Ask a physicist anything. (3)

[Wiccan_Child]

So in other words, light is invisible in space?

Basically. Light is invisible until it hits your eyes (or a camera, or whatever). It streams through space minding its own business. It's not like a laser beam in the movies, where it leaves a sparkling red glow behind it - real lasers can only be seen when they reflect off something. If someone points a laser from A to B, unless you stand in the path of the beam, you won't see it - it just zips right by you, never hitting your eye.

 

[Cabal]

Because it comes from somewhere. The light we see when we look at a green pea looks green because the pea is emitting specifically green light. That's why it's green. If there's no light coming from a particular direction, we see that as 'dark' or 'black'.

*whispers* reflecting, not emitting

A pea looks black if you seal it in a lightproof box

 

[Cabal]

Basically. Light is invisible until it hits your eyes (or a camera, or whatever). It streams through space minding its own business. It's not like a laser beam in the movies, where it leaves a sparkling red glow behind it - real lasers can only be seen when they reflect off something. If someone points a laser from A to B, unless you stand in the path of the beam, you won't see it - it just zips right by you, never hitting your eye.

Well, this is why I made the point about light that passes through a scattering medium. An intense enough laser has enough photons scattered out of it by the air that you can effectively "see" the beam, even though you're looking at photons that are technically no longer in the beam.

 

[Wiccan_Child]

*whispers* reflecting, not emitting

A pea looks black if you seal it in a lightproof box

Reflection is just emission When materials reflect things, they absorb the light, then emit it back out in mathematically elegant ways. That's why light 'slows down' in materials: it's not actually travelling slower, it's just experiencing a small (but finite) delay between emission times - during transit, it's travelling at c.

 

[Wiccan_Child]

Well, this is why I made the point about light that passes through a scattering medium. An intense enough laser has enough photons scattered out of it by the air that you can effectively "see" the beam, even though you're looking at photons that are technically no longer in the beam.

True, but, well, one step at a time Showing her 'visible' lasers is just gonna be confusing...

 

[Cabal]

Reflection is just emission When materials reflect things, they absorb the light, then emit it back out in mathematically elegant ways. That's why light 'slows down' in materials: it's not actually travelling slower, it's just experiencing a small (but finite) delay between emission times - during transit, it's travelling at c.

Yeah, as soon as I made the post I figured that this was actually going to be the case. Ho hum.

Reflection is a little clearer though.

 

[Cabal]

True, but, well, one step at a time Showing her 'visible' lasers is just gonna be confusing...

Just being pre-emptive. I figured that objection was gonna come up fairly sharpish, but perhaps I was wrong.

Also, "him", not "her".

 

[Wiccan_Child]

Just being pre-emptive. I figured that objection was gonna come up fairly sharpish, but perhaps I was wrong.

Also, "him", not "her".

Gah! All the time's I've been called a 'her'...

 

[Cabal]

Gah! All the time's I've been called a 'her'...

Pfft, everyone knows only sexy chicks are Wiccans.

I read it on Buffy or whatnot.

 

[Supreme]

No... though their antimatter counterparts, the positron and antiproton, have virtually exactly the same properties (mass, etc), and the exact opposite charge.

So while you can't get positive electrons technically, the positron is pretty much a positive electron. Hence the name

Thanks you. I was just prepared to have 14 years study of science completely disproved! I suppose that's what science does, however- it discounts widely held beliefs with such ease.

 

[Wiccan_Child]

Thanks you. I was just prepared to have 14 years study of science completely disproved! I suppose that's what science does, however- it discounts widely held beliefs with such ease.

I just hope to live to see the next big paradigm shift

 

[snackster29]

what do you think about string theory?

 

[Wiccan_Child]

what do you think about string theory?

Anything that emulates spaghetti has to be on the right lines.

 

[Steffenfield]

Okay. So in American football, when a punter kicks the ball on 4th down and if the other team doesn't get to it, they let the ball roll until it comes to a completely stop and then the punting team touches the ball to down it.

What might be the applied wind force by this entire team to collectively keep blowing the ball down to the one yard line before downing it?

Would you just have to simulate such an event or could you actually apply some number logic to solve for such a question?


Specs:

Short Circumference: 20 3/4"- 21 1/4"
Long Circumference 27 3/4 "- 28 1/2 "
Weight: 14-15 ozhttp://wiki.answers.com/Q/What_are_the_dimensions_of_a_Football#ixzz16oJYCHlz​

 

[LifeToTheFullest!]

Okay. So in American football, when a punter kicks the ball on 4th down and if the other team doesn't get to it, they let the ball roll until it comes to a completely stop and then the punting team touches the ball to down it.

What might be the applied wind force by this entire team to collectively keep blowing the ball down to the one yard line before downing it?

Would you just have to simulate such an event or could you actually apply some number logic to solve for such a question?


Specs:

Short Circumference: 20 3/4"- 21 1/4"
Long Circumference 27 3/4 "- 28 1/2 "

Weight: 14-15 oz​

I think the Raiders tried this back in '74... didn' work.

 

[Cabal]

Okay. So in American football, when a punter kicks the ball on 4th down and if the other team doesn't get to it, they let the ball roll until it comes to a completely stop and then the punting team touches the ball to down it.

What might be the applied wind force by this entire team to collectively keep blowing the ball down to the one yard line before downing it?

Would you just have to simulate such an event or could you actually apply some number logic to solve for such a question?


Specs:

Short Circumference: 20 3/4"- 21 1/4"
Long Circumference 27 3/4 "- 28 1/2 "
Weight: 14-15 ozhttp://wiki.answers.com/Q/What_are_the_dimensions_of_a_Football#ixzz16oJYCHlz​

The toughest thing would be approximating the force of the net wind acting against the ball, then the rest would be basic projectile dynamics.

In the middle of attempting to solve something else now though.

 

[Steffenfield]

Are you being serious? I need to check for videos of this! *lol*

 

[LifeToTheFullest!]

Are you being serious? I need to check for videos of this! *lol*

Nah, just funnin'. Would have been funny to watch tho'.

 

[snackster29]

lol is there any specific reason you don't accept it?

 

[Chesterton]

Nah, just funnin'. Would have been funny to watch tho'.

I actually recall seeing that. I don't rememeber what game, but I remember seeing two or three special teams guys blowing on a rolling ball to try and get it as close the goal line as possible. I remember thinking, I wonder if the rules specify that you can't utilize an electric fan.