According to our current understanding of physics, it is not possible for an object with mass to travel at the speed of light. The theory of special relativity, formulated by Albert Einstein, tells us that as an object with mass approaches the speed of light, its mass would effectively become infinite, requiring an infinite amount of energy to accelerate further.
However, we can still discuss the effects of acceleration on a spaceship that is traveling at speeds close to the speed of light, but not precisely at it.
As the spaceship accelerates, it experiences a number of relativistic effects. These effects become more significant as the spaceship's speed approaches the speed of light:
Time dilation: According to the theory of special relativity, time passes slower for objects moving relative to an observer at rest. As the spaceship accelerates and reaches high speeds, time dilation would occur. From the perspective of someone on the spaceship, time would pass more slowly compared to an observer at rest.
Length contraction: Another consequence of special relativity is length contraction. As an object moves faster, its length in the direction of motion appears contracted from the perspective of a stationary observer. So, as the spaceship accelerates, it would appear shorter in the direction of motion.
Increased energy requirements: As the spaceship approaches the speed of light, its relativistic mass increases. This means that it would require more and more energy to continue accelerating. The closer it gets to the speed of light, the more energy it would need, and reaching the speed of light itself would require an infinite amount of energy.
Momentum and force: As the spaceship accelerates, its momentum increases. However, in accordance with special relativity, the relationship between momentum, velocity, and mass is different from classical physics. The increase in momentum requires an increasingly large force to sustain the acceleration.
Causality and information: One of the fundamental principles of relativity is that no information or influence can travel faster than the speed of light. If the spaceship were to accelerate to speeds close to the speed of light, there would be limitations on how quickly information from the spaceship could reach distant observers or how quickly the spaceship could respond to external events.
It's important to note that these effects are theoretical predictions based on the principles of special relativity. Since we currently lack practical means to accelerate massive objects to speeds close to the speed of light, the direct experimental verification of these effects is challenging. However, they have been confirmed through numerous indirect experiments and observations involving high-energy particles.