Ask a Scientist: Weight at the Equator

By Admin | Published: May 15, 2012

Question:
What would be the difference in my weight (force) between standing at the equator vs standing at one of the poles? I suspect I would weigh less at the equator due to the centrifugal force. Say I weigh 80 kg.

Answer:
At first glance, yes you would weigh a very small amount less at the equator, but one day of over-eating on the airplane to the pole, or of strenuous sweating exercise, will easily mask the predicted weight difference. This answer considers the effect of rotation at the equator, that uses “approximate values” for factors, and ignores the non-spherical nature of the earth and other effects. This simple approach compares

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Ask a Scientist: Laser Beam

By Admin | Published: March 6, 2012

Question

What happens to air as a laser beam travels through it?

Answer

This depends on the wavelength of the laser beam.

As this pictureshows: http://fuse.pha.jhu.edu/~wpb/spectroscopy/figures/trans.gif, there are very narrow windows in which laser light can pass (i.e. the atmosphere is transparent and has no effect on the laser light). By contrast, where the atmosphere is “opaque”, all the light is absorbed by the atmosphere. Of course, air is composed of several different gases, each of which respond differently to different wavelengths of laser light. So, depending on the wavelength, the laser will either interact with the gas or it won’t.

For example, one can consider a typical microwave oven and how it works to heat food. Microwaves, as found in a microwave oven (122mm wavelength), interact and are absorbed by water molecules causing them to vibrate more vigorously, resulting in heat, but leave the other food molecules unchanged. By the same token, a laser beam of the appropriate wavelength can interact with one of the gases in air causing the air to heat up (absorption), refract or reflect the light (change the direction in which the light is moving), or even change the wavelength of the light (change of colour of the laser beam).

- Kevin Shortt

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Ask a Scientist: Large Hadron Collider

By Science.gc.ca | Published: September 30, 2011

Question: If particles in the LHC are circulation in opposite directions near the speed of light, is their relative speed almost twice the speed of light when they collide?

Answer by Dr. James Di Francesco: That would be true following the classical physics of our everyday world.  Over the last 100 years, however, we have learned that Nature acts in a much more peculiar way when objects gain speeds close to the speed of light.  Following Einstein’s Special Theory of Relativity, space and time themselves distort so no object can appear to be moving faster than the speed of light.  So, from the perspective of either particle, the other actually appears to approach it at a speed very close to the speed of light, not twice that.  (Since the particles have finite mass, they cannot actually reach the speed of light itself, just get very close.)

You may have recently heard news about European observations of subatomic particles where the speed of light was exceeded.  If true, this measurement could lead to serious reconsiderations of Einstein’s theories which until now had been proven to high degree of precision in many experiments.  Although these recent measurements have been examined carefully for flaws by the scientists involved, none have been found.  It still remains possible, however, that their measurements were off by an unusual statistical fluke.  Repeat, independent experiments are planned to revisit their findings.

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Ask a Scientist: Absolute Zero

By Science.gc.ca | Published: September 29, 2011

Question: Can it get more colder than absolute zero is this where the temperature stops?

Answer by Dr. James Di Francesco: No, it can’t get colder than absolute zero. The temperature of a substance is defined by the motion energy of particles that make up that substance. The coldest temperature on the temperature scale, -273 C or absolute zero, is defined as the point where the motions of particles become effectively zero. Indeed, the qualities of matter at such low temperatures can be quite unusual (e.g., superconductivity, bose-einstein condensates) and are still being actively studied today in condensed matter physics laboratories.

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Ask a Scientist: Gravity

By Science.gc.ca | Published: October 2, 2009

Question submitted by Peter:

I have read a great deal about the cause of gravity, including Einstein’s theory of curved space/time and attraction of large objects. I have the impression that scientists really do not know what is the cause. Is there some truth in that impression?

Response by Pauline Barmby:

There is indeed some truth to that impression. But I think you could also say it applies to all scientific explanations. Eventually if you keep asking “what is the cause,” you get to the answer “that’s just the way the universe is”. Some people would try to address this with something called the “anthropic principle”: “the universe is the way it is because otherwise we wouldn’t be here to observe it”. Not everyone finds this idea convincing.

As working astrophysicist, I tend to leave questions like yours to people who study the philosophy of science. I am content to accept that there is gravity, for which Einstein’s theoryof general relativity is the best current description we have,and to try and figure out its observable consequences. It’s not that these deeper questions are not important, but a typical scientist’s training doesn’t equip us to address them.

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