I am wondering just how far the eye can see. That isn't an easy question to answer, it depends on a lot of things. This morning, my eyes can't see very far. No, it ain't my eye's fault, it is really foggy and at the big airport north of Houston (Houston Intercontinental) the visibility was 0.13 miles. I have seen it worse, but it sure does limit the distance I can see. So, the main thing that determines how far we can see is the conditions. So, let us assume that the conditions are perfectly clear and it is at night. Now look up. How far can you see?
What limits how far you can see is the speed of light. Yep, there are things so far out there that their light will never reach earth. A light-year, as you all know, is the distance that light travels at a speed of 186,282.4 miles per second from your one birthday to your next. (unless it is leap year - grin). That is a long, long, long way. But the universe is a big, big, big place. Let me try to put the distances in perspective.
The nearest "bright" star that we can see is Sirius. There are seven closer stars but Sirius is the closest one that can be easily seen by the naked eye. The light from Sirius is only 8.7 years old when it reaches us, about the age of a third grader. The light from Capella is 43 years old, matching a middle aged person. Mizar (the middle star of the Big Dipper's handle) is 78 years old. That is older than this old man. The upper front star in the Dipper's bowl is Dubhe and its light is older than the oldest person I know, it is124 years old. The bright star Rigel is 860 light-years away, and if you look to the northwest just after the sun sets you can see a fuzzy oval that is the most distant object the naked eye can see. What is it? It is the Andromeda galaxy. It is 2.54 million light-years away. The light from this galaxy when it reaches us started its trip to us before there were any humans on Earth. Now, don't complain about how far away a store or a friend or a place you want to drive to is, and have a great day, you hear?
In the last year or so, when i get tired, my eyes don't see like they used to. Well, when i'm reading anyway.
ReplyDeleteNeither do mine.
Deletei don't understand how the light from Sirius can only be 8.7 yrs old when mankind has been seeing it for thousands of years, and it was there even before there were people to observe it. The universe is really mind boggling, isn't it.
ReplyDeleteI should change that to read that mankind has probably been viewing Sirius for hundreds of thousands of years. I'm not remembering the timeline so well this morning.
DeleteIt takes the light from Sirius 8.7 years from the time it was emitted until it reaches us on Earth. In other words, we are seeing now what Sirius looked like 8.7 years ago if we were there close to the star. Does that make any sense?
DeleteIt makes perfect sense now. I'm not sure how I was reading it but I wasn't understanding it very well. Now I do, and thanks for the clarification.
DeleteNo problem. Sometimes I have problems saying things the way I am thinking them.
DeleteIt is getting to the point I can no longer see where BillyBob hits his golf drives to. I heard that some guy named Dizzy finds trees with his RV instead of his eyes. I have been known to find a tree or two with my outside internet antenna. We are all falling apart.
ReplyDeleteI don't know about you, but I sure am falling apart. By the time I die there may not be enough of me left to bury. . . Anyway, if there are any trees on the way to heaven or below, I hope I don't swipe a tree on the way.
Deletewell, dang, Dizzy.. just getting caught up with you ... what a week you did have! glad you weren't hurt ... and my eyes are covered in vaseline sometimes ... I don't like this getting old business. I really don't. always something ... hiss
ReplyDeletewas the Sirius radio named after Sirius, y'think?
We got a Sirius radio and it probably was named after the bright star.
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