[IzzieC (OP)]

Patrick asks

I've been told space is expanding at an ever-increase rate. Is the rate of expansion the same across the whole universe and what would be the current rate of expansion? Also, why don't I see the effects of space expanding around me? My two-year old is expanding, but last time I checked my wife was about the same size.

What do you think?

[Janus]

The expansion of the Universe is not the applicable over all scales.   It only applies at scales large enough that local forces aren't strong enough to overcome it.  Your 2 year old son is not expanding because the bonds between the molecules holding him together prevent it.  The solar system is not expanding because the gravity of the Sun prevents its.  Our galaxy isn't expanding because its own mutual gravity holds it together.   Even our local group of galaxies is gravitational bound together against the expansion of the universe (Evidence of this is the fact that our neighboring galaxy of Andromeda is actually decreasing its distance from us).  It isn't until you get past the scale of galaxy clusters that these clusters are far enough apart that their gravitational attraction to each other is not enough to stop them from being pulled along with the expansion of the universe as a whole. 

[Bill S]

.....what would be the current rate of expansion?

I understand t the expansion rate of the Universe is reckoned to be 67.3 kilometres per second per megaparsec.  You probably know that a megaparsec is defined as a distance equal to 3.26 million light years. 

[trackpick]

Thanks for the replies to my question. 67.3 kilometres per second per megaparsec is a really minute rate of expansion - something like 2.18*10^-13 % expansion per second? So even if we didn't have forces holding things together, presumably we'd never notice the effects locally...

My follow-up question was how it can be that, with a tiny expansion rate like that, we can have galaxies flying apart faster than the speed of light due to expansion! Is the answer that the further the distance the more intervening expanding space there is? About 4458 megaparsecs for it to be speed of light?

[syhprum]

"One parsec corresponds to the distance at which the mean radius of the earth's orbit subtends an angle of one second of arc".
A parsec is not defined as 3.26 lights years that is its approximate value

[opportunity]

Is it possible to suggest that the idea of the "expanding universe" theory is problematic on large scales, as technically the faster than light expansion and those objects there will never be visible to us...........problematic for a "theory of everything". As, how can a theory of everything be a theory of everything if there are objects out there we can't account for because they are in the realm of the faster than light expansion of space? The mechanics of objects in that faster than light expanding region could really confirm or deny a big bang or not, yet we can't see that because it is faster than light, right?

As we are lead to believe, there was an initial expansion, an infinitesimal array of points of space expanding, then local laws set in, , "then" faster than light expansion steps in "not" for a perimeter, because there is no perimeter, every point in space is the perimeter. That's another problem. To say local laws are above and beyond the accelerating expansion it must be said is nonsense.

[Bill S]

A parsec is not defined as 3.26 lights years that is its approximate value.

I plead guilty to sloppy use of language!

[Colin2B]

..how can a theory of everything be a theory of everything if there are objects out there we can't account for because they are in the realm of the faster than light expansion of space?

But they are accounted for, even if we can’t see them.

That's another problem. To say local laws are above and beyond the accelerating expansion it must be said is nonsense.

There must be a misunderstanding here. Do you mean local measurements?

[Bill S]

  how can a theory of everything be a theory of everything if there are objects out there we can't account for

Surely, a theory is a scientifically/mathematically constructed idea about how things might be, or might work.  If all the relevant factors were actually known; their description would be a factual account, not a theory.

[jeffreyH]

Space is not something that can be seen. The objects that populate space can be seen and not just in the visible spectrum. Space is dimensional in a similar way that time is. We can determine the distance between objects. That does not mean we can actually 'see' it. Around 99% of anything is empty space. What we can actually see is an illusion in this sense.

[PmbPhy]

Can we see space expanding?

Space can't be seen so no. What we see is objects which are in the space that is expanding and we see those objects receding at an increasing rate.

[opportunity]

The responses since my last post in this thread haven't nailed anything relevant to the question the post is asking.

Colin, "how" can objects that aren't visible be understood? What if the proposed big bang had a faster than faster light speed "shell" at the time everything went faster than light in terms of spatial expansion? How do we know? Whats a "shell" ? That's my point, "how would we know"? Plus, the valid question of space being expansive "everywhere", as was the condition of the initial big bang, has not been addressed. Faster than light expansion "has to" be relevant to any point in space anywhere. There's no "perimeter", that's an idea of reference of an observor. And "local laws", well, yes local measurements give rise to local laws that are "understandable".

Bill S, yes, that's fast. Almost absurdly so.

Trackpick, check your calculations.

As absurd as it sounds, the CMBR and red-shift effect may not be due to a proposed big bang event. If the jury isn't still out there, allowing such a possibility, we could be missing out on key insights. I know of a theory that clearly states the CMBR and red-shift effect are not due to a big bang effect. That theory requires though to prove a new phenomena science can't predict with its current models, obviously (and I won't be talking about that theory in this section). If that theory can though, science is in trouble on the "expansion of space" subject.

It's good though to hear the reasoning behind why our own space has no measureable expansion here on Earth, yet elsewhere in galaxies far far away its off the charts, especially in places we are not allowed to see owing to the faster than light effect.

The only evidence for any expansion in this reality of ours is "cynicism"; it pushes us away further from each other, yet some of us don't register that. "Cynicism" is one of the only things that I consider to be pre-meditated, and thus faster than our own time, sadly, yet it has nothing to do with the expansion of space unless you're medicated for that purpose (and yes, who knows?). Thankfully, science isn't designed to be cynical.

[Colin2B]

"how" can objects that aren't visible be understood?

Well, this is a problem faced by science for a long long time.
Newton couldn't see gravity but he could observe its effects and describe its actions.
Consider Copernicus. No one could send out a probe to view the solar system, but there were anomolies in the motions of the planets (moveable stars) that puzzled even the ancient Greeks. Brilliant Arab mathematicians came close, but Copernicus and his contemporaries spent a great deal of effort on observation, meticulous record keeping, and some very neat mathematical analysis.
Obviously, there are some things we will never be able to go out and test and many cosmological ideas are current consensus of those working in the field. I for one am very willing to listen to anyone with an alternative who has put in as much mental effort and analysis as, say, Alan Guth or Stephen Hawkins - people who really understand the detail. Problem is there are a lot of uninformed guesses out there which don't take account of basic tested physics, but that's what New Theories section is for. Good ones are few and far between.

[PmbPhy]

Colin, "how" can objects that aren't visible be understood?

Simple. If we are speaking about something which we hold to exist then we hold that to be true because it interacts with its environment. We understand dark matter (which can't be "seen" in the conventional sense) because it has gravitational mass and as such has an effect of the orbits of matter in galaxies. We detect things like neutrinos (which can't be seen) by observing what creates it and use principles such as conservation of energy and momentum to detect their existence and location

What if the proposed big bang had a faster than faster light speed "shell" at the time everything went faster than light in terms of spatial expansion?

The universe doesn't have a shell. However its quite common to observe matter in the universe racing away from us at speeds greater than the speed of light. And you can't even speak of speed if you don't at the same time state what the speed is relative to.

How do we know? Whats a "shell" ? That's my point, "how would we know"? Plus, the valid question of space being expansive "everywhere", as was the condition of the initial big bang, .... etc

You can learn all you'd like to by picking up a book on astronomy. It's too unwieldy to explain everything one needs to know to understand the big bang theory in one thread and threads are not used to teach theories but to answer questions about a theory which one took the time and effort to start learning. Have you made such an attempt? From what I see so far you don't seem to know what "big bang" means or what it means for the universe to expand. Far too many people make the mistake of thinking that the big bang theory is about an event, i.e. a "bang" which started it all when in fact no such event is to be found in the big bang theory. Not because we don't believe that such event occurred but because there's no way to determine that such an event happened. A person in another part of this forum made the same mistake. However they did not like being corrected.

[opportunity]

Well, whoever that was, lets hope they find an answer to what we're still debating.

No expansion here (in this quadrant of a universe) is a red flag.

Are we ever going to see expansion here?

[PmbPhy]

Well, whoever that was, lets hope they find an answer to what we're still debating.

No expansion here (in this quadrant of a universe) is a red flag.

Are we ever going to see expansion here?

I find it odd to be discussed in the third person in a forum like this. Lol!

[jeffreyH]

@opportunity While you are babbling I am studying the Wronksian theorem. You should try learning.
https://en.m.wikipedia.org/wiki/Wronskian

[opportunity]

Ok, I wasn't trying to bake any muffins here.

How's the studies going though?

[PmbPhy]

Well, whoever that was, lets hope they find an answer to what we're still debating.

The answers are very well known so nobody needs to find them.

[opportunity]

Colin, "how" can objects that aren't visible be understood?

Simple. If we are speaking about something .......
.......A person in another part of this forum made the same mistake. However they did not like being corrected.

Then, I said "Well, whoever that was, lets hope they find an answer to what we're still debating."

Ok, so that person was you......that's the alleged third person I was referring to. Should have been obvious. It was in direct response to your reply. Apologies if you thought I was making "you" the third person. I mean, when I read my reply to yours I still can't see how I made you the third person......

Maybe this topic is a little hot for some and blinds us from seeing the facts?

I'm still a little stunned no one has answered my questions though other than saying what I have allegedly done wrong in terms of forum protocol or how great they are with what they're currently studying. Try studying Medicine, many many abstract concepts there that are "factual". I've had the benefit of not only studying Medicine, yet understanding the "flaws" in Medicine theory, namely taking an incorrect history. For instance, much of Medicine is based on taking a good history, yet the history the patient provides is not exactly honest most of the time. I know this having worked in Medical Insurance and seeing some of the claims and associated facts that come through that treating Doctors themselves are not aware of. I'm no stranger to facts.