You're completely right that we observe it taking an amount of energy approaching infinity to accelerate a particle as it approaches the speed of light. But wha

You're completely right that we observe it taking an amount of energy approaching infinity to accelerate a particle as it approaches the speed of light. But what the particle experiences is quite different. Imagine the speed of light is 10 units and you had a thruster on you that, in a vacuum, could generated exactly enough thrust accelerate you 1/10th that speed each time you pressed a button. Nothing suddenly happens causing the thruster to completely fail on the 10th, 11th, or 500th push of that button. All that would happen is that you'd start to experience things getting quite weird. The two biggest things would be that time for everybody would seem to be speeding up and distances would physically contract. This would prevent you from ever perceiving yourself as moving faster than 10 units. The distance from A to B might be 1000 units at rest, but through length contraction it might be perceived to instead only be 15, traversing that distance in thus 1.5 units of time would not be perceived as exceeding the speed of light. However, an outside observer would see you passing through those 1000 units at some speed asymptotically approaching 10 units of speed, but never getting there. They see you taking approximately 100 units of time, you see yourself doing it in 1.5 units of time. Both are right. A really cool (and handy) area where these two worlds of observer and observed intersect is in particle decay. For instance in particle accelerators we can observe particles that decay after 1 units of time, yet the odd thing is we get observe these particles existing for 4 or 5 units of time! Actually the same effect also applies to things in nature. Muons are created as a product of atmospheric particle collisions, and these muons do make their way down to Earth's surface, yet their lifetime (before decay) is less than the time it would take to get from our atmosphere to the surface of earth at the speed of light! Our universe is seriously weird. ---- These are all very practical problems, or solutions, depending on how you look at things. You can travel billions of years in a human lifetime. Here [1] is a handy converter. It'd take about 45 years at 1g accelerator for a person to travel 15 billion light years - to the ends of the currently observable universe. So the only question is how long it will take us to develop or discover such technology. This is one of the many reasons the possibility of an EM drive, though improbable, was so tantalizing! Forget infinite energy, we're going exploring! These are also the reason I said that things like extinction become quite difficult to define. For instance, imagine in 200 years that we send out 1000 exploration+colonization ships each with some 5,000 people on them (or whatever the magic number to create a genesis population without inbreeding is). And then 1000 years later humanity on Earth kills itself off. Are humans extinct? Well, we still have those 5 million humans traveling not only in different places in space but in different times in space. So you'd probably say no, but once again... it's weird. [1] - http://convertalot.com/relativistic_star_ship_calculator.html http://convertalot.com/relativistic_star_ship_calculator.htm...