Rebirth in Buddhism means instant mental rebirth due to craving and attachment. Buddhist should do kammas that will end all kammas so that there will be no 'rebirth' which is the basis for sufferings. We should try to be objective with our own mind and observe how do our mind interacts with the external world and with itself internally to come up with attachment to dualistic thinkings. Bit by bit we will learn to let go of attachments. This process can often be enhanced by right-meditation techniques.
Buddhist meditation is nothing but the process of objective observation of the nature of the mind.
This process would be efficient only when the mind is calm enough, but not too calm. A naturally calm person thus has no need to go through all the formal technique of meditation. Meditative observation should ideally be done at every opportunity, even when answering the calls of nature. Logical reasoning alone is not good enough but it is the initial kamma needed to develop trust so that more insights can be gained through the practice. Buddhism does not concern itself with metaphysics and cosmology.