“I think if I had to choose, I would rather have gravity instead of zero gravity. It’s fun for a while, but I’d rather live on Earth.” –Kevin A. Ford

By now, you’ve probably had a lot of opportunities to think about what holds our Universe together: the incredible force of gravitation. Although it’s the weakest known force in the Universe, there seems to be no limit to how much mass you can collect in one place. And so on the largest scales — like solar systems, stars and galaxies — it seems to be the only force that matters.

Image credit: © 1998–2015 Lynette R. Cook.

Image credit: © 1998–2015 Lynette R. Cook.

Yet the matter that we see and know of can simply not account for the gravitational force that we see, from its effects on the galaxy to the formation of rocky planets with heavy elements like our own. What’s going on, then?

Find out on our latest episode of Genesis: the story of where everything comes from.


  1. #1 Omega Centauri
    January 12, 2015

    Have thoughts about dark matter and galaxy formation changed? Last I heard without DM density variations wouldn’t have grown to the point where stars/galaxies would formed.

  2. #3 Nick Greaves
    Oxford, UK
    January 28, 2015

    I wrote to Ethan in June last year with a paper n Mach’s principle, Matter distribution and and gravitation and as I recall he was kind enough at least to reply but said he was too busy to have a look at it, which is pretty much come d’habitude. However his last little Monday film on dark matter is not impossibly far away from the questions I was asking other than I came up with a resolution which gives an explanation of sorts for this problem, and a remarkably simple one at that, however unlikely that might appear to be. Now that the existence of dark matter and energy has become more common knowledge in the last decade or two, it is no wonder that the physicists and cosmologists are in such a twit and quandary since until they come up with an explanation, it is a reasonable assumption that one or two of our existing belief patterns are awry. If they are not bothered by this obvious void in our understanding and the possible consequences , then they ought to be. The first question that seems to me to be most fundamental and the best candidate for investigation is the possibility that Light speed is variable and is indeed one which I use. If it is then all the experts and cosmologists have to really reconsider their options and whether they have to go back to square one in order to get a better grasp of nature.

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