• Question: How is gravity made? How does it actually work? What makes up gravity?

    Asked by anonymous to Steve, Emma, Christian, Bose, Alice on 9 Mar 2016. This question was also asked by 966grte22.
    • Photo: Emma Dean

      Emma Dean answered on 9 Mar 2016:

      Gravity is very interesting because we know very little about it. We know know it is an attractive force. It travels at the speed of light. We experience it everywhere all of the time.

      We think gravity works by being carried by a particle called a graviton. It works in a similar way to a photon (a particle of light) which carries the electromagnetic force. The scientists at CERN are trying to the graviton at the moment.

      Einstein’s idea of gravity was that massive objects in the universe like planets, stars and black holes, all bend spacetime. Kind of like how a bowling ball bends the fabric on a trampoline. If you roll a marble from one side of the trampoline to the other, it would dip in towards the bowling ball as it passes. It might even start circling the bowling. You could then say the marble is attracted towards the bowling ball, like earth is to the sun. Gravity is what we call this bending of spacetime. The stronger the bending, the stronger the gravity.

    • Photo: Steve Marsden

      Steve Marsden answered on 10 Mar 2016:

      Great question, and one I’ve been helping to try and answer for the past few years working on the LHC at CERN. There are four fundamental forces, electromagnetism, weak, strong and gravity. The first three of these all have particles which transmit this force. For example, electromagnetism has a particle called a photon.

      If two objects have electric charge, a huge number of these photons fly between them, transferring momentum from one to another, causing the two objects to either be attracted or repelled.

      In a similar way, it is expected that gravity has a particle called a graviton. These are incredibly difficult to detect because gravity is so incredibly weak compared with the other forces. It could even be that gravity works in a completely different way to the other forces, at this point we just don’t know.

      So far I’ve been able to show that gravitons cannot exist if they have certain properties. There are still theories that describe a huge number of different types of gravitons that could still exist though.

      When we’re only concerned with distances like those between planets and stars, we understand gravity far better. We know that gravity can be explained by treating space-time almost like a material that is curved by mass. This description works wonderfully, and predicted the existence of gravity waves, which were first measured last month! However, this theory breaks down on the sub-atomic scale and inside black holes.

      Ultimately, we’re doing our best to try and answer your question, and year by year we’re getting slightly closer to being able to.

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