Earth Revolving in Sun's Orbit

<html>
<head>
<link rel="stylesheet" href="style.css" />
</head>
<body>
<!-- Right below is an image of the sun -->
<img id="sun" src="http://goo.gl/PmbqZa">
<div id ='earth-orbit'>
<img id="earth" src="http://goo.gl/41IWnf">
</div>
</body>
</html>