Aliens are out there, says former Nasa astronaut

A Nasa astronaut who has walked on the moon has claimed that UFOs are real and aliens have visited the earth.

Does he give any specific reasons as to why he thinks this?

For what it's worth, I don't think we're the only life in the universe, but I won't go and say that we get regular visits from extraterrestrials or anything.

its a vast universe, its niave to assume that we are alone in it

Well, everybody knew that.

*sigh* another one of these crazy "aliens are visiting Earth" statements.

Look. Even if we aren't alone in the universe, there's no way Earth is being visited by aliens on a regular basis and I can prove it. First: the basics. 1) No star system is within 4 light-years of our own system. 2) it is highly unlikely that any civilization that has achieved a level of technology of our level or greater exists within 45 light-years. (We would have picked up their radio transmissions easily if they were there)

That being said, for the sake of our argument we will say that civilization with a level of technology slightly ahead of our own exists 20 light-years from Earth and has somehow managed to escape detection. In order for them to travel to our star system in a reasonable amount of time, let's say they have a spacecraft that weighs 5000 kilograms and is capable of traveling at 75% of the speed of light. (At this velocity it would take them 25 years to make the journey) In order to accelerate their spacecraft to it's maximum speed, they will have to expend E=1/2mv^2 = 5,000,000(g)*810,000,000(m/s)^2 =1.64025 x 10^24 joules of energy. (and they will expend an equal amount of energy to slow down at the end of the trip)

Now that's a LOT of energy. 1.64 x 10^24 joules would keep a 100-watt light bulb burning for 5.1968 x 10^15 years. (that's right. More than 5 QUADRILLION years!) Also note that a 5000 kg spacecraft is ludicrously small (the Space Shuttle routinely carries payloads of well over 20000 kg) and it is highly doubtable that such a craft would be able to provide the necessary provisions and equipment to survive a 25-year spaceflight.

As you can see, traveling to another planet in a reasonable amount of time would require a very significant investment and would not be undertaken at all unless there was a very good reason to do so; and even then, it would not be done frequently. Bottom line: Anyone who says Earth is being routinely visited by aliens is completely wrong.

^What if they came up with a way to fold space? No need to expend all that energy traveling then.

....unless folding space requires huge amounts of energy.  I wouldn't know.

Ok, on the topic of aliens, I can say with 100% certainty that they exist.

However I highly doubt that any alien species has visited the earth and if they have it was while humans were not even on the planet. If you look at the Earth's lifetime as a 24 hour clock humans have only been here for the past 30 seconds. So chances are if any aliens have visited at any time humans were not even a species yet. So pretty much humans have only been here for 1/2880 of the entire existence of the Earth and even a shorter amount of that time is our recorded history.

Also on the topic of intelligence. Out of the billions upon billions of creatures that have lived on this planet, we have been by far the smartest and the only creatures to have obtained a high level of technology on this planet. So pretty much Humans are more intelligent than probably 99.9999999% with that 9 repeating even farther than that of all creatures that have lived on the Earth over its entire existence. So logically this same intelligence model can be used for all life in the entire universe placing humans as more intelligent than 99.999999% than all life in the entire universe. Now the chance that one of these species that is more intelligent than us is within a distance that could be traveled to reach us has been visiting us frequently completely undetected seems very improbable to me.

And the only reasonable way to travel very long distances through space is by opening worm holes to travel through which would bend space time and decrease the distance you travel, it does not actually make you travel faster just makes the distance shorter so you get there in a quicker time period that not going through a worm hole.

What about slipspace?

What you say is a very sound theory when considering 'normal' traveling abilities. However, there are also plenty of theories, and sci fi shows love these, especially stargate, about wormholes or the ability to fold space and time to travel great distances in a fraction of that time. IF, and I realize this is a big if, that is attainable then species much further out could be traveling here and elsewhere. Personally, I think that if space travel outside of our solar system will ever happen it will be with some type of technology similar to this.

Aye. I'm no scientist, but a bunch of equations and formulas(from science as we know it) cannot prove aliens have not visited. Technology and the understanding of science are always improving. Just look at how far we have advanced in the last few hundred years, or the last 50, or 10, etc.

I believe there is life, maybe even intelligent life, somewhere out there. Do I believe we have been visited by aliens? Maybe, though I'm more inclined to believe we have not been visited.