Scientists have only searched through a tiny fraction of our galaxy, and with the fast advances in technology, we can expect many more interesting discoveries in the future. But for now, check out the handy infographic below, courtesy of Space.com, displaying all known types of alien worlds.
The Novikov self-consistency principleis a principle to solve the problem of paradoxes in time travel. The principle asserts that if an event exists that would give rise to a paradox, or to any "change" to the past whatsoever, then the probability of that event is zero. It would thus be impossible to create time paradoxes.
science is a subject that i like most of the time when we learn about whats in space and all the planets