The MIS data also matches the astronomical data of Milankovitch cycles of orbital forcing or the effects of variations in insolation caused by cyclical slight changes in the tilt of the earth's axis of rotation – the "orbital theory". Indeed, that the MIS data matched Milankovich's theory, which he formed during World War I, so well was a key factor in the theory gaining general acceptance, despite some remaining problems at certain points, notably the so-called 100,000-year problem. For relatively recent periods data from radiocarbon dating and dendrochronology also support the MIS data. The sediments also acquire depositional remanent magnetization which allows them to be correlated with earth's geomagnetic reversals. For older core samples, individual annual depositions cannot usually be distinguished, and dating is taken from the geomagnetic information in the cores. Other information, especially as to the ratios of gases such as carbon dioxide in the atmosphere, is provided by analysis of ice cores.