Bob Maths
EVE University
Ivy League
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Posted - 2014.05.11 11:31:00 -
[1] - Quote
James Amril-Kesh wrote:1 AU is about 8.32 light minutes (.32 minutes ~= 19 seconds).
As said earlier, light doesn't travel slower in a medium, what happens is that it's absorbed (photon energy excites a valence electron in the material) and re-emitted some time later (excited electron releases its energy in the form of a photon to return to the base energy state).
And again, light doesn't actually bend. Light always travels in a straight path. The space that the light is traveling through is curved.
Not necessarily correct and we're arguing pedantics here.
Light doesn't excite exclusively valence electrons, as valence electrons are ones of the highest energy state, requiring the least energy to be emitted and are absorbed if the photon is of the hf to release the electron. The photoelectric effect tells us that the energy of the photon only needs to be greater than the difference of next energy state to the highest energy state for emission to occur.
As most mediums compared to the path of trajectory of a photon is virtually non-existent if it is opaque. The speed of light c is derived from Maxwell's equations (as all physicists should know) and is ultimately the inverse square root of the product of the permeability and permittivity of free space. However, that is free space. All mediums other than free space (a vacuum) have a refractive index which is a proportional increase of what the speed of light in the medium needs be multiplied by to become c. So as a result the permeability and permittivity of any other medium will reduce the speed to v, a percentage of c.
Light doesn't bend but space does so it doesn't bend? So, a projectile doesn't bend towards the Earth, the Earth is being pulled upwards in such a fashion that the projectile appears to be bending towards it. Oh wait, anyone who does physics knows that all masses attract each other so actually that's right, if only by thousandths of the radius of a nucleon in the case of Earth-to-Projectile. Classical mechanics will tell us that the projectile follows a parabolic motion towards the surface much quicker than the Earth will rotate and adjust itself to the point of the projectile. Light does bend as the path is bent and it can only travel along spacetime which begs the nature of light.
Ion Kirst wrote:
Yes, so if you could travel at the speed off light, it would take you 4.37 years to reach Alpha Centauri. (or you could get lost in space.)
-Kirst
No it would not. Relativity will tell us that it will take less 'time' for you to reach Alpha Centauri but why waste all the energy going up to the speed of light when you could just warp and get there sooner?
When considering time dilation you have to also take into account length stretching (or from your point of view, length contraction) of the object in question that is travelling to the speed of light. The reason (i imagine, not versed as much as a msci in this) is because as you travel to the speed of light you occupy all the space of the event within the time period of observation and thus you appear to be stretched.
Length contraction means that your journey will mechanically take less time from your clock than if you were to sit and observe the journey. There would be a disparity in clock time ticking.
This is one of the reasons why we can observe muons at ground level and also how matter from the start of the universe are only just arriving here.
To answer the main post if it hasn't been answered already:
9.4605284 +ù 10^15 m in standard form which is 9.4 trillion (or billion if you like the long scale) km, so think travelling for 6 hours at 3 AUs |