Astronomy and "controlled scientific tests"

[Nereid]

Is 'dark energy' real?

What about 'dark matter'?

Do 'black holes' really exist?

How about 'neutron stars'?

Is 'Sirius B' really ~8 light-years' away?

Do oxygen, hydrogen, sulphur, etc really give those nebulae their pretty colours?

If astronomers don't have a bottle of 'nebula material' to test, in their labs, how can they be sure it's composed of O, H, S, etc?

If astronomers don't have a bottle of 'neutron star material' to test, in their labs, how can they be sure such stuff exists at all?

These, and related, questions have come up a number of times lately, in several Cafe threads, so I thought it would be interesting to discuss them.

[makc]

You mean, you will come back later and post "official" answers here, or do you expect others to answer your questions?

[astro_uk]

I'll have a stab.

Is 'dark energy' real?

If its not something very odd is going on with gravity, or their is some strange systematic in the behaviour of distant SN.

What about 'dark matter'?

Again if it don't then our understanding of gravity must be off.

Do 'black holes' really exist?

If actual BHs (i.e. a singularity) doesn't exist then something that is essentially observationally indistinguishable must, MECOs?

How about 'neutron stars'?

As above.

Is 'Sirius B' really ~8 light-years' away?

Yes, thank you parallax.

Do oxygen, hydrogen, sulphur, etc really give those nebulae their pretty colours?

Yes.

If astronomers don't have a bottle of 'nebula material' to test, in their labs, how can they be sure it's composed of O, H, S, etc?

Spectroscopy.

If astronomers don't have a bottle of 'neutron star material' to test, in their labs, how can they be sure such stuff exists at all?

Particle physics experiments.

Do I win a prize? If anyone wants a more thorough description of any point, just ask.

[craterchains]

yes, what do all those initials stand for?

[astro_uk]

SN = Supernovae
BH = Black Hole
MECO = Magnetospheric Eternally Collapsing Object

[Nereid]

You mean, you will come back later and post "official" answers here, or do you expect others to answer your questions?

I'm interested to see just how interested the readers of posts in the Cafe are in either trying to answer these questions, or (more pertinent, to this thread) the methods that can be used to get answers ... and, by implication, the methods that are not good (or worse) for getting answers.

To some extent, the "official" answers are less interesting ... than the methods.

We've recently had quite a few, quite vocal, folk post opinions (and more) that are - it seems to me - quite antithetical to modern astronomy (as a science), and which, very likely, express a deep-felt hostility to science in general (and astronomy in particular).

I'd rather like to get the bottom of this hostility (if that's what it is), and expose the inconsistencies and muddled thinking that I feel lies behind much of what we've seen here not so long ago.

Of course, in this I'm assuming - and I readily admit it - that these folk are not, in fact, profoundly ignorant of the relevant basics of physics.

It may be that they are ... the almost universal avoidance of questioning of quantum theory (e.g. spectroscopy) cf one-step removed attempted gutting of GR (and even Newtonian gravity and mechanics) may be the mark of profound, wilful, ignorance ... I simply do not know.

[makc]

the almost universal avoidance of questioning of quantum theory

I think it has something to do with this:

There is a complete disconnect between our "existing" understanding of the universe based on classical understanding, and QM. There is nothing about our understanding of classical mechanics that we can build on to understand QM. We use the identical words such as particle, wave, spin, energy, position, momentum, etc... but in QM, they attain a very different nature. You can't explain these using existing classical concepts.

... to get the bottom of this hostility ...

"These scientists think they are so smart, and know everything, and are, therefore, superior to other people, like me? Well, I've got some news for them: they don't know a shit!"

[craterchains]

I think much of the problem is "theory" being presented as something that is a fact.

[makc]

much of the problem is "theory" being presented as something that is a fact

On the other hand, folks are saying "that is just a theory", as if it was somehow a problem with it.

[Nereid]

the almost universal avoidance of questioning of quantum theory

I think it has something to do with this:

There is a complete disconnect between our "existing" understanding of the universe based on classical understanding, and QM. There is nothing about our understanding of classical mechanics that we can build on to understand QM. We use the identical words such as particle, wave, spin, energy, position, momentum, etc... but in QM, they attain a very different nature. You can't explain these using existing classical concepts.

[snip]

That's part of it, no doubt.

What I had in mind is something like this:

Spectroscopy 'works' only if you accept the modern theory of the atom (etc), based on quantum theory. Spectroscopy gives you 'nebula material 'composed of O, H, S (etc); it gives you the redshifts (irrespective of what you think the cause(s) of the observed redshifts are); etc.

Yet we see no one - here - claiming that (observed) spectra are not due to O, H, S; that lines in spectra are something quite different; that ...

Similarly with photons - occasionally someone makes some extraordinary claim about the nature of photons ... but their quintessentially quantum nature is, AFAIK, never questioned.

And yet all of astronomy (beyond the solar system) is built on (detection of) photons - surely the most powerful challenge you could possibly mount against modern cosmology (etc) would be one based on an alternative to modern quantum theory?

Why is gravity (etc) a soft touch in comparison?

[Nereid]

I think much of the problem is "theory" being presented as something that is a fact.

And this is also very curious ... other than you looking up at the night sky with your own, unaided vision, everything in astronomy is "theory"!

Or at least is so soaked with theory that the 'facts' have no independent existence.

Try it; take an astronomical 'fact' that requires more than just your unaided vision, and we'll explore just how much theory it depends upon.

How about 'Sirius B is ~8 light-years away'?

[Maddad]

I'm interested to see just how interested the readers of posts in the Cafe are in either trying to answer these questions, or (more pertinent, to this thread)

Nereid. When I first came here a few days ago, I thought you were an administrator, so I sent you a private message. You either did not see it or chose to not respond.

Most of the questions you posed fall into a category for me of being uninteresting. Dark energy and matter, existence of black holes, distance to Sirius, the chemical nature of nebula and neutron stars. What really draws me though is exploring how the intense gravity of a black hole bends the shape of distance and time. I see perhaps five frames of reference, maybe six. All discussion on the subject uses only one of them, the outside observer, with only the most superficial treatment of two more - approaching and being at the event horizon.

If you allow an artificial source of gravity, and that is a huge if, then you have the possible ability to turn it off after an inbound traveler is inside the event horizon. This would give you access to two-way travel from the moment of the big bang to the end of all time. We would need to understand what we meant by "greater than infinity" because one of those frames of reference would see the time of the outside observer as being in that category.

[Nereid]

I'm interested to see just how interested the readers of posts in the Cafe are in either trying to answer these questions, or (more pertinent, to this thread)

Nereid. When I first came here a few days ago, I thought you were an administrator, so I sent you a private message. You either did not see it or chose to not respond.

Most of the questions you posed fall into a category for me of being uninteresting.

First, welcome to the Cafe!

If a thread is of little interest to you, why not simply ignore it?

Dark energy and matter, existence of black holes, distance to Sirius, the chemical nature of nebula and neutron stars. What really draws me though is exploring how the intense gravity of a black hole bends the shape of distance and time.

From a theoretical perspective, why not read up on GR (General Relativity)?

From an observational perspective, there's little to say at the moment, other than that the best observational tests of the strong (gravity) field, to date, show no deviations from the relevant GR predictions - google on 'double pulsar', for example, or 'SgrA*'

I see perhaps five frames of reference, maybe six. All discussion on the subject uses only one of them, the outside observer, with only the most superficial treatment of two more - approaching and being at the event horizon.

Yes, but ... there is no other way that I know of to address this, observationally.

If you're interested in different perspectives, within GR, then I could suggest some resources that might be of interest ... perhaps one of the standard, classical, textbooks on GR?

If you allow an artificial source of gravity, and that is a huge if, then you have the possible ability to turn it off after an inbound traveler is inside the event horizon.

I have no idea what "an artificial source of gravity" is; could you elaborate please?

This would give you access to two-way travel from the moment of the big bang to the end of all time. We would need to understand what we meant by "greater than infinity" because one of those frames of reference would see the time of the outside observer as being in that category.

My initial impression is that you have gone far beyond the realm of anything we could cover, within 'astronomy as a science' ... but maybe that's because I simply don't understand how what you write relates to GR - can you elaborate please?

[craterchains]

chuckles, , and the fun begins.

[cosmo_uk]

MM said

Monopoles
Strings
Inflation
Dark Energy
Dark Matter
Magnetic Reconnection
Black Holes

I'm an observational cosmologist so I can give you my opinions on the above

Monopoles - who cares
Strings - probably barking up the wrong tree (thats for mathematicians to worry about)
Inflation - no matter how unlikely it sounds it does seem to work in explaning the observed properties of the Universe
Dark Energy - an adaptation to big bang cosmology that is not required by the basic theory. It just so happens that we have one set of observations that show its existence - this may change.
Dark Matter - It must be there otherwise gravity is an extremely protracted and unwieldy beast.
Magnetic Reconnection - who cares
Black Holes - well something very dense is happening in the centre of the Galaxy and external galaxies call it what you like.

[kovil]

Nice topic Neried !

And a good unfolding of the subject as well. How do we know what we think we know? That is the basis and method of science.

I hadn't thought about it for a while, but yes I do accept spectroscopy as valid, even tho I don't believe in photons ! LOL It's funny how religion and science join unconsciously when one gets into the furthest out theories of how the universe began, what is matter and energy etc. (re:Big Bang in Wikipedia, and how different religions regard this.)
Here's my shot at your poll.

'Dark Energy', is a postulation to account for problems with present theory vs. observation; but I suspect it is not real in the way it is postulated. We are measuring wrong, or extrapolating incorrectly, or both, and thusly need dark energy to fill the gap.

'Dark Matter', same as dark energy; garbage in, garbage out, and thusly dark matter is required to compensate. (now don't take my metaphor as I'm being hostile, I say this with a grin not a scowl.)

Neutron stars are a theoretical possibility, yet they may not be possible because other unknown factors are not understood by us yet. Black Holes are another more unlikely possibility, yet possible; but I suspect they are as common as a perfect vacuum.

Sirius B - seriously is it that close! Todays APOD at a mere 2500 LY seems like just a hop a skip and a jump away. Having 3 Genie wishes, one wish would be to go there on my next vacation. Parallax lives.

O,H,S spectroscopy - it is amazing how 'light' is the great communicator in this universe. It transmits information of vast multitudes everywhere at the ratio of space-to-time in this spacetime.

'nebula material' - good point, we are making an assumption that 'out there is the same as here'. This may get us into trouble, and cause dark energy and dark matter to be proposed, when the compounding of errors runs its course into high exponents.

Yes, "How we get there is 99% of the trip of Life", where we are going is often mistakenly thought to be the most important aspect. How we get there is what science is all about. Tho some theories seem to be more interested in where we are going, and devise routes to get there, and that bothers me, and is I suppose cause of the hostility I do exhibit.

Now, Dobson says that current university teaching has mistaken all of general relativity, but I do not understand well enough of what he means to express it. But I do remember his going on about how in determining the space-time distance between two light-events; the square root sign has under it; X2 + Y2 + Z2 - T2 ; being the 3 axis in 3 dimensional space x,y,z axis and Time (T) comes in under the square root sign with a minus sign.
So that the distance between the emission event and the absorption event of a light speed occurrence, is an adjacency! There is a space separation, and a time separation, but in space-time there is no separation. There are no photons that went be-bopping from every possible there-then to every possible here-now. There aren't any photons.

But on the other hand, spectroscopy is valid. So go figure!

As the Buddhists say, it is not 'either-or' it is 'both-and'.

[FieryIce]

Considering the distances involved, I'm pretty sure you'll have to leave your present form behind when you go on vacation there.

Just wear proper attire. Make sure all tray tables and seat backs are in the upright postion, for the occasion when some people get over the limit of light speed like they did with the barrier for sound.

[Nereid]

Let's take just one of Michael's responses:

[snip]

Do oxygen, hydrogen, sulphur, etc really give those nebulae their pretty colours?

I would say yes. The spectrometers we use will often tell us exactly which element is the most likely culprit for various emissions.

If astronomers don't have a bottle of 'nebula material' to test, in their labs, how can they be sure it's composed of O, H, S, etc?

The can study the wavelengths of the light in question and figure out which type of atom emits light on that specific wavelength.

[snip]

The relevant spectra - emission or absorption - of H, O, or S (in any appropriate state of ionisation) are indeed quite distinct.

But without a bottle of 'nebula material' in your hand (or you lab), how can you be sure - really sure - that what you see through your telescope was indeed emitted (or absorbed) by H, O, or S?

Or, going down a level: the spectra of H, O, and S (in any appropriate ionisation state, or any other element, or even compound) can be understood in terms of a 20th century theory in physics.

If you decide - ignore for now how you decided - that the 'nebula material' does indeed include H, O, and S, to what extent is your decision equivalent to a statement (or belief?) about the universality* of that particular 20th century theory of physics?

*In this example, at least to the particular nebula; more generally, almost all astronomical objects for which we have obtained good spectra ... in any waveband.

[Nereid]

Nice topic Neried !

And a good unfolding of the subject as well. How do we know what we think we know? That is the basis and method of science.

Thanks.

I'm quite interested in this ... but it does require at least a minimal, mutual understanding of the nature of science.

Sadly, if that minimum is not present, then it should become clear that this is not the forum for you ... and, as I think has now become clear, you seem to have such a radically different view of the nature of science that I can't see how we can have much discussion at all, in this forum.

I hadn't thought about it for a while, but yes I do accept spectroscopy as valid, even tho I don't believe in photons ! LOL It's funny how religion and science join unconsciously when one gets into the furthest out theories of how the universe began, what is matter and energy etc. (re:Big Bang in Wikipedia, and how different religions regard this.)

See what I mean?

If, for whatever reason, you choose to trash one of the most successful theories in science, in the history of humankind to date, then surely all our discussions will be pretty much meaningless, won't they?

And it's not because of anything astronomical ... it would seem that a great deal of physics - done in labs - in the last century is not within your ken.

Here's my shot at your poll.

[snip]

O,H,S spectroscopy - it is amazing how 'light' is the great communicator in this universe. It transmits information of vast multitudes everywhere at the ratio of space-to-time in this spacetime.

'nebula material' - good point, we are making an assumption that 'out there is the same as here'. This may get us into trouble, and cause dark energy and dark matter to be proposed, when the compounding of errors runs its course into high exponents.

See how it works?

If we don't have the minimal, mutual acceptance of quantum theory, then we have no hope whatsoever of discussing neutron stars ... or even astronomical spectra.

Yes, "How we get there is 99% of the trip of Life", where we are going is often mistakenly thought to be the most important aspect. How we get there is what science is all about. Tho some theories seem to be more interested in where we are going, and devise routes to get there, and that bothers me, and is I suppose cause of the hostility I do exhibit.

Now, Dobson says that current university teaching has mistaken all of general relativity, but I do not understand well enough of what he means to express it. But I do remember his going on about how in determining the space-time distance between two light-events; the square root sign has under it; X2 + Y2 + Z2 - T2 ; being the 3 axis in 3 dimensional space x,y,z axis and Time (T) comes in under the square root sign with a minus sign.
So that the distance between the emission event and the absorption event of a light speed occurrence, is an adjacency! There is a space separation, and a time separation, but in space-time there is no separation. There are no photons that went be-bopping from every possible there-then to every possible here-now. There aren't any photons.

But on the other hand, spectroscopy is valid. So go figure!

As the Buddhists say, it is not 'either-or' it is 'both-and'.

At one level, who cares?

I mean, if there is no test you could do - even in principle - that could distinguish between Dobson's ideas and GR or modern quantum theory, then all you have is two (or more) different interpretations, or philosophies. The phenomology is the same.

But if there were observable differences, between Dobson's ideas and quantum theory, then it would be an easy matter (in principle) to do experiments to find out which better described the way the universe works.

And, I suspect, those experiments would be far more easily done in earthly labs than through astronomical observations.

If so, then why hang out here? Why not go to an internet discussion forum whose scope is physics? or philosophy?