Is the Universe Really Expanding?

A good place to start might be here.

Maybe everything is just shrinking....

Don't look back.

Thursday evening I followed a gaggle of jinormous hefties into Walmart and so I'd have to say "Yes, it is. Quite."

It seems to me that the jury is still out,at least for the next 15 years or so:

See the following link:

http://www.ox.ac.uk/news/science-blog/universe-expanding-accelerating-rate-%E2%80%93-or-it

Jorrie,

Thank you for sharing your insights in such an approachable way. I'm hoping you can shed some light on this expansion related question for me....

How well ruled-out are other phenomena that may cause or contribute to the apparent red shift in CMB that the standard model attributes to expansion?

Take these possibilities, for example:

1. If slightly greater density of material in space, lower levels of metals in the early universe, or perhaps a diminutive quantity of some particle (maybe neutrinos) early on that has since built up enormously, provided conditions that meaningfully changed the way the yardsticks worked in the past...couldn't some or all of the red shift we are interpreting as everything receding be actually gradual variation in those yardstick reaction over time that make more recent reactions appear with slightly higher frequency light?

2. If the fabric of space is expanding, how do we rule out the wavelength of light getting longer as the material through which it propagates is stretched? If wavelength stretches with space as it grows, even slightly, couldn't that be responsible for a large portion of the red shift?

3. The really big stuff in our neck of the woods seems to be getting more friendly, not more isolated: the Great Attractor, the Milky way, and the Shapley Cluster appear to be set on getting far more intimate. Doesn't this suggest our interpretation of the red shift might have a problem? What are the odds this area would be an anomaly? If expansion is happening, it seems that a strong confirmation would be available in the typical proximity of features decreasing as we look back farther in time. Has any corroborating observation shown a correlation between density of features and how distant/far back we look?

Thank you for you time.

"How well ruled-out are other phenomena that may cause or contribute to the apparent red shift in CMB that the standard model attributes to expansion?"

Pretty well in the sense that no other interpretation ties in so well with a wide range of observations. In fact, not even 'Young Earth Creationists" seem to challenge the fact that spatial expansion causes the observed comic redshift any more.

1. The model says that the early universe was much denser than today and takes this into account when observations are interpreted. Without going into the math, exactly 'how' is be hard to expalain.

2. The cosmological redshift IS "stretching of wavelengths' and it is due to the expansion of space, which could be loosely stated as the 'fabric of spacetime is stretching'.

3. Nothing that is gravitationally bound expands due to cosmic expansion, which is an effect only working on cosmological scales, i.e. roughly from the distance between us and the Coma super-cluster. I have written a Blog post on such detail many years ago: http://cr4.globalspec.com/blogentry/9562/Cosmic-Balloon-Application-V-Cosmic-Tidal-Force

The strong gravity between bound clusters can override the 'stretching forces' of cosmic expansion, depending upon their average density and size.

PS: too late to edit my prior post, but it may be worth your while to read the whole of our attempt to design the 'perfect CR4 cosmic balloon'. And if you have even more time on your hands, the other "applications" that flowed from that analogy, especially the one on redshift.

Thank you.

Nah, all that dark energy business stopped 12 billion years ago; but the evidence hasn't arrived yet. In another billion years, we can start chewing our fingernails over the Cosmic Crunch, which won't hit for another 13 billion years. Oh, dear.

When was the last calibration?

How reliable is that calibration source, anyway?

Maybe we need to break out the cosmic ruler and actually measure it. Who's turn is it? Well, who did it last.

Thank you. Great response.

Nice reply!

These cosmological yardsticks are used to calibrate each other from smallest to largest, where they overlap. This is then used to refine the value of the Hubble constant, which is ultimately used to determine the distance to any object for which the redshift is known.

If it does expanded, where are we situated in that cloud of constellation and galaxies, center or somewhere on the edge?

Hi Jorrie,

Good to see you here, and also on Physics Forums. You have some good answers. It's best not to feed the trolls with the small brains, especially about infinity. Even you and I don't always agree on that.

-S

You extend my regards to Chester Miller.

Was it not possible to know the gradient of surrounding stars, where they go?

Say for example our galaxy was one of the drops of water going left. We see who's coming towards us and going farther.

But, I wonder if that would even possible to determine. I am not quite knowledgeable about this.

Just for grins, assume we were within reach of the 'edge'. What's beyond it?

Yes, this is a trick question.

For tomorrow's class, we will discuss the difference between "nothing" and "nothingness".

Ok, start with this guy.

He got the misleading idea of nothing, which not actually nothing. I am a little bit confused.

But this guy Prof. Shankar made sense

(see 0 to 1:30 sec) of this video

What confuses you about Krauss's talk? He is a great speaker. He explains everything in a simple straight forward way.

Perhaps you are confused because you have decided his ideas are misleading. If you are confused, how can you be confident enough in your understanding to decide his ideas are misleading? Perhaps some ideas you developed prior to hearing his speech were misleading and at odds with what he presented.

My answer is professor's Shankar's wits, see 0 to 1:30

You can not use proton analogy with the universe (Is there proton in space between the moon and the Earth? No, there's none). Space without matter is nothing, void. And, it will accommodate all there is including EM spectrum. EMS are dead energy. Dead energies could no longer be used and is being wide spread to the vastness of space.

It's true that the universe is a close universe and it's obvious what the boundaries are. The absolute zeros. (Absolute nothing,->Pressure and Temperature) Ground state. And with it comes two extremes of opposite symmetries (+/-), down and above, where ever you may go. An unlikely pair is always coexistent.

But, how can he say the universe is flat or spherical and etc.? It's an imagination, a wild fantasy. Could be a sci-fi. and I decline to think that is how it is.

By 'professor Shankar's wit' it would appear you are saying most other people are not too bright.

I get the feeling that professor Shankar was merely keeping the tone light with some humor aimed at no one in specific. He seems like a pretty bright and capable guy, which would suggest in light of work by Dunning & Kreuger as well as others that, in contrast with your apparent position, he is more likely to underrate his own talents and overrate the talents of others.

Hey, if you are able to update your understanding with corrected information, here is some: there are protons between the Earth and Moon.

In science, I just don't get star struck at all. Ordinary people do. I mean I am quite ordinary, but the truth is there somewhere. Needless to say whose mouth is it coming from.

One could be a scientist then some part of self is not.

The idea of space is simple as void. Some people just do not get it that simple. I believe the universe runs in absolutely in perfect math equations and space is a proof it is perfect. Oh, I am a believer of nothing and perfection.

Afterall,

F-ma=0, F-P/A=0, ...so on and so forth. Even if you add up all drag and counter forces against it. You would end up all your working equation equated to zero. Nothing just works perfectly fine every time.

_{"There are protons between the Earth and Moon."} -This could be true, but doesn't necessarily true to the concept of space and the universe.

Watch the movie "They Came From Beyond Space".

Four elephants on the back of a turtle. And from there it's turtles all the way down.

While it is an interesting question, almost philosophical, does it really matter?

To date the most that I am aware of is that the red-shift is greater than "expected", whatever that means.

And if it is expanding at a greater rate than originally thought, what is the significance? Calculation error?

Will the Universe hit some sort of barrier and start to collapse on itself?

Is it possible that that is where all of the energy that supposedly comprised the "Big Bang" came from?

Regardless, I don't think any of us, or even the Solar System will be around to answer, or for that matter care.

"The important thing is not to stop questioning. Curiosity has its own reason for existing." A. Einstein

Scientists <...know what the universe is doing at the present time...> because of careful observation. <...The further they look, the faster it is accelerating...> because of the red-shift of the hydrogen light colour characteristics from stars within distant galaxies. Generally, the farther away a galaxy is, the greater the red-shift. Therefore the universe is expanding.

Friedmann equations.

Hubble deep field.

The information is from long ago. You can say that the universe WAS expanding, but not necessarily IS.

Ah! Good point. Thanks.

That is exactly what I was saying in my original post:

"..They really don't know what the universe is doing right now.

All of our information is millions or billions of years old."

Some of the stars that we observe have completed their life cycle by now,and are cold and dead.

We are always getting yesterday's news.

Insofar as what exists beyond our visible universe,I refer to ancient world maps "Beyond here there be monsters".

Monsters in this case are made of our ignorance.

Another possibility would be that as light travels great distances over long periods of time, the wave slowly but continually relaxes to longer wave lengths and slower frequency.

The red shifts would work out similarly. The more distant in time/space the further red shifted the light would be.

In an infinite system you can only say that the region we can observe is accelerating. I have heard about the big bang and the big crunch, I always thought it is this big bang and that big crunch, one of many.

Given infinite time and infinite space what I believe we are seeing is expansion here and there is contraction there. Look at it as cosmic weather patterns with regions of highs and lows, cold fronts chasing hot fronts.

Drew K