# Is there a middle to our Universe?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by machiaventa, Aug 5, 2009.

1. ### AlphaNumericFully ionizedModerator

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Everyone has a vague understanding of what 'space' is. You don't always need to give a formal definition for everything. I imagine few people can give a formal dictionary definition for the word 'the' but any native English speaker has a good grasp of how it is used. For instance, if you're a native English speaker you almost intrinsically know there's something wrong with the sentence 'Monday is first day of week'. In fact, I almost read it in a foreign accent since it's something you'd expect of a non-native English speaker.

It's quite hard to give a formal definition of such things as 'space' and 'time', yet everyone has a notion of them. You can give formal definitions involving mathematical terminology, in how space-time is viewed in general relativity, but I'd imagine you would not accept them.

In GR there is a very clear and distinct difference between an explosion of material in space and the explosion of space containing material. The form, assuming no back reaction, has a time independent metric. The latter does not. The former has time varying positions of the dtuff which makes up the matter, the former doesn't need to, they are stationary in a comoving frame. The FRW metric can model an 'exploding space-time' without needing to make reference to any actual matter.

So your claim James's statements are mute without a formal definition is mute itself.

3. ### Doc RichardRegistered Member

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Oh.
I see.
At least, I think I understand a bit.
I understand that I do not understand.
Which is a start, I suppose.

There are several questions flying around in my head at the moment, but the only one that I can put into words is this: "Why in heaven's name would space want to expand faster than the speed of light in the first place?"

But this is not a question that I expect anyone here to answer.

Anyway, thanks for the enlightenment guys.

R

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

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I'd ask you: why do you think space should want to expand slower than the speed of light?

7. ### StrangerInAStrangeLandSubQuantum MechanicValued Senior Member

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I made the claim after asking for a definition. The claim is valid.
You claim everyone knows yet you do not define it. Refusing to provide a requested definition inherently invalidates any statement containing the "word".

8. ### eburacum45Valued Senior Member

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Space is what stops everything happening in the same place. Time is what stops everything happening at once. Next question...

9. ### BelalanRegistered Senior Member

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Sigh, a number of things. Firstly string theory fails in the same manner as religion. It is impossible to prove and or disprove. In string theory when 26 dimensions fails they move onto 27 and keep on going when it doesn't work.

In terms of the 'middle of our universe' we first need to specify what exactly the universe is and by which theory you are going. Our universe has four spacial dimensions and one time dimension. The best analogy that I have found should be familiar to those who have read Flatland by A. Square.

Imagine you are an ant walking on an orange that is suspended in a quantum vacume. Your ant has various breathing devices that quantum tunnel a gaseous compound of 79% nitrogen and 21% oxygen in from an external source to prevent him/her from sufforcating. The ant and the orange are wrapped in unobervable, unreactive and perfect insulation to prevent heat loss. The orange supports a gravitational field which causes objects to fall towards its surface at pi squared meters per second per second. For the moment the ant and the orange will not rupture due to the pressure difference between them and the quantum vacume because I said so*.

Now back to the analogy, you are the ant. Your goal is to walk to the edge of the universe (the orange) and you will achieve this by walking in a straight line. As you can see, because the universe can operate in a dimension higher than the one which you operate in you cannot do much to get to the edge. Now you decide to try and find the center of the universe again, you will not be able to.

To the more educated of readers, yes I know that in a quantum vacume that particles such as the higgs boson and the graviton do not function, thus meaning that the orange and the ant would be thrown into movement faster than the speed of light due to the imbalance caused by the existance of either. This movement would be non terminating and would be paradoxical as the nitrogen oxygen compound would be quantum tunneled from the present to the ant which is now travelling in the past in a backwards (from our current perspective) direction to our concept of time. In other words this analogy is so badly broken that it makes a mockery of the bread rising in the oven analogies. Don't you just love how we try to appeal to the non-scientific and grimace in pain at all the inaccuracies?

10. ### gooseRegistered Senior Member

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Its just stuck going faster than the speed of light, and since something going faster than the speed of light cannot slow down to the speed of light, (or slower for that matter), it will remain there..... forever

11. ### AlphaNumericFully ionizedModerator

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Utterly wrong and shows you've got no understanding of string theory, only an axe to grind.

26 dimensional space-time arises in bosonic string theory via anomaly cancellation. Anomalies are found in all quantum field theories and are when a classical symmetry doesn't exist in the quantum theory. This is an inconsistency and so only when anomalies are set to zero do you get a consistent theory. It's this which is guiding a lot of GUT work into extensions of the MSSM. In bosonic string theory you only get a consistent behaviour if the strings move in 26 dimensions. If you add in fermions then they alter the behaviour to make it 10 dimensions. Yes, there are 'sub-critical' string theories in other numbers of dimensions but they are enormously restricted, in no way is it physicists saying "Try 26, if that's wrong try 27!".

12. ### Evolon73Registered Member

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I am by no means more than of average intelligence so bear with me.
I just watched an episode of Universe. And they said that according to
the doppler shift of distance galaxies the universe is expanding and doing
so more quickly.

If the doppler shift of far away galaxies shows that its expanding...

And the far away galaxies are the past.

Wouldn't that mean that it was expanding faster in the past than it is now.

And thus mean it is slowing?

13. ### John99BannedBanned

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i dont believe in the correlation between speed, time and distance. not that if you go faster you wont get there quicker but time itself.

i think time is based on the individual and that individuals age is the sole factor.

14. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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Unfortunately there IS a correlation.
Regardless of "belief".

In which case you think wrong.
A second is still a second, a year is still a year.
The perception may vary, the actual interval doesn't.

15. ### John99BannedBanned

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that is right, and the perception is directly related to time. tha fact is that time is longest at the first second of breath and gradually\steadily quickens.

16. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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No.
Perception is NOT time or the passage of time itself.

No.

17. ### BenTheManDr. of Physics, Prof. of LoveValued Senior Member

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This is a really good way to put it. The most helpful analogy to me is to imagine the surface of a balloon---as the balloon inflates, there is no center''. Another good analogy is a loaf of raisin bread---as the bread rises, all of the raisins move apart, and there is no real center.

18. ### John99BannedBanned

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well, it is a theory and it is my theory.

19. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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Except that it doesn't meet the definition of, or criteria to qualify as, a "theory".
And it's unsupported (indeed contradicted) by science (or even simple observation).
Way to go.

20. ### John99BannedBanned

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why is it contradicted? in that case we can base time off of anything we want to. the revolutions of the earth or any arbitrary function. i am basing it off of real life experiences.

21. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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For example if you take a bus trip: at the end everyone agrees on how long it took.
Boiling an egg happens whether it's a 12 year old or a 90 year doing the cooking.

No, you're basing it on real-life perceptions, not actualities.

22. ### John99BannedBanned

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Exactly. the younger the person the longer the egg takes to boil. this is a fact.

23. ### John99BannedBanned

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IF you throw away all the clocks. THAT is the essence of REAL time.