Y'all are a bunch of wankers!

Photons

A star a bazillion miles away send photons zipping out in every direction, and no matter where you are, some of them hit your eye (e.g. if you move an inch over you're not going to be in an "uncovered" area).

Think about that.
Permalink DF 
March 6th, 2007 5:20pm
I think the republicans created photons so they can convertly be used by terrorists and then later to attack them.
Permalink Bot Berlin 
March 6th, 2007 5:23pm
The universe must be bound then. Or each star must produce an infinite amount of photons per second.
Permalink Send private email strawberry snowflake 
March 6th, 2007 5:37pm
" Or each star must produce an infinite amount of photons per second"

Is this something that Al Gore and the democrats are pushing.  Damn global warming.
Permalink Bot Berlin 
March 6th, 2007 5:41pm
Good weed up there in Canada?
Permalink zed 
March 6th, 2007 5:47pm
>The universe must be bound then. Or each star must produce an infinite amount of photons per second.

I don't know much about astrophysics, or even photons for that matter, but really think of the number of photons to cover that 3D surface area at such a distance, continuously.
Permalink DF 
March 6th, 2007 5:55pm
There is a precise mathematical term for that number of photons. It is "quite a lot".
Permalink Send private email bon vivant 
March 6th, 2007 5:57pm
Well, I do think it's more like "one Gazillion!" -- but even that is WAY below "Infinite".
Permalink SaveTheHubble 
March 6th, 2007 6:01pm
This is why it's such a big deal whether neutrinos have mass or not...

WTF?!  They do have mass?  I haven't been keeping up...  Wow,
at least 0.05 eV, but no more than 0.3 eV.
Permalink Send private email Ward 
March 6th, 2007 6:57pm
This is proof that people really don't comprehend large orders of magnitude.  10^26 just doesn't help w/ day-to-day comparisons...

>>> The Sun's luminosity is 3.83e26 W

>>> So let's say that 40% of the Sun's energy is emitted at a wavelength of 550 nm (which is pretty reasonable).

Not sure where they got this, but probably close enough.

>>> The energy of a 550 nm photon is E=hc/lambda=3.6e-19 J.

>>> So the number of photons emitted at 550 nm is roughly: 3.82e26 J/s * 0.4 / (3.6e-19 J/photon)= 4.2e44 photons/s.


Here's a better rough estimate:

The Sun generates about 4x10E26 Watts.

The surface area of our telescope is 0.03141 square metres.

200 light years.  (work out the area yourself A = 4*pi*r*r)

Energy in a photon = 3.97x10E-19 Joules  (800nm)
Photons in a Joule = 2.52x10E18
100 Watts = 2.52x10E20 photons per second.

Jiggle the sums, and the number of photons that reach my telescope is about 700,000 photons per second.
Permalink Send private email Ward 
March 6th, 2007 7:20pm
How many if your telescope is 10 light years away from the star?
Permalink Send private email strawberry snowflake 
March 6th, 2007 7:23pm
And to think, all those photons and we STILL have to use photomultipliers in space telescopes...
Permalink Send private email no label 
March 6th, 2007 8:20pm
There might be 700,000 of them per second, but a photon is *really* small.
Permalink Send private email Flasher T 
March 7th, 2007 3:02am
interesting thought.
Permalink $-- 
March 7th, 2007 4:16am
it's amazing that flickr can store that many, when you think about it.
Permalink $-- 
March 7th, 2007 4:16am
Ah, you see, the trick is that Flickr stores each photon only once and then just uses it for different pictures!
Permalink Send private email Flasher T 
March 7th, 2007 4:50am
Is that a second's worth of photons in your pants, or are you just happy to see me?
Permalink Send private email JoC 
March 7th, 2007 10:36am
We should outlaw photons.. those sneaky bastards are always up to no good.
Permalink Send private email Mikael Bergkvist 
March 7th, 2007 2:36pm
So the further you get from something, the more limited the precision of imaging could be.

e.g. If we had the most amazing CMOS-sensor ever, and it was 10 gazillipixels, but we fed it through the aforementioned lens super zoomed in to some far off star, we aren't going to see surface details because there just aren't enough photons coming in.
Permalink DF 
March 7th, 2007 2:47pm
hence my conclusion that if

> no matter where you are, some of them [photons] hit your eye

is true, then either stars produce infinitely dense beams of light, or the universe is bound (aka, you can never move out of a beam of light from a star ... the finite density of the spread is greater than the size of the universe).
Permalink Send private email strawberry snowflake 
March 7th, 2007 3:20pm
>>no matter where you are, some of them [photons] hit your eye

That doesn't require infinite density of photons. It just requires infinite time between photons hitting your eye.

In other words, given finite density, given random emission direction, a photon from a star will eventually come by and hit your eye, you just might have to wait a while.
Permalink bob's your uncle 
March 7th, 2007 4:13pm
ok good point. I read the OP as saying that you could move over an inch and there would be light there from said star. Ie, that upon moving over one didn't need to bring popcorn, some beef jerky and wait an *infinite* amount of time to see the star.

But yes, that works too.
Permalink Send private email strawberry snowflake 
March 7th, 2007 7:12pm

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