Gravitational potential and speed of light

Remnant of Supernova 1987A seen in light of very different wavelengths. ALMA data (in red) shows newly formed dust in the centre of the remnant. Hubble (in green) and Chandra (in blue) data show the expanding shock wave. Credit: ALMA/NASA

(Phys.org) —Physicist James Franson of the University of Maryland has captured the attention of the physics community by posting an article to the peer-reviewed New Journal of Physics in which he claims to have found evidence that suggests the speed of light as described by the theory of general relativity, is actually slower than has been thought.

Read more at: http://phys.org/news/2014-06-physicist-slower-thought.html#jCp

The paper is available in IOP website.

Length vs Speed

I don't know who made this graphic, but it's a great way to compare length vs speed and the Physics that can be applied.

Neutrino's Saga - final chapter?

Time of flight difference between the speed of light and the arriving neutrinos. Observe a great difference between the two experiments. Now, we have to wait for the new results of the OPERA experiment, after the cable's problem.

The ICARUS experiment uploaded a paper to the arXiv website with a preprint paper about the neutrinos' velocity, in October 2011, defying the superluminal neutrinos. Now, after the assumption of a problem in a cable, by the OPERA team, ICARUS published a preprint paper that confirms the previous results that neutrinos doesn't travel with a speed superior that the speed of light. 

So, we have to wait for the OPERA results (we need a large number of events and it takes... days), to confirm that neutrinos aren't superluminal.

Here is the abstract:

Measurement of the neutrino velocity with the ICARUS detector at the CNGS beam

The CERN-SPS accelerator has been briefly operated in a new, lower intensity neutrino mode with ~10^12 p.o.t. /pulse and with a beam structure made of four LHC-like extractions, each with a narrow width of ~3 ns, separated by 524 ns. This very tightly bunched beam structure represents a substantial progress with respect to the ordinary operation of the CNGS beam, since it allows a very accurate time-of-flight measurement of neutrinos from CERN to LNGS on an event-to-event basis. The ICARUS T600 detector has collected 7 beam-associated events, consistent with the CNGS delivered neutrino flux of 2.2 10^16 p.o.t. and in agreement with the well known characteristics of neutrino events in the LAr-TPC. The time of flight difference between the speed of light and the arriving neutrino LAr-TPC events has been analysed. The result is compatible with the simultaneous arrival of all events with equal speed, the one of light. This is in a striking difference with the reported result of OPERA [1] that claimed that high energy neutrinos from CERN should arrive at LNGS about 60 ns earlier than expected from luminal speed. 

 Read more in DiscoverMagazine.com, CNet and Wired. 

Measure the Speed of Light with Chocolate

"'C' is for chocolate! 'c' is also the symbol used for the speed of light. Defined as being 299,792,458 meters per second in vacuum, you can take a crack at measuring the ultimate speed using your microwave, a ruler and a bar of chocolate! Yum!" (Jefferson Lab - YouTube)

Well, lets see how they do it:

And now the calculations:

To calculate the speed of light, we can use the math's expression of speed:

v = Dx/Dt

In this case, Dx = l and Dt = T and T = 1/f (T is the period and f the frequency of the wave, and l the wavelength).
The holes that appear in the chocolate corresponds to the maximum and minimum in a steady wave. So the wavelength is two times this distance:
l = 2 x 7.1 cm = 2 x 7.1 x 10^-2 m
The frequency can be read in the back of your microwave. In this case, the value corresponds to f = 2 450 MHz = 2 450 x 10⁶ s^-1.


So, velocity is:
v = l x f <=> v= 2x(7.1 x 10^-2 m) x (2 450 x 10⁶ s^-1) = 3.48 x  10⁸ m s^-1 .


That brings a percent error:


e = |c - v|/|c| x 100 = | 2.99 x  10⁸ - 3.48 x  10⁸|/|2.99 x  10⁸| x 100 = 16 %

Breaking the speed of light?

Let's break the speed of light in your backyard :)

The Neutrino's Saga - Part 3

The OPERA experiment

Roll over Einstein: Law of physics challenged (Update 3)
One of the very pillars of physics and Einstein's theory of relativity - that nothing can go faster than the speed of light - was rocked Thursday by new findings from one of the world's foremost laboratories.
in PhysOrg.com

"[...] As a spokesperson for the MINOS neutrino experiment told Ars yesterday, there are three potential sources of error in the timing measurements: distance errors, time-of-flight errors, and errors in the timing of neutrino production. The vast majority of both the paper and the lecture were dedicated to discussing how these errors were reduced (the actual detection of the neutrinos was only a small portion of the paper).

[...] There are a lot of potential sources of error they know about—the paper’s table lists a dozen of them. Small errors in each of these could add up to something more significant than their total error. Then there are the classic unknown unknowns.

 in wired.com

More in the news Reuters, PhysicsAbout

Attention at FermiLab: http://beaconnews.suntimes.com/news/7807816-418/physics-turned-on-its-ear-catches-attention-at-fermilab.html

See the video of the presentation in a seminar: http://cdsweb.cern.ch/record/1384486/

Faster than the speed of light

Roll over Einstein: Pillar of physics challenged (Update)
A pillar of physics - that nothing can go faster than the speed of light - appears to be smashed by an oddball subatomic particle that has apparently made a giant end run around Albert Einstein's theories.

It seems that the muon neutrinos from CERN traveled 730 km and arrived the Gran Sasso Lab, Italy, a billionths of a second earlier than expected (it means it traveled that distance faster than the speed of light).