# The Naked Scientists Forum

### Author Topic: lights velocity  (Read 11260 times)

#### ukmicky

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##### Re: lights velocity
« Reply #25 on: 26/07/2006 22:46:48 »
The speed of light is constant,the direction of view or the motion of the observer doesnt affect the speed that the observer measures light to be travelling at.
No matter how fast your moving light will always pass you by 186,000 miles per second faster than you.

Michael

#### thebrain13

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##### Re: lights velocity
« Reply #26 on: 27/07/2006 01:19:11 »
I am not talking about light traveling in the same direction as you. I know that light will always pass you at c. However light isn't going to be passing by anything in my example, its traveling perpendicular to you.

My question is what is the speed of light relative to, not when its traveling directly towards or away from you? And before you answer YOU, read the rest of my post.

And lastly you didn't answer what would happen in my experiment. So what would happen, based on what you just said?

#### ukmicky

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##### Re: lights velocity
« Reply #27 on: 27/07/2006 01:58:32 »
quote:
More precisely you could say if light isn't moving directly toward or away from you, it is always seen as moving under c.
No. How do you see it doing anything if its not traveling towards you . if you see it because it strikes something like the contents of a galaxy then your viewing a doppler shifted image of the things the photons hit.

quote:
Originally posted by thebrain13

Quote
I am not talking about light traveling in the same direction as you. I know that light will always pass you at c. However light isn't going to be passing by anything in my example, its traveling perpendicular to you.

once again  for you to see light  in a vacuum, for it to  be viewed and measured  its has got to be traveling towards you and therefore passing you.

Michael
« Last Edit: 27/07/2006 02:45:26 by ukmicky »

#### another_someone

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##### Re: lights velocity
« Reply #28 on: 27/07/2006 02:01:53 »
quote:
Originally posted by thebrain13

Since you no longer view light to be constant if it is not moving directly toward or away from you, how is non c moving light, affected by your relative motion?

How fast would you view light in this case. Lets say you were traveling at .99c relative to a starting point, a flash of light starts from the same starting point perpendicular to your motion at the same time, how fast do you see the light traveling relative to you, and how fast do you see it traveling relative to the starting point?

Now what if you were traveling at .1c?

The problem is that if light is not travelling towards you, you will not see the light, and you will have to infer its presence and speed by indirect means.  If you could clearly construct the complete thought experiment whereby you describe not only what you think the light will be doing, but how you think you would gain information about what it is doing, and then we can look at the total experiment and see what information it will tell us.

George

#### thebrain13

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##### Re: lights velocity
« Reply #29 on: 27/07/2006 02:44:35 »
The beam of light hits particle of dust the whole time its traveling, then it bounces and hits the observer. So it affects the object directly, there you happy? I believe it is completely unnecessary to include that, einstein never had to, and its very silly to imply that if something doesnt directly affect you then it doesnt happen.

#### thebrain13

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##### Re: lights velocity
« Reply #30 on: 27/07/2006 02:54:15 »
ukmikey redshifting wont change its velocity. So how does bouncing off something change the experiment?

#### ukmicky

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##### Re: lights velocity
« Reply #31 on: 27/07/2006 03:06:19 »
quote:
Originally posted by thebrain13

ukmikey redshifting wont change its velocity. So how does bouncing off something change the experiment?

quote:
The velocity of an object is simply its speed in a particular direction. Since velocity is defined as a vector, both speed and direction are required to define it.
http://en.wikipedia.org/wiki/Velocity

What happens to somethings velocity when it bounces and changes direction. What does velocity mean.?

.
Michael
« Last Edit: 27/07/2006 03:33:50 by ukmicky »

#### thebrain13

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##### Re: lights velocity
« Reply #32 on: 27/07/2006 03:34:15 »
what does that have to do with anything?

#### heikki

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##### Re: lights velocity
« Reply #33 on: 29/07/2006 16:39:41 »
quote:
Originally posted by jaybee

heikki,

"Composition of velocities - velocities (and speeds) do not simply 'add'"

Speed mathematical unit is m/s.

Where m is measured distance dimension.

S is time-unit.

When time unit is 1s it is 1s it cannot be anything else.

And if some object,

small or big,

goes some distance x at time 1s,

then speed is x/s.

If x is 500000km/1s then speed is 500000km/s.

If two objects goes same speed at different direction at speed x/s then that separate speed is 2x/s.

So, if these object speed is 500000km/s.

Then separate speed is 2*500000km=1000000km/s.

I cannot use other mathematical detour rules because mathematical rules are simple and scientifical proved.

My thought is that if we thing things what nature has, even parcicle motion or matter-vibrate motion, the both has same nature-laws and these nature-laws dont has constant-speed element. Of cource many things can says it is constant because changes happend so long time or distance that it is not important to known other and ofcource sometimes it is simply to use and compromise constant-value to made things understable and useful us.

#### another_someone

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##### Re: lights velocity
« Reply #34 on: 29/07/2006 16:56:28 »
quote:
Originally posted by heikki
Speed mathematical unit is m/s.

Where m is measured distance dimension.

S is time-unit.

When time unit is 1s it is 1s it cannot be anything else.

But this is the whole essence of relativity – what may appear as 1 second to you, may appear as 10 seconds to someone else, or 0.1 second to another person (all assuming they are in different inertial reference frames).  Likewise, what may appear as 1 metre to you, may be 10 meters to someone else, and 0.1 meters to another.

George

#### heikki

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##### Re: lights velocity
« Reply #35 on: 30/07/2006 07:33:32 »
quote:
Originally posted by another_someone

quote:
Originally posted by heikki
Speed mathematical unit is m/s.

Where m is measured distance dimension.

S is time-unit.

When time unit is 1s it is 1s it cannot be anything else.

But this is the whole essence of relativity – what may appear as 1 second to you, may appear as 10 seconds to someone else, or 0.1 second to another person (all assuming they are in different inertial reference frames).  Likewise, what may appear as 1 metre to you, may be 10 meters to someone else, and 0.1 meters to another.

George

Hi, A_s.

I havent read that mentioned theory of relativity and your wrotes is kind strange for me. When time-meauring unit is 1s it is 1s at all points, everywhere.

But, now i must says goodbay at this forum. It seems that you and other else who speak this forum, have read some theoryes and scient-books and then my thoughts are not same-kind than these books are, so then happend un-necessary different understanding.

I hope you nice life forward.

br. Heikki.

#### ukmicky

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##### Re: lights velocity
« Reply #36 on: 30/07/2006 16:41:12 »
heikki
If you would like to read Albert Einsteins special and general theorys of relativity you can down download it from here.

http://www.gutenberg.org/etext/5001

Michael
« Last Edit: 30/07/2006 16:50:29 by ukmicky »

#### another_someone

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##### Re: lights velocity
« Reply #37 on: 30/07/2006 23:27:42 »
quote:
Originally posted by heikki

Hi, A_s.

I havent read that mentioned theory of relativity and your wrotes is kind strange for me. When time-meauring unit is 1s it is 1s at all points, everywhere.

But, now i must says goodbay at this forum. It seems that you and other else who speak this forum, have read some theoryes and scient-books and then my thoughts are not same-kind than these books are, so then happend un-necessary different understanding.

I hope you nice life forward.

heikki,

Please do not leave simply because there are some things some of us have read that you have not.  The whole point about this forum is to spread the knowledge of science, and if every time someone comes across a theory they have not heard of being mentioned here they depart, it would leave this place fairly empty.

If you have questions – them please ask them.  If there are gaps in your knowledge (and believe me, there are very many gaps in my knowledge, as there is for all of us), then stick around and let us help you fill them.

Over the 9 or 10 months I have been here, I have had many of the gaps in my knowledge filled, and still continue to learn.

George

#### Solvay_1927

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##### Re: lights velocity
« Reply #38 on: 31/07/2006 02:43:26 »
I hope Heikki does come back.

Anyway, if you want a straight answer to your original question, Brain, it's:

The photon would be traveling at c from its starting point.

So if points A & B are 300,000 km apart, then a light ray would take 1 sec to travel from A to B.  And if you're at a point which is perpendicular to the line AB - let's say A is 300000km "west" of B, and you are 300000km "north" of B, then:
The light deflected off dust particles just after leaving A would take 1.4 sec to reach you (i.e. sqrt(2) - use Pythagoras' Theorem) - i.e. you'd see this light at t=1.4 sec;
And the light deflected off dust particles as it arrives at B would take 1 sec to reach you - i.e. you'd see this light at t=2 sec (where t=0 is the time when the light first leaves A).

So it would "appear" to you that the light beam has only taken 0.6 sec to go from A to B, but once you allow for the distances/geometry involved, you'd be able to work backwards to tell that the light beam actually took 1 sec to go from A to B.

#### Soul Surfer

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##### Re: lights velocity
« Reply #39 on: 31/07/2006 19:44:11 »
It is interesting to note that cases of this apparant motion of light faster than the velocity of light have been seen astronomically.

Learn, create, test and tell
evolution rules in all things
God says so!

#### Mjhavok

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• Posts: 468
##### Re: lights velocity
« Reply #40 on: 03/08/2006 05:54:29 »
The speed of light is the same no matter it's direction relative to you. Unless it passes through, off or into something.

I read somewhere that the speed of light constant c has actually got faster since the universe began. Very interesting I have to find that article.

#### The Naked Scientists Forum

##### Re: lights velocity
« Reply #40 on: 03/08/2006 05:54:29 »