Fact vs Hypothesis - What's the difference? | WikiDiff

From the initial appearance of about 2.0-1.8 mya, Europe was periodically buried under the ice sheets that began growing and receding when the first stone tools were made, so tended to appear and disappear in Europe. The fact that humans evolved and spread during an ice age has led to competing hypotheses about many aspects of humanity’s rise. Although , and there have been 17 identified episodes of advancing and retreating ice sheets, particularly in North America and northern Eurasia, the early ones were not as severe, and they did not achieve , as the diagram below shows. (Source: Wikimedia Commons)

What if we tested hypothesis'? - History Meta Stack …

Although she doesn't know it, she is basing her statement on the Critical Period Hypothesis.

PubMed - National Center for Biotechnology Information

When the total continental land mass was small or combined into a supercontinent, there was no land to divert that diffusion of warm water toward the poles, which results in currents. During those times, the global ocean became one big, calm lake, with no currents of significance. Those oceans are called today, and they would have been anoxic; the oxygenated surface waters would not have been drawn by currents to the ocean floor, and the oceans were certainly anoxic before the GOE. The interplay of those can be incredibly complex and lead to the multitude of hypotheses posited to explain those ancient events, but a leading hypothesis today is that a combination of factors, including supercontinents, variations in volcanic output, Canfield Oceans, and ice ages prevented life from gaining ecosystem dominance until the waning of the second Snowball Earth event, which was the greatest series of glaciations that Earth has yet experienced. It is known today as the , which ended about 635 mya. The study of the Cryogenian Period, which is the subject of , resulted in the term “.”

Moved Permanently. The document has moved here.

Kirschvink noted that reappeared in the geological record during the possible Snowball Earth times, after vanishing about a billion years earlier. Kirschvink noted that iron cannot increase to levels where they would create BIFs if the global ocean was oxygenated. Kirschvink proposed that the sea ice not only killed the photosynthesizers, but it also separated the ocean from the atmosphere so that the global ocean became anoxic. Iron from volcanoes on the ocean floor would build up in solution during the , and during the greenhouse phase the oceans would become oxygenated and the iron would fall out in BIFs. Other geological evidence for the vacillating icehouse and greenhouse conditions was the formation of cap carbonates over the glacial till. It was a global phenomenon; wherever the Snowball Earth till was, cap carbonates were atop them. In geological circles, deposited during the past 100 million years are considered to be of tropical origin, so scientists think that the cap carbonates reflected a tropical environment. The fact of cap carbonates atop glacial till is one of the strongest pieces of evidence for the Snowball Earth hypothesis. Kirschvink finished his paper by noting that the eon of complex life came on the heels of the Snowball Earth, and scouring the oceans of life would have presented virgin oceans for the rapid spread of life in the greenhouse periods, and this could have initiated the evolutionary novelty that led to complex life.

Vibration theory of olfaction - Wikipedia

In general, to evaluate a counterfactual, say “If it were the casethat , then …”, one replacesthe original equation for each variable with anew equation stipulating its hypothetical value,while keeping theother equations unchanged; then one computes the values for theremaining variables to see whether they make the consequent true. Thistechnique of replacing an equation with a hypothetical value set by a“surgical intervention” enables us to capture the notion ofcounterfactual dependence between variables:

Free hypothesis Essays and Papers - 123HelpMe

There is also evidence that life itself can contribute to mass extinctions. When the eventually , organisms that could not survive or thrive around oxygen (called ) . When anoxic conditions appeared, particularly when existed, the anaerobes could abound once again, and when thrived, usually arising from ocean sediments, they . Since the ocean floor had already become anoxic, the seafloor was already a dead zone, so little harm was done there. The hydrogen sulfide became lethal when it rose in the and killed off surface life and then wafted into the air and near shore. But the greatest harm to life may have been inflicted when hydrogen sulfide eventually , which could have been the final blow to an already stressed ecosphere. That may seem a fanciful scenario, but there is evidence for it. There is fossil evidence of during the Permian extinction, as well as photosynthesizing anaerobic bacteria ( and ), which could have only thrived in sulfide-rich anoxic surface waters. Peter Ward made this key evidence for his , and he has implicated hydrogen sulfide events in most major mass extinctions. An important aspect of Ward’s Medea hypothesis work is that about 1,000 PPM of carbon dioxide in the atmosphere, which might be reached in this century if we keep burning fossil fuels, may artificially induce Canfield Oceans and result in . Those are not wild-eyed doomsday speculations, but logical outcomes of current trends and , proposed by leading scientists. Hundreds of already exist on Earth, which are primarily manmade. Even if those events are “only” 10% likely to happen in the next century, that we are flirting with them at all should make us shudder, for a few reasons, one of which is the awesome damage that it would inflict on the biosphere, including humanity, and another is that it is entirely preventable with the use of technologies .

Cohesive - definition of cohesive by The Free Dictionary

Another key set of tensions are those between theorists, empiricists, and inventors. Theorists attempt to account for scientific data and ideally predict data yet to be adduced, which tests the validity of their hypotheses and theories. often produce that scientific data. Inventors create new technologies and techniques. Albert Einstein is the quintessential example of a theorist, who never performed experiments relating to his theories but accounted for experimental results and predicted them. , who performed the experiment that produced results that various scientists wrestled with for a generation before Einstein proposed his , never suspected that their experiment would lead to the theories that it did. The most important experiments in science’s history were often those producing unexpected results and were usually called failures. Einstein’s had no experimental evidence when he proposed it (it , but that was the only evidence for it when the theory was proposed), but it has been confirmed numerous times since then. Einstein expected that his theories would eventually be falsified by experimental evidence, but that the best parts of his theories would survive in the new theories.