Expanding universe Definition and 230 Threads

We are told the universe is expanding because galaxies are red shifted and that it is a doppler effect. Do blue shifted galaxies contradict the idea of an expanding universe?

The evidence points to an expanding universe, we tell this by looking at the redshift/distance relationship, objects further away are receding faster, with their redshift and distance at an almost linear relation. My question is, the photons emitted by those objects that we are just now...

The question in the title of this thread was triggered after reading a couple of papers that, while accepting the assumption of an expanding universe, seem to question whether space itself actually expands. These papers are: http://arxiv.org/abs/0707.0380" Reference: ‘The Expansion of...

The universe is expanding. We know this because light from distant stars is red shifted indicating that they are moving away from us. Here is the nugget that just occurred to me. Lower frequency light carries less energy so if all the light emanating from a star shifts further down in...

Hey, After watching a show on TV about expanding universe and dark matter&energy, I wondered the following. In the program, it was mentioned that the universe is expanding at an accelerated rate. This was measured using spectroscopy, comparing Type 1A supernovaes at different distances. It...

in an expanding universe is all matter cooling? also, is has gravity become weaker over large distances? does isotrophy apply to the natural forces?

Anybody out there with info? What part of the expandable universe have the galaxys been observed to be flowing to a pecticular direction. Been looking for information site on topic. Thanks

This relates to Doppler's effect. The phenomenon: It is quite simple and says that light emitted from a moving object will be redshifted when the object is moving away from us (earth) and blueshifted when the object is moving towards us (earth). I was thinking of this phenomenon and arrived...

Hey so I've started learning some cosmology and i have a question about the expanding universe. So i was told to picture a 3D graph with time on the vertical axis and space making a plane perpendicular to the vertical. I am using the metric where the diagonals are (1,-a,-a,-a) where a is a...

How did scientists discover that the universe is expanding? This theory doesn't make much sense to me. What could be pushing the planets and galaxies away from each other? I just started reading magazines about astronomy such as "Sky and Telescope" and have started reading my physics textbook...

I was wondering if someone agrees: Is it possible that on the other side of the black hole is an expanding universe? It seems an iteresting idea to me: in our universe a star collapses onto itself with an explosion, creating a black hole and on the other side a big bang happens with matter...

For starters let me say that reading about and pondering cosmology is only a hobby, I have no formal education in this arena, although I am returning to school this spring to do just that. That being said, the following query may be foolish for some basic reasons I have missed, or not come upon...

How is energy conserved in an expanding universe? As space expands between, say, stars in a galaxy, don't they gain potential energy in the gravitational field of the galaxy? Which mechanism lessens the total kinetic energy?

This has been puzzling my mind for a long time. How do we really know the universe is expanding? Based on observation? Redshifts? Observation based conclusions cannot be made IMO. We have observed the universe for a few hundred years and that is way too little to use to predict 13+ billion...

The Two Concepts The [PLAIN]http://en.wikipedia.org/wiki/Speed_of_light"[/URL], through expansion and inflation, as one of the fundamental aspects of the model. The conundrum is that these two concepts seem to be mutually exclusive. The purpose of this article is to bring this conundrum...

Hello all. I am a newcomer on the forum and no major math or astronomy knower. But I have often thought about this issue I would like to ask about here. From what I understand the Big Bang happened from a singularity expanding outwards (or exploding). As the speed of light is considered a...

I would appreciate assistance in answering the following. Does the existence of time depend on the universe expanding at an accelerated rate?

I have been reading Cosmology related topics for about eighteen-months. The other day I was reading from the following website: http://wmap.gsfc.nasa.gov/site/faq.html Under Item 2. is this sentence. "Astronomers see galaxies moving apart from one another: space in the universe is...

For those of you accepting singularity, When the big bang occurred there was a massive amount of energy exerted. Did this energy exert a positive acceleration on everything, meaning that it will continue to expand forever? Or did it have a negative acceleration, like throwing a ball up in...

In our universe, is the shortest distance between two points a straight line or a hyperbolic curve? (I'm debating this with my teacher) Of course you're going to ask me for the definition of a straight line but I don't think I can define that relative to a curved line without getting...

Hi all, I was watching some online video lectures from the Quantum to Cosmos festival, where they discussed the expansion of the universe and the problems this brings in physics. Problems like the need of dark matter and what the mysterious force is that accelerates this expansion. I've been...

Sorry if this question has been reproduced elsewhere. If the universe expands greater than the speed of light, c, will a light ray from a distant object never reach us? Lawrence Krauss gave a nice presentation and commented about this, but this has thrown my nose out of sorts because I think...

When people say the universe is expanding, do they mean that the galaxies etc are moving farther apart from each other (i wonder how fast o.O)? or does that mean that more matter is being produced somewhere in the universe, causing it to expand...

The 'measurement' of the radial expansion of the moon's orbit is 3.8 cm/yr http://curious.astro.cornell.e...uestion.php?number=124 but that measurement is only slightly more than the Hubble constant (the rate that the universe is expanding) Here is my calculation: Hubble expansion...

I know there are a lot of these questions, but please bear with me, I couldn't really find these precise scenarios elsewhere. First of all, am I correct in saying that if we took a distant galaxy that was highly redshifted, and had it emitting light pulses to us once every second from its...

Are there any alternative theories/explanations of why light from distant galaxies is redshifted by an amount proportional to the distance away from us, other than the popular universal expansion explanation? Maybe some theory about light losing energy when traveling over such large distances...

Hi, I have a question about the redshift caused by the expanding universe. I am not a physicist and reading books and articles about physics is just a hobby so I apology if this is obvious to most of you. I have read somewhere that the light from far away galaxies is redder than light...

As I understand things, the following are true: The further away in space we observe, the further back in time we are looking The further away in space we look, the faster galaxies are receding from us If these are true, doesn't it indicate that the rate of expansion of the universe...

Why the early universe started expanding

We hear that the universe is expanding, and this accounts for red shift as all objecsts are accellerating away from each other. But I have also heard that it is the space itself, of which the universe made, that is expanding - not that things are moving in that space. If so, then the...

Astronomers believe that the universe is expanding because of the measured doppler effect redshift of light emitted from distant stars in other galaxies, correct? Do they have other reasons for believing that the universe is expanding? The stars in our own galaxy are known to not be traveling...

I wonder how the expansion affected the solar system. Yes, I know that gravitationally bound objects had already "adapted" to the expansion. But it had adapted to the linear expansion - this assumption is valid only when we analyze a limited period of time. But the rate of the expansion...

A common misconception from friends studying outside a Bsc. is the impression that our universe is expanding out in space, that space is infinite and that simply matter traverses into voids. They seem to have a hard time understand that the expanding universe is space itself expanding and that...

Hello, I am trying to understand that in order for the universe to be expanding that galaxies at further distances must be moving away from us at faster speeds than galaxies closer to us. It seems enough that all galaxies are moving away from us (or each other if observed from another galaxy)...

reading thru some of the posts I havn't really found the answer. The universe is expanding but is it a constant rate or is it an accelerating rate?

As we know we see the universe at points in its infancy when the universe was born however for us to be here to see the light we must have either 1) Gone faster than the speed of light and 2) always existed here somehow. Is there a general consensus that space actually expanded faster than...

I have certain doubts about the notions of expanding universe: 1. Are both space and time intervals expanding or only the space interval expanding? According to FRW model, only space is expanding. Is that correct? 2. At what rate is this expansion taking place? When I talk to my friend, I...

Assuming we are not at the center of the universe: If V is the vector from the center of the universe to us, then -V would be the vector from the center of the universe in the direction away from us. Wouldn't a star (or whatever) on the -V vector be accelerating away from us at a larger rate...

I was wondering if anybody knows of any experiments that differentiates between tired light and an expanding universe?

This may be a little crazy of an idea, and I am posting it just for fun, so don't take it too seriously. What if the universe was not expanding, but instead we along with all other objects are shrinking?

Now, It is has been derived from GR that the pressure within a substance contributes to it's gravity just as it's mass density does. But I had a thought Suppose you have negative pressure. A simple example I can come up with would be when a solid object is stretched to support a hanging...

Has anyone ever considered the possibility that the perceived Doppler effect of light from distant stars/galaxies is not caused by movement of the emitting bodies, but rather a side effect of light traveling extraordinarily long distances under the week gravitational force of the entire...

Dear all, i'm very new to cosmology/astronomy branches of physics. i've one simple question. it's known that the universe is expanding and i suppose the measurement was made by Hubble for which he won the nobel prize. but also, i recently learned that there're black holes at the centre of...

Does gravity create a wake in subspace? If so would this wake produce a undetectable energy source or negative pressure in subspace which would indirectly lead to the expansion of all atoms in normal space that sit upon it? If the universe's expansion is accelerating then could this be...

didn't know where to post this. i recently learned that the universe is expanding and it is doing this symmetrical... and all points are accelerating away depending on their distance in space. ok this is ok but then i thought about it alittle bit... doesn't this imply that a galaxy far enough...

Empty space contains a surprising amount of matter in the form of gas. I couldn't tell you the number because I can't find it online but it is there. Has anyone thought that the universe might be expanding because this gas in empty space far outnumbers the mass of galaxies and that the gas is...

Am I right in saying that exotic matter or energy is responsible for the accelerating expansion of the universe? If so, would that mean that it's getting further and further away from us? Could a civilization in the future somehow get their hands on exotic (or dark, or negative) matter...

Hi everyone, just signed up to forum so not too sure of what to expect but can I ask one question that has probably been thrashed to death in the past and it is: Taken that the UV is expanding, what is it expanding into? I was told once that it created space as it expanded but that does not...

If I remember right, I have on several occasions read that the second law of thermodynamics is a consequence of the very unlikely initial state of the universe, and that it is this "potential" that drives the universe. I would rather give the credit to the fact that the universe can expand...

"General Relativity teaches us that Space is expanding." Ok, so as we discussed in a previous thread, a literal interpretation of this is nonsense. "Empty space" does not expand. Rather, objects move apart. Fine, but the universe as a whole is expanding, right? (Of course, we have little...