Light goes at the fantastic speed of 670 million miles per hour, which is to the moon and back in less than a second, so can we achieve this speed? What if a rocket going at half the speed of light shot a bullet forward at half the speed of light? Unfortunately, doing this changes time and space, so the bullet only goes at four-fifths the speed of light.
Can we gradually speed up a rocket up to the speed of light? Nature again intervenes by increasing the rocket mass until at near the speed of light its near infinite mass needs a near infinite force to move it, so this doesn’t work either. In theory, in a rocket going 5mph slower than the speed of light, one could throw a ball at 5mph per hour to reach the speed of light but in practice, we can’t produce the force needed to throw the ball. And if the rocket had headlights, one might expect light to leave it at almost twice the speed of light, but again nature plays with space and time to keep the speed of light the same.
This seems to deny the conservation of mass, and the thermodynamic law that energy in a closed system can’t be lost, but Einstein noted that energy and mass convert by E=mc2, so nothing is really lost. But whether mass is energy, or energy is mass, or both are aspects of something else, isn’t clear.
Relativity contradicts all our intuitions about movement. For example, if two rockets left the earth at half the speed of light, one to the sun and one to Pluto (Figure 5.6), relativity requires light from the sun to pass both rockets at the same speed! But how can the same photon pass rockets going to the sun and away from it at the same speed? This makes no sense in classical terms.
The equations work but, like those of quantum theory, deny common sense. How can space, which is the measure of movement, itself move? How can time, which is the measure of change, itself change? Einstein deduced that space and time had to change for our world to be as it is, but not why. Perhaps he expected physics to explain it later, but a century on, we are no wiser.
In this model, light sets the speed limit of our universe because the network of space passes it on every cycle, so nothing can go faster, but the same model also portrays matter as a stationary standing wave, which raises the question, how does matter move at all?