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# Mind-blown.

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Rajat_Pawar
See guys..I was doing this presentation for my project..on the "BIG BANG THEORY" which almost everyone of you knows. If you don't, click on it. See this picture I used to represent the theory which I DO support.
This happened around 15 billion years ago.
Now the question comes.
You see the black background in which the explosion is occurring?
Now an example of what I am saying.
Consider a ball kept in a box. The ball exploded and we captured the moment on camera. Now the background would be the box right? That means, the ball was kept or was present in SOME surrounding. Now see the pic above.
If universe began after the BIG BANG theory, what was the SURROUNDING in which it took place? It must have needed some place to start exploding..What was it? IF it was there, it means, there's a universe WITHIN a universe, just like inception.
This content was mine, the questions too! Give your opinions.
Bikerman
This is one reason I dislike the 'bang' analogy that the name suggests.
Let's get some groundrules established:
1) It wasn't an explosion, or a 'bang' of any sort
2) Whenever we use a model to stand-in for something, we need to be REALLY careful that we don't mistake the limits of the model for the limits of the system being modelled.

Yes, a 3-D explosion MUST take place in 4-D spacetime (or 3D space and 1D TIme if you prefer). This is a limit of the model, NOT a genuine limit of the BB.
The BB was not an explosion into existing spacetime. It was the stretching of an infinitely small 'bit' of spacetime to the size of the universe we observe today (actually much bigger, but let's keep it simple to start).
Instead of the explosion model, think of a currant bun, before baking. The dough contains currants scattered throughout. We put it in the oven and the dough expands. The currants don't actually 'move', but they DO get further away as the dough between them stretches. This is a fairly good model for the big bang and subsequent inflation/expansion. The dough in the oven, of course, expands into empty space, BUT remember that this is a limit of the model, not the BB itself. The spacetime that 'stretched' during the BB (and which continues to stretch, faster and faster) obviously didn't have any space to expand into - otherwise it would already have BEEN spacetime and the BB would not have done anything.

If you get trapped into thinking of the BB as an explosion, it leads to many errors. The first one is this one here - the assumption that the BB must have 'exploded' into existing spacetime. The second error normally following is the assumption that, like an explosion, the galaxies should all be hurtling apart from a fixed point where the explosion occurred. This is WRONG. The BB didn't happen at a specific point in spacetime. A tiny bit of spacetime stretched very rapidly (inflation) - so really we are all inside the Big Bang and always have been, and the direction in which spacetime is expanding is 'EVERY' direction - just like the currant bun expanding in the oven.
Ankhanu
loremar

This video's right on with the OP's question especially
 Quote: It must have needed some place to start exploding..What was it?

It didn't had an origin. Or like it didn't have a fixed radial vector field or something that describes how everything moved. Or you can also imagine that the center of expansion can be anywhere or any point in the universe you want(Or I could be wrong, I just figured that out since it says that everything is moving away from each other which means I can imagine that I can choose any arbitrary point and imagine that the rest is moving away from that point).
Bikerman
Way too annoying for me ......

Easy and Mellow

Standard college intro level

A little bit more gnarly and interesting

More Gnarly still - for those with a good grasp of basic physics
http://www.newton.ac.uk/webseminars/pg+ws/2005/gmr/gmrw04/1107/penrose/
Bikerman
Way too annoying for me ......

Easy and Mellow

Standard college intro level

A little bit more gnarly and interesting

More Gnarly still - for those with a good grasp of basic physics
http://www.newton.ac.uk/webseminars/pg+ws/2005/gmr/gmrw04/1107/penrose/
loremar
I'm not sure if I imagined it right but if we assume that the universe has an edge, it would look like a ball. And the surface of the ball would be the edge of the universe. But in the real universe, even if you point at the surface of the ball, you'd still be in the center of the ball. Wait, but that wouldn't look like a ball anymore, would it? LOL.
Bikerman
Weerrrllll.....
Imagine the 3-D of space as a 2-D 'sheet' and that gets about as close as possible for such a model.
Now, the sheet (of paper if you like) can be scrunched into a sphere, or it can be perfectly flat, or it can be any one of an infinite number of other shapes/topologies. If the universe is closed in on itself then it would resemble a ball, with the skin of the ball representing 3-D space and the radius of the ball representing time.
Clearly to anyone on the ball there is no edge or other boundary - just infinite extent within a (possibly) bounded volume.
loremar
 Bikerman wrote: Weerrrllll..... Imagine the 3-D of space as a 2-D 'sheet' and that gets about as close as possible for such a model. Now, the sheet (of paper if you like) can be scrunched into a sphere, or it can be perfectly flat, or it can be any one of an infinite number of other shapes/topologies. If the universe is closed in on itself then it would resemble a ball, with the skin of the ball representing 3-D space and the radius of the ball representing time. Clearly to anyone on the ball there is no edge or other boundary - just infinite extent within a (possibly) bounded volume.

Oohhh. I get it now. You could imagine the skin of the ball(doesn't necessarily have to be a ball, could be any shape), as representing the space in the universe where everything's are and if you increase the radius of the ball or move forward in time, then you'd be stretching the universe. But from anywhere in space you can't see the edge, right? because there's no edge?

But I'm wondering. If I travel forward across the universe, then is it possible to circumnavigate the universe? or ,is it possible that I can draw a straight line from the start and end up back in the starting point?

But of course, the universe doesn't really look like a ball or anything. I guess, it's wrong to ask what the universe looks like since it doesn't really look like anything but space. That makes sense since if you have to assume that it has shape then that's the same as saying that the universe has an edge because there would be something else other than the universe that would define its shape and the edge/boundary that sits between them.
Bikerman
 loremar wrote: But I'm wondering. If I travel forward across the universe, then is it possible to circumnavigate the universe? or ,is it possible that I can draw a straight line from the start and end up back in the starting point?
Yes. If the universe is curved back on itself then you would end up back where you started. In fact you wouldn't - because the universe is expanding whilst you move....but the idea is correct, yes.

As for looks....what does a proton look like? The answer is 'other protons'. What does curved spacetime look like? Curved Spacetime. Tp say it looks LIKE (X) is nearly always going to cause problems because x will be different enough so that the model quickly breaks-down and one is left applying inappropriate parts of a broken model.
Rajat_Pawar
Yeah bikerman, I agree. But the main point is what was the dimension in which this expansion of the 'ball' occured? That's the thing that's driving me nuts. I wish I could get in a spaceship with infinite life and go round, checkout what the strange, dark, infinitely huge universe holds in store for me. One of spaceships went outta the solar system and is almost out of the 'magnetic or asteriod' field or something like that which surrounds our system. If it does get out of that, we could possibly explore 0.1 percent of this mind blowing question's solution. That the universe is expanding is not likely, cause I saw this program on discovery which said, that a galaxy about a lot bigger than ours is going to 'crash' into ours. Now if this happnened, expansion of the universe isn't taking place, right? Some also believe that there would be a 'close' to the universe, as in, the universe would get 'renewed' or it would be 'destroyed' and 'recreated.' (credits - stephen hawkings.)
Bikerman
Why do you think it has to be another dimension?

Is there a rule that everything is straight, and if we change that we need another dimension to make it 'crooked'? No, of course not. I understand your thinking but it is erroneous.
A dimension is a 'direction of freedom' - allowing movement along the axis conventionally used to represent that dimension.
4-D spacetime may not be free at all to 'move' in a higher dimension. It might just be that common-or-garden spacetime, when we get it from the shop, is naturally non-flat. Do we need a 5th dimension for this? No. The 4-D of spacetime describes every possible point within, so we don't need a fifth coordinate to describe the bendiness of spacetime, because it just IS bendy, it isn't actually free to move in that direction of 'twist' or 'bend'.

Do you see what I'm saying - this is not an easy concept, I understand, but it is important.
kelseymh
 Rajat_Pawar wrote: Yeah bikerman, I agree. But the main point is what was the dimension in which this expansion of the 'ball' occured?

There isn't one. The only time you "need" another dimension classically is in order to draw a picture that human beings can interpret. Those are called embedding diagrams (look it up), and they are merely a visual aid, not reality.

 Quote: That the universe is expanding is not likely, cause I saw this program on discovery which said, that a galaxy about a lot bigger than ours is going to 'crash' into ours. Now if this happnened, expansion of the universe isn't taking place, right?

Wrong. You need to have more knowledge in order to draw competent conclusions.

On local scales, gravity can hold objects, or collections of objects, together while the Universe expands around them. The solar system is not getting bigger because of cosmological expansion. The Milky Way and Andromeda galaxies are gravitationally bound to one another (they are both part of the Local Group), and therefore do not independently participate in the cosmological expansion.
ocalhoun
 Bikerman wrote: The BB didn't happen at a specific point in spacetime.

Now... isn't that an interesting thought...

I have always thought of it as being in a particular point in time, after all...

*goes off to think of what it would be like if time was expanding*
Bikerman
The idea of time 'expanding' doesn't really make sense, since it is, in any case, relative.

The way I sometimes explain it is - you are ALWAYS moving at the speed of light (c). Sometimes you are relatively still and therefore moving at c through time, most of the time you move around and the sum of velocity through space and time is c, and if you DID move at the speed of light then you would not move in time, only space. Whatever the combination, it always sums to c.
ocalhoun
So, you'd say the big bang did occur at a specific point in time?

That would open up some speculation as to what that difference between time dimension(s) and space dimensions could tell us about the nature of both...

*edit*

Oh yeah, but isn't space also relative? But it expands...
Bikerman
Not sure about a specific time - there are a couple of hypotheses that basically say no (ie that as t approaches zero, it never arrives. There are at least a couple of ways this might be so. One intruiging little thought is that strings bring some odd symmetries with them, if strong theory is correct. One result is that scale of things is not as it appears. T-Duality in s-string theory tells us that large and small distances can actually be the same to strings, depending on what 'mode' they are in.
Sounds weird but it means that the whole idea of large distances being multiples of smaller distances is, on some deep level, just wrong.
mazito
Thnks to Bikerman to enligths us i am enjoying the videos i have some problems to undertanding but i think i am in the good way

firt i try the Translate Subtitles but no good, the just de CC and then turn off my english is better than CC
Bikerman
Glad to try to help but I think that what I've probably done more than anything is point-up the problems when dealing with this stuff on an 'everyday' basis.
Many of the concepts are what people would probably call 'not common sense'. Some of them defy any real description except the most important one - the mathematical description.
Many people have a deep suspicion and even a mistrust of anything which they regard as counter-intuitive (which is just another way of saying 'anything that goes against the way they think the universe operates) and they don't understand the maths and are therefore doubly distrustful of that.
The simple truth that needs to be grasped is that the way that the universe operates, according to our best theories and observations, is possible to describe mathematically but is so far beyond anything that we could consider 'common sense' that not only is our intuition not particularly useful, it is very often an actual hindrance.
Mosr of us think we have a handle on reality - we think we know how the 'world works' - at least to some extent. This confidence is massively misplaced, as we have progressively disovered over the last century or so. Our understanding of what actually goes on, even in our own tiny piece of reality, is riddled with error, full of simplifications and short-cuts, and very often biased and self-contradictory. This is true of us all and to therefore use 'common sense' as a metric when examining theory is actually quite bizarre, not to mention massively and ignorantly egotistical. It is like the fool who watches a chess match for a few moves, during which only pawns are played, and thereafter insists that chess is a game in which the pieces can move forward 1, or sometimes 2 squares, that the notion of a bishop going diagonally is clearly madness, and the notion of a knight 'jumping' pieces is clearly indicitive of some deep psychosis requiring urgent treatment. The fact that their understanding leads, inevitably, to a chess game which lasts for 1 minute and always ends in a stalemated draw is disregarded, and the fact that people are actually observed playing a richer version is taken as evidence that they don't userstand the 'true' game.

It is, in short, no different to the religious apologist denying evolution because it goes against a world-view which they subscribe to - rather pathetic and parochial, at best.
mazito
i have the same opinion, but for me es a little hard to participate here, because my english is not good enough to discuss science, i am a mid school teacher i tehachs Math and phyisics is a small privete school, i have not the background in science i am an accountant and a public servant taht loves science and math and reads and study hard i think we dont did so bad because my students are capable to get spot in severals universitys.

just last week i recibe 17 books about scince abouth Math, Chaos Theory, Relativity and Quantum physcis.

i tell to my students that the open mind is the best we can do to get an education of quality, get apart from taboos, and ask them to not religious discusses, because i live in a small chatolic town, where religion is part of the formation of the people, i was in the primary school at religious one, then at 12 i went to the seminary and quit after a week.

i like to have a better english to participate, but reading is enough

thanks for give us your time