I'm reading a thoroughly ridiculous book, Calling Captain Future. It was written as a pulp serial in the 1940's, and is set in a very futuristic 1990. In addition to its many rather entertaining literary faults, it makes several errors about space and space travel. It made me curious about how much scientists knew when it was written in 1940.
First, Earth is described as a "green planet" when viewed from space, not the blue-and-white orb we have seen so many times by 2021.
When did we first see our planet from space?
Second, the protagonist's spaceship The Comet makes a journey from Venus to Mars in the time of a short conversation, approximately five minutes. https://nineplanets.org/distance-between-planets/ lists the distance between Venus and Mars as 0.8 AU, or 74,402,987 miles. I'm a novice to be sure, but a ship would have to travel 133% the speed of light in order to make that journey, wouldn't it?
$$74,402,987*(60/5) = 892,835,844 mph$$ $$892,835,844 /(60*60) = 248,009 mps$$
I read that the speed of light has been known since the 17th Century (link). Today, 80 years after the book was published, we certainly aren't very close to making anything as bulky as a spaceship travel at anything approaching the speed of light. But did the 1940s-era scientists have reason to believe that by 1990, we might be able to do this?
What was known about the likelihood traveling beyond light-speed in 1940?