Twinkle Twinkle...

[Indemaijinj]

[img]graemlins/offtopic.gif[/img] but:

Have you ever noticed what colour lightning usually has? I've found that it's usually neither yellow, nor blue...

[Sever]

Originally posted by Indemaijinj: [img]graemlins/offtopic.gif[/img] but: Have you ever noticed what colour lightning usually has? I've found that it's usually neither yellow, nor blue...

I recently saw a bolt of lightning up close, like, from within 200 metres. It's definately blue, unless heavy rain or other effects can change that. The front window of my car is not tinted and it was at night, so naturally, i wasn't wearing sunnies.

Sort of off topic -> I was told a long time ago, that the difference in appearance between stars and planets (naked eye) is that stars 'twinkle' and planets do not. Is this true? Is the light reflected from planets not interfered with by atmospheric effects?

[Indemaijinj]

Yeah, I have found that the most common colour of lightning bolts tends to be pink. But blue is also common.

[Legolas]

*Activating semi-scientist mode*

It's true that stars twinkle whilst planets don't.
The following information is a rough translation of the Dutch text here, and I've probably make a few mistakes. But as long as most of it is clear, I'm happy

The reason behind the twinkling is that all stars are extremely distant from the earth, which means they can be viewed as light originating from a single point in space. The atmosphere of the earth distorts these rays of light, because the atmosphere's different warm and cold layers of air make it turbulent. In addition, the athmosphere contains a lot of dust and water vapours, which make sure the fine rays from the stars are bent and broken in all sorts of ways, making the starlight dance back and forth, and in that way, twinkle.
When we look at planets, we see an entire disk, just we see the moon. Although the atmosphere influences light reflecting off of planets as well, the disc we see is much larger than the point of light coming from a star. The distortion appears much less severe, and that's why planets hardly twinkle at all.

The layers of atmosphere and the water vapours and dust in it also form the reason scientists prefer to build their telescopes in high and dry areas (the view is much more stable that way, as there's less of all of the above).

Space telescopes will never see stars twinkling, which is why they are there in the first place [img]smile.gif[/img]

So no, planet light is hardly interfered with by atmospheric effects.

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Colours of stars do depend on the heat of the stars themselves, but also on a doppler-like effect (don't know the english term for the actual phenomenon), where lightwaves appear to be closer together, or farther apart, than they were when they left the star. This causes stars moving towards us (or stars we move closer to) to appear more blue than they are, whilst stars moving away appear more red (actually, the wavelength increases is all). Our earht atmosphere also influences this.

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As for lightning bolts... I believe blue/white is a common colour for electrical discharges, although I can't say I have had any experience with lightning myself.

*Deactivating semi-scientist mode*

[Arvon]

In most cases of the visible stars you wouldn't notice the Doppler shift, sometimes known as the red shift. The relative speed is not enough to see it. You would need spectrographic equipment to note it in the visible stars. Remember that other than Andromeda all of the stars you can see are stars of the local system. Yes you people in the southern hemisphere can see the Magellian clouds.

By the way the fastest star one can see is Barnards Star, which is a Brown Dwarf.

[Leonis]

Originally posted by Legolas: ...Colours of stars do depend on the heat of the stars themselves, but also on a doppler-like effect (don't know the english term for the actual phenomenon), where lightwaves appear to be closer together, or farther apart, than they were when they left the star...

Doppler effect is the term use in English too. [img]smile.gif[/img]