I think a lot of people assume that this means you couldn't go more than a few (~100) light-years in your lifetime... But this is not actually correct. Counter-intuitively you can theorically go any number of light-years (essentially) in your lifetime, as long as you are able to approach the speed of light because when you do so the distance is dilated and hence you're covering far more ground within your reference f…
I assume people know how bad the penalty can be for going merely 10 MPH over the speed limit.
Don't worry about an individual photon except as part of an image in this example.
The light from the source hits the subject and is reflected toward your eyes at the speed of light.
That's why they call it the speed of light, and radio signals do it too between their source & receiver.
So now imagine you could travel faster than the speed of light to a planet a number of light-years away and you are going to get there from here.
Once you leave Earth orbit you will be able to accelerate up to and beyond c in the safest most gradual way directly toward your destination.
While still in orbit you look down on the traffic in your hometown, and everything is still moving at normal speed no matter how far it is down there, since you are a steady distance away from what it is you are looking at.
As you accelerate away from Earth and approach the speed of light itself you're beginning to catch up with the light that was reflected off your home planet quite a bit earlier than the light which is simultaneously being seen by those back in orbit.
So at half c you look out the window and it looks like everyone back in your hometown is moving at half speed. But naturally time marches on down there. You just can't be so sure any more. At that speed if you left 2 years earlier you will only be able to know additional things about your home which happened no more recently than 1 year ago at that point.
Of course you can't communicate with them about this in real time because of how long it takes the radio signal to get back & forth so you don't bother.
You keep going and reach full light speed which finally matches the rate the images are being reflected away from the Earth at, so now look back home and everyone appears to be standing still on Earth, as expected. Even though as far as you know they are still carrying on like normal.
OTOH, approaching the destination planet at the speed of light, that's pretty fast, but you have to realize their alien traffic is actually only moving half as quickly as it looks from your craft, whilst you are speeding so rapidly in their direction. Don't let that fool you, the aliens are only half as advanced as they look.
If you want to really see something, go faster than the speed of light and the planet you are approaching will be moving more than twice as fast as normal, and looking Earthward all you can see would be things moving backwards.
One thing that's happening is that you are always seeing images of these two planets where the light source originated from two different suns.
Once the distances get far enough, it's possible to launch a mission to a destination that actually no longer existed any more for quite some time before launch, only who knew?
In that case the earlier you make your reservations the more unwise it could be.