# The Naked Scientists Forum

### Author Topic: How do imaginary numbers feature in relativity and the speed of light?  (Read 673 times)

#### dutchiexx

• Jr. Member
• Posts: 19
##### How do imaginary numbers feature in relativity and the speed of light?
« on: 14/02/2016 09:02:48 »
i dont know much about science, but i remember reading something about atoms vibrating, i read that if atoms vibrate slower then the speed of light then they become physical and if they vibrate faster then light then they become un-physical
is this true?i thought nothing can move faster then light.
then i really thought about it and ran into a problem i cant figure out, and google doesnt have the answers either

its hard for me to explain but here goes,

okay,so imagine the earth and our sun, we know that light does infact take time to travel from the sun to earth.(not sure exactly how long, buts thats not important right now) so now imagine that your traveling at the speed of light towards the sun,lets just say it takes you 3 hours to travel to the sun from earth (3 hours is not correct but lets just roll with it for now)

now, imagine that you are so big that the earth and sun are the size of marbles compared to you.now, if you put your hand right above the sun and swing your arm fast towards the earth,you would hit the earth in like 1 sec, but by doing this, your hand would be moving faster then the speed of light from the perspective of a normal sized human, but it would seem like your moving faster then light from your perspective.how the fk does this work?

ah never mind i found my answer :)

turns out eistien already explained this subject :)
« Last Edit: 15/02/2016 23:04:04 by chris »

#### evan_au

• Neilep Level Member
• Posts: 4120
• Thanked: 245 times
##### Re: space and time?
« Reply #1 on: 14/02/2016 12:03:23 »
Quote from: dutchiexx
if they vibrate faster then light then they become un-physical
is this true?i thought nothing can move faster then light.
This is related to the mathematical concept of "imaginary numbers".

There are a number of equations in relativity that have a square root in them (√, used in the Lorentz factor). If an object is travelling slower than light, then you take the square root of a positive number, which is also positive. We have experience in interpreting these "real" numbers in terms of the physical world around us.

However, if you exceed the speed of light, the number inside the square root becomes negative, and there are no "real" solutions. In mathematical terminology, the solutions are "imaginary". We don't know how one would interpret such imaginary solutions in terms of the physical world we see around us (but some physicists have tried testing for such "tachyon" particles, so far without success). This is why they might be described as "unphysical".

Einstein said that you can't accelerate any massive object from below the speed of light to even reach the speed of light, let alone go beyond it.
The equations of relativity don't explicitly say that there can't be anything faster than the speed of light, it's just that we don't know how we could do it, we've never seen it, and we don't really know what it would look like.

#### The Naked Scientists Forum

##### Re: space and time?
« Reply #1 on: 14/02/2016 12:03:23 »