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Astronomy-Interesting Facts

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vseehua
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  #11 Old 25-06-2007 Default

Quote:
Originally Posted by tezuka87
I stand corrected! Yeah...should do calculations b4 claiming something.
I stand corrected means you hold that your previous claims are correct, but you seemed to admit your mistake in the phrase afterwards. So which one is correct?
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  #12 Old 26-06-2007 Default

I'm WRONG. The moon we see is the moon as it was 1.2~1.3 seconds ago.

I was just under the wrong impression that 'I stand corrected' means 'Yes, I have been corrected. I bow my head, I admit defeat.'

Or am I really under the wrong impression? If I wanted to say I am actually correct, wouldn't I say 'I am actually correct' rather than use the term 'corrected'?

Thank you, dear vseehua....please correct me if I am wrong.

Anyway, another related interesting astronomical fact...There are many stars in the sky which we can see but which really don't exist anymore...[/b]
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  #13 Old 26-06-2007 Default

Quote:
Originally Posted by tezuka87
I'm WRONG. The moon we see is the moon as it was 1.2~1.3 seconds ago.

I was just under the wrong impression that 'I stand corrected' means 'Yes, I have been corrected. I bow my head, I admit defeat.'

Or am I really under the wrong impression? If I wanted to say I am actually correct, wouldn't I say 'I am actually correct' rather than use the term 'corrected'?

Thank you, dear vseehua....please correct me if I am wrong.

Anyway, another related interesting astronomical fact...There are many stars in the sky which we can see but which really don't exist anymore...[/b]
As far as i know, the term "i stand corrected" literally means my points are corrected and i refuse go budge from it. That is what i can derive from the numerous time that i had encountered this phrase...

The fact is based on the fact that the light from the stars required time to travel to our eyes. In fact, the time that it takes to travel to our eyes are so long that they are can take millions if not billions of years to do so. Since the speed of light is determined to be about 300,000 m/s you can imagine that the size of the universe if indeed very epic in itself.

The light from the stars that you are looking now actually have been emitted in the past, as such, you are looking at the history of the star, not the present state of it ;)
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  #14 Old 27-06-2007 Default

Quote:
Originally Posted by youngyew
Quote:
Originally Posted by tezuka87
If the sun blots out it would take 8 minutes for us to find out..this is cos it takes 8 minutes for the sun's light to reach earth. This also means that the sun we see is actually the sun as it was 8 minutes ago.

Similarly, the moon we see is the moon as it was 1 minute ago.
The light from moon should be about 1.2 to 1.3 seconds ago, as the moon's distance from earth is 360,000 km to 400,000 km while the speed of light is about 300,000 km/s.

Anyway, it's interesting to think about the speed of light in terms of interstellar distances. There's an interesting paragraph in Bill Bryson's book "A Short History of Nearly Everything" about Drake equation:

"... Unfortunately, space being spacious, the average distance between any two of these civilizations is reckoned to be at least two hundred light years, which is a great deal more than merely saying it makes it sound. It means, for a start, that even if these beings know we are here and are somehow able to see us in their telescopes, they're watching light that left Earth two hundred years ago. So they're not seeing you and me. They're watching the French Revolution and Thomas Jefferson and people in silk stockings and powdered wigs - people who don't know what an atom is, or a gene, and who make their electricity by rubbing a rod of amber with a piece of fur and think that's quite a trick. Any message we receive from these observers is likely to begin 'Dear Sire', and congratulate us on the handsomeness of our horses and our mastery of whale oil. Two hundred light years is a distance so far beyond us as to be, well, just beyond us."
its possible for an object to travel faster than the speed of light.
care to give me your opinion?
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  #15 Old 28-06-2007 Default

I thought it's impossible to travel beyond the speed of light?
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  #16 Old 04-07-2007 Default

In Einstein's frameworks, nothing can travel faster than light. However, nobody really says that nothing exists outside Einstein's framework, so who knows, one day it might be possible?

But of course I am not qualified to talk about this thing, just some random ramblings here.
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  #17 Old 15-07-2007 Default

Did you all ever heard of Cerenkov Radiation? I don't really understand its meaning...but i guess it has something to do with the phenomenon when a particle travel faster than the speed of light....means it should be possible for an object to travel faster than light!

Wanna ask something, light beam has the speed of 300000 km/s....
Do you think the speed of light beam will increase when we shoot the light beam in a constant velocity moving vehicle?

Let say if the velocity of the vehicle is 200km/s....will the speed of light beam shot from the vehicle increase to 300200 km/s ?
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  #18 Old 15-07-2007 Default

Quote:
Originally Posted by Al-Bert
Did you all ever heard of Cerenkov Radiation? I don't really understand its meaning...but i guess it has something to do with the phenomenon when a particle travel faster than the speed of light....means it should be possible for an object to travel faster than light!

Wanna ask something, light beam has the speed of 300000 km/s....
Do you think the speed of light beam will increase when we shoot the light beam in a constant velocity moving vehicle?

Let say if the velocity of the vehicle is 200km/s....will the speed of light beam shot from the vehicle increase to 300200 km/s ?
I can't comment much about the cerenkov radiation.

For your question about the light beam, no, regardless of the velocity of the vehicle, the velocity measured from the car is still c, 299,792.458 km/s. This counter-intuitive result holds true in our observable universe, and it in fact forms the basis of the theory of special relativity by Einstein. Read more here:

http://en.wikipedia.org/wiki/Speed_of_light
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  #19 Old 27-05-2008 Default

Harlo, feel like reviving this thread...a bit...

Cerenkov radiation is the electromagnetic radiation emitted when a (charged) particle travels faster in a medium than the speed of light in the same medium...

I guess when people say nothing can travel faster than the speed of light, they mean the speed of light in a VACUUM...
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  #20 Old 28-05-2008 Default

I could comprehend why Sun could "burn" without oxygen gas...

However, I have no idea why something would get burned when it travels close to the Sun? ( There's no any kind of gas particle exist in outerspace )
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