Universe Today

Ever wonder what it would be like to walk on the Moon or run on Mars? A treadmill developed using NASA technology can provide users the feeling of moving about in less than 1 G. Anti-gravity treadmills, sold under the name of Alter-G, are becoming common in hospitals, rehab centers, and sports facilities, and just about every professional sports team in North America has one. They are a bit pricey for individuals to afford, but athletes and physical therapists say the device is a fantastic addition to their exercise repertoire.
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If you can build a better mousetrap, then you can certainly build a better glove for astronauts! Making a glove that both protects the hands of the astronauts in the harsh environment of space or on the Moon, and allowing them the dexterity to manipulate tools is a tough challenge for NASA. That's why they are holding the second Astronaut Glove Challenge on November 19th, with a $400,000 prize for the best glove. Read more…

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When waves interact, specifically when they interfere, the effect is called, in physics, interference. Instruments which rely upon the interference of electromagnetic waves are called interferometers.

Some of the most sophisticated interferometers are to be found in astronomical observatories, because they can be used to reveal far more about stars, galaxies, planets etc than simple telescopes can.

Aperture synthesis is perhaps the most common form of astronomical interferometry. This involves a number (at least two!) of separate telescopes working together to act like a single telescope the size of the distance between them. Electromagnetic (EM) radiation – light, infrared, submillimeter radiation, microwaves, radio – received by each unit (telescope) is combined (it interferes), and information – often an image – about the source extracted. Sometimes this is done in real time – by piping the EM radiation to a device (the actual interferometer) near the center – and sometimes by recording the signal and combining it electronically later; the former is common in optical astronomy, the later in radio astronomy. An array of telescopes can be used – with different combinations giving different possible baselines – or the Earth's rotation may supply the changing viewing angle and distance needed to reconstruct an image ('synthesize the aperture'). In VLBI (very long baseline interferometry, an important part of radio astronomy), the most distant telescopes may be separated by tens or thousands of km (i.e. at least one is in space).

The first interferometer used in astronomy was in 1920, when Michelson and Pease used one to measure the diameter of Betelgeuse (Michelson was very familiar with interferometers, having built one – with Morley – that formed the heart of an experiment which showed that the aether does not exist; oh, and he also won the Nobel Prize for his work on interferometers). However it was in radio astronomy that interferometry really made its mark; in the radio part of the EM spectrum, the waves are so long that a single radio dish has a very low angular resolution (often much worse than that of the human eye), so to get images even close to those which optical astronomers get, even with atmospheric seeing, interferometry is essential.

The most sensitive interferometer used in astronomy today does not observe the universe through EM radiation, but looks for gravitational wave radiation. In LIGO, VIRGO, and other gravitational wave observatories interferometers constantly measure the distance between two masses suspended in vacuum chambers, several km apart. Changes in that distance may be caused by passing gravitational waves (not to be confused with gravity waves!); the changes will be tiny – some fraction of the size of a proton! – but detectable.

NASA's Ask an Astrophysicist has a good short article on interferometers; the ESO's VLTI (Very Large Telescope Interferometer) explained; CHARA (Center for High Angular Resolution Astronomy), ALMA (Atacama Large Millimeter/Submillimeter Array), and LIGO (Laser Interferometer Gravitational-wave Observatory) … just some of the hundreds of astronomical interferometers.

Universe Today stories which rely upon interferometers include A Glimpse at the Future of Our Sun, Squadrons of Planet Hunters Could Find Life, European Astronomers: 'Era of Stellar Imaging' Has Begun, and New Limits on Gravitational Waves From Big Bang.

Interferometry, an Astronomy Cast episode, explores this topic in more detail; and Gravitational Waves discusses how gravitational wave radiation may be detected by interferometers.

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Infrared spectroscopy is spectroscopy in the infrared (IR) region of the electromagnetic spectrum. It is a vital part of infrared astronomy, just as it is in visual, or optical, astronomy (and has been since lines were discovered in the spectrum of the Sun, in 1802, though it was a couple of decades before Fraunhofer began to study them systematically).

For the most part, the techniques used in IR spectroscopy, in astronomy, are the same or very similar to those used in the visual waveband; confusingly, then, IR spectroscopy is part of both infrared astronomy and optical astronomy! These techniques involve use of mirrors, lenses, dispersive media such as prisms or gratings, and 'quantum' detectors (silicon-based CCDs in the visual waveband, HgCdTe – or InSb or PbSe – arrays in IR); at the long-wavelength end – where the IR overlaps with the submillimeter or terahertz region – there are somewhat different techniques.

As infrared astronomy has a much longer ground-based history than a space-based one, the terms used relate to the windows in the Earth's atmosphere where lower absorption makes astronomy feasible … so there is the near-IR (NIR), from the end of the visual (~0.7 µm) to ~3 µm, the mid (to ~30 µm), and the far-IR (FIR, to 0.2 mm).

As with spectroscopy in the visual and UV wavebands, IR spectroscopy in astronomy involves detection of both absorption (mostly) and emission (rather less common) lines due to atomic transitions (the hydrogen Paschen, Brackett, Pfund, and Humphreys series are all in the IR, mostly NIR). However, lines and bands due to molecules are found in the spectra of nearly all objects, across the entire IR … and the reason why space-based observatories are needed to study water and carbon dioxide (to take just two examples) in astronomical objects. One of the most important class of molecules (of interest to astronomers) is PAHs – polycyclic aromatic hydrocarbons – whose transitions are most prominent in the mid-IR (see the Spitzer webpage Understanding Polycyclic Aromatic Hydrocarbons for more details).

Looking for more info on how astronomers do IR spectroscopy? Caltech has a brief introduction to IR spectroscopy. The ESO's Very Large Telescope (VLT) has several dedicated instruments, including VISIR (which is both an imager and spectrometer, working in the mid-IR); CIRPASS, a NIR integrated field unit spectrograph on Gemini; Spitzer's IRS (a mid-IR spectrograph); and LWS on the ESA's Infrared Space Observatory (a FIR spectrometer).

Universe Today stories related to IR spectroscopy include Infrared Sensor Could Be Useful on Earth Too, Search for Origins Programs Shortlisted, and Jovian Moon Was Probably Captured.

Infrared spectroscopy is covered in the Astronomy Cast episode Infrared Astronomy.

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"Twinkle, twinkle little star", how maddening! Adaptive optics (AO) to the rescue.

Down here, under a sea of air, stars dance around and flash with different colors when viewed at high magnification through a telescope. That's because the path of light rays through the air is not straight and not constant, due to the air being in motion and of uneven density; turbulence. Astronomers call this 'seeing'.

Seeing can be reduced by keeping the telescope and its equipment (and dome) at the same temperature as the air, by getting above as much of the atmosphere as possible (on mountaintops, for example), and by choosing sites where the air is unusually steady (on only some mountaintops).

Better still would be to find a way to cancel out the distortions introduced by the air, and to make the image that falls on a detector such as a camera as close to that you'd get if the telescope were above the atmosphere. That's what adaptive optics does.

In a nutshell, a number of wavefront sensors measure how distorted the light entering the telescope is (the wavefront), calculate how to warp ('deform') a bendy mirror in the light path so as to make it undistorted, and do so … hundreds or thousands of times a second. There are several different technologies for doing this, and the simplest can be found on some amateur telescopes (the 'tilt-tip mirror').

Adaptive optics became possible only with the advent of computers both cheap and fast enough to calculate the wavefront distortions in real time (the air is still on timeframes of milliseconds); the principles of AO were known several decades before they were implemented on astronomical telescopes in the 1990s. Today, just about every new large telescope comes with AO instruments, capability, or plans for such.

In general, AO only works over a relatively small field within the image plane of a telescope, and for it to be successful on faint objects, there needs to be a bright one nearby to serve as a guide. Initially, these were stars; today several observatories are equipped with lasers which can create an artificial 'star' a dozen or so km up in the atmosphere (they often operate in pulsed mode, in synch with the detector, to keep the artificial 'starlight' from spoiling the image of the faint astronomical source).

With AO, a large telescope can achieve a resolution close to its theoretical maximum, which can be as low as a few hundredths of an arcsecond (as good as, or better than, the Hubble Space Telescope!).

The University of California's Center for Adaptive Optics has a good set of material for further exploration of the technical aspects.

Universe Today has lots of stories on observations made using AO; for example, Adaptive Optics Reveal Massive Star Formation, Best Ground-Based Image of Jupiter – Ever!, Closest Ever Look at Betelgeuse Reveals its Fiery Secret, and Titan's Desert Sports a Surprising, Powerful Storm. Enhanced Vision for the Subaru Telescope, and Keck Uses Adaptive Optics for the First Time cover the AO techniques themselves.

Astronomy Cast has an episode on Adaptive Optics; The Rise of Supertelescopes explains how important AO has become, and Optical Astronomy gives the general background.

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Isaac Newton is arguably one of the most influential scientists in history. Though he lived in the late 1600s, many of his discoveries still affect us in the present. His various theories still hold true even centuries after his death and countless experiments. The scientists able to improve upon his work became famous themselves. Some would say that he was the greatest product of the Enlightenment, the explosion of intellectual knowledge that occurred in his century. So what did Isaac Newton discover?

Sir Isaac Newton’s largest contributions were in the areas of science and mathematics. Newton discovered many of the laws and theories that not only furthered our understanding of the universe, but also gave future scientists the tools to discover how to enter space. He discovered gravitational force and established the three Universal Laws of Motion. By tying these discoveries to the work Johannes Kepler and his Laws of Planetary motion, he established classic mechanics the beginning of modern Physics. This was huge in many ways as he proved definitively the heliocentric model first proposed by Copernicus. He also was the first to propose a set of laws that described the motion of all things in the universe. This served as the basis for our understanding how the universe functions and why it is the way it is. For his time and even now this was a major breakthrough.

His discoveries in mathematics were just as important. He came up with the Binomial Theorem and was one of the two creators of calculus. These discoveries represented a quantum leap in the fields of math and science allowing for calculations that more accurately modeled the behavior of the universe than ever before. Without these advances in math, scientists could not design vehicles to carry us and other machines into space and also plot the best and safest course. Calculus gave scientist the tools to set up a theoretical model of a situation and still account for varying factors. This basic knowledge would help scientist such as Einstein to be able make even greater discoveries such as the Theory of Relativity and Nuclear Fission.

In the end, when we look at Newton's discoveries we must realize that we are looking at one of the core foundations of the modern sciences. Newton opened humanity's eyes to new possibilities and even though his work is over three hundred years old it still helps to guide the advance of technology and our scientific understanding of the earth and the universe around us.

If you enjoyed this article there are others on Universe Today that you will enjoy. There is an interesting article on the Gravitational Constant. There is also a great article on "What is the Universe?"

There are other resources on the internet if you want to learn more about Isaac Newton. This UK site has some great info on his discoveries. You can also check out the PBS website.

You can also check out Astronomy Cast. Episode 44 Einstein's Theory of Relativity is particularly interesting.

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Walking on the moon was one of mankind's greatest technological feats and NASA's biggest success story. We all know about the very first successful landing and the two astronauts who first set foot on the moon, Buzz Aldrin and Neil Armstrong. But they were not the last astronauts to walk on the moon and go further than most humans have ever traveled. So, how many men have walked on the Moon?

Including the first two astronauts 12 men have walked on the moon. Looking at the development of the Apollo program it is not surprising. The entire Apollo program was a study in the gradual progression of technology until a successful moon landing and return. The first Apollo missions dealt with actually getting to the moon and coming back. Up until the Apollo 11 mission, no astronauts landed on the moon. They simply flew to it, did a flyby and returned. After the successful Apollo 11 mission of course the feat was repeated several times.

NASA launched 6 successful mission in all to the moon. The last was in 1972. There is very interesting information concerning these twelve astronauts. First off they are among only 24 people to actually see the far side of the moon. Second there were other famous astronauts other than Armstrong and Aldrin. Alan Shepard the commander of the Apollo 14 mission was the second man and first American in space. His mission was also the first to be broadcast in color television.

Apollo 17 was the last mission to the moon. The three astronauts on this mission were Eugene Cernan, Ronald Evans and Harrison Schmitt. Their mission was also the first night launch occurring at midnight. Cernan and Schmitt became the very last astronauts to walk on the moon.

Another question that would probably be raised is if the lunar landings were so successful why didn't NASA or other nations plan more missions? The simple answer is lack of resources. The Apollo program at its peak cost 24 billion dollars. Even now the current NASA budget is only half of that amount. On top of that, the United States was going through a major recession in the latter half of the seventies so NASA had a curtailed budget and limited political will to launch any more missions. The Soviet Union was the only other government capable of a similar feat but they had already decided against the expenditure. The eventual collapse of the Soviet Union put a permanent end to any possibility of an attempt by a foreign government at the time.

If you enjoyed this article there are others on Universe Today that you will like. There is a great article on the Space Race. There is also a great article on Russian Cosmonauts.

There are also great resources on the web. The NASA website has extensive information on the Apollo program. The Smithsonian website also has a page with detailed information on each of the missions.

You can also check out Astronomy Cast. Episode 114, The Moon, Part 2 is about the history lunar exploration.

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Although current astronauts are Twittering and blogging from space, it's a cumbersome process as the ISS, shuttle and Soyuz do not have internet access. Instead, they have to downlink their information to mission control, where someone posts it to the web. But if future commercial space travelers or astronauts living on the Moon want to blog, Tweet and share their experiences real-time, will it be possible? Well, a group of engineers are working on applying the same wireless systems that keep our mobile phones, laptops and other devices connected to the web to a new generation of networked space hardware. They say that wireless technologies will likely be important part of future space exploration, not only for human communication but for transfer of data and commands.
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