- Attachments : Thinking
------------ There are 25,280,000,000,000 miles in a single lightyear
------------ Alpha Centauri is 5,880,000,000,000 miles away
------------- Time = Distance / Velocity
------------- Time light has traveled = 25.28 *10^12 miles / 6.7 * 10^8 miles / hour
------------- Time = 37,000 hours for light to reach us
------------ There are 8,760 hours in a year
------------ Time light has traveled = 3.7*10^4 hours / 8.7*10^3 hours / year = 4.4 lightyears
- That is how far the closest starlight has to travel and how long it takes to reach us even when traveling at 670 million miles per hour.
- When we are looking at the star Alpha Centauri we are viewing what it looked like nearly 4 ½ years ago. It is 4 ½ years older now. It could have blown up and disappeared and we would not know about it for another 4 ½ years. ( although this explosion is unlikely) It turns out the Universe is always giving us old information.
- You hear that expression that the stars of the heaven could have gone supernova and not even be there anymore. This is unlikely. The stars we can see with the naked eye are likely within 3,000 lightyears distance. These are the stars in our neighborhood of the Milky Way Galaxy. So, all these stars could not have lived more than 3,000 additional years. Stars live for millions and billions of years so 3 thousand is merely a blink of the eye in star time.
- You can only see about 6,000 stars in the night sky. But, who’s counting? It is very unlikely that one of these will have gone supernova exactly 3,000 years ago, or whatever fewer lightyears it is away from us. The most likely supernova we are likely to have in our Galaxy is Eta Carinae ( just guessing) and it is 250,000,000 lightyears away. It would have had to have exploded 250,000,000 years ago in order for us to see it now. ( See Reiews #1346, #775, #49, and #832 to learn more about Eta Carinae.)
- Astronomers have discovered over 1,000 Quasars that are billions of lightyears away. They are extremely bright lights created by active Blackholes at the cores of massive galaxies. These astronomers are most assuredly looking at ghosts. Quasars only occurred in the early Universe. The Universe has since expanded so much that more recent Quasars don not exist anymore. The light we are seeing is information about a long bygone Universe.
- We have read about massive stars collapsing into a Blackhole. We visualize it happening in our minds. Artist depict renderings and computer simulations of what it would look like. Our imagination can see it but in fact we could never see such an event. A Blackhole is so dense with so much gravity that light never escapes. Its gravity bends space-time back on itself. If somehow we were viewing this event from outside it would simply look like time was slowing to a stop. The event becomes frozen in time. It just stops. There is nothing more ever to be seen.
- The Universe is expanding at 47,000 miles per hour for every million lightyears distance. Therefore the galaxies are no longer located where we see them. And, of course, by now they may look much different. There may even have been mergers and collisions by now. They may even be so far away by now that the light will never reach us. We may never know what these galaxies look like today.
- We create the Universe in our heads. It is similar to how we create “ rainbows’ in our heads. Rainbows are not objects that really exist. They are not actually there. If some sees a rainbow from a different location, she is seeing a different rainbow from the one you are seeing. Your eyes witness a specific light beam that gets bent in the rain drops and enters only your eyes. If no one was looking the rainbow would not be there. In fact, throughout history rainbows did not exist until animals evolved with color vision. Your eyes and your eyes alone personally create the colors you see. Each rainbow is personally yours.
- Rainbows do not have shadows or reflections. If you see a rainbow reflected of the still surface of a lake it is a different rainbow because it is being created by different beams of light. Rainbows are not real, we make them real in our heads.
- So it is with much of the Universe. It is as we perceive it. The finite speed of light requires that we use the laws of physics to learn what “is”. For sure, it “ is” not what we “ see”. A good student will be able to “ see” with “ understanding”. You have to learn to see what is. An announcement will be made shortly, stay tuned.
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