How are galaxies expanding along with space time?

[Markus Hanke]

1 minute ago, Quantum321 said:

If you measure their rated of expansion from earth how can the accelerator read zero?

Because there is a difference between what we visually observe from a distance, and what actually happens locally where the galaxy is. The first is called coordinate acceleration, the latter is called proper acceleration. The difference between these is crucial.

To see why, turn things on their head - from the perspective of a very far away galaxy, our own galaxy where Earth is located is moving away at a very high and accelerating rate. Yet if you stand up right now and look at an accelerometer, you won’t actually detect any massive acceleration acting on you (hence on the Earth, and our galaxy). There is coordinate acceleration (what you measure from a distance), but no proper acceleration (what an accelerometer physically measures). The same is true for forces of course.

[Quantum321]

Yes. the dots are attached to the rubber of the balloon. As the rubber stretches due to the balloon being inflated the dots are carried along because they are fixed to the surface. The galaxies are not fixed to space.

[koti]

40 minutes ago, Markus Hanke said:

Again, you need to remember that space is not any kind of mechanical medium, and that there is no motion involved, in the sense that no forces act on anything. If you were to attach an accelerometer to any of these galaxies, it would read exactly zero at all times, so there is no acceleration and hence no forces that act on anything. All that happens is that the distance between galaxies increases, because space there expands - so there is relative/apparent motion due to the increase in distances, but no local motion that involves forces or the transfer of energy. It’s purely a geometric phenomenon.

Nice easily digestable explanation of expansion +1.

[Markus Hanke]

11 minutes ago, Quantum321 said:

Yes I have also heard to raisins in the bread analogy. But that's not the same as galaxies and space.

No - but it’s a reasonably good analogy to demonstrate the basic principle. Where the analogy fails though is that metric expansion has nothing to do with any “stretching”. That’s why it’s just an analogy.

Edited June 21, 2018 by Markus Hanke

[Quantum321]

Just now, Markus Hanke said:

No - but it’s a reasonably good analogy to demonstrate the basic principle.

I don't see how its applicable. The raisins are carried along with the expanding bread due to atoms pushing against atoms

[Markus Hanke]

Just now, Quantum321 said:

I don't see how its applicable. The raisins are carried along with the expanding bread due to atoms pushing against atoms

It’s useful so long as you bear in mind the difference between “analogy” and “model” - they have different aims and goals.

[studiot]

5 minutes ago, Quantum321 said:

Yes. the dots are attached to the rubber of the balloon. As the rubber stretches due to the balloon being inflated the dots are carried along because they are fixed to the surface. The galaxies are not fixed to space.

I didn't use the word space.

But the balloon skin is the analogy or model for space in this case.

And yes the galaxies experience interactive forces just as the molecules of the skin does, but that is outside the analogy.

[koti]

9 minutes ago, Quantum321 said:

I don't see how its applicable. The raisins are carried along with the expanding bread due to atoms pushing against atoms

Thats why it is only an analogy. To have a clear view of how it really works think of what Markus wrote - the galaxies do not experience local motion due to expansion, everything gets away from each other because space around everything gets bigger. Any reference frame in our universe experiences that expansion regardless of its velocity or position. You also need to understand that gravitational waves have nothing to do with strong and weak interaction nor electromagnetism, they are all separate phenomena. 

Edited June 21, 2018 by koti

[Quantum321]

Wait a minute. The Hubble constant says that for every parsec the galaxy increases in speed by 72 kilometers per hour. An accelerameter won't register anything? Doesn't make sense to me.

 

[koti]

9 minutes ago, Quantum321 said:

Wait a minute. The Hubble constant says that for every parsec the galaxy increases in speed by 72 kilometers per hour. An accelerameter won't register anything? Doesn't make sense to me.

 

Yes, you need to read Marcuses posts again and wrap your head around it.

Think about the bread and raisins again.

[Markus Hanke]

17 minutes ago, Quantum321 said:

An accelerameter won't register anything? Doesn't make sense to me.

It doesn’t need to “make sense” (a purely subjective perception!), it just needs to fulfil the requirements of a scientific model. Which the laws of gravity demonstrably do very well.

The situation is the exact same as when you jump off a board into a swimming pool - a stationary bystander can measure your motion from afar, and will argue that you undergo acceleration, based on what he measures (9.81m/s2). But if you yourself carry an accelerometer with you as you jump off, you will find that it reads exactly zero at all times during your free fall.

This is not just some theoretical speculation, but something you can actually try out yourself. In fact, I would encourage you to go ahead and do this experiment, if you are really in doubt over the differences between coordinate and proper measurements. Just make sure your accelerometer is waterproof  Alternatively, you can just recognise that this funny feeling you get in your tummy while you are in free fall is just precisely this - the absence of any acceleration (i.e. force) acting on you. And yet you fall under the influence of gravity.

Edited June 21, 2018 by Markus Hanke

[studiot]

17 minutes ago, Quantum321 said:

Wait a minute. The Hubble constant says that for every parsec the galaxy increases in speed by 72 kilometers per hour. An accelerameter won't register anything? Doesn't make sense to me.

 

 

Actually the dimensions of the hubble constant are  LT^-1L^-1 = T^-1 or the reciprocal of time or a frequency.

[koti]

5 minutes ago, Markus Hanke said:

...Alternatively, you can just recognise that this funny feeling you get in your tummy while you are in free fall is just precisely this - the absence of any acceleration (i.e. force) acting on you. And yet you fall under the influence of gravity.

I love that feeling when going fast over a hill in a car.

[Endy0816]

48 minutes ago, Quantum321 said:

I hear you. Look at the Hubble constant. By definition galaxies are move away at an increasing rate based on parsec's of distance. "Moving away at an increasing rate" If you measure their rated of expansion from earth how can the accelerator read zero?

Yes I have also heard to raisins in the bread analogy. But that's not the same as galaxies and space.

Every 6 hours a 10 man road crew doubles the distance of a 1,100 mile road between Orlando and New York.

What is Orlando's acceleration?

[koti]

7 minutes ago, Endy0816 said:

Every 6 hours a 10 man road crew doubles the distance of a 1,100 mile road between Orlando and New York.

What is Orlando's acceleration?

Hmm, I think this might bring even more confusion to the OP as this complicates things. Universe expansion is there for any frame of reference. There are a lot of frames of reference in relation to which Orlando accelerates. 

Edited June 21, 2018 by koti

[Endy0816]

17 minutes ago, koti said:

Hmm, I think this might bring even more confusion to the OP as this complicates things. Universe expansion is there for any frame of reference. There are a lot of frames of reference in relation to which Orlando accelerates. 

In relation to NYC then.

[Markus Hanke]

34 minutes ago, koti said:

I love that feeling when going fast over a hill in a car.

...until you meet you meet a 10t cement truck head-on at the other side of the crest. All of a sudden acceleration becomes very real again  

27 minutes ago, Endy0816 said:

Every 6 hours a 10 man road crew doubles the distance of a 1,100 mile road between Orlando and New York.

What is Orlando's acceleration?

Lol, I like this

[Mordred]

Ok lets try this angle. expansion or contraction of our observable universe involves the distribution of matter, radiation and the cosmological constant. It is in essence a thermodynamic process involving these three factors. Each of these contributors has an equation of state that relates the pressure vs the contributors kinetic energy with the contributors density. For example matter has a low kinetic energy term so its pressure contribution is zero. These contributors evolve over time in that the average density decreases as the volume increases, except for the cosmological constant.

Heuristically one can think of pressure as performing the work for expansion however this isn't precisely accurate. However expansion requires no new forces to cause expansion the equations of state for the three categories mentioned determine the contributors to the FRW fluid equation.

Here is the equations of state.

https://en.wikipedia.org/wiki/Equation_of_state_(cosmology)

notice the term [latex] w=\frac{P}{\rho}[/latex] this shows the correlation between the mean density and the pressure relations. Now why do we say space between galaxies expand rather than galaxies are moving. This is a consequence of the Cosmological principle. The universe mass density is a homogeneous and isotropic distribution as well as expansion is a homogeneous and isotropic process. The distribution and dynamics has no preferred direction nor a centre or location. Combined this expresses a uniform distribution.

 Now in order for inertia change to occur ie acceleration force must be applied. However the distribution around galaxies is uniform, so the force due to pressure surrounding galaxies are also uniform. There is no net force in any direction as the pressure is uniform surrounding the galaxies. Hence those galaxies gain no momentum due to expansion. Instead the volume between the galaxies expand without causing an inertia change to the galaxies themselves.

Here is a more complete explanation

http://www.astronomy.ohio-state.edu/~dhw/A5682/notes4.pdf

Edited June 21, 2018 by Mordred

[Eise]

2 minutes ago, Markus Hanke said:

...until you meet you meet a 10t cement truck head-on at the other side of the crest. All of a sudden acceleration becomes very real again  

I've lived one year long in Ireland. The risk there seems very real to me...

Markus, I would like to (mis)use this opportunity to thank you for your very clear postings everywhere on these fora, bringing in your deep expertise, and in name of some others, for your patience explaining the nearly impossible.

@Quantum321: I have two analogies.

The first is the balloon again. But look from this side: the balloon is inflating because of the pressure from the inside, so there is a force in the outward direction. But there is no force between the dots drawn on the surface. 

The second is two people on the north pole of the earth: say they walk to the south, but under a slight angle. Given  their experience that the earth is locally flat, they expect that their distance increase with time uniformly: if they have walked two kilometer, their distance will be twice as much as when they had walked for one kilometer. But to their astonishment, they measure that the distance between them increases less and less the farther they walk. So they conclude there is some force that tries to push them to each other. But we know there is no such force: it is a consequence of the curvature of the earth. (So in this example, their universe accelerates less and less. The curvature of the earth is positive, but if you imagine a negative curvature (the form of a saddle) they will get away from each other faster and faster, without any force.) Just imagine that the direction they are walking, is the time dimension.

[StringJunky]

2 hours ago, Quantum321 said:

I don't see how its applicable. The raisins are carried along with the expanding bread due to atoms pushing against atoms

In their own frame of motion, which is inertial, the individual raisins are not moving but every one around them is. It's an increase in the intervening space.

Edited June 21, 2018 by StringJunky

[Markus Hanke]

59 minutes ago, Eise said:

I've lived one year long in Ireland. The risk there seems very real to me...

Indeed - some of the roads are shocking here. I know this better than most, because I’ve been a full-time van-lifer for a while, so these roads are my home. A healthy dose of respect is needed.

1 hour ago, Eise said:

Markus, I would like to (mis)use this opportunity to thank you for your very clear postings everywhere on these fora, bringing in your deep expertise, and in name of some others, for your patience explaining the nearly impossible.

 

Thank you Oftentimes, explaining things to others is the best way to deepen your own understanding of it. The challenging bit is always to figure out whether the other party is actually receptive, or whether you are talking to a wall. 

[swansont]

4 hours ago, Quantum321 said:

Swansont. " No, it doesn't push the atoms. Space expands, and two objects would tend to get further apart since there is more space between them. But there is no push. " This is exactly my problem. What physical properties are involved in "two objects would tend to get further apart since there is more space between them" Why would they? What force makes them get farther apart?

No force is required to get things further apart. One situation is: If they are moving, they tend to keep moving. No force required.

But this is another situation. If we imagine a space with a bunch of tiles (e.g. the square made by grid lines on a graph). If you are on tile #1 and I am on tile #1001 and the some time later we see that there is an additional tile between us, we are further apart. And yet I have not moved on my tile, and you have not moved on yours. We are not moving locally, and have felt no force.

[Phi for All]

5 hours ago, Quantum321 said:

Koti. No gravity is not a separate force. Gravity wave A is the strong nuclear force and gravity wave b is the weak force. Scientists have know this for some time now but keep it under wraps.

!

Moderator Note

And now the thread is no longer asking questions about mainstream science, but is instead speculating outside it. Moved to Speculations, please read the special rules concerning this section, and support your ideas with evidence and critical thought.

 

[Endy0816]

2 hours ago, Markus Hanke said:

Lol, I like this

Thanks means alot from you.

 

 

[Quantum321]

6 hours ago, Markus Hanke said:

It doesn’t need to “make sense” (a purely subjective perception!), it just needs to fulfil the requirements of a scientific model. Which the laws of gravity demonstrably do very well.

The situation is the exact same as when you jump off a board into a swimming pool - a stationary bystander can measure your motion from afar, and will argue that you undergo acceleration, based on what he measures (9.81m/s2). But if you yourself carry an accelerometer with you as you jump off, you will find that it reads exactly zero at all times during your free fall.

This is not just some theoretical speculation, but something you can actually try out yourself. In fact, I would encourage you to go ahead and do this experiment, if you are really in doubt over the differences between coordinate and proper measurements. Just make sure your accelerometer is waterproof  Alternatively, you can just recognise that this funny feeling you get in your tummy while you are in free fall is just precisely this - the absence of any acceleration (i.e. force) acting on you. And yet you fall under the influence of gravity.

Next morning...Now that I think about it, of course you are right. Acclerometers measure forces like when an object suddenly stops but does not read during motion.

It's interesting that the only was we have of measuring the speed of a galaxy is the Doppler shift. Edwin Hubbles great contribution that changed everything.

Mordred. " Now in order for inertia change to occur ie acceleration force must be applied. However the distribution around galaxies is uniform, so the force due to pressure surrounding galaxies are also uniform. There is no net force in any direction as the pressure is uniform surrounding the galaxies. Hence those galaxies gain no momentum due to expansion. Instead the volume between the galaxies expand without causing an inertia change to the galaxies themselves."

If there is no net force in any direction (which I agree with) Then why are to galaxies moving with the expansion of space? With all the conventional examples given here there isn't one that accurately describes whats happening in space. Raisins move because atoms push against atoms. Dots on a balloon because  they are anchored to the fabric of the balloon. There is no friction in space.

Epiphany

I just had a thought. I have been thinking about this all wrong.  The initial conditions of the BB set everything in motion. Gravity caused dust particles to come together forming rocks and rocks formed planets etc. Everything was already in motion. Space is expanding for some reason no one understands but it does not affect the galaxies motion. And since there is nothing to slow the galaxies they continued to expand along with space. Now this makes sense to me. But wait.. this does not explain the Hubble constant. Why are galaxies accelerating?

2 hours ago, Phi for All said:

!

Moderator Note

And now the thread is no longer asking questions about mainstream science, but is instead speculating outside it. Moved to Speculations, please read the special rules concerning this section, and support your ideas with evidence and critical thought.

 

I was going to say now I know how Copernicus felt. But I don't want people to think I am special in any way. I respect as moderator your responsibilities regarding personal theories which are not accepted by mainstream science. Respectfully, what I said is mainstream science. I won't visit this topic again.

Now I don't understand...if the BB is in question because there does not appear to a center from which everything is expanding then whats going on?

Edited June 21, 2018 by Quantum321