Smoller and Temple integrate shock waves into Einstein's general relativity. This produces a universe that "looks essentially identical to the aftermath of the big bang" according to cosmologists Barnes and Lewis. They explain that Smoller and Temple's version is distinguished from the big bang only by there being a shockwave at the leading edge of an explosion - one that, for Smoller and Temple's model, must be beyond the observable universe. However, Barnes and Lewis do not support shockwave cosmology because they see it as not testable; they point out that there is no explosion in the standard theory of the Big Bang.