Answer:
b. flat rotation curves in spiral galaxies
Explanation:
Dark matter accounts for majority of the matter in the universe (about 85%). It is considered to be composed of subatomic particles which are yet to be discovered. Dark matter cannot be observed because it does not emit light that can be detected. Only its gravitational effect is visible.
Astronomers when calculated the mass of the visible matter and tried to account for the observed speed of stars in the galaxy, there was a mismatch. To understand what caused this mismatch, astronomers gave name to the invisible matter as the Dark Matter.
The expected velocity of stars should decrease away from the near the center of the galaxy but a constant velocity of stars was observed that is a relatively flat rotation curve was obtained.
Thus, flat rotation curves in spiral galaxies in an evidence of Dark Matter.
In general, physical weathering from temperature changes is most common on the shorelines, because waves are able to take down rocks that have been weathers. They would be least noticeable inland, in desert areas with little forestation.
<span />
is it oceans or the actual continent/country
The best and most correct answer among the choices provided by your question is the third choice.
The oceanic trenches<span> are hemispheric-scale long but narrow topographic depressions of the sea floor. They are also the deepest parts of the </span>ocean<span> floor.</span>
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Answer:
For a geographer Map is the most important tool
Explanation:
Apart from the above geographers rely on various tools and techniques which are both Qualitative and Quantitative. Such as the Primary and secondary sources of data like surveys, questionnaires, and journals, etc. Apart from this use of satellite data to generate a comparative analysis of objects and there processing in terms of software i.e the GIS, GPS that store and breaks the data into an understandable format. Use of mental maps to understand the spatial construct of humans and the use of Aerial photography to help the geographers do an in-depth analysis of the landscape. Tools like the map which is again divided into various types such as the topological maps, hydrological maps, physiological, political and many more are essential tools of any geographer.
