Out of the dark

13

WHEN SITTING ALONE at night, my thoughts often turn to dark topics. By this, I mean dark matter and dark energy. In the 30 years since I completed my PhD in physics, the world has changed a great deal, for better and for worse. On the negative front, I never would have imagined we would still be battling ignorant religious fundamentalism within my own country.

On the plus side, we have obtained more information about the cosmos in my lifetime than I would have believed possible. Our picture of reality has dramatically altered from what it was when I was a graduate student. In some cases, things we were virtually certain of turned out to be wrong; in others, the boldest and wildest extrapolations have sometimes turned out to be right on the money. In all cases, the universe has surprised us.


One of the things we don’t emphasise enough when writing about science is that most theoretical proposals about nature, made in advance of experiment, are wrong. Nature has a way of surprising us, so it’s vitally important to realise that science cannot proceed by pure thought and logic alone. Without the guidance of experiment, scientists are like those who choose to immerse themselves in sensory deprivation tanks. They inevitably tend to veer off into hallucination. So it is all the more telling when new unexpected clues about nature come from observations, or when some of our creative imaginings turn out to reflect the way nature really works.

ONE OF THE EXOTIC surprises physics has thrown at us in the past 30 years is the concept of dark matter. Dark matter was first inferred by Swiss astronomer Fritz Zwicky in 1933 when trying to figure out what stopped galaxies in massive clusters from flying apart. When I was a student, in the 1970s, the case for dark matter was suggestive, but not compelling. As a particle physicist, I became fascinated by the idea that particles could naturally be produced in the early universe with the necessary abundance and characteristics of dark matter today. But the game was wide open.

Neutrinos, which after all are known to exist, still seemed like a good bet to be dark matter particles, but it was still possible that our estimates about the amount of dark matter were wrong, and maybe it could be made up of boring things that simply don’t shine as brightly as stars or hot gas, such as planets.

Now, there is compelling evidence that cold dark matter is real; from direct measures of mass in galaxies and clusters, calculations of the abundance of light elements produced in the Big Bang, measurements of large-scale structure coming from millions of galaxies, and remarkable observations of the primordial seeds of structure observed in the cosmic microwave background (CMB) radiation from the Big Bang.

Observations of colliding galaxies suggest very convincingly not only that dark matter exists in profusion; but also that it cannot be made of normal matter. Moreover, candidates for dark matter may be on the verge of detection by direct detectors of the sort that I and others proposed more than 25 years ago, or perhaps may be produced in the coming years at the Large Hadron Collider.

 

Written By: Lawrence Krauss
continue to source article at cosmosmagazine.com

13 COMMENTS

  1. “Nothing prepared us for this shock, and it could take us a long time before we understand the origin of this energy of nothing.”

    I imagine this “energy from nothing” as a form of energy precipitate being force out of solution and suspended in space. I often think, perhaps other univi beyond ours creates the adequate force to compel the energy together.

    As one amoeba said to the other—”Nothing prepared us for this shock, and it could take us a long
    time before we understand the origin of these salt crystals from water.”

  2.  “most theoretical proposals about nature, made in advance of experiment, are wrong. Nature has a way of surprising us”

    …or as Lewis Wolpert says ‘Science is counter-intuitional’.

    Which is why it still eludes those with nothing but intuition.

  3. I speculate that ‘dark’ matter and energy are manifestations of the contents of a higher spatial dimension.

    In three dimensions, no two objects can occupy the same space, but fields such as gravity (which apparently is influenced by dark energy) don’t have that limitation.

    Their effects may impinge upon the 3dim domain, much as I imagine radiant energy can affect a 2dim domain.

  4.  Well, energy is different than flour. Flour is a known substance after all. But what about energy? Is energy like a substance?

    Energy of nothing would be a state, and energy from nothing would be by means of tapping in such a state. A difference indeed.

  5.  But flour is a known substance. But what about energy? Energy is different than flour – we do not know the substance of energy.

    The energy of nothing would be a state, whereas the energy from something would the process by which such energy of nothing would be tapped into.  That is a difference, and an important difference.

  6. I’m glad scientists like L.K. understand these invisible things that matter. Even when I’m very energetic, I’m relatively in the dark about Nothing – but I’ll keep reading, and trying to comprehend, even without knowing any of the math required for that …. 8-)

  7. Just finished reading L.K.’s “Hiding in the Mirror”. Was going great guns until about half way through. It was tough from there on. He seems to have such a great grasp, a grand overview of all the advances (and failures) in physics but in the final chapter, in summing up string theory, he says he’s “confused” and he wouldn’t have it any other way. Says he, “Perhaps there is no state more desired by theoretical physicists than being confused for it is confusion that compels us to seek out new knowledge and the opportunities for breakthroughs.”
    Next stop; “A Universe from Nothing”. Even more confusion?
    Feel like we’re heading back into a Samuel Beckett universe.
    Your “… in the dark about Nothing -”?

  8. Hi Quarecuss:  I wish I was intelligent enough & educated enough to comprehend enough to be confused about ‘Nothing’.
    I’m a Scientific Instrument Maker, with Scottish college engineering.  I can visualize 3D objects well, do tricky machining & fabricating, program CNC’s & Coordinate Measuring Machines, etc.
    I’m not math or science trained enough to understand theoretical physics, but I do read a lot & try to keep my brain operating during my retirement, so I can marvel at the things I accept as our best understanding of reality so far.
    I’m in awe of the work & results humanity has achieved – and I’ve added tiny bits in the auto, aerospace & nuclear industries, plus on-going motor racing & rallying.
    Good luck with your next L.K. book.  I’ll make do with his video discussions.  Mac.  8-)

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