Week 4 DQs

DQ1 - Do you think that a universe with a definite beginning in time some 14 billion or so years ago , has any important philosophical implication ? Explain

Yes , to think of a universe with a definite beginning in time begs the question : but what came before ' It places an implicit demand that something greater and bigger exist that is both external to and greater than the universe . For , if the universe had an exact beginning , it implies that there was nothing material before it , since everything material that exists now is part and

parcel of the universe . Hence since it exists now , the universe must have arisen from nothingness . But what or who could give rise to such an entity from nothing ? Different religions and philosophers would answer differently - some would say God , some would say any transcendent being that is not encompassed by the limits of the universe - yet it all boils down to positing the existence of something omnipotent and transcendent

DQ2 - The evidence for black holes at the center of galaxies is strong However , it is very difficult to prove absolutely that they exist because the black holes do not emit light . We can only infer their existence from their powerful gravitational influences on surrounding matter . How compelling do you find the evidence ? Do you think astronomers have proved the case for black holes beyond a reasonable doubt

Even though theories and evidence may point to the existence of black holes , they do not present an entirely convincing argument . For one thing , the cause of powerful gravitational influences on surrounding matter ' may not necessarily be black holes . They can actually be caused by dark matter in the universe . On the other hand , however , though black holes may not emit visible light , theories predict that they in fact emit other types of electromagnetic waves with very short wavelengths such as x-rays and gamma rays . The cause of this emission is due to the high gravitational force at the event horizon of the black hole . As interstellar matter is sucked by the black hole , the very high gravitational force accelerates the matters , causing it to heat up to extremely high temperatures , thus emitting gamma rays and x-rays . Still even with this evidence , it is still too early to say whether black holes exist or not

DQ3 - The end of time . Just as there was a big bang , astronomers say , there will be a big crunch . Some people speculate that the universe will experience a re-birth and eventually a new big bang . Do you believe on this ? Discuss some ideas on how this may happen

For big crunch ' to happen , there needs to be a critical mass of dark matter in the universe . This means that at a certain point , the gravitational force exerted by dark matter in the universe must be enough to pull the other matter in the universe together . As they come closer and closer together , gravitational force increases , accelerating the rate of contraction . Eventually , the gravitational force...