The Awareness Series: how GPS works

ISRO’s launching of seventh navigation satellite has been in news recently. It’s a proud moment for us Indians to have our own GPS system. But how does GPS work? Why is it dependent on satellites? Let me try and answer these questions.

The invention of GPS is an interesting story. 60 years ago, Russia launched the first ever satellite Sputnik in space. For the USA, this came as something of a shock and surprise (some wonderful glimpses of theatmosphere are captured in the movie ‘October Sky’). People became concerned about their security.

But for two scientists in the Applied Physics Laboratory (APL) located in Maryland, Sputnik meant a novel opportunity. The two scientists were William Guier and George Weiffenbach.

Sputnik used to emit certain radio frequencies for communications. William and George started monitoring these frequencies. They realised that if they apply the Doppler Effect to these transmissions, they can find out the position of the satellite!

We all know the Doppler Effect of course. If a train blowing whistle is approaching you, the whistle appears shrill. But if the train is going away, the same whistle sounds softer. William and George applied this to the rotating satellite and were able to calculate its position. They reported this to their director, who gave them a pat on the back and funds to get better equipment for the experiments.

Next spring a new director Frank McClure joined and found out about the experiments. He called William and George to his room and asked them to close the door. Then he asked them – can they invert the experiment? Given the position of the satellite, can they find their own position? And thus was born the technology that is now called Global Positioning System (GPS).

So this is how it works. The satellite emits a known frequency that GPS instruments catch. Since the satellite position is known, some mathematical calculations using the Doppler Effect tell us where exactly we are. And that’s how the little blue dot on your Google maps moves.

The accuracy of the position depends on the number of satellites. For the GPS to work a minimum of three satellites are required. But most nations having a GPS system have many more. For example, the US and Russia have 24, Europe has 27 and China has as many as 35. With the seven satellite based NAVIC system, we will get enough accuracy for India and regions around us.

You can read the story of William and George in their own http://www.jhuapl.edu/techdigest/td/td1901/guier.pdf

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Gut feeling: bacteria in your gut might be affecting your mind

This is a frantic time for the stomach bug. The heat, lowered water levels and vacationing crowds bring a host of stomach infections with them. Many of you like me might have already suffered. After a few days of antibiotics and food restrictions we get better. We no longer give a thought to the bacteria in the gut, except with a sense of passing annoyance.

But these little guys in your stomach might be far more important than we think (or don’t think). If the hints scientists are getting turn out to be correct, gut bacteria (or microbiome, as they are called), might be having profound effect on the development of our brains and our mental well being.

In some interesting experiments on mice, researchers found clear links between microbiome and anxiety. They delivered some baby mice through caesarean procedure. Such mice had a different microbiome from the baby mice born though vaginal delivery, who acquired the vaginal bacteria of their mothers. The researchers found that the caesarean born mice had higher anxiety levels than the normally born mice. It’s too early to link this observation to human beings, but this just points out the kind of discoveries we might make.

Some studies are happening on human beings. After the 2000 flooding of many Canadian regions, more than 2000 people were affected by gastrointestinal problems, such as irritable bowl syndrome (IBS). Researchers studying the affected people found a clear correlation between psychological disorders such as depression and anxiety and IBS. Scientists are working on the question of whether the destruction of gut bacteria due to infection caused the mental disorders. Links of gut bacteria with disorders like autism have already been seen.

(See my 2013 article : http://www.yourssciencely.in/2013/12/gut-bacteria-and-autism.html)

The obvious question is: how can bacteria in stomach affect the brain? Microbes in blood cannot enter the brain cells due to what is called as the blood-brain barrier. Some microbes like the Rabies virus break this barrier and enter neurons, playing havoc with us such as making us afraid of water among other things.

But gut bacteria mostly do not take such drastic steps. They have other powerful weapons at their disposal. The waste products of many gut bacteria contain neurotransmitters, the chemicals that our brain cells use to talk to each other. An example is the neurotransmitter Serotonin. Scientists found that levels of Serotonin in blood change significantly when microbiome is changed. This might be affecting our brains.

Gut bacteria might also be have other complex effects on the development of baby brains. As an example, they might be affecting a process called Myelination, a kind of covering up of neurons. The chemicals produced by these bacteria might be triggering growth of neurons in particular places in the young brains.

Finding these links is important because then we can use them for treatment. An interesting research is going on at the McMuster University, Ontario in Canada. The Office of Naval Research has funded a research project to find a treatment that will help soldiers deal with stress better. The fighters have to face several high-stress situations in their work. It is possible that supplementing them with proper gut bacteria might improve their stress handling capability. I think we might all benefit from such a discovery!

Naturally, the pharmaceutical industry sees a big opportunity in this research. Since 2008, more than 500 million dollars have been spent in finding microbiome based treatment for mental disorders. We haven’t seen much success yet, but some good breakthroughs may be just round the corner. Of course, ‘Probiotic’ yogurt and probiotic supplement tablets are already here. But though harmless, they haven’t been found effective in anything.

This might change very soon as we understand the links between gut bacteria and brain (called the microbiome-gut-brain axis) better. I would love to report the progress as it is published.