Problems with an Infinite Universe

Michael Bronson writes:As I mentioned earlier, I don’t believe UFOs are flying saucers from outer space because I think it would be very impractical for extraterrestrials (if they exist) to make fly-by visits to our world. There are six major reasons I feel interstellar travel is physically unrealistic. They are:
Distances are too great. If we could travel 10 times faster than our fastest spaceship, it would still take us 8,200 years to reach our closest star.
Ultra high-speeds are impossible. To propel a spaceship the size of NASA’s space shuttle to 50% of the speed of light, it would take energy equal to 23 million atomic bombs. This estimate does not even include the weight of the fuel and rockets needed to get the shuttle into earth’s orbit (which is 95% of the shuttle’s weight at the time of launch). In fact, this estimate does not include a large number of things that would add weight to the spaceship.
Collision problems. Running into a pebble the size of a pea (while flying at 50% of the speed of light) would produce kinetic energy equal to 2.2 atomic bombs.
Force fields could not protect ultra high-speed spaceship. Even if "force fields" technically could be designed, it would be impossible to supply them the necessary power to protect ultra high-speed spaceships. As stated earlier, hitting a pebble would generate energy equal to 2.2 atomic bombs. Therefore, the energy powering the force field must be at least that great to absorb the impact. In fact, (as the chapter shows) this number needs to be multiplied millions of times for every second of use.
Outer space is anything, but empty. Outer space is full of hidden objects that can completely destroy ultra high-speed spaceships.
Difficulties in detecting objects in its path. Let’s say a spaceship has a "radar" so sensitive that it can detect a rock the size of a TV at 10,000 miles. If it is flying at 50% of the speed of light, the pilot will only have 4/100th of a second to respond.
Difficulties in avoiding objects. In the above scenario, the flight adjustment to avoid the rock would produce 1.8 million Gs of G force. Three Gs will give a fighter pilot red eye and nine Gs can kill him.