Search In
• More options...
Find results that contain...
Find results in...

# Traveling faster than light

## Recommended Posts

Correct me where I'm wrong, but my understanding is that the closer an object approaches the speed of light the slower time goes by for that object (known as time dilation). If speed is a measurement of distance over time, then wouldn't an object traveling very nearly the speed of light effectively to those stationary be traveling much faster than the speed of light due to the relative effects of traveling near the speed of light, thus making interstellar travel feasible?

Does anyone know how this works? If light travels 299,792.5 kms per second, how much does time slow down for me if I manage to travel 200,000kms per second? What about 250,000kms per second? 280,000kms per second? 295,000km per second? 299,780kms per second? There must be a simple hyperbola equation that lets you plot the time dilation for different speeds approaching c.

One last point: Does light, being the only thing that is able to travel at the speed of light, not experience any passage of time? Is it therefore ageless and timeless and therefore actually traveling infinite distances instantaneously?

i thought that time was relative, though. wouldn't it be the same?

1 hour ago, Hellbent said:

If speed is a measurement of distance over time, then wouldn't an object traveling very nearly the speed of light effectively to those stationary be traveling much faster than the speed of light due to the relative effects of traveling near the speed of light, thus making interstellar travel feasible?

To those stationary, the moving object would appear slowed down and contracted in length, but it would not appear to travel faster than the speed of light, precisely due to the relative effects in question (different perceptions of time and distance depending on speed relative to the observed object).

1 hour ago, Hellbent said:

There must be a simple hyperbola equation that lets you plot the time dilation for different speeds approaching c.

You've got the equation right here - from briefly reading the article, it seems that, if you and another object are moving at different speeds, and the speed by which you're moving relatively to each other when measured from the point of view of the other object is equal to v, then from your own point of view, the other object seems slowed down exactly delta t' times relatively to you (if delta t = 1). Note that there is a distinction between the speed by which you're moving relatively to each other when measured from your point of view and when measured from the other object's point of view, so that before applying the equation to compute a perceived slowdown of a moving object from your point of view while the object is moving at speed v also from your point of view, the speed would have to be recalculated into speed by which you're moving from the other object's point of view, using the equation for time from this article and the equation for length from the article about length contraction.

1 hour ago, Hellbent said:

One last point: Does light, being the only thing that is able to travel at the speed of light, not experience any passage of time? Is it therefore ageless and timeless and therefore actually traveling infinite distances instantaneously?

I'm not sure if the words "ageless" and "timeless" (especially "timeless") are fitting to describe this concept, but light indeed does not experience any passage of time (and passage of distance), so that from a photon's point of view, its creation is immediately followed by (traveling zero distance at zero time, and then) its destruction, no matter how long distance it has traveled from other points of view.

Edited by scifista42

1 hour ago, Hellbent said:

Does light, being the only thing that is able to travel at the speed of light, not experience any passage of time?

From a photon's point of view, he has never traveled. He left his origin and hit his destination at the exact same 'time'.

No, it's all really weird and non-intuitive. Say you've got two objects, A and B, that are moving away from point O in opposite directions. Suppose both A and B are moving at 2/3 the speed of light relatively to O. You'd think that A and B would be moving a 4/3 speed the light relatively to each other, wouldn't you? But no, they don't.

Also as a minor point of pedantry: light doesn't necessarily travel at the speed of light. More properly we should speak of the speed of light in a vacuum. It's certainly possible to slow down photons, and experimentally they have even been stopped (though not for very long). (src)

Since photons are only at maximum speed in a vacuum, and they're slower in a denser medium, they do experience the passage of time a bit. They're still quite fast (usually).

Ahhhh, we certainly can travel faster than the speed of light.

We wouldn't do it by achieving a velocity that fast. That's not sensible. What we'd do is, we skip out of this universe briefly, then skip back in, re-entering this universe at the desired location.

It's a little bit like skipping a rock on top of water. The water isn't able to let your rock just rocket fast through it, but when you skip the rock on top, it flies through the air and re-enters the water at a different spot. The difference tho is that the physical location in the other universe isn't related to the location in this one. So you just skip out and just re-enter in this universe whereever you wanted.

:D

5 hours ago, Hellbent said:

Does light, being the only thing that is able to travel at the speed of light, not experience any passage of time?

Gravity waves are said to travel at c, and there are probably other phenomena that do as well. c is not necessarily the "speed of only light" but perhaps a universal speed limit on any sort of information moving through space.

Here's another way at looking at it. Everything always travels at exactly the speed of light through the 4 dimensions of space-time. The faster you travel through space, the slower you travel through time, but the total speed is the speed of light. Anything with mass can never reach the speed of light through space, and therefore non-zero speed through time,  and anything without mass can ONLY travel at the speed of light through space, and therefore zero speed through time.

All this is, of course, in a vacuum.

15 hours ago, Vorpal said:

c is not necessarily the "speed of only light" but perhaps a universal speed limit on any sort of information moving through space.

With the exception of quantum entanglement, which transports information instantaneously across any distance!

2 hours ago, dew said:

With the exception of quantum entanglement, which transports information instantaneously across any distance!

Because of the way entanglement works, it cannot be used to send information faster than light. I, too, was disappointed when I learned that.