"You can test gravity" ->
theodosius dobzhansky did a test in the 70s that successfully proved speciation using fruit flies. The test is repeatable. You can go out and buy fruit flies, set up the test the same way, and watch them evolve right before your eyes.
"you can figure out what causes it" ->
random genetic variation with natural selection as the selective pressure.
"You saw how the system began and ended, and thus you know for a fact that gravity did its thing" ->
mountains of evidence in the fossil record.
Slashdot Mirror
Are you seriously saying the comments on reddit are better? The comments are why I left reddit and came here.
Sure. Here ya go: http://en.wikipedia.org/wiki/List_of_transitional_fossils
"You can test gravity" -> theodosius dobzhansky did a test in the 70s that successfully proved speciation using fruit flies. The test is repeatable. You can go out and buy fruit flies, set up the test the same way, and watch them evolve right before your eyes. "you can figure out what causes it" -> random genetic variation with natural selection as the selective pressure. "You saw how the system began and ended, and thus you know for a fact that gravity did its thing" -> mountains of evidence in the fossil record.