Structure of Universe: Is It Correct?

The structure of the Universe

What is spacetime geometry?

    Think of a very large ball. Even though you look at the ball in three space dimensions, the outer surface of the ball has thegeometry of a sphere in two dimensions, because there are only two independent directions of motion along the surface. If you were very small and lived on the surface of the ball you might think you weren’t on a ball at all, but on a big flat two-dimensional plane. But if you were to carefully measure distances on the sphere, you would discover that you were not living on a flat surface but on the curved surface of a large sphere.
    The idea of the curvature of the surface of the ball can apply to the whole Universe at once. That was the great breakthrough in Einstein’s theory of general relativity. Space and time are unified into a single geometric entity called spacetime, and the spacetime has a geometry, spacetime can be curved just like the surface of a large ball is curved.
    When you look at or feel the surface of a large ball as a whole thing, you are experiencing the whole space of a sphere at once. The way mathematicians prefer to define the surface of that sphere is to describe the entire sphere, not just a part of it. One of the tricky aspects of describing a spacetime geometry is that we need to describe the whole of space and the whole of time. That means everywhere and forever at once. Spacetime geometry is the geometry of all space and all time together as one mathematical entity.

What determines spacetime geometry?

    Physicists generally work by looking for the equations of motion whose solutions best describe the system they want to describe. The Einstein equation is the classical equation of motion for spacetime. It’s a classical equation of motion because quantum behavior is never considered. The geometry of spacetime is treated as being classically certain, without any fuzzy quantum probabilities. For this reason, it is at best an approximation to the exact theory.
    The Einstein equation says that the curvature in spacetime in a given direction is directly related to the energy and momentum of everything in the spacetime that isn’t spacetime itself. In other words, the Einstein equation is what ties gravity to non-gravity, geometry to non-geometry. The curvature is the gravity, and all of the “other stuff” — the electrons and quarks that make up the atoms that make up matter, the electromagnetic radiation, every particle that mediates every force that isn’t gravity — lives in the curved spacetime and at the same time determines its curvature through the Einstein equation.

What is the geometry of our spacetime?

geometry of space time

    As mentioned previously, the full description of a given spacetime includes not only all of space but also all of time. In other words, everything that ever happened and ever will happen in that spacetime.
    Now, of course, if we took that too literally, we would be in trouble, because we can’t keep track of every little thing that ever happened and ever will happen to change the distribution of energy and momentum in the Universe. Luckily, humans are gifted with the powers of abstraction and approximation, so we can make abstract models that approximate the real Universe fairly well at large distances, say at the scale of galactic clusters.
    To solve the equations, simplifying assumptions also have to be made about the spacetime curvature. The first assumption we’ll make is that spacetime can be neatly separated into space and time. This isn’t always true in curved spacetime, in some cases such as around a spinning black hole, space and time get twisted together and can no longer be neatly separated. But there is no evidence that the Universe is spinning around in a way that would cause that to happen. So the assumption that all of spacetime can be described as space changing with time is well-justified.
    The next important assumption, the one behind the Big Bang theory, is that at every time in the Universe, space looks the same in every direction at every point. Looking the same in every direction is called isotropic, and looking the same at every point is called homogeneous. So we’re assuming that space is homogenous and isotropic. Cosmologists call this the assumption of maximal symmetry. At the large distance scales relevant to cosmology, it turns out that it’s a reasonable approximation to make.
    When cosmologists solve the Einstein equation for the spacetime geometry of our Universe, they consider three basic types of energy that could curve spacetime:
    1. Vacuum energy
    2. Radiation
    3. Matter
The radiation and matter in the Universe are treated like a uniform gases with equations of state that relate pressure to density.
    Once the assumptions of uniform energy sources and maximal symmetry of space have been made, the Einstein equation reduces to two ordinary differential equations that are easy to solve using basic calculus. The solutions tell us two things: the geometry of space, and how the size of space changes with time.

Open, closed or flat?

    If at every time, space at every point looks the same in every direction, then space has to have constant curvature. If the curvature was different at any point, then space would look different in that direction from every other point. Therefore if space is maximally symmetric, the curvature has to be the same at every point.
    So that narrows us down to three options for the geometry of space: positive, negative or zero curvature. When there is no vacuum energy present, just matter or radiation, the curvature of space also tells us the time evolution of the spacetime in question:

Circles of increasing curvature
A sphere has constant positive curvature.

Positive: The unique N-dimensional space with constant positive curvature is an N-dimensional sphere. The cosmological scenario where space has positive constant curvature is called a closed Universe. In this spacetime, space expands from zero volume in a Big Bang but then reaches a maximum volume and starts to contract back to zero volume in a Big Crunch.

Zero: A space with zero curvature is called (no surprise here) a flat space. A flat space is noncompact, space extends infinitely far in any direction, so this option also represents an open Universe. This spacetime has space expanding forever in time.

Hyperbola of increasing curvature
A hyperboloid has constant negative curvature.

Negative: The unique N-dimensional space with constant negative curvature is an N-dimensional pseudosphere. To compare this funny word with something more familiar, a hyperboloid is a two-dimensional pseudosphere. With negative curvature, space has infinite volume. The negative curvature option represents an open Universe. This spacetime also has space expanding forever in time.

    What determines whether a Universe is open or closed? For a closed Universe, the total energy density ρ in the Universe has to be greater than the value that gives a flat Universe, called the critical density ρ0. Let ω = ρ/ρ0. So a closed Universe has ω > 1, a flat Universe has ω = 1 and an open Universe has ω < 1.model-spacetimegeometry
   The above analysis only takes into account energy from matter, and neglects any vacuum energy that might be present. Vacuum energy leads to a constant energy density that is called the cosmological constant.
   Which behavior represents our observed Universe? To discuss the most recent observations, first we need to look at dark matter and the cosmological constant.

Where does dark matter come in?

   The matter in the Universe that we can see mainly consists of stars and hot gas or other stuff that emits light of some wavelength that can be detected by either our eyes, telescopes or complicated instrumentation. But for the last two decades, astronomers have been seeing evidence of vast amounts of invisible matter in the Universe.
   For example, there doesn’t seem to be enough visible matter in the form of stars and interstellar gas to hold most galaxies together gravitationally. According to estimates of how much mass would actually be needed to keep the average galaxy from flying apart, it is now widely believed by physicists and astronomers that most of the matter in the Universe is invisible. This matter is called dark matter, and it’s important for cosmology.
   If there is dark matter, then what could it be made of? If it were made of quarks like ordinary matter, then in the early Universe, more helium and deuterium would have been produced than could exist in the Universe today. Particle physicists tend to think that dark matter could consist of supersymmetric particles that are very heavy but couple very weakly to the particles observed in accelerators now.
    The visible matter in the Universe is much less than closure density, therefore, if there were nothing else, our Universe should be open. But is the dark matter enough to close the Universe? In other words, if ωB is the density of ordinary matter and ωD is the density of dark matter in the Universe today, does ωB + ωD = 1? Studies of galactic motion show that even including dark matter, the total only adds up to about 30% of closure density, with ω B making up 5% and ωD accounting for as much as 25%.
    But that’s not the end of the story. There’s another possible source of energy in the Universe: the cosmological constant.

What about the cosmological constant?

    Einstein didn’t always like the conclusions of his own work. His equation of motion for spacetime predicted that a Universe filled with ordinary matter would expand. Einstein wanted a theory where the Universe stayed the same size forever. To fix the Einstein equation, he added a term now called the cosmological constant, that balanced the energy density of matter and radiation to make a Universe that neither expanded nor contracted, but stayed the same for eternity.
    Once everyone accepted Hubble’s evidence that the Universe was expanding, Einstein’s cosmological constant theory was abandoned. However, it was resurrected by relativistic quantum theories where a cosmological constant arises naturally and dynamically from the quantum oscillations of virtual particles and antiparticles. This is called the quantum zero point energy, which is a possible source of the vacuum energy of spacetime. The challenge in quantum theory is to avoid producing too much vacuum energy, and that’s one reason why physicists study supersymmetric theories.
    A cosmological constant can act to speed up or slow down the expansion of the Universe, depending on whether it is positive or negative. When a cosmological constant is added to a spacetime with matter and radiation, the story gets more complicated than the simple open or closed scenarios described above.

What’s the final answer?

   The Big Bang began with a radiation dominated era, which accounted for the first 10,000-100,000 years of the evolution of our Universe. Right now the dominant forms of energy in our Universe are matter and vacuum energy. The latest measurements from astronomers tell us:
   1. Our Universe is pretty flat: The cosmic microwave background is the relic of Big Bang thermal radiation, cooled to the temperature of 2.73° Kelvin. But it didn’t cool perfectly smoothly, and after the radiation cooled, there were some lumps left over. The angular size of those lumps as observed from our present location in spacetime depends on the spatial curvature of the Universe. The currently observed lumpiness in the temperature of the cosmic microwave background is just right for a flat Universe that expands forever.
   2. There is a cosmological constant: There is vacuum energy, or something that acts just like IT, to make the expansion of the Universe accelerate in time. The acceleration of the Universe can be seen in the redshifts of distant supernovae.
   3. Most of the matter in the Universe is dark matter: Studies of galatic motion show that ordinary visible matter in stars, galaxies, planets, and interstellar gas only makes up a small fraction of the total energy density of the Universe.
   The Universe at our current epoch has (approximately)

Matter and vacuum density today

So right now the density of vacuum energy in our Universe is only about twice as large as the energy density from dark matter, with the contribution from visible baryonic matter almost negligible. The total adds up to a flat universe which should expand forever.

About these ads

About bruceleeeowe
An engineering student and independent researcher. I'm researching and studying quantum physics(field theories). Also searching for alien life.

12 Responses to Structure of Universe: Is It Correct?

  1. Nelson says:

    Universe is certainly inflationary and open. Dopler effect had already proved it. Bruceleeeowe, I’ve many evidences to support this idea and I believe you certainly aware of these ideas. Most tangible evidence to support this theory is datas obtained from hubble telescope shows that density of our universe is continuously decreasing or entropy of universe it increasing. Take mass constant.
    Density =mass/volume
    let mass is to be constant. Now it is easy to assume volume is increasing means universe is inflationary.

  2. bruceleeeowe says:

    Hey Nelson, there are certainly evidences that support inflationary universe and most of astrophysicists accept it. I’m one of them. But that is done considering dark matter and dark energy concept. I’ve described it in my next post.
    http://bruceleeeowe.wordpress.com/2009/11/03/string-theory-cosmology-review/
    Although finally mixing string theory, duality and braneworlds it come up with that.

  3. Pingback: Myth of Strange Matter And Black Hole at LHC « Bruceleeeowe's Blog

  4. Dilsgrordergo says:

    Generally I do not post on blogs, but I would love to mention that this post extremely forced me to try and do therefore! really nice post. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    By and large I will not post on blogs, but I would really like to say that this post extremely required me to try to to therefore! very nice post, you should create a manuscript on the subject. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    I can not keep in mind when i last wrote on a website. principally the communities didn’t grasp what they were talking about. your website has the foremost conversant people on this matter for quite a time. do you have different forums or sites i can post on? thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    educational post here, i do not like to write and waste my time when i surf merely as a result of the responses are idiotic or dim. i can tell this website has smart people on this subject. this is often as a result of of the moderator keeps the great explanation on. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    thanks for the knowledge on this web site, it extremely helped me out. a minimum of get a higher appreciation on this subject. smart input and queries add to the information. keep the unhealthy comment out of this blog to keep the standard up. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    i am not sure if i accept as true with all your comments however most do build sense to me. this can be the sort of web site i like to book mark and revisit. just as a result of i don’t agree with your explanation does not mean i can not browse them. i favor sturring up conversations by playing the devils advocate, all in fun of course. thanks a lot and see you soon. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Most of the comments and inputs are smart on the topic but i do have some problems with the dangerous questions. i recognize there is dumb question solely dumb answers however i would love to see more clued-up input. i can bookmark this website simply because i am an admirer of this material and will tell you folks are simply as ardent as i am. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    at the instant i am therefore busy that i can’t comment however your questions and comments have raised my interest enough to inquire into the internet website itself. i’ll bookmark you or your web site and contribute at a later date. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Hey. Thanks, this assisted me a lot! Truly, I am researching on this topic from past 5 half-dozen days however I wasn’t in a position to find any sensible info, I found some sites which were helpful however couldn’t realize any exact knowledge, thus is there any website you recognize that has more explicit answers? Please e-mail me. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Glorious blog with lots of useful information, Are there any web sites that you simply advocate I join? thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Typically I do not post on sites, however I would really like to say that this post really forced me to do thus! extremely nice input. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    In general I can not post on sites, however I would like to say that this post really forced me to do thus! extremely nice post, you should create a manuscript on the topic. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    I can’t bear in mind when i last blogged on a web site. largely the folks failed to apprehend what they were talking about. your website has the most clued-up people on this theme for quite a time. do you have got different forums or sites i will post on? thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    helpful post here, i don’t like to write down and squander my time when i surf merely because the responses are idiotic or stupid. i will tell this web site has smart folks on this topic. this can be because of the moderator keeps the good commentary on. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    thanks for the knowledge on this web site, it really helped me out. at least get a better appreciation on this subject. good input and queries augment the information. keep the unhealthy comment out of this blog to stay the standard up. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    i’m not positive if i consider all your explanation however most do create good judgment to me. this is the sort of website i wish to bookmark and revisit. simply as a result of i do not agree with your explanation does not mean i will not scan them. i prefer sturring up conversations by enjoying the devils advocate, all in fun of course. thanks a heap and see you soon. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Most of the commentary and inputs are clever on the subject but i do have some issues with the unhealthy questions. i understand there is dumb question only dumb answers however i would like to see a lot of up to date input. i will bookmark this web site simply as a result of i am an exponent of this material and will tell you people are simply as avid as i am. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    at the moment i am thus busy that i can not comment however your queries and comments have raised my interest enough to touch upon the net web site itself. i’ll bookmark you or your web website and have a say at a later date. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Hey. Thanks, this assisted me a ton! Actually, I am researching on this topic from past five vi days but I wasn’t ready to find any sensible data, I found some sites that were helpful but couldn’t notice any explicit knowledge, thus is there any website you know which has additional exact answers? Please e mail me. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Glorious blog with lots of useful information, Are there any google groups that you just recommend I join? thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Typically I don’t post on sites, however I would love to mention that this post really forced me to try to to thus! really nice input. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Typically I can not post on sites, however I would like to say that this post really forced me to try to to therefore! extremely nice post, you should produce a report on the subject. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    I am unable to bear in mind when i last blogged on a web site. mostly the communities failed to apprehend what they were talking about. your website has the foremost up to date individuals on this topic for quite a time. do you have alternative forums or blogs i will post on? thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    helpful post here, i don’t like to put in writing and squander my time when i surf simply as a result of the responses are unintelligent or dim. i will tell this web site has smart folks on this subject. this is because of the moderator keeps the great comments on. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    thanks for the knowledge on this website, it really helped me out. at least get a higher awareness on this topic. good input and questions raise the information. keep the unhealthy comment out of this blog to keep the standard up. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    i am not certain if i consider all your explanation however most do make good judgment to me. this can be the sort of site i like to save on my web browser and revisit. simply as a result of i do not agree together with your comments will not mean i will not browse them. i prefer sturring up conversations by enjoying the devils advocate, all in fun of course. thanks a lot and see you soon. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Most of the comments and inputs are smart on the subject but i do have some problems with the dangerous questions. i apprehend there’s dumb query only dumb answers but i would like to determine additional well-versed input. i will bookmark this web site simply as a result of i am a follower of this subject material and will tell you folks are just as avid as i am. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    at the moment i am thus busy that i can not comment however your questions and comments have raised my interest enough to investigate the web website itself. i’ll bookmark you or your web site and contribute at a later date. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Hey. Thanks, this helped me a lot! Really, I’m researching on this topic from past five half-dozen days however I wasn’t in a position to search out any sensible data, I found some sites which were useful but couldn’t find any definite data, therefore is there any site you know which has additional precise answers? Please e mail me. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Glorious blog with heaps of helpful data, Are there any google groups that you just recommend I be part of? thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Generally I do not post on sites, however I would really like to mention that this post very required me to try and do so! really nice input. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Habitually I will not post on sites, however I would love to mention that this post extremely required me to try to to therefore! really nice post, you ought to create a report on the topic. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    I can’t bear in mind when i last blogged on a website. mostly the communities failed to know what they were talking about. your website has the most conversant individuals on this matter for quite a long time. do you have got other forums or sites i will post on? thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    informative post here, i don’t like to put in writing and waste my time when i surf simply as a result of the responses are unintelligent or thick. i will tell this website has good individuals on this topic. this can be because of the moderator keeps the good explanation on. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    thanks for the information on this site, it really helped me out. at least get a higher knowledge on this topic. good input and queries increase the information. keep the dangerous comment out of this blog to stay the standard up. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    i am not sure if i consider all your explanation but most do build good judgment to me. this is often the type of site i like to bookmark and return to. just because i don’t agree along with your commentary does not mean i can not browse them. i favor sturring up conversations by taking part in the devils advocate, all in fun of course. thanks a heap and see you soon. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Most of the comments and inputs are sharp on the subject however i do have some problems with the dangerous questions. i understand there is dumb question only dumb answers however i would love to work out more learned input. i can bookmark this site merely as a result of i am a lover of this subject material and will tell you individuals are simply as zealous as i am. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    at the instant i am thus busy that i am unable to comment but your questions and explanation have raised my interest enough to treat the net website itself. i am going to bookmark you or your internet web site and add at a later date. thanks. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Hey. Thanks, this assisted me a ton! Actually, I am researching on this subject from past five vi days however I wasn’t ready to seek out any good information, I found some sites which were helpful but couldn’t notice any detailed data, so is there any site you recognize that has more exact answers? Please e-mail me. thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment
    Excellent blog with lots of helpful information, Are there any forums that you simply suggest I join? thanks, here’s a similar subject you’ll like Aquired Pulmonary Hypertensioneatment

  5. Mark Louis says:

    Well, principle of mediocrity was new for me, Bruce! Yeah..? Well what’s idea about intelligent of other creatures excluding human? Ok, skeptics say the ant is not intelligent or sentient. But I think without intelligence these creatures wouldn’t be capable of building such complex tunnels. Right? I think billions of years old civilisation would be a plausible scenario. Perhaps we are ant.

  6. AndreyDejavu says:

    Музыкальный ансамбль [url=http://dejavu-group.ru/index.php]Dejavu-group[/url] – это коллектив дипломированных вокалистов и музыкантов.
    [url=http://dejavu-group.ru/about_us.php]Deja Vu[/url]- один из лидеров в области организации и проведения свадеб, дней рождения, корпоративных вечеров, шоу программ.
    В репертуаре ВИА Дежа вю около 3000 песен.
    Только живое исполнение. Ретро, хиты 70-80-90-х, джаз, диско, поп, современная музыка, европейские хиты, фоновая музыка, шансон.
    Группа Дежа вю располагает мощной качественной аппаратурой, которая позволяет заполнить приятным и плотным уху звуком как небольшое помещение (фуршет), так и большое помещение (корпоратив до 1 тыс. человек).

    Андрей +7 910 483 8294

  7. Sometimes it’s really that simple, isn’t it? I feel a little stupid for not thinking of this myself/earlier, though.

  8. Pingback: Where Is The Missing Dark Matter? « Bruceleeeowe's Blog

  9. bigbangno says:

    I’m against Universe expansion:

    For example a question: – The universe expand in any radius at light speed: How can accelerate? At what speed expand the diameter (radius x 2)?

    This and more questions, doubts, proofs and hypothesis in http://bigbangno.wordpress.com

    Thanks.

  10. bruceleeeowe says:

    Hi bigbango, make it clear for me what actually you want to say.

  11. bigbangno says:

    I say really that I’m against all the Universe expansion theory and I speak over it in my web: http://bigbangno.wordpress.com

    I can’t believe in the expansion theory.

    For example in your text (with your permission): “Our Universe is pretty flat” – a flat universe is against Hubble’s law, only a spherical expansion can be according to it”

    “The cosmic microwave background is the relic of Big Bang thermal radiation” – it means that we see the final of the universe and by that is difficult to understand what is inflationary because the expansion is near light speed.

    ” Universe accelerate in time” is near impossible, if expansion of Universe is near of light speed: how can accelerate?, this would be many more less distance.

    How Universe expand near at light speed, 2 point A and B are separated always near at the same expansion indepentent of their distances, by that the expansion (expansion is not a travel, is that space intermediate expand) is decreasing: How cam be all this expansion synchronized and instantaneous according to Hubble’s law?

    If you like we can continue with email: lbiar@mail.com

    Thanks. Sorry if I disturb.

  12. Bari Socci says:

    Great articles & Wonderful a site…

    ———————
    California–Berkeley

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 157 other followers

%d bloggers like this: