Besides being a characteristic of space, gravity is also a force but it is the weakest of the four forces , and it might be a particle, too. Some scientists have proposed particles called gravitons cause objects to be attracted to one another. But gravitons have never actually been observed. Another idea is that gravitational waves are generated when an object is accelerated by an external force, but these waves have never been directly detected, either.
Our understanding of gravity breaks down at both the very small and the very big: at the level of atoms and molecules, gravity just stops working. The problem is that our understanding of both particle physics and the geometry of gravity is incomplete. Pamela Gay. We have written many articles about gravity for Universe Today. This recent article discusses how the latest research looks at quantum physics to explain gravity. Listen here, Episode Gravity.
Very creative and informative.. This continuing series of videos is always welcome! See the diagrams. Encourage classroom discussions interpretive discussions which explore the interaction of gravity forces with air resistance and frictional forces.
An approach is to compare the motion of two sheets of paper, one flat and the other crumpled into a small ball, when they are released at the same time from the same height. The gravitational forces acting on each are the same but their relative motion is very different due to the action of air resistance. Extend the discussion to explore the forces acting on skydivers during free fall and when using parachutes.
POE Predict-Observe-Explain : to help students think about their relative sizes, ask students to predict which of these forces is smallest: magnetic, electric or gravity forces. Then ask them to observe a hair sticking to a charged comb and a hair clip sticking to a magnet.
While this activity is imprecise it opens up discussions about the relative strengths of these forces. Our website uses a free tool to translate into other languages. This tool is a guide and may not be accurate. For more, see: Information in your language. You may be trying to access this site from a secured browser on the server. For example the fact that it acts equally on all objects and substances becomes obvious when you thing of gravity as a distortion of space-time rather than a force.
Imagine that you are in free space, away from any planets or stars, when suddenly a planet is created quite close to you. You would not be aware that anything is happening to you, you would feel no force, but you would find that you started to accelerate towards the planet. This is just like the case where you travel through space, you are not aware that you have also travelled through time but people observing you are. You can argue that we do not.
What happens is that, as you pass through time, the distortion of space-time caused by the presence of the earth accelerates your body towards the centre of the earth. But when your feet are touching the ground, the ground exerts a force on your feet in an upwards direction which pushes you in the opposite direction. In other words you are being accelerated upwards with respect to space-time by the force of the ground acting on your feet.
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