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#16    MID

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Posted 15 April 2008 - 01:04 AM

Grey Area on Apr 14 2008, 07:16 PM, said:

As I understand it attaining the speed of light is theoretically impossible because:  When an object accelerates it gains mass, which requires more energy input,so theoretically to accelerate anything with mass to the speed of light would require an infinate amount of energy.  This is not a great explanation but it is described by Einsteins formula E=mc2, as well as calculating energy potential it can be applied to acceleration.

So to calculate the energy required to accelerate to a certain speed you take the mass (m) x velocity (c (usually sol)) squared.  Its a bit more complex than that and the actual calculation would be differential but for a simple explanation It'll do, until someone corrects me its been ages since I have dealt with that.


Actually, the mathematics involved with Special Relativity are elegantly simple.
Above, a little ways, I discussed the speed limit of "C":


Quote

Oddly enough, Special Relativity predicts that as an object nears the speed of light, it will shrink in respect to its length in the direction of motion, relative to the stationary observer, not get bigger. Clocks also slow down in the same fashion, and by the same relation...

(1 / square root of (1 - velocity squared / speed of light squared))


We cannot attain the speed of light because if velocity in the relation above is = the speed of light, the relation becomes the square root of zero...which of course is zero...meaning something would have no length and time would cease to exist, which of course isn't possible for an object in space. Thus, "c" is unattainable. And of course, making velocity > "c" would result in the square root of a negative number, which is not a real number...thus, you can't attain or exceed the speed of light, according to Special Relativity...

Of course, none of the changes would be perceptible to the person who was actually moving!
...wierd stuff, eh?

It's really that bottom-line simple....of course, understanding the derivation of that relation takes a little more than basic algebra. Einstein wrote a popular exposition on Relativity in 1916, in which he said that it assumed a level of education which corresponded to that of a college matriculation exam. I think today perhaps that might be a little shy of the real requirement.

If you're actually interested, the book is called, oddly enough , RELATIVITY, Albert Einstein (1916) (c. 1961, the estate of Albert Einstein). It's relatively short (no pun intended), at about 155 pages or so, but it will take some patience and effort, and a knowledge of algebra at least to get through it. It's elegantly simple, really!


If you actually take the time to study Einsten's own work, and you get down to the bottom line of this cosmic speed limit stuff...you just kind of sit there with your mouth agape and say, "Holy crap...of course!"

It's alot of fun!



#17    protostar

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Posted 16 April 2008 - 01:12 AM

The part of the "big bang" that gets me is......if nothing can exceed the speed of light, how come inflation occurred faster than the speed of light!?
Or have I got that completely wrong?  dontgetit.gif


#18    MID

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Posted 16 April 2008 - 10:35 PM

protostar on Apr 15 2008, 09:12 PM, said:

The part of the "big bang" that gets me is......if nothing can exceed the speed of light, how come inflation occurred faster than the speed of light!?
Or have I got that completely wrong?  dontgetit.gif



Inflation?




#19    capeo

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Posted 16 April 2008 - 11:38 PM

protostar on Apr 15 2008, 09:12 PM, said:

The part of the "big bang" that gets me is......if nothing can exceed the speed of light, how come inflation occurred faster than the speed of light!?
Or have I got that completely wrong?  dontgetit.gif


You haven't got it completely wrong.  This is part of the horizon problem in the standard model and was first brought up in the seventies.  It's not that anything was moving faster than the speed of light but that metrics (how space is described) underwent exponential growth at the speed of light.  You can't picture it as moving away from a central point but instead everything moving away from everything at the same moment.  This would invariably mean that some areas of the universe would have no causal effect on others because energy from one area would never reach another given constant inflation.  This is based on the fact that the speed of light is dependent on a single inertial frame.  Yet you arrive at any inertial frame moving away from another at the speed of light.  They could never meet.  That's kind of simplified but it suffices.  This would also imply that the universe should not be so homogenously close in temperature.  The problem is solved by inflation through quantum fluctuations.  Meaning, at that point in the universe, fields would adhere to quantum fluctuations not the general standard model.  The predictions of the inflation model solved a ton of problems and has since had a bunch of it's predictions confirmed, such as homogenous background radiation.  What it comes down to is in first instances of inflation the universe followed the laws of quantum physics and was already acting like, say, a volume of gas with differing areas of temperature.  It homogenized quickly and the slight areas that didn't were the areas that formed collections of matter that later became galaxies and such.  This early homogenization should have remanents near the hubble limit and this is what we see.

I know this all sounds pretty wacky.  Something that is not often brought up is that the inflation model also implies a universe much, much larger than the visible universe.  What we see of the universe is within the hubble limit.  Outside of that there still remain metrics that had no causal reference on us.  Meaning, due to exponential inflation the fields there can never propogate past the hubble limit.  No wave, field, or anything bound by C (which is everything as we understand it) can reach us due to exponential inflation at C during the inflation event.

Well, I don't know if I cleared anything up or made it worse.

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#20    protostar

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Posted 18 April 2008 - 12:58 PM

Thanks capeo, I've read and reread your post several times......but alas, I still don't really get it!
What do you mean by "exponential growth at the speed of light"? I understand what exponential growth means, but not the complete sentence!
What I mean is.....exponential means accelerating and not linear, whereas the speed of light is constant.

I decided to do a Google on the subject and found Inflation for beginners.
I had to chuckle to myself.....for beginners? yeah right! clear as mud! lol
There is a paragraph that suggests that the expansion does exceed the speed of light, but it's spacetime that does this not matter.

capeo or anyone, is there a way of describing this theory that is more understandable to the cosmologically challenged!?



#21    Lord Of The Dragons

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Posted 19 April 2008 - 11:47 PM

There is another way of looking at the Big Bang theory.
In String Theory, our universe exists in Calabi Yau space. Calabi Yau space is a multi-dimensional space that exists in anything from 7 to 11 and upto 26 dimensions. In Calabi Yau space there exists 'Throats'. These are regions of space that are wide at the top and get progressively smaller as you travel down (think of a funnel). It has been theorised that, at a distant time in the past, our universe fell down one of these Throats. As the universe travelled down the Throat, it would be compressed into an infinately small point (Big Crunch?). However, because the universe is spinning, its rate of spin as it travelled down would increase until, eventually, Centrifugal Force would force the universe back up the Throat where it would expand again once it had the room. This could be one explanation for the Big Bang event. This would also explain what was here before the universe as we know it. It was the universe.

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#22    Your Friend

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Posted 26 April 2008 - 02:53 AM

Correct answer to original thread question.

Yes there is a more fundamental theory behind the big bang. It is known as string theory. (see string theory), In this theory (branes) short for membranes collide and the point of their collisions are viewed as big bangs. In fact youtube has a very nice collection of short films on string theory. I recommend them.


#23    Waspie_Dwarf

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Posted 26 April 2008 - 10:43 AM

Your Friend on Apr 26 2008, 03:53 AM, said:

Yes there is a more fundamental theory behind the big bang. It is known as string theory. (see string theory), In this theory (branes) short for membranes collide and the point of their collisions are viewed as big bangs.

The problem here is that string theory is not accepted by all physicsts, in fact far from it. Actually it isn't even a theory, more of a hypothesis. String theory is a nice attempt to unify the forces of nature and subatomic particles into one theory. However there is currently very little evidence to show whether string theory is correct. Even more problematically there are multiple (and sometimes mutually exclusive) interpretations of string theory. String theory requires more than the three spatial dimensions we are used to. The string theorists argue about how many are required and how they exist.

Then we have brane theory. This is an off shot of string theory. It is fairly new and is not yet widely accepted even by string theorists. It really is just a hypothesis with no evidence to support it... yet.

This at one of the cutting edges of physics. Brane theory and even string theory itself may become accepted or discarded in the next few years. Either way mankind's knowledge will have increased as a result.

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#24    Your Friend

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Posted 26 April 2008 - 12:07 PM

No, string theory has been unified, I believe it is called M theory.

   All theories are just models which rely on their predictive capacity and or / consistency with known observations as validity.

Do we know if the electrons are really spinning in electron spin ?.
Do we know if there are really quarks inside subatomic particles ?.
Do we know if a one legged duck really swims in a circle?.

     Sometimes the model (theory) adds understanding to the underlying process. Sometimes the process gives rise to the theory. It is the old chicken and egg conundrum.
    Sometimes new theories or discoveries shed light on old theories, for example Newtons law of gravity explained how to predict the acceleration, velocity and displacement of moving objects. I did nothing for the understanding of action at a distance. Along comes relativity and gives insight into a finite closed and curved universe, now we can see gravity as a straight line following curved space. If a theory is accurate at fitting the data and makes useful prediction, let it stand.
  
   If later we find conceptual problems with it, we can abandon it at that time. There is no absolute truth only series of smaller and smaller useful lies. I advocate acceptance of M theory until it is either disproved by malprediction of violation of previously accepted facts.

   If science cannot be wrong, if we can't change our minds, if we just dogmatically accept something as forever and eternally true irregardless of new insight and evidence , If we malign and mistreat everyone that does not share our opinion, then we would have to change our name to Religion.  

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#25    Silmarillion

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Posted 26 April 2008 - 12:16 PM

You make some excellent points. Please elaborate, though. I had thought that "super" string theory and brane theory (M Theory) had concluded that there are 11 dimensions? Or 12? The additional ones (by the way, humans encounter four: length, width, depth, and time) are wrapped up, folded, and twisted on the scale of foamy space. You are absolutely correct that it's hypothesis. Basically, it works with the math, and the math works with the theory. But we'll never be able to "see" that level. It goes against Heisenberg... But elaborate. What are the superstring theorists saying today: Brian Greene and company?

Waspie_Dwarf on Apr 26 2008, 10:43 AM, said:

The problem here is that string theory is not accepted by all physicsts, in fact far from it. Actually it isn't even a theory, more of a hypothesis. String theory is a nice attempt to unify the forces of nature and subatomic particles into one theory. However there is currently very little evidence to show whether string theory is correct. Even more problematically there are multiple (and sometimes mutually exclusive) interpretations of string theory. String theory requires more than the three spatial dimensions we are used to. The string theorists argue about how many are required and how they exist.

Then we have brane theory. This is an off shot of string theory. It is fairly new and is not yet widely accepted even by string theorists. It really is just a hypothesis with no evidence to support it... yet.

This at one of the cutting edges of physics. Brane theory and even string theory itself may become accepted or discarded in the next few years. Either way mankind's knowledge will have increased as a result.


Edited by lmbeharry, 26 April 2008 - 12:17 PM.

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#26    Lord Of The Dragons

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Posted 26 April 2008 - 09:14 PM

Waspie_Dwarf on Apr 26 2008, 10:43 AM, said:

The problem here is that string theory is not accepted by all physicsts, in fact far from it. Actually it isn't even a theory, more of a hypothesis. String theory is a nice attempt to unify the forces of nature and subatomic particles into one theory. However there is currently very little evidence to show whether string theory is correct. Even more problematically there are multiple (and sometimes mutually exclusive) interpretations of string theory. String theory requires more than the three spatial dimensions we are used to. The string theorists argue about how many are required and how they exist.

Then we have brane theory. This is an off shot of string theory. It is fairly new and is not yet widely accepted even by string theorists. It really is just a hypothesis with no evidence to support it... yet.

This at one of the cutting edges of physics. Brane theory and even string theory itself may become accepted or discarded in the next few years. Either way mankind's knowledge will have increased as a result.


I would disagree with what you said about String Theory being just a hypothesis. I think String Theory is as relevant a theory as Relativity was when it was in its infancy. And yes, String Theory is, basically, still in its infancy, especially compared to Relativity and Quantum mechanics. You also have to remember that String Theory was considered dead at one point and was hardly even thought of during the 70s, it wasn't until mid-way through the 80s that it was taken up again as a viable theory and there has been many significant advancements made in it in the years since then.
True, for String Theory to work properly, it has to exist in many dimensions and most of these dimensions are much smaller than the Planck length and, therefore, almost impossible to prove. However, taking these dimensions as a given, String Theory works remarkably well when applied to models of the universe. That's why it is still the best option as a grand unification theory to date imo.

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#27    Waspie_Dwarf

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Posted 26 April 2008 - 09:39 PM

Your Friend on Apr 26 2008, 01:07 PM, said:

No, string theory has been unified, I believe it is called M theory.

I do not claim to be any kind of expert on the subject, but it is my understanding is that M theory is a branch of string theory which would unify them if correct. However, yet again, it is highly hypothetical. As there is no empirical evidence to support string theory there can, logically, be no empirical evidence to support M theory.

Your Friend on Apr 26 2008, 01:07 PM, said:

All theories are just models which rely on their predictive capacity and or / consistency with known observations as validity.

This is true but string theory has not yet reached that level, it remains purely hypothetical, a mathematical possibility but not yet backed up by observations in the same way that Relativity or Quantum Mechanics are. These have both been tested experimentally. The theories make specific predictions when where then tested and the results found to be excellent fits, Sting Theory has not been tested in the same way, that is why I believe it is only a working hypothesis and not yet theory. One day string theory may be experimentally verified, but not yet.


Your Friend on Apr 26 2008, 01:07 PM, said:

Do we know if the electrons are really spinning in electron spin ?.
Do we know if there are really quarks inside subatomic particles ?.
Do we know if a one legged duck really swims in a circle?.

I'm not sure about the duck, but the other two were predicted and then experimentally verified. We can take this discussion down to the philosophical level, do we really know that anything exists, but then it would no longer suitable for the science board. From a scientific point of view though the Standard Model has been tested time and time again and the experiments appear to confirm it. This is not true of string theory.

Your Friend on Apr 26 2008, 01:07 PM, said:

I advocate acceptance of M theory until it is either disproved by malprediction of violation of previously accepted facts.

Up until here you were making good scientific sense, sadly you ruined it with this one sentence. Science should never EVER be in the business of accepting as fact something for which there is little or no supporting evidence, that is the realm of superstition and religion. IM theory should neither be accepted nor rejected until such time as there is good evidence to make such a decision. It should be treated as what it is a hypothesis... a good but unproven working model.

Your Friend on Apr 26 2008, 01:07 PM, said:

If science cannot be wrong, if we can't change our minds, if we just dogmatically accept something as forever and eternally true irregardless of new insight and evidence , If we malign and mistreat everyone that does not share our opinion, then we would have to change our name to Religion.

I agree with you on this point (and have made this very same point many times on this science forum), but it also holds true that if we dogmatically accept a hypothesis arbitrarily, as you seem to have done above, we risk going down the same route. Acceptance of a hypothesis must be on the weight of evidence. If there is no evidence there can be no acceptance however good the hypothesis looks on paper.

I have no problem with string theory, my posts should in no way be considered an attack on it. My point is simply that it remains purely hypothetical and should not be considered fact... yet.

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#28    --Mandalore--

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Posted 29 April 2008 - 12:10 AM

I have a question and maybe somebody can help me with it. I read in a high school textbook today(I collect them btw) and it said that when all the matter came together that it started spinning and exploded thus the Big Bang, the question I have is if this "infintesimile region" was spinning in one direction wouldn't all the galaxies, planets, etc. be spinning in the same direction? Thanks. grin2.gif

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#29    Torgo

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Posted 29 April 2008 - 05:54 PM

tarheelsfan23 on Apr 28 2008, 08:10 PM, said:

I have a question and maybe somebody can help me with it. I read in a high school textbook today(I collect them btw) and it said that when all the matter came together that it started spinning and exploded thus the Big Bang, the question I have is if this "infintesimile region" was spinning in one direction wouldn't all the galaxies, planets, etc. be spinning in the same direction? Thanks. grin2.gif


Your textbook is wrong.

People (including the people who write the often oversimplified textbooks) have an odd conception that the big bang was directly responsible for every detail in the uinverse.  As near as we can tell, what ACTUALLY happened is that the furthest back we can see (the microwave background radiation) the primordial gas was very nearly uniform with only small density differences.  These lead large clouds to collapse into the filament-of-galaxies and void structure we see in the universe as a whole.  As clouds collapsed further, you got places becoming dense enough for star formation.  Depending on the details of that collapse you got galaxies with a lot of spin (spirals) or not much spin (ellipticals) and spin in all different directions.  Within all these galaxies, the forces causing smaller clouds to collapse into stars and stellar systems are FAR stronger influences on the eventual orientation of the stars and planets than the galactic spin.  Its basically chaotic stochastic steps all along the way causing all these things, not some kind of overall angular momentum of the universe.

Edited by Torgo, 29 April 2008 - 05:55 PM.


#30    --Mandalore--

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Posted 29 April 2008 - 06:11 PM

Torgo on Apr 29 2008, 01:54 PM, said:

Your textbook is wrong.

People (including the people who write the often oversimplified textbooks) have an odd conception that the big bang was directly responsible for every detail in the uinverse. As near as we can tell, what ACTUALLY happened is that the furthest back we can see (the microwave background radiation) the primordial gas was very nearly uniform with only small density differences. These lead large clouds to collapse into the filament-of-galaxies and void structure we see in the universe as a whole. As clouds collapsed further, you got places becoming dense enough for star formation. Depending on the details of that collapse you got galaxies with a lot of spin (spirals) or not much spin (ellipticals) and spin in all different directions. Within all these galaxies, the forces causing smaller clouds to collapse into stars and stellar systems are FAR stronger influences on the eventual orientation of the stars and planets than the galactic spin. Its basically chaotic stochastic steps all along the way causing all these things, not some kind of overall angular momentum of the universe.



Thanks, I don't believe in the Big Bang, but I do like to study up on the subject of evolution and the Big Bang. original.gif

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