Here are some of the very important points that Nuclear Physicist Stanton Friedman explains in this lecture.
What he is saying is that scientists are not being scientific about the alien UFO subject. They dismiss the subject without giving it any scientific thought and often come out with some very stupid statements.
Scientists dismiss UFOs because they say there is no evidence. Although if they'd actually looked in to the subject they would find that there are many official studies that came to the conclusion that alien UFOs do exist based on undeniable evidence.
Scientists talk about the vast distances between stars and state that it is against the laws of physics to travel faster than light so ETs would not come here because of the thousands of years it would take. What the scientists always forget when they say such things is that it's against the laws of physics “as we presently understand them”. Also if they thought about our laws of physics just a little bit, travelling to the nearest stars wouldn't actually take thousands of years at all.
The official account of the history of the rise of human civilisation is only around 5000 years. It doesn't take a rocket scientist to realise that other intelligent civilisations on other worlds could have had much longer histories. Think of all of the scientific developments that humans have made within the last 50 years. There will be civilisations in the universe that have had the same rate of development but instead of 5000 years, it could have been for millions of years. We can't even imagine the laws of physics they will have discovered.
Nuclear Fusion Engines
The biggest nuclear bomb was exploded by the Russians and it was the equivalent of 60 million tons of TNT.
In the second world war the largest conventional bombs were 10 tons of TNT.
Using a Nuclear Fusion (rocket) engine you can produce 10 million times more energy per particle than you get from a chemical rocket engine. You can also use the gravitational pull of planets, stars and black holes to give the spaceship a speed boost in the same way NASA used the Earth's gravity and the Moon's gravity to slingshot their Apollo spacecraft to and from the Moon in the late 60s and 70s.
1g = 9.8 metres per second squared.
1g = 21 miles per hour per second.
1g = 0 to 63 miles per hour in 3 seconds.
Speed of Light = 299,792,458 meters per second.
Speed of Light = 670,616,629 miles per hour.
It takes 1 year at 1g to get to the speed of light.
Einstein more or less said that as an object approaches the speed of light it's mass increases so much that the energy involved to travel at the speed of light would be too great.
He also said that due to time dilation the time elapsed for a passenger travelling at high speed would be less than the time elapsed for people (on Earth) observing.
So by travelling at 99.9% of light speed a trip to Zeta Reticuli (39 light years away) would only take 6 months for the passengers due to time dilation.
By the way the closest star is Proxima Centauri at 4.2 light years away.
Alpha Centauri is 4.37 light years away.
Scientists never talk about these things because they start with the premiss of it being impossible anyway. They're not even using their own scientific principles when they dismiss interstellar travel.