Are there any possibility that what you sometimes see in this world is just an illusion?
2007-09-23 09:32:04 · 21 answers · asked by RICHARD M 1 in Science & Mathematics ➔ Astronomy & Space
Geoff is correct. Most answerers here are simply speculating about something they know little about.
It is true that the light from the farthest galaxies was emitted 13.2 billion years ago. However, light from the nearest star was only emitted 4 years ago.
Our Sun is an average star. It has an expected life span of 10 billion years. Other stars may live longer or shorter. If we use this as a rule of thumb, then we would say that all stars within 5 billion light years are still alive since it would take 5 billion light years for light from the farthest ones to reach us and they would today be roughly in the middle of their lives.
Let's put this 5 billion light years into perspective. The diameter of the Milky Way is 100,000 light years across. This is WELL within the 5 billion figure meaning that virtually ALL starlight emitted from stars within our galaxy are still there.
Let's go out farther- how about the entire Universe?
The visible universe is 13.7 billion light years in radius. This means that 1/3 of all the stars in the entire universe would be still alive today.
The naked human eye is able to see about 2000 stars in the sky away from city lights. Almost all of these lie between 10-100 light years away. Therefore, almost NONE of the stars visible to the naked eye could have gone out by the time their light reached us. Having a star supernova during your lifetime is a rare occurance.
Your second question... Ah, here's one for the philosophers. You have sensory inputs that create an interpretation in the mind. Is this the only possible interpretation? Or is it just the one that you decided to select?
http://www.thegreatillusion.com/secret.html
2007-09-23 17:37:24 · answer #1 · answered by Troasa 7 · 0⤊ 0⤋
The answer to your question would be YES.
I'm not sure if I would call it an illusion, as the the light do exist but the source might be dead.
Let's put it this way... If a certain star that you're looking at is about a million light years away from us, that would mean that the light that comes out from the star takes a million years to reach the earth. And now for example, if the the star would die at this moment and be 'extinguished' it would take a million years for us to know about that as the previous emitted light is still reaching us. Hope that was of any help
2007-09-23 09:51:27 · answer #2 · answered by arako 1 · 0⤊ 1⤋
These are two very separate questions.
You're quite right that stars that you can see - well with a telescope - ones you can see with the naked eye are relatively close and not that likely to have changed - but stars far away might well be gone - that doesnt mean what you're seeing isn't real. You're just looking back in time - take a glimpse at the sun - you're not seeing it as it is now - you're seeing it as it was when the light thats hitting your eye left the sun's surface - about 8 minutes earlier. Looking at the nightsky we look back hundreds or thousands of years back in time to how those stars were when the light left them - objects astronomers study on the 'edge' of the universe are most likely long extinct but because we're looking so far away, we're looking at things billions of years ago.
What we see in this world might well be an illusion but thats not optics - thats just human fallibility. If you know that you can be wrong about things you see you're rationality will serve you well.
2007-09-23 09:41:50 · answer #3 · answered by Leviathan 6 · 2⤊ 0⤋
Yes the stars you see are most likely still in existence. If you look at a particular star and see it is like our sun then you could safely assume it is still there unless it is at an extreme distance and then you probably wouldn't even see it. If the star is a blue giant there is a possibility that it has super nova-ed and the light hasn't reached us yet. There are many natural illusions light can play on our eyes however what we think we see and what is actual is no illusion.
2007-09-23 09:41:26 · answer #4 · answered by answerman 3 · 1⤊ 0⤋
We do not know for sure. What we see is the condition of the star when that light left it. The light left the star years ago, in some cases MANY MANY years ago. No, we cannot know the state of any star as it is right now due to it's great distance. A distant star may have gone nova 100 years ago, but if it is say, 300 light years distant, we will not know about it for another 200 years. Even our Sun is seen as it was about 8 minutes ago.
2007-09-23 09:38:29 · answer #5 · answered by cyswxman 7 · 0⤊ 0⤋
We don't know. If they are close neighbours (say, 6 light years away), then we know that they still existed 6 years ago. But if they are 5 million light years from us, then we can only know that they existed 5 million years ago. They may still exist, or they may have burned out - or gone supernova, or been swallowed by a black hole...
What we see is an illusion. It's not what is real, just a reflection of reality - to be precise, it's the light that reflects off what we see and into our eyes, filtered by our brain according to our experience-oriented preconceived ideas and expectations.
2007-09-23 10:06:30 · answer #6 · answered by Me 6 · 0⤊ 0⤋
The very concept of "at this moment" is not what you think it is. It is a fact of the universe that there is no consistent definition of simultaneous time for far away events, for accelerating things. But, within the local group of galaxies, and even the local super group, we can define a nearly consistent meaning for "at this moment" for the distances involved.
Also, what do you mean by "illusion"? The stars and the light from them are as real as anything else. Do you think that perhaps there is some magic guy who paints pictures inside your head?
2007-09-23 10:01:06 · answer #7 · answered by morningfoxnorth 6 · 0⤊ 0⤋
Wrong, wrong, wrong!
The stars we see with the naked eye are all within a few thousand light years of the Sun, and the lifetimes of stars are measured in BILLIONS of years. So while there may be one or two stars which have expired while their light is on its way to us, most of them are still there, unchanged in a few thousands of years. When we look at other galaxies, then a more substantial number of stars may have died, but still just a tiny fraction.
Most answrerers just don't have the foggiest idea about the distances and ages of the stars!
2007-09-23 09:42:30 · answer #8 · answered by GeoffG 7 · 1⤊ 0⤋
Most of the stars that we see in the night sky may have long since burned themselves out, you see the light that we see coming from the stars can be as old as time itself. it all has to do with the distance light can travel in one year. One light-year is equal to 9,500,000,000,000 kilometers. So we figure out how far away a star is and the light we see here today was radiated from the star miles divided by light years and that is how long ago that light left its sun to get here.
2007-09-23 09:51:06 · answer #9 · answered by sdars2 1 · 0⤊ 1⤋
The light you see from stars is as old as that star is light years away from us. It is possible that the star you are "seeing" no longer exists!
2007-09-23 10:15:05 · answer #10 · answered by Jack S 1 · 0⤊ 0⤋