• Question: how did gravity evolve

    Asked by phoebe to Steve on 17 Mar 2016.
    • Photo: Steve Marsden

      Steve Marsden answered on 17 Mar 2016:

      That’s a really interesting question, and one that I’m trying to answer with my work at the LHC.

      We believe that the laws of physics do not depend on time, so in that respect gravity didn’t evolve. It’s existed since the big bang, and has remained unchanging since.

      However, close to the big bang the universe was much smaller, and much hotter. We know that the other fundamental forces (electromagnetism, weak and strong) change in strength when the temperature of the universe changes. This is a tiny effect in terms of the current range of temperatures in the universe, but the big bang was immensely hotter.

      In the LHC, we try to recreate the conditions soon after the big bang. For brief moments in time, we generate temperatures 100,000 hotter than the sun! That’s about 1,000,000,000,000°C!

      At these temperatures, electromagnetism is slightly stronger. As far as we can tell, even at these temperatures, gravity is unaffected. There are many theories that suggest that gravity should get much stronger at even higher temperatures, and so gravity would have been much stronger in the early universe.

      At the moment we just don’t know, and we need to continue doing experiments like those at the LHC in order to find out.