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Reading Comprehension for Grade 4

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  Reading comprehension for grade 4 involves understanding longer and more detailed texts. Students analyze the text for main ideas, supporting details, cause and effect, and inferences. Here’s an example: Passage: The sun was setting as Mia and her brother, Alex, reached the top of the hill. They had been hiking all afternoon, and now they could see the entire valley below. The trees looked like tiny green dots, and the river sparkled in the fading sunlight. “It was worth the climb,” said Alex, smiling. Mia nodded, feeling proud of their effort. They unpacked their sandwiches and watched as the sky turned shades of orange and pink. Questions: Why were Mia and Alex hiking? What did they see when they reached the top of the hill? How did Alex feel about the hike? What happened to the sky as the sun set? What does the word “sparkled” mean in the passage? This level encourages students to think critically and expand their vocabulary. Would you like another example or a specific topic ...
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IS TIME TIME TRAVEL POSSIBLE??? - ASKS UTKARSH SHINDE


 All of us, of course, time-travel forwards at the rate of one second per second.


The Theory of Relativity* tells us that it is also possible to time-travel forward at different rates. For example, time dilation*, a consequence of the Theory of Relativity (for particles that move almost with the speed of light) or the fact that time slows down in the presence of strong gravitational field, are real, verified facts. Thus, continuous forward time-travel is perfectly OK. (By continuous, mean there should be no gaps in the accounting of time.)


What is problematic is travelling backwards in timeand this is what usually is meant by `time-travel' in popular movies and books. This is not allowed by laws of physics as we know them now, since these laws have "causality" built into them.


Causality means that the cause happens before the effect, and not vice versaFor example, a glass breaks after it falls downit does not fall down after it breaks; the falling comes first. Thus, causality is tightly woven into the arrow of time that points in only one directionAll our millions of observations everyday agree with this. There has not been a single violation.


Does this mean backward time-travel is 'impossible'? Well, a single verified instance of backward time travel will force us to change our theories, but that looks extremely extremely unlikely.


Science fiction is full of backward time-travel. Good sci-fi ensures that there is no logical contradiction: nothing that will change the future is disturbed. While I love these, what all of them miss is that if something from future were to land suddenly, the Law of Conservation of Energy* would be violated. And we have not seen this yet.


The only way to get around this will be saying that all the backward time-travel has been hidden by some strange coincidence. And that is not a good excuse. You might as well have an invisible unicorn in your house.


So, backward time travel is the stuff of science fiction; impossible according to all our observations and laws of physics so far. But suppose laws of physics have missed something? That's speculation till we observe a single verified incident.



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