How Would We Do Surgery in Space?

Virtually rendered cutaway view of a postulated traumapod surgical module. Multiple layers of thermal and radiation shielding are visible. A four?armed surgical robot is situated within the module. The patient is tethered to the operating table, while the assistant, using a touchscreen console, is tethered to the module structure via a movable chair. Illustration by T. Trapp (https://www.planvis.co.uk) CC BY-SA 4.0

Any mission to Mars requires deeper planning than missions to the ISS or the Moon. Based purely on the length of the mission, contingencies branch outwards in complex logistical pathways. What if there’s an accident? What if someone’s appendix bursts?

And what if surgery is needed?

Continue reading “How Would We Do Surgery in Space?”

Russian-American Trio Blasts Off and Boards International Space Station After Fast Track Trajectory

The Soyuz MS-06 rocket blasts off with the Expedition 53-54 crew towards the International Space Station from the Baikonur Cosmodrome in Kazakhstan, Tuesday, Sept. 12, 2017 (Wednesday, Sept. 13, Kazakh time). Credit: NASA/Bill Ingalls

The Soyuz MS-06 rocket blasts off with the Expedition 53-54 crew towards the International Space Station from the Baikonur Cosmodrome in Kazakhstan, Tuesday, Sept. 12, 2017 (Wednesday, Sept. 13, Kazakh time). Credit: NASA/Bill Ingalls

Barely a week and a half after the thrilling conclusion to the record breaking space endurance mission by NASA astronaut Peggy Whitson, a new Russian-American trio blasted off for the International Space Station (ISS) on a Russian Soyuz capsule and boarded safely early this morning Wednesday, Sept. 13, after arriving as planned on a fast track orbital trajectory.

NASA astronauts Mark Vande Hei, Joe Acaba and Alexander Misurkin of Roscosmos launched aboard the Soyuz MS-06 spacecraft from the Baikonur Cosmodrome in Kazakhstan overnight at 5:17 p.m. Tuesday, Sept. 12, 2017, (2127 GMT), or 3:17 a.m. Baikonur time Wednesday, Sept. 13, on the Expedition 53 mission.

Following the flawless launch and achieving orbit the three man crew executed a perfect four orbit, six hour rendezvous and arrived at the orbiting laboratory complex at 10:55 p.m. EDT Tuesday, Sept. 12, (or Wednesday, Sept. 13, Kazakh time) where they will carry out a jam packed schedule of scientific research in a wide array of fields.

The entire launch sequence aboard the Soyuz rocket performed flawlessly and delivered the Soyuz capsule to its targeted preliminary orbit eight minutes and 45 seconds after liftoff followed by the opening of the vehicles pair of life giving solar arrays and communications antennas.

The whole event from launch to docking was broadcast live on NASA TV.

Soyuz reached the ISS after a rapid series of orbit raising maneuvers over four orbits and six hours to successfully complete all the rendezvous and docking procedures to attach to the station at the Russian Poisk module.

“Contact! We have mechanical contact,” radioed Misurkin.

The Soyuz MS-06 spacecraft carrying NASA astronauts Mark Vande Hei and Joe Acaba and cosmonaut Alexander Misurkin of Roscosmos is seen on the right approaching the International Space Station on Tuesday, Sept. 12, 2017. The spacecraft docked to the station at 10:55 p.m. EDT. Credits: NASA Television

After conducting leak and safety checks the new trio opened the hatches between the Soyuz spacecraft and station at 1:08 a.m. EDT this morning, Sept. 13 and floated into the million pound orbiting outpost.

The arrival of Vande Hei, Acaba and Misurkin restores the station’s multinational habitation to a full complement of six astronaut and cosmonaut crewmembers.

They join Expedition 53 Commander Randy Bresnik of NASA and Flight Engineers Sergey Ryazanskiy of Roscosmos and Paolo Nespoli of ESA (European Space Agency).

The station had been temporarily reduced to a staff of three for 10 days following the departure of the Expedition 52 crew including record setting Whitson, NASA astronaut Jack Fischer and veteran cosmonaut Fyodor Yurchikhin of Roscosmos.

This is the rookie flight for Vande Hei, the second for Misurkin and the third for Acaba. They will remain aboard the station for a planned five month long ISS expedition continuing into early 2018.

Vande Hei was selected as an astronaut in 2009. Misurkin previously flew to the station on the Expedition 35/36 increments in 2013. Acaba was selected as an astronaut in 2004. He flew on space shuttle mission STS 119 and conducted two spacewalks – as well as on the Expedition 31/32 increments in 2012 and has logged a total of 138 days in space.

Originally the Soyuz MS-06 was only to fly with a two person crew – Vande Hei and Misurkin after the Russians decided to reduce their cosmonaut crew from three to two to save money.

Acaba was added to the crew only in March of this year when NASA and Roscosmos brokered an agreement to fill the empty seat with a NASA astronaut, under an arrangement worked out for 5 astronauts seats on Soyuz through a procurement by Boeing, as compensation for an unrelated matter.

The Russian cosmonaut crew cutback enabled Whitson’s mission extension by three months and also proved to be a boon for NASA and science research. It enabled the US/partner USOS crew complement to be enlarged from three to four full time astronauts much earlier than expected.

This allowed NASA to about double the weekly time devoted to research aboard station – a feat not expected to happen until America’s commercial crew vehicles, namely Boeing Starliner and SpaceX Crew Dragon – finally begin inaugural launches next year from the Kennedy Space Center in mid-2018.

With Acaba and Vande Hei now on orbit joining Bresnik and Nespoli, the USOS crew stands at four and will continue.

The six crewmembers will carry out research supporting more than 250 experiments in astrophysics, biology, biotechnology, physical science and Earth science.

“During Expedition 53, researchers will study the cosmic ray particles, demonstrate the benefits of manufacturing fiber optic filaments in microgravity, investigate targeted therapies to improve muscle atrophy and explore the abilities of a new drug to accelerate bone repair,” says NASA.

Among the key investigations involves research on cosmic ray particles reaching Earth using ISS-CREAM, examining effects on the musculoskeletal system and exploring targeted therapies for slowing or reversal of muscle atrophy with Rodent Research 6 (RR-6), demonstrating the benefits of manufacturing fiber optic filaments in a microgravity environment with the Optical Fiber Production in Microgravity (Made in Space Fiber Optics) hardware, and working on drugs and materials for accelerating bone repair with the Synthetic Bone experiment to develop more effective treatments for patients with osteoporosis.

Expedition 53 Flight Engineers Mark Vande Hei and Joe Acaba of NASA and Soyuz Commander Alexander Misurkin of Roscosmos launched from the Baikonur Cosmodrome in Kazakhstan, Tuesday, Sept. 12, 2017 (Wednesday, Sept. 13, Kazakh time), and arrived at the International Space Station at 10:55 p.m. to begin their 5.5-month mission aboard the station. Credits: NASA/Bill Ingalls

Bresnik, Ryazanskiy and Nespoli are scheduled to remain aboard the station until December. Whereas Vande Hei, Acaba and Misurkin are slated to return in February 2018.

Watch this cool Roscosmos video showing rollout of the Soyuz rocket to the Baikonur launch pad and erection in advance of launch. Credit: Roscosmos

Meanwhile one of the first tasks of the new trio will be to assist with the departure of the SpaceX Dragon CRS-12 spacecraft upcoming this Sunday, Sept 17.

Dragon will be detached from the Harmony module using the stations Canadian-built robotic arm on Sunday and released for a splashdown and retrieval in the Pacific Ocean Sunday morning. It is carrying some hardware items as well as scores of science samples.

SpaceX launched its 12th resupply mission to the International Space Station from NASA’s Kennedy Space Center in Florida at 12:31 p.m. EDT on Monday, Aug. 14, 2017. Credit: Ken Kremer/Kenkremer.com

NASA TV will cover the release activities beginning Sunday at 4:30 a.m. EDT.

Visiting vehicle configuration at the International Space Station (ISS) after arrival of the Soyuz MS-06 spacecraft on Sept. 12, 2017. Credit: NASA

Watch for Ken’s onsite space mission reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

The space station’s Expedition 53 crew members are (from left) Joe Acaba, Alexander Misurkin, Mark Vande Hei, Sergey Ryazanskiy, Commander Randy Bresnik and Paolo Nespoli. Credit: NASA

Expedition 53 Crew Insignia

Year in Space Flight for Russian/American Crew Starts With Spectacular Night Launch and Station Docking

The Soyuz TMA-16M spacecraft is seen as it launches to the International Space Station with Expedition 43's NASA Astronaut Scott Kelly and Russian cosmonauts Mikhail Kornienko and Gennady Padalka of the Russian Federal Space Agency (Roscosmos) onboard Friday, March 27 (Saturday, March 28 Kazakh time) from the Baikonur Cosmodrome in Kazakhstan. Credit: NASA/Bill Ingalls

The first ever ‘One-Year Mission’ to the International Space Station (ISS) started with a bang today, March 27, with the spectacular night time launch of the Russian/American crew from the Baikonur Cosmodrome in Kazakhstan at 3:42 p.m. EDT Friday (1:42 a.m., March 28 in Baikonur and culminated with a flawless docking this evening.

NASA astronaut Scott Kelly and Russian cosmonauts Mikhail Kornienko and Gennady Padalka launched aboard a Soyuz TMA-16M spacecraft to the International Space Station precisely on time today on the Expedition 43 mission.

The crew rocketed to orbit from the same pad as Russia’s Yuri Gagarin, the first human in space.

Kelly and Kornienko will spend about a year living and working aboard the space station on the marathon mission. Padalka will remain on board for six months.

Streak shot of Expedition 43 Launch to the ISS on March 27 Eastern time, (March 28, 2015, Kazakh time)  from the Baikonur Cosmodrome in Kazakhstan with Scott Kelly, Mikhail Kornienko, and Gennady Padalka to start one-year ISS mission. Credit: NASA/Bill Ingalls
Streak shot of Expedition 43 Launch to the ISS on March 27 Eastern time, (March 28, 2015, Kazakh time) from the Baikonur Cosmodrome in Kazakhstan with Scott Kelly, Mikhail Kornienko, and Gennady Padalka to start one-year ISS mission. Credit: NASA/Bill Ingalls

The goal is to use the massive orbiting outpost to provide critical knowledge to NASA and researchers hoping to better understand how the human body reacts and adapts to long-duration spaceflight and the harsh environment of space.

The pathfinding mission is about double the normal time of most expeditions to the Earth orbiting space station, which normally last four to six months.

The one-year mission is among the first concrete steps to start fulfilling NASA’s “Journey to Mars” objective of sending “Humans to Mars” in the 2030s.

“Scott Kelly’s mission is critical to advancing the administration’s plan to send humans on a journey to Mars,” said NASA Administrator Charles Bolden, in a statement.

“We’ll gain new, detailed insights on the ways long-duration spaceflight affects the human body.”

Year in Space Begins With Soyuz Launch.  Media photograph the Soyuz TMA-16M spacecraft as it launches to the ISS with Expedition 43 NASA astronaut Scott Kelly, Russian cosmonauts Mikhail Kornienko and Gennady Padalka of the Russian Federal Space Agency (Roscosmos) onboard at 3:42 p.m. EDT Friday, March 27, 2015 (March 28 Kazakh time) from the Baikonur Cosmodrome in Kazakhstan. Credit: NASA/Bill Ingalls
Year in Space Begins With Soyuz Launch. Media photograph the Soyuz TMA-16M spacecraft as it launches to the ISS with Expedition 43 NASA astronaut Scott Kelly, Russian cosmonauts Mikhail Kornienko and Gennady Padalka of the Russian Federal Space Agency (Roscosmos) onboard at 3:42 p.m. EDT Friday, March 27, 2015 (March 28 Kazakh time) from the Baikonur Cosmodrome in Kazakhstan. Credit: NASA/Bill Ingalls

This evening the three man international crew successfully rendezvous and docked at the ISS at the Poisk module at 9:33 p.m. EDT – just four orbits and six hours after liftoff.

‘Contact and capture confirmed, 1 year crew has arrived,’ said the NASA launch commentator Don Huot. “The one-year crew has arrived.”

“Soyuz is firmly attached to the ISS.”

Soyuz spacecraft on final approach to dock with the ISS for #YearInSpace mission. Credit: NASA
Soyuz spacecraft on final approach to dock with the ISS for #YearInSpace mission. Credit: NASA

Docking took place about 253 kilometers off the western coast of Colombia, South America approximately 5 hours and 51 minutes after today’s flawless launch from Baikonur.

The crews are scheduled to open the hatches between the Soyuz and ISS at about 11:15 p.m. EDT/315 GMT this evening after conducting pressure, leak and safety checks.

NASA astronaut Scott Kelly gives a thumbs-up from inside the Soyuz TMA-16M taking him and Expedition 43 crewmates Mikhail Kornienko, and Gennady Padalka of the Russian Federal Space Agency (Roscosmos) to the International Space Station after a successful launch from the Baikonur Cosmodrome in Kazakhstan.  Credit:  NASA
NASA astronaut Scott Kelly gives a thumbs-up from inside the Soyuz TMA-16M taking him and Expedition 43 crewmates Mikhail Kornienko, and Gennady Padalka of the Russian Federal Space Agency (Roscosmos) to the International Space Station after a successful launch from the Baikonur Cosmodrome in Kazakhstan. Credit: NASA

The arrival of Kelly, Kornienko and Padalka returns the massive orbiting outpost to its full six person crew complement.

The trio joins the current three person station crew comprising Expedition 43 commander Terry Virts of NASA, as well as flight engineers Samantha Cristoforetti of ESA (European Space Agency) and Anton Shkaplerov of Roscosmos, who have been aboard the complex since November 2014.

“Welcome aboard #Soyuz TMA-16M with Genna, Scott, and Misha- we just had a succesful docking,” tweeted Virts this evening post docking.

The 1 Year mission will provide baseline knowledge to NASA and its station partners – Roscosmos, ESA, CSA, JAXA – on how to prepare to send humans on lengthy deep space missions to Mars and other destinations in our Solar System.

A round-trip journey to Mars is likely to last three years or more! So we must determine how humans and their interactions can withstand the rigors of very long trips in space, completely independent of Earth.

Astronaut Scott Kelly will become the first American to live and work aboard the orbiting laboratory for a year-long mission and set a new American duration record.

Scott Kelly and Russian Cosmonauts Kornienko and Padalka are all veteran space fliers.

They have been in training for over two years since being selected in Nov. 2012.

No American has ever spent anywhere near a year in space. Four Russian cosmonauts – Valery Polyakov, Sergei Avdeyev, Vladimir Titov and Musa Manarov – conducted long duration stays of about a year or more in space aboard the Mir Space Station in the 1980s and 1990s.

Kelly and Kornienko will stay aboard the ISS until March 3, 2016, when they return to Earth on the Soyuz TMA-18M after 342 days in space. Kelly’s combined total of 522 days in space, will enable him to surpass current U.S. record holder Mike Fincke’s mark of 382 days.

Padalka will return in September after a six month stint, making him the world’s most experienced spaceflyer with a combined five mission total of 878 days in space.

NASA Astronaut Scott Kelly and Russian Cosmonaut Mikhail Kornienko comprise  the first ever ISS 1 Year Crew
NASA Astronaut Scott Kelly and Russian Cosmonaut Mikhail Kornienko comprise the first ever ISS 1 Year Crew

They will conduct hundreds of science experiments focusing on at least 7 broad areas of investigation including medical, psychological and biomedical challenges faced by astronauts during long-duration space flight, as well as the long term effects of weightlessness and space radiation on the human body.

Another very unique science aspect of the mission involves comparative medical studies with Kelly’s identical twin brother, former NASA astronaut and shuttle commander Mark Kelly.

“They will participate in a number of comparative genetic studies, including the collection of blood samples as well as psychological and physical tests. This research will compare data from the genetically identical Kelly brothers to identify any subtle changes caused by spaceflight,” says NASA.

Scott Kelly is a veteran NASA Space Shuttle commander who has previously flown to space three times aboard both the Shuttle and Soyuz. He also served as a space station commander during a previous six-month stay onboard.

Good luck and Godspeed to Kelly, Kornienko and Padalka – starting humanity on the road to Mars !!

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

Expedition 43 crew members Mikhail Kornienko of the Russian Federal Space Agency (Roscosmos), top, NASA astronaut Scott Kelly, center, and Gennady Padalka of Roscosmos wave farewell as they board the Soyuz TMA-16M spacecraft ahead of their launch to the International Space Station.  Credit:  NASA/Bill Ingalls
Expedition 43 crew members Mikhail Kornienko of the Russian Federal Space Agency (Roscosmos), top, NASA astronaut Scott Kelly, center, and Gennady Padalka of Roscosmos wave farewell as they board the Soyuz TMA-16M spacecraft ahead of their launch to the International Space Station. Credit: NASA/Bill Ingalls

Have A Heart! This Organ Plays Shape-Shifter In Space, Leading To Mars Mission Questions

Astronaut Piers Sellers during an STS-121 spacewalk in 2006 to demonstrate techniques on repairing the shuttle's heat shield. Credit: NASA

Could a long mission to Mars increase your risk of heart problems back on Earth? That’s something that scientists are trying to better understand after discovering that hearts become temporarily rounder in space, at least in a study of 12 astronauts.

The finding doesn’t appear to be a big surprise for cardiovascular scientists, however, who had the astronauts examine their hearts using ultrasound machines on the International Space Station as well as before and after spaceflight. The heart gets 9.4 percent more round, similar to models developed for the project, before returning to its normal shape on Earth.

“The heart doesn’t work as hard in space, which can cause a loss of muscle mass,” stated James Thomas, lead scientist for ultrasound at NASA, and senior author of the study. “That can have serious consequences after the return to Earth, so we’re looking into whether there are measures that can be taken to prevent or counteract that loss.”

Astronauts typically spend six months on the International Space Station. One year from now, NASA’s Scott Kelly and Roscomos’ Mikhail Kornienko are going to launch for a one-year mission. Spending months upon months in space leads to a host of problems upon returning to Earth. Your muscles get weaker, you’re more likely to pass out, and you’re at increased risk of bone fractures, among other problems.

NASA astronaut Norm Thagard exercises aboard the Russian Mir space station in 1995. Thagard was the first American to launch into space aboard a Soyuz and spent what was then a record-breaking 115 days in space. Credit: NASA
NASA astronaut Norm Thagard exercises aboard the Russian Mir space station in 1995. Thagard was the first American to launch into space aboard a Soyuz and spent what was then a record-breaking 115 days in space. Credit: NASA

A typical person on the space station spends two hours a day exercising just to ward off the worst of the effects. The researchers added that one remedy could be to add more exercises targeting the heart. This will be particularly important for missions that last 12 to 18 months or more — such as a Mars mission.

Studying astronauts in space could provide data on Earth-bound patients facing similar problems, the researchers said. Since the models that they made for astronauts were so congruent with reality, this gives the researchers confidence that they could create similar models for patients on Earth.

Conditions that could be considered include ischemic heart disease (the most common kind of heart disease and source of heart attacks), hypertrophic cardiomyopathy (thickened heart muscle)  and valvular heart disease (damage to one of the heart’s valves).

Results were presented last week at the American College of Cardiology’s annual conference. It’s not immediately clear from a press release if the study was peer-reviewed. The researchers added that more study of astronauts after returning to Earth could be a useful research direction, to see how the effects persist (if at all.)

Source: American College of Cardiology

Expedition 37/38’s Tips For Surviving Long Voyages in Space

Russian cosmonaut Oleg Kotov (left), Expedition 37 flight engineer and Expedition 38 commander; along with NASA astronaut Michael Hopkins (center) and Russian cosmonaut Sergey Ryazanskiy, both Expedition 37/38 flight engineers. Credit: NASA

NASA wants to bring its astronauts outside of Earth. It recently recruited a new astronaut class for deep space voyages. It’s talking about picking up asteroids and possibly heading to the moon or Mars in the distant future. But there are a heck of a lot of steps to do before anyone can head into space for long periods of time.

The agency and Roscosmos are preparing for a one-year voyage to the International Space Station in 2015 that will add to the limited set of data on people being in space consecutively for a year, or longer. You can bet there will be reams of information collected on sleep habits, bone loss, muscle shrinkage, eye pressure and other health factors of concern.

How about the psychological side? The next space station crew to launch gave some hints about how their training prepares them to live cheek-by-jowl in a tiny space for six months.

The mission’s main goal:

The main goal is to put the station in a good condition, and also for the Russian segment, to [install] the new module, MLM (Multipurpose Laboratory Module.) We’re all targeted to this job. Me especially, being the commander of the station, I have the responsibility of the whole crew and their success and also for their psych [psychological] atmosphere. That’s really what I want to do. — Oleg Kotov, Expedition 37 flight engineer, Expedition 38 commander and preparing for his third spaceflight

Receiving advice from past crews:

Sometimes it’s the little things in terms of how to deal with, for example … the food and your clothes and supplies. Other times it’s trying to make sure you’re focusing on the critical items, and not necessarily getting caught up in all the little details [because] you’re going to be there for such a long amount of time.  — Michael Hopkins, Expedition 37/38 flight engineer and rookie astronaut

The Mars 500 long-duration mission vs. flying to the space station:

Mars 500 was really aimed at science. Most of the station [work] is mostly of the safety of the crew and the safety of the station, and then the [next priority is] science. But it also was a great experience to see, psychologically, the space station can be isolating, and how great the influence of this psychology is on the crew. So that was really the experience. Being commander there helps me a lot in my training for real flight.” — Sergey Ryzansky, commander of a 105-day segment as part of phase two of the Mars 500 program, Expedition 37/38 flight engineer and rookie cosmonaut

Michael Hopkins, Expedition 37/38 flight engineer, during spacewalk training. Credit: NASA
Michael Hopkins, Expedition 37/38 flight engineer, during spacewalk training. Credit: NASA

Communications with Mission Control:

Sometimes you ask a question or an item from the ground, and just realizing that you’re not always going to get that answer right away. Sometimes it takes some time for them to determine what the right answer is. — Hopkins

The challenge for other planets:

[I study] how to develop countermeasure means for flights on another planets. After 200 days, for example, flying in space, then we need human beings to work in a spacesuit on the surface of other planets, in different gravity. — Ryzansky

Artificial Gravity

An artist's representation of a rotating space station.

[/caption]
Have you ever noticed that astronauts float around in the space shuttle and in the International Space Station, while space travelers on television and in the movies keep their feet firmly on the ground. That’s because it would be very difficult (and expensive) to have your actors floating around in every scene. So science fiction writers invent some kind of artificial gravity technology, to keep everyone standing on the ground.

Of course, there’s no technology that will actually generate gravity in a spaceship. Gravity only comes from massive object, and there’s no way to cancel the acceleration of gravity. And so if you wanted to have a spacecraft that could generate enough artificial gravity to keep someone’s feet on the ground, the spaceship would need to have the mass of the Earth.

Floating in space is actually very hard on astronauts’ bodies. The lack of gravity softens their bones and causes their muscles to weaken. After any long trip into space, astronauts need several days and even weeks to recover from traveling in microgravity.

But there a couple of ways you could create artificial gravity in a spaceship. The force we feel from gravity is actually our acceleration towards a massive body. We’d keep falling, but the ground is pushing against us, so we stand on the ground. If you can provide an alternative form of acceleration, it would feel like gravity, and provide the same benefits of standing on the surface of a planet.

The first way would be through accelerating your spaceship. Imagine you wanted to fly your spaceship from Earth to Alpha Centauri. You could fire your rockets behind the spacecraft, accelerating at a smooth rate of 9.8 meters/second2. As long as the rocket continued accelerating, it would feel like you were standing on Earth. Once the rocket reached the halfway point of its journey, it would turn around and decelerate at the same rate, and once again, you would feel the force of gravity. Of course, it takes an enormous amount of fuel to accelerate and decelerate like this, so we can consider that pretty much impossible.

A second way to create acceleration is to fake it through with some kind of rotation. Imagine if your spaceship was built like a big donut, and you set it spinning. People standing on the inside hull would feel the force of gravity. That’s because the spinning causes a centrifugal force that wants to throw the astronauts out into space. But the spaceship’s hull is keeping them from flying away. This is another way to create artificial gravity.

There are no spacecraft that use any form of artificial gravity today, but if humans do more space exploration, we will likely see the rotational method used in the future.

We have written several articles about artificial gravity for Universe Today. Here’s an article about how mice might be used to test out artificial gravity, and here’s more information about future technologies that might use artificial gravity.

Here’s a podcast from Scientific American that talks about the effect of artificial gravity.

We have recorded an episode of Astronomy Cast that talks about science fiction technologies. Listen to it here: Episode 104 – Science Fiction at Dragon*Con

Sources:
Wikipedia
NEWTON, Ask A Scientist!
Wise Geek