If I could travel at the speed of light

[glenc]

If I could travel at the speed of light (9,461,000,000,000 km per year) it would take me:

0.13 seconds to travel once around the Equator
1.3 seconds to reach the Moon
8.3 minutes to reach the nearest star, the Sun
4 hours to reach Neptune, the Sun’s outermost planet
4.3 years to reach Alpha Centauri, the nearest star, apart from the Sun
370 years to reach the bright open star cluster Pleiades (M45)
710 years to reach the Helix planetary nebula, a dying star (NGC7293)
1,350 years to reach the Orion Nebula (M42)
15,800 years to reach the globular star cluster Omega Centauri (NGC5139)
25,900 years to reach the black hole in the middle of our Milky Way galaxy (Sgr A*)
100,000 years to cross our Milky Way galaxy
157,000 years to reach the small local galaxy the Large Magellanic Cloud (LMC)
2,540,000 years to reach the large local galaxy in Andromeda (M31)
2,400 million years to reach the bright magnitude 12.9 quasar 3C 273

All of these are visible in binoculars or a small telescope except the black hole, but don't look at the Sun.

[renormalised]

If I could travel at the speed of light (9,461,000,000,000 km per year) it would take me:

11 minutes to run into a piece of debris in the Asteroid Belt and then everything else would be moot:):P

[adman]

...and at that speed it wouldn't be pretty!

[sally1jack]

And the last thing to go through your mind would be ???:shrug: it's an oldie i know:D

[leon]

Very interesting stuff, thanks.

Leon

[renormalised]

The rocket nozzle at the back of the ship:):P

[asimov]

LS seems pretty damned slow when you look at it this way hey! I'm not greedy & only want to get out of the atmosphere so's I can do some decent imaging..!

[scagman]

If I could travel at the speed of light (9,461,000,000,000 km per year)

I'd still be late everywhere

[Steffen]

Travelling at the speed of light can really ruin your weight-loss program, too.

Cheers
Steffen.

[renormalised]

Only in the eye of the beholder....you'd still weigh the same as usual according to yourself:)

[Steffen]

You are too kind :)

Cheers
Steffen.

[Ric]

There a some massive distances in the Universe even at light speed.

Where's Scotty, we need warp 9

[sheeny]

Ah... well if you going to be like that then...

The times Glen quoted are only for a "stationary" observer. The actual time that Glen would experience is zero!

;)

Al.

[multiweb]

And they'd find a way to put interstellar speed cameras. :P

[Archy]

If you could travel at the speed of light, it would take you no time at all, after reaching that speed, to travel anywhere in the universe.

[qld]

:lol::lol::D
red shift makes you travel faster

[Paduan]

At that speed would my headlights work? Being space it is pretty dark!

[thunderchildobs]

[QUOTE=glenc;753338]If I could travel at the speed of light (9,461,000,000,000 km per year) it would take me:

2,400 million years to reach the bright magnitude 12.9 quasar 3C 273

QUOTE]

With the quasar moving away from us, 2,400 million years would leave you a little bit short . (I'll let others do the math).

[glenc]

Thankyou for all the corrections! This is supposed to be for beginners!
Yes, strictly speaking I should say the light takes that much time to reach us from each of these objects.

[renormalised]

Once you start to get out around cosmological distances, the distances quoted start to become problematical due to time dilation, redshift and spacetime curvature. Several different ways of measuring distance are employed.... light travel time, light travel distance, comoving/proper distance, cosmological proper distance, angular size distance and luminosity distance. They all give different answers as to how far away an object is, with luminosity distances giving the largest of all the values that can be ascertained.

[Paduan]

the faster that you travel, time apparently travels slower from .9 C onwards anyway. So at the speed of light you could be every where yet nowhere. all of your friends not with you will age roughly 100 yrs per your day. not to mention that at 10g (9.8 m/s/s) it would take roughly 5 yrs to get to such a velocity anyway... but remember that the speed of sound was impossible not 50 yrs ago


P.S. do not quote me on the numbers as i am rounding from memory for "shock" value

[leonie-macaroni]

But you would be massless anyway, and nobody likes massless friends.
Photons and gluons pass me by constantly and I mostly just ignore them.

I suppose they could be friends with each other, but as stated earlier that theoretically travelling at C will cause no time for the traveller to pass at all, I would guess that they haven't met yet.
:sadeyes:

[Mliss]

Thanks for posting that Glen. :)

For a noob that's about as much as i can handle :P
Puts a real perspective on how tiny we are, and how much space is in.. space!

I can't keep up with you guys and my head can't cope with time dilation, redshift and spacetime curvature :exploding head emoticon: :lol:

[renormalised]

Actually, the moment you begin to move, time starts to slow down for you, relative to an observer at rest to you. It's imperceptibly changed at first, but the closer you come to "c", the slower it becomes.

At the speed of light your own time, from your perspective, remains the same, but a stationary clock's time speeds up to the point where, theoretically, all of time outside of your ship passes almost instantaneously. It's the same effect you get when you reach and pass over the vent horizon of a black hole. The opposite effect happens for the stationary observer looking at your clock. At "c", you clock from their perspective, stops. Same when an object approaches and passes over the EH of a BH. From your PoV, it never crosses. That's time dilation for you:)

[renormalised]

Actually, if you were a photon, gluon or graviton, you would be massless, but not for the reason you're thinking of. The velocity of the particle (in this case bosons, or force carrying particles) does not dictate the mass of the particle. That has to do with the way particles couple with the Higgs Field, and since these bosons don't couple to this field, they're massless...no matter (pardon the pun) what velocity they're doing. The only bosons that have any mass at all are the W and Z particles, which intermediate the weak nuclear force responsible for radioactive decay. They cannot travel at "c".

[glenc]

Thanks Mel. This was intended to be for beginners.

[pmrid]

But since light would also be travelling towards you at the same speed, would you seem to be travelling at twice that speed (relative to that light source)?
Peter

[renormalised]

No, the speed of light is a constant, no matter what situation you find yourself in. So if you were traveling at c and were being approached by a light source traveling at c in the opposite direction, your closing velocity would still be c, not 2c. Whilst traveling through space, the speed of light cannot be exceeded in any way, shape or form.

[pmrid]

The operative word there was "seem" or "relative" - or whatever I said. While light is not traveling faster than C, it appears to be - just like an approaching car on the highway. No??
And what about Doppler shift - I'm approaching so it should shift to blue. It's approaching me also, so it should also shift to blue. So in combination, the combined blue shift would put it outside the visual spectrum anyway - Yes/No/Maybe?
Peter

[renormalised]

Light can only travel at c, whatever c is in the medium within which the light is traveling. Be it a vacuum or a bowl of jelly.

The answer to your question is still no....c is a constant. To change the equations to get 2c, you would have to change the constancy of the speed of light, which you can't do. As I mentioned before, your example doesn't produce a "2c" result, whether that's "seems" or "relative" to anything you or the other object is doing.



You will appear to blueshift to it and it to you. And the answer to the second part of this question is No. You will only see it blueshifted by the amount it attains depending on its velocity of approach. There is no combination of "blueshifts" to give you an ultraviolet spectrum. You will only see the light of the object as it approaches you being blueshifted.

[Mliss]

:einstein::einstein::scared3: :einstein::einstein:


Glen, what have you started? :lol:

i'm really trying to grasp this, (don't like my chances) but it's a really interesting read! so many talented people in here!

[The_bluester]

I am not so sure about that. Maybe it wouldn't be pretty, but it would at least be pretty spectacular!

[pmrid]

OK. I'm struggling here.
Photon A and I both leave our respective destinations at the same time, heading towards one-another. At the point of departure we are, say, 5 light years apart. Our relative starting positions.

After 1 year, I have travelled a light year towards the source of photon A. In the same year, Photon A has travelled a light year in my direction.
At the end of year 1, we are therefore 3 light years apart, not 5. To my observing eye, hasn't the distance between us reduced at the rate of 2 light years/year?

Peter

[Brian W]

And from another perspective when we look at those distant objects we are actually connected to an uninterrupted energy transmission that originated with the object we are looking at.

Which means that an energy source that includes me is also traveling at the speed of light.

As i have often said my telescope allows me to travel at the speed of light with no fear of a speeding ticket!
brian

[sjastro]

An understanding of special relativity is required here.

At very high velocities approaching and including the speed of light (=c), velocities don't add vectorially.

For example if two objects approach each other at a velocity v, then their approach velocity relative to each other is 2v.

At high velocities their approach velocity is 2v/(1+(v/c)^2)

If each object (photon) approaches each other at a speed c, then the
approach velocity is 2c/(1+(c/c)^2)= c

Regards

Steven

[pmrid]

I am going to have to take that on faith alone. It sounds like fancy bookeeping to me I'm afraid.
Peter

[sjastro]

The derivation of the formula is simple, straightforward and logical.:thumbsup:

Regards

Steven

[scagman]

I've given up triing to grasp it, I have enough trouble keeping a grasp on reality.


So if I was on a really really big train(t1) travelling along the tracks at the speed of light, and inside that train there is another train(t2) travelling along a set of tracks running down the center of the really big train, also travelling at the speed of light, what speed is the inside train(t2) going in relation to someone watching from outside the big train?

Now to me it should be travelling at 2*c but I know its not because you cant go faster than c.

Now you could complicate matters further and have a really really small train(t3) in side the not so big train(t2) also travelling at the speed of light and so forth and still none of the trains would be going faster than c.

:)

[glenc]

Should I rename this thread Einstein's theory of relativity? :)

[leonie-macaroni]

Are you implying that if static, they remain massless? Or differ in mass?

Where can I learn more about particle physics?

I'm getting a bit lost, but this is all so interesting.

:thanx:

[pmrid]

I have no problem working the problem and see how it produces the result "c". But it is still keeping me awake.
If, instead of my travelling at c, I am accelerating towards c. As I continue to accelerate and reach high velocities, my approach velocity reduces as the effect of that formula kicks in????
Peter

[renormalised]

They're massless in all cases, whether they're at rest or moving. The only bosons that have mass are the W and Z bosons. This is because they gain mass via their interaction with the Higgs field.

However, hold the announcement for the present....the Higgs mechanism might not yet exist, if they don't end up finding the Higgs boson itself.

Just look up special and general relativity, higgs boson, higgs mechanism, quantum mechanics and such on wikipedia. That will give you a brief intro of the subjects in question. If you want books about these subjects, let me know and I'll see what I can find that you'll be able to follow without having to go get a degree:):P

[leonie-macaroni]

Thanks Carl!
:atom:

Expect questions from me in the future! ;)

[sjastro]

To understand things that accelerate, special relativity is no longer relevant and one needs to look at general relativity instead.

If we accelerate up to a particular velocity and stay at that velocity, the formula is applicable where the velocity is constant.

The formula is applicable for all constant velocities, it's just the effects of the formula are not observable at slower velocities.

If you look at the formula there is a (v/c)^2 term. For an object travelling at 100 km/hr, the (v/c)^2 term equals 3.21 X 10^-11 which being a very small number for all intents and purposes equals zero.
For small velocities we can take the (v/c)^2 as equalling zero, then our formula reduces to the familiar approach velocity 2v.

If the object is travelling at say 0.9c the effects of the formula are much more noticeable. The (v/c)^2 term is now equal to 0.81. At 0.9999c (the speed of protons at the LHC) it becomes 0.9998.

So as you travel at higher constant velocities the effects become increasingly apparent.

Regards

Steven

[glenc]

How long does light take to reach us from various objects?
At the speed of light (9,461,000,000,000 km per year) it takes light:

1.3 seconds to reach us from the Moon
8.3 minutes to reach us from the nearest star, the Sun
4 hours to reach us from Neptune, the Sun’s outermost planet
4.3 years to reach us from Alpha Centauri, the nearest star, apart from the Sun
370 years to reach us from the bright open star cluster Pleiades (M45)
710 years to reach us from the Helix planetary nebula, a dying star (NGC7293)
1,350 years to reach us from the Orion Nebula (M42)
15,800 years to reach us from the globular star cluster Omega Centauri (NGC5139)
25,900 years to reach us from the black hole in the middle of our Milky Way galaxy (Sgr A*)
157,000 years to reach us from the small local galaxy the Large Magellanic Cloud (LMC)
2,540,000 years to reach us from the large local galaxy in Andromeda (M31)
2,400 million years to reach us from the bright magnitude 12.9 quasar 3C 273

[renormalised]

And 42.5 billion years from the observable edge of the Universe:)

[Mliss]

http://www.bbc.co.uk/news/science-environment-15017484

thought this may be of interest :P

[renormalised]

Already in the Science Forum:):)

[Paduan]

the formula is sound however advanced mathematics is like a poll you can get it to reflect the view of the individual balancing the equations. i am not intending to call anybody a liar but this previous statement was proven to me by my mathematics teacher in yr 10 where he proved using calculus that 1 can equal 0. now we all know that to be false yet mathematically it is possible. Einstein was a genius who told the world that "c" was the ultimate velocity of matter, yet just the other day nutrinos were accelerated faster than light. however mathematically it is impossible.
Physics and mathematics are like a beautiful object, held with great stead the eye of the beholder!

[Paduan]

before anyone points it out yes i know that it is a problem with the math i was just using it as an example. 1 cannot equal 0 yet to the uninitiated it seems true which was my point. and i agree with you Peter i believe that the resultant distance is 3ly however neither particle exceeded "c"

[sjastro]

You are way off base.
This is the sort of comment made by people who do not understand mathematics.
Using calculus to prove that 1=0 either indicates that your teacher was pulling your leg or is a mug who shouldn't be teaching mathematics.

On the subject of neutrinos travelling faster than light is still pending investigation, many scientists are of the opinion that the experiment is flawed.

Regards

Steven

[Poita]

Are you referring to:
Let x = 0
.. x(x - 1) = 0
.. x - 1 = 0
.. x = 1
.. 1= 0

Hidden divisions by zero are often used as a trick to catch the unwary, the above uses that cheat, and so is invalid.
Your teacher was probably proposing it, hoping you would find the hole in the 'proof'.
There is another similar 'proof' that 1 = 0 using the indefinite integral that has a similar hidden division by zero, but also looks at first glance to be correct.

[Paduan]

if you notice i replied to my own post. i do know that it is flawed and maybe it was a bad example but history is full of mathematical indescrepancy which is the point i was trying to make. as for the nutrino's they do not have Einstein telling them that they are moving too fast. as i remarked in a previous post. It was not too long ago we (the human race) believed that the speed of sound was an impenetrable BARRIER

[sjastro]

The argument that one uses "history" as a case to establish flaws in mathematics pertaining to current theories is a logical fallacy.

In fact if you use history as a guideline you will find that most theories fall by the wayside as observations or experiments do not match up with the predictions made by the theory. Very rarely are theories rejected because of any discrepancies in the maths. The application of the maths may be wrong but the actual maths itself isn't wrong.

When did Einstein say things couldn't travel faster than light?
What Einstein specifically stated was that objects in space cannot exceed the speed of light.
Expanding space itself can exceed the speed of light as is found with the recession velocities of distant galaxies.

Finally the areodynamic speed of sound barrier was not considered a theoretical barrier that could not exceeded.

Regards

Steven

[renormalised]

That's the big problem....everyone has been laboured under the impression that Einstein said nothing can travel faster than light, period. No matter what the situation and that has been a thorn in the side of physics (especially in the public conscience of the field) for many years. You even hear scientists proclaim it loud and clear for all to hear. But as Steven has mentioned, that's not what Einstein actually said. It's about time people learn about it and stop parroting everyone else before them.

[Poita]

I found this a fun read:
http://www.weburbia.com/physics/FTL.html

[Brian W]

Finally the areodynamic speed of sound barrier was not considered a theoretical barrier that could not exceeded.

Regards

Steven[/QUOTE]

Steven not to hijack the thread but could you expand a bit on the above. You have emphasized 'theoretical' and that to me means you are using the word pointedly.

However, as I understand the history... the whole point of the American program was to find out if it was possible to break the sound barrier. they thought they could but they did not know they could.

As no one knew the answer and the whole program was developed to find the answer it seems to me that they had a theory and they tested it?

brian

[Poita]

The program wasn't to see if the sound barrier could be broken, it was already known that many items broke it, the program was setup to see if a controlled vehicle (e.g. a piloted jet) could break the barrier and maintain control.
The aim was to be able to make fighters/bombers etc. that could fly supersonically, not whether the barrier could be broken at all, that was already common knowledge.

[sjastro]

Brian,

A theoretical barrier is a fundamental barrier imposed by the "laws of nature" and cannot be overcome by technological considerations.

The speed of sound barrier clearly does not fit this definition. Bullets for example could exceed the speed of sound before an aircraft was developed that could do the same.
In this case the speed of sound was a technological barrier that was eventually overcome.

The debate is whether the speed of light is a fundamental barrier or a technological barrier. Based on current observations it would appear to be the former.
Particle accelerators can accelerate protons up to 0.9999c.
There is a law of diminishing returns. As you increase the amount of energy to accelerate protons, the corresponding increase in proton velocity becomes progressively less.
To accelerate protons up to speed c requires the expenditure of an infinite amount of energy.

Regards

Steven

[Paduan]

My statements are being taken far too literal. i am not here to make any body hot under the collar as a few seem to be getting nor am i going to continue the "argument" all i am trying to say is "HAVE AN OPEN MIND". i am not attempting to hassle anybody's intelligence, career path or beliefs.



BY the understanding we have using todays Physics, velocities at "c" and above are impossible. We have come so far in the last hundred years imagine what we will "KNOW" in a hundred years from now

[Brian W]

Thanks Steve and Peter, I corrected a misunderstanding on only the second day of my 60th year... could be a great year
brian

[renormalised]

No they're not. You haven't been listening (or reading as the case may be). Velocities above "c" are not impossible. As a matter of fact they're quite acceptable in the terms of SR. In fact, astronomers measure relative velocities much greater than "c" nearly everyday with distant galaxies (anything with z>1). What cannot be attained in any way, shape or form for ordinary matter moving through space, is "c". There's nothing stopping matter moving with space, or outside (i.e. higher dimensions, wormholes etc) of it, traveling at whatever velocity it likes. It's the traveling through space at "c" which is the hard part. It has to do with mass and inertia (Higgs Field etc). The reason why photons travel at "c" is they have no mass, therefore no inertia. A photon can stop instantaneously to a halt, an electron (for instance) can't. All bosons (force carrying particles) can travel at "c", except W and Z bosons (which have mass). All massless particles can also instantaneously accelerate to "c", as well.

Tachyons must always travel faster than the speed of light, just as particles of ordinary matter must always travel slower. As I mentioned previously, to make a tachyon go faster, you make it lose energy...they have imaginary mass and negative proper time as properties. Losing energy for these particles is akin to gaining energy for ordinary matter. At E=0, v=infinity for tachyons....when E=infinity, v=c for ordinary matter (E=infinity, v=0 for tachyons).

[Brian W]

[QUOTE=renormalised;769717]No they're not. You haven't been listening (or reading as the case may be). Velocities above "c" are not impossible. As a matter of fact they're quite acceptable in the terms of SR. In fact, astronomers measure relative velocities much greater than "c" nearly everyday with distant galaxies (anything with z>1). What cannot be attained in any way, shape or form for ordinary matter moving through space, is "c". There's nothing stopping matter moving with space, or outside (i.e. higher dimensions, wormholes etc) of it, traveling at whatever velocity it likes. It's the traveling through space at "c" which is the hard part.

Ok Carl, if i understand the point... scientists have clocked distant galaxies at faster than the speed of light. Therefore if one of these speed demons headed our way and passed close to us or even through us and we orbited our starship around one of the galaxies planets or suns or whatever, we would be traveling faster than the speed of light in relation to other galaxies but not faster than the speed of light in relation to the speed demon galaxy?

Brian

[renormalised]

[QUOTE=Brian W;769719]

No.....it is the expansion of space which is driving it at that speed, relative to our own position with that galaxy. If you were to orbit a planet in that galaxy and/or observing home from the surface, looking back towards us, we would be moving faster than "c" with respect to them. If that galaxy was in our local neighbourhood, it wouldn't be moving at the speed it does. It's not moving through space faster than "c", it is being carried along by space faster than "c" from our point of view. The galaxies themselves actually move through space at speeds of several 100kms relative to one another locally, sometimes upto several 1000kms in dense clusters.

[glenc]

Please start a new thread under astronomy and amateur science to discuss the speed of light etc.

[glenc]

http://theconversation.edu.au/long-way-to-the-chemists-a-rough-guide-to-distances-in-the-universe-2154
“Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.” Douglas Adams, The Hitchhikers Guide to the Galaxy

[renormalised]

It's actually |-----| this big:):):P:P

[brian nordstrom]

:sadeyes:
Would be cool but as' Einstien 'says at the point of reaching the speed of light , and if you had mass to start with , your mass would be infinate , eg you would weigh MORE ! than the entire universe !!!!:eyepop:,,Woaw! So in theory you would be the universe so to travel any where in that universe would take you ZERO Time . Instant travel to any piont you wanted ! . so yea light speed is the cosmic speed limit .Bummer but hey? ....
COOL ! lets do IT! :question:
Brian.

[brian nordstrom]

:shrug: No body dreams at the speed of thought ?
Beats light hands down .
See you there.:hi:
Food for .....?
Brian.

[brian nordstrom]

:thumbsup: Dean Martin ,,, "Come fly with Me?" ...

[leonie-macaroni]

There is an art, it says, or rather, a knack to flying. The knack lies in learning how to throw yourself at the ground and miss. Pick a nice day, [The Hitchhiker's Guide to the Galaxy] suggests, and try it.

Relevant? I think so.:P

[brian nordstrom]

:thumbsup: so long as you dont miss the ground? :question:
What ground ..... Ohh , that one ,:lol: the one I hit when I rolled off the bed .
Brian.