A few Qs i have about of The Big-Bang Theory formulated by Georges Lemaître.

[Thermal]

Thermal, you assumed that if one observes recession in all directions, one must be at or near ground zero of the recessive phenomenon. I gave you an example of a simple geometry that falsifies that assumption. It's also an easy way for laymen to visualize the kind of thing cosmological physicists are talking about. And cosmological physicists have been quite clear that they are talking about a ((much) more complicated) version of that same kind of geometry.

So what's your complaint?

The same one I mentioned, not that it's a complaint. The example you gave doesn't address the image I'm seeing. You could just as well have drawn a couple dots on a rubber band and stretched it, saying "see? They move away from each other! QED!"

You don't understand the simple visualization?

Like a rubber band, very very easy to understand.

You don't like the simple visualization?

It's quite lovely. Just doesn't relate to the visual image.

You think cosmological physicists must be wrong about the geometry they're describing?

Now you're just being ridiculous. I don't know enough about the subject to even begin to question their conclusions. What I am saying is that analogizing an expanding single plane is evading the question in favor of a simpler one.

You're just playing silly buggers? You think you gave some substantive point not covered by the possibilities I've listed?

I've brought this up before: dark matter and energy. It is popularly described as having been "predicted". But it wasn't predicted. The math just produced wrong answers (or made predictions that turned out to be 180 degrees wrong or however you want to say it). Then I saw a Ted Talk or something once where a physicist said "the math failed, so we could do one of two things: throw out everything we knew, or stick a pin in this phenomenon and keep swinging till we could explain it".

Now to my ear, that is a very satisfying description. Tons better than the bull **** pseudo-mystical explanation about predictions. If you want to call that "playing silly buggers", Vaya con dios. The point I am making is that somewhere out there, there is likely a description that will click for a pragmatic layperson. A stretched rubber band is not it.

 

[sphenisc]

The same one I mentioned, not that it's a complaint. The example you gave doesn't address the image I'm seeing. You could just as well have drawn a couple dots on a rubber band and stretched it, saying "see? They move away from each other! QED!"



Like a rubber band, very very easy to understand.



It's quite lovely. Just doesn't relate to the visual image.



Now you're just being ridiculous. I don't know enough about the subject to even begin to question their conclusions. What I am saying is that analogizing an expanding single plane is evading the question in favor of a simpler one.



I've brought this up before: dark matter and energy. It is popularly described as having been "predicted". But it wasn't predicted. The math just produced wrong answers (or made predictions that turned out to be 180 degrees wrong or however you want to say it). Then I saw a Ted Talk or something once where a physicist said "the math failed, so we could do one of two things: throw out everything we knew, or stick a pin in this phenomenon and keep swinging till we could explain it".

Now to my ear, that is a very satisfying description. Tons better than the bull **** pseudo-mystical explanation about predictions. If you want to call that "playing silly buggers", Vaya con dios. The point I am making is that somewhere out there, there is likely a description that will click for a pragmatic layperson. A stretched rubber band is not it.

The rubber band is a one-dimensional analogue, the surface of a balloon is a two-dimensional analogue, baking bread is a three-dimensional analogue. As a pragmatic layperson I can understand that they each represent types of expansion, and things placed in/on each one will be carried along by the expansion of the underlying medium. I can also understand than the increase in separation between the things will be approximately proportional to their initial separation.

Where do you have a problem?

 

[Roger Ramjets]

This very diminutive size object that exploded out really was composed in their whole of all the chemical elements that do exist in our universe and in such inmense quantities? Have you a theory about of this particular phenomenom?

I don't have any theories, but I suspect the 'Big Bang' theory will have to be modified in the future as we gather more information. I would suggest waiting a few years to see where it goes.

Apart from that, why obsess over it when there are so many other more interesting and relevant things to learn?

 

[Thermal]

The rubber band is a one-dimensional analogue, the surface of a balloon is a two-dimensional analogue, baking bread is a three-dimensional analogue. As a pragmatic layperson I can understand that they each represent types of expansion, and things placed in/on each one will be carried along by the expansion of the underlying medium. I can also understand than the increase in separation between the things will be approximately proportional to their initial separation.

Where do you have a problem?

I was reading an ESA article about redshift and expansion, where it was said:

Two objects can actually be stationary in space and still experience a red shift if the intervening space itself is expanding.

...and this sent me off on a tangent. If the objects are stationary in space, but the space is expanding, that would mean the subjective referential measurement between the objects would remain the same and they would detect no difference in motion, but they still experience redshift as if they were moving apart? So from our vantage point, nothing is moving, but we infer that we must be moving because of the redshift? Do we have an explanation for why light waves are acting independently from the universal expansion? It would seem to follow that if space itself was expanding, the light would too, and redshift be morphing along with it. The raisins in the proverbial rising bread wouldn't perceive themselves in any way as being stationary to each other.

Getting back to my initial hitch, we do detect blueshift in some galaxies. If everything was universally expanding, as with our intrepid balloon, we shouldn't see this at all. And that's where I start getting cranky. But nevermind. I'll chase it around a bit more.

ETA: was reading another article about the hundred or so observed blueshifting galaxies. It is attributed to gravity of larger galaxies pulling them closer together, apparently altering their courses (somewhat radically?) from the force of the expanding universe.

 

[hecd2]

I was reading an ESA article about redshift and expansion, where it was said:



...and this sent me off on a tangent. If the objects are stationary in space, but the space is expanding, that would mean the subjective referential measurement between the objects would remain the same and they would detect no difference in motion, but they would experience redshift as if they were moving apart? So from our vantage point, nothing is moving, but we infer that we must be moving because of the redshift? Do we have an explanation for why light waves are acting independently from the universal expansion? It would seem to follow that if space itself was expanding, the light would too, and redshift be morphing along with it. The raisins in the proverbial rising bread wouldn't perceive themselves in any way as being stationary to each other.

Getting back to my initial hitch, we do detect blueshift in some galaxies. If everything was universally expanding, as with our intrepid balloon, we shouldn't see this at all. And that's where I start getting cranky. But nevermind. I'll chase it around a bit more.

You can get redshift and blue shift from the motions of galaxies with respect to the Hubble flow - this is known as relativistic Doppler redshift.

Overlaying Doppler shift is cosmological redshift caused by the universal (throughout the universe) expansion of space. For nearby galaxies, their local velocities can be such that the Doppler blueshift exceeds the cosmological redshift and then we observe blueshift. But taking a large number of galaxies into account, we can disentangle the local motion from the space expansion and determine the rate of space expansion as being in the order of 70km per second per megaparsec - this is the Hubble flow.

 

[W.D.Clinger]

(hecd2 has already responded, but having written this independently of that response I'll go ahead and post it.)

...and this sent me off on a tangent. If the objects are stationary in space, but the space is expanding, that would mean the subjective referential measurement between the objects would remain the same and they would detect no difference in motion, but they would experience redshift as if they were moving apart?

No. They are stationary in space, but the objectively measurable distance between them is increasing.

The "subjective referential measurement" between the objects increases because the objectively measurable distance increases.

Getting back to my initial hitch, we do detect blueshift in some galaxies. If everything was universally expanding, as with our intrepid balloon, we shouldn't see this at all.

Because space is expanding everywhere, the distance between us and faraway galaxies is increasing faster than the distance between us and nearby galaxies. That's why Hubble's constant (and the Hubble parameter more generally) is commonly expressed as kilometers per second (the rate at which that distance is increasing with time) per megaparsec (which says the rate at which the distance is increasing with time is itself proportional to the number of parsecs between the objects whose separation we're discussing).

We see blueshift in some relatively nearby galaxies because galaxies move a little bit with respect to each other. For nearby galaxies that are moving toward us, that motion can easily overwhelm the effect of expanding space, because (see above paragraph) the expansion of space affects the distance to nearby galaxies less than it affects the distance to faraway galaxies.

 

[Thermal]

(hecd2 has already responded, but having written this independently of that response I'll go ahead and post it.)


No. They are stationary in space, but the objectively measurable distance between them is increasing.

The "subjective referential measurement" between the objects increases because the objectively measurable distance increases.

This may be where I'm losing the plot. It's my understanding that if space itself is expanding (as opposed to simply the outer boundaries of it expanding), them matter within it would also be expanding along with it, resulting in no subjective detectable difference. The universal expansion would only be tracked by a reference frame outside of the expanding space.

Because space is expanding everywhere, the distance between us and faraway galaxies is increasing faster than the distance between us and nearby galaxies. That's why Hubble's constant (and the Hubble parameter more generally) is commonly expressed as kilometers per second (the rate at which that distance is increasing with time) per megaparsec (which says the rate at which the distance is increasing with time is itself proportional to the number of parsecs between the objects whose separation we're discussing).

We see blueshift in some relatively nearby galaxies because galaxies move a little bit with respect to each other. For nearby galaxies that are moving toward us, that motion can easily overwhelm the effect of expanding space, because (see above paragraph) the expansion of space affects the distance to nearby galaxies less than it affects the distance to faraway galaxies.

Thanks for that, but I feel that alcohol may have done it's evil work to my memory and I've simply forgotten so much of the basics that I need to play a rather long catch-up on my own.

 

[Darat]

This may be where I'm losing the plot. It's my understanding that if space itself is expanding (as opposed to simply the outer boundaries of it expanding), them matter within it would also be expanding along with it, resulting in no subjective detectable difference. The universal expansion would only be tracked by a reference frame outside of the expanding space.




Thanks for that, but I feel that alcohol may have done it's evil work to my memory and I've simply forgotten so much of the basics that I need to play a rather long catch-up on my own.

That is I think your misconception. Matter is held together with forces that aren't being stretched if you like. Think of it like a chair in a room - you can make the room bigger - that's the expansion but the chair doesn't scale with the room that stays the same size.

 

[W.D.Clinger]

ETA: Ninja'd by Darat.

This may be where I'm losing the plot. It's my understanding that if space itself is expanding (as opposed to simply the outer boundaries of it expanding), them matter within it would also be expanding along with it, resulting in no subjective detectable difference.

It's reasonable to think that, but there are two reasons why compact objects don't expand even though they lie within expanding space.

• The size of atomic particles is fixed by the laws of atomic physics, so atoms don't expand. Similarly, molecules don't expand because their size is determined by things like binding energy, which aren't affected by expanding space. And so on up until you get to objects that are mostly held together by gravity instead of the stronger forces such as electromagnetism and nuclear forces.
  
  
• Objects that are held together by gravity might expand due to expanding space, but that will happen only if the effect of expanding space overcomes the gravitational forces holding them together. For compact objects such as planets, stars, and (most) galaxies, the gravitational forces that hold them together are strong enough to keep holding them together despite the small effects of expanding space. (Recall that the effect of expanding space is proportional to distance. That means the effect of expanding space is very small for compact objects.)

 

[Thermal]

That is I think your misconception. Matter is held together with forces that aren't being stretched if you like. Think of it like a chair in a room - you can make the room bigger - that's the expansion but the chair doesn't scale with the room that stays the same size.

That is why I keep stalling there. It seems to follow that if the universe is expanding at 160,000 mph, the walls around my chair should be flying away at about that rate. But since they don't, I assume that matter and the space between particles is chugging right along with it.

Then again, universal expansion at the rate of 160,00 mph is like crazy slow on the astronomical scale:

It's much more useful to quantify the expansion velocity of the Universe as a relative growth rate. It turns out that space is expanding pretty slowly: at present, cosmic distances increase by just 0.007% in one million years.

Kind of surprising we would be detecting redshift in such a slow rate, but I suppose that speaks to the astounding precision of the state of scientific observation.

 

[theprestige]

That is why I keep stalling there. It seems to follow that if the universe is expanding at 160,000 mph, the walls around my chair should be flying away at about that rate. But since they don't, I assume that matter and the space between particles is chugging right along with it.

Then again, universal expansion at the rate of 160,00 mph is like crazy slow on the astronomical scale:



Kind of surprising we would be detecting redshift in such a slow rate, but I suppose that speaks to the astounding precision of the state of scientific observation.

Over short distances, gravity and other forces are strong enough to hold stuff together. At least at the current rate of expansion. If the rate of expansion keeps accelerating, eventually it will override gravity at galactic scales, and the galaxies will start dispersing.

If the rate of expansion keeps accelerating after that, eventually it will start to override mechanical, molecular, and even atomic bonds.

 

[hecd2]

Kind of surprising we would be detecting redshift in such a slow rate, but I suppose that speaks to the astounding precision of the state of scientific observation.

It speaks rather to the extremely long time the expansion has been going on to the extent where we detect that the universe has expanded by a factor of ~1000 since the cosmic microwave background was emitted more than 13 billion years ago (that’s 13000 million years). It’s easy to detect the redshift.

 

[catsmate]

Gravity. Gravity will crush any sufficiently large object into a sphere. Small objects do not have enough gravity to crush themselves into spheres.



Are you asking why we don't see planet-sized objects floating around in interstellar space, but only around stars?
Well, the simplest reason is that they would be too dim. Stars are easy to see because they give off light. Planets outside our solar system are very hard to see because they only reflect the light of stars. Nearby planets are similar in brightness to stars even though they are much, much closer. It's actually extremely hard to see planets around other stars, and we have only been able to do that very recently. Even most planets around other stars we don't observe directly, but by their shadow as they pass in front of their star. A planet in interstellar space would receive very little light to begin with, and we would receive almost none of it. They would blend into the blackness of space.

The few studies into FFPs indicate they are probably extremely common, more so than stars, perhaps by several orders of magnitude. They are, as you say, damn difficult to find however.

 

[Lothian]

I am not a scientist but I know the answer, in layman's terms, to some of the above. I wonder why the op doesn't as they appear to have an interest and have clearly done some research. Hopefully they will take on board the answers and go away d look into it more. It will be very disappointing if they come back and simply proclaim Goddidit.

 

[Wudang]

That is why I keep stalling there. It seems to follow that if the universe is expanding at 160,000 mph, the walls around my chair should be flying away at about that rate. But since they don't, I assume that matter and the space between particles is chugging right along with it.

Matter distorts space. You heard the analogy about gravity being like weights on a rubber sheet and the dips formed represent the gravitational pull?
Going back to the balloon analogy, matter makes the balloon thicker in parts so it doesn't stretch the same way as thinner parts.
Not a physicist.

 

[arthwollipot]

Going back to the balloon analogy, matter makes the balloon thicker in parts so it doesn't stretch the same way as thinner parts.
Not a physicist.

That's a good analogy from what I understand about it. Also not a physicist.

 

[HansMustermann]

1.- If the whole floating objects (moons, planets, suns or stars, galaxies, small asteroids, comets, etc.) were at the first time an integral part of a kind of a very diminutive size object, how can be possible that (after of "the mega-explosion" of this very diminutive size object) all their expulsed thrown parts of it have been shifted to so gigantic floating objects in the outer space before of to be so "microscopical"? Have you a theory about of this particular phenomenom?

Just as a small addendum, we do not know if the whole universe was all in the same dot. Just the parts that we can still see. If the universe is flat (as in, not curved like a giant balloon) the only explanation would be that it was always infinite, just a lot more compressed.

As for how the rest happened, that's better combined with your question 2.

2.- This very diminutive size object that exploded out really was composed in their whole of all the chemical elements that do exist in our universe and in such inmense quantities? Have you a theory about of this particular phenomenom?

No. It expanded too fast to produce almost anything other than hydrogen and helium. Well, also some insignificant traces of lithium, but that was about it. Not even enough lithium for the first stars to have the metallicity to properly ignite fusion like later generations.

The first stars in fact may have been giant quasi-stars that didn't have a fusing core to provide the energy to balance them (and were too gigantic to be supported by that kind of radiation pressure) but had a black hole as a core. Then eventually those blew up, and their remains then formed the first galaxies. Then that matter clumped up and gravity (and friction) made it accrete into stars and planets, then those stars exploded and so on.

Elements up to iron can be formed by fusion in stars. Past iron, it takes energy to fuse, rather than produce anything, so any star that is massive enough to exhaust anything else and start fusing iron, only does so very briefly and it makes it collapse.

Above iron, it's produced in the massive explosions of supernovas.

3.- If the force of the explotion of this very diminutive size object was so strong, how is possible that this particular force (force which still until today as strongest as it was since the moment of this explosion), so, how can be possible that this so powerful force is the weak enough for to thrown away (just in the same direction or way than takes the planets, suns or stars, galaxies, etc.) all the most smallest floating objects of our universe as are the moons, small planets, asteroids, comets, etc)? What i am refering in this Q is about why and how is possible that in the paticular circunstances of this mega-explotion do exist the orbits of the floating objects that firstly must be thrown away by this force without any minimal chance of to return repeatedly just in the same contrary direction of the direction that takes this mega-explotion almost without to be really affected by this force? Have you a theory about of this particular phenomenom?

Think of it less as a force, and more like space itself expanding in all directions, to understand that one. The important difference being that a force is strongest up close, and weak at a distance, whereas space expands by a percent, so it's a truly insignificant speed small scales, but big at a billion light years distance. It's kinda like compound interest on a bank account.

And the difference then becomes how strong some systems are bound by gravity, to be kept together in spite of the space trying to pull them apart. Like, basically sure, space expansion may try to move the moon by a nanometre, but gravity says "oh no, you don't" and keeps it in place.

4.- Why all the bigger floating objects of this universe have particularly a spherical shape while the smallest floating objects (as are the comets, asteroids, meteorits, a some moons, etc.) have particularly very asymmetrical shapes? All the millions of years passed since the mega-explotion do not was the enough time for to shape them too in a some spherical-like shape? Have you a theory about of this particular phenomenom?

The difference is gravity, and more specifically the pressure it creates. Very small moons have barely enough gravity to keep themselves together. Larger ones have enough gravity to limit the relative size of bumps. Like, if Earth had a clump thrice the size of Everest, it would just get squished by its own weight.

5.- How can be possible the formation of solar systems, constellations and galaxies if the monumental force of this mega-explotion is supposed that is so strongest that "in theory" none of the floating objects could have "the time" for to end "hooked" to a "vulgar" and "ordinary" orbit? Really the gravity force of the solar systems, constellations and galaxies is much more strongest than the mega-explotion which "do form" this universe avoiding so the chaotic destiny of floating objects that do not have none orbit at all? Have you a theory about of this particular phenomenom?

For the same reason mentioned before. Other than during the actual big bang, space expands by a very small percentage each year. This is a big change for stuff very far away, but very very small at the sizes where those accretion disks happen. Gravity is BY FAR the dominant force at solar system scales. (And in turn electromagnetism is by far stronger than gravity at atom scales.)

6.- Why our modern telescopes still without to find floating spherical objects (like moons & planets) that are floating just alone in the outher space and without to have at all an orbit around of another floating body? Really all and each of the moons & planets that do exist in our universe actually are not alone and actually have an orbit for to follow or are outhere moons & planets without any orbit at all --because The Big-Bang Theory points to this chaotic view--. Have you a theory about of this particular phenomenom?

Planets form in accretion disks during the formation of stars.

That said, it is thought that rogue planets (without a star) do exist, but really our telescopes are too weak to actually see planets at all past very short ranges. Most exoplanets we've detected so far are really indirect observations, rather than see the planet itself. E.g., we see that a star slightly dims periodically and deduce than a planet keeps going in front of it periodically.

Plus a rogue planet would be very hard to detect anyway, because it doesn't have a star shining light on it. It would be something whose surface is the temperature of frozen nitrogen, so it doesn't emit much energy itself. (Cf Stefan–Boltzmann.) For all intents and purposes it is very very dark in any wavelength, against an equally dark background. It's basically like looking for a black cat on a moonless night, from 5km away.