the speed of light = 299 792 458 m / s???????

i appolagise for any spelling/grammar mistakes, had to get it down before i forgot.

i was at work today and my mind starting wondering, as it usually does. for some reason i was thinking about the speed of light, i think i got there by first thinking about space travel, but anyway, i digress...

i was thinkning about the staement that nothing can travel faster than the speed of light, and then i got to thinking about how we measure speed and something hit me, the speed at which something is travelling is relative the the person taking the measurement.

eg.
im sitting in my car - the distance between me and my car is closing at a rate of 0mph, im moving 0mph
im driving to work - the distance between my car and work is closing at a rate of 40mph, im moving 40mph
both my car and my work are on earth - the earth is circling the sun at about 66,648mph, im moving 66,688mph
our solar system is orbiting a blackhole at the center of our galaxy
our galaxy is in and expanding universe........ you get were im going with this

how fast i am moving is entirely dependent on where you are taking the measurements from.

so if we say that speed is relative to the observer then how can we observe the speed of light from a truely stationary position?

also, wouldnt our measurement of the speed of light change depending on if we were moving away from or towards the source of said light?

let me chuck a quick hypathetical question at you (assuming i get more than just one or two visitor to this particular thread)

lets say that we are travelling on a ship, at the speed of light (hypathetical remember), if we were travelling away from a light source at the speed of light then the distance between us and the photons travelling through space would not change, so that light would appear to be stationary.
on the flip side, if we were travelling towards a light source at the speed of light then the distance between us and the photons travelling through space would close at twice the normal rate, so that light would appear to be travelling at twice the 'speed of light'.

so, in conclusion, if speed is relative to the observer, the speed of light cannot be pinned down as 299 792 458 m / s

what are everyones thoughts on this, or did i just write down a load of nonsense, i swear it made sense in my head.

I understand where you are coming from...

I have wondered this myself when it comes to our universe. It seems to me that our understanding is hindered by the belief that nothing can exceed the speed of light, as this is objective to our perspective. claims that our universe is expanding increasingly torwards the speed of light, however if our universe is expanding beyond the speed of light, we would never know as those particles of light at the edges would never be visible to us in conventional ways. this also accounts for why it appears that we reside at the center of our universe. if we were to position ourselves somewhere a million light year from earth, our perspective would change and our observable universe would be much different than what we can see from our Sol bound point of view.

I'm thinking that you forgot that you would have the knowledge that the light travelling towards you would be going at light speed hence you would only need to include that in your calculation to pin down the speed of light.

Maybe I didnt understand your question coz that seems to simple

reply to post by DaveNorris


I had the same questions. These two videos explained it to me 110%. Hopefully you will get it in a snap like I did by watching these.

Steven Hawking Train Ride

AND

Einstiens Big Idea

You have arrived at one of the problems which led Einstein to develop the theory of special relativity.
The speed of light is not relative. It is the same no matter what the frame of reference.

Weird, huh?

Originally posted by DaveNorris
so if we say that speed is relative to the observer then how can we observe the speed of light from a truely stationary position?

Using our own light source, such as a laser instead of "unknown" or celestial light.

also, wouldnt our measurement of the speed of light change depending on if we were moving away from or towards the source of said light?

Same as above. The speed of light is a constant and I daresay someone good at maths could use it to calculate our speed through the solar system, galaxy, universe.

let me chuck a quick hypathetical question at you (assuming i get more than just one or two visitor to this particular thread)

lets say that we are travelling on a ship, at the speed of light (hypathetical remember), if we were travelling away from a light source at the speed of light then the distance between us and the photons travelling through space would not change, so that light would appear to be stationary.
on the flip side, if we were travelling towards a light source at the speed of light then the distance between us and the photons travelling through space would close at twice the normal rate, so that light would appear to be travelling at twice the 'speed of light'.

This is my (limited) understanding also. There is also something called red shift and blue shift, the light exhibits a different shade depending if it is approaching or traveling away from us.

so, in conclusion, if speed is relative to the observer, the speed of light cannot be pinned down as 299 792 458 m / s

I think the last one is incorrect but as I'm not a physicist I can't quote you things out of my head.
ETA I see one answered you already though. Hopefully he's still reading and will point out my errors too.

thanks for the replies.....

VoidHawk, my whole question hinges on the idea that speed is relative to the person taking the measurements, we all know the earth is moving through space but we dont include that when we are measuring how fast our cars move.

Vandettas, thanyou for the links, i will watch them when im at my pc (im on my phone atm)
and i will get back to you when i have watched them.

I thought about this theory once,
nice thread

Originally posted by DaveNorris
also, wouldnt our measurement of the speed of light change depending on if we were moving away from or towards the source of said light?

The speed the light travels? No. The frequency? Yes. Moving to or away from the source of light adds energy but that energy is is manifested in the frequency of the wave and not it's veloicty.

Originally posted by DaveNorris
thanks for the replies.....

VoidHawk, my whole question hinges on the idea that speed is relative to the person taking the measurements, we all know the earth is moving through space but we dont include that when we are measuring how fast our cars move.

Vandettas, thanyou for the links, i will watch them when im at my pc (im on my phone atm)
and i will get back to you when i have watched them.

As Phage said, light always travels at the same 186,000 miles per second regardless of the inertial frame of reference of the observer doing the measuring.

It sounds counter-intuitive but its been proven time and again to be empirical fact over the last hundred years.

Watch the videos linked by ATS member Vandettas when you can, they are reasonably brief and answer your question as well as is possible without demonstrating the math.

reply to post by Vandettas


maybe im being dense, but that made no sense to me.
the speed of light is the top speed in the universe and if anything might break that top speed then time slows down to protect prevent it, that just confuses me more, it seems so counterintuitive

reply to post by DaveNorris


we think and see in 3d our physics knows only 3d, if we could move to 4 5 6 dimensions in thought and process we would know the answer to a lot more questions

Originally posted by Phage
You have arrived at one of the problems which led Einstein to develop the theory of special relativity.
The speed of light is not relative. It is the same no matter what the frame of reference.

Weird, huh?

edit on 6/23/2012 by Phage because: (no reason given)

Thanks, Phage. I was afraid I would have to explain that one since I have the physics minor. Yeah, this is actually something we go over in class. So good job thinking of it yourself, OP!!

reply to post by DaveNorris

im sitting in my car - the distance between me and my car is closing at a rate of 0mph, im moving 0mph
im driving to work - the distance between my car and work is closing at a rate of 40mph, im moving 40mph
both my car and my work are on earth - the earth is circling the sun at about 66,648mph, im moving 66,688mph
our solar system is orbiting a blackhole at the center of our galaxy
our galaxy is in and expanding universe........ you get were im going with this

If you are driving at 40 MPH, then that's the speed your tires are traveling over pavement. It doesn't matter how fast the earth is spinning on its axis or how fast it's orbiting the sun. If an observer from a point in space could see you, he could mark a point where you were, and then mark a point ahead of you and then, using time, he could determine that you are traveling at 40 MPH.

good job thinking of it yourself, OP!!

my heads full of stuff like this, still cant quite grasp the fact that the speed of light is a constant, its so counter intuative, will have to read up on my physics i suppose

Thanks op, these sorts of questions are great.
What I found interesting is how the speed of light is a constant, when scientific experiment has managed to reduce it?

reply to post by zilebeliveunknown

The speed of light is constant in a vacuum. The rate of propagation of light through a material is not.

what if einstein lied.

there are only a handful of people in the world who truly understand einsteins theory of relativity. so in theory, 99.9999% of the population, over 7 billion people, are essentially just taking some one else's word on it.

what if einstein was some how deceived, and he put this artificial speed limit, to stop mankind from exploring space.

he says nothing can travel faster than light because it would need infinite energy. what if this is just a lie.

what if we found an infinite power source. then one half of the problem is solved.

he says that as an object approaches the speed of light, its mass would be infinite.

in space, an object has essentially zero mass. you can "lift" up an elephant as easily as a pen.

you weigh just as much as a light wave in the vacuum space. so "mass" in the sense of the power to move an object is irrelevant.

gravity affects mass in space. if you can counter act those effects to zero, then the part of the theory that says an object has to have a zero mass to travel the speed of light, is technically solved.

if that part is true. which is the whole point.

side note. how does a flashlight work. a duracell battery is hardly an infinite power source, yet it is able to power light waves to 299792458 m/s.

but on the same note, astronauts don't turn on a flashlight in space and propel themselves to zeta reticuli. or do they.

ufos have been known to accelerate in a instant leaving a trail of light. so maybe light is a method of propulsion.

Originally posted by DaveNorris
thanks for the replies.....

VoidHawk, my whole question hinges on the idea that speed is relative to the person taking the measurements, we all know the earth is moving through space but we dont include that when we are measuring how fast our cars move.

The speed of light is not relative to the observer. No matter how fast you are traveling, light will always travel at 164,000 MPS. If you could travel at the speed of light while traveling TOWARDS a light source, it might LOOK like the photons going past you are traveling at twice the speed, but it would be an optical illusion.

Just my opinion.

reply to post by randomname

in space, an object has essentially zero mass. you can "lift" up an elephant as easily as a pen.

Mass is not the same thing as weight. Mass is a property of matter. Weight is the measurement of the force of gravity acting on a mass.

An object in freefall (like a skydiver or an orbiting spacecraft) is weightless but it is not massless.

"What if Einstein lied?" Seriously? It's possible he was wrong but no one has managed to disprove him yet. All they manage to do is prove him right.