not infinite before the Big Bang.
Was space beyond it? Then it should've collapsed into a black hole, not gone Big Bang.
Was in fact the entire infinite universe as dense as the "blob"? Then where the hell did all this energy/matter go since the universe is less dense now? If there was no space to expand, then the density couldn't decrease either.
EXPLAIN TO ME!
____________
|
|
Seraphim
Supreme Hero
Knowledge Reaper
|
|
posted March 12, 2011 07:41 PM |
|
|
|
Doomforge
Admirable
Undefeatable Hero
Retired Hero
|
|
posted March 12, 2011 07:44 PM |
|
|
Great post
Human knowledge does seem pretty funny however. We either have magical creatures creating people or lands from clay or air, or infinite mass of eternal nothing that "explodes" into magical something. 
____________
We reached to the stars and everything is now ours
|
|
VokialBG
Honorable
Legendary Hero
First in line
|
|
posted March 12, 2011 08:01 PM |
|
|
There must be other universes outside the univers
Quote:
What was beyond the pre-Big Bang blob of matter? Nothing?
Also how the "nothing" looked like  There is no such thing as nothing in our known words. There is at least air and free space. What's a nothing?
____________
|
|
ohforfsake
Promising
Legendary Hero
Initiate
|
|
posted March 12, 2011 08:13 PM |
|
|
Quote:
What was beyond the pre-Big Bang blob of matter? Nothing? Then the universe was not infinite before the Big Bang.
Quote:
But that primordial pellet of matter and energy was NOT surrounded by empty space... it was surrounded by more matter and energy (which today is beyond the region we can observe.)
As far as I know. The observable universe (using the word universe here, as meaning everything there is) is defined as that region of universe we can actually observe, i.e. measure upon.
As such, I believe, any question that is to do with a region outside the observable universe is not a question science can answer.
However. If that region should be once found measureable. Then said question would be answerable by science. Though then it would not be a question about the parts outside of the observable universe anymore.
____________
Living time backwards
|
|
Adrius
Honorable
Undefeatable Hero
Stand and fight!
|
|
posted March 12, 2011 08:16 PM |
|
Edited by Adrius at 20:16, 12 Mar 2011.
|
I don't really care if it falls into the category of science or not, that's just a word.
And yeah I read that part, which was why I also asked:
Quote:
Was in fact the entire infinite universe as dense as the "blob"? Then where the hell did all this energy/matter go since the universe is less dense now? If there was no space to expand, then the density couldn't decrease either.
____________
|
|
ohforfsake
Promising
Legendary Hero
Initiate
|
|
posted March 12, 2011 08:26 PM |
|
|
Religion is also just a word! I don't get your point about that one, but nevermind.
I don't know what can expand through what or if we know all possible components. I mean, one infinity can be bigger than another...
____________
Living time backwards
|
|
Corribus
Hero of Order
The Abyss Staring Back at You
|
|
posted March 12, 2011 08:55 PM |
|
|
Quote:
What was beyond the pre-Big Bang blob of matter? Nothing? Then the universe was not infinite before the Big Bang.
As I've stated here before, this question is based on the potentially misleading assumption that there was a before. If time started at the moment of the Bang, then there was no before. Hence, the question fundamentally makes no sense. It would be, to my mind, equivalent to asking what lies north of the North Pole.
|
|
Adrius
Honorable
Undefeatable Hero
Stand and fight!
|
|
posted March 12, 2011 09:01 PM |
|
|
I have a hard time grasping the non-existance of time but I think I get what you're saying...
So if there is no flow of time, there is no movement or any reactions, and thus the Big Bang would be hard to explain... and that's where quantum physics come in...
Which I also have a hard time grasping. I kinda like cause and effect, things shouldn't just happen randomly.
____________
|
|
ohforfsake
Promising
Legendary Hero
Initiate
|
|
posted March 12, 2011 10:55 PM |
|
|
For what I know. Time, as we know it, starts at the moment of the big bang. The cause of the Big Bang, if such exists, is unknown.
To my knowledge. Quantum mechanics doesn't offer a possible cause for the big bang either. Though I could be wrong of course.
I believe string theory offers a possible cause for the Big Bang, but not only is that theory not really testable as of yet, it also, to my knowledge, merely substitutes the problem from a big bang into some membranes.
Then again. I don't really know very much about string theory at all.
____________
Living time backwards
|
|
Zenofex
Responsible
Legendary Hero
Kreegan-atheist
|
|
posted March 12, 2011 11:06 PM |
|
|
The greatest difficulties when one tries to comprehend all this arise from the inherently limited human perception which always seeks patterns and borders, at least in this stage of its evolution. I guess the mathematics is the primary way to make a good description of the universe as it only has the right tools for the purpose - for the time being at least. That is not to say that it is the only way.
Quote:
I mean, one infinity can be bigger than another...
No, it can not. "Small" and "big" and respectively their superlative degrees can be applied only to finite objects. The infinite has no size or shape, it can not be measured - if it can, then it is not infinite.
|
|
ohforfsake
Promising
Legendary Hero
Initiate
|
|
posted March 12, 2011 11:21 PM |
|
|
Quote:
Quote:
I mean, one infinity can be bigger than another...
No, it can not. "Small" and "big" and respectively their superlative degrees can be applied only to finite objects. The infinite has no size or shape, it can not be measured - if it can, then it is not infinite.
Check out Hilberts Hotel!
A simple example. Between 0 and 1, there are infinite many real numbers. No doubt there are double as many real numbers between 0 and 2, also infinite.
The infinite amount of real numbers between 0 and 2 is twice as big as the infinite amount of real numbers between 0 and 1.
The amount of complex numbers between any two random numbers are infinitely larger than the amount of real numbers between the same two values.
The amount of real numbers between any two random numbers are infinitely larger than the amount of rational numbers between the same two values.
The amount of rational numbers between any two random numbers are infinitely larger than the amount of natural numbers between the same two values.
[Complex number is a number on the form a+ib, where a and b are real numbers and i is the squareroot of negative 1]
[Real numbers are all possible numbers you can compose of 0,1,2,3,4,5, etc. Like 0,134 is a real number and 0,1354341413 is a real number and 58459284234 is a real number]
[Rational numbers are all numbers you can form by taking x / y, where x and y are natural numbers. An example of a real number, a non-rational number is the squareroot of 2, pi, etc.]
[Natural numbers are all the numbers you can count in positive and negative direction, including zero, i.e. stuff as 1, 2, 3, 4 and 9134134 and -234, etc.]
____________
Living time backwards
|
|
Zenofex
Responsible
Legendary Hero
Kreegan-atheist
|
|
posted March 13, 2011 12:19 AM |
|
Edited by Zenofex at 00:20, 13 Mar 2011.
|
Quote:
A simple example. Between 0 and 1, there are infinite many real numbers. No doubt there are double as many real numbers between 0 and 2, also infinite.
I don't think the example is correct. The "infinite" you are talking about is actually quite finite. To have double the amount of "infinite" numbers between 0 and 2 in comparison with the amount of numbers between 0 and 1, you have to know what is the amount of numbers between 0 and 1, i.e. to have a finite quantity which is to be "doubled". You can't double something which has no finite value just like you can't double nothing - which also has no finite value (except maybe 0, which is paradoxical number, but I'm not willing to enter the area of the hardcore mathematics which is totally dark for me). Otherwise you are presuming the existence of a border which contradicts the notion of infinity.
|
|
baklava
Honorable
Legendary Hero
Mostly harmless
|
|
posted March 13, 2011 12:41 AM |
|
|
Sometimes I feel like the relationship between cosmic origin theoreticians and mathematicians is similar to that of modern architects and construction engineers. The former are there to come up with all kinds of weird and silly stuff and the latter are expected to somehow make that possible.
____________
"Let me tell you what the blues
is. When you ain't got no
money,
you got the blues."
Howlin Wolf
|
|
baklava
Honorable
Legendary Hero
Mostly harmless
|
|
posted March 13, 2011 12:49 AM |
|
|
Quote:
The infinite amount of real numbers between 0 and 2 is twice as big as the infinite amount of real numbers between 0 and 1.
Also if the Earth is round, how come nothing's upside down in Australia.
____________
"Let me tell you what the blues
is. When you ain't got no
money,
you got the blues."
Howlin Wolf
|
|
del_diablo
Legendary Hero
Manifest
|
|
posted March 13, 2011 02:06 AM |
|
|
Quote:
Quote:
A simple example. Between 0 and 1, there are infinite many real numbers. No doubt there are double as many real numbers between 0 and 2, also infinite.
I don't think the example is correct. The "infinite" you are talking about is actually quite finite. To have double the amount of "infinite" numbers between 0 and 2 in comparison with the amount of numbers between 0 and 1, you have to know what is the amount of numbers between 0 and 1, i.e. to have a finite quantity which is to be "doubled". You can't double something which has no finite value just like you can't double nothing - which also has no finite value (except maybe 0, which is paradoxical number, but I'm not willing to enter the area of the hardcore mathematics which is totally dark for me). Otherwise you are presuming the existence of a border which contradicts the notion of infinity.
1.01 is a different value than 1.0000001 is it?
Because of that, there is infinite values between numbers.
Of course, there are not infinite "practical" values between numbers.
____________
|
|
mamgaeater
Legendary Hero
Shroud, Flying, Trample, Haste
|
|
posted March 13, 2011 03:11 AM |
|
|
Quote:
Quote:
A simple example. Between 0 and 1, there are infinite many real numbers. No doubt there are double as many real numbers between 0 and 2, also infinite.
I don't think the example is correct. The "infinite" you are talking about is actually quite finite. To have double the amount of "infinite" numbers between 0 and 2 in comparison with the amount of numbers between 0 and 1, you have to know what is the amount of numbers between 0 and 1, i.e. to have a finite quantity which is to be "doubled". You can't double something which has no finite value just like you can't double nothing - which also has no finite value (except maybe 0, which is paradoxical number, but I'm not willing to enter the area of the hardcore mathematics which is totally dark for me). Otherwise you are presuming the existence of a border which contradicts the notion of infinity.
It isn't defined but that doesn't necessarily mean that there isn't a way to know it is smaller or bigger.
if all infinities were equal that would mean that the number of numbers between 0 and 1 (I'll call this X) were equal to the sum of numbers between 0 and 2. (I'll call this Y)
But how can that be true? All of the numbers in X are also included in Y. Y will always be greater than X because Y itself includes all of X's values. No matter how large X is, Y will always be larger. (twice as large in this case)
____________
Protection From Everything.
dota
|
|
shares
Supreme Hero
I am. Thusly I am.
|
|
posted March 13, 2011 09:01 AM |
|
|
Mamgaeater and ohforf are quite right. The existance of varying infinities is also part of the evidence for multiple universes(though that hardly provides any evidence in the previous matter).
I can also tell you that time is about two infinities long.
____________
|
|
Zenofex
Responsible
Legendary Hero
Kreegan-atheist
|
|
posted March 13, 2011 10:11 AM |
|
|
Well, if this is all true, then the notion of infinite has to be re-defined or at least there should be some other terms to describe it.
Quote:
1.01 is a different value than 1.0000001 is it?
Because of that, there is infinite values between numbers.
Of course, there are not infinite "practical" values between numbers.
Yes, but 1.0000001 is not the end of the infinite as the latter has no end. 0 to 1 and 0 to 2 in this case are borders, so you have one infinity between 0 and 1 and another infinity between 0 and 2 (this way of expression is not very good but I don't know how else to put it, plus English is not my native language). If one of them is "bigger" than the other, then the "smaller" part has to be finite, otherwise there is no base for comparison. If there are two or more infinities on the other hand, they have to co-exist in some sort of reciprocity, otherwise they will be borders for each other.
Quote:
if all infinities were equal that would mean that the number of numbers between 0 and 1 (I'll call this X) were equal to the sum of numbers between 0 and 2. (I'll call this Y)
But how can that be true? All of the numbers in X are also included in Y. Y will always be greater than X because Y itself includes all of X's values. No matter how large X is, Y will always be larger. (twice as large in this case)
That could be so if there is a finite number of numbers between 0 and 1 and 0 and 2 respectively - that's what you supposition suggests. The infinite however is where the quantity has no exact numerical value, i.e. I don't think you could say that there is infinity X where X is some number. For the same reason it is not exactly properly to say that there is an infinity between 0 and 1 as 0 and 1 would be borders.
|
| |
|
|
