Cuesta College, San Luis Obispo, CA
Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.
(The following question was asked prior to the lecture on the finite speed of light and lookback time.)
How would it be possible for you to see a star in tonight's sky that may have already died a long time ago? Briefly explain your answer. (Graded for completion.)
The following are all of the student responses to this question, verbatim and unedited.
"You're crazy and seeing things"
"..."
"the gases are still around"
"its many many light years away"
"thats how it works"
"the sun is behind the star"
"It takes many lightyears for the image to reach us."
"Yes, because if it's many lightyears away, it could take a long time for light to catch up to us"
"space-time stretches photons giving them longer wavelengths...also known as redshift duh!"
"The light has just reached earth, as it takes time for light to travel just like anything else."
"It can be so far away that the speed of light is too slow, causing us to have a delay on seeing the star die."
"it's possible to see the nebula that if formed into"
"Light takes a long time to reach earth from distant stars, it is not instant."
"the light is still traveling even after it's stopped being produced"
"the nova hasn't reached us yet"
"Since it is so many light years away, it would take that many years to see that the light has stopped."
"Were on a different time schedule than space."
"I have no idea."
"still burning"
"because the star is so far away that it takes a long time for the traveling light to reach us"
"The light source is out, but because it's so far away, the last of the light hasn't reached us yet."
"star is really far away"
"using a high powered telescope"
"not to positive"
"because we are x ammount of lightyears away from that star and it takes a long time for that light to reach the earth."
"it takes a very long time for its light to reach Earth"
"light still comin"
"So far away that the light we see is from when it was still alive"
"Light travels at a certain speed to reach us."
"if its like a million light years away, the light is still traveling even though the star has died"
"It would take a long time for the absorption lines to come into view."
"the energy blast"
"I DONT KNOW"
"Because of the lightyears."
"Light is still traveling"
"The time in which it takes for the light from the start to reach the Earth could take longer than the stars lifetime."
"No idea???"
"dunno....."
"white dwarf"
"It would have to have died at a distance, for it takes time for light to reach earth"
"because light can only travel a certain speed so it takes a while for it to get to earth"
"yes, because of the speed the visual light travels."
"because it takes a long time for light to travel"
"i dont have a clue :("
"the white dwarf"
"When the star is really far away the light takes so long to get to us that even if the star is dead, light from the star can still be coming towards us many years later."
"magic"
"they are many light years away so the light that star gave of would take a long time to die out."
"Emitted gasses from a companion star"
"Because the stars themselves are millions of lightyears away meaning it takes a ridiculous amount of time for the phonons to reach us. so those photons were sent before the star died and we are just now recieving them (almost like a letter from a person before they go to battle and that can be read even if he dies before it arrived elsewhere)."
"Its so far away that the light is still traveling to us from when it was still alive. We live in a really big area :)"
"it takes thousands of lights years for the light of the star to reach us so even if it died its lights will still reach us thousands of years after it died."
"Even though the star already died, its was so far away that its light is finally reaching Earth."
"If a star is many light years away it will take the light from that star many years to reach Earth."
"im lost"
"Light takes time to reach earth, therefore we are seeing the past rather than the present of the distant night sky
because it becomes either a white dwarf, neutron star or black hole"
"i have no idea"
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