E=mc^2, but nothing can travel faster than light?

In summary, The conversation is about the famous mass-energy equation, E = mc^2, and how it relates to the speed of light. The participants discuss a potential contradiction between the equation and the fact that nothing can travel faster than the speed of light. They also clarify that c^2 is not a speed, but rather a constant in the equation. The equation is explained as an intermediate step in a calculation, and the conversation ends with a suggestion to read an early paper on the topic for a better understanding.
  • #1
Cosmic Philo
3
0
I tried to find an answer to this here, but may have missed it.

There must be a flaw in my understanding here, since it seems to be contradictory. Mass times the speed of light squared = Energy, and yet (according to Einstein), nothing can travel faster than the speed of light?

I'm just curious also if anyone has a link handy, what is the equation that led to the famous e = mc^2 formula or are there a series of equations?
 
Physics news on Phys.org
  • #2
Cosmic Philo said:
There must be a flaw in my understanding here, since it seems to be contradictory. Mass times the speed of light squared = Energy, and yet (according to Einstein), nothing can travel faster than the speed of light?

Why do you think there is a contradiction?
 
  • #3
Of course the speed of light squared is much faster than the speed of light, and yet nothing can go the speed of light (much less that speed squared). If c^2 is impossible, what is the use of the famous equation?

But I must be misunderstading something (or everything! :-D).
 
  • #4
1. c^2 is not a speed. It has units of m^2 / sec^2, whereas speed has units of m/sec.

2. Even if it were a speed, simply because c^2 appears in an equation does not mean that anything is actually traveling at that speed.
 
  • #5
jtbell said:
1. c^2 is not a speed. It has units of m^2 / sec^2, whereas speed has units of m/sec.

2. Even if it were a speed, simply because c^2 appears in an equation does not mean that anything is actually traveling at that speed.

That helps, thanks. I've beeen reading various books about physics and trying to grasp the main concepts. So somehow it works out that c^2 works in the formula as a static amount. I was under the impression that moving mass that fast would create energy (i.e., turn the mass into energy).
 
  • #6
You're looking at an intermediate step in a calculation, not the input value. The input value is the speed of light, not the speed of light squared. You can also enter any actual speed into the equation and get the energy equivalent -- but entering 10 m/sec means your object is moving at 10 m/sec not 100 m/sec (or m^2/s^2).
 
  • #7
Cosmic Philo said:
That helps, thanks. I've beeen reading various books about physics and trying to grasp the main concepts. So somehow it works out that c^2 works in the formula as a static amount. [..].

c (or c0) is an electromagnetic vacuum constant, related to the impedance of free space; it just happens to correspond to the speed of light in vacuum. See for example:

http://en.wikipedia.org/wiki/Electromagnetic_wave_equation
http://en.wikipedia.org/wiki/Impedance_of_free_space

PS. the first (?) paper that precisely led to the mass-energy equation is rather complex, but even reading it diagonally may give you a feeling for how it was done:
http://www.fourmilab.ch/etexts/einstein/E_mc2/
 

1. What does the equation E=mc^2 mean?

The equation E=mc^2 is known as the mass-energy equivalence equation and it shows the relationship between mass (m) and energy (E). It states that energy and mass are interchangeable and can be converted into one another.

2. How does the equation E=mc^2 relate to the speed of light?

The speed of light (c) is a constant in the equation, and it represents the maximum speed at which anything can travel in the universe. This means that the equation shows the maximum amount of energy that can be obtained from a certain amount of mass, and vice versa.

3. Can anything travel faster than the speed of light?

According to the theory of relativity, nothing can travel faster than the speed of light. The speed of light is considered to be the ultimate speed limit of the universe and is believed to be impossible to surpass.

4. What happens if an object reaches the speed of light?

If an object were to somehow reach the speed of light, it would require an infinite amount of energy. This is because as an object approaches the speed of light, its mass increases and it would take an infinite amount of energy to accelerate it to the speed of light.

5. How does the equation E=mc^2 contribute to our understanding of the universe?

The equation E=mc^2 is a fundamental principle in physics and has greatly contributed to our understanding of the universe. It explains the relationship between mass and energy and has led to advancements in fields like nuclear energy and particle physics. It also plays a crucial role in the theory of relativity and has helped us understand the behavior of objects at high speeds and in extreme conditions.

Similar threads

  • Special and General Relativity
2
Replies
40
Views
2K
Replies
6
Views
1K
  • Special and General Relativity
Replies
9
Views
1K
  • Special and General Relativity
Replies
14
Views
1K
  • Special and General Relativity
Replies
17
Views
2K
  • Special and General Relativity
Replies
8
Views
957
  • Special and General Relativity
Replies
32
Views
2K
  • Special and General Relativity
Replies
19
Views
1K
Replies
18
Views
2K
  • Special and General Relativity
Replies
8
Views
1K
Back
Top