Wednesday, April 30, 2008
This got me to thinking about the "time delay" of seeing an image (eg exploding star) and sensing other effects (eg. solar flares). I realise "time" stops at the speed of life which may effect this issue.
This delay may be irrelevant for distant stars but may have practicaal implications for our own star - the Sun.
I wonder if we can see a solar flar explode out of the sun how long would the delay be until non visual radiation effects (cosmic rays) influenced the earth and satellites?
Physicists know the speeds of energetic particles and light. The light will outrace any particles that aren't traveling at the speed of light. Check out Swift (http://www.nasa.gov/mission_pages/swift/main/index.html). It detects gamma rays using a gamma ray detector to get a bearing and then it trains a visual telescope on it to detect the light from the explosion. The remnants of the supernova will travel at lower speeds. That's why you see all those pretty nebulas like Kepler's Nova (http://www.jpl.nasa.gov/images/spitzer/p0429aw-browse.jpg). So, when they see solar flares, they know what's coming. NASA and others call solar radiation space weather (http://www.swpc.noaa.gov/today2.html). With all those expensive satellites, it's become important to track solar radiation, flares and the like.
Einstein had a nice gedanken experiment. He posited what happens if the Sun just vanished. He figured that the Earth wouldn't "know" the Sun was missing for 8 minutes. Since the speed of light is the upper limit, gravity can't go faster than the speed of light, so it would take the Earth at least that amount of time once the Sun disappeared to leave orbit and travel in a straight line, or notice the Sun was gone for that matter. So, if the Sun managed to explode somehow, it would be 8 minutes before we "cooked".
I personally would not want the Sun to explode! It would put a dampner on the whole day.
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