All this talk of the speed of light has reminded me of yet another useless, but quite interesting fact.



Presume that two photons are travelling in the same direction right beside each other, sort of like this:

· -->
· -->

where "·" represents a photon and "-->" its direction (each photon's velocity is c, the speed of light).

If we call one of the photons "A" and the other "B", what's the velocity of photon A relative to photon B and the velocity of photon B relative to photon A?


If your answer is zero, you are wrong - both velocities (that of photon A relative to photon B and of photon B relative to photon A) are c (the speed of light).

If your reaction to this is ZOMGWTFUSACCCPHAX, you have simply forgotten that the speed of light is constant in all frames of reference. This means that if something travels at the speed of light relative to one frame of reference, it travels at the speed of light relative to every frame of reference. Thus, the photon A also travels at the speed of light relative to the photon B's frame of reference, and vice versa.

You would probably ask "But how can we observe the two photons to always be right beside each other if they're travelling at the speed of light relative to each other?" The answer is simple - they're not moving relative to each other from our frame of reference, because from our frame of reference both time passage for photon A and time passage for photon B has stopped (due to time dilation because they're both travelling at the speed of light relative to us) - so even though they both have velocities c relative to each other their distances from each other don't change from our frame of reference because from our frame of reference time passage for both of them has stopped.


Gosh, I love the theory of relativity. :nerd:

It's like drinking a Slurpe. At the first sip you think it's good and go: Hey I'm glad I did this and by the second sip the ice gets to your brain and you go: OW! OW! OW!

A friend of mine hates it, he can't stand the fact that everything except the speed of light is relative, he likes solid facts.

Uh, I don't think from our frame of reference that their time passage has stopped.
If that was the case, they would not be moving at all.
Unless time dilation is completely different then what I know.

All I know is that time doesn't stop. Even at the speed of light.
Sure the object at the speed of light is less effected by time, but it doesn't cease all movement.
And any object, when time is stopped, can never move. Even if it's traveling at the speed of light to begin with. Without the existence of time, after all, nothing can move. Not even Tachyons.

Unless frame of reference is completely different. I mean, even if I can run at the speed of light, and watch a bullet in the air, it's still going to travel, even if to my frame of reference, it looks at a stand still. It's still moving, even in my frame of reference it's still moving....just so slow...

http://en.wikipedia.org/wiki/Time_dilation#Overview_of_formulae

That graph on the right is incomplete - as it gets closer to 1c it goes to infinity.

You'll notice that the Lorentz factor γ in the case of the speed of light becomes 1/√(1 - c²/c²) = 1/√(1-1) = 1/√0 = 1/0 = ∞
That means that the time passage of something that's travelling at the speed of light relative to you is (relative to you) infinitely slower than your time passage.

Ah. Okay. I got confused then. My bad.

Time dilation confuses me.
That does explain why it would only take you 5 years or so to get to Alpha Centari, but when you got there, and returned to earth, 80 years would have passed.

Wait, are you saying that something traveling at the speed of light looks standing still by out frame of reference?
Oh, but only if it has mass. Unlike Photons. Otherwise nothing could be seen.

That is if you would travel at a speed close to the speed of light, not actually at the speed of light. If you travelled exactly at the speed of light, you would get from Earth to Alpha Centauri instantly.

Both you within the space vessel and observers on Earth would agree that for you the journey was instantaneous. However, for different reasons:

From your frame of reference (within the space vessel), the journey being instantaneous for you would be a consequence of http://en.wikipedia.org/wiki/Length_contraction. From your frame of reference you and the ship were stationary and Earth and Alpha Centauri were travelling relative to you and the vessel at the speed of light. As a consequence of this, the contraction of length of distance between the Earth and Alpha Centauri was infinite from your frame of reference, so to get from Earth to Alpha Centauri you had to travel a distance of 0, thus the journey was instantaneous for you.

From the frame of reference of the observers on Earth, the journey being instantaneous for you would be a consequence of time dilation. From their frame of reference you were travelling at the speed of light and thus from their frame of reference the time passage for you has stopped and from their frame of reference time for you "stood still" your entire journey, so the trip for you was instantaneous.

The reason why ultimately more time would have passed for those on Earth than those on the space vessel is because you would be changing frames of reference due to acceleration and deceleration. It's explained in detail http://en.wikipedia.org/wiki/Twin_paradox (specifically http://en.wikipedia.org/wiki/Twin_paradox#Difference_in_elapsed_time_as_a_result_of_differences_in_twins.27_spacetime_paths).

I hate you so much right now. I wasn't really paying attention to it and jumped a sodding mile. Spilt tea on me <_<

Useless fact: This thread will be locked in approximately 16 posts.

Hey, don't worry. I was paying attention to it and I still jumped!

Useless fact; I don't get the "Quantum Theory Headache" that most people get when hearing or thinking about Quantum mechanics or the ramifications of the Theory of Relativity.

There's quite the simple explanation for that; "If you're not shocked by it, you haven't understood it".

Actually, I do understand that a particle is held in a indeterminate state until measured- and that this would be like a cat, sealed in a box with a poison canister set to go off at a random time, would be both alive and dead at the same time until you actually opened the box to check on it.

I also understand that a singe photon can interact with itself like a wave, even though it should be impossible for it to do so. (Because it's both a particle and a wave)

Also, that time stops for an object "going into" a black hole from all outside observers, even though this doesn't occur for the object itself.

Also that a pair of entangled particles seemingly violate the speed of light limit since when one changes positions, the other changes to the opposite position instantainiously.

Your head hurting yet? Mine ain't!

Also, the Scientific term for a football-shaped object is a prolate spheroid.

Schr?dinger's Cat

You have understood all the ridiculous simplifications of quantum theory that you read in high-school books.

You have not understood quantum theory.

I knew that

That's actually marriage, Walter says so

Which then equates marriage to Quantum Physics.

Quantum Physics = "If you're not shocked by it, you haven't understood it".

Marriage = "if your head doesn't hurt constantly, you haven't a clue what's going on."


close enough to fit.


Hey guys, I've cracked it :celebration:

Crocodilians tend to grow throughout their whole lives.

Henry VIII had the world's largest turducken.

The M1 Abrams main battle tank has armor with depleted uranium mesh.

Some ducks have very long, corkscrew-like pencses.

Largest what???



Sounds like the solution why Donald always gets screwed

A turducken is a meal created by putting chicken inside a duck inside a turkey.

http://instantrimshot.com/

The term for a pregnant goldfish: Twit.

Lewis Carrol (Charles Lutwidge Dodgson) wrote Alice's Adventures in Wonderland while standing up.

The language of Taki, spoken in parts of Guinea, only contains 340 words.

King George II's diary entry for July 4, 1776: "Nothing of importance happened today."

There are 27 chemicals that can be added to bread without being listed on the label.

75% of all murder victims knew their killer.

Pres. Herbert Hoover never accepted his presidential salary.

A lifeguard in Ravenna Italy lost his job for being "too accurate." 3 people drowned because he hit them with life preservers.

1/4 of al species of snakes are venomous (800 of 2400)

The USA rainks first in terms of overall nasty weather.

In some cases, ransom paid for kidnap victims are tax-deductable.

Per Capita, Alaskans eat twice as much ice cream as the rest of the nation.

A 100-ton blue whale eats it's own weight in krill every month.

In England, in 1558, beards were taxed according to their length.

American Indians rarely go bald.

Coldest place on Earth: Vostok, Antartica. Average annual temperature: -72^oF

Each mile of a 4-lane freeway takes up over 17 acres of land.

60% of athiests and agnostics say they own at least one Bible.

Giant oil tankers get about 31... feet per gallon.

George Washington's name has been given to 1 state, 7 mountains, 8 streams, 9 colleges, 10 lakes, 33 counties, and 121 towns.

Denmark's flag has remained the same since the 13^th century.

A hippo's stomach is 10 feet long, and can hold 400 lb. of food.

Mount Irazu in Costa Rica is the only point in the Americas where one can see both the Atlantic and Pacific oceans.

The world's largest zipper is the one that zips the turf together in the Houston Astrodome.

Disney World is twice the size of Manhattan.

Comedian Stan Laurel was married 8 times, but only had 4 wives.

Of the 80,000 known species of plant, only 50 are cultivated regularly.

72% of Americans don't know the people who live next door.

The 1953 film The Moon Is Blue was condemned by the Roman Catholic Legion of Decency because... it contained the words "mistriss" and "virgin."

The notebooks used by Marie and Peirre Curie are still too radioactive to handle safely.

The winning bid for a "Moldy Lemon" on eBay: $6.75.

Someone once tried to sell their soul on eBay. It was taken down after it had reached about $50 because it wasn't an item that the seller could readily give to the buyer.

And finally... The most useless facts aren't facts at all- they're false information that seems plausible, usually to the point where the person who spreads it doesn't realize it's not a "fact."

I made the mistake of holding coffee the first time I saw that. I thought about suing Starbucks.


What's a crocodilian?


He had the largest turkey stuffed with duck stuffed with chicken? He must have had one fowl appetite.


The 30 mm GAU-8/A Avenger Gatling cannon on the A-10 Thunderbolt II fires armor piercing shells made of depleted uranium. It can fire 3,900 rounds per minute and put 80% of its shots within a 40-foot circle from 4,000 feet while in flight. Let's see the M1 Abrams stand up to that.



Umm...800 out of 2400 is 1/3.

Hold on... checking the source...

*elivator music plays*

The source was incorrect... so either 1/3rd of all snakes are venomous, or the actual number is 800 out of 3200, or 600 out of 2400.

Thanks for pointing that out!

[quote name='The Vyper' date='25 August 2010 - 05:00 PM' timestamp='1282770052' post='16321739']
What's a crocodilian? [/quote]
A group of reptiles that includes crocodiles, alligators, caimans, and gharials.


[quote name='The Vyper' date='25 August 2010 - 05:00 PM' timestamp='1282770052' post='16321739']He had the largest turkey stuffed with duck stuffed with chicken? He must have had one fowl appetite. [/quote]
It was a monster, made up of a bustard stuffed with a turkey, a goose, a pheasant, a chicken, a duck, a guinea fowl, a teal, a woodcock, a partridge, a plover, a lapwing, a quail, a thrush, a lark, an ortolan bunting, a garden warbler, and an olive.[/quote]

[quote name='The Vyper' date='25 August 2010 - 05:00 PM' timestamp='1282770052' post='16321739']The 30 mm GAU-8/A Avenger Gatling cannon on the A-10 Thunderbolt II fires armor piercing shells made of depleted uranium. It can fire 3,900 rounds per minute and put 80% of its shots within a 40-foot circle from 4,000 feet while in flight. Let's see the M1 Abrams stand up to that.

Oh yes, I'm well aware of the Warthog's durability and badassery.

[/quote]

[quote name='rmctagg09' date='25 August 2010 - 05:13 PM' timestamp='1282770823' post='16321775']
It was a monster, made up of a bustard stuffed with a turkey, a goose, a pheasant, a chicken, a duck, a guinea fowl, a teal, a woodcock, a partridge, a plover, a lapwing, a quail, a thrush, a lark, an ortolan bunting, a garden warbler, and an olive.[/quote]
[/quote]

So it WASN'T a Turducken, it was a Busturgoophechicduckguintealwoodpartplovlapquailthruslarkortwarive!

... I have no idea how to pronounce that...

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