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With regard to global warming, is there any potential for a disaster scenario where the Earth becomes uninhabitable, or that the Earth's climate is re-set to a pre-historic state where it was much warmer due to a higher CO2 content in the atmosphere? |
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It has been millions of years since the Earth's atmosphere contained as much carbon dioxide as today, and we are continuing to pump CO2 into the atmosphere as we consume hydrocarbon fuels. Since the atmospheric CO2 content is changing relatively rapidly, it is difficult to predict what effect this w... Click here for more.
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Can plants on earth photosynthesize from reflected light of the moon? |
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They could in principle, since a photon of sunlight reflected from the Moon has just as much energy as a photon coming directly from the Sun. But the Moon is so much fainter than the Sun that, in practice, trying to do photosynthesis from moonlight is not a viable option.
David Morrison
N... Click here for more.
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If you were to start from ordinary grass, how many years would it take to selectively breed wheat, rice or a similar food stuff? I know that our ancestors took thousands of years to develop modern grains, but that was because they were learning as they went along; how long would it take if you knew what you were aiming for? |
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We can get some idea from looking at recent history. The fast-growing "green revolution" crops of the mid-late twentieth century were developed within a few decades using "conventional" breeding techniques, while genetically modified (GM) crops can be engineered today within as little as a decade. T... Click here for more.
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Why did dinosuars not drive cars? Or, in a less sensationalist manner, why did competitive pressures, natural selection and a significantly longer evolutionary timeframe not facilitate the development of advanced intelligence in a class of dinosaurs which would have left some measurable trace. |
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This is a good question that highlights our limited understanding of the development of advanced intelligence. While there is some trend over time toward greater intelligence, most lineages do not travel that evolutionary route very far. In general, modern mammals and birds have larger brains (relat... Click here for more.
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Egyptologists tend to believe that the Sphynx and the pyramids were erected somewhere between 9,000 and 12,000 years ago, much earlier than we originally believed. In this case, someone could explain why their technology disapeared only to resurface only a few hundreds years ago? Also if this belief turns out to be true how to explain that a tribe that lives in the desert can be so in advance on their time? |
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Answer: I think you are misinformed on some aspects of your question. In spite of some press reports to the contrary, has been no revision recently of estimated ages for the monuments of ancient Egypt; the Giza pyramids and the sphinx are between 4000 and 4500 years old (for more information see th... Click here for more.
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Is it not possible for the Northern and Southern hemispheres of the globe to shift relative to one another, the northern hemisphere being of more mass than the southern hemisphere? Could the entire Earth have shifted on its axis in the recent past, changing the course of human migration, and thus accounting for our insufficient lack of recorded history prior to the fifth century B.C. |
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No, the Earth is stable, and scientists understand the slow (and relatively small) variations in the tilt of the Earth's spin axis over many hundreds of thousands of years in the past. Similarly, ice cores reveal the climate history of the Earth over tens of thousands of years. As to records of huma... Click here for more.
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How long have intelligent creatures existed on earth. Would creatures with the intelligence of a dog, an ape or possibly even a dolphin, have existed at the time of the dinosaurs, or is intelligent, social activity a fairly recent innovation. |
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Your question is difficult to answer for two reasons: we lack a good definition of intelligence, and it is difficult to infer intelligence (other than by measuring brain size) on extinct animals. As far as we know, the apes (including humans) and the dolphins and their relatives have the highest bra... Click here for more.
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I understand that the earths magnetic field protects our atmosphere from the solar wind and the magnetism is caused by rotations within the core that are only possible because of the ongoing geothermal activity. Will the interior of the Earth eventually cool, the magnetism fade and the atmosphere eventually be blown off by the solar wind (perhaps in a similar way to which Mars lost its atmosphere. |
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The interior temperature of the Earth today represents a balance between radioactive heat generated in the interior (primarily in the mantle) and the loss of heat from the surface. There is only a small contribution of primordial heat left over from the formation of the planet. Thus the internal tem... Click here for more.
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What were the conditions of early Earth like?
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What sort of conditions did you have in mind, and when? A planet is a big place with different conditions in different times and places. Some parts were hot and some cold, ranging from volcanic lava to ice sheets. There was an ocean but we are not sure how salty it was. There was land but it probabl... Click here for more.
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I have a question regarding the zircons which are said to be approximately 4.3 billion years old. The implication of this, from what I read, is that the Earth was cooler than what has been previously assumed in that early period. So the question I have is, doesn't this pose difficulties for the source of the current heat in the Earth's interior? My recollection is that the core is gradually cooling down, and that the current heat is from the early accretion process. So if the Earth was much cooler early on, shouldn't it be cooler now than it actually is? |
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The zircons indicate that parts of the Earth's crust had solidified by
4.3 billion years ago and not subsequently remelted. This is what one
would expect. Even when the young Earth had a much greater internal heat
source, the surface temperature would have been determined primarily by
the su... Click here for more.
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