how is universe expanding after the big bang.

[sunofawrx]

my idea is that it expanded like a sphere due to the fact that there was equal pressure outside the universe as it was expanding-or-it waz expanding soo fast that it didnt react to the pressure. but if im wrong then how DID the universe expand?

[Kyrisch]

We're talking about something with which even the greatest of scientists speculate... The people here can give you their opinions or theories, but you're not going to get hard fact or a direct answer to your question.

[Severian]

The standard idea is that it is expanding from the energy of the big bang itself. In inflation models the energy for a very rapid expansion is usually coming from a vacuum-expectation value of a scalar field.

[Mcgee]

Have you guys heard of fractals? Apparently, functions that describe fractals can also be used to describe the rate of expansion of the universe

[Thales]

Fractals are usually modelled on what mathmaticians term the 'Golden Ratio'. A quick google will give you a more comprehensive idea of the intricacies involved, but basically this golden ration shows up in nature all the time(from the ratio of your palm width to your upper arm length to the scaling of vorticies in a hurricane). Thus it is often proported that fractal equations, which are based on chaos theory are one of the few means by which we can manifest the complexities that are present in nature, from the seemingly deterministic(invariant) physical laws.

 

When specifically discussing how it relates to the big bang and the initial expansion (or more quantatively the patterns observed in the recent WMAP data), it is not suprising that certain fractal equations could be fitted to the data provided. This is however less groundbreaking than it first may seem. It is a fine example of what we call post-dicting (ie the opposite of predicting). Any valid scientific theory must not only withstand peer scrutiny but must also adhere to the condition of making measurable predictions. Therefore providing a test of the theory's validity.

 

Thats where alot of difficulty arises when talking about the universes genisis event. Most models generated to describe this event can adjust the relevant parameters to fit the current observational data. These theories however usually have little if any reasoning regarding why the parameters are at there observed values.

[sergey500]

Yep, this is nothing that was proven all based on thought and thought is (well my though) is welll one word, Red Shift (i am pretty sure that name). Since galaxy's move apart from each other they need to go somewhere, so space is expanding, or is saod to. Eventually it will stop expanding and will calapse on itself do to the immense gravity of all the object, this is known as the big crunch. But all this is speculation, so until proven otherwise i am right, you are right, everyone is right.

[Bubba]

While you’re spot on with the basics sergey500 it's actually a bit more complicated.

 

Firstly galaxies move apart from each other because the universe is expanding not the other way round. You should also bare in mind that they do not move apart in the way that 2 cars driving opposite ways down a street move apart, rather they appear to have more distance between them because the space they exist in is being "stretched".

The classic example is to think of a group of people on the surface of a giant balloon, as the balloon is inflated the amount of surface between the people gets bigger and they all move away from each other (the group becomes diffuse). The important point here is that from the view point of each person they are staying still and everyone else is moving away from them (a very simple, and hopefully educational, experiment that you can do is to draw some dots on a deflated balloon, measure the distance between them, inflate the balloon and measure the distance again. Also try to think about how each dot moves with respect to each other).

 

It is this "stretching" of space that gives rise to Red Shift. Light (photons) has a frequency and wave length (if this is new to you do a quick google) the frequency determines how many times per second the photon moves a distance of one wavelength. Light that we see from distant galaxies has a longer wavelength (or equivalently, lower frequency) than expected, we can infer from this that the photon has been “stretched” out, ie. must now move further the travel one wavelength. The term Red Shift comes from the fact that red light has a longer wavelength that the other colours, hence the light seems "reddened".

This effect is analogous to the Doppler effect for sound.

 

The real question being disscused now is, what is the RATE of expansion? if this expansion is accelerating the universe could keep expanding forever, but if the expansion rate is indeed slowing gravity could win out and cause the so called Big Crunch. If we can answer these questions then can have a much better chance at understanding the mechanisms that started and continue to drive the expantion of space.