Travelling at the speed of light....

[astromanian]

If you were traveling at the speed of light in a spacecraft, what would happen if you switched your headlights on ?

Ian.

[timthelder]

if you switched your headlights on ?


If I were in a spacecraft, traveling at 186,000 miles per second, the headlights would be the LEAST of my worries.:eek:

[Radar]

G'day Ian,

I think the rule of thumb is, is if you were to turn on your headlights, the light being emitted from your headlights would leave you at the speed of light. From your perspective, time would slow down to allow for this to happen. No matter where you stand or sit in the universe and no matter how fast you move, light will always move at the speed of light relative to you.

I think this is called Time Dilation.

Ray

[Aussie Pete]

Ray is correct and why does your spiffy spaceship have headlights?

:)

Pete

[Tenacious Del]

I've heard and read a bit about this stuff now, but I'm not convinced that time slows down the faster you move. My head just hasn't got around this yet.

[CanisMajorTom]

When they say time slows down, does that mean you live longer? Or does time just go slower for you? :confused:

[Aussie Pete]

Well, lets say you leave Earth in your spiffy new spaceship for a very quick trip through the solar system just for fun before dinner. The wife will stay at home on Earth and watch the wall clock till you get back for the meal :)

You zoom off for a round trip at 99.00% light speed and thanks to your headlights don't hit anything huge except for a few gazillion atoms and particles (bad news by the way).

Returning to Earth after this relativistic cruise in the solar system you land in the backyard and look at your watch, your lap took only 47 minutes. But the wife looks very miffed because by her clock you've been gone for just over 5 hours!

Time has slowed for you RELATIVE to other clocks on Earth. And dinner is cold.

Pete

[Tenacious Del]

your lap took only 47 minutes. But the wife looks very miffed because by her clock you've been gone for just over 5 hours!

okay but how do you work this out? what is the math behind 47 minutes at light speed = 5 hours down here? this is way over my head but i love it. :crazy:

Del

[wakaleo]

Ray is correct and why does your spiffy spaceship have headlights?

:)

Pete

I'm surprised you asked the question Paul. They're so you can see your way through dark matter and black holes of course! ;-)

Jim

[LJF]

Returning to Earth after this relativistic cruise in the solar system you land in the backyard and look at your watch, your lap took only 47 minutes. But the wife looks very miffed because by her clock you've been gone for just over 5 hours!

This would be impossible because time is relative. Our system of time is based on the earth, which i call earth time.

For instance, traveling 3 light years at the speed of light will take you three years to travel. This is based on earth time so on earth it will also be three years before whoever is traveling to the place.

Earth time os base time for us humans. No matter how fast we go, it wont change for us. (clock wont automaticly speed up or slow down, for instance)

[Aussie Pete]

Earth time os base time for us humans. No matter how fast we go, it wont change for us. (clock wont automaticly speed up or slow down, for instance).This would be impossible because time is relative. Our system of time is based on the earth, which i call earth time.

Do your homework before you say things like "Impossible". Time dilation does not imply your clock goes wacko while you look at it (speeding up or slowing down like a bad fake Rolex). My exampled effect is not noticed by the crew until they return and compare clocks at journeys end, in this case back in Earth's gravity field. Our time is not universal, if your spiffy spaceship were in orbit of a black hole, just within its event horizon, then time for you compared to the rest of the universe would actually stop. Time would seem "normal" on board the spaceship whilst eons could pass for those outside.

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

http://casswww.ucsd.edu/public/tutorial/Intro.html

http://www.time.com/time/magazine/article/0,9171,839785,00.html

Cheers...Pete

[Astro Dave]

This maleability of time is a fact. Time for you slows down (relative to an outside frame of reference) if you're in motion.

It's observable and testable. In fact, it has been tested.

I remember a few years ago two clocks were made (Caesium if I remember) - one was sent flying around the world in a plane (it was in motion) - the other was at rest on the earth.

When the two clocks were compared one scientist said to the other, " Geez, Look at that (translated: *##*&*#**) the clock from the plane is one nanosecond slower.

It's a fact of realtivity, as Einstein predicted - "Moving Clocks Run Slow!"

I'm out of action for awhile... off to the USA next week: Kennedy Space Centre, Air and Space Museum Washington, Meteor Crater Arizona and Lowell Obs, AND the Winter Star Party in the Florida Keys (600 scopes +) covering these stories for Sky and Space Magazine.

..who hates me? :biggrin:

[Aussie Pete]

I'm out of action for awhile... off to the USA next week: Kennedy Space Centre, Air and Space Museum Washington, Meteor Crater Arizona and Lowell Obs, AND the Winter Star Party in the Florida Keys (600 scopes +) covering these stories for Sky and Space Magazine.

..who hates me? :biggrin:

I for one mate! :)

I've done a similar cross continental "Space Tour" of the USA..FANTASTIC!! Hey we can compare watches when you get back!
I look forward to the write ups! Safe and enjoyable journey Dave!!

[Tenacious Del]

that wikipedia link was interesting.



..who hates me? :biggrin:

I certainly do :ahh!:

[Astro Dave]

heh heh good one Del

Thanks Pete and yes, you'd know what sort of sights lay ahead. I'll be doing a series for the mag so you'll read all about it soon.

I'd bring you both back a rock from Meteor Crater.... but I think it's illegal to nick anything from the site. Funny, the whole place is just full of rocks!!! There's nothing else there!

Psst, don't tell Radar I'm going. I can't stand tears.

[Radar]

Psst, don't tell Radar I'm going. I can't stand tears.

Usually I would cry in a situation like this Dave, but I'm glad you are leaving the country for a while. So it kinda evens it out, lol. :biggrin: :biggrin: :biggrin: :biggrin:

[LJF]

Do your homework before you say things like "Impossible". Time dilation does not imply your clock goes wacko while you look at it (speeding up or slowing down like a bad fake Rolex). My exampled effect is not noticed by the crew until they return and compare clocks at journeys end, in this case back in Earth's gravity field. Our time is not universal, if your spiffy spaceship were in orbit of a black hole, just within its event horizon, then time for you compared to the rest of the universe would actually stop. Time would seem "normal" on board the spaceship whilst eons could pass for those outside.

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

http://casswww.ucsd.edu/public/tutorial/Intro.html

http://www.time.com/time/magazine/ar...839785,00.html

Two things. One i'm sorry i don't mean to say impossible. I know that nothing is truly impossible. Second I wouldn't really trust anything from wikipedia. Some of that stuffed is so @#$%ed up. I know a guy that goes on there just to mess up stuff.


This maleability of time is a fact. Time for you slows down (relative to an outside frame of reference) if you're in motion.

It's observable and testable. In fact, it has been tested.

I remember a few years ago two clocks were made (Caesium if I remember) - one was sent flying around the world in a plane (it was in motion) - the other was at rest on the earth.

When the two clocks were compared one scientist said to the other, " Geez, Look at that (translated: *##*&*#**) the clock from the plane is one nanosecond slower.

It's a fact of realtivity, as Einstein predicted - "Moving Clocks Run Slow!"

One thng to say. I don't really trust this fact. A nanosecond is such a short amount of time that the origional setting of the clocks could have been off. Even if it was set by computers. There is no way to prove this wasn't human or computer error.

[Radar]

There is no way to prove this wasn't human or computer
error.

That's a valid argument.

[Aussie Pete]

Actually its not Ray. Why not let LJF say "I see no curve, therefore the world is flat". Is that valid?

These time dilation effects were validated from the resulting data of repeated experiment and investigation by folks far more qualified than we. Its real, no matter how brain bending it is to some. :)

Lets read what an expert says. Its what they are good at. The GPS system we all use with confidence would fall down without taking time dilation into account.

Courtesy Prof Richard W. Pogge of Ohio State University. Great podcaster too :)

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html

Nuff said.

Pete

[Astro Dave]

Pete, you're dead right.

"It can't be, therefore it isn't" is a bad way to do science my erstwhile young friend LJF (you're not related to LBJ are you? or Lynda Bird?)

Anyway, a nanosecond may be slow BUT it is a unit of time AND it can be measuresd.

Look, these 'clocks' aren't ordinary clocks... clocks is a bad word although anything that measures time is a clock, it's just a device OK?

Whew! ... OK, today, cesium clocks measure with an accuracy of from 2 to 3 parts in 10 to the 14th, i.e. 0.00000000000002 Hz; this corresponds to a time measurement accuracy of 2 nanoseconds per day or one second in 1,400,000 years.

It is the most accurate realization of a unit that mankind has yet achieved. A cesium clock operates by the vibration of cesium atoms at one of their resonant frequencies and then counts the corresponding cycles as a measure of time.

Radar, two clocks set running using this method will NOT change.

[Radar]

G'day Pete / Dave,

If the experiment had only been done once then LJF would have had a good point. It would have at least been something that needed looking at. LJF obviously is new to time dilation, and to be honest, as a 14 year old he's doing pretty well tackling something such as time dilation. :smile:


These time dilation effects were validated from the resulting data of repeated experiment and investigation by folks far more qualified than we. Its real, no matter how brain bending it is to some. :)


That's a valid argument. I along with others have very little knowledge of time dilation, even though I totally agree that it happens. I'll check that link out Pete. Interesting, actually awesome that the gps system takes it into account.


Radar, two clocks set running using this method will NOT change.

First time I've heard of these clocks Dave, totally amazing what kind of accuracy humans have acheived.

On another note, remember you guys are both veterans, this info is nano- second nature for you both (how good was that pun?:biggrin: ). And the younger ones are still not only learning this enduring subject, but also how to go about learning this subject. So wording should not be taken too literally on debates such as this.

The time dilation concept is brilliant. Thanks to Einstein for making this place so complicated.:biggrin:

Ray

[gyro]

I concur with previous comments re: 'GPS timing'. However, with my in-car route-finder, it is of little comfort to know to the nano second just how late I am.... WHEN LOST.....:Oh_No:

[LJF]

I see what you're talking about now. Still I say that if you traveled for 47 minutes by your watch and 5 hours on earth you would have to go extremly far. If going around the world only set you back one nanosecond. I'll try to figure out the exact calculations.:hmm: :hmm:

[gyro]

I see what you're talking about now. Still I say that if you traveled for 47 minutes by your watch and 5 hours on earth you would have to go extremly far. If going around the world only set you back one nanosecond. I'll try to figure out the exact calculations.:hmm: :hmm:

Good for you LJF, stick at it, what we are not telling you is how long it took for us to get our heads around the subject....measured in Earth years :wink: :wink:

Don't get tied up with the figures here, just try to understand the concept, after all Einstein was several years older than you before he figured it out. Who knows where your enthusiasm will lead.......watch this space guys.

[Aussie Pete]

LJF is 14 yr old?!

Wow..keep asking the BIG questions mate..its not a sin! :)

hehehe..

Pete

[LJF]

I think I have the calculation.

5 hr * 6o min per hr = 300 min
300min - 47 min = 253 min difference
253min * 60 sec per minute = 15,180 sec
15,180 sec * 1,000,000,000 nanosec per sec = 1,518,000,000,000 nanosec

earth is approx 40,075.2 km circumference

1,518,000,000,000 nanosec * 40.075.2 km =

608,341,536,000,000,000 km is what you would have to travel for your clock to say 47 minutes while an earth clock says 5 hours

(im not saying im right. This is an approx. And i might have goofed a calculation.)

Told you I could do it.:eartoear: :ta_clap5:

[Astro Dave]

Hey, I gotta say that I like LJF. You remind me of me when I was.. err, a little thinner. People used to say to me in my quieter, reflective times, "What are you thinking about." I couldn't tell them ... I hardly knew myself. I was puzzling over this time thing too - SO I did something about it, I got a book (square thing-thick cover, with thin pages in the middle, symbols on pages) and read up on the subject.

A lot of the older guys around here (I'm not in that category by the way) probably did the same. LJF, It needs time to understand time. Keep thinking, you are an inspiration.

BTW - head over to YouTube and plug in 'Time Dilation' or 'Time Travel' in the search box. There's a few interesting little vid clips that will help.

[Astro Dave]

Keep in mind young LJF that time dilation is not a factor of distance, so much as a factor of (relative) speed.

The only exception, it seems, is W.A. - who are in a constant state of time dilation without moving ... ??? Here in NSW of course everyting runs to time.(pun) witty, huh?

[LJF]

Well I wass talking about if it were a constant speed.

If it wasn't you'd have to get into algebra and trigonemetry and variables and all that fun stuff. I twould be a lot harder to show over the internet.:confused:

[Radar]

I think I have the calculation.

5 hr * 6o min per hr = 300 min
300min - 47 min = 253 min difference
253min * 60 sec per minute = 15,180 sec
15,180 sec * 1,000,000,000 nanosec per sec = 1,518,000,000,000 nanosec

earth is approx 40,075.2 km circumference

1,518,000,000,000 nanosec * 40.075.2 km =

608,341,536,000,000,000 km is what you would have to travel for your clock to say 47 minutes while an earth clock says 5 hours

(im not saying im right. This is an approx. And i might have goofed a calculation.)

Told you I could do it.:eartoear: :ta_clap5:

Holy cow, well done mate. I'll have to look in to this further. I'm still behind on the ratio's of time dilation.



The only exception, it seems, is W.A. - who are in a constant state of time dilation without moving ... ??? Here in NSW of course everyting runs to time.(pun) witty, huh?

Because Astro Dave is in a constant state of Time Dilation (as well as pupil dilation), he forgets that W.A could mean many other places around the world. As a typical Australian he thinks eveyone in the world lives in Australia. So for clarity, when Astro Dave says W.A he means Western Austalia. :biggrin:

Hopefully when Dave comes back from his overseas holiday soon, he'll be one nanosecond younger. He needs all the help he can get. :biggrin: :woot: :woot: :crazy:

[Astro Dave]

I knew it - I knew it ... Radar hates me!!!!! And its all my fault...:confused: :confused:

[Radar]

I knew it - I knew it ... Radar hates me!!!!! And its all my fault...:confused: :confused:

Radar loves you mate. Radar also likes to talk about himself in third person.

Radar simply has to warn other members about you. :crazy: :woot: :crazy:

[LJF]

:crazy: :crazy: :crazy: :crazy: :crazy: :crazy: :crazy: :crazy: :crazy: :crazy:




Sorry i've been wanting to do that for a while now.

[gyro]

Can I remind you chaps that this thread began with a serious tone,,:rulez:

http://dingo.care2.com/cards/flash/5409/galaxy.swf

[LJF]

HAAA PTTTTTTTTTTTTTTTT!!!!!!!!!!!!!!:nana:

Sorry I know. How did it get this way?

Help me back to sanity.