Gravity

Gravity Defying Drips of a Bike Pump Controlled Fountain

People love to see a trick that fools their senses. This truism was in play at the Crash Space booth this weekend as [Steve Goldstein] and [Kevin Jordan] showed off a drip fountain controlled by a bike pump.

These optical illusion drip fountains use strobing light to seemingly freeze dripping water in mid-air. We’ve seen this before several times (the work of Hackaday alum [Mathieu Stephan] comes to mind) but never with a user input quite as delightful as a bike pump. It’s connected to an air pressure sensor that is monitored by the Arduino that strobes the lights. As someone works the pump, the falling droplets appear to slow, stop, and then begin flowing against gravity.

Sadly this phenomenon is quite difficult to record in a video since the latency of our vision is integral for the trick to work. The frame…

Key Einstein principle survives quantum test

warping space
EINSTEIN ENDURES According to Einstein’s general theory of relativity, massive objects warp space (illustrated above), producing gravitational attraction. Scientists don’t understand how general relativity interfaces with quantum mechanics, but a pillar of general relativity, the equivalence principle, has withstood a new quantum test.

Particles with mind-bending quantum properties still follow a standard gravitational rule, at least as far as scientists can tell.

The equivalence principle — one of the central tenets of Einstein’s theory of gravity — survived a quantum test, scientists report online April 7 at arXiv.org.

In Einstein’s gravity theory — the general theory of relativity — gravity and acceleration are two sides of the same coin. According to the equivalence principle, the gravitational mass of an object, which determines the strength of gravity’s pull, is the same as its inertial mass, which determines how much an object accelerates when given a push (SN: 10/17/15, p. 16). As a result, two objects dropped on Earth’s surface should accelerate at the same rate (neglecting air resistance), even if they have different masses or are made of different materials.

One of the first reported tests of the equivalence principle — well before it was understood in the framework of general relativity — was Galileo’s apocryphal experiment in which he is said to have dropped weights from the Leaning Tower of Pisa. Scientists have since adapted that test to smaller scales, swapping out the weights for atoms. In the new study, physicists went a step further, putting atoms into…

Discovery of Speeding Galaxies May Challenge Einstein’s Gravity and Dark Matter

Article Image

A present-day near-miss of two spiral galaxies NGC 5426 and NGC 5427, which is possibly comparable to the early flyby of the Andromeda Galaxy past our own Milky Way. Courtesy of © Gemini Image Gallery.

A discovery of fast-moving galaxies, 10 million light years wide, may cause physicists to re-examine Einstein’s theory of relativity. A team from University of St. Andrews in Scotland found the enormous ring of galaxies speeding away from our galaxy much faster than existing physics modeling predicts. In fact, the scientists believe the galaxies are moving so quickly that they are calling this expansion “a mini Big Bang”.

Dr. Hongsheng Zhao and PhD student Indranil Banik co-authored the study, which came from investigating 54 galaxies in what’s called “the Local Group” of the Universe. The scientists explain the unexpected conclusions by proposing that at some point 7 to 11 billion years ago the neighboring Andromeda Galaxy came so close to our own Milky Way Galaxy that they created a “tsunami-like wake,” scattering smaller galaxies with a sling-shot-like effect.

“If Einstein’s Gravity were correct, our Galaxy would never come close enough to Andromeda to scatter anything that fast,”