Because our mathematical understanding of the universe today is involved in our entire lives. Do you like your cell phones, TV, or the internet? Good thing we have a firm understanding of gravity and orbital mechanics, otherwise all those satellites wouldn't be working. The very same laws that are used to put objects on or around other objects in the solar system? We know exactly how the planets move in the sky, which is why the theories Kepler constructed are now called the "Laws of Kepler." Because they've been put through rigorous testing over and over again and have still been proven to be true.

You would think that even if our calculations are wrong by the tiniest bit, that the New Horizons probe on its nine year trek to Pluto traveling at 31,000mph would completely miss its target right? There's no near miss there, we're talking about 3.1 billion miles of travel. Yet the probe will make it, based on our very keen understanding of gravity and our abilities to make accurate calculations according to those laws. The very same laws that punch gaping holes in the "Hollow Earth Theory." The very same calculations that put a rover on Mars.

Therefore, if you're claiming our mathematics are bad, you're saying we could never have landed a rover on Mars.