Is it correct for me to interpret the big bang as something like an infinitely small spinning point, that suddenly explodes in mass, spinning out matter/energy in all directions outward from it's center point?
No. The universe is expanding and if you calculate back everything it came from one single point. It's not a singularity that exploded or spewed out matter. The universe isn't expanding right now because the outer shell of stars is being thrown away from the center. No, the space between the stars is increasing. Ignore the matter in the universe itself. The universe itself inflated from a single point into what it is now. During all that time a lot happened to the matter inside the universe. But that's a different issue.
I thought that scientists were unable to find like 98% of the matter than the universe ought to have and just theorized something they decided to call dark matter as a temporary explanation.
My question is: Why do physicists or whoever think that the universe won't slow down again?
If there is enough matter in the universe then all that matter has enough mass, causing enough gravity, to make it contract again.
Currently the universe is expanding at increasing velocity and it doesn't look like it has anywhere close to enough to start to contract.
Is it correct for me to interpret the big bang as something like an infinitely small spinning point, that suddenly explodes in mass, spinning out matter/energy in all directions outward from it's center point?
No. The universe is expanding and if you calculate back everything it came from one single point. It's not a singularity that exploded or spewed out matter. The universe isn't expanding right now because the outer shell of stars is being thrown away from the center. No, the space between the stars is increasing. Ignore the matter in the universe itself. The universe itself inflated from a single point into what it is now. During all that time a lot happened to the matter inside the universe. But that's a different issue.
I thought that scientists were unable to find like 98% of the matter than the universe ought to have and just theorized something they decided to call dark matter as a temporary explanation.
I don't think scientists are able to observe more than 1% of the universe, much less be able to account concretely for 2% of it even.
acceleration: the rate of change of velocity with respect to time speed: how fast an object is moving (the time rate of change of position)
Many people are using versions of the word accelerate incorrectly. Accelerating outwards specifically means to either speed up in the outward direction, or possibly slow down (deceleration aka negative acceleration). Velocity and acceleration are not the same thing -_-
On April 07 2009 05:29 Diomedes wrote: The universe is expanding and if you calculate back everything it came from one single point. It's not a singularity that exploded or spewed out matter.
Then what happened?
The universe isn't expanding right now because the outer shell of stars is being thrown away from the center. No, the space between the stars is increasing.
On April 07 2009 05:30 vAltyR wrote: You know what escape velocity is, right? It's the velocity an object must be travelling in order to ecape the pull of the gravity of any given mass.
We can measure the rate of expansion of the universe (if you want more details, ask), so the theory is, if the universe is expanding faster than its own escape velocity, then it will never compress back down to the original size from just before the big bang. Seems like a straightforward problem, right?
quick interruption here, you may or may not know the answer to this question. the general movement of the galaxies - is it a linear path, or is it curving? it would have to be curving, wouldn't it?
On April 07 2009 06:04 micronesia wrote: acceleration: the rate of change of velocity with respect to time speed: how fast an object is moving (the time rate of change of position)
Many people are using versions of the word accelerate incorrectly. Accelerating outwards specifically means to either speed up in the outward direction, or possibly slow down (deceleration aka negative acceleration). Velocity and acceleration are not the same thing -_-
i learned all about this the last time i had a physics discussion in a blog!
It will either expand "forever" or go back to big bang state~~ It depends on the actual mass of the universe, I remember reading book about this particular subject but my english's too weak to actually talk about this stuff lol
hmm... hehe... this is a very large topic, and depending on who you ask... you could receive different answers.
One of the well thought of theories is inflationary cosmology...
pretty much, an extremely small chunk of stuff is made up of dark matter... dark matter, reaching a certain state dark matters has a negative pressure. According to to Einstein's theory of relativity, gravity is not only changed due to displacement and mass, but also pressure and i think temperature. Since this mass has a greater amount of dark matter, this negative pressure creates an expanding gravitational force, causing a rapid expansion...
however, there is the idea that a set of matter only has to meet a certain set of defined characteristics to follow this expansion, like temp and different fields, and could in fact appear practically anywhere. Entire universes expanding out of universes... its a rather neat concept to visualize.. cant seem to find a pic...
Now, the idea of expansion is also a rather tricky one. planets and matter arnt just floating away, but in fact the space is expanding... let me rephrase that... a rather simple example is say you have a balloon with a grid on it... at each point place a penny, then blow up the balloon. The pennys themselves didnt get larger, but the space it is on did...
Now, the entire "bang" that happened just spread out a common matter. This has been attested to by the fact that there is a uniform electromagnetic wave throughout the universe. The entire universe was uniform. Looking now at the quantum mechanics side of things, the tiny jitters that is seen at the very small is spread out to practically uniform space. Whoever, with the jitters, as the universe cooled, tiny bits of matter began to pull on each and after a crapload of time... we got galaxies and junk ...
now, as the universe gets farther and farther away... some have theorized that the force created by the expanding gravity will slowly fall smaller than the contracting force... which will then pull all of the matter back in and once again start the cycle... and expand, contract, expand, contract... etc...
But, as always, there are more theories... Looking at it from a string theory perspective... the universe we know of is composed on one 3-brane and what caused the the expansion was a collision of our 3-brane with another. However, this has yet to be tested for our way of testing, using electromagnetic radiation, is trapped inside of the 3-brane... there is hope that gravity, being so weak, may actually be able in fact be leaking out of our 3-brane and can be used to test such theories... but... i don have my books atm and cant really explain much farther...
Researchers are hoping that the new Hadron collider will be able to, in fact, validate certain theories... being able to crash large ammounts of mater to tiny speeds may create conditions like the begining of our known universe or can hopefully validate some ideas brought up by string theory...
ack... /ramble i wasnt really planning on writing so much... but if you really want an experts opinion on this subject, and some like it, i would advise you get Brian Greene's book Fabric of the Cosmost. It goes for a great light read before bed
edit: i hope i didnt have to many errors like i said... im away from my books
The problem with the way you describe the phenomenon is the fact that you appear to consider matter to be flying outwards from a central point. According to inflationary cosmology, space itself is expanding like a loaf of raisin bread (the raisins representing galaxies, the bread space-time etc.). This means that all galaxies are moving away from every other galaxy. Space is expanding in every direction. There is no central point away from which matter is moving.
I have to read up a lot on space and time. So I don't have anything to add to that part of the discussion right now. The idea of dark energy is a concept thought up after observing acceleration.
As far as matter is concerned. All mater is unstable. Even black holes evaporate over time according to Hawkins. This is not in the order of billions of years. Add a lot more zeros. So in some models the universe will become empty space with only EM radiation.
Edit: The name Big bang suggests an explosion. But there is nothing kinetic about it. A kinetic explosion could never create space. If an pointlike object would explode it would immediately start caving in again due to gravitation. I feel like the subject is way out of my legaue
On April 07 2009 07:47 Swarmy wrote: The problem with the way you describe the phenomenon is the fact that you appear to consider matter to be flying outwards from a central point. According to inflationary cosmology, space itself is expanding like a loaf of raisin bread (the raisins representing galaxies, the bread space-time etc.). This means that all galaxies are moving away from every other galaxy. Space is expanding in every direction. There is no central point away from which matter is moving.
ok, I have heard this and I do understand it. But the actual matter must be moving away from a central point - or else it should be coming together. Right?
On April 07 2009 07:47 Swarmy wrote: The problem with the way you describe the phenomenon is the fact that you appear to consider matter to be flying outwards from a central point. According to inflationary cosmology, space itself is expanding like a loaf of raisin bread (the raisins representing galaxies, the bread space-time etc.). This means that all galaxies are moving away from every other galaxy. Space is expanding in every direction. There is no central point away from which matter is moving.
ok, I have heard this and I do understand it. But the actual matter must be moving away from a central point - or else it should be coming together. Right?
most common example for this in books is pumping spotted baloon with air, where spots represent galaxys~~you should also check hubble,doppler effect
The answer to your question is very simple: an explosion propelles matter away with a certain acceleration a, if there is no resistance force (like in the vacuum of space), the acceleration a will remain constant and the speed of the expanding matter will increase.
Offcourse this is only 1 view of the universe, its origin and its end, hence the awesome fuel for discussions since noone can know what has happened and what will happen.
I suggest reading a book or some other serious references about it (choices are enourmous, many topics), it may seem boring at first, but it is very compelling once you get into it. And with serious i mean NOT wikipedia, never ever cite it or trust it or use it as a reference.
According to some scientists there exists something called 'Dark Matter' and 'Dark Energy'. Dark Matter, they theorize, accounts for about 20-22% of all the mass in the universe, and Dark Energy accounts for about 70-75% of all the mass in the universe.
We cannot detect either of those, and according to all the tests run (don't ask me how they do it -- this is beyond my scope of knowledge), the visible matter in the universe accounts for about 4-6% of all the mass in the universe.
The reason why they believe that the universe is expanding at a faster rate than it was previously (which goes against the logic that gravity from mass will cause expansion to slow and eventually contract) is that Dark energy, being greater in mass than Dark Matter and visible matter combined, is causing the expansion of the universe at a greater rate than it can be contracted.
Of course, this is all highly theoretical. Dark Matter is the only thing we can indirectly prove, but there's significantly less indirect proof of Dark Energy.
This is sorta off topic but some people talked about Einstein, can someone explain how he figured out the equation? Actually, how do people figure out equations in general? I think it's pretty neat to figure out something that will work for specific things
from what i understand, the universe expanding forever is just 1 theory. i've also heard the theory that it will eventually hit some point and turn around and compact into a point again (pulsating hypersphere), and also that eventually it will just stop and remain at one size.
On April 07 2009 09:27 il0seonpurpose wrote: This is sorta off topic but some people talked about Einstein, can someone explain how he figured out the equation? Actually, how do people figure out equations in general? I think it's pretty neat to figure out something that will work for specific things
EPT
...
