We can never reach the speed of light. Or, more accurately, we can never reach the speed of light in a vacuum. That is, the ultimate cosmic speed limit, of 299,792,458 m/s is unattainable for massive particles, and simultaneously is the speed that all massless particles must travel at.
Nothing can travel faster than 300,000 kilometers per second (186,000 miles per second). Only massless particles, including photons, which make up light, can travel at that speed. It's impossible to accelerate any material object up to the speed of light because it would take an infinite amount of energy to do so.
Einstein also said our universe has a speed limit: nothing can travel faster than the speed of light (186,000 miles per second). What does this mean for time travel? Well, according to this theory, the faster you travel, the slower you experience time. Scientists have done some experiments to show that this is true.
If an object ever did reach the speed of light, its mass would become infinite. And as a result, the energy required to move the object would also become infinite: an impossibility.
Light-year is the distance light travels in one year. Light zips through interstellar space at 186,000 miles (300,000 kilometers) per second and 5.88 trillion miles (9.46 trillion kilometers) per year.
If you travelled at the speed of light, how would you experience time? Travelling in space for three years at close to the speed of light would equal five years on Earth. This indicates how an astronaut might age on a long space journey.
At any rate, the beam of light emitted by your flashlight would appear to reach the far wall instantly, as the speed of light is independent of your speed and would always be constant at about 300,000 kilometres per second in a vacuum.
In special relativity, the speed of light is the ultimate speed limit to the universe. Nothing can travel faster than it.
At 99.99999 percent of the speed of light, for a year, more than 2000 years would pass on Earth. The point is, the closer you get to the speed of light, the more time dilation is experienced. Achieving those speeds, however, is incredibly unlikely and probably impossible.
So light is the fastest thing. Nothing can go faster than that. It's kind of like the speed limit of the universe.
The speed limit is a harsh reality
The reason that it is hard to travel through space at the speed of light is that you must push the object out of moving in the time direction to moving more in the space direction.
NARRATOR: If we could experience the world the way a ray of light does, the world would look completely different. At near light speed, we'd hardly recognize familiar surroundings. Likewise, the Doppler effect would make objects so bright, we couldn't recognize anything at all.
Darkness travels at the speed of light. More accurately, darkness does not exist by itself as a unique physical entity, but is simply the absence of light. Any time you block out most of the light – for instance, by cupping your hands together – you get darkness.
So, yes, for really large distances you could say that the Universe is expanding faster than light.
We can never reach the speed of light. Or, more accurately, we can never reach the speed of light in a vacuum.
From the perspective of a photon, there is no such thing as time. It's emitted, and might exist for hundreds of trillions of years, but for the photon, there's zero time elapsed between when it's emitted and when it's absorbed again.
Because of the physical differences in the makeup of the materials light actually travels slower through water and glass. Speed of light in a vacuum and air = 300 million m/s or 273,400 mph. Speed of light in water = 226 million m/s or 205,600 mph. Speed of light in glass = 200 million m/s or 182,300 mph.
Albert Einstein's special theory of relativity states that photons—or particles of light—travel at a constant speed of 670,616,629 miles per hour. As far as we know, nothing can travel faster than this. But across the universe, particles are often accelerated to 99.99 percent the speed of light.
Q: Which object travels faster than light? The controversial hypothetical particles Tachyons are said to travel faster than light. However, according to Einstein's special theory of relativity particles regarding speed of light, they can never travel faster than light in the real world.
Gamma Rays! A flash of lightning.
speed of sound, speed at which sound waves propagate through different materials. In particular, for dry air at a temperature of 0 °C (32 °F), the modern value for the speed of sound is 331.29 metres (1,086.9 feet) per second.
Time Travel
Special relativity states that nothing can go faster than the speed of light. If something were to exceed this limit, it would move backward in time, according to the theory.
Felix Baumgartner, a skydiver from Austria, achieved faster-than-sound speed during his famous supersonic freefall in 2012. If you are thinking about trying it our yourself, keep in mind that you will need an air balloon and a pressure suit.