• Question: What is the most interesting fact about physics you know?

    Asked by sawyerbean to Mark, Matthew, Mike, Paul, Sabina on 11 Mar 2014.
    • Photo: Paul Coxon

      Paul Coxon answered on 11 Mar 2014:

      There are loads! One of my favourites I like to use to illustrate how small a nanometer is if you imagine the largest aircraft carrier in the US Navy – and a seagull lands on the deck, the weight of the seagull will cause the ship to sink by one nanometer.

    • Photo: Matthew Malek

      Matthew Malek answered on 11 Mar 2014:

      Ooooh! Good question!

      There are so many interesting fact that it can be hard to choose only one! So my answer will change with time, and as we learn more. Right now, I think that the most interesting fact is that almost 70% of the universe is made up of some mysterious “dark energy” that appears to be an anti-gravity force built into the very fabric of spacetime.

      We don’t know much about it yet. Is it the “cosmological constant” that Einstein invented then later rejected as his greatest mistake? Is it something entirely different? We do know that it is making the universe expand at an ever-faster rate, though, so it will determine the ultimate fate of the universe!

      Cool question — thanks for asking!

    • Photo: Mike Lee

      Mike Lee answered on 11 Mar 2014:

      Did you know that atoms are mostly empty? And the reason we can’t walk through walls is the same reason that magnets can push each other away?

    • Photo: Mark Jackson

      Mark Jackson answered on 11 Mar 2014:

      You think you live in three spatial dimensions? You’re wrong, you only live in two.

      In the 1970’s physicists such as Stephen Hawking and Jacob Bekenstein made huge leaps in understanding black holes. They discovered that black holes posses something called “entropy” which is basically how much information it contains. Now the fact that black holes had entropy at all was pretty shocking (people had previously believed they were just big holes in space!) but the really amazing thing was that the entropy was proportional to the black hole’s surface area, not the volume! This is contrary to how things normally work: if you double the volume, you can store twice as much stuff, and therefore twice as much information. But somehow black holes encoded all their information on the surface. It took many more years for string theory to offer an explanation how this might be possible.

      Then an Einstein-level brilliant Dutch physicist named Gerard ‘t Hooft offered a simple but profound insight: black holes were the densest object Nature allows. If you tried to put more stuff into a black hole, you don’t get a denser black hole, you just get a bigger black hole. So the black hole’s entropy is the most amount of entropy you could possibly have in that region of space. And if black holes store information on their surface, than *everything* stores information on the surface. It might appear that things occupy a volume, but this is an illusion: Nature actually does the bookkeeping on the surface. If you were very very clever you could take all the information in three dimensions and encode it using only two dimensions. Another brilliant physicist named Leonard Susskind developed the idea further, coining the term “Holography” in analogy with making two-dimensional objects appear to be 3D.

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