Newbie
Hey everybody ...
My first ever post, so I thought I'd begin with a question that's puzzling me.
If the universe is expanding, does this include the stars within our Milky Way galaxy?
If so, how is the black hole in the center of our galaxy explained? Is it pulling us in, or are we expanding ?
Thanks in advance.
Order of Kilopi
Yes space is expanding even right here in our solar system.
01101001 corrected my calculation here which puts the expansion of the universe moving the Earth away from the sun at a rate about 10m/year.
So taking out colliding with Andromeda and our sun blowing up, etc, the earth is receding from the sun. I'm not sure about the rate at which the earth would be pulled into the sun. From my understanding the earth would recede from the sun even with out universal expansion just like our moon is from us.
Established Member
Err, it's not really the case that the Earth is moving from the sun at that rate due to expansion. What you calculated would be what happens in the absence of any other forces. And I'm reasonably sure there's at least one major force involved in the earth/sun system...Originally Posted by WayneFrancis
Order of Kilopi
It isn't.
(If our own Sun was turned into a black hole - of the same mass as the Sun already has - we'd simply keep orbiting it as we do now.)
The Gravity of the stuff in our Galaxy, though, is what's stopping the Galaxy "expanding" the way the Universe overall is.
Welcome to BAUT, by the way.
Get up, a get-get, get down.
Order of Kilopi
Correct, sorry. The dynamics within the solar system is very complex. All the other bodies pulling the earth/moon system every which way as we all orbit the Sun. Throw in that 10m/yr and it really amounts to nothing.
I just did the calculation for the earth moon system. I thought it would not be that much but it works out to 0.027383095m or 2.7383095cm/yr
Now we measure the moons recession rate as 2.16cm/yr
It is expected that the moon will recede because of the orbital mechanics. So, I'm missing something here. That is if I did the calculations properly.
Banned
Welcome 'TopRanking'
The answer can be simple or complex... depending on how pedantic you feel like being. Simply put No. This solar system and this galaxy are not expanding. Gravity of the mass and orbital velocities govern those things. The universe is expanding and at a ever faster rate., but, only away from gravity bound objects.
Now it must be said that in actual fact everything is expanding... ( so they say )
You will note the discussion above regarding the Earth Sun distance... at 2.7 cm per year rate of recession... don't cough you might change the distance.
Established Member
Hi and welcome TopRanking,
This issue has been discussed much here. I can recommend this thread and in particular Spaceman Spiff's post at the end for the latest views and more links.
Newbie
Thank you for everyone's helpful answers ...
Established Member
Hi TopRanking
Welcome
The mainstream model describing the expansion of spacetime is a limited expansion model in that the expansion of spacetime is assumed to stop at the boundary of gravitationally bound galaxies. The spacetime within the atom is also assumed to not be expanding, due to binding forces.
(This assumption is wrong, but this is my Against the Mainstream model, which I can’t discuss).
So, according to the mainstream model, a 10 meter expansion in one year between the earth and the sun does not happen due to gravitational binding forces.
(Note, if the expansion were to include the atoms making up the ruler, the ruler would also proportionally expand and there would be no measured 10 meter expansion in the distance between the earth and the sun over a one year period.)
The following conversions for the observed rate of expansion, Ho may be helpful.
Ho = recessional velocity / distance between points at time of emission;
(Recessional velocity assumed to be created by expansion of spacetime with no “real” or what astronomers call “peculiar” motion involved that would affect the observed red shift).
at Ho = (70 km) / second) per megaParsec) =
0.021 meters/second per lightyear =
0.34 x 10-6 meters/second per AU.
2.27 x 10-18 meters/second per meter
Two points separated by 1 meter would take about 14 billion years to increase their separation to 2 meters.
Snowflake
Order of Kilopi
I thought only non-gravitationally bound galaxies are effected?
Established Member
Everything is affected, but gravity has a bigger effect at scales smaller than galaxy clusters.
Established Member
This is not the case, even at the scale of the atom, space is expanding (a very very tiny amount).
Please don't base your answers in the Q&A forum on ATM theories.(This assumption is wrong, but this is my Against the Mainstream model, which I can’t discuss).
Think of it this way. If expansion is accelerating the earth away from the sun by amount X, and gravity is accelerating the earth towards the sun by amount Y, then the orbit of earth will be based on the sum of those 2 forces. That sum isn't changing, so neither is the orbit.So, according to the mainstream model, a 10 meter expansion in one year between the earth and the sun does not happen due to gravitational binding forces.
The ruler won't expand even if the space it occupies is expanding because the forces holding together the ruler are much much stronger than expansion. Think of your ruler laying on a rubber sheet that is being stretched. The friction between the sheet and the ruler will be creating forces trying to stretch the ruler, but it's not going to actually stretch because the forces between the atoms of the ruler are much stronger. Same thing with cosmic expansion, it's only apparent when the forces holding things together are weaker than the expansion, such as gravity is over huge distances.(Note, if the expansion were to include the atoms making up the ruler, the ruler would also proportionally expand and there would be no measured 10 meter expansion in the distance between the earth and the sun over a one year period.)
Established Member
Hi tommac
You said,
I thought only non-gravitationally bound galaxies are effected?
I was a bit vague in my description of the mainstreams limited expansion model. I said,
The mainstream model describing the expansion of spacetime is a limited expansion model in that the expansion of spacetime is assumed to stop at the boundary of gravitationally bound galaxies.
What do I mean
One could ask, what is meant by a “gravitationally bound galaxies”? Is it the galaxy itself or is it something like a couple of galaxies attracted to each other?
The mainstream answer would be both, but a more complete answer should categorize three types of interaction.
A single galaxy
The self-gravitation of a galaxy to itself seems somewhat obvious.
A galaxy looks like a “closed” system. It requires a certain amount of dark matter in order to properly describe the observed orbital motions of the stars swirling around spiral galaxies.
Multiple galaxies
The gravitational binding of multiple galaxies to each other I would categorize as consisting of at least two types, groups and groups of groups called clusters. (or even super clusters interacting with super clusters)
(Ever increasing amounts of Dark Matter)
(I should note that according to these mainstream descriptions an ever increasing amount of dark matter is necessary as the scale of these extra galactic gravitationally bound structures increases).
Extra galactic interaction and general relativity
The last extra-galactic gravitational interaction of galaxies is based our understanding of general relativity and gravity.
Two galaxies can only interact to each other if they have had time to interact, that is to say if two galaxies are separated by 5 billion light years in a 3 billion year old universe, these two galaxies would not have had an opportunity to gravitationally bind to each other. In essence any galaxy that can be seen from one “central” galaxy is gravitational bound to that “central’ galaxy, in a cosmic sense.
This self-binding gravitational interaction of galaxies slows the rate of expansion. In fact, based on the observed current rate of expansion, and the “simplest” version of general relativity, it is possible to determine the age of the universe. This age should be 2/3 1/Ho. Which should be about 9 billion years old.
This is too young of an age of the Universe for the current mainstream model to conform to observation, and a number of “corrections” to the model have been added to allow the current “limited expansion model” to work. These corrections include adding just the right amount of dark matter and dark energy at the proper times in varying amounts.
Snowflake
Established Member
Hi phunk
If you believe that the space within the atom is increasing, (which is a very logical and reasonable assertion, reflective of an intelligent person), then you are advocating an ATM theory, not a mainstream theory.
I am an advocate of such a model, and I have posted works in the ATM section describing the mathematics of an expanding metric. If you wish to review my work in the ATM forum, do a search within the BAUT forum with the search name “snowflakeuniverse”.
Snowflake
Established Member
Hi phunk
I reread you post, perhaps you should re read mine. The mainstream model a "limited expansion model" which you admint to at the end of your posting. So your agree with my discription of the mainstream model. You just don't like perhaps my choice of words describing it as a limited expansion model.
Snowflake
Order of Kilopi
Yes thus ... non expansion ...
Order of Kilopi
But how close were they 3 billion years ago?
Established Member
Hi Tommac
You asked
But how close were they 3 billion years ago?
The mainstream answer would be 0 separation. That is to say, if one considered a 3 billion year old universe and was asked the separation distance between galaxies when the age of the Universe was 0, the separation distance would be 0.
Your are bringing out a good point, in that what does that mean for the galaxies that will turn out to be separated 5 billion light years in a 3 billion year old universe? The answer to the separation distance would again be 0.
The mainstream has not completely resolved the formation or distribution of galaxies from a “singularity” , but the proposed solution is the creation of inflation theory. This is purported to allow quantum variations to be stretched out so large that it creates the separation between galaxies.
As of yet there is no successful theory that matches this explanation. For example, if the beginning of the universe is intensely hot, everything would be thoroughly mixed up, no form or structure could exist. How could galaxies form in such chaos?. Why are aren’t there galaxies 1000 times the mass of our galaxy? Etc, etc.
Snowflake
Established Member
From Misconceptions about the Big-Bang
In fact, in our universe the expansion is accelerating, and that exerts a gentle outward force on bodies. Consequently, bound objects are slightly larger than they would be in a non accelerating universe, because the equilibrium among forces is reached at a slightly larger size. At Earth’s surface, the outward acceleration away from the planet’s center equals a tiny fraction (10–30) of the normal inward gravitational acceleration. If this acceleration is constant, it does not make Earth expand; rather the planet simply settles into a static equilibrium size slightly larger than the size it would have attained.
Established Member
Hi speedfreak
It would be better to state that it is believed the universe is accelerating, rather than it is accelerating.
Dark Energy fix
Dark Energy is added as a fix to the standard model to account for the unexpected dimming of type 1a supernovas (1asn’s) when correlated to their observed red shift and the expected deceleration of the expansion due to gravitational interaction between galaxies.
Fact or most popular guess
While the accelerating universe is a mainstream belief, I do not belief any astronomer would stake their life on this as being a fact. While the local outward acceleration is reputed to be small, the magnitude of this fix is actually mind-boggling. In order to move all the galaxies in the entire universe to the assumed observed distances (based on observed luminosities), most of the universe would have to be composed of dark energy. E = mcc, so if this energy were converted into mass, it would be greater than all the observed stars in all the observed galaxies in the universe, We do not know where this energy is coming from nor why. Such a proposal should really be recognized and reported as a speculative model.
Snowflake
Established Member
What speedfreak posted is exactly what I was getting at in my earlier post. Expansion is not limited to galaxy clusters and larger, space is expanding everywhere, it's just not noticeable at small scales because objects are bound to each other, not the the space they occupy. The space you occupy is free to 'slide out from under you' without carrying you along for the ride when there are other forces holding you in place. That doesn't mean space stops expanding at the small scale, it means your ruler, or earth, or the solar system, etc, aren't expanding because other things hold them together.
Order of Kilopi
I am also trying to make a point that in the past they WERE gravitationally bound. and if gravitational waves can not move faster than the speed of light ... then shouldnt they still be gravitationally bound as the changes in the gravitational field could not yet be felt?
Order of Kilopi
Do object expand along with space?
Order of Kilopi
But that would be incorrect. It is a necessary conclusion based on observations and logical inference. It is always true that some step in the scientific process of reaching a conclusion could be misguided, which might alter the conclusion, but all of the steps in this case have been analyzed very carefully, and no problem has yet been found.
Everyone is entitled to his own opinion, but not his own facts.
Order of Kilopi
Objects are held together by the EM force (not to mention the strong nuclear force). I am guessing at the magnitude, but the EM force is about 1060 times stronger than the 'force' of expansion. I believe this information should allow you to answer this question yourself.
Everyone is entitled to his own opinion, but not his own facts.
Order of Kilopi
Gad, tommac, speedfreek already gave you the answer to that one.
Solid objects do not expand along with space. Any acceleration or deceleration in the rate of expansion results in a slight force, which in this epoch is trivial in comparison to electromagnetic binding energies.
Grant Hutchison
Established Member
expansion of spacetime
Hi Top Ranking,
Taking up Snowflakes scenario on what happens to atoms in an
expanding universe, may I offer an alternative. In a vacuum with no atoms,
would spacetime still be expanding? I propose this concept based on above and
below posts that involve gravity. If space time expansion is greater in a weak or
null gravity, it would beg the question of what is driving it.
Could it be that gravity as we know it has a negative side, that acts in opposition
to any mass?
Nokton
Established Member
Objects and spacetime
The expansion of objects in space is more to do with time and the
observer. Indeed, is ruled by the position of the observer in the observers
current spacetime. As Albert said, everything is relative.
Nokton.
Newbie
The Mainstream is wrong and it knows its wrong but it cannot take the highly embarasing step of saying so. The ludicrous inclusion of Dark Matter, Dark Energy and Expansion all attest to a dying theory clutching at straws. A Theory should be predicting observations not requiring fudges to bolster the Theory.
And they even got the Pope to endorse the Big Bang Theory as it looks an awful lot like the Genesis account of creation! Well the Papacy has got it wrong before!
No, the Universe is infinite in time and space. The Red Shift is a natural phenomenon due to distance not speed.
oh, and the Higgs Boson will not be found!
Administrator
fivish,
First, welcome to BAUT.
Second, I very strongly urge you to read our rules for this board. Among our rules is the rule that Q&A is only for mainstream answers to things. If you wish to advocate a non-mainstream position you may only do so in the ATM (Against-The-Mainstream) section, and that section has its own set of rules.
We also have a rule against religious discussions; please leave out such references too.
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