<p>1) The gravity is a so powerful force that _____
2) The gravity is a force so powerful that _____</p>
<p>The second one is correct; the first one is not idiomatic.</p>
<p>A third option would be to say, “The gravity is so powerful a force that…” It’s not any better or worse than the second option; it’s just another alternative.</p>
<p>i hate english too :P</p>