New theory about how it all started

[Ophiolite]

So.. any substantive response to the dark energy point while we are here?

I have the good sense not to comment on matters I have not studied in depth. The only advantage of having people who do not follow this approach is that it keeps active hundreds of forums on many disciplines
, including CF. If, indeed,that is an advantage.

 

[FrumiousBandersnatch]

they all contribute to the observation that more distant objects appear to be receding more quickly-
not necessarily accelerating-

Accelerating if the change in velocity with distance is non-linear.

Don't worry I forgive you! argument from authority is one of the most common fallacies and we have all been guilty of it at some point. I am old enough to remember science teachers who still looked to Hoyle as an authority on the steady state nature of the universe..

You should update your understanding of common fallacies. It would be absurd if it was fallacious to prefer expert consensus over uninformed opinion.

The argument from authority fallacy generally concerns appeal to spurious authority (e.g. authority in an unrelated field) or, less often, appeal to fringe authority (e.g. an authority that does not represent expert consensus).

There are several alternate theories, my original point was just that the same general observation of objects receding at greater speeds at greater distances doesn't require a repulsive force- positive gravity can do the same

A repulsive force is the simplest explanation as, in the physics of GR, it just involves a positive cosmological constant, producing negative pressure vacuum energy which results in a repulsive gravitational field.

Can you explain what you mean by 'positive gravity' and how it would produce the acceleration effect?

 

[Guy Threepwood]

Accelerating if the change in velocity with distance is non-linear.

You could use doppler shift to measure several cars, with a non linear differential in velocity over distance. This still would not tell you any cars are accelerating, just that they are travelling more quickly at further distances

acceleration is change in velocity over time, not distance...

You should update your understanding of common fallacies. It would be absurd if it was fallacious to prefer expert consensus over uninformed opinion.

intuitively absurd yet curiously useful- when the overwhelming majority of cosmologists favored static/ steady state models, the average man on the street could have told you there was a beginning- 'wisdom of the masses' some call it

A repulsive force is the simplest explanation as, in the physics of GR, it just involves a positive cosmological constant, producing negative pressure vacuum energy which results in a repulsive gravitational field.

That's the mistake Einstein made, using the gap in his math to 'discover' a new constant

Can you explain what you mean by 'positive gravity' and how it would produce the acceleration effect?

There is no directly measured acceleration, just higher velocities at greater distances- positive/attractive gravity can, and would produce this same observation in itself- beginning with an initial collapse which is what the OP'er was speculating about

 

[FrumiousBandersnatch]

You could use doppler shift to measure several cars, with a non linear differential in velocity over distance. This still would not tell you any cars are accelerating, just that they are travelling more quickly at further distances

The point is to find the simplest explanation for the phenomenon. Galaxies are not automotive, distant ones typically have very small proper motion compared with their recession velocity. Accelerating expansion accounts for the red-shift observations and is supported by other measurements as previously described.

intuitively absurd yet curiously useful- when the overwhelming majority of cosmologists favored static/ steady state models, the average man on the street could have told you there was a beginning- 'wisdom of the masses' some call it

That would depend which street you chose. In Buddhism, Hinduism, & Jainism, time and the universe are eternal. Other religions have a variety of origin myths, but when the choice is between origin or no origin, it's no surprise that large numbers claim 'origin' without any empirical knowledge of the universe. Expressions of uninformed belief are not what is generally meant by the 'the wisdom of the crowd'.

That's the mistake Einstein made, using the gap in his math to 'discover' a new constant

He called it his 'biggest blunder' because he'd put it in to conform to a presumption of a static universe rather than evidence of such. Now we have evidence of accelerating expansion, it's a pragmatic candidate, but not the only one.

There is no directly measured acceleration, just higher velocities at greater distances

As previously explained, there are no directly measured velocities either, just higher red-shifts.

positive/attractive gravity can, and would produce this same observation in itself- beginning with an initial collapse which is what the OP'er was speculating about

Can you explain how a gravitational collapse produces the appearance of accelerating expansion (rather than, say, a black hole)?

 

[Guy Threepwood]

The point is to find the simplest explanation for the phenomenon.

like one that does not require an entirely theoretical new energy force like dark energy?

That would depend which street you chose. In Buddhism, Hinduism, & Jainism, time and the universe are eternal. Other religions have a variety of origin myths, but when the choice is between origin or no origin, it's no surprise that large numbers claim 'origin' without any empirical knowledge of the universe. Expressions of uninformed belief are not what is generally meant by the 'the wisdom of the crowd'.

And it depends on what we call an 'expert'

Roger Federer has won 20 Grand Slams- I think we can all agree he is an expert at the game of tennis, and I would certainly value his advice on it

Stephen Hawking was considered an expert on cosmology- he predicted a 'Big Crunch' that time would reverse and we would literally crawl back into the womb- before this was debunked by some of the observations we are discussing- also Hawking radiation, which I don't think anyone ever found yet

Having said that he overcame enormous adversity, sold millions of books, and entertained and inspired millions of people- I'd say that's where his demonstrable expertise lay

As previously explained, there are no directly measured velocities either, just higher red-shifts.

that's true yes, the red shift could be caused by something else also

Can you explain how a gravitational collapse produces the appearance of accelerating expansion (rather than, say, a black hole)?

For example- we were discussing the voyager probes/ interstellar space travel etc on another thread.

Voyager 1 is much further away than Voyager II and is also moving faster

Does this suggest it is moving faster because it is further away - being repelled by a mysterious force?
or that it is simply further away because it is moving faster?

what sort of mysterious force caused it to be receding from/ defying our system's gravity even more quickly than voyager II?

 

[FrumiousBandersnatch]

like one that does not require an entirely theoretical new energy force like dark energy?

An 'entirely new' force is not necessary - as mentioned, gravity can do the job. But there is no problem with introducing a new force if that is what best explains the observations; the currently known forces are relatively recently identified and formulated as such.

And it depends on what we call an 'expert'Roger Federer has won 20 Grand Slams- I think we can all agree he is an expert at the game of tennis, and I would certainly value his advice on it

Sure, but how is that relevant?

Stephen Hawking was considered an expert on cosmology- he predicted a 'Big Crunch' that time would reverse and we would literally crawl back into the womb- before this was debunked by some of the observations we are discussing- also Hawking radiation, which I don't think anyone ever found yet

Having said that he overcame enormous adversity, sold millions of books, and entertained and inspired millions of people- I'd say that's where his demonstrable expertise lay

He predicted a big crunch given certain assumptions, which turned out not to hold. Hawking radiation is not expected to be detected as its intensity inversely proportional to the size of the black hole, and it has a thermal signature. We couldn't detect it for a black hole large enough for us to see even if there was no other radiation from outside the event horizon - of which there is usually vast quantities. It's generally accepted because it's a prediction of quantum mechanics at the event horizon.

Hawking's demonstrable expertise was in theoretical physics and cosmology, although he was also a professor of mathematics.

... that's true yes, the red shift could be caused by something else also...

Quite; but a Doppler effect fits the data and satisfies common abductive criteria better than other suggested explanations, just as accelerating expansion fits the data and satisfies common abductive criteria better than other suggested explanations.

For example- we were discussing the voyager probes/ interstellar space travel etc on another thread.

Voyager 1 is much further away than Voyager II and is also moving faster

Does this suggest it is moving faster because it is further away - being repelled by a mysterious force? or that it is simply further away because it is moving faster?

what sort of mysterious force caused it to be receding from/ defying our system's gravity even more quickly than voyager II?

There's nothing mysterious about it. Voyager 1 had a different trajectory from Voyager II, so gained sufficient momentum from gravitational slingshots to overtake it. The expansion of space has no effect within gravitationally bound systems such as our galaxy.

None of that explains how a large amount of mass collapsing under its own gravity could give the appearance of accelerating expansion.

 

[Guy Threepwood]

Quite; but a Doppler effect fits the data and satisfies common abductive criteria better than other suggested explanations, just as accelerating expansion fits the data and satisfies common abductive criteria better than other suggested explanations.

the acceleration is based in turn on the redshift- assuming it is doppler- i.e. the acceleration is a farther speculation

There's nothing mysterious about it. Voyager 1 had a different trajectory from Voyager II, so gained sufficient momentum from gravitational slingshots to overtake it. The expansion of space has no effect within gravitationally bound systems such as our galaxy.

None of that explains how a large amount of mass collapsing under its own gravity could give the appearance of accelerating expansion.

So it used attractive gravity to repel itself away from gravity- with no additional repelling force required

 

[FrumiousBandersnatch]

the acceleration is based in turn on the redshift- assuming it is doppler- i.e. the acceleration is a farther speculation

It's not speculative because it's been tested by other observations (previously mentioned) which are consistent with that explanation.

So it used attractive gravity to repel itself away from gravity- with no additional repelling force required

I know. But how does that explain how a large collection of mass collapsing under its own gravity gives the appearance of accelerating expansion?

If you don't know, just say so.

 

[Guy Threepwood]

It's not speculative because it's been tested by other observations (previously mentioned) which are consistent with that explanation.

again the other observations may be interpreted to support the same observation- that more distant objects are receding more quickly, not that they are actually accelerating.

I know. But how does that explain how a large collection of mass collapsing under its own gravity gives the appearance of accelerating expansion?

If you don't know, just say so.

Voyager and Saturn essentially 'collapsed' towards each other, contributing to their own separation velocity

 

[FrumiousBandersnatch]

again the other observations may be interpreted to support the same observation- that more distant objects are receding more quickly, not that they are actually accelerating.

It is the expansion of space that is accelerating. The differences in the velocities of galaxies with distance are consistent with that.

Voyager and Saturn essentially 'collapsed' towards each other, contributing to their own separation velocity

OK. I'll take that as a "don't know".

 

[Guy Threepwood]

It is the expansion of space that is accelerating. The differences in the velocities of galaxies with distance are consistent with that.
'

circular- the accelerated expansion of space is based on the same assumption of acceleration based on velocities over distance

not velocities over time directly

OK. I'll take that as a "don't know".

you don't accept that the probe got closer to Saturn, before it got further away?

 

[FrumiousBandersnatch]

you don't accept that the probe got closer to Saturn, before it got further away?

I accept that the Voyager slingshot around Saturn doesn't explain how the apparent outward acceleration of the universe arises from its matter collapsing under its own gravity. You may remember being asked why that wouldn't result in a black hole.

 

[Guy Threepwood]

I accept that the Voyager slingshot around Saturn doesn't explain how the apparent outward acceleration of the universe arises from its matter collapsing under its own gravity.

no it doesn't- that's the point, there is no acceleration in Voyager 1, it is further away because it is moving faster- not faster because it is further away. And only attractive gravity was necessary to account for this observation of increased velocity over the closer Voyager II

You may remember being asked why that wouldn't result in a black hole.

It could result in many (as observed) - just as a slightly altered trajectory for Voyager I might have resulted in it becoming a permeant part of Jupiter! each body has one of two fates, coalescing or achieving escape velocity