About Expanding Universe

[johana]

Hi,about the expanding universe:

I have some questions that I do not get any answers for. Can somebody please help.

1. Why are the objects closer to earth(or our galxie) moving away slower than those far away? What do we have to do with the whole situation.

2. What force is eccelerating all that mass in space. If it is black matter, why are they evenly spread around the visible galaxy to achieve such even acceleration in all directions.

3. If you go backwards in time and reverse the expansion, then you end up with all matter in one heap, how do you start the expansion from there.

Thanks,

johana.

[toastywombel]

Hi,about the expanding universe:

I have some questions that I do not get any answers for. Can somebody please help.

1. Why are the objects closer to earth(or our galxie) moving away slower than those far away? What do we have to do with the whole situation.

2. What force is eccelerating all that mass in space. If it is black matter, why are they evenly spread around the visible galaxy to achieve such even acceleration in all directions.

3. If you go backwards in time and reverse the expansion, then you end up with all matter in one heap, how do you start the expansion from there.

Thanks,

johana.

 

Hi welcome to the forum, I will attempt to answer these questions for you one by one.

 

1. Not all objects in our galaxy (the milky way) are moving away from us. The objects within our galaxy are generally gravitationally fixed, as with other galaxies.

 

2. The universe is expanding and why is not exactly understood. When you say black matter, I assume you mean dark-matter and as far as I know that does not have much to do with the expansion of distances between galaxies and clusters of galaxies. Dark matter is un-seen, but we know it exists because it has gravitational effects on surrounding visible matter.

 

On to the point though, when Einstein published his theory of general relativity the equations suggested that the universe was either expanding or contracting. Einstein believed that the Universe was fixed and therefore created a cosmological constant to balance out the theorised expansion or contraction. However, when many astronomers began to look at the night sky such as Edward Hubble, they noticed that most of the night sky is red-shifted. This means that the light from these galaxies has a long wavelength, telling us that it is moving away. Hubble then discovered that galaxies further away were more red-shifted than galaxies closer to the milky way. This meant that the universe was not only expanding outward, but the further away galaxies were the faster they were expanding outwards. Many scientists have theorised that the expansion is due to the continued expansion of space-time from the big-bang. It is good to remember that the universe contains everything that exists, so to say that it is expanding outwards is not exactly correct. It is better to think that the distances between galaxies and super-galactic clusters are expanding. We cannot really say whether the universe itself is expanding because we have nothing to compare it to, it is the end all be all. The galaxies are not necessarily moving apart it is more that the space between them is stretching.

 

3. By suggesting going backwards in time and ending up with the matter all in one heap, I suppose you mean the point of singularity, where all matter, energy, force, space and time was contained within one point. It is really an unknown as to why the Universe started to expand. Some have theorised that the big-bang is part of a cycle of an expanding then contracting universe, with the universe expanding through the dissipation of a black hole, then sucked back together again by black holes. All we know is that the Universe at some was smaller and closer together than it was today.

 

Here are some interesting links to some information that might help you understand the Big-Bang Theory and the Expansion of the Universe:

 

http://en.wikipedia.org/wiki/Accelerating_universe

http://en.wikipedia.org/wiki/Metric_expansion_of_space

http://csep10.phys.utk.edu/astr162/lect/cosmology/expansion.html

http://en.wikipedia.org/wiki/Big_Bang

http://en.wikipedia.org/wiki/Gravitational_singularity

http://en.wikipedia.org/wiki/Dark_matter

http://astro.berkeley.edu/~mwhite/darkmatter/hubble.html

 

Hope this helps, welcome to the forum.

Edited December 14, 2009 by toastywombel

[johana]

Hi,

Thanks. As far as the red shift goes, I believe that electromagnetic waves traveling through space are continually being reduced in frequency, thus causing a red shift. I think the energy for the reduction is used for propulsion. In the end they will disappear.

I do not believe the universe is expanding.

Thanks for the links,

johana

[toastywombel]

Hi,

Thanks. As far as the red shift goes, I believe that electromagnetic waves traveling through space are continually being reduced in frequency, thus causing a red shift. I think the energy for the reduction is used for propulsion. In the end they will disappear.

I do not believe the universe is expanding.

Thanks for the links,

johana

 

Well I am afraid you are terribly mis-informed than. The Universe is expanding and it is a fact accepted by nearly the entire scientific community. I think your understanding of how light travels through a medium is wrong. Here is a link to gravitational red-shift, I hope this clears up your misunderstanding.

 

http://en.wikipedia.org/wiki/Gravitational_redshift

[mooeypoo]

Hi,

Thanks. As far as the red shift goes, I believe that electromagnetic waves traveling through space are continually being reduced in frequency, thus causing a red shift. I think the energy for the reduction is used for propulsion. In the end they will disappear.

I do not believe the universe is expanding.

Thanks for the links,

johana

Indeed, as toastywombel said so eloquently, your initial premise is absolutely wrong. And it's proven to be wrong. Light does not behave this way, we know and explain the behavior of light, and the explanation of red shift not only is *explained* in current physics, it yields perfect predictions.

 

 

Wikipedia has a VERY good starter on what Redshift *actually* is (usually I find that people think they know, and often don't quite know what it is), and the basic math behind it. If you want more information on how we know what we know, I can find more thorough examples:

http://en.wikipedia.org/wiki/Redshift

 

(That above one is the basics of what Redshift is, while toastywombel's wikipedia page is specifically about gravitational redshift.. they're *BOTH* right, and they're both good for the subject, I just figured you might want to start with the basics [redshift in general] and then go up a bit to specifics [gravitational redshift]).

~moo