Gerald Lawrence Schroeder is an Israeli-American physicist, author, lecturer and teacher at the College of Jewish Studies Aish HaTorah’s Discovery Seminar. Schroeder does indeed have a genuine science background and may have been a real scientist at some point, but he is also a creationist, and seems to have spent most of the last 40 years doing apologetics, such as investigating “the confluence of science and Torah” and constructing elaborate, tortured ad hoc explanations to get the apparent age of the universe to fit with the literal Biblical six-day account of creation; in particular Schroeder draws on relativity to reconcile a six-day creation as described in Genesis with the scientific evidence that the world is billions of years old using the idea that the perceived flow of time for a given event in an expanding universe varies with the observer’s perspective of that event. As such, it isn’t really young-earth creationism in the traditional sense, but it is still serious nonsense (there is a comprehensive explanation of his silliness here; Schroeder’s non-response to being refuted is discussed here), and still creationism. Although he attempts to reconcile Genesis and science when it comes to the age of the universe, he simply rejects science in favor of the Bible – including the Bible Code – when it comes to all other matters (these areas are, after all, beyond his area of competence anyways, and you can always reject the science of things you don’t understand). Schroeder is a signatory to the Discovery Institute’s silly petition A Scientific Dissent From Darwinism (Schroeder has no expertise on anything related to evolution), and currently seems to be considered something of an authority in the Intelligent Design movement, being invited to give seemingly scientifically informed talks by various denialist groups across the US.
His books include titles like The Science of God: The Convergence of Scientific and Biblical Wisdom (reviewed e.g. here) a book that has generated research such as Andrew Mark Sibley “A Photon Reference Frame and Distant Starlight: Analyzing Ideas from Gerald L. Schroeder’s The Science of God” published in the venerable Answers Research Journal, Answers in Genesis's house journal. Schroeder’s most famous book is presumably The Hidden Face of God, however, since it apparently impressed ex-atheist Antony Flew during his conversion process; it is reviewed here (“[n]o one should read this tiresome book for any serious purpose other than to find examples of popular science-abuse”). Given Schroeder’s background, the most striking characteristic, apart from its New Age-style handwavings, is perhaps the many misinterpretations of and obvious errors in the physics he describes.
Diagnosis: At least he is pretty clear that what he is doing is fundie dogmatism: start with the conclusion you like, try to make the data fit and just reject whatever doesn’t. But Schroeder is also something of a star in the creationist movement, and seems to spend quite a bit of effort promoting denialism. He must accordingly be considered a moderate threat to civilization and human flourishing.