## Physics Photo Phriday (August 10, 2012)

So the big news this week of course is the successful landing of the Curiosity rover on Mars.  It is an incredible achievement, and the excitement of the landing all over the world is truly heartwarming.

So the photo this week is my favourite image (so far) of the Curiosity landing. It was actually taken by the Mars Reconnasaince Orbiter, a satellite in orbit around Mars which was diverted to just the right spot at just the right time to capture the landing.

The Mars Reconnaissance Orbiter captures the parachute of the Curiosity landing. Amazing! Credit: NASA/JPL-Caltech/Univ. of Arizona

Now we just sit back and wait for the evidence of water on Mars…

## Physics Equation Wednesday: Newton’s Second Law

I’ve decided to start another weekly post topic entitled “Physics Equation Wednesday”. As you might guess, every Wednesday I will show and explain a different physics equation.

Today we start with a classic, Newton’s Second Law (in the form in which most people first see it)

$\vec{F}_{net} = m\vec{a}$

In this equation, Fnet is the net external force experienced by an object, m is the mass of the object, and a is the object’s acceleration.

In Newton’s Principia Mathmatica, he states

Lex II: Mutationem motus proportionalem esse vi motrici impressae, et fieri secundum lineam rectam qua vis illa imprimitur.

Which in modern day terms simply says that the net force on an object is equal to it’s mass times it’s acceleration, and the acceleration is in the direction of the net force.

It may seem like a simple idea, and a simple formula, but it is one of the most widely used ideas in physics. It even forms the basis of an entire branch of physics, Classical Mechanics, which describes the motion of groups of objects.

So what do we mean by “net force”? Well the idea is that you add up all forces acting on an object vectorially (i.e. add up all the force components in the x-direction and all the force components in the y-direction)  and what you end up with is the net force.

Here’s an example. Let’s say you are moving out of your apartment and there is a particularly heavy box in the kitchen. It is heavy because even though your girlfriend warned you not to pack all the heavy dishes in one box, you went ahead and did it anyway (yes, I’ve experienced this first hand).

When the box is just sitting on the ground, the force of gravity pulling it down is exactly matched by the force of the floor holding it up (called the normal force).

$F_{gravity} = F_{floor}$

Since all the forces are balanced, the net force is zero and the box does not move.

$\vec{F}_{net} = 0$

Now, if you try to lift the box straight up, it doesn’t go anywhere. That is because the force of gravity pulling the box down is greater than your lifting force. The box stays firmly planted on the ground, because the normal force of the floor combined with your lifting force will still exactly match that of gravity.

$F_{gravity} = F_{lifting} + F_{floor}$

Again, the net force is zero, so the box does not move.

So naturally you now try to push the box across the floor. At first, it doesn’t move at all, even though you are pushing will all your might. This is because the force of friction between the box and the floor is greater than you pushing it. The net force in this case is zero, since the force of friction is exactly matching your pushing force. Since the net force is zero, the box stays firmly in place.

$F_{push} = F_{friction}$

Finally, after remembering that you watched The Incredible Hulk last night, you summon some mighty strength and with a loud grunt you increase the force of your push. Now the force of your pushing is greater than the force of friction, so the net force is in the direction of your push and the box will accelerate in the direction of the push.

$F_{push} - F_{friction} > 0$

$\vec{F}_{net} > 0$

The unit we use to measure force is called the ‘Newton’, after Sir Isaac Newton. One Newton of force is defined as the amount of force it takes to accelerate a 1 kilogram object at 1 meter per second per second.

That is pretty much the first lesson any new student in physics will get. Newton’s laws are relatively simple and easy to use, making them ubiquitous in many areas of physics.

## TOUCHDOWN!!!

The Curiosity rover has landed safely on the surface of Mars!

I'm safely on the surface of Mars. GALE CRATER I AM IN YOU!!! #MSL
@MarsCuriosity
Curiosity Rover

Screengrab of the live NASA TV feed of the Curiosity landing. In the foreground you see celebrating mission controllers, and in the background the first image from the rover, showing it is safely sitting on the Martian surface.

Now, I’m going to bed. More in the morning! Woohoo!

## Mars Science Laboratory Landing Today!

Well, hopefully.

Landing on another planet is about as easy as it sounds, which is not at all. But the MSL will be entering Mars’ atmosphere this evening and if all goes according to plan, we will have a new Mars rover bombing around on the surface!

The Mars Science Laboratory Curiosity rover when deployed. Photo: NASA/JPL

What is Curiosity looking for?

Curiosity was designed to assess whether Mars ever had an environment able to support small life forms called microbes. In other words, its mission is to determine the planet’s “habitability.”

Of course, getting to Mars and landing on it is a very delicate operation.

Curiosity is scheduled to land around 11:30 PM PDT. I will be nerding it up and staying up late to watch the landing. You can watch live on NASATV.

Also, Fraser Cain, Pamela Gay, Philip Plait and Miles O’Brien will be doing a Google+ hangout to discuss the event as it happens.

## Physics Photo Phriday (August 3, 2012)

This week, the manuscripts for papers describing the discovery of a boson, possibly the Higgs, of a mass of around 125 GeV from both the ATLAS and CMS experiments are online.

Results of the diphoton decay path from the ATLAS experiment. The theoretical background results are the dashed line (assuming no boson) and experimental results (blue line). The “bump” in the data (highlighted by me with a green arrow) indicates the presence of a boson at approximately 125 GeV.

Combined results from 5 decay paths from the CMS experiment. The background-only expectations are represented by their median (dashed line) and by the 68% and 95% CL bands. Again, note the excess in the experimental data around a mass of 125 GeV, indicating the presence of a boson.

Both manuscripts are expected to be published in Physics Letters B.

The CMS experiment ended up having a statistical significance of 5.0σ, and the ATLAS experiment a significance of 5.9σ.

London, UK, from space. Photo: NASA

This week, we have the physics of firewalking, another protest against research cuts in Canada, and NASA releases photos of Olympic host cities…from space!

Physics

Assessing Risk in Costing High-energy Accelerators: from Existing Projects to the Future Linear Collider

The Physics of Firewalking

The truth behind TSA back scanners. Are they safe?

21 people had to be treated for burns from walking over hot coals at a Tony Robbins inspirational event.

Astronomy

Saskatchewan researchers find meteor crater in Arctic

New NASA telescope has key Canadian parts

NASA Releases Satellite Photos of Olympic Host Cities

The Apollo 11 Journey in Photographs

Health/Environment

SOS formed in protest of science cuts

Washington pertussis outbreak is very, very bad

Anti-Fluoride Propaganda as News

Sudden massive melt of Greenland ice sheet surprises scientists

Lightning Captured at 7207 Images per Second

Fun/Funny

10 Scientific Missions That Became Action Adventures

Is that guy threatening you? Or is it that extra cup of coffee?

Harry Potter And The Ten Years Later – Episode One

What’s the best contraption for a trip over Niagara Falls?

Music Was Better in the Sixties, Man

## Physics Photo Phriday (July 27, 2012)

In July of 1969, Apollo 11 became the first manned spacecraft to land on the moon.

The Lunar Module ascends from the Moon’s surface to dock with the Command Module. Photo: NASA

While we have not landed humans on any other planetary body since the Apollo program, in 10 days the Mars Science Laboratory will be landing on the surface of Mars.

## Canada to Fund Study on Health Effects of Wind Turbines

In southwestern Ontario, if you turn north of the 401 and head up towards the Bruce peninsula, you will eventually stop seeing familiar farmland and your eye will be drawn to the towering wind turbines which dot the landscape.

The turbines supplement the nuclear power plant located in Kincardine, Ontario. Wind power has been heralded as a potential untapped resource for sustainable energy. With no pollution and no nuclear waste to contend with, what could possibly go wrong?

But residents nearby have claimed that the noise from the turbines is causing adverse health effects. Headaches, migraines, nausea and other non-specific symptoms are being blamed on the presence of the turbines.

Health Canada has recently announced that it will fund a two-year study on the health effects of the turbines on the nearby residents. In the meantime, a moratorium on the construction of new turbines is being proposed until the study is complete.

Shawn and Tricia Drennan’s farm sits in the proposed Kingsbridge II wind farm and one turbine will be about 650 metres from their house. Shawn Drennan says they heard some people living near an earlier wind farm project sold their properties to the wind farm operator after suffering health problems.

This couple heard through the grapevine that their neighbours sold their house because of the turbines. Anyone who reads this blog knows how I feel about anecdotal evidence. I prefer real scientific studies.

But a large amount of study has already been done in this area. So what does it say?

A review of the literature from the journal Environmental Health in 2011 stated that

While it is acknowledged that noise from wind turbines can be annoying to some and associated with some reported health effects (e.g., sleep disturbance), especially when found at sound pressure levels greater than 40 db(A), given that annoyance appears to be more strongly related to visual cues and attitude than to noise itself, self reported health effects of people living near wind turbines are more likely attributed to physical manifestation from an annoyed state than from wind turbines themselves. In other words, it appears that it is the change in the environment that is associated with reported health effects and not a turbine-specific variable like audible noise or infrasound. [emphasis mine]

So the negative of effects of the wind turbines had more to do with the attitude of the person towards the wind turbines, rather than the turbines themselves.

The World Health Organization held a workshop in 2004 to discuss the reports of adverse health effects of wind turbines. They found several things; first

The term “Iditopathic Environmental Intolerance (IEI) with attribution to EMF (electromagnetic fields)” was proposed by the working group to replace EHS (electromagnetic hypersensitivity) since the latter implies that a causal relationship has been established between the reported symptoms and EMF.

So the attendants of the workshop found that since there was no causal relationship between EMF and adverse health effects, a new term should be used to describe those who believe they are afflicted with such an ailment. This was to stop the proliferation of the idea that low-frequency EMF from power sources could cause adverse health effects. Further,

The majority of studies indicate that IEI individuals cannot detect EMF exposure any more accurately than non-IEI individuals. By and large well controlled and conducted double-blind studies have shown that symptoms do not seem to be correlated with EMF exposure.

There are also some indications that these symptoms may be due to pre-existed psychiatric conditions as well as stress reactions as a result of worrying about believed EMF health effects, rather than the EMF exposure itself. It was added that IEI should not be used as a medical diagnosis since there is presently no scientific basis to link IEI symptoms to EMF exposure. [emphasis mine]

Studies from Sweden and the Netherlands also found that the level of “annoyance” associated with nearby wind turbines is largely affected by the subject’s views on the presence of the turbines. The study from the Netherlands stated that

High turbine visibility enhances negative response, and having wind turbines visible from the dwelling significantly increased the risk of annoyance. Annoyance was strongly correlated with a negative attitude toward the visual impact of wind turbines on the landscape. The study further demonstrates that people who benefit economically from wind turbines have a significantly decreased risk of annoyance, despite exposure to similar sound levels [emphasis mine]

So does this mean that the symptoms the residents of rural Ontario are experiencing are not real? Are they just exaggerating?

The symptoms they are describing are indeed real, but seem to have little to do with any EMF or sound generated by the wind turbines.

It is likely that any unexplained symptom experience by residents near a wind turbine, be it nausea or migraine or the like, they blame on the presence of the turbine. It is classic post hoc ergo propter hoc logic: the turbine was built, now I have a headache, therefore the turbine caused my headache.

But it is a tough situation. How do you tell someone that their headache is not being caused by a wind turbine, but by their negative attitude towards the turbine? I cannot see that conversation going well. I imagine the situation would be quite similar if a highway were being built behind these people’s houses. But does that mean we should stop building roads?

Will a two-year study by Health Canada convince anyone? I don’t think so. If the study shows there is no adverse health effect of the turbines, residents are just going to get more upset and say the study is wrong. If the study shows that there is an effect, it will be heralded by the few that believe in it, but will be criticized by the scientific community, and will still only be a single study in a large body of evidence, therefore proving nothing.

I can understand being upset at the construction of the turbines, I really can. If a new condo development sprang up behind my apartment, I would be pretty upset as well. But you can only delay progress for so long. Renewable energy is the wave of the future and we are going to have to learn to accept it. You can say “Not In My Back Yard” all you want, but eventually we all just need to learn to adapt.

This week, we have a Do-it-Yourself spectrometer, a study on the health effect of wind turbines, and XKCD asks how much power Yoda can produce with the Force?

Physics/Astronomy

DIY Spectrometer

Imaging electronic quantum motion with light

5 Sigma — What’s That?

How much Force can Yoda output?

Dark Matter Still Hiding

Skepticism

Wind farm opponents cheer federal study of health effects

The HCG Diet: Another ineffective and possibly dangerous diet plan

Teaching creationism: Indoctrination is a form of child abuse
Health

France’s 20th Century Radium Craze Still Haunts Paris

Fukushima’s disease risk: A major fallout?

CDC: Whooping cough rising at alarming rate in US; this could prove the worst year since 1959

Fun/Funny

What’s the best contraption for a trip over Niagara Falls?

After 25 years trapped in woman’s stomach, lost pen still writes

Exploding a Watermelon With Rubber Bands in Slow Motion.

The Most Popular New Baby Names of 2012: Arya… and Theon?

The First Ever Self-Chilling Can

## Physics Photo Phriday (July 20, 2012)

Credit: NASA, ESA, and M. Showalter (SETI Institute)

Last week, astronomers using the Hubble Space Telescope announced the discovery of a fifth moon around Pluto!

From the Hubble website,

The moon is estimated to be irregular in shape and 6 to 15 miles across. It is in a 58,000-mile-diameter circular orbit around Pluto that is assumed to be co-planar with the other satellites in the system. Provisionally designated S/2012 (134340) 1, the latest moon was detected in nine separate sets of images taken by Hubble’s Wide Field Camera 3 on June 26, 27, and 29, 2012 and July 7 and 9, 2012. This discovery increases the number of known moons orbiting Pluto to five.

How such a small body such as Pluto can have such a complicated array of moons is a bit of a mystery. The current theory is that Pluto collided with another object from the Kuiper belt to create such a strange system of moons.