But is it art?

**R-Soul** · 17th August 2010, 12:03

Originally Posted by aprilia_RS250

Remember Newton's physics are incorrect when you take into consideration that something is traveling at speed of light, that's where Einstein came in.

I think you're confusing mass with momentum here... Acceleration causes your momentum to increase, not mass. You need an infinite amount of energy to move something at speed of light, mass doesn't change at all.

No, he is right. I also remember this from varsity days. As your velocity increases to tend towards the speed of light, your mass tends towards infinity.

Simplified,
F=m.a

To accelerate an infinite mass would take an infinite amount of force (and hence energy in creating that force), and hence you can never actually reach the speed of light.

Also, he is right in that energy is conserved, not mass. Matter is created and destroyed all the time in stars in nuclear reactions. A tiny amount onf matter contains a huge amount of energy locked up in it. When matter is destroyed, it releases this energy as fusion or fission nuclear reactions.

**swbarnett** · 17th August 2010, 17:16

Originally Posted by aprilia_RS250

So if I was traveling at speed of light my rest mass would remain at 80kgs however my relative mass (i.e. momentum) would be infinity kgs/m/s?

Yes, your rest mass is essentially just a measure of the mass you have when you're not moving in a given inertial reference frame i.e. when you're at rest. Also correct, as per the graph I posted earlier, as you get ever closer to the speed of light your mass increases more and more for every extra kph you add.

The weird thing here is that all this is relative. If you are travelling near the speed of light at a constant velocity all the laws of physics appear to work the same. For example, you can play tennis in a smooth fast moving train with no windows and you'll think the train is standing still.

If you are travelling near the speed of light at a constant velocity you won't feel any heavier. Indeed, if you stand on a set of scales it will just read your rest mass. However, to a stationary observer (relative to you) your mass will have increased, well, massively.

After consultation with the expert I've realised that what I said earlier is not quite right. Adding gravity to an inertial reference frame ruins its' inertial nature because gravity itself is akin to an accelleration.

Another interesting thing is that the speed of light itself is constant inside the reference frame no matter how fast you are travelling. Hold a mirror in front of you and the time taken for the photons to leave your face, hit the mirror and reach your eyes remains the same. This is related to the fact that as you travel faster time actually slows down. This has been proven experimentally by synchronising two atomic clocks and sending one around the world in a jet. Even at the relatively low speeds of commercial air travel the clock that went around the world lost time relative to the one that stayed on the ground. In essence we travel backwards through time relative to the ground dwellers every time we hop on an airliner.