• Question: why do planets float in the air in space?

    Asked by to Jim on 17 Jun 2011. This question was also asked by .
    • Photo: Jim Caryl

      Jim Caryl answered on 17 Jun 2011:

      Well, it’s not my area, but I spent my time growing up with a nose in an astronomy book, so I’ll give it a go 😉

      Planets appear to float, but in fact they in fact sit on what is often called the ‘fabric of space’. There is no air for them to float on, as space is a hard vacuum, so there are no (or at least very, very few) atoms or molecules around at all. The planets are all held in place by the sun.

      One way to think of it is to think of the solar system as a table cloth (this represents the ‘fabric of space’), and the sun as an apple sat in the middle of the table cloth. It will make the table cloth dip slightly towards the middle from all sides – the dip in the table cloth represents the effect of gravity.

      Each of the planets, depending on their size, will be differently sized (and much smaller) fruits, each of which would make their own little dips in the table cloth. It is the little dip (i.e. gravity) that Earth makes that causes the moon to circle around it.

      Now, if you just placed the fruit/planets on the cloth, and they weren’t moving, they would just roll towards the apple at the middle. However, all the planets are in motion, they are continually accelerating to avoid rolling into the middle of the ‘tablecloth’, and they travel at such a speed that it balances the gravitational force (the dip of the tablecloth) made by the sun.

      Hope this makes some sense to you?

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