Speed of light and length contraction

In summary, Einstein's assumption of the speed of light being a constant is based on previously mentioned relativistic effects. These effects don't apply to objects at high speeds if they are enclosed (like in a spaceship or train). There are practical issues to consider, such as avoiding collisions.
  • #1
Brookey
1
0
Hey, I am new to this site, I'm not entirely sure where i should post this question but can anyone here help?
I need to know Einsteins assumption of the speed of light as a constant by referring to length contraction, mass and time dilation and how it affects people traveeling in space at high speeds...
Anyone?
Brooke
 
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  • #2
when traveling at very high speeds:

To = T(sqrt(1 - v^2/c^2)) [To is stationary time, and T is the travellers time]
Lo = L(sqrt(1 - v^2/c^2)) [Lo is stationary length, and T is the length experienced
by the traveller]
Mo = M/(sqrt(1 - v^2/c^2)) [Mo is rest mass, and M is the travellers mass at high speed]

to do these calculations it is simple is you use units in c, (ex. 0.8c, 0.9c) and not in m/c. If you use c (speed of light) units, then the units cance out nicely and your answer can be obtained in 30 seconds.
 
  • #3
The answer that I am about to give you is not my own but brian greenes from the fabric of the cosmos .
he states that when you are stationary you are traveling only through time but when you move you are traveling through both space and time.
now when you a stationary you are traveling through time at the spped of light but when you move some of this speed is transferred to traveling through space. this means that because the sum of traveling through space and time must always =c then the faster you travell through space the slower you must travel through time. hence time dilation.
hope this helps.
 
  • #4
Both Nenad and jamie's answers were correct, however your looking at the problem backwards. Einstein didn't assume the speed of light is constant because of the previously mentioned relativistic effects, he discovered these effects because he assumed the speed of light is constant. This assumption comes from James Clerk Maxwell's equations for electromagnetism, which don't provide a frame of reference for the calculated speed of light, c. The conclusion (which was drawn by many before Einstein too) was that therefore light must travel at c relative to everything, contradictory to Newton's laws of motion. Therefore Einstein developed his special theory of relativity to show how it's possible for light to travel at c relative to everything, the explanation being drawn from such things as time dilation and length contraction.
Welcome to PF!
 
  • #5
Brookey said:
Hey, I am new to this site, I'm not entirely sure where i should post this question but can anyone here help?
I need to know Einsteins assumption of the speed of light as a constant by referring to length contraction, mass and time dilation and how it affects people traveeling in space at high speeds...
Anyone?
Brooke

Moving at high speeds per se doesn't have any effect. The laws of physics are independent of one's velocity. So if one is in a closed spaceship, or a closed train, one can't tell from local observations whether or not one is even moving.

Of course, there are some practical issues, like the importance of avoiding collisions. Running into even a very small dust speck at relativistic velocities would be Bad. Without some more details, it's hard to say which of these practical issues would be important to you.
 

1. What is the speed of light?

The speed of light is a fundamental physical constant that represents the speed at which light travels in a vacuum. It is approximately 299,792,458 meters per second or 186,282 miles per second.

2. How was the speed of light first measured?

The speed of light was first measured by Danish astronomer Ole Rømer in the late 17th century using observations of the moons of Jupiter. He noticed that the time between eclipses of the moons varied depending on the distance of the Earth from Jupiter, providing evidence that light had a finite speed.

3. What is length contraction?

Length contraction is a phenomenon described by Einstein's theory of relativity, which states that objects appear shorter in the direction of their motion as they approach the speed of light. This is due to the fact that time slows down for objects in motion, causing distances to appear shorter.

4. How does length contraction affect our everyday lives?

Length contraction is not noticeable in our everyday lives as we do not typically move at speeds close to the speed of light. However, it is a crucial concept in modern physics and helps explain many phenomena in the universe, such as the time dilation observed in high-speed particles.

5. Is the speed of light constant?

Yes, according to Einstein's theory of relativity, the speed of light is constant and does not change regardless of the observer's frame of reference. This means that the speed of light is the same for all observers, regardless of their relative motion.

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