As part of our celebration of the International Year of Astronomy 2009 we brought you the article How does gravity work?, in which Bangalore Sathyaprakash takes us from Newton's theory of gravitation to Einstein's general theory of relativity. Now hear Sathyaprakash explain gravity in his own words
in this podcast.
In our fourth online poll to find out what Plus readers would most like to know about the Universe you told us that you'd like to find out how gravity works. We took the question to Professor Bangalore Sathyaprakash of the School of Physics and Astronomy at
Cardiff University, and here is his answer. This interview is also available as a podcast.
If you'd like to put another Universe question to experts, vote in the current poll, or leave a comment on this blog.
Thanks for this interesting article - but I do find the paragraph below confusing. My first problem is the sentence: "But according to Newton's gravity, the effect of the Sun's vanishing would be felt immediately, as the Earth would fly away in an tangential direction to its original path." Does this vanishing refer to sight? If so, this has nothing to do with gravity.
"According to Newton's theory, gravitational interaction is instantaneous. Suppose the Sun were to vanish from the horizon today. We would not notice its disappearance immediately just by looking at the Sun, because light takes some time to travel. But according to Newton's gravity, the effect of the Sun's vanishing would be felt immediately, as the Earth would fly away in an tangential direction
to its original path." Einstein's special theory of relativity, however, states that nothing, not even information, can travel faster than the speed of light. "It's possible to use the vanishing Sun analogy to construct [theoretical] gravitational telegraphs which would transmit information instantaneously — and that, according to Einstein, is impossible. That's the reason why Einstein had to
reformulate the theory of gravity." Einstein published his reformulation in 1916, under the name of general relativity.
A researcher from the University of Bath has tackled an old geometric problem with a new method, which may lead to advances in creating hip replacements and replacement bone tissue for bone cancer patients. The Kelvin problem, posed by Lord Kelvin in 1887, is to find an arrangement of cells, or bubbles, of equal volume, so that the surface area of the walls between them is as small as possible
— in other words, to find the most efficient soap bubble foam. The problem is relevant to bone replacement materials because bone tissue has a honeycomb-like structure, similar to a bubble foam.
This year's Frieze Art Fair in London is going to tempt its arty audience with a little string theory. A project developed by David Berman, a physicist at Queen Mary, University of London, and the US artist Jordan Wolfson will invite visitors to view the show together with a string theorist, who will talk about his trade while touring the exhibition. The aim is to open up unconventional
perspectives on the art works on display.
Plus doesn't usually report on primary school maths, but we couldn't resist telling you about a beautiful new maths play for key stage 2 students, which premiered today at the Royal Institution. In the land of Polygonia, where maths is the official language, Rhombus the maths wizard is falsely imprisoned on the orders of
Queen Parabola. Data, a ten-year old girl, is the only witness. Before she can help him she must learn to speak the language of maths — and work out why the queen hates anyone who tries to make maths exciting.
Today's two performances, each in front of a full house, proved a great success with audiences made up of students from year 3 through to year 7 and their teachers. With their help, and plenty of laughs, Data managed to solve the puzzles facing her in her mission to save Rhombus, encountering prime numbers, number sequences, symmetry and more mathematical magic along the way. Data and the
audience learn that no matter how difficult a maths problem looks, there's usually a trick which makes it simpler, and more fun.
What would you like to know about your Universe — The fifth online poll
This poll is now closed. The most popular question was: "Is time travel allowed?" We will publish the answer in an article on Plus shortly. Thank you for taking part!
This is the fifth online poll in our series to celebrate the International Year of Astronomy 2009. Choose your favourite question from the list on the right, and we'll put the one that proves most popular to world-leading astronomers and cosmologists, including Astronomer Royal Martin Rees and author and cosmologist John D. Barrow. The poll will
remain open for a month and the answer will be published in a Plus article and podcast soon after. If your most burning question is not on this list, then leave a comment on this blog and we'll endeavour to include it in a future poll.
The winning questions in our previous polls have been
What is the nature of the universe and consciousness ?
How is the material constructed ?
That is the problem concerning to the humankind for a long time. And we always thought that the universe is created from the elementary particles, but perhaps we also always agree with Geoffrey Chew’s idea : “A truly elementary particle – completely devoid of internal structure – could not be subject to any forces that would allow us to detect its existence. The mere knowledge of a particle’s
existence, that is to say, implies that the particle possesses internal structure!” (1).
And it must be completely homogeneous, each its debris must be intact itself not different, it could not be subject to the space and time
With that particularities, the elementary particle could not exist in the our world, even though in the subatomic world.
So, why do we always thought that it must be a smallest particle?
Why can not it be an unlimited one, contains all motive laws of the universe?
And there is only the unlimited one that contains all the particularities of an elementary particle.
Therefore, universe is just one the unlimited and homogeneous entity, with an inherent internal energy in oscillations form, in which, the material is mere the sets of internal oscillations of that entity.
THE NATURE OF THE LIGHT http://sites.google.com/site/ngvnhg/
When talking about the theory of evolution and the age of the earth and it's inhabitants, no one ever wants to talk about the lose of speed in the spin of the earth. How many years back would the spin of the earth be so great that no person could remain on the surface because gravity could no longer hold them down and/or the wind sheer would be so great that the surface would begin to become
smooth? This would definitely have a lot to do with the age of mammals on this planet.