[Clutch Martin]

Not to push Carl Sagan, but he did surmise that the distances were far to great. Interdimentional makes more sense even if it is harder to grasp

[DoodleBob]

I read that the potential damage from hitting a rock or debris grows in relation to your speed. For example they kept scanning for debris on the journey of New Horizons (the probe that passed Pluto a few years ago) because at 40,000 mph a rock the size of a grain of rice could cause serious damage.

Thus, if an alien was traveling at light speed then hitting a tiny speck of something could be tragic. Compound that potential across scores of light years and, with our current technology, light speed travel is almost impossible. There has GOT to be a bit of rock somewhere between here and there, and if you hit it then KABLOOIE!!

[PUGACHEV]

The problem is we don’t know what we don’t know. Concluding that space travel from the stars is unlikely because of the great distances involved reminds me of the 19th Century scientists who opined that the Sun was less than 5,000 years old because that’s how long a lump of coal that size could burn. Of course, they new nothing of nuclear physics and coal was the only source of combustion they could imagine which might fuel the Sun.