On the radio? You’re not talking about those late night conspiracy theory shows are you?
No, it was NPR both times. It was late at night, though.
You don’t believe in aliens, do you?
Do I believe aliens exist, and we're not alone in the universe? Yes, absolutely. Obviously I can't know for sure, but the size of the universe is absolutely staggering... at last reckoning, there are ~125 billion galaxies in the observable universe (and keeping in mind that that's what we can observe... we can observe stuff in a 13.57 trillion year light year sphere around us... but certainly we are not the center of the universe. If not, then there is more that we can't see because the universe hasn't existed long enough for that light to reach us. Each of those galaxies has anywhere from a hundred million to more than a billion stars. From what we can see now in the stars close enough to observe planets via transit across the star, earth-like rocky planets in their stars' habitable zones are quite common. So, unless our galaxy/local galactic neighborhood is somehow special and different from all the other galaxies, the number of planets that could conceivably have developed life is so immense as to be, for all intents and purposes, infinite.
Obviously life doesn't form on all such planets, and if life developed, it might not have developed to intelligent life. It's even less likely that such life would be able to explore space. And the time frame is important, too... for Earth, it existed for 4.5 billion years before life evolved to the point of being able to send out signals or go into space, which has only been happening for less than 100 years. It remains to be seen how long we will survive or how far we will evolve in our technology.
It also remains to be seen whether faster than light travel is even possible. if it isn't, then the only traveling to another planet that is possible is in your local neighborhood of stars in your own galaxy. It takes light 4 years to travel to the nearest star... assuming you could develop a spacecraft that could move just under the speed of light, that's still a LOT of travel time to go anywhere else. But I'm not prepared to say that it's definitely not possible to travel in some non-physical way, perhaps by bending spacetime.
Do I believe that we're being or have been visited by aliens? I don't know. Probably not, it's much more likely we haven't been/aren't. But it's also possible. Do I believe that aliens exist in the universe? I am as close to 100% certain as it's possible to be that they do, in uncountable varieties. What makes us so special that our planet alone developed life in all of the vastness of the universe? On the order of 10^20 stars in the universe is a HELL of a large number of chances for life to develop.