What would happen if an object reached the speed of light?

[CAllFlow]

Earlier today a friend and myself were having a discussion about a vehicle going the speed of light and what it would look like if someone was to witness this event happen. (The discussion started because we were watching Star Wars)

First off my understanding of an object reaching the speed of light is that it can reach "almost light speed" but never actually break the light speed barrier. Now let's say that an object like a car somehow manages to break the 299,792,458 m/s Universal speed limit. If you were watching the car as it hit light speed what would you see? My thoughts are that from behind the car light can't catch up to it to reflect back at you so it becomes invisible. From the side there may be an instant where light hits the car from a forward angle then reflects back to you, causing you to see the side of the car as if it was in front of you when really it's passed you. Finally from the front, with light being able to hit the car but never reflect back quick enough to be seen does the front of the car become a black hole?

My friend and I are quite curious as to what other, more intelligent people have to say on this subject.

 

[bcrowell]

First off my understanding of an object reaching the speed of light is that it can reach "almost light speed" but never actually break the light speed barrier.

That's correct.

Now let's say that an object like a car somehow manages to break the 299,792,458 m/s Universal speed limit. If you were watching the car as it hit light speed what would you see?

You can't, so science doesn't have an answer to your question.

FAQ: What does the world look like in a frame of reference moving at the speed of light?

This question has a long and honorable history. As a young student, Einstein tried to imagine what an electromagnetic wave would look like from the point of view of a motorcyclist riding alongside it. But we now know, thanks to Einstein himself, that it really doesn't make sense to talk about such observers.

The most straightforward argument is based on the positivist idea that concepts only mean something if you can define how to measure them operationally. If we accept this philosophical stance (which is by no means compatible with every concept we ever discuss in physics), then we need to be able to physically realize this frame in terms of an observer and measuring devices. But we can't. It would take an infinite amount of energy to accelerate Einstein and his motorcycle to the speed of light.

Since arguments from positivism can often kill off perfectly interesting and reasonable concepts, we might ask whether there are other reasons not to allow such frames. There are. One of the most basic geometrical ideas is intersection. In relativity, we expect that even if different observers disagree about many things, they agree about intersections of world-lines. Either the particles collided or they didn't. The arrow either hit the bull's-eye or it didn't. So although general relativity is far more permissive than Newtonian mechanics about changes of coordinates, there is a restriction that they should be smooth, one-to-one functions. If there was something like a Lorentz transformation for v=c, it wouldn't be one-to-one, so it wouldn't be mathematically compatible with the structure of relativity. (An easy way to see that it can't be one-to-one is that the length contraction would reduce a finite distance to a point.)

What if a system of interacting, massless particles was conscious, and could make observations? The argument given in the preceding paragraph proves that this isn't possible, but let's be more explicit. There are two possibilities. The velocity V of the system's center of mass either moves at c, or it doesn't. If V=c, then all the particles are moving along parallel lines, and therefore they aren't interacting, can't perform computations, and can't be conscious. (This is also consistent with the fact that the proper time s of a particle moving at c is constant, ds=0.) If V is less than c, then the observer's frame of reference isn't moving at c. Either way, we don't get an observer moving at c.

 

[VanOosten]

well as the car gets close to the speed of light the length contraction causes it to get shorter and shorter and theoretically speaking if it reaches the speed of light it would have no length at all and therefore invisible.

 

[Bob S]

Look up the Terrell Effect on the web. It includes distortion and rotation of objects moving by at speeds very close to the speed of light. Color also gets blue and red shifted as objects move by.

Here is a video simulation on youtube



Bob S

 

[Christov84]

Now let's say that an object like a car somehow manages to break the 299,792,458 m/s Universal speed limit. If you were watching the car as it hit light speed what would you see?

I don't think the car would disappear but you certainly wouldn't be able to tell where the car is by looking at it.

Think of it like the speed of sound, object passes and sound catches up.

In this case object passes and then light catches up.

Now this is where someone says causality is broken.

Assuming we find a way to break C of course.

 

[Bob S]

Now let's say that an object like a car somehow manages to break the 299,792,458 m/s Universal speed limit. If you were watching the car as it hit light speed what would you see? My thoughts are that from behind the car light can't catch up to it to reflect back at you so it becomes invisible...

There is an observed effect that is very similar. Cosmic rays and charged particles from particle accelerators travel at speeds very close to the speed of light, c. But the speed of light in media like water (n=1.33) or glass (n=1.52) is only v = c/n. When these particles pass through glass or water, the particle velocity is greater than c/n, so they produce a "shock wave" of light particles, called Cerenkov radiation, named after a Russian physicist who first observed it. For a cosmic ray, there are about 230 visible light photons created per cm of travel in water. Beta particles from radioactive beta decay also travel at speeds greater than c/n. The bluish glow of Cerenkov radiation from beta decay is easily observed by looking down into a pool-type nuclear reactor, or looking at radioactive fuel rods stored in water.

So Cerenkov radiation is the result of fast charged particles breaking the speed-of-light limit in media like water or glass, where the speed of light is v=c/n.

Bob S

 

[John232]

Well, if the ship was traveling 1m/sec slower than light speed he would still observe the light to be traveling about 300,000 km/sec faster than he was, so if he went 1m/sec faster to obtain light speed I don't think there would be much of a difference.

No one has been able to accelerate a particle to the speed of light let alone a ship, but I think it may have to do with the speed the EM force propagates. It would only affect a particle at the speed of light so then how could it ever make anything go faster than that? It would be like trying to push something with a car that tops out at 180mph to get it to go 200 mph, it just isn't going to happen.

 

[John232]

And the object the car is trying to push is more massive...

 

[Christov84]

stirring the pot:

http://www.universetoday.com/33752/device-makes-radio-waves-travel-faster-than-light/

 

[JesseM]

stirring the pot:

http://www.universetoday.com/33752/device-makes-radio-waves-travel-faster-than-light/

The article says "Einstein predicted that particles and information can’t travel faster than the speed of light, but phenomena like radio waves are a different story, said John Singleton", so presumably Singleton is not claiming information can be transmitted faster than light this experiment. I would imagine it's an issue of the phase velocity or group velocity of the wave being faster than light, which is consistent with relativity--see here and here.