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  #701  
Old 16.08.2008, 16:44
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Re: Ask a Scientist

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When the Big Bang happened and by the time the plasma condensed, all the mass of the entire universe was concentrated in an incredibly small space.

Surely this would have caused a black hole?
Well, it's gravity that causes a black hole. Gravity is a failry weak force (not to be confused with the "weak force" ). The initial force imparted on the matter by the big bang was probably sufficient to overcome the gravitational force.
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  #702  
Old 16.08.2008, 17:57
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Re: Ask a Scientist

This is a great thread, but only read the first 9 pages. Did a quick search and i dont think this question has been asked/answered before:

Why, when you are parallel to a car/bike on a road, do the wheels appear to being going backwards when the car is infact going forwards?

e.g. a few mini examples of this at around the 1min - 1min 10 mark.
http://www.youtube.com/watch?v=TeXr50LNJfM

Greg

Last edited by Gregsyuk1; 16.08.2008 at 17:58. Reason: video
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  #703  
Old 16.08.2008, 19:01
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Re: Ask a Scientist

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Yeah, but why does it affect people differently?

Some people react if there's even the slightest bit of heat in their food.

Other people barely notice at all... eg one of my friends used to have pretty much a whole bottle of Tabasco sauce in her Bloody Marys, and used to regularly clean out bars of their Tabasco sauce...

I love Thai/Malaysian food and gobble it down, but I can't seem to build up a physical tolerance to the heat, no matter how regularly I have spicy food...
Hi Bubbles, have wee gander at this; http://www.thenakedscientists.com/fo...0967;boardseen

I personally go along with the genetic factor.

I remember in science at school, we did an experiment which involved putting a dandelion leaf on our tongues and noting the reaction.
We, third or more generation Kiwis don't do well with bitter at all (chiggg!!), but there was a guy in our class that was of direct European descent that never even batted an eyelid, quite interesting really, as so many of us (Pakeha) Kiwis descend from Europe and Europeans seem to be immune to that 'nnggechh' reaction.

Ros

P.S. I also really liked the Ops' signature "Men are the same as women.... just inside out !!"
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  #704  
Old 16.08.2008, 23:52
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Re: Ask a Scientist

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Why, when you are parallel to a car/bike on a road, do the wheels appear to being going backwards when the car is infact going forwards?
In any movie, what you see is made up of a series of individual pictures flashing one after the other at a speed too fast for your eye to see, usually around the 24/25 pictures per second mark. Most stuff moves slowly, but anything happening repetitively at a speeds approaching or beyond 24 time per second causes interesting effects:

If the wheel is turning fast in real life, the spokes are just a blur.

Captured on video, they are frozen for every picture.

So if the wheel moves so that the spokes are in the same position every time the lens opens, the spokes appear not to move at all. If the speed deviates around 25 "spoke replacements" per second, the effect is of the wheel turning slowly, or even backwards.

This can happen in real life too, if you for example have railings between yourself and the other car producing the stroboscope effect.

Last edited by resident; 11.09.2008 at 16:38.
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  #705  
Old 19.08.2008, 15:41
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Re: Ask a Scientist

I saw this and thought of you (wholesome thread readers).


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  #706  
Old 19.08.2008, 15:57
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Re: Ask a Scientist

I have a question for the mathematicians out there.............

How is it that 85% of people surveyed think that they are above average?
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  #707  
Old 19.08.2008, 16:09
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Re: Ask a Scientist

A question for scientists - does anyone have access to the ornithology journal Limicola?
Help!
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  #708  
Old 11.09.2008, 16:37
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Re: Ask a Scientist

Why is "Waltzing Matilda" not a waltz?
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  #709  
Old 11.09.2008, 16:48
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Re: Ask a Scientist

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Why is "Waltzing Matilda" not a waltz?
Because the waltzing referred to is not a dance (it means travelling), neither is Matilda a woman (it's a swag)...

Barbra.
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  #710  
Old 11.09.2008, 17:44
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Re: Ask a Scientist

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How is it that 85% of people surveyed think that they are above average?
1. Because 15% of people ssurveyed have a low self-esteem.

2. People with time to waste doing surveys generally have a point to make and thus skew the statistics.
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  #711  
Old 03.10.2008, 13:30
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Re: Ask a Scientist

At the risk of going way off topic - I thought you scientists might enjoy the latest Savage Chickens offering

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  #712  
Old 03.10.2008, 13:49
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Re: Ask a Scientist

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At the risk of going way off topic - I thought you scientists might enjoy the latest Savage Chickens offering
Another in that vein:



More at www.phdcomics.com
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  #713  
Old 03.10.2008, 13:50
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Re: Ask a Scientist

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If the wheel is turning fast in real life, the spokes are just a blur.

This can happen in real life too, if you for example have railings between yourself and the other car producing the stroboscope effect.
Not only. It can also happen under some (artificial) lighting conditions. If the light is not constant in time (i.e. fluorescent lighting but not lightbulbs or torches), because of the ACness of the current, the light itself is already creating the stroboscopic effect. Which means you can see it. If you are in your office at night and move a pen back and forth in front of a piece of paper, chances are you won't see the same thing as at home.
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  #714  
Old 04.10.2008, 19:23
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Re: Ask a Scientist

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I have a question for the mathematicians out there.............

How is it that 85% of people surveyed think that they are above average?
This is not maths - it's psychology. There are some interesting studies where they asked folk to estimate their results in a test they had just done. Turns out that the best underestimate how good they are and the worst mainly overestimate how good they are.

I'm a physicist so I can't explain why that is .
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  #715  
Old 06.10.2008, 19:39
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Re: Ask a Scientist

Yet another question...

Why are hair shampoo and conditioner sold in different bottles? Are the compounds so utterly different that they can't be mixed, or is it all just because of marketing?
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  #716  
Old 06.10.2008, 20:12
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Re: Ask a Scientist

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Yet another question...

Why are hair shampoo and conditioner sold in different bottles? Are the compounds so utterly different that they can't be mixed, or is it all just because of marketing?
They can be mixed. Wash and go PertPlus. However, for someone with hair like mine, I need actual conditioner, the shampoo/conditioner combo doesn't work for me.

Main ingredient in shampoo is usually sodium lauryl sulfate, a anionic (negatively charged) surfactant. Main ingredient in conditioner is a cationic (positively charged) surfactant. I'm guessing they might associate together a little too much when mixed together to get a really good clean and a really good condition. Hence, better to use them separate.
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  #717  
Old 06.10.2008, 20:30
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Re: Ask a Scientist

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Yet another question...

Why are hair shampoo and conditioner sold in different bottles? Are the compounds so utterly different that they can't be mixed, or is it all just because of marketing?
In short, there is no chemical reason they can't be mixed (i.e they won't react with each other and explode or anything like that) but they achieve quite different things, and (particularly if you have long hair) it can be better to apply them sequentially. If your hair is short, it's not such a big deal.

You can find out more than you ever wanted to know about hair and the science behind hair care (including an explanation of the difference between shampoo and conditioner) on the Exploratorium website. This article also explains other hair-related phenomena, such as why it's easier to curl hair when it's wet than when it's dry, and how permanent curls and permanent hair dyes work. (Of course, you're probably not that interested in learning the differences between shampoo and conditioner, but I thought I'd give the link just in case.)


Heather
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  #718  
Old 06.10.2008, 22:15
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Re: Ask a Scientist

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In short, there is no chemical reason they can't be mixed (i.e they won't react with each other and explode or anything like that) but they achieve quite different things, and (particularly if you have long hair) it can be better to apply them sequentially. If your hair is short, it's not such a big deal.

You can find out more than you ever wanted to know about hair and the science behind hair care (including an explanation of the difference between shampoo and conditioner) on the Exploratorium website. This article also explains other hair-related phenomena, such as why it's easier to curl hair when it's wet than when it's dry, and how permanent curls and permanent hair dyes work. (Of course, you're probably not that interested in learning the differences between shampoo and conditioner, but I thought I'd give the link just in case.)


Heather
I'd say it's always better to use them sequentially. The shampoo is negatively charged, like hair, and its rôle is to clean dirt off your hair, leaving nothing. The conditioner is positively charged and its role is to stay on the hair as an anti-static and easy care agent. As Chemgodess summises, the two love each dearly. If you use them at the same time they tend to get together and not fulfill their required roles. You can get 2-in-1 products, but they're specially formulated and probably not as good, and/or more expensive than the standard one-after-another treatment.
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  #719  
Old 06.10.2008, 22:17
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Re: Ask a Scientist

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I'd say it's always better to use them sequentially. The shampoo is negatively charged, like hair, and its rôle is to clean dirt off your hair, leaving nothing. The conditioner is positively charged and its role is to stay on the hair as an anti-static and easy care agent. As Chemgodess summises, the two love each dearly. If you use them at the same time they tend to get together and not fulfill their required roles. You can get 2-in-1 products, but they're specially formulated and probably not as good, and/or more expensive than the standard one-after-another treatment.
Thank you for reiterating what I said

Pertplus (an american product) is dirt cheap but doesn't work very well.
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  #720  
Old 06.10.2008, 22:42
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Re: Ask a Scientist

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How is it that 85% of people surveyed think that they are above average?


Did you know that 99% of all statistics are wrong
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