Young Universe gets busy

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Adam, Jan 14, 2003.

1. §lîñk€¥™Uneducated smart alecRegistered Senior Member

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No, you have misunderstood my question. The center of your circle is not a point on the rope. I want the center of the rope and that point must be on the rope. So where is it?

. Wow. Thanks for the demonstration on the level of your education (or rather the apparent lack of it).

A light year is the distance travelled by light in one year in vacuo. Light covers nearly 300,000km in one second. In one (approximate) year it would cover 300000x60x60x24x365 = 9,460,800,000,000km.

It has nothing to do with knowing where the center of the Universe is.

There are no objects "around space". Objects exist within space.

No, the Big Bang did not happen in space. The Big Bang was the beginning of space. If you want to think of it as an explosion you should see yourself as inside the explosion.

This isn't even consistent with your above quoted statement.

Alien Mastermind, please don't take this the wrong way, but you are either severely uneducated, and as such, many of your complaints stink of naïvité, and are framed from an uninformed and conceptually poor position. Or, you are simply acting the fool.

kind regards
Paul

3. §lîñk€¥™Uneducated smart alecRegistered Senior Member

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Every point in space is the center of expansion.

The Big Bang happened everywhere.

kind regards
Paul

5. James RJust this guy, you know?Staff Member

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Procop:

Think about the balloon again. As you blow it up, each dot moves further away from the other dots. No dot moves closer to any other dot.

7. ProCopValued Senior Member

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RE:James R

If two planes are flying from London, one west, the other east, they fly in one perspective away from one another in the other perspective they wil crash into one another in the other hemisphare. They fly away from one another only some way then they start to fly closer (The Earth is round). (Space is finite.)

8. §lîñk€¥™Uneducated smart alecRegistered Senior Member

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The earth's size does not change. However, space is expanding, which would equate to the earth getting bigger as the planes fly around it.

Let's say the planes fly away from London at 100mph each with respect to London. Also, let's say that the earth's circumference is increasing in size by 100mph/per 1000miles. ie. The circumference is 24000miles to start with. One hour later the circumference will be 24000 + (24000/1000*100) = 24000 + 2400 = 26400.

Will the planes ever crash into each other?

9. ProCopValued Senior Member

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RE: §lîñk€¥™

If the space is expanding qiucker than the planes fly not, but it was said that the space is finite...

10. Alien MastermindRegistered Senior Member

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Paul,

I would have to apologise. I have thought about some things I have said and understood them now. But

that I still do not understand. Wouldn't you need to have boundaries to measure the size of space? You would need to measure the size of space in order to to be able to say "cm/sec/light year".

Now doing that would be possible if the universe would be the surface of a sphere (that's the way I understand it from what you said). However, you also said that the universe is 3D space. That would mean that a surface of the sphere wouldn't apply, becasue it's 2D. Then all I could think of is the volume of the sphere. But THAT would have a center, as well as an edge.

Now please, I am not trying to change anyone's mind. I am merely trying to clarify things for myself.

11. §lîñk€¥™Uneducated smart alecRegistered Senior Member

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Agreed.

Indeed it is. At any moment you care to mention the Universe has a finite size. Same as the earth in the example above.

How big was the earth "to start with"? 24000mikes in circumference. How big was the earth 1 hour later? 26400miles in cicumference. These are all finite sizes.

You have mistaken the word finite for fixed, unchanging. It does not mean this.

kind regards

12. ProCopValued Senior Member

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RE: §lîñk€¥™

This changing, non fixed universe will be expanding infinitely but will always have a finite size (at a given moment - however big).

An infinitely small number will always be getting smaller but at any given moment it will have a finite number of digits.

Your concept seems not to be different from infinity.

13. §lîñk€¥™Uneducated smart alecRegistered Senior Member

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"A man who is able to admit his errors is a man able to learn". Good on you AM. This is evidence enough that you are seeking to understand.

No. The surface of a sphere is unbounded. It has no edge. Yet we can work out the circumference and the area of the surface. We don't even need to know the radius.

Don't worry too much. Making the leap from the 2-D surface of a sphere to a 3-D space is a hard thing to do. I, and I'm sure many others here, can appreciate the difficulty you are having.

You are sitting in your home (or at work) and everything around is flat. Flat in the sense that you are completely unable to detect that the surface of the earth is curved. You have no idea how big space is. Yet, you probably have a rule (straight edge) somewhere marked off in cm along one edge, and inches along the other edge (these are standard kit for most UK schoolkids doing anything that requires measurement).

A light year is no different. It is simply a long rule. We don't need to know how big the Universe is in order to define the length of this rule. All we need to know is the length (in time) of one earth year, and the speed of light (which is constant in vacuo).

As to the redshift being 1.9-2.1cm/sec/light year. The number is usually defined as 60-70km/sec/megaparsec (megaparsec = 3,260,000 light years approx.). I think it is defined this way in order to give an idea of the scales we are talking about when it comes to space.

Well, to be honest that wasn't at first apparent but as I say above, you have made it clear you want to learn.

kind regards

14. Alien MastermindRegistered Senior Member

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Err, are you saying that a 3D sphere wouldn't have a center?

15. §lîñk€¥™Uneducated smart alecRegistered Senior Member

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A sphere, a 3-D object, does indeed have a center. The Universe, however, is not a 3-D sphere. Space is like the 2-D curved surface of a sphere, but it is not on anything.

This is where the (difficult) conceptual leap comes in from the 2-D curved surface of a sphere to a 3-D space that is curved.

It's a loose analogy but not the whole picture.

kind regards

16. cephas1012Registered Senior Member

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General question:
James said:
So does this mean theoretically you could look one way and see a star that was actaully in the opposite direction you were looking in if you could see far enough?

Related to that, do they have an idea as of to how far across the universe is?

17. Alien MastermindRegistered Senior Member

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Paul,

...This just kind of doesn't make sense to me... Why isn't the universe a 3D sphere. It would make sense to me (pardon the lack of my knowledge in the subject). The Big Bang has occured, and since then everything was moving away from it. But it seems that you disagree on that, and I still didn't get what you think on that matter.

Thanks
Alien

18. §lîñk€¥™Uneducated smart alecRegistered Senior Member

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Well, I sat here for a moment and thought about this. At first I thought, yes, you would see it in two directions if the universe was small enough and expanding slow enough, but then I wondered if it wouldn't occupy the whole sky because the universe is curved back on itself.

Basically, I'm not sure. Sorry. Maybe someone a bit more in the know can answer that one.

I would imagine there have been some estimates. How they would go about it I'm not sure, but they would have to have a rough guess in order to calculate the matter density (Omega). My guess is that it is something like 3x10<sup>10</sup> (30,000 million) light years across.

kind regards

19. chrootCrackpot killerRegistered Senior Member

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2,350
Only if the entire universe is within causal contact. In other words, if enough time has elapsed since the big bang such that light from every part of the universe has had time to reach every other part of the universe. This is currently believed to be untrue -- we believe the universe is too young to be entirely in causal contact. Eventually, however, the concept will be correct -- you could look in some straight line and see the earth as it was billions of years ago.
The size of the observable universe is just the age of the universe times c, or about 15 to 20 billion light-years. No one can tell you for sure how big the entire universe is, however.

- Warren

20. §lîñk€¥™Uneducated smart alecRegistered Senior Member

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Well, let's think of it as a 3-D sphere for a moment. What is outside this sphere? There is nothing outside. No dimensions, no time. No-thing. How big is that? It has no no size. So the sphere's edge has no size.
Well, this is a problem of thinking it "exploded".

An explosion, like dynamite exploding, happens inside space and time. We can say where and when it exploded for eg. 30ft below sea level in a quarry in Wales at 3.30pm GMT.

The Big Bang was the beginning of space and time. It didn't happen in space and time. This is conceptually different. We can't point to a place or time for where and when it happened. All we can say is time and space started in the Big Bang.

kind regards

21. TristanLeave your World BehindValued Senior Member

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1,358
Two things:

Isn't it possible that the dimensions of space and so forth are incomprehensible to our feable minds? So this means its pointless trying to explain something that we can hardly comprehend. Like if we lived in a two dimensional world, meaning we are flat creatures like squares and rectangles drawn on a blackboard. It would be interesting for us to discuss how our universe works but do you really think it would be possible for us to comprehend "Height" or "upwards" or "downwards" for that matter, if we cant look up or down. I think we could only possible even begain to comprehend it if a 3rd dimensional being poped into existance, not being perfectly represented due to 2D space, and picked one of use squares up. Then he remarked "Look, This is 'up'". Then it would be clear. But for right now we are locked into a place were we can not see the big picture no matter what we try to imagine. Its like wondering what a tree is (never seen it), and trying to comprehend it only knowing that it has leaves (never seen them either) and bark (nor that) while be locked up in a dark room inside the orbital of an electron while spinning violently back and forth. (very wierd analogy but effective).

Soo......the only other thing I can say is this.....

"The cosmos is all that is, or ever was, or ever will be"
-Carl Sagan

No questions asked, although Ill be a hypocrit and say "its fun to think about"

Later
T

22. matnayRegistered Senior Member

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I think that I am begining to grasp this impossible concept of spatial expansion that's confused me so far. I came up with an analogy that really helped me conceptualize the big picture, without being confused by the surface-of-a-balloon analogy. So for anyone still having trouble, maybe this will help. Basically it's an expanded version of the Astroids(the video game) analogy:

First of all, you must understand how the game works. For example, when you exit off the right side of the screen, you then enter the left side of the screen. Note that there is no actual center of space, but that each point on the screen is equally arbitrary. Now, imagine that the size of the monitor represents all of 3-D space that matter and energy(the astroids, ship, etc...) are contained in. Now go back in time to the big bang. A moment after the big bang happened, the monitor would have been the size of a golf ball(and all the astroids/ships would have been condensed together). Note that the right-exit/left-enter property is already in effect. As the big bang keeps expanding, so does the monitor in our analogy. The condensed matter starts to spread out, but not from any arbitrary central point.

Note that there is no center point of expansion in regards to the video game word, but the monitor does have a center point of expansion.

23. blobranaRegistered Senior Member

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2,214
hehe,
like the anology...
(and to add to the confusion) perhaps the actual sprites were SHRINKING , and the monitor kept still,
And they were not just shrinking at a uniform rate but were accelerating...And funnily enough a by-product to this would be Gravity!...

Who needs zero-spin Higgs bosons!
(just joking)

Seriously, we need these extra dimensions to solve the horizon, inflation, magnetic monopoles and other problems...Heterotic string theories begin with 10 dimensions (up to 26!) and its the
properties of super-symmetry breaking that give rise to all the things in the universe...