# Is Light our limit? [closed]

Suppose something existed faster than light will we be able to perceive it? And even if we encounter it wouldn't seem to travel with speed of light?

• How is this question not telated to Physics? Nov 20, 2020 at 10:22
• their action seems to be dubious! Nov 20, 2020 at 11:13

Superluminal objects have a big problem with the relativistic mass equation: $$m = {m_0 \over {\sqrt{1-{v^2\over{c^2}}}}}$$ If you set $$v=2c$$ in the equation, you get $$m = {m_0\over{\sqrt{-3}}} \approx 0.577im_0$$ So you get an imaginary mass.

Goodness knows what that might mean... I'll have imaginary two kilos of potatoes please.

• ... and I need them quick! Nov 19, 2020 at 18:11
• @mickep ...Like imaginary five minutes ago.. I mean, from now.. or... something... Nov 20, 2020 at 6:29

There exist hypothetical particles named Tachyons that would travel faster than light. They are merely hypothetical since Einstein's relativity does not forbid their existence but there is no experimental support for their existence at all.

If such particles existed they would to us also appear to travel faster than light. We would first observe them when they are inside our detector and only later would we see the light that reflected of the particle as it aproached our detector.

The following image shows the spacetime diagram of a tachyon and how it would be observed, I copied this image from this webpage

Notice that the order in which the particles are observed by the observer do not follow chronological order. Event 0, which happened long before event 6 is only observed after event 6.

Note: This image claims for the light of the particle to be blueshifted as it aproaches the observer and redshifted as it moves away. I personally am not so sure whether that is truly what happens since the equation for relativistic redshift is $$\lambda_{recieved} = \lambda_{emitted} \sqrt{\frac{1+\beta}{1-\beta}}$$ which for $$\beta > 1$$ gives imaginary $$\lambda_{recieved}$$ which I would not know how to interpret.

• So we can say there will distortion in information provided by Tachyons suppose someone falls downs and breaks his hand we will find at least for a instant that his hand is broken before he falls down. Nov 19, 2020 at 10:58
• Re, "...and only later would we see the light that reflected of the particle as it aproached..." Just to be clear: What you are saying is, we would see the particle appear, out of nowhere, and it would instantaneously seem to split in to two parts, that would head off in opposite directions. The one part, represented by the blue dots in your diagram, actually is the particle approaching us, but from our point of view, we would see that approach "backward in time." Nov 19, 2020 at 14:26
• Indeed, that is exactly what we would 'see', although we would 'observe' just a particle going faster than light. The distinction between observing and seeing is crucial here. When observing we internally compensate for the fact that we know how long the light took to get to us, when seeing we do not. Nov 19, 2020 at 14:50