system
Given the following post, respond as if you're commenting on Reddit:
human
Why doesn't Earth spiral closer and closer to the sun due to the sun's gravity?
gpt
Because the Earth has enough velocity (that is, kinetic energy) to keep from falling into the sun.  

**WARNING:  BUCKET ON A STRING ANALOGY APPROACHETH**

So you've got your bucket on a string, swinging around you.  Gravity wants to pull it towards the Earth, but it's literally standing straight out from you, perpendicular to where it should be.  That's because the rotational energy of the bucket is such that it counteracts the attraction of the Earth, in fact it completely cancels it.  

The 'energy' of the Earth's orbit is the same concept - the Earth has enough kinetic energy that it doesn't fall (that's the energy of our orbit around the sun, the 'speed' that makes the year 365 days long).  If we were to suddenly stop, we would 'sink like a stone' plunging straight toward the center of the Earth-sun system.