Physics P1

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Ways in measuring distances to stars:

Parallax - when an object appears to move when you look at is from different places. This is used for stars whithin a certain parameter, they are classsed as 'nearby stars'. 

Measuring the brightness of stars - detect the amount of photons in the light being recieved, how high is the concentration of the light. However, light pollution from street lights  and other man-made sources brightens of the night sky caused other man-made sources, which disrupts the natural cycles of light in the atomsphere and inhibits the observation of stars and planets.

Red shift is used. The wavelengths seem to look red when the star is further away. This shows that distant galaxies are moving away from us, and that the further away a galaxy is, the faster it's moving away.

Doppler effect: It’s the apparent change of the frequency of a wave caused by relative motion between the source of the wave and the observer.

Measuring the amount of radiation emitted by a star - stars emit radiation in forms shown in the electromagnetic spectrum, it is mainly visual light.

Continental Drift:

Alfred Wegener hypothesized that 300 million years ago, there was a 'supercontinent' called Pangea - all the continents were joined up, one big continent. Over time, the small continents withinn Pangea moved apart to the positions on the Earth that they are on now. According to his theory, the continents are still moving around the Earth. To support his idea, he said that fossils of specific animals and plants had been found on the opposite side of the Ocean, where they wouldn't have lived due to the difference in climate and resources. Also, the coastlines of Africa and South America looked as if they were part of a puzzle, they matched perfectly.

Unfortunately when Wegener went to other scientists (geologists) to add confidence to his theory, the idea was rejected. This is because some of his evidence was opposed and disproved, they explained that fossils on different sides of the Atlantic Ocean could have been due to land bridges. As a results of land bridges, animals were able to travel to the other side of the Ocean and when they would die, their fossils would remain in the same continent. Also, Wegener had no reasonable explanation for how he thought that the continents were moving. Lastly, as Wegener was actually a meteorologist his ideas weren't very important to the geologists as he didn't know exactly what his theory was.

Eventually, evidence for continental drift was found during world war 2 after Wegener had died. It happened whem soldiers…


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