Will we go the the past if we could go faster than speed of light?

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SUMMARY

The discussion centers on the implications of traveling faster than the speed of light (c) and its relationship to time travel. Participants assert that exceeding light speed is impossible according to Einstein's theory of relativity, specifically referencing the equation t' = t√(1 - v²/c²). The conversation highlights that if one were to hypothetically exceed light speed, the time dilation factor would become imaginary, indicating a fundamental breakdown of our understanding of time and space. Ultimately, while one may observe past events, actual time travel remains a theoretical impossibility.

PREREQUISITES
  • Understanding of Einstein's theory of relativity
  • Familiarity with the concept of time dilation
  • Basic knowledge of spacetime geometry
  • Awareness of the properties of light and massless particles
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  • Study Einstein's theory of relativity in detail
  • Explore the concept of time dilation and its mathematical implications
  • Research spacetime diagrams and light cones
  • Investigate theoretical physics concepts related to faster-than-light travel
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Physics enthusiasts, students of relativity, and anyone interested in the theoretical implications of speed and time travel.

altairz
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On a forum I read that we don't know what would happen if we went faster than speed of light. On a video, I heard that we would go to the past if we went faster than c.

Im confused, what is right?
 
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altairz said:
On a forum I read that we don't know what would happen if we went faster than speed of light. On a video, I heard that we would go to the past if we went faster than c.

Im confused, what is right?

Hi altairz! :wink:

It's all rubbish!

We can't go faster than light, and according to the equation t' = t√(1 - v2/c2), if we could, our age wouldn't be multiplied by a negative factor, it would be multiplied by an imaginary factor! :smile:
 
tiny-tim said:
Hi altairz! :wink:

It's all rubbish!

We can't go faster than light, and according to the equation t' = t√(1 - v2/c2), if we could, our age wouldn't be multiplied by a negative factor, it would be multiplied by an imaginary factor! :smile:

thanks for answer :).. But what do you really mean with imaginary factor :p? ( sorry, I'm new to physics :P )
 
I mean that the time-dilation factor √(1 - v2/c2) becomes the square-root of a negative number, and is therefore imaginary. :smile:
 
"Time" is described as going from a state of less entropy to more entropy. Or from hot to cold in energy-temperature terms.I am not really sure what velocity (light speed) has to do with that.
 
For something with mass to travel at c, it would have to have infinite density. That is why the photon is massless.
 
Draw a diagram of time vs distance. Normally this is done with axes of years (vertical, time, both pos and neg.) and lightyears (horizontal, distance).
At a speed of c the graph is at 45deg. One lightyear traveled in one year. when extended in both horizontal directions this is called a light cone. It indicates the area inside which physical processes from the source can be experienced. Outside the cone is forbidden by Special relativity.
At 2c the graph is at 26deg, but still positive time.

To get to horizontal you need infinite speed. You can never go negative.
 
Travel in time is a function of a spacetime geometries that allow for such travel, not velocity. For speed to be a factor, you would need to be one of a two cosmic string whipping past each other, and even then the result wouldn't be as desired.
 
I can imagine that you move faster than speed of light, like you are at point A and after 1 sec point B (2*c distance) .. etc. which is a purely imagination. Then you will see the Earth event moving backward, on which I am sure.
 
  • #10
IF and this is a rather big IF, you cold travel faster than light, people say you will go back in time because-
Lets take a scenario. The year is 2010, yes? Let's say there is an outpost 42 light years away from Earth. If i get on a ship that can travel 42c, I will reach that outpost in 2011, yes? But, if (here we go again) I take a huge telescope and take a peek at the moon, I will see the light that reflected off the Apollo Mission in 1969... so have I traveled back in time?

No, because the year is still 2011. However, I can see past events, as I have overtaken the 'messenger' who 'delivered' the 'message'
 

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