Ernst Mach

Today in Mailbox: We announce the four lucky winners of our September competition and you will also find out the new question for October. Listeners quoted: Sourabh Agrawal, Mukesh N Tekwani, Al Vybiral, David Eldridge, Charles Konecny, Charles Konecny, Radiant Didla, Catherine Kraina, David Wright, Petr Young, Stephen Price, Colin Law.

Hello and welcome to Mailbox. As promised, today we'll find out the name of our mystery person from the September competition and we'll announce the names of the four lucky listeners who will receive Radio Prague goodies for their correct answers. We asked you to tell us the name of a renowned physicist who was born in Brno in 1838. Let's hear some of your answers. This one is from Sourabh Agrawal from India.

"The correct answer is Ernst Mach and he is best known for an 1877 paper on supersonic velocity in which he gave his name to the ratio of an object's speed to the speed of sound (an object moving at the speed of sound is at Mach 1)."

Also from India Mukesh N Tekwani wrote:

"The physicist mentioned is none other than Ernst Mach. The quantity is the 'Mach number'."

Al Vybiral from the United States adds more on the Mach number:

"The answer to this month's Mailbox question is Ernst Mach. The Mach number is attributed to his research. It is a multiple of the speed of an object relative to the speed of sound."

David Eldridge from England sent us some practical implications:

"For example, the flow of atmosphere over the wing of an aircraft as it accelerates and approaches Mach 1 is less than Mach 1 at the leading and tailing edges of the wing, but greater than Mach 1 at the centre of the wing. As the aircraft increases speed, the airflow at the leading edge of the wing remains less than Mach 1 but both the middle and trailing edges of the wing then become greater than Mach 1. This configuration causes the shock wave known as the sonic boom."

This answer came from Charles Konecny from the United States:

"I am familiar with Mach speeds and Doppler effects as I was stationed at White Sands Proving Grounds while in the Army during the Korean War. White Sands is a missile development facility and my duties were at a Doppler radio site. It is with great satisfaction that Mach speed is named for a Czech."

Radiant Didla listens to us in Lithuania:

"I am glad I got a chance to participate again in this month's quiz. The famous physicist who was born in Czech Republic's second largest city is Ernst Mach. And "Mach Bands" are an optical illusion named after Ernst Mach."

Catherine Kraina follows Radio Prague in Australia:

"Ernst Mach is your man. Born in Chrlice, Brno, in 1838, Mach was a mathematician, physicist and philosopher. Mach numbers, representing the ratio of the speed of a moving body to the speed of sound (Mach 1), are named after him. He was a bit of a polymath, working in fields including acoustics, optics and sensory perception. Einstein saw him as an important forerunner in development of the theory of relativity, and he must have been an OK chap because Lenin denounced "Machists" who shared his philosophy of science."

David Wright from South Wales also mentions Einstein in connection to Ernst Mach:

"His work was very influential to Albert Einstein who took the idea of relativity further. Ernst Mach was one of the great thinkers of his time and like fellow thinkers Mendeleyev and Darwin he had the beard to go with it!"

Petr Young from the United Kindgom summed his answer up in a poem:

"Born in Brno,

Prof Ernst Mach,

Put us on track,

In subsonic,


Go, go, go,

With the flow."

Stephen Price sent this answer from North Carolina:

"The answer is Ernst Mach, he was born in Chrlice which is now part of Brno. Later he taught at Charles University in Prague. The Ford motor company used his last name for the name plate for the high performance versions of the Mustang which is still being made today."

That's interesting to hear and I'm actually surprised that no one has mentioned the razor blades named after Mach. I would have thought the ubiquitous advertisements would have made them the first thing that comes to mind.

And finally, Colin Law from New Zealand:

"The world-famous physicist was Ernst Mach, 1838 - 1916. He was born in Moravia in the town of Chrlice. On today's maps Chrlice seems to have been absorbed as a suburb of Brno. He is frequently listed as an "Austrian" because at the time Moravia was part of the Austro-Hungarian Empire."

Thank you for all those answers which were in their overwhelming majority correct and there was still a little more of them than the last record earlier this year. And that's why we have quadrupled the number of winners and this time, the lucky four are:

Al Vybiral from the US, Bjorn Tandberg from Norway, Catherine Kraina from Australia and Mukesh Tekwani from India. Congratulations and your prizes are on their way!

And finally it's time to announce a new competition question. Our October quiz question is short and simple:

Which US Secretary of State was born in Prague?

You can send us your answers by the end of the month to [email protected] or Radio Prague, 12099, Prague, Czech Republic.