Why is the universe expanding?

[HerbertSu]

Can somebody explain to me why the universe is expanding? Or maybe just some speculations to why it's expanding. Putting the explanation in layman's terms would also be helpful. Thanks!

[IM Egdall]

Einstein's field equations of general relativity has proven to be the most accurate theory of gravity to date. And when it is applied to the universe as a whole, it predicts the universe is not static -- it must change size over time.

 

In 1928, I think, Georges Lemaitre combined Hubble's galaxy distance measurements with known redshiift data to show that in general the further away a galaxy is the more its light is redshifted. Lemaitre proposed this as evidence for the expansion of the universe as predicted by general relativity.

 

Observations of supernovae in 1998 and later observations show the expansion of the universe is speeding up over time. The cause of this acceleratation-- dubbed dark energy -- remains a mystery.

 

I hope this helps.

Edited July 29, 2012 by IM Egdall

[Airbrush]

The explanation as to why the universe is expanding is the Big Bang theory. The Big Bang was so great that it overcame the gravitational effect of all the matter in the universe. And the expansion is observed to be accelerating.

[HerbertSu]

So basically scientists think this "dark matter" is what's pushing the universe to expand?

Edited July 31, 2012 by HerbertSu

[zapatos]

So basically scientists think this "dark matter" is what's pushing the universe to expand?

No. The expansion is believed due to two things:

 

1. Dark energy as mentioned by IM Egdall, and

2. The continuing motion that originated with the Big Bang as mentioned by Airbrush.

 

The motion due to the Big Bang is what predominated early, and motion due to dark energy is presumed to dominate the continued motion (and acceleration) now.

Edited July 31, 2012 by zapatos

[alpha2cen]

We can observe the expansion in the Supercluster by using red shift phenomena.

Edited July 31, 2012 by alpha2cen

[alpha2cen]

Accelerated expansion is well known phenomena. But some doubt remains. How to calculate the red shift? How about adding new parameter, which is related to time dependent factor(old light is more red shifted than newer one), to the red shift equation, and obtaining parameter value from the data by using the parameter estimation method? And then, calculate the parameter sensitivity from the equation. Is this nonsense? This will be a good paper. Because, after this paper no one will have any doubt about the great finding.

Edited August 1, 2012 by alpha2cen

[Autumn_Man]

Can somebody explain to me why the universe is expanding?

I think that the Big-Bang started the whole process by sending out a huge amount of energy at an event billions of years ago. It used to be believed that it was the momentum of the explosion that is carrying matter away but lately astrophysicists and cosmologists have discovered that the expansion is occuring at an accelerating rate. That can be due to various reasons such as the presense of a positive cosmological constant (which is more of an description than an explanation). Another reason would be negative pressure. Such sources act as negative active gravitational mass and is thought of as gravitational repulsion.

[JohnStu]

they say it is due to the Big Bang and dark matter

[ACG52]

they say it is due to the Big Bang and dark matter

 

 

Dark energy.

 

Dark matter is something else entirely.

[alpha2cen]

The explanation as to why the universe is expanding is the Big Bang theory. The Big Bang was so great that it overcame the gravitational effect of all the matter in the universe. And the expansion is observed to be accelerating.

 

Based on current redshift concept.

 

Time lag effect

neighboring Super Cluster--------------------- recent light------------------moving slow

...

near Super Cluster----------------------------- near past light---------------moving fast

...

far away Super Cluster------------------------ old light ----------------------moving more fast

...

very far away Super Cluster ------------------ very very old light------------moving very fast

 

+ geometric location effect

Edited August 7, 2012 by alpha2cen