The Last Physics Question - Hopefully

[Kristofor]

Well, it's always possible that we'll come up with something better in the future, (ie relativity replacing Newtonian mechanics) but for the time being both special relativity and general relativity are very well accepted, and have been demonstrated for decades.

One of the most commonly mentioned modern examples is the GPS system. To determine your precision requires knowing extremely precise times and time differences. GPS positions would diverge from accuracy by something like 10KM/day if they were building the system they hadn't corrected for both the motion impact (special relativity) and our location deeper in a gravity well than the satellites (general relativity).

[Wood_workur]

R U sure that is right? Light would be traveling at 300,000km/sec + 300,000km/sec(.90). Or am I totally wrong on this?

It depends on the viewpoint - a person not in the vehicle would see them move at the speed of light. You would see them move at .1x the speed of light.

EDIT: I take that back, you would also see them moving at the speed of light, but because your speed at .9x the speed of light, you would catch up to the waves at a speed of .9x the speed of light.


but the more interesting part is that light waves do resemble a sine graph. When you are traveling at the speed of light, the light waves would compress as you move forward, as in the dopplar effect. Now, once the light waves compress beyond the visable spectrum, and move through ultraviolet, x-ray, and finally gamma rays, whould would kill you, unless you surronded yourself/the lights in water, which would block them.

Effectivly, you are commiting sucide by turning on the lights at the speed of light.

[TK421]

What you would see when you turn on your head lights if you could go that fast? The same thing you see now. Postulate II of Einsteins' special relativity states(basically): the speed of light in a vacuum always has the same value in all diffrent inertial frames of reference.

If some one standing on earth could actually see you turn on your lights as you came whizzing by so fast they would see the same thing you see if car going down the road turns its lights on.

It can be hard concept to grasp.

Mathmatically it is a matter of relativistic vector addition (straight line).


u = v + u' / 1 + (vu'/c^2)

where v = velocity of object 1 w/respect to observer
u' = velocity of object 1 w/respect to object 2
u = velocity of object 2 w/respect to observer
c = speed of light
and velocities are in fraction (percent) of c

In our case v is the speed of your car w/respect to observer, u' is the speed of the light out of your headlights w/respect to your car, and u is the speed of the light out of the headlights w/respect to the observer.

Example

Your in your car going along at lets say 90% of the speed of light (.9c)
and you fire a photon torpedo that goes at 60% of the speed of light (.6c)
Will the torpedo 'break' the speed of light?

u = .9c + .6c / 1 +((.9c)(.6c)/c^2)

= 1.5c / 1 + (.54c^2/c^2)

= 1.5c / 1.54

= .974c

pretty close but not quite.

Hope this helps! Yes, I am a physics major.

[Texas splinter]

Aww, you guys are looking at this all wrong. The answer depends on whether the car has side air bags and electronic stabilization control. Also, it could depend on the number and position of the cup holders in the back seat. ;~)

[Russianwolf]

I drive a 37 year old jeep with a 3 speed transmission. It will barely do 70mph, so this problem doesn't apply to me.

[gsmittle]

Using the Heisenberg Uncertianty Principle, we find that I have no idea how fast the light would go. My hunch is that since we use the speed of light as a unit of measure, the light is going the speed of light.

Thanks a lot. I've laid awake more than one night pondering this.....

g.

[gsmittle]

What you would see when you turn on your head lights if you could go that fast? The same thing you see now. Postulate II of Einsteins' special relativity states(basically): the speed of light in a vacuum always has the same value in all diffrent inertial frames of reference.

[Bunch of incomprehensible math deleted.]

Hope this helps! Yes, I am a physics major.

My head hurts.

g.

[jwaterdawg]

Some of this science stuff I wonder about. The whole doppler effect about color shift and they can tell if the start is moving towards or away etc....I just seen in the news a black hole ate a star.....More mumbo jumbo...Most of the people making these claims think we came from monkeys and the big bang created the universe..No offense if you believe that....
Now as far as some of this stuff they claim to "see" is just an ultraviolet burst in the case of the black hole eating a star....
Even carbon dating....If we have a machine that can carbon date something you calibrate it.....You take something a known age and if it measures correctly I assume it would pass...well whats the oldest known sample age we can use to calibrate the machine??? And I know carbon deteriorates at a certain rate (so they say) but how do we know it always has??? Maybe God changed something along the way..Why did people stop living hundreds of years? I dang sure don't believe the earth or universe is trillions of years old......
Anyhow I don't think the headlights would produce light like they do on the at highway speeds (overdriving your headlights) just like a jet flying faster than the speed of the bullets from their guns..They can fire them but they better move or they will fly into them..But then again bullets slow down....Light doesn't..It just reflects or gets absorbed unless it changes medium at which point it can change speed..Right???

Since I don't want to bring in religion I'll try to focus on the science (at least as we currently know it). The problem is that the people who argue most strongly on both sides (ultra-science/anti-religion vs ultra-religion/anti-science) generally have no clue about what they are talking about. They argue against the other side without a full appreciation of the "evidence" on both sides.

Onedash, please don't take this an attack on you, it's not. I myself am very religous (I hope I'm not breaking a rule here) but I am also highly trained scientifically. Those two things are not incompatible for me; in fact the science (which is really just an incomplete mathematical description of something we don't fully understand) in many ways makes me appreciate even more the incomprehensible. The science often is portrayed as mathematical mumbo-jumbo but really getting beyond that it, it describes (as best we poor humans can) the mathematical beauty and symmetry of the physical world, both tangible and intangible.

For the question at hand, the light beams moving at the speed of light. As already mentioned, both the special and general theories of relativity have stood the challenge of numerous tests and are fairly well accepted as an accurate mathematical description of an albeit weird physical "law". No human really knows why the cosmic speed limit exists only that it is there, and we've observed it and tested it.

Photons can't really change medium; they can be absorbed or reflected, but they do not spontaneously convert into something else, kind of like electrons they are fundamental. And unlike protons, which can decay into other objects.