Was out on my deck at 10pm looking at stars in southeastern, coastal Massachusetts (Cape Cod). Noticed that a few dogs in my neighborhood started barking, which I thought was weird. Looking north, I saw 2 round, cherry red spheres in what looked like a rhythmic dance. It was beautiful. The only color was cherry red, & there was a slow, rhythmic, pulse to the light.One I could see clearly outside the edges of a big tree that was blocking the sky. The other I could see through the branches of the tree. They did this rhythmic dance, like 1 went up & the other went down. Then they'd come back close, then swirl around slowly. I watched this for 20 minutes, transfixed. Then one turned & slowly went northeast, towards the ocean & lower Cape. The other turned left & proceeded southwest, towards Yarmouth. Both had that rhythmic, slow pulsing, cherry red light. The one heading towards Yarmouth I observed until it disappeared at 1030 pm, when I came in & immediately wanted to make this report.Size wise, when I came in, I looked for something to compare it to. Only thing I can compare them to is maybe the size of a small pea.It was beautiful.