High-Speed Video Helps Scientists Understand Hummingbird Pollination

November 25, 2012

Science

Photo by Scott Streit

Hummingbirds are part of the family Trochilidae and are among the smallest birds on the planet, with most species measuring between 7.5 to 13 cm. Now, a new high-speed video has helped scientists understand why hummingbirds always pollinate flowers that hang upside down.

The scientists published their findings in the journal Functional Ecology. Hummingbirds are native to the Americas, and are one of the only types of birds that can hover while flying. This expends a lot of energy, and as such, they have one of the fastest metabolisms of any animal. While they eat small insects, hummingbirds typically drink the sugar-rich nectar from flowers to gain calories. Many hummingbird species have co-evolved with certain plant species, but it has remained a mystery why they visit flowers that hang upside-down.

In this experiment, biologists fed Anna’s hummingbirds (Calypte anna) from artificial flowers that pointed horizontally, upside-down, or tilted at a 45-degree angle. The flowers were filled with nectar and fitted with a mask to measure how much oxygen the birds were using while hovering. The upside-down flowers required the hummingbirds to tilt their heads back awkwardly, and required 10% more energy to feed than horizontal flowers.

Because it’s more costly energy-wise to drink from such flowers, researchers speculate that the orientation must be beneficial in some other way. They believe that flowers that don’t hang upside-down are possibly more exposed to rain, which would dilute the nectar, and since hummingbirds can taste the sweetness of the nectar, they may avoid flowers that contain less sugar.

Body posture of an Anna’s Hummingbird when feeding from horizontal (a), tilted (b), and vertical (c) feeders. Credit: Copyright Nir Sapir

Slowing Cargo Ships Results in Major Reductions in Pollution

November 23, 2012

Science

Cargo ship on the ocean. Photo via Environ. Sci. Technol., 2012, 46 (22), pp 12600–12607

A new study indicates that slowing down vessels near coastlines by 10 to 15 miles per hour can dramatically reduce air pollution from the ships. However, only a few US ports have initiated efforts to apply this.

The scientists published their findings in the journal Environmental Science and Technology. A speed limit of 14 mph, down from the current speeds of 25 to 29 mph would cut nitrogen oxides by 55% and soot by 70%. It would also reduce carbon dioxide by 60%.

Cargo ship in Vancouver’s harbor. Photo by Flickr/ecstaticist

There are 100,000 ships carrying 90% of the world’s cargo, and the resulting air pollution is problematic for people living near ports. The ports of Los Angeles/Long Beach and New York/New Jersey are already part of a voluntary monitoring program and this has already cut down emissions significantly in those areas. They’ve been in place for a number of years. Setting a speed limit is an elusive goal for port cities because shipping traffic is regulated by international treaties.

All vessels, when they are within 10 nautical miles of a US port, must slow down to 14 mph. Ports that are part of the volunteer programs slow ships out further out, up to 40 miles offshore.

A ship’s fuel consumption and emissions increase drastically when they go faster. In order to increase air quality, speed reductions would need to be maintained long-term. The shipping industry is responsible for 3% of the world’s carbon dioxide emissions and shipping emissions are expected to grow 2 to 3 percent every year over the next three decades [PDF] as shipping traffic grows, according to the International Maritime Organization.

Some states, like California, have banned ships from burning dirty kinds of fuel and are rolling out other clean port initiatives. As a result, smog-causing nitrogen oxides from the Los Angeles port have declined 30% between 2005 and 2011, while particulate matter has decreased about 70%.

Experiment Using Photons Could Detect Quantum-Scale Black Holes

November 23, 2012

Science

Jacob Bekenstein’s proposed experiment fires a photon through a transparent block to check whether space-time is pixelated. Image by J. Bekenstein

A new tabletop experiment using a single photon was proposed to show whether space-time is made up of indivisible units. Space isn’t smooth, and physicists think that on the quantum scale, it is composed of indivisible subunits, like the dots of a pointillist drawing. This pixelated landscape is thought to be populated by black holes, smaller than one trillionth of one trillionth of the diameter of a hydrogen atom, which continuously pop in and out of existence.

The pre-print of this study is available through arXiv. This hypothesis was proposed decades ago in order to unify quantum theory with Einstein’s theory of gravity, which is the only one of nature’s four fundamental forces not to have been incorporated into the Standard Model of Particle Physics.

Physicists have tried to use the Large Hadron Collider, gravitational wave detectors and observations of distant cosmic explosions in order to determine whether space is grainy, but so far the results have proven to be inconclusive.

This new tabletop experiment was proposed by Jacob Bekenstein, a theoretical physicist at the Hebrew University of Jerusalem, and it uses readily available equipment.

The experiment was designed to examine on the scale of 1.6 × 10⁻³⁵ (1.6E-35) meters. This Planck length is the theoretical limit at which the macroscopic concept of distance ceases to have any meaning and quantum fluctuations begin to make space-time resemble a foamy sea.

Instead of using instruments, Bekentstein proposes to fire a single photon through a transparent block, and indirectly measure the minuscule distance that the block moves as a result of the photon’s imparted momentum.

The photon’s wavelength and the mass as well as the size of the block are carefully chosen so that the momentum is just large enough to move the block’s center of mass by one Planck length. If space-time is grainy on this scale, then the photon is less likely to make it through the block. If quantum fluctuations in length are important on Planck scale, a sea of black holes, each with a Planck-scale radius, will readily form. Anything that falls inside of these black holes will be unable to escape until the hole dissipates. If the center of mass of the moving block falls into one of these holes, the block’s movement will be impeded. Photons are much larger than the Planck length, and as such aren’t bothered by these quantum black holes.

The conservation of momentum in this experiment requires that the photon can’t make it through the block if it fails to move by a Planck length. So if fewer photons than expected are seen by the detector, this would mean that the block’s movement has been impeded by black holes, and that space-time exhibits quantum features at the Planck scale.

Distinguishing between possible quantum gravitational effects from others will be challenging, states Igor Pikovski, a quantum physicist at the Vienna Center for Quantum Science and Technology. It is unknown at what exact scale quantum gravity plays a significant role. There is plenty of room for granularity at much larger lengths, but there is no theory that could provide this answer, he continues.

British and American Teams Hunt for Life Under Antarctic Ice

November 22, 2012

Science

A British field camp in Antarctica will soon host efforts to drill through the ice to reach Lake Ellsworth. Photo by BAS

Next week, UK glaciologists are heading to Lake Ellsworth to prepare for a new drilling stage that will start December 5. They hope to reach the lake and start examining sediments to find signs of life.

The team will try to understand the history of the West Antarctic Ice Sheet, which has the potential to reveal how the glacier has waxed and waned over time.

Roughly 380 subglacial lakes have been discovered and mapped in Antarctica, and they have been explored remotely with ice-penetrating radar, gravity measurements, and seismic sensors. The lakes were created by geothermal heat that melts the Antarctic ice from below. Gravity and pressure force the melt water to flow, and it collects under the ice.

Trapped under ice, infographic via Nature

If everything goes according to plan, Lake Ellsworth will be the second lake to be breached after Lake Vostok was reached in February. A US team is heading to Lake Whillans, a small, shallow body of water close to the edge of the Ross Ice Shelf. The discovery of exotic microbial life, which could have evolved untouched for millennia, is one of the aspects of this research. Scientists have already discovered bacteria that mine their energy from rocks and minerals, and they assume that there are many specialized microbes living underneath Antarctica.

The Russian team at Lake Vostok found evidence of heat-loving bacteria living in the bedrock surrounding the lake. The clues came from DNA in the sediment that was trapped in accretion ice. The upper layers of the lake itself appeared to be lifeless. No native microbes were turned up from a preliminary analysis of lake water.

Lake Ellsworth might have more microbes because it offers fewer hiding places. It’s 12 km in length, 3 km in width, with an average depth of about 150 meters. Vostok is 250 km long by 40 km in width, which makes it one of Earth’s largest freshwater bodies. It’s also nestled in a subglacial valley near the continental divide, where overlying ice moves at its slowest. The site, at about −30 °C, is twice as warm as the ice on the Vostok plateau in East Antarctica.

The goal is to reach Ellsworth in three days using a drill that will melt the ice with a high-pressure jet of water, heated up to 90 °C. Once the borehole is completed, the team has about 24 hours to deploy a sediment corer before the hole freezes over.

The equipment was prepared so that it doesn’t contaminate the lake with microbes from the surface. The main challenge involves completing all of the sampling operations within this very short window of time.