Light Speed


Temporal Novice
I had a question, or more a general wondering and I was curious if anyone could explain this to me any better. I'll use an example to illustrate my question.

If you are in some kind of rocket ship traveling at let's say half the speed of light or 150,000 km/s and you pass a friend in another rocket going only 50,000 km/s. The theory of relativity would say that to your friend you only look like you are moving 100,000 km/s. Now that makes perfect sense to me, so I would say everything seems to fit. But it's when the speed of light comes into the picture that things start to get fuzzy.

So you are in the rocket still taveling at the same velocity 150,000 km/s and a beam of light comes upon you and passes you. Now the theory of relativity would say that this light traveling at 300,000 km/s (speed of light) would only appear to be moving at 150,000 km/s to you, but this isn't so. The light still is suppose to appear to be moving at 300,000 km/s to you. This seems like an odd paradox to me. Now I would never presume to say that this can't be so, or that Einstein goofed when he invisioned this. I just don't understand it, and if anyone does would like some clarification
Ok ill break it down and we'll have a look:

OK your on a train moving 50mph and you throw a ball away from you at 20mph,
for an outside observer how fast is the ball moving?
70mph!yes that makes sense,

Now your on a train that is travelling half the speed of light
93,000 mps,now instead of throwing a ball,you turn on a flash light,how fast is the light from the flash light travelling relative to an observer outside the train?

this time it is NOT 186,000mps +93,000mps=279,000mps

NO the light stays constant at 186,000mps! which is the answer,
now if this was mass it would not make sense.

Ok now this time you are on a train again moving at half the speed of light,and you turn on your flash light,
how fast is the light travelling away from you?
again it is moving at 186,000mps

Yes it is a paradox,and now the solution,einstiens equations which you skipped:


Velocity = Distance travelled divided by Time

10 miles an hour= 10 miles/1 hour

20 miles an hour= 20 miles/2 hours

got it? like in your car or whatever,thats how it works out.

What does this tell you?
this suggests in fact that distance travelled always relates to time,it tells us that time and possibly distance aswell is not always the same for all observers.

Distance changes with time as well,a one foot ruler moving in a train thats moving at 186,000 mps would not look like a foot,maybe half a foot or less,and his watch would tick faster.

Now this leads to the problem of going out in to deep space,earth is your observer this time,and you are the rocket that can go 99.9999% the speed of light,off you go to a star 1000 light years away,for you on the rocket everything will be normal,but from earths perspective youll be taking years to get to that destination,youll get there in maybe 1 year,itll take you 1 year to get back,but earth will now be 2000 years older than when you left,youll have aged 2 years.

If you travel at light speed,itll be the same except you wont age at all,but thats not possible.
Not to change the subject but if you think conceptualizing Relativity is tough, think of the practical problems of traveling near the speed of light in the first place. I'm assuming here that you have a handy jet pack with limitless fuel and therefore have the ability to achieve .9999c.

Do you think you could travel over light years and not run into anything? (Its not like you're going to have brakes and a steering wheel to get around space junk). Also interstellar space has a considerable amount of gas molecules in it. As you approach speed c the quadrillions of atoms in your path are going to hit with the force of cosmic rays. Your space ship will melt and vaporize. Maybe that is why the fastest meteors arrive at no more than 1% the speed of light.

Any Star Trek fans want to dispute this?

The way I see it ET had better phone home cause he ain't getting from here to there on a bicycle no matter how hard he peddles.
Well in star trek the ships computer navigates round space debris or whatever.

You are correct though,you cannot steer,which means star treks bollocks,the reason you cant steer or grind to a halt is there is one major thing missing in space:FRICTION
the other is of coarse gravity and heat(except near a sun).

Without friction it is technically impossible to stop,so ok you get to 99.9999% the speed of light,
well you can shut off the engines or whatever it is got you to that speed,but now you got to that speed what is gonna slow you down?,if your not in orbit of anything youre fucked(and at that speed youll just crash),nothing can slow you down cos youre not grinding against anything,unlike on a race track(the ground) and in the air (gravity) in the air there is gravity which pulls to the centre,this is actually slowing the plane down,if it were to just shut off,it will go down.
In space of coarse there is nothing so youll go on a little perpetually.

The other problem is heat,there is none once you are far away from a sun,and it dont matter if youre moving at lightspeed,cos youll freeze to death.

The other real problem is radiation,you see we have an ozone layer,that protects us,in space theres all sorts of dangerous shit,your likely to be bombarded with it.
To clear it up,when your near a sun your getting radiation overdose inc beta and delta(i think),when your away from a sun you freeze.

You also may travel to a sector where a sun is gonna blow up,not nice,like a billion nukes going off in your face.

Communication is impossible cos by the time you get to wherever,everyone at home will be dead.

no one in the universe has got the ability to do this cos the main problem is that they exist in THIS universe and its shitty laws.

If we have been visited by aliens im almost certain they could not have come from this universe,itd have to be a universe where our contraints do not apply,if this was so they would probably be made out of energy and not be visable to the naked eye,for the simple reason there not the same physically either.

If we are visited by a being made out of anti-matter wed all be fucked within a micro second,cos the entire universe would blow up,anti-matter and matter are the same but cannot come in contact with each other or BANG!!!.
<font size="1" color="#FF0000">LAST EDITED ON 23-Aug-02 AT 04:11PM (EDT)</font>


Einstein didn’t simply say that the speed of light is fixed at ~300,000 km/sec. He said that all observers will measure the speed of light to be ~300,000 km/sec regardless of their relative velocity.

I won’t post all the Lorentz Transformations that are involved but you can find them on the Internet on many sites. Look at the simplified transformations – they are in algebra form rather than calculus. The basic part of the Lorentz Transformation that you should see is:

Gamma = 1/Sqrt (1- v^2/c^2).

Gamma is the factor by which time or length is contracted/dilated at a specific relative velocity where “v” is your velocity and “c” is the speed of light.

The transformations tell you that if you are in motion relative to some other observer your clock will appear to that observer to run slower than his/hers and your measuring rod will appear to be shorter than his.

You shoot out a beam of light in the direction that you are traveling. You are traveling at some high percentage of the speed of light and believe that you should measure the speed of light to be c- v (your velocity in the same direction). However, your clock is running a bit slow and your measuring rod is a bit shorter…in fact they are just slow and short enough so that when you measure the velocity of the light the result is still ~300,000 km/sec.

Here’s the thought experiment:

You are coasting toward your friend “The Observer” at .9 c. You both have “perfectly” matched clocks. You send out ten pulses of light one second apart as measured by your clock. The first pulse hits your friend’s receiver and starts his clock. The tenth pulse stops his clock.

You both have “perfectly matched” instruments that measure the velocity of the light. At the end of the experiment you get together and compare notes. You both agree that the speed of light is ~300,000 km/sec. Your clock has ticked off 10 seconds. His, however, ticked off about 23 seconds. So you now disagree on the total time elapsed between pulse 1 and pulse 10 and the distance that the first pulse traveled before the last pulse hit your friend’s clock. You say it traveled 10 light seconds. He says that it traveled 23 light seconds.

Let’s figure the gamma factor for your relative velocity:
v= .9 (decimal of c) – your velocity
c= 1
Gamma=1/Sqrt (.9^2/1^2)=2.29

He measures the interval between pulses as 2.29 seconds and says that total elapsed time is about 23 seconds (10 * 2.29~23 seconds total elapsed time). You reciprocate (literally, 1/2.29 = .44) and say that his clock was running too fast and ticking off “one second” for every .44 seconds has measured by your clock.

You’re both correct in terms of Special Relativity. From his point of view (frame) it did take 23 seconds and the distance between the first and last pulse is 23 light seconds of distance.

You sure do know your math, but I know my history!!!

Did you know that all the lessons that you learned in math are directly related to and originated from the bible?

Like Einstein, we can further back track to Pythagoras and even further to Euclid. He was the man that Created GEOMETRY some 2200 years ago. Its called the Euclid Elements WHICH PRINCIPLES OF MEASURING WERE DIRECTLY TAKEN OUT OF THE HEBREW BIBLE!!! and right under our noses we fail to realize that the very basis of science/math is none less than RELIGION!!!

Euclid was one of the most prominent mathematicians of antiquity. He is still known to every pupil who studies geometry.

Very little is known about Euclid's life. He lived from about 330 B.C. to 275 B.C. It is believed he studied at Plato's
Academy in Athens. He also taught in Alexandria and also founded the school of mathematics and wrote his prizework, "THE ELEMENTS".

The mathematics included Geometry, arithmetic, algebra that where directly studied out of the old testament by Euclid, Archimedes, Menelaus, Pappus and Diophantus.

The Elements are all what is known today about points, lines, angles and simple shapes. Based on Euclid's work of 10 axioms/postulates. From these ten axions he built up the Geometry which is still taught today in school.

Its interesting to note that although the name "Euclid" and the word "Geometry" have often been used to mean the same thing for centuries.

Centuries later the word geometry began to appear on the title page of book. The first edition in English, published in 1970, had the word in its title, which was the ELEMENTS OF GEOMETRY OF THE ANCIENT PHILOSOPHER EUCLID MENGARA.


You get no argument from me on your post. It's not lost on me that science and philosophy have the same roots - the attempt to answer who are we, where did we come from, where are we going and why? Are not those the very questions that we ask of Him?

Real science is built upon the foundations laid one step at a time throughout the ages. Without Euclid - no geometry. Without geometry the Greeks would have never measured the size of the Earth (Hmmm....geo-metry).

In any case, great post. Thank you.