I had to set the record straight.
Don't get me wrong, there is nothing wrong with the guy's physics (for the most part), it's his application of the physics that is lacking.
There are a number of flaws in the arguments presented.
Firstly, the author posits a high-frequency beam would be superior to a low-frequency beam. While it is true that the energy of the beam is higher for higher frequencies, this says nothing about the beam intensity. The more power my beam has, the more energy it delivers per second. Physics defines power as energy delivered per second. So a high intensity, low frequency beam can deliver much more of a blow than a low intensity, high frequency beam. This is why we can look at a purple light but not at a powerful red laser. If I have technology that produces high intensity beams, I don't really care what the frequency is.
Where it makes sense that different 'races' would use different light frequencies is in protecting their own ships. Just as the skin of a stealth bomber is designed to absorb radio frequencies to make them difficult to detect by radar, spaceships could design their skins to reflect the frequencies of their own weapons to avoid loss from 'friendly fire'.
The reason microwave ovens are so effective, despite using a longer wavelength than the infrared radiation of a typical oven, is that water absorbs microwave energy really well. If I'm using microwave beams, I want to be hitting ships that absorb like water.
The author also suggests red light is 'slower' than violet light. In a vacuum, all light moves at the same speed, namely the speed of light (c). Even in the air they move at practically the same speed and the difference in velocity certainly has no impact on their performance as a weapon.
The author then moves on to kinetic energy weapons, referring to weapons which make a mass move rapidly and cause damage by coming to a rapid stop, delivering their energy to the target. He says they are the basis for virtually all our killing devices for the last 5,000 years.
The fact is most modern day weapons do not fall into this category, other than conventional bullets. Rockets and missiles do not do their damage because of their speed, but because of the explosive charge in them. It is the rapid release of chemical energy on impact that does the damage. Also, the ultimate weapon of mankind, the nuke, doesn't even hit their targets physically. Nuclear devices are detonated in the atmosphere above their targets and it is the release of energy which either irradiates its target or blasts it with the shock wave. Nuclear bombs are an energy weapon and they are much more powerful than a practical kinetic equivalent. The Hiroshima bomb contained just 64kg of uranium of which just 0.6g was converted into energy. 0.6 grams (0.02 ounces) destroyed an entire city. It is easier to destroy stuff by converting mass into energy and rapidly releasing that energy than throwing the same amount of mass at something.
The exception to this rule is referred to in the video. If I'm bombarding a planet, all I have to do is nudge a large mass towards the planet and gravity will do the rest. The thing is while this is good if I'm sitting on the moon and have a large supply of big rocks, this is completely impractical for a spacecraft.
However, let us say I am towing a collection of boulders behind me while exploring the less civilised regions of the galaxy and I want to accelerate them. I still need a good supply of energy to do this. Let's say I now throw this boulder at a particularly aggressive alien some distance away (this is space after all). What happens if the alien moves? We need to pump in a bunch more energy to make the mass change its course. Or I could simply put the same energy into my energy weapon, rapidly change its direction and knock out the interstellar blackguard.
In short, if I'm attacking a planet, the planet's gravity will do the heavy lifting, if I'm a spaceship I have to do it all myself. Velocity may be easy but nuclear fusion is much easier than accelerating a decent sized object to near-light speeds without the help of gravity and beam weapons are a lot more manageable than fast moving rocks.
The other disadvantage is accelerating masses in space introduces a finite resource. Whether we use an energy weapon or rocks, we need a significant source of energy but if we are using rocks, and we run out of rocks, we are a sitting duck.
Finally, the video suggests the kinetic energy of a mass travelling as fast as physics allows is (1/2)mc^2. When masses move at near light speed the 'easy physics' no longer applies and a new physics called Special Relativity kicks in. The fact is masses moving at near light speeds store energy far in excess of (1/2)mv^2, but the fact is you have to pump the energy in for the mass to release it on your enemy so why not use it in the form of an energy weapon?
In conclusion, all conventional weapons rely on delivering a large amount of energy in a short amount of time to a target. Kinetic weapons do this by being thrown. Explosive weapons generally do this through chemical reactions and nuclear weapons do this by converting mass into large amounts of energy. In all cases we need a source of energy and generally the denser the better.
The reason to choose one form of weapon over another are reasons of practicality and efficiency. It is practical and efficient to drop rocks on a planet. It is practical to nuke cities rather than try to accelerate the same, tiny mass to inflict the same damage. It is not practical for a spaceship to carry rocks around, accelerate them and throw them at enemies if they have the ability to deliver the energy directly in the form of an intense beam of radiation.
Also, a visible beam weapon is not ruled out by considerations of frequency employed but more by the ability to efficiently generate an intense beam of energy. There is no doubt that sparkly weapons used in movies are there for the audience first and consider physics, if at all, a distant second but physics does not rule out the possibility as suggested.
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