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☖ Forums → Discussion Forum → Astrophysics (help me win an argument)!
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Astrophysics (help me win an argument)!
2008-12-28, 10:40 PM #1
Hey there!

We were arguing about the speed of light with my wife yesterday; She did not believe me that some stars we see may not, in fact, exist anymore (by the time it will take for their light to reach Earth, the stars may already be gone).

I looked up a few articles (mainly on Wikipedia and a couple of articles on BBC News), but nothing definite. Can you guys give me a couple of links / arguments that would help me prove my point?

Thanks!
幻術
2008-12-28, 10:48 PM #2
Pretty damn definitive.

Light is composed of photons. They move. They only move so fast. When something is really really far away, the light coming from it is really really old. I don't know how else to explain it.
Bassoon, n. A brazen instrument into which a fool blows out his brains.
2008-12-28, 11:07 PM #3
Wow. No offense, but your wife is pretty dumb.
"it is time to get a credit card to complete my financial independance" — Tibby, Aug. 2009
2008-12-28, 11:19 PM #4
Tell her to get back in the kitchen where she belongs.
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2008-12-28, 11:21 PM #5
how can someone not understand ballistic physics

it is hard coded into our dna
2008-12-29, 12:06 AM #6
Originally posted by Freelancer:
Wow. No offense, but your wife is pretty dumb.


Quote:
-just because you said 'no offense' doesn't mean you get to say whatever you want!

-yes it does! it in the Geneva convention!

.
Welcome to the douchebag club. We'd give you some cookies, but some douche ate all of them. -Rob
2008-12-29, 12:38 AM #7
it's like how your old great-aunt can have mailed you a birthday cheque but died before you received it... only when it comes to stars it's cool instead of sad.
2008-12-29, 12:47 AM #8
I'll give his wife the benefit of the doubt and say that she's smart enough to understand the concepts at hand, but hasn't been taught properly.

I think you should start by explaining that light is composed of photons (don't bother talking about wave-particle duality, that's too advanced), and that the images we see are the result of the rods and cones in our eyes sending electrical signals to our brain, which creates an image. Then explain that, light is really fast, but the universe is really big, so by the time light reaches us, things could happen on the other side.
Bassoon, n. A brazen instrument into which a fool blows out his brains.
2008-12-29, 2:22 AM #9
Originally posted by Freelancer:
Wow. No offense, but your wife is pretty dumb.


Originally posted by TimeWolfOfThePast:
Tell her to get back in the kitchen where she belongs.


Do you speak like this in person too, or just on the internet?

But anyway, thanks Emon and Vornskr! I'm not sure what wave-particle duality is myself (but then, Wikipedia's always at hand), but thanks for advise! Cheers.
幻術
2008-12-29, 2:50 AM #10
I'm pretty sure TimeWolf was joking.
Bassoon, n. A brazen instrument into which a fool blows out his brains.
2008-12-29, 2:54 AM #11
Originally posted by Koobie:
Do you speak like this in person too, or just on the internet?


It's very common and quite normal to express yourself differently on the internet than in real life.
Looks like we're not going down after all, so nevermind.
2008-12-29, 3:29 AM #12
Timewolf was joking, Freelancer is nuts.
COUCHMAN IS BACK BABY
2008-12-29, 3:44 AM #13
Indeed, Koobie! I always find it fascinating that when you're gazing at stars, you're gazing through both space and time. You're looking at objects that are a very long way away, and it takes a finite amount of time for the light from them to reach you. Any number of things might happen in that finite time, and some of those stars will have gone supernova. You're looking at stars that have already died.

Although you may also be looking at planets. A few months ago, you could see Jupiter and Venus with the naked eye (or just a pair of good binoculars) when they appeared quite close to the moon.
"The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt. " - Bertrand Russell
The Triumph of Stupidity in Mortals and Others 1931-1935
2008-12-29, 8:00 AM #14
Everyone thinks a little differently to anyone else.

The idea of something you can see not existing is a little hard for some to swallow. I guess you could say its sort of an optical illusion.
2008-12-29, 9:08 AM #15
Sometimes knowing you're right is all you need to win an argument. Letting the other person argue the obviously wrong point is more than enough fun.
Quote Originally Posted by FastGamerr
"hurr hairy guy said my backhair looks dumb hurr hairy guy smash"
2008-12-29, 10:24 AM #16
Originally posted by Emon:
I'll give his wife the benefit of the doubt and say that she's smart enough to understand the concepts at hand, but hasn't been taught properly.

I think you should start by explaining that light is composed of photons-


I'm sure she'll be lost right about here
"Nulla tenaci invia est via"
2008-12-29, 10:53 AM #17
just say light travels at ___ speed, the star is ___ distance away, and also the star only has a life span of ___ years, so if the star is far enough away it can burn out before the light ever reaches earth, so what we are seeing is really light that a dead star gave off a long time ago.

you could use the noise from large fireworks for a comparison. if you have ever seen a fireworks show from a ways away sometimes the firework can go off and fizzle out completely before you ever hear the bang from it.

...dont say anything about photons.
Welcome to the douchebag club. We'd give you some cookies, but some douche ate all of them. -Rob
2008-12-29, 3:57 PM #18
your wife is right. Because stars dont really exist. They're just wee dots that circle the earth, the Earth that god made in his infinite wisdom.
Code:
if(getThingFlags(source) & 0x8){
  do her}
elseif(getThingFlags(source) & 0x4){
  do other babe}
else{
  do a dude}
2008-12-29, 4:18 PM #19
Tell her it's like sound; it takes time for it to get to you, but it's so fast that you only notice it over massive distances.
2008-12-30, 9:42 AM #20
oh, oh! tell her its like a bowl of rice crispies! you know like wen the cereal sits in the milk for too long and... ah, never mind.
Welcome to the douchebag club. We'd give you some cookies, but some douche ate all of them. -Rob
2008-12-30, 12:52 PM #21
Maybe the sound idea would work better, explain it like an echo. Even though she already made the sound, she will hear it after it bounces off a cliff and comes back.
Quote Originally Posted by FastGamerr
"hurr hairy guy said my backhair looks dumb hurr hairy guy smash"
2008-12-30, 3:14 PM #22
Originally posted by Freelancer:
Wow. No offense, but your wife is pretty dumb.


I'm not sure how you can say something like this and expect not to offend.
If you think the waiters are rude, you should see the manager.
2008-12-30, 3:19 PM #23
That's why he said no offense.
2008-12-30, 3:19 PM #24
Originally posted by Michael MacFarlane:
I'm not sure how you can say something like this and expect not to offend.


I'm not sure how someone can be smart and refuse to believe this even after it's been explained to her.

Are you telling me she's not dumb?
"it is time to get a credit card to complete my financial independance" — Tibby, Aug. 2009
2008-12-30, 3:26 PM #25
Originally posted by Squirrel King:
That's why he said no offense.


No offense, but **** you ***ing son of a mother****ing ***licking cockplunger you can **** the **** off my *** into your *** and **** it into your face. No offense, btw.
"The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt. " - Bertrand Russell
The Triumph of Stupidity in Mortals and Others 1931-1935
2008-12-30, 3:27 PM #26
That made me giggle.
2008-12-30, 3:28 PM #27
cockplunger? lol..
"it is time to get a credit card to complete my financial independance" — Tibby, Aug. 2009
2008-12-30, 8:59 PM #28
Originally posted by Squirrel King:
That's why he said no offense.


It doesn't make any sense to preface an obviously offensive statement with "No offense."

Originally posted by Freelancer:
I'm not sure how someone can be smart and refuse to believe this even after it's been explained to her.

Are you telling me she's not dumb?


I don't know if she's dumb. But usually the best way not to give offense, if you don't mean to, is not to say things like that. :eng101:
If you think the waiters are rude, you should see the manager.
2008-12-30, 9:13 PM #29
But Freelancer's intention wasn't to offend. He didn't call her a blithering idiot or the like, with any real obvious intention to offend, he just commented that she must not be especially clever by calling her "dumb." This is why he prefixed his statement with "No offence," not to prevent you from taking offence from the statement, but to indicate he wasn't trying to insult her.

Why am I defending Freelancer? This thread is stupid.
2008-12-30, 9:14 PM #30
Originally posted by Michael MacFarlane:
I don't know if she's dumb. But usually the best way not to give offense, if you don't mean to, is not to say things like that. :eng101:


Sorry, I'm incapable of that.
"it is time to get a credit card to complete my financial independance" — Tibby, Aug. 2009
2008-12-30, 10:02 PM #31
Originally posted by Jin:
But Freelancer's intention wasn't to offend. He didn't call her a blithering idiot or the like, with any real obvious intention to offend, he just commented that she must not be especially clever by calling her "dumb." This is why he prefixed his statement with "No offence," not to prevent you from taking offence from the statement, but to indicate he wasn't trying to insult her.

Why am I defending Freelancer? This thread is stupid.


I suppose that makes some sense. The juxtaposition of an insulting statement with "no offense" just seemed odd to me.
If you think the waiters are rude, you should see the manager.
2008-12-30, 10:21 PM #32
The real question now is: am I really sorry? :ninja:
"it is time to get a credit card to complete my financial independance" — Tibby, Aug. 2009
2008-12-30, 11:03 PM #33
:science:
Photons are the only known particle (or wave) that can travel at exactly the speed of light (c).

The photon has no mass.

Energy of a photon: E = hc/λ = hν

Momentum of a photon: p = h/λ = (h-bar)k where k = h/2π

Speed of Light in a Vaccuum: c = 299,792,458 m/s on the dot

Even more :science:

To give you an idea of just how far apart things are in universe, if Earth and Mars are the furthest possible apart it is about 402,336,000 km. Light, the fastest thing we know to exist in this universe, takes 1,342 seconds or 22.37 minutes. 22 minutes to reach Mars travelling at c.
Code to the left of him, code to the right of him, code in front of him compil'd and thundered. Programm'd at with shot and $SHELL. Boldly he typed and well. Into the jaws of C. Into the mouth of PERL. Debug'd the 0x258.
2008-12-30, 11:25 PM #34
you know what will really boggle her mind? even though we can see the star, assuming it doesn't exist anymore, we won't feel any gravitational effects from it. trippy! gravity affects all matter in the universe instantly (ie faster than light)! algebraic!
2008-12-30, 11:28 PM #35
Tell her it's like ejaculation: there's a delay between it exiting the urethra and reaching her face. She will understand.
Looks like we're not going down after all, so nevermind.
2008-12-30, 11:48 PM #36
Originally posted by ragna:
gravity affects all matter in the universe instantly (ie faster than light)!


http://en.wikipedia.org/wiki/Speed_of_gravity

Unlikely to be true, or--at the very least--the speed of gravity is unknown. But gravity having instantaneous effects would allow information to be transmitted faster than light, which causes problems...
2008-12-31, 12:36 AM #37
How would that cause problems?
"it is time to get a credit card to complete my financial independance" — Tibby, Aug. 2009
2008-12-31, 1:04 AM #38
According to special relativity, within certain limits, the timeline of events isn't fixed. Two events that seem simultaneous to one observer aren't simultaneous for another observer; two events can even happen in opposite orders for different observers. That is, what looks like a cause-effect relationship to one observer could be reversed for a different observer; the way the math works out, if the observers could send messages to each other faster than the speed of light, they could create a paradox.

Then again, http://en.wikipedia.org/wiki/Special_relativity#Causality_and_prohibition_of_motion_faster_than_light says that the situation is more complicated in general relativity. I didn't get that far in college, so I really can't say...
2008-12-31, 1:27 AM #39
interesting
"Nulla tenaci invia est via"
2008-12-31, 5:38 AM #40
Gravity most likely 'travels' at the speed of light. The same way the time delay in the effect of a magnetic field has been measured.

Also, all energy in the universe is light.
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