New Clues About the Nature of Dark Energy

Jim Mansfield writes "With the Hubble space telescope no longer being serviced by NASA, it's good to see one of their hardest working and most famous satellites in the news again. According to their press release on the nature of dark energy, Einstein may have been right after all - and even if he turns out to have been wrong, it seems that dark energy is not going 'to cause an end to the universe any time soon' ... whew, that's a relief." See also a space.com story.

I wouldn't worry

I wouldn't worry about the Hubble, it will just end up drifting off into space only to return 300 years later as H'ble, the super intelligent sentient telescope of the future, bent on destroying the human race.

Ok, so maybe there is reason to worry....

Re:I wouldn't worry

Is that why we will have to go back in time to get a whale to talk to the evil telescope... no.. wait.... we will have to explain to it why we decided not to repair the telescope and give it an extended life.....dammit, I'm all confused now...

May I just be the first

To say the dark side of the force is much much more powerful than the light.

The Sith Lord awaits.

The restaurant at the end of the universe

..dark energy probably won't destroy the universe any sooner than about 30 billion years from now, say Hubble researchers.

The restaurant at the end of the universe must be really far...

Racists!

the dark energy probably won't destroy the universe any sooner than about 30 billion years These damned white scientists are racists: yesterday they said that a black hole destroyed a star, now this: the dark energy will destroy our universe!

...End of time?

If the repulsion from dark energy is or becomes stronger than Einstein's prediction, the universe may be torn apart by a future "Big Rip," during which the universe expands so violenty that first the galaxies, then the stars, then planets, and finally atoms come unglued in a catastrophic end of time.

This is quite a shift from the implosion theory that results in pre-'Big Bang' conditions causing a loop in time.

Re:...End of time?

Yeah, but that theory's been out of vogue for a while. It's theoretically tidy (and therefore attractive), but I believe the last few years' astronomical data has shown the universe's rate of expansion is accelerating. Something new woulkd have to turn up for the Big Crunch to come into vogue again.

Re:...End of time?

I always wonder whether the "It's accelerating so it'll drift apart in the end" folks understand basic calculus. The rate of expansion accelerating doesn't mean it will continue accelerating

Well, if you've done any General Relativity you'll know that for a standard cosmology (FLRW cosmology), the final state is one of recollapse, asymptotic expansion, or accelerating expansion. This end state depends on the total mass-energy content of the universe and the nature of the dark energy (cosmological constant). It really isn't a lack of understanding of "basic calculus", but rather a deeper understanding of the physics involved. So, basically, we don't need to know all the derivatives -- we just need to have an understanding of the potential in which our universe evolves.

Re:...End of time?

Of course they understand basic calculus. They just also understand the currently prevailing model for the constitution of the universe and its evolution. To have the accelerating expansion stop accelerating, decelerate, or turn over would require some additional, extremely bizarre physics that's not indicated by any observation or experiment we presently have. This may seem like an odd constraint for me to place when we're talking about something as bizarre as "dark energy", but it isn't. There were a lot of theoretical reasons from both cosmology and elementary particle physics (and even a few vague extragalactic observational reasons) to at least consider that the cosmological constant may be nonzero; that's why the two high-z supernova teams did their work. And now there's still harder data suggesting same. In contrast, there's just no reason whatsoever to presume unbelievably bizarre physics of the form necessary to produce the behavior to which you appeal. The scale-factor dependence of the currently-known components of the Universe don't have the higher-order derivative behavior you appeal to; while coming up with a hypothetical field that does is pretty damned hard. That doesn't mean you're wrong, of course; it just means the odds are very highly against you. The claims they're making are almost certainly true.

Re:...End of time?

I always wonder whether the "It's accelerating so it'll drift apart in the end" folks understand basic calculus.

You always wonder whether astrophysicists understand basic calculus?

I'm doing my best to come up with something witty or intelligent to say to that, but I'm having trouble coming up with anything more than "What...? Huh?"

Considering that modern physics is largely just a whole hell of a lot of math, yes, I think it's safe to say that astrophysicists understand the principles of calculus. Have you even seen a modern physics paper?

Big Rip a Big improbability

If you fear things involving physics, skip the rest of this post. Alright, for those who are interested, it seems like 70% of the current energy density of the universe is in some form of "dark energy", as was previously stated. The Universe is currently 13.7 billion years old. We say that every component in the universe has an energy density and a pressure. Dark energy is different from things like normal matter and light, because these have positive pressures. (Normal matter has a very small pressure). But dark energy has a negative pressure, which means it works opposite to gravity. Everything that has a pressure that we can physically think of (well, that I can physically think of) has a pressure between (-1)*energy density and (+1)*energy density. A big rip will only occur (and it will only occur in the very distant future) if the dark energy has a pressure that is outside this range, such that pressure is less than (-1)*energy density. This is, of course, possible, but unlikely in my view.

That's one depressed satelite!

Poor, poor huble. Getting scrapped by Nasa. You can just see he's getting really depressed. He already has a black outlook on life, all that dark energy...

Well, it's his own fault now, giving us back such negative waves [the-ocean.com].

Reinout

Never underestimate the power of the schwartz!

Oh sorry, I thought the headline was New Clues About the Nature of Dark Helmet.

"Now you see that evil will always triumph, because good is dumb!"

- Dark Helmet

The future of the Unvierse

After we have all (I assume that doesn't include any creationsists) adhered to the scientific theory of The Big Bang and the beginning of the Universe as we know it, I can only think that we can begin to accept the fate of the Universe.

As dark matter destabalizes, essentially matter is pulled apart at the atomic level. Some thing tells me The Big Rip, is what we are in for.

The universal constant is a nice theory and would be the better, happily-ever-after option, but in reality it seems a little far fetched if the expansion of the Universe is accelerating. It means that eventually speed will over come matter and every thing disintegrate and get ripped apart.

Big Rip != Acceleration

The fact that the universe is accelerating is not the same as the "big rip". The accelerating universe, as we understand it now, sort of means that the space between everything and everything else is getting bigger all the time. However, in order to discover this (and the expansion of the universe in general), we have to look at very distant galaxies - we don't see our own galaxy flying apart, and some other galaxies bound together in our local galaxy cluster are orbiting or moving toward ours. In general, objects that are in bound states - whether gravitational bound states (like solar systems and galaxies) or other bound states (atoms, etc.) will remain held together even as the distant galaxies which are not tightly bound to us zoom away. Our own situation on earth would be completely unaffected - you'd need a big telescope to even tell the difference. The idea of the "Big Rip" is that this condition that "bound things stay bound" (the dominant energy condition) might be violated, that dark energy might be so extreme that not even bound objects could keep from eventually dissipating. That idea is HIGHLY theoretical - there's no particular evidence for it, and until recently most theorists thought it was ridiculous. But, of course, this is science - we have to think about even the weird possibilities.

Relief?

If a big crunch doesn't end the universe, then heat death will. Eventually the universe will reach a state of maximum entropy, and nothing interesting will happen.

Before it gets to that stage, stars will become a rare occurance. The chain of star birth and death results in smaller stars, and once stars get small enough they become like our Sun -- too small to undergo the explosive death that would provide enough mass for future stars. Eventually there won't be enough clouds of hydrogen massive enough to start nuclear fusion.

Given enough time, current theories suggest that the universe seems to be screwed either way.

Re:Relief?

It's true that entropy can decrease when matter/energy enters a spontaneously ordered state, e.g. all the gas collects in the corner of the room. In itself that's infinitesimally unlikely, yet still possible. But in the case of the universe we live in, there's an additional wrinke. The edges of the "room" are expanding faster than the speed of light. Which means, eventually, every particle will disappear over every other particle's event horizon, and it will be impossible to put them back together again.

Another person downthread alludes to the idea of surviving through increasing entropy by presumably using decreasing amounts of energy. In other words, as the universe gets older and colder, there will be, say, 1/100th the free energy available utilizable by a heat pump. So a form of alife could simply run itself 100 times more slowly and thereby experience time subjectively at a linear rate. Right? Wrong. Two problems pop up. One is proton decay, which means the building blocks of any sentient computer will eventually decay on their own. And second is the cosmic background radiation. Machines work on the principle of taking in energy and outputting it in the form of waste heat. But once the universe has cooled down to the same temperature as the CBR, it will be impossible for any machine to output waste heat. It will cease to function. There is some work being done on reversible computing [mit.edu] which might, in the long run, be able to tackle the second problem, but not the first.

Re:Relief?

Stephen Baxter (I think?) wrote a very good book (Time) based around the idea of heat death. Some of the ideas that civilzations come up with to make the most out the last remaining energy in the universe is very neat. Well worth a read.

non-physical physics

Right now we're about twice as confident than before that Einstein's cosmological constant is real,

Of course, 2x (near-as-dammit-zero-certainty) is pretty much the same as (near-as-dammit-zero-certainty)...

A lot of new physics does seem to be increasingly theoretical and "out there" on the proverbial limb. It would be good for the practical lot to catch up with the theoretical lot... unfortunately, trying to verify these out-there hypotheses seems to involve larger and larger atom-smashing accelerators. Lets just hope they don't need to find the 'Higgs Boson' (hint: ohhh WAAAY ohhh, ummm barrray :-)

Simon

Re:non-physical physics

A lot of new physics does seem to be increasingly theoretical and "out there" on the proverbial limb

All new physics is out on the proverbial limb. Galileo's ideas were so outrageous at the time that the church had him outcast from society (IIRC).

It doesn't take that much of an open mind to consider these new (or old) theories based on new facts. But, I'm glad the majority don't follow such theories, because most people tend not to leave things in the grey ("THIS theory is RIGHT") otherwise, actual scientific progress would be severely hindered, as people would become quite disheartened, and possibly ANGRY at science.

It would be good for the practical lot to catch up with the theoretical lot...

The border between "Practical" and "Theoretical" isn't very black-and-white either. Often theoretical sceince leads to very practical applications (as in the case of forward error correction, originally just mathematics) and practical turns out quite sour (as in the Wankel(?) engine).

Just my 2c

Re:non-physical physics

Actually, Galileo was excommunicated, which at the time was almost as bad as being driven out entirely. In addition, he was placed on house arrest and was confined there until he died, refusing to recant his observations.

Great man.

Dark Matter and Ether

I find it strange that scientists 'believe' in dark matter. The main reason for the hypothesis that dark matter exists, is that otherwise those huge systems of galaxies don't obey Newton's laws. However, throughout the 20th century, there have been numerous occasions where Newton either was proven wrong or where fields of science were found where his laws weren't applicable: ether didn't exist, at nanoscale Newton's laws don't apply (quantum mechanics), at very high velocities they don't either (relativity), and in very complex systems Newton can't be used (chaos). Why would it be so strange if systems with enormous scales and very small accelarations would not obey Newton's laws? It does feel a bit like Ether to me to introduce a form of matter/energy which has never been measured at all...

I think dark matter doesn't exist. It can be useful in the models, like ether could, but nothing more than that.

Re:Dark Matter and Ether

and in very complex systems Newton can't be used (chaos)

Hang on a moment; I thought the Lorenz attractor (which is the canonical example of chaos) was based on a system obeying Newtonian mechanics.

Why would it be so strange if systems with enormous scales and very small accelarations would not obey Newton's laws?

This is the line of thinking which led Mordechai Milgrom to propose Modified Newtonian Dynamics (MOND) in the 1980s. MOND posits that Newtons second law (F=ma) is modified when the acceleration is very small. It is able to "explain" the unusual rotation curves of galaxies, without the need to invoke dark matter. It can also explain phenomena which the dark matter hypothesis can't, such as the Tully-Fisher relationship observed in the surface brightness of galaxies.

However, its important to remember that MOND cannot be considered a physical theory; it is more of an empirical modification of known physical laws (like the Lorentz transformation was), which still awaits a physical explaination.

Re:Dark Matter and Ether

It can also explain phenomena which the dark matter hypothesis can't, such as the Tully-Fisher relationship observed in the surface brightness of galaxies.

The Tully-Fisher relation has been explained by dark matter for some time. You can find a brief derivation in Carroll & Ostlie p. 1002, for instance. There's no need to invoke MOND at all - it just comes from the fact that the luminosity is proportional to the maximum velocity to the 4th power, which you can get by using the expression for total mass contained within the galaxy derived from rotational velocity curves.

Re:Dark Matter and Ether

I was under the impression that dark matter needs fine tuning to explain Tully-Fisher

Yes and no: The typical Tully-Fisher coefficients for Sa, Sb, and Sc type galaxies are 9.95, 10.2, and 11.0 or so. These are all within 10%, and for Sa and Sb types, within 5%, of 10. Simple assumptions get you a coefficient of 10, if you assume that the mass-to-light ratio is the same for all spirals, and that the surface brightness is the same for all spirals.

The first assumption (mass-to-light ratio) is a clearly idiotic assumption. It assumes that galaxies form with same proportions of light and dark matter, which we *know* is not true for other types of galaxies (dwarf ellipticals, in particular). Aside: This is also the "nail in MOND's coffin", more or less - MOND was hoping to replace the dark matter hypothesis by saying physics works differently at large distances. The problem is that galaxies which contain the same amount of light-emitting matter and have the same spatial extent should therefore have the same rotation curves. This isn't true. You then have to add a new parameter with MOND to fit it, which is OK, sure, but now you've started to lose the elegance originally intended, and now MOND becomes a more complicated theory than the dark matter hypothesis, which just says "well, that galaxy formed around less dark matter."

Anyway, back to the subject: the point is that those two assumptions clearly are not completely true, and therefore there's plenty of room for a 10% correction due to forming biases in spiral galaxy types. If the mass-to-light ratio is a very weak function of mass (which is believable - perhaps smaller galaxies formed when the dark matter density was slightly lower, due to their late formation times), you can easily get those corrections.

MOND allows you to get that 10% correction due to the parametric fit of the rotation curve, which is essentially identical to the way that it's done in the dark matter case - the corrections are due to the variation in the rotation curve, which MOND says is due to a modified Newtonian field, and dark matter says is due to a dark matter density. It's the same reasoning - one isn't more natural than the other.

(It should also be noted that the Tully-Fisher data has a crapload of spread to it, just like all astronomical data. Each galaxy varies a fair amount.)

Re:Dark Matter and Ether

The article is about dark energy, not dark matter. Those are two distinctly different things. Dark matter is simply matter that has not been found, but that astronomers assume must exist to explain certain gravitational behaviour as observed in galaxies. AFAIK there is not much controversy over wether dark matter is real or not. Dark energy however is theorized to be a force that acts opposite to gravity, and that could explain why the rate of expansion of the universe seems to be increasing.

IANA astronomer, but that's what I've understood from the stuff that I've read about it. Pop science ofcourse because the math is way over my head.

There's more to dark matter...

You're right, the natural step when we learn that the universe doesn't obey Newton's laws should be to try to modify Newton's laws, not to imagine that there is a magic 95% of the universe with funny unobserved properties. The thing is that this isn't the only evidence for dark matter. There are a number of different lines of evidence which lead to the same conclusion - the orbital behaviors of galaxies and their clusters, the adundances of various light elements in the universe, the behavior of the cosmic microwave background, x-ray emission from clusters, etc. It turns out that no matter how hard we try, we can't modify Newton's laws to get the right answer to all of these. Gravitational lensing (the bending of light by the mass of distant galaxies and clusters) is really impressive in this regard - modifying Newton's laws (and general relativity) in the desired ways should have essentially no effect on it, and it definitely looks like there's dark matter (and even allows us to map its distribution). Dark matter really seems like the SIMPLEST answer, from the point of view of someone who knows the data! Dark energy was the subject of the article, however, and that's quite a bit different. As of right now, I'd say that we DON'T have very convincing evidence that this isn't just a modification of general relativity. All of our particle physics-related ideas seem far too complicated. Oh, and chaotic systems still obey the laws of classical physics - the systems are just so complicated that knowing how the individual atoms are behaving is not very helpful for predicting the behavior of the macroscopic system.

Correct me if I'm wrong

But the "Cosmological Constant" Einstein was credited for theorizing on was Ether, and eventually disproved the existance of Ether himself by somehow using the earths revolution around the sun.

While this may be a completely seperate idea, it definitely appears that the author is mixing these two (Dark Energy and Ether) Einstein theories.

Re:Correct me if I'm wrong

You're wrong. Aether was thought to be a physical fluid whose ripples were the basis of the wave-like nature of light. This was proven not to be so by Michelson and Morely, who showed that the speed of light was the same no matter if it were going with or against the aether (which was presumably flowing past the moving Earth). Dark energy is a field, like light or gravity, which presumably has no preferred frame of reference (like light or gravity).

The article you must read

It seems this "dark energy" is quicker, easier and more seductive.

I'd buy that for a dollar!

Everything's nonsense

The end of the unverse makes me depressive. Nothing that is eternal. No sense in building up things, inventing, scientific discoveries and everything. Just nonsense. Well, if you do not believe in god or are at least agnostic.

Well, back to my OSS/FS projects to gain fame in this dark world :)

Dark Matter? My god...

.. it's full of Goths! I hereby dub the matter 'Mopotronium

Dark Matter conclusively identified...

It's like regular matter, only it has a goatee. I thank yew.

Einstein was wrong anyway

It wasn't the introduction of the cosmological constant per se that Einstein thought of as his greatest blunder, it was the failure to realize and predict that the Universe is expanding. The cosmological constant he had there to get a static universe, and that's bad. Also, the cosmological constant isn't Evil, it comes rather naturally from solving the equations. I never got as far as actually doing that, but I followed a back-of-envelope solution once, and it comes out sort of like an integration constant. I think of it as a natural parameter that should be constrained by observations just like any other parameter, and I see no particular reason why it should be 0.

Re:Einstein was wrong anyway

Actually, the cosmological constant can result in an expanding universe.

Re:Einstein was wrong anyway

This whole "Eistein was right after all" angle is misinformed. He wanted a static universe because that was the historic conception of the universe. His own science didn't allow for it, but he wrangled an equation for one out of it anyway. Turns out he was wrong, is wrong, and will always have been wrong. Einstein's motivation for putting in the cosmological constant was ideological, not observational -- and that's a recipe for Dumb Science.

Dumb Science isn't "right after all," no matter how much you respect the guy who came up with it.

Re: Einstein was wrong anyway

> This whole "Eistein was right after all" angle is misinformed. He wanted a static universe because that was the historic conception of the universe. His own science didn't allow for it, but he wrangled an equation for one out of it anyway.

Remember that at the time Einstein introduced it (1917, if a Web search didn't lead me astray) scientists still thought "the universe" and "the galaxy" were the same thing. We tend to forget how vastly our understanding of the universe has changed in the past ~80 years.

Duh!

I doesn't take an Einstein... oh wait. Nevermind.

Are you Corn Fed? [ebay.com]

No info...

...in that article. I was hoping for a hint as to what dark energy is, but this article simply states possible changes in theory.

At the end it states, "Understanding dark energy and determining the universe's ultimate fate will require further observations." Well great. Didn't we know this already? *sheesh!* Thanks for "almost" nothing....

No, really?

From the article:
"Riess' team uses Hubble to find stars that exploded when the universe was about half its present age. A certain type of these supernovas, as they are called, shine with a known brightness."

Supernovas, you say? Wow, what a fascinating new concept for readers of Space.com!

I mean, come on!

Dark energy

Could this possibly be the counter force to grvity?

Filling the blank?

I get the feeling that we are trying to fill
a gap but with what???
Observer: Look at those galaxies..they are moving appart.
Braniac: Yes, that's because the big-bang long long time ago.
Observer: They look very old and they appear to move slower as they drift compared to the young galaxies.
Braniac: Of course, they are loosing momentum. But don't be deceived, at some point all universe is going to loose cohesion and become rippi-bits!
Observer: Howbout that cluster over-there? Those galaxies are quite old and they are driftin faster than the young ones! What gives??
Branica: Er ur..is dark energy pushing them appart, dark energy is spreading the galaxies.
Observer: And the big bang.
Braniac: yes, that too ..explosions and ever
present dark-energy.
Observer: Far out!
Braniac:(scratching her head and punching madly
at her calculator and giving a big sight of
frustration)yeah, riveting.

They were wrong ??

"This would lead to a "big crunch" where the universe ultimately implodes. "This looks like the least likely scenario at present," says Riess."
This can't be, coz' even Red Dwarf had an episode about that [nildram.co.uk]!

http://www.ebtx.com/ntx/ntx16.htm

Whats more likely? This mysterous dark energy exists and compromises 70% of the mass/enery of the universe even though we can't see it anywhere locally, or our theories are wrong?

I suggest reading www.ebtx.com on the nature of dark energy. This guy is right, or at least close.

Matter attracts matter; this we know. The rest of the theory explains that space attracts space, and matter repels space. Matter and space are polar opposites (as well as logical opposites).

Einstein wasn't relative enough in his theories. He declares C as constant and bases all other observations off it, when in fact you can change all the physical constants continuously and arrive at the same results. If C changed, as long as h, G, and about 18 other 'constants' also changed, we couldn't tell, from our point of view.

Is the universe expanding, or are we all shrinking? From a relative point of view there is no difference.

A more detailed article on the same:

http://www.space.com/scienceastronomy/big_rip_0303 06.html> more on buig rip Here

"the repulsive force"

is how it's described in the article. I think that's a bit unfair. It can't help its appearance.

The main problem with Dark Energy...

...is that no mainstream theory predicts its existance. It is based solely on observations. Scientists try to bend/modify current theories in order to include Dark Energy.

Many formulas and theories are based on observations, however, a good theory not only describes current observations, but predicts things which are not observed, yet. Like Einstein's theory predicted time-dilation, the curvature of space-time, etc. and gave a solution to the orbit of Mercur (which Newton's theory was unable to explain).

A new theory may be needed to include the Dark Enegy from its foundations or to explain these phenomenas without Dark Energy.

A "Circular" argument?

Whatever happened to the idea that something going away from us would eventually "re-appear" on the opposite side of the Universe and start heading towards us? (I have no clue what hypothesis was/is called.) Perhaps everything expanded to the edge, ALREADY, and is now "expanding" towards the center, again, and is therefore being more attracted to everything else cause it's getting CLOSER! (I have to stop now. My brain is going to take a little break.) Whew. Next?

big rip?

Take cover! The big rip has already started, it's called SCO! oh, wait...sorry, that's "the big rip off".

*phew*

and I thought it was about Enron again.
(or if u live in california, any company that sells power; duke, reliant, etc.)

and in the computing world; SCO at the moment though history shows that it'll return to microsoft as soon as SCO goes under (it's not a matter of if but a matter of when).

This Einstein was right stuff

It's true that it's looking more and more like we live in a Universe with a nonzero cosmological constant. But that doesn't mean Einstein was right. Einstein introduced a nonzero cosmological constant for a very specific reason: to make a static universe. He lived at a time when the general metaphysical assumption was that the Universe was static and unchanging and had been around forever and always would be. So when he created his field equations and discovered that they insisted that, with a reasonable model, a universe must expand or contract, he introduced a cosmological constant with the intent of negating that expansion or contraction, resulting in a static, unchanging universe. (Specifically, he thought the universe was closed -- this is one of his boundary assumptions in general relativity -- but static.)

Now it turns out that we seem to live in a universe which is not only, to most cosmologists' surprise, open, but also with a nonzero cosmological constant that is accelerating that expansion. The entity -- the cosmological constant -- which Einstein introduced would appear to have some use (though in fact we already knew that, since inflation theory, a pretty solid part of our Standard Model, involves an effective cosmological constant), but not for the reasons he introduced it (that is, our universe is emphatically not static and the cosmological constant does not help it become so). In theoretical physics, you don't get bonus points for getting the right answer for the wrong reasons.

In fact, in many ways, theoretically the cosmological constant is a bad theoretical feature, because it indicates a tweakable parameter that you need to find observationally -- hence, the desire to find the theoretical basis for the value of the cosmological constant.

Quick summary

w=-1

This comes as a great shock to exactly no one. ;-) Postulating anything else is like introducing epicycles when you've only just figured out that there are orbits.

[TMB]

Questioning dark energy

Coming from a classical perspective, matter would be "condensing" from the primordial "hot stuff" for a long time after the Big Bang. Classical hypothesis is that E + Matter = E +Matter for the universe in the long haul. I ask as a layman: the condensation of matter for a long time following the big bang would have equated to a gradual increase in gravitational forces, wouldn't it, because matter expresses gravitation more effectively than energy? At some point about five billion years ago, the condensation of matter crossed a threshold where it no longer condensed from the primordial "hot stuff" at a rate sufficient to override the expansion of space and the contained energy from the original expansion. The universe at that point didn't accelerate so much as it continued to expand with less overiding constraints from the diminishing role of condensing matter. Perhaps matter is less infinite than energy in the equilibrium of this universe. Is dark energy only the limiting of exhausted matter in the grand equation? That being said, I hope for tapping the energy of the zero point field and the success of overunity devices based on that premise. I tire of classical explanations--including my own--based on post-classical observation

Asimov

Isaac Asimov is certainly best known for his work as a science fiction writer. What most people don't know is that he also knew and enjoyed science. I don't have the understanding to discuss many of the theories that I have read here being debated, but I think something Isaac said once bears repeating. From his scientific work "The Neutrino", let me paraphrase:

If you take a red ball, and throw it up in the air, you will observe it come back down. You can repeat the experiment with the same results. You can use a different red ball. Eventually you may adopt the theory that red balls when thrown up must come back down. You may eventually expand that theory to include blue balls, and then green balls, and then any ball. That would lead to further experimentation and the conclusion that "what goes up, must come down."

Later on though, you may let go of the helium balloon that you were holding. Helium balloons do come back down once they've gone flat, but you may need to modify your theory to say "what goes up, must come down, but not necessarily right away." Airplanes do this too. But what if something reaches escape velocity.

"What goes up, must come down, but not necessarily right away, and only if it doesn't reach escape velocity."

As our knowledge and data base grows, our theories expand or get thrown out in favor of something that better fits our observations. But they are just that: our observations. If a model doesn't fit an observation, don't blame the model, or the observation, or the scientist. Such will only be modified again as our understanding grows.