The Naked Scientists Forum

Author Topic: Question of the Week - Old Version  (Read 176567 times)

another_someone

• Guest
Re: Question of the Week - Old Version
« Reply #350 on: 17/06/2006 02:48:40 »
quote:
Originally posted by chris
"Why does a mirror reverse things in the horizontal, but not the vertical axis?"

This is a question that comes up so often that I feel I should have a standard template with which to answer it.

A mirror does not reverse things.  What a mirror shows is a true image.  It is what we compare a mirror image to that is reversed.

You expect a mirror image to look like a person facing you.  The reason why a mirror image does not look like a person facing you is because the person facing you has turned around to face to.  It is the person who is facing you who is reversed.  The person who is facing you is reversed in the horizontal plane because (s)he has revolved around a vertical axis when turning around to face you.  If that person, rather than turning on their heals to face you, turned around by doing a handstand, then they would be reversed in the vertical plane and not in the horizontal plane.

George
« Last Edit: 17/06/2006 02:49:42 by another_someone »

chris

• Neilep Level Member
• Posts: 5293
• Thanked: 61 times
• The Naked Scientist
Re: Question of the Week - Old Version
« Reply #351 on: 20/06/2006 09:49:44 »
But in terms of the physics of the light waves hitting the mirror, what's happening?

Chris

"I never forget a face, but in your case I'll make an exception"
- Groucho Marx

ROBERT

• Guest
Re: Question of the Week - Old Version
« Reply #352 on: 29/06/2006 16:48:57 »
quote:
Originally posted by chris

But in terms of the physics of the light waves hitting the mirror, what's happening?

I found these sites on this subject:-
http://www.mathpages.com/home/kmath142.htm
http://www.mathpages.com/home/kmath354.htm
http://www.mathpages.com/home/kmath441.htm
« Last Edit: 30/06/2006 14:06:30 by ROBERT »

ROBERT

• Guest
Re: Question of the Week - Old Version
« Reply #353 on: 29/06/2006 16:48:57 »
quote:
Originally posted by chris

But in terms of the physics of the light waves hitting the mirror, what's happening?

I found these sites on this subject:-
http://www.mathpages.com/home/kmath142.htm
http://www.mathpages.com/home/kmath354.htm
http://www.mathpages.com/home/kmath441.htm
« Last Edit: 30/06/2006 14:06:30 by ROBERT »

rochelle

• First timers
• Posts: 1
Re: Question of the Week - Old Version
« Reply #354 on: 10/07/2006 15:49:04 »
I have a question for you scientists! Lets see if you can answer this one. Tell me why.......tell me why I've never gotten goose bumps? I do get cold, and I do get the shivers, but goose bumps have never followed after experiencing those feelings.
Hopefully someone will have an answer!
My bf's answer is that I have no soul, but thats obviously not a logical answer.

Rochelle Eloranta

Mjhavok

• Sr. Member
• Posts: 468
Re: Question of the Week - Old Version
« Reply #355 on: 15/07/2006 05:57:23 »
Goose bumps are a vestige from the days when humans were covered with hair.

When it's hot and you need to cool down, little muscles at the base of each hair relax. Your hair becomes relaxed. Your sweat glands pump out body heat in sweat. Your blood vessels get big to take more heat to the skin to get rid of it. When it's cold, the arrector muscle pulls the hair up. The duct to the sweat glands gets small to conserve heat. Our blood vessels also get small to save heat.

Hair standing up doesn't make very good insulation - we don't have enough fur for that. Humans don't have very much hair on their bodies anymore. Millions of years ago, humans probably did. And that hair standing on end helped keep people warmer. Those little muscles we have on the end of each hair still work. They still make goose bumps.

Cold is not the only thing that can cause our hair to stand on end. Fear or anger can cause the same reflex. The same is true for other mammals. You'll notice that on a cat or dog. Their fur gets bigger when they're angry or afraid.

Perhaps you have some kind of genetic abnormailty that stops you from getting goosebumps. I have heard of someone who couldn't produce tears before but never the goosebumpless disease.

Sorry
Steven
« Last Edit: 03/08/2006 05:37:41 by Mjhavok »

Mjhavok

• Sr. Member
• Posts: 468
Re: Question of the Week - Old Version
« Reply #356 on: 03/08/2006 05:40:52 »
"Why does a mirror reverse things in the horizontal, but not the vertical axis?"

I think the entry in wikipedia below explains this quite well.

http://en.wikipedia.org/wiki/Reflection_(physics)

Steven

narasimeena

• First timers
• Posts: 3
Re: Question of the Week - Old Version
« Reply #357 on: 11/09/2006 20:20:34 »
quote:
Originally posted by NakedScientist

THIS WEEK'S QUESTION : - Have a go - brownie points to the person who gets closest to the correct answer, which we'll post in a week's time.

"WHY IS THE SKY BLUE ?"

This is mainly due an effect called as Tindall Effect a property of collides. "If you shine a beam of light through a solution, the light is not effected and passes through. If you shine the beam through a colloid the small aggregates scatter the light and the material looks cloudy or milky" This causes the sky to apprea blue.
Do I get a brownie for this!

Narasi Ramachandran

narasimeena

• First timers
• Posts: 3
Re: Question of the Week - Old Version
« Reply #358 on: 11/09/2006 20:22:52 »
"WHY IS THE SKY BLUE ?"

This is mainly due an effect called as Tindall Effect a property of collides. "If you shine a beam of light through a solution, the light is not effected and passes through. If you shine the beam through a colloid the small aggregates scatter the light and the material looks cloudy or milky" This causes the sky to apprea blue.
Do I get a brownie for this!

Narasi Ramachandran

Mjhavok

• Sr. Member
• Posts: 468
Re: Question of the Week - Old Version
« Reply #359 on: 12/09/2006 00:39:55 »
Yes, this question was answered a while back. :-D

David_D

• First timers
• Posts: 4
Re: Question of the Week - Old Version
« Reply #360 on: 13/09/2006 04:03:33 »
quote:
Our ancesters had much more hair than we do. In those days, when they became cold they would get goosebumps as a skin response which would raise the hairs on their body. ...

I've heard that humans have as many hairs as a chip, but our hair is much finer.

lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
Re: Question of the Week - Old Version
« Reply #361 on: 13/09/2006 20:23:44 »
Why it's dark in the night?
(It was a serious question).
« Last Edit: 15/09/2006 13:41:58 by lightarrow »

Mjhavok

• Sr. Member
• Posts: 468
Re: Question of the Week - Old Version
« Reply #362 on: 11/10/2006 01:08:54 »
Hairy chips yuk. I prefer mine with salt and vinegar. lol.

science_guy

• Hero Member
• Posts: 701
• I'm right there... inside neilep's head!
Re: Question of the Week - Old Version
« Reply #363 on: 29/10/2006 08:07:32 »
Why it's dark in the night?
(It was a serious question).

I was taught that not as many photons reach the planet when the sun is on the other side.  The Earth's "night" side is not completely dark, because the light from the sun bounces off the moon and light shines from faraway stars.  More recently, though, light pollution from the lights in citys have made it harder to see stars.  The night sky is never completely dark.

lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
Re: Question of the Week - Old Version
« Reply #364 on: 29/10/2006 09:55:08 »
No.
The question is very simple: why in the night there is not as such ligh as in the daylight? (Or almost, or more?).
I'm not talking about complete dark, just the usual concept of dark we all have.
(The answer is not trivial)
.
« Last Edit: 29/10/2006 09:58:06 by lightarrow »

lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
Re: Question of the Week - Old Version
« Reply #365 on: 21/11/2006 09:34:21 »
No one have any idea?

Heliotrope

• Sr. Member
• Posts: 151
Re: Question of the Week - Old Version
« Reply #366 on: 28/11/2006 19:26:45 »
First of all define night. Then define dark.

If not, I'll have a go at it when you have some definitions.

lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
Re: Question of the Week - Old Version
« Reply #367 on: 29/11/2006 22:53:03 »
First of all define night. Then define dark.
If not, I'll have a go at it when you have some definitions.

Night = the sun is behind the earth.
Dark = There is not enough light to play tennis or to read a book or to make precision work...

ukmicky

• Moderator
• Neilep Level Member
• Posts: 3011
Re: Question of the Week - Old Version
« Reply #368 on: 29/11/2006 23:31:31 »
Its dark at night for us humans because we have evolved to do most of our survival work (hunting and gathering) during daylight conditions. And therefore we have not been equipt with enough light collecting cells in our eyes or specialist systems like cats have for us us to see well in low light conditions.

lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
Re: Question of the Week - Old Version
« Reply #369 on: 30/11/2006 12:35:34 »
Its dark at night for us humans because we have evolved to do most of our survival work (hunting and gathering) during daylight conditions. And therefore we have not been equipt with enough light collecting cells in our eyes or specialist systems like cats have for us us to see well in low light conditions.
Interesting consideration, Michael.
But my question was different: why it is physically dark in the night? Why there is (almost) no light, or much less light in the night than during the day?
You shoudn't give anything for granted, believe me.

kalimna

• Jr. Member
• Posts: 26
• Oh globbits!
Re: Question of the Week - Old Version
« Reply #370 on: 15/12/2006 18:20:28 »
And Im guessing that your answer has little to do with the fact  that of all the photons streaming from the sun (primary source of 'light' received by the earth), at night they are only interacting with the side facing the sun? And hence the side away from the sun is receiving only starlight (and reflected sunlight from the moon)....
Or am I missing something here?

lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
Re: Question of the Week - Old Version
« Reply #371 on: 16/12/2006 13:39:05 »
And Im guessing that your answer has little to do with the fact  that of all the photons streaming from the sun (primary source of 'light' received by the earth), at night they are only interacting with the side facing the sun? And hence the side away from the sun is receiving only starlight (and reflected sunlight from the moon)....
Or am I missing something here?

You don't miss anything, the answer has nothing to do with that.

kalimna

• Jr. Member
• Posts: 26
• Oh globbits!
Re: Question of the Week - Old Version
« Reply #372 on: 16/12/2006 15:09:49 »
Hmmm, well in that case, Im stumped! Unless the answer is one of those metaphysical philosophising answers. 'Why is it dark?' - 'Because it is not light'.......
Throw us a bone here :)

lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
Re: Question of the Week - Old Version
« Reply #373 on: 17/12/2006 14:44:40 »
Hmmm, well in that case, Im stumped! Unless the answer is one of those metaphysical philosophising answers. 'Why is it dark?' - 'Because it is not light'.......
Throw us a bone here
:)

Ok. The bonus is:
star's light.

Soul Surfer

• Neilep Level Member
• Posts: 3345
• keep banging the rocks together
Re: Question of the Week - Old Version
« Reply #374 on: 07/02/2007 10:04:05 »
Just latched on to this I think he is talking about "Olbers paradox"  If the universe was infinite every line of sight would end up on a star and it would be uniformly bright.  The fact that it is dark at night means that the universe is finite in space time or both.

It is also essential for life to work to have a heat flow so a uniform high temperature universe without light or dark bits would be boring and devoid of life.
« Last Edit: 07/02/2007 10:05:39 by Soul Surfer »

The Naked Scientists Forum

Re: Question of the Week - Old Version
« Reply #374 on: 07/02/2007 10:04:05 »