Gravitational Waves are Not the Ultimate Test of General Relativity

Last year’s ground breaking gravitational wave detections generated some of the widest media coverage of a scientific discovery to date. Many articles and reports described the detection as the “ultimate” test of general relativity, the “final” test of general relativity, or confirmation of Einstein’s “last” prediction. For a theory that is 100 years old, that was developed by one of the most celebrated physicists of all time, and has survived every experiment thrown at it, you could be forgiven for thinking that general relativity is done and dusted. However, general relativity is far from facing its “ultimate” test.

Gravitational Waves — another success for General Relativity, but not the final test.

Gravitational Waves — another success for General Relativity, but not the final test.

Over the past century, general relativity has been put through its paces with some of the brightest minds on the planet developing new ways to test it. General relativity explains anomalies in the planet Mercury’s orbit around the Sun, why the universe cannot be static, and the way star-light is deflected by massive bodies like the Sun and distant galaxies. Predictions of general relativity have been tested using high-precision gyroscopes on satellites orbiting the earth and atomic clocks, by timing the orbits of distant neutron stars, and now, by the direct detection of gravitational waves. General relativity has survived every test, passing with flying colours. Even the fact that GPS functions properly is evidence of the success of general relativity.

But the nature of the scientific method means that no test that general relativity survives will be its ultimate test. Scientists will never stop testing general relativity until it fails. We know general relativity is not the final solution to a theory of everything, and we are reasonably certain that general relativity must fail at some point. While general relativity has been spectacularly successful in describing the large-scale workings of the cosmos (such as solar systems, galaxies, and the entire visible universe), it does not work on the small scale (atoms, nuclei, and fundamental particles), for which we need quantum mechanics. General relativity does not tell us what goes on inside a black hole, or at the moment of the Big Bang, because, in those situations, we are dealing with much smaller scales where quantum mechanics comes in to play. While we are very aware of general relativity’s ultimate limitations, this does not give us a very convenient starting point for developing a replacement theory. Like an engineer investigating the collapse of a bridge, if we can find the exact point of failure, we are better able to develop a solution. Because of this, many tests of general relativity today seek to determine the exact point at which general relativity breaks.

Most of the current approaches to breaking general relativity assume the devil is in the detail, and aim to make more precise measurements of previously tested phenomena. As more and more gravitational wave events are detected and studied, they will provide ever more stringent tests of the predictions made by general relativity. One research group wants to measure the precise orbits of different types of metal around the Earth, while another wants to time the fall of different types of atoms, things that general relativity says should show no difference between the different materials and atoms. The ESA’s ACES mission aims to make the most precise measurements ever of gravitational time dilation and gravitational redshift. If general relativity passes these tests, physicists will celebrate another success for a brilliant theory and for human intellect, and will then set about designing the next test. However, if, for any of these experiments, the predictions of general relativity do not match the data, physicists will celebrate the discovery of the breaking point, and the dawning of a new era in our understanding of the nature of the universe.

In order to get to space, throw yourself at the planet, and miss.

High precision space- and ground-based experiments aim to test General Relativity in minute detail

Rest assured, articles claiming “[Some experiment] is the ultimate/final test of Einstein’s greatest theory” are not yet a thing of the past.

Floating in the Sea of Tranquility

Why we should build a swimming pool on the Moon

We choose to build a pool on the Moon, not because it is easy, but because it is hard.

A recent special issue of the New Space journal reported on the reasons and methods for constructing a permanently inhabited lunar colony, and that it could be done within the next few years and for around $10 billion.

On Sundays we go outside and flip off everyone on Earth.

A bargain at only $10 billion.

A lunar colony would provide invaluable experience and technological development for future missions to Mars and beyond, as well as being extremely scientifically useful. The only reason moon colonization missions are not on the cards is because NASA believe they have the budget to get to the Moon, or Mars, but not both. However, as the contributors to the New Space journal have argued, thanks to developments in 3D-printing, life support systems, and reusable launch vehicles, this is no longer the case.

While we’re building that moon colony, we should equip it with an Olympic-sized swimming pool.

That would be really cool

As already demonstrated by Randall Munroe of xkcd What If, a swimming pool on the Moon would be really cool. Due to the low gravity a swimmer wearing fins could leap 4 or 5 metres out of the water. The shear awesomeness of this endeavour would stimulate great interest from the public. A pool would also be a huge morale boost to the crews of the Moon base during their long missions.

Thanks to reusable vehicles such as SpaceX’s Falcon 9 and Dragon, the cost of a flight to an established base on the Moon would fall to a few tens of millions of dollars, putting it in the price range of space tourism trips for eccentric billionaires, and providing a supplementary source of funding.

It would also provide scientists with an opportunity to categorically prove whether or not a human can run on water in low-gravity as predicted by this paper.

Still pretty weird though.

Not even the weirdest thing I’ve seen in the lab.

The technological challenge has massive benefits

Building a swimming pool on the Moon, especially an Olympic-sized one, would be an immense technological challenge, but the technologies developed and lessons learned during this program would kick-start deep space exploration and industries such as asteroid mining.

An Olympic-sized pool of water would be too stupidly expensive to transport to the Moon, even assuming the most optimistic forecasts of SpaceX’s launch cost reductions. The materials to build the pool and the water to fill it would have to be mined from the Moon itself. The tools and techniques developed to mine these resources would have direct application to asteroid mining, an industry that promises to supply huge quantities of rare and valuable minerals without destroying ecosystems back home on Earth. Obtaining resources in this way is a necessary precursor to humanity establishing bases on other worlds.

If they can get those barge landings sorted.

A properly reusable vehicle like the Falcon 9 Heavy will revolutionize space travel.

Mining huge quantities of water from celestial bodies is a necessary step in the production of rocket fuel to support manned missions into deep space. The surest way to reduce the effects and risks of space flight to humans is to reduce the flight time. To do this, we would need refuelling stations at strategic points throughout the solar system. Also, permanent human habitation will require colonists to work to reduce their dependence on supplies from Earth, and this means obtaining huge quantities of water to grow the food necessary to sustain a colony. The Moon would be the first small step of humanity’s giant leap out into the cosmos.

The structure required to house an Olympic swimming pool and protect it from the vacuum of space would be far larger than anything currently envisioned for missions to the Moon or Mars in either the short- or mid-term. However, if humanity is really going to colonize Mars, or other bodies in the solar system, then we are going to need large spaces such as this to play and exercise. If we can’t build large recreation spaces like this one, permanent human habitation of deep-space colonies will not be a realistic goal.

As with humanity’s other forays into space, the technologies developed during the project will have useful, important, and lucrative spin-offs on Earth. For example, waste management and resource recycling systems, of critical importance to a Moon colony, would be applied on Earth to reduce our environmental footprint and improve sustainability.

 

Building a swimming pool on the Moon will hone the tools and techniques that humanity needs to develop if we are going to expand into deep space and reap the benefits of becoming a truly space-faring race, while the scale of the goal will inspire scientists and the public alike. Big goals spur big leaps in technological and scientific progress, and I think you’d have to agree, this would be pretty cool.

Space for Innovation

Australia needs a space program.

As 2015 drew to a close, Prime Minister Malcom Turnbull unveiled the government’s Innovation Statement with a plan to invest $1.1 billion to drive an Australian “ideas boom”. Before this announcement, the government had already commenced its Review of the Space Activities Act 1998 stating that Australia is in a transition ‘to an advanced economy that cultivates and commercialises innovative technologies’ and that ‘there is significant potential for space technologies to play a role in facilitating this transition…’ It is high time Australia invested in a space program.

Australia is the only OECD country that does not have a space agency or coordinated space program. China and India both established space agencies in the mid-20th century which have contributed immensely to the countries’ technological capabilities and economic growth. Even Ethiopia has recognized the huge advantages afforded by a dedicated space program, establishing a space agency in August 2015.

Why does Australia need a space program?

In the 21st century a space program will be a key instrument for sustainable development. For the average person, the impact that space technologies have on their lives is not immediately obvious, often being hidden away behind some product, service, or app, but all of us benefit immensely every day from what space programs have brought us. We would all notice very quickly if we lost our GPS and satellite communication infrastructure, but space technology goes much further. Satellites are used for environmental monitoring, weather prediction, soil monitoring, water and agricultural management, as well as to search for ore bodies, track bushfires, and in disaster planning. This short list barely makes a dent in the complete list of important space technologies, and doesn’t even touch on the spin-offs, the technologies developed by space agencies that have found other uses and applications.

A space program will cultivate scientific thinking and technological innovation, and provide the training to engineers, scientists and students that Australia needs if we want to maximize the progress from our “ideas boom”.

A national space program will ensure that innovative ideas are exploited to their fullest by stabilizing funding to projects under its aegis. A space agency is also necessary if we are going to cooperate with other countries in the exploration and exploitation of space, since an agency with technical expertise that represents the Australian government will be in a position to negotiate with NASA, the ESA and other countries’ space agencies. An Australian space agency will even reduce the time and cost required to purchase flights on other countries’ launch vehicles.

I liked the picture of a satellite.

Out of sight, out of mind: vital technologies are operating overhead all the time.

They’re expensive. Couldn’t the money be better spent on something other than rockets?

When figures like NASA’s $19.3 billion 2016 budget are bandied around, and even a small space mission costs tens of millions of dollars, it often seems that space programs are too expensive to be worthwhile and that there are other problems we should be using this money to solve. However, put in context with other spending, a space program doesn’t appear to be so expensive.

NASA’s $19.3 billion represents only 0.5% of the US government’s spending, while the US military takes more than 15% of the total. The economic return to the USA gained from NASA’s products, patents, services, and spin-offs means that NASA more than pays its way. Australia is in a not-too-dissimilar position, with around A$30 billion being spent on defence. If we were to copy the US, we would direct around $1 billion to a space program. Australia has the money for a space program, it is only a matter of public choice and political will to divert the necessary funds. And that’s not even taking into account that space programs generate revenue for the government. History has shown that space programs are a very good investment. An Australian space program would begin to pay for itself after only a few years.

NASA’s $19.3 billion sounds like a lot less money when you take into consideration the huge range of projects NASA is responsible for. A reasonable summary of NASA’s active and on-going projects would fill a small book. They include climate and crop monitoring, satellite tracking, observational astrophysics, space-vehicle development, aeronautics, launch contracting, running a space-station and driving a nuclear-powered laser-equipped science-car on Mars. Australia is unlikely to match this commitment (at least in the short-term).

Individual space missions, even pioneering interplanetary missions, can be quite cheap when compared to other things we are willing to spend huge amounts of money on. India became the first country to successfully reach Mars orbit on its first go with the Mangalyaan Mars orbiter, which cost only US$73 million. Major blockbuster movies rarely cost less than $100 million these days. James Bond Spectre cost $245 million, the CGI movie Tangled cost $260 million, while Pirates of the Caribbean: On Stranger Tides cost an eye-watering $378.5 million.

Also, we do not have to spend big money on huge projects such as shuttles and space stations like Russia, China, and the US. The UK and Canadian space agencies provide a very good model for a similar Australian organization. We don’t need to have a launch vehicle, we just need to start contributing to international space project collaborations.

A space program is not a luxury. It is a key to a sustainable future and developing scientific thinking.

We should totally build one of these any way.

As cool as it would be to have one of these, this is probably not what an Australian space program will look like.

What have we got to offer?

I have come across the belief that Australia has little it can offer the international space science community (and therefore should leave space up to other countries) disturbingly often, and nothing could be further from the truth. Australia has had a small but outstanding role in space since the 1960s, and in a field as diverse as space research, there is always something we can offer both in international collaborations and from Australia-only projects.

Universities and research organizations across the country already have some involvement in space research. We are world leaders in the development of scramjet technology, we are internationally renowned in radio astronomy and computer sciences, we are participating in space missions such as eLISA and the GRACE follow-on, we have important deep-space tracking facilities, and we have the most productive geodetic observatory in the world.

A space program also affords Australia the opportunity to focus efforts on problems that are unique to Australia. This article in The Conversation from 2013 addresses the reasons why Australia urgently needs a space program to solve our own problems and to stop piggybacking on other countries’ space projects.

Western Australian Space Centre

The Western Australian Space Centre: the site of the world’s most productive laser ranging station.

What should we do?

We need to establish a space agency with its own slice of government funding. This is necessary to produce the funding stability I discussed previously and exploit space research to the full.

The Review of the Space Activities Act needs to provide appropriate recommendations so that future legislation minimizes red tape and makes it easy for Australian agencies and research organizations to conduct research within Australia, and to collaborate with other nations.

We need to start training our students for the space sector. A huge number of brilliant STEM students are being attracted to space science at the undergraduate level, but there are too few programs and training opportunities for all but a few of them to continue down this path. Increased support for space research at all levels of education will be needed to develop and exploit Australia’s intellectual resources and drive innovation.

We need to get the public excited about space through science communication, media attention, and school programs.

The public excitement will only grow as Australia’s space program progresses. By collaborating with NASA, the ESA and other space agencies and contributing to international projects, Australia will be eligible to select its own astronauts. While Australian-born Americans have flown in space, no one has gone to space with an Australian flag on their shoulder. The media attention surrounding Canada’s Chris Hadfield and the UK’s Tim Peake show just how much public excitement is generated by space flight, and with proper science communication efforts, this excitement will feed back into greater support for space science and the benefits it has to offer.

Has anyone got a suggestion for a good name for our space agency?

This is here just because I like this picture.

WRESAT: Australia’s first satellite.