Yes, atheists, like anyone else, can imagine things beyond the natural world, including imagining a light brighter than the sun. Atheism is simply a lack of belief in deities or gods and does not impose any restrictions on one's ability to imagine or conceive of things beyond what currently exists or is scientifically known. The power of imagination is a universal human capacity and is not limited by religious beliefs or lack thereof. Therefore, atheists, like people of any belief system or worldview, can engage in creative and imaginative thinking, including envisioning lights brighter than the sun.