The equation — E = mc2 — means “energy equals mass times the speed of light squared.” It shows that energy (E) and mass (m) are interchangeable; they are different forms of the same thing. If mass is somehow totally converted into energy, it also shows how much energy would reside inside that mass: quite a lot.

E = mc2. It’s the world’s most famous equation, but what does it really mean? “Energy equals mass times the speed of light squared.” On the most basic level, the equation says that energy and mass (matter) are interchangeable; they are different forms of the same thing.

A: The light from a laser in space would continue on forever unless it hit something. However, if you were far enough away, you wouldn’t be able to detect the light. A projectile would also continue on forever unless it hit something.

In the United States, there is a federal law that makes it illegal to aim a laser pointer at an aircraft, or the flight path of an aircraft.

Class IIIb lasers cannot legally be promoted as laser pointers or demonstration laser products. Higher powered Class IIIb or IEC Class 3B lasers are dangerous and can cause either temporary visual effects or an eye injury.

While it may seem extreme to criminalize pointing a laser at an aircraft, the reason for these laws is to deter extremely dangerous behavior. Studies have shown that these lasers cause severe glare in the cockpits, essentially temporarily blinding airplane pilots for periods at a time.

So what’s the difference between class III and class IV lasers? The biggest difference is their maximum power output. The FDA defines a class IIIb laser as a device with a power output between 5-500mW (0.005-0.5W), and a class IV laser as a device with a power output above 500mW (0.5W).

We use class 4 laser therapy on a range of issues including chronic knee pain or arthritis, chronic Achilles tendonitis, elbow pain or tendonitis in the elbow, and chronic wrist pain. We are able to use the class 4 laser on a wide range of injury sites and extremities to provide relief to our patients.

Class 4 visible-light lasers are significantly hazardous for eye exposure. They can cause burns to the retina. A person cannot turn away or blink fast enough to prevent retinal eye injury from a Class 4 laser. Prevent all eye exposure to beams from Class 4 lasers.

Class 3B lasers can heat the skin and materials if the beam remains on the object at a close range. The distance Class 3B laser beams can travel to is up to 116,890 feet or 99 miles. These lasers should not be used for pointing due to their power and heat capabilities.