Can anything travel faster than light?

In one line

The rule

According to Einstein's theory of relativity, no object with mass can reach or exceed the speed of light in a vacuum (about 3,00,000 km/s).

The formula for the energy needed to move an object is: E = mc² / √(1 - v²/c²) where:

• E = energy needed
• m = mass of the object
• v = speed of the object
• c = speed of light (about 3 × 10⁸ m/s)

Let's understand it simply

Imagine you are pushing a cycle. At first, it is easy to make it go faster. But as you try to push it closer and closer to the speed of light, it gets harder and harder. It is like the cycle is getting heavier and heavier. No matter how hard you push, you can never make it reach the speed of light.

Think of the speed of light as the fastest train on the tracks. No other train (object) can ever go faster than this train, no matter how powerful its engine is. The tracks (the laws of physics) simply do not allow it.

How it works

1. Light in a vacuum always travels at the same speed: about 3 × 10⁸ m/s (3 lakh km/s).
2. When you try to make something with mass go faster, you must give it more energy.
3. As it gets closer to light speed, it needs much more energy for each small increase in speed.
4. At the speed of light, the energy needed becomes infinite (never-ending).
5. Since you can never give infinite energy, nothing with mass can reach or cross the speed of light.

The story behind it

Albert Einstein, a German-born physicist, developed the theory of special relativity in 1905. He was trying to solve problems about how light and motion work together. Before Einstein, people thought speeds could just add up (like running on a moving train). But light did not behave this way. Einstein showed that the speed of light is always the same, no matter how you move, and this changed our understanding of space and time forever.

Where you see it in real life

• Mobile networks: Signals travel as electromagnetic waves (like light), but never faster than light.
• Watching cricket on TV: The match is shown almost instantly, but there is always a tiny delay because signals cannot travel faster than light.
• Lightning and thunder: You see the lightning before you hear the thunder because light travels much faster than sound, but still not instantly.
• GPS in your phone: GPS satellites use the speed of light to calculate your position. Even a small delay matters.
• Fiber-optic internet: Data travels as light through cables, but always below the speed of light in a vacuum.
• Diwali rockets: Even the fastest rocket cannot come close to the speed of light.

Why it matters

• Technology: All our communication systems (internet, TV, phones) depend on the speed of light.
• Space travel: It sets a limit on how fast we can send spacecraft to other planets or stars.
• Physics: Many modern theories (quantum physics, relativity) are built on this rule.
• Exams: Questions about relativity, speed limits, and energy often appear in board exams and competitive tests.

Worked example

Let's see what happens if you try to accelerate a 1 kg object to the speed of light:

Given: m = 1 kg, v = c (speed of light)
Step 1: Write the rule        E = mc² / √(1 - v²/c²)
Step 2: Substitute v = c      E = mc² / √(1 - c²/c²)
Step 3: Simplify denominator  √(1 - 1) = √0 = 0
Step 4: Division by zero      E = mc² / 0 → infinite energy
Step 5: Conclusion            It is impossible to reach light speed

Common mistakes

• Thinking rockets or spaceships can go faster than light: Even the fastest rocket is millions of times slower than light.
• Believing light can go faster in other materials: Light actually slows down in glass or water; only in a vacuum does it reach its top speed.
• Confusing 'information' or 'shadow' with real objects: Sometimes, a shadow or a laser spot can move quickly across a wall, but no actual object or information travels faster than light.
• Misunderstanding science fiction: Movies often show spaceships jumping to 'warp speed', but this is not possible with our current understanding of physics.

Remember it

Nothing with mass can ever go faster than light—it's the universe's speed limit.