You are standing still and a train goes by. You notice it's speed. Now you're in a train car with no windows, and a glass smooth track so you don't feel the clacking jars as the wheels pass over the rail joints. You toss a ball between you and a friend, and the ball to your present perception is just moving at the speed it's thrown.
A jet is moving through the air at Mach 3. it's gotten quieter in the cockpit, because the jet is moving faster than the noise it is producing. The pilot keys his mic and talks to the tower. His voice is being spoken in a bubble of air (interior of the cockpit) that is moving at Mach 3 so the sounds he makes seem normal in that enclosed environment.
A space ship is flying near/at the speed of light. Light as we know it is perceived far differently depending upon which direction an observer is viewing. Blue shift red shift. An observer inside the spaceship however turns on a light and views his surroundings with no problem. I understand the Doppler affect of a train whistle as it goes by, but wonder what exactly happens if a search light were aimed forward of the speeding space ship. Would the photons/light energy be amassed near the front of the space ship? Sort of a "Photon torpedo," or would it become a different form of energy that travels faster than the speed of light. Because everything gains in mass the nearer it approaches the speed limit of light, why don't photons have annihilating properties? They are traveling at light speed, so they should ave infinite mass. Their mass is used for solar sails and move space craft with light pressure
I'm curious and want to know. I hate junk science in sci-fi and want to write a good one.
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Now I'll be up all night thinking about this.
My understanding is that the speed of the vehicle housing the light source would be traveling at the speed of light; therefore, wouldn't the light projecting from the vehicle still be traveling at the speed of light... Are you asking then with the ball in the train theory that the light from the headlight would be traveling at twice the speed of light?
Am I understanding your question? I'm certain we need hale's input here! I have this blond headache going now. ;> (luv you huck)
I think the light from the vehicle would approach Warp Factor 2 and start time traveling - or astral projecting.
You are on the right track with a lot of your thinking there, Huck, with a couple of small but important modifications.
First thing to remember is that the speed of light is the same for everyone no matter what is happening, period. Whenever you measure the speed of light, you will measure the same speed (about 3*10^8m/s in a vacuum) no matter if you are moving or the source of the light is moving or if you both are moving. Doesn't matter if the motion is toward each other, away from each other, or any angle in between.
This seems very counterintuitive. However, different observers will disagree on measuring times and distances due to the relativistic phenomena of time dilation and length dilation respectively. Since each observer has different measurements for time and distance, when you calculate the speed of light (v=d/t) the d and the t change just the right amount that everyone measures the same speed of light.
So if a spaceship is traveling toward Earth very fast and let's say he wants to use a laser to communicate with Earth (laser communication is very efficient as larger amounts of data can be transmitted at a faster rate than by radio signals). The spaceship fires, oh, let's say a green laser toward the Earth. That laser will be blue shifted. Depending on how fast the ship is moving, it may be shifted to the blue, violet, ultraviolet or even to X-rays and gamma rays (if we ever design a spacecraft that can travel near light speed, we will need to worry about shielding as every single photon of light that it encounters will be blue shifted to a dangerous X-ray or gamma ray so you better have good shielding!) The laser would still travel at the speed of light (from both the perspective of the spaceship and the Earth)but would have more energy for an observer on Earth.
And you are correct that objects have an increase in mass as they approach the speed of light and the formula says at the speed of light, the mass would be infinite (we observe this increase in mass in particle accelerators such as Fermilab and CERN and it matches predictions). Well, photons have zero mass to start out with so infinity times zero is still zero. A lot of people don't like photons having zero mass, but they are pure energy. Photons cannot have mass as that would violate a symmetry in quantum mechanics (I believe it is the SU1 symmetry if I remember my quantum mechanics correctly, but that is getting pretty technical there!) Photons have energy and momentum so they can be used for solar sails as you state.
Although there are some similarities with the Doppler shift of sound and the Doppler shift of light, there are some subtle differences as well so it is important not to treat them as though they are identical.
There is a fun science fiction book called Redshift Rendezvous that plays with relativity. It takes place on a spacecraft where the speed of light is ten meters per second. Relativity suddenly becomes very important in the everyday lives of people on board!
Hope this didn't muddy the waters too much more!
I'm going to take a shower when I get home... I'm muddied all right! :D
Next time can we talk about string theory?
Thanks HB, that answered a lot of questions. The last little bit deals with the red shift story and light speed inside a spaceship at near light speeds. Are you saying that a light source inside the space ship would have the same constraints as the speed of light outside the ship? Now that is an interesting quagmire and leads to a lot of fun possibilities.
People won't be able to travel in space ships traveling at such speeds. As their mass increases, their blood would become too heavy for the heart to pump. Maybe time dilation would preclude this though and time would stand still for the periods at light speed.... Oh jeez. If that were to happen, any automatics that would pull the ship down slower at the end of the trip, wouldn't function as they went into a state of stasis.
These problems turn all my favorite sci-fi into science fantasy, and I like my fiction to be plausible. I like early Heinlien because he wove science facts with fiction. That's the level I wish to write at. Weaving science fact with fiction. I'll probably have more questions for you.
Thanks a ton! I'll be asking about slingshot orbits to gain/bleed speed sometime in the future.
All this is making my head hurt...
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