quantumaniac:

How Much Does Fire Weigh? 

Question: Since fire is a plasma, and plasma is a state of matter, and matter is defined as anything that has mass, would that then mean that fire has mass and weight to it? If so, is there a way to measure its weight? How much space would, say, a pound of fire take up?

Answer: It weighs more than nothing, but if you’re at the bottom of a pillar of fire, being crushed should be your second concern

Fires, putting aside details about plasma and chemicals or whatever, is just hot air.  For a given pressure the ideal gas law says that the density of a gas is inversely proportional to temperature, in Kelvin.  You can use this fact, the temperature and density of air (300°K 1.3 kg/m³), and the temperature of your average run-of-the-mill open flame (about 1300°K) to find the density of fire. For most “everyday” fires, the density of the gas in the flame will be about 1/4 the density of air.  So, since air (at sea level) weighs about 1.3 kg per cubic meter (1.3 grams per liter), fire weighs about 0.3 kg per cubic meter.

One pound of ordinary fire, here on Earth near sea level, would take up a cube about 1.2 meters to a side.  The reason that fires always flow upward is that its density is lower than air.  So, fire rises in air for the same reason that bubbles rise in water: it’s buoyant.  Enterprising individuals sometimes even take advantage of that fact.

If you were on a planet with no air at all, fire would fall to the ground instead of rise because, like all matter, it’s pulled by gravity.  Also, it would be hard to keep the fire going (what with there being no air).

quantumaniac:

Scary Movies about to get Much Scarier

During the Sundance Film Festival in January, a midnight screening of V/H/S provoked the ultimate audience reaction of the horror movie genre. Some scenes were so graphic and gory that a man ran from the theater, collapsed in the lobby and had a seizure. His girlfriend followed suit and vomited while he was being treated. An ambulance even had to be called.

Fortunately, the man and his girlfriend were fine after being treated by paramedics. Unfortunately, horror movies are about to get even more nauseating thanks to the latest technology from Dolby Laboratories. But if you’re a fan of seizure-inducing horror movies, consider it your lucky day.

On Monday the company revealed its new sound system call the Dolby Atmos, capable of pumping out sound how we naturally hear it: from every direction. Unlike current sound systems that push sound from the sides of theaters, the Atmos system can not only deliver sound from above, it will be able to swirl sound around the theater.

Senior technical marketing manager for Dolby Laboratories, Stuart Bowling, said the new Atmos system is one of the biggest technological advances the company has made in the last 20 years.

“You can imagine watching a scary movie, and it’s a scene when someone is hiding in a basement and there are footsteps on the floorboards above,” Bowling said, according to the New York Times. “The Atmos system will actually play that audio from above people in the theater.”

The new system will feature 64 speaker feeds and will be in select theaters later this year.

“Dolby Atmos is our most significant innovation in years and represents the future for entertainment sound in cinema,”  President and Chief Executive Officer, Dolby Laboratories, Kevin Yeaman said in a press release. “We have leveraged our deep insights into how people hear and experience sound to empower filmmakers, studios, and exhibitors with new technology that transforms storytelling.”