What? From where do we derive our knowledge of the natural world and universe? How do we know, for instance, that the Earth revolves around the sun and not vice versa? Are you implying that we don’t know that, or are you implying our knowledge of this fact is a divine gift?
Ok then let’s rephrase the statement to “Absent any sudden shifts in the gravitational field, 5N of force is not enough to bring a 1 kg sphere to escape velocity.” Science can prove that.
And if we can’t prove it, then we return to the question of rationality. When given an unknown, is it rational to assume anything about that unknown without verifiable evidence? I think not.
If there is no evidence either way, then it is only rational to reject any positive assertion. The reason is that negative assertions are infinitely more likely to be correct than positive assertions. As a motivating example, think of a number between 1 and 1,000. Now, which statement seems more likely to be true: “the number you thought of is 32” or “the number you thought of is not 32.” I have evidence of the number you thought of, but the negative assertion is much more likely.
Another way of thinking about it is this: each positive fact yields are near infinite number of negative facts. E.g. if you know a ball is green then you also know it’s not red and it’s not blue, etc. the converse isn’t true. When you know a negative fact, you learn very little. E.g. what else can you say after learning a ball is not blue.