A Blog for the Curious and the Scientifically Perplexed

This is the story of a great journey that started with a great thought. One day in 1895 a boy looked into a mirror and wondered what the universe would look like if he could travel on a beam of light. That sixteen year old boy was Albert Einstein and that one thought started him on the road to discover his Theory of Relativity. The great man has been reinvented as Albert 2.0 to come back and blog about a journey through space on a beam of light and explain the science behind everything from atoms, blackholes to global warming. If you've just joined and want to start at the beginning use the index on the left. If you're bored try these links below just for fun.


Sunday, May 20, 2007

Dark Matter and how WIMPs may save the universe

“Albert, you said earlier that the Belgian priest came up with the Big Bang idea by thinking backwards.”

Father Lemaître. That’s right.

“Well if I start thinking forwards about an expanding universe all I can imagine is a universe that gets bigger and bigger until all the stars would be so far apart you couldn’t see any.”

Excellent. That brain of yours is now starting to imagine things. Now what you say might happen but it isn’t the only way the universe could end. It might just keep on expanding, getting thinner and thinner, older and older. But then there is my great friend gravity. If there is enough stuff in the universe to generate enough gravitational pull it will start to slow down and then start contracting. Eventually everything will end up in same place. The Big Crunch.

"Then what happens?"

Well it might start all over again with Big Bang II: The Sequel. Perhaps it already has. There is one thing that science can’t fathom - what happened before our Big Bang. Gravity is trying to pull everything in the universe back into the centre. The more mass, the more gravity and the more likely it is that gravity will be able to put the brakes on the present
expansion and start pulling things back together again. Looking around the universe there isn't enough matter to overcome the present expansion. But there is a lot more to the universe than meets the eye. The fate of the universe rests on how much dark matter there is.

"Dark matter? That sounds like something from Star Wars."

Dark matter is very real and very important. It's all the bits of the universe that can't be seen. Left over hydrogen, dust, interstellar debris, pollution from advanced but ecologically unsound civilisations - that sort of thing. What sounds even more like a Star Wars invention is the idea of the 'Dark Energy.' In the last few years scientists have started to see signs that the expansion of the universe is getting faster, as if there is something pushing galaxies away.

"Something like the opposite of gravity."

That sort of thing. But no-one knows what sort of mysterious force could do this so they've called it 'Dark Energy'. Remember I put something extra into my theory to stop the Universe expanding when I didn’t want to believe it could, the Cosomological Constant.

“Your biggest mistake?”

That one. Well it turns out that today that same extra part of the equations is exactly how this Dark Energy could work.

“So you were right?”

Only in part and for all the wrong reasons. But whatever this dark force is, if it exists, the only thing that will stop this force is gravity. So it comes back to seeing how much dark matter there is. If there is enough dark matter then one day the universe will stop expanding. If not the universe will just keep going and eventually fade away.

"So the fate of the universe depends on how much dust there is lying around?"

Well, basically yes. The problem is that as it’s dark we don’t how much is out there because you can’t see it with a normal telescope.

“So we’ll never know until we start travelling around the galaxy like in Star Trek?”

No, astronomers have already found a way to find invisible things but strangely it wasn’t invented by astronomers but by an American telephone company, Bell Labs, in 1931. Karl Jansky was looking for all the different types of interference or noise that could affect radio telephone signals and he noticed a certain type of interference that appeared at round about the same time each day. This interference was found to come from certain positions in the sky, from outer space. This was the birth of radio astronomy, mapping and understanding radio signals that come from stars and galaxies.

"So are these like alien radio stations?"

No, radio waves can be created deliberately to send music and news, but the radio waves picked up radio telescopes from space seem to be naturally occurring coming from stars, galaxies and other strange objects that live out there in space. And guess what you can detect with a radio telescope?


Well some stars but the most important things are the things that you can't see with a regular telescope like dust and interstellar gas.

"So astronomers finally have a way of looking for the missing dark matter."

Exactly. Unfortunately, despite all this, they still don't think they have found all of it. Another thing that might make up dark matter are WIMPs that some scientists think will determine the fate of the universe.

“The fate of the universe lies in the hands of wimps? Albert you really have lost it now.”

WIMPs are weakly interacting massive particles. They are called sub-atomic particles because they are smaller than atoms but they don’t really interact with normal matter. A WIMP could fly straight through the whole earth, which makes them even harder to detect than dust. Wimps may make up 80% of the dark matter but no-one is quite sure.

"So most of this dark matter is still missing?"

Either they can't find it or it isn't there.

"Are there clouds of it lying around in this galaxy?"

Oh, yes lots of it. There are also things called MACHO’s which stands for Massive Compact Halo Objects, these are large lumps of dark matter like old dead stars or dense clouds.

"So which are more important for the universe wimps or machos?"

Oh, the wimps I'd say. They could be responsible for the most of the dark matter in the universe.

"And we couldn't tell if we were about to fly into a cloud of this dark matter?"

No. That's why it is called dark matter.

"And we could be absorbed, just like that, before we had reached anywhere?"

True, but we have another two thousand years of this journey to go, so I think we can reasonably assume we are safe for a few years. Anyway I never think of the future. I always find it comes soon enough. But don’t forget this is a thought experiment. So don’t imagine it happening or it just might.


  1. albert said...
    gt8 blog thanks m8
    albert2.0 said...
    Delighted you like it. Tell ur m8s
    Anonymous said...
    one bad thing has come of reading this, i knew the big crunch theory but and i thought of the whole big bang 2, or big bang 1 million, or whatever, but now i have doubts as to whether i thought them or heard them when i wasn't truly listening and they manifested in my brain as if i had thought of them, ah well, i guess i could say that of all my thoughts, all someone elses, how depressing, or enlightening that i may be the source of many other peoples thoughts
    Lawrence J. Carson II said...
    Wonderful site. Thank you for your devotion to a wonderful subject.

    You wrote "That sort of thing. But no-one knows what sort of mysterious force could do this so they've called it 'Dark Energy'."

    Please comment on the following - and if you would be so kind, email me when you do so I can back-navigate back to this answer. LJohnCarson@msn.com

    Here is the question in the form of a response to that ridiculous "Dark Energy" theory.

    #1) The Potential force of gravity exist with or without the presence of mass. Gravity is a primal force of principium ... Latin < "In the beginning". And, gravity is not the only Principium force that set all the marbles in play, its just one.

    #2) A second Principium force is Equilibrium. It's force (and formula) is exactly like that of its sister but in opposite. Its sort of what we experience when someone in church stinkers. The stinker - via the force of equilibrium - becomes equally dispersed throughout the space in the pews.

    #3) We do not need to concoct mystical myths, Greek Gods, black matter or any other irrational "notions" to explain the physics of the universal "Principiums" from which the developer built his back yard. We just need to think and ask ourselves ...
    "If I had to build what I now experience as cosmic micro and macro reality ... and all I had to work with was a scant toolbag of carpenter "Principiums" ... what would they be? What would they do, what would they look like ... and what else would I need to think about before I began building ... this tremendous system called "The Infinite Universe of Living Libraries" :-)

    I really look forward to what your imagination and incredible "current understanding maps" on the above "notions" ... will come up with.

    Thank you
    L Carson
    Boise, Idaho
    JTS said...
    I'm so disappointed that your reply to Lawrence J Carson II isn't published here for all to read. I'd be so interested to hear the reply.

    Civilisations should be civliZations, correct? Or is there a joke I missed?
    ribitfish said...
    Let's assume...
    If the big crunch theory of this universe is correct and if it is followed by another big bang (making a seconf universe) and if the laws of physics are constant (even if we dont understand them all) then wouldn't everything in each successive universe heppen exactly as it had in the the previous universe?
    Anonymous said...
    ever experienced deja vu
    Anonymous said...
    deja vu is a spiritual happening. Before we were born we mapped out our own lifes in whats called a blue-print. A deja vu experience is just a flashback of this and just to let us know we are on the right path! Or so i believe anyway!!
    Ellen Jackson said...
    Scientists can measure the expansion of the universe at different times in the its history. And, in fact, the expansion IS accelerating. They can measure the expansion by observing supernovae at various distances from Earth.

    As the universe expands, more space comes into existence. Dark energy appears to be a property of space itself. As more and more dark energy is created, the universe and the objects in it get more of a push.

    Ellen Jackson, author
    Anonymous said...
    Bear with me as I share an idea as I am approaching this thought with very limited knoweledge on how things work. Everyone says that spacetime is expanding and in fact is expanding faster as our perception of time passes. When I think of the possible ending of this I get confused with the thought of a "Big Crunch". In order for gravity to overcome the expansion and cause the collapse of the univere back to a central point shouldn't there be a center in our universe where gravity is enormous(Having an effect on ALL MATTER?)? Otherwise wouldn't all the clumps of gravity within the universe just cruch things to themselves?
    Also, since time is based on perception and relativity, then the overall age of the universe is relative to who's asking. If you ask the universe itself, how old would it tell you it is? Could it be possible that the universe's expansion and velocity of that expansion could simply be that we are still living in the time of the initial explosion in it's infanncy? To us, the initial explosion or expansion was 14 billion years ago. But what if you ask the universe itself? Could it be that if you were the universe you would consider yourself a baby and therefore the explosion process still has ENORMOUS amounts of human-measured-time to pass before everything makes sense? What if the universe itself is a living thing, and we along with everything else in the universe,(Seen, not seen, possibilities of life outside earth, etc.) are just small particles that make it up, much the same way atoms and molecules make us?

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