After making a successful landing on 67P/C-G, the Philae probe gathered as much data as it could before entering “sleep mode.” It’s not clear at this point whether it will revive again. While the ESA team had hoped Philae would have remained active longer, the lander did complete all of its major data gathering, so we can call this a win. The reason Philae went into sleep mode is that it happened to land in the shadow of a cliff, which meant it wasn’t getting enough exposure to sunlight to keep its batteries charged. Like many spacecraft, Philae is solar powered. It needs light to keep going.
Weft and Warp
Gravitational lensing is a well-known effect where the mass of an object such as a galaxy deflects the light from more distant objects. It was first observed by Arthur Eddington in 1916, and affects the observed position stars. With distant quasars it can produce an effect known as an Einstein cross. Even dark matter can gravitationally lens distant objects, which is one of the ways we know of its existence. But where gravitational lensing would be the strongest is in the vicinity of a black hole.
Echoes of Light
The supermassive black hole in the center of our galaxy, known as Sagittarius A*, is pretty quiet for a black hole. It does however flare up from time to time, when material is captured, as can be seen in images from the NuSTAR x-ray telescope. Of course, x-ray astronomy with enough sensitivity to observe x-ray flares at galactic center is …
Confluence of Evidence
Suppose you were an electrician. You’ve trained, apprenticed, passed all your certifications, and you’ve worked with electric wiring for years. You’ve wired houses and commercial buildings for years, and you feel pretty confident in your trade. One day you finish wiring a light switch, dust off your hands, and flip the switch to test it. But instead of seeing the light turn right on, you find that it flickers dimly. You’re pretty sure you wired things correctly, so what do you do?
Bend It Like Newton
Yesterday’s post on testing the assumption that photons are massless raised a few questions for readers. One of the most common was the idea that the gravitational lensing of light must mean that photons have mass. After all, if a star or galaxy can deflect light gravitationally, doesn’t that mean the light is gravitationally attracted to it? If that is the case, doesn’t that mean that light has mass?
Dying Light
Photons are massless. We know they are massless because particles with mass can’t move at the speed of light. We know that special relativity works, and the speed of light is the same in all frames of reference, and special relativity only works if photons are massless. Except…
Missing Ingredient
There’s been a bit of press regarding “missing light” in the universe. It all starts with a recent paper in the Astrophysical Journal Letters. Most of the popular articles spin things as missing light because that was the spin of the press release, but the actual work is more subtle, and more interesting.
Extraordinary Claims
A paper has recently been published in the New Journal of Physics claiming that the speed of light is wrong. This has triggered the usual headlines in the popular press, but as the saying goes, “extraordinary claims require extraordinary evidence.” So let’s look at the evidence behind this paper.
Light Me Up
One of the properties of atoms and molecules is that they interact with light in an interesting way. If you heat up atoms or molecules in a gas, they will give off light. But they only give off light at specific wavelengths (colors).