Accelerating to speed of light

In summary: The geometry of space time.Suppose you have a spaceship which undergoes constant acceleration as measured by an on-board accelerometer, and that after 6 months' travel (as measured by an on-board clock) you have reached half the speed of light (0.5c) relative to your starting point. You might think that after another 6 months you would reach the speed of light. But you don't, because the rule for "adding" velocities is notu + vbut\frac{u+v}{1+\frac{uv}{c^2}}.So , in fact your velocity would be\frac{0.5+0.5}{1+0.5^2}\,c =
  • #1
kannank
25
0
When the an object is accelerated and when the velocity approaches the speed of light, its mass increases exponentially the force required to accelerate the object increases exponentially. So it cannot be done. Fine.

But what if I travel in a spaceship with A LOT of fuel and the spaceship is accelerated constantly by burning the fuel? When the velocity of spaceship approaches the speed of light, does increase mass in its own frame-of-reference?

This may be a silly question. I got confused somehow.

cheers!
KANNAN
 
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  • #2
kannank said:
When the velocity of spaceship approaches the speed of light, does increase mass in its own frame-of-reference?
No, rest mass is an invariant quantity, and an objects mass in its own frame is the invariant mass.
 
  • #3
DaleSpam said:
No, rest mass is an invariant quantity, and an objects mass in its own frame is the invariant mass.

Then what stops me from accelerating my spaceship to FTL? I still got fuel left in my spaceship.
 
  • #4
The mass that is moving is not aware that its mass increases. So the answer to your question is no, no matter how much fuel you burn you still cannot reach the speed of light.
We can choose a reference point (e.g. some distant quasar) for the Earth which makes our velocity a significant fraction of the speed of light. Do you feel any heavier now? No matter how fast you are moving with respect to some outside reference point your flash light will still work the same.
 
  • #5
kannank said:
Then what stops me from accelerating my spaceship to FTL? I still got fuel left in my spaceship.

The geometry of space time.
 
  • #6
Suppose you have a spaceship which undergoes constant acceleration as measured by an on-board accelerometer, and that after 6 months' travel (as measured by an on-board clock) you have reached half the speed of light (0.5c) relative to your starting point. You might think that after another 6 months you would reach the speed of light. But you don't, because the rule for "adding" velocities is not[tex]u + v[/tex]but[tex]\frac{u+v}{1+\frac{uv}{c^2}}.[/tex]So , in fact your velocity would be[tex]\frac{0.5+0.5}{1+0.5^2}\,c = 0.8\,c.[/tex]The formula always gives you an answer less than c, no matter how long you wait.

Another way of looking at this is that everyone measures the speed of light to be the same value relative to themselves (299792458 m/s). So at the start of your journey you reckon you are going 299792458 m/s slower than your target speed, but after 6 months you reckon are still going 299792458 m/s slower than your target speed: you've got no nearer to it.
 

FAQ: Accelerating to speed of light

1. What is the speed of light and can anything actually reach it?

The speed of light is approximately 299,792,458 meters per second in a vacuum. According to Einstein's theory of relativity, nothing with mass can reach the speed of light as it would require infinite energy. However, particles with no mass, such as photons, can travel at the speed of light.

2. How close have we come to reaching the speed of light?

The fastest man-made object, the Parker Solar Probe, has reached speeds of about 430,000 miles per hour, which is about 0.064% of the speed of light. Although we have not come close to reaching the speed of light, we have been able to accelerate particles to very high speeds, just below the speed of light, in particle accelerators.

3. Is it possible to travel faster than the speed of light?

According to our current understanding of physics, it is not possible to travel faster than the speed of light. As an object approaches the speed of light, it would require infinite energy to accelerate it further. Additionally, time would slow down for the object, making it impossible to travel faster than the speed of light.

4. What are the potential implications of traveling at the speed of light?

If it were possible to travel at the speed of light, it would drastically change our understanding of space and time. The laws of physics, as we know them, would break down and many theories, such as causality, would need to be reexamined. It would also open up the possibility of interstellar travel and exploration.

5. How does the speed of light impact our daily lives?

The speed of light plays a crucial role in many technological advancements that we use in our daily lives. For example, fiber optic cables use light to transmit information at incredible speeds. The speed of light also dictates how fast information can travel, which is important for communication and technology. Additionally, the speed of light is used in scientific experiments and research to study the properties of matter and the universe.

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