Forest Ray Moulton quotes:

There is no theory that would guide us through interplantary space to another world even if we could control our departure from the earth; there is no means of carrying the large amount oxygen, water, and food that would be necessary for such a long journey; and there is not known way of easing our ether ship down on the surface of another world, if we could get there.

There is no hope for the fanciful idea of reaching the moon because of insurmountable barriers to escaping the earth's gravity

There is not in sight any source of energy that would be a fair start toward that which would be necessary to get us beyond the gravitative control of the earth.