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Epiphileon
Posted: Thursday, December 4, 2014 12:32:26 PM

Rank: Advanced Member

Joined: 3/22/2009
Posts: 4,281
Neurons: 166,376
Saw a T-shirt advertised with this printed on it...


[image not available]

and I thought, isn't that backwards? If someone reads that, and then ran away* from you, shouldn't the shirt be either white or blue, in order to be red shifted?

Then I read the description and was even more mystified, besides the most novel color list I think I've ever seen, not the underlined shirts construction.
Quote:
100% pre-shrunk cotton in all colours (exc grey, Antique Jade Dome, Antique Cherry Red, Antique orange, Antique Sapphire 90% cotton 10% polyester, Heather Navy Dark Heather, Heather Red (50% polyester 50% cotton), Heather Royal, Heather Purple, Heather Orange Heather Maroon (65% Cotton 10% Polyester)



What exactly would that shirt look like? You have a whole shirt but constructed of only 75% of the necessary material.

*assuming that anyone standing next to you could only run away from you.
coag
Posted: Thursday, December 4, 2014 1:05:00 PM

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In my opinion, theoretically, if you move fast enough toward the red shirt you would be able to see it as blue. If you move fast enough away from the red shirt, the shirt would become invisible (the wavelength of the perceived electromagnetic wave would be out of the visible spectrum).
Phil Bain
Posted: Thursday, December 4, 2014 1:38:18 PM

Rank: Newbie

Joined: 12/4/2014
Posts: 3
Neurons: 15
Location: São Paulo, Sao Paulo, Brazil
"What exactly would that shirt look like? You have a whole shirt but constructed of only 75% of the necessary material."
Clearly the person who wrote the description is not very good at maths. I suspect there is a missing 'ingredient', but it could just be the percentages are wrong.

About the concept "... if you run fast enough". Doppler blueshift is caused by movement of a source towards the observer, as coaq noted; however, no human could "run" at near-relativistic speeds toward the observer, even our fastest rockets can't do that.
It's a joke for physics nerds to tease on-lookers. Pretty clever, actually.
.:.
kasparijus
Posted: Thursday, December 4, 2014 2:34:48 PM

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Location: Višnjan, Istarska, Croatia
Suppose you are a Dirac electron dressed in this nice red shirt. Your friend, a stationery electron at the bottom of the band, is looking at you. If you run towards it it will see you as dressed in a blue shirt.
Archer5007
Posted: Thursday, December 4, 2014 2:47:41 PM

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Location: Chico, California, United States
What in the hell are you people talking about....
CatCat
Posted: Thursday, December 4, 2014 3:00:13 PM

Rank: Advanced Member

Joined: 8/15/2014
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Location: Toronto, Ontario, Canada
Archery5007 wrote:
What in the hell are you people talking about....


Haha!
early_apex
Posted: Thursday, December 4, 2014 4:53:09 PM
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Joined: 4/20/2009
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Location: Spindletop, Texas, United States
The other 25% must be dark matter, which would affect the shade.
Epiphileon
Posted: Thursday, December 4, 2014 5:16:34 PM

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Joined: 3/22/2009
Posts: 4,281
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early_apex wrote:
The other 25% must be dark matter, which would affect the shade.


Yea but it would push the shirt apart.
Listening . . .
Posted: Thursday, December 4, 2014 5:31:42 PM
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Joined: 6/30/2011
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Epiphileon wrote:
early_apex wrote:
The other 25% must be dark matter, which would affect the shade.


Yea but it would push the shirt apart.


Shouldn't the majority of the shirt be made of dark matter? Think
Epiphileon
Posted: Friday, December 5, 2014 4:49:27 AM

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Joined: 3/22/2009
Posts: 4,281
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Listening . . . wrote:
Epiphileon wrote:
early_apex wrote:
The other 25% must be dark matter, which would affect the shade.


Yea but it would push the shirt apart.


Shouldn't the majority of the shirt be made of dark matter? Think


Think hmmm well, yes but that would be the normal ambient level of dark matter, a 25% local increase in the vicinity of the shirt I think, it seems maybe, just might be disruptive to the shirt, to say nothing, (or just this much) of what it might do to wherever they took it from.
pedro
Posted: Friday, December 5, 2014 5:57:07 AM
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Joined: 5/21/2009
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If everybody ran towards the shirt at the same time would it become heavier?
ithink140
Posted: Friday, December 5, 2014 7:14:29 AM
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I think we should make light of the matter
Jadesqr
Posted: Saturday, December 6, 2014 7:19:29 AM

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Joined: 6/2/2014
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Location: Carolina Beach, North Carolina, United States
I am reminded of a "Big Bang Theory" scipt on 'Superman-the movie':

Penny: "...yeah, men can't fly"

Sheldon: "...lets assume they can".

Sign me, lost in the "QUANTUM"!
Elvandil
Posted: Monday, December 15, 2014 3:32:00 PM

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Joined: 12/5/2014
Posts: 338
Neurons: 149,452
Location: East Montpelier, Vermont, United States
Phil Bain wrote:
"What exactly would that shirt look like? You have a whole shirt but constructed of only 75% of the necessary material."
Clearly the person who wrote the description is not very good at maths. I suspect there is a missing 'ingredient', but it could just be the percentages are wrong.

About the concept "... if you run fast enough". Doppler blueshift is caused by movement of a source towards the observer, as coaq noted; however, no human could "run" at near-relativistic speeds toward the observer, even our fastest rockets can't do that.
It's a joke for physics nerds to tease on-lookers. Pretty clever, actually.
.:.


"Relativistic speeds" have nothing to do with this problem. You would only need to run fast enough to make up for the distance that differs from the red wavelength to the blue, a very small distance, in fact. And you would need to cover that small distance in the same time it takes the red light to travel one wavelength, which is travelling at the speed of light. So the speed you would really need to travel is only about 1/100th the speed of light to see the blue-shift, not impossible. After all, we see red-shifted objects in space that are travelling away from us at velocities far less than the speed of light. The light from objects moving away from us is ALWAYS red-shifted, though if they are not moving fast enough, it may not actually appear to be "red" in color.
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