The speed of light is constant, or so textbooks say. But some scientists are exploring the possibility that this cosmic speed limit changes, a consequence of the nature of the vacuum of space.
The definition of the speed of light has some broader implications for fields such as cosmology and astronomy, which assume a stable velocity for light over time. For instance, the speed of light comes up when measuring the fine structure constant (alpha), which defines the strength of the electromagnetic force. And a varying light speed would change the strengths of molecular bonds and the density of nuclear matter itself.
A non-constant speed of light could mean that estimates of the size of the universe might be off. (Unfortunately, it won't necessarily mean we can travel faster than light, because the effects of physics theories such as relativity are a consequence of light's velocity). [10 Implications of Faster-Than-Light Travel]
Two papers, published in the European Physics Journal D in March, attempt to derive the speed of light from the quantum properties of space itself. Both propose somewhat different mechanisms, but the idea is that the speed of light might change as one alters assumptions about how elementary particles interact with radiation. Both treat space as something that isn't empty, but a great big soup of virtual particles that wink in and out of existence in tiny fractions of a second.
Cosmic vacuum and light speed
The first, by lead author Marcel Urban of the Université du Paris-Sud, looks at the cosmic vacuum, which is often assumed to be empty space. The laws of quantum physics, which govern subatomic particles and all things very small, say that the vacuum of space is actually full of fundamental particles like quarks, called "virtual" particles. These matter particles, which are always paired up with their appropriate antiparticle counterpart, pop into existence and almost immediately collide. When matter and antimatter particles touch, they annihilate each other.
Photons of light, as they fly through space, are captured and re-emitted by these virtual particles. Urban and his colleagues propose that the energies of these particles — specifically the amount of charge they carry — affect the speed of light. Since the amount of energy a particle will have at the time a photon hits it will be essentially random, the effect on how fast photons move should vary too.
As such, the amount of time the light takes to cross a given distance should vary as the square root of that distance, though the effect would be very tiny — on the order of 0.05 femtoseconds for every square meter of vacuum. A femtosecond is a millionth of a billionth of a second. (The speed of light has been measured over the last century to high precision, on the order of parts per billion, so it is pretty clear that the effect has to be small.)
To find this tiny fluctuation, the researchers say, one could measure how light disperses at long distances. Some astronomical phenomena, such as gamma-ray bursts, produce pulses of radiation from far enough away that the fluctuations could be detected. The authors also propose using lasers bounced between mirrors placed about 100 yards apart, with a light beam bouncing between them multiple times, to seek those small changes.
Read the entire article:
Step right up and prove why you should get a one-way ticket to Mars! Well, wait -- you might want to know a little more about the venture first.
A Dutch company called Mars One began looking Monday for volunteer astronauts to fly to Mars. Departure for the Red Planet is scheduled for 2022, landing seven months later in 2023.
The space travelers will return ... never. They will finish out their lives on Mars, representatives from the nonprofit said.
"It's likely that there will be a crematorium," said CEO Bas Lansdorp. "It's up to the people on Mars to decide what to do with their dead."
Still, the company said it has received more than 10,000 e-mails from interested would-be spacefarers.
Read the entire article here:
NASA's Hubble Space Telescope has snapped a spectacular new image of an iconic nebula to celebrate its 23 years of peering deep into the heavens.
The Hubble observatory, which launched on April 24, 1990, captured the Horsehead Nebula in infrared light, peering through obscuring veils of dust to reveal the object's hidden features.
"The result is a rather ethereal and fragile-looking structure, made of delicate folds of gas -- very different to the nebula's appearance in visible light," mission officials wrote in an image description today (April 19). The new observations allowed astronomers to create a dazzling video of the Horsehead Nebula based on Hubble's photos.
The Horsehead Nebula, also known as Barnard 33, is located about 1,500 light-years from Earth in the constellation Orion (The Hunter). The Horsehead is a huge interstellar cloud of gas and dust, like other nebulae, and the light from a nearby star gives it a beautiful glow.
The object is a popular observing target, and Hubble has taken numerous Horsehead photos over the years -- including in 2001, to celebrate the telescope's 11-year anniversary.
The Horsehead's dramatic pillar is made of sterner stuff than the clouds surrouding the nebula, which have already dissipated. But the pillar will disintegrate as well in another 5 million years or so, astronomers say, and the Horsehead will go the way of the dodo.
Mars was capable of supporting microbial life in the distant past, scientists announced today.
They reached this conclusion after studying the latest observations from NASA's Curiosity rover, which just analyzed the first-ever sample collected from the interior of a Red Planet rock.
Here are answers to a few basic questions about Curiosity's discovery, and what it means about the Red Planet's past and the rover's future.
What exactly did Curiosity find?
Last month, Curiosity drilled 2.5 inches (6.4 centimeters) into a rock on a Martian outcrop that mission scientists have dubbed "John Klein." [The Search for Life on Mars (Photo Timeline)]
The rover's onboard Chemistry & Mineralogy (CheMin) and Sample Analysis at Mars (SAM) instruments found some of the chemical ingredients for life in the collected powder, including sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon. The mix of compounds also suggests that the area may have contained chemical energy sources for potential Red Planet microbes, researchers said.
In addition, the sample contains clay minerals, indicating that the rock was exposed to a benign aqueous environment — such as a neutral-pH lake, for example — billions of years ago.
To be clear, Curiosity found no evidence that life has ever existed on the Red Planet. But its results suggest that the John Klein site could have supported microbes long ago, if they ever evolved on Mars or were transported there.
So what? Didn't we already know that ancient Mars was wet?
Scientists have known for years that water flowed or pooled on the surface of Mars in the ancient past. But there's more to habitability than the mere existence of liquid water.
For primitive microbial life to survive, a site must also have the right chemical makeup and a potential energy source, researchers say. And all of these ingredients were apparently present at John Klein.
Doesn't the right chemical makeup include organic compounds? Did Curiosity find any of those?
The SAM instrument can detect complex organics — the carbon-containing building blocks of life as we know it — and Curiosity is looking for these molecules on Mars, but it hasn't found anything conclusive yet.
Read the entire article: