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by
Joseph Silk
relies on settling the Moon and using it as a base to probe the deepest questions in the Cosmos...
The search is on for an Earth-like exoplanet in a solar system light-years away.
Closer to home, we'll soon be excavating the icy moons of Jupiter for life in watery realms. There's a global drive to develop the Red Planet, Mars, where proposals include human outposts, tourism, and an intensive search for ancient life.
Mars may loom in our collective imaginations as the next world out, but prospects for humans living there are actually dim. The landscape is arid, and Martian dust is especially toxic.
The trip to Mars would expose travelers to lethal levels of radiation, which engineers and astrobiologists are hoping to mitigate eventually.
Since the long voyage to
Mars is currently too dangerous for crewed travel, robotic
exploration there will likely dominate for several decades to come.
When you get right down
to it, despite our dreams of travelling far, the orbiting body next
door, the Moon, is our next real target - and the true portal to the
cosmos at large.
Now it's time to return. Reaching the Moon again is practical. It is an essential first step to exploration of the distant Universe. And it is inevitable.
We'll achieve this by
constructing novel telescopes of unprecedented scope in dark lunar
craters and on the far side of the Moon.
The resulting lunar infrastructure will open the way to building powerful telescopes that will provide new vistas into key questions that have long obsessed humanity.
Space exploration is our destiny, but we can only fulfill it, only discover the deepest mysteries of our Universe, by first returning to the Moon.
Many commercial activities are already on the drawing board, spearheaded by space agencies and the private sector alike.
The Moon offers dazzling new horizons for leisure and sports activities.
Transport for the first decades of human lunar travel will be expensive. But there is a pent-up demand for luxury tourism. Today's overwhelming demand will be addressed initially with orbital trips around the Moon.
Tickets are already being
sold by the likes of SpaceX for launches planned within five years.
Tourist lunar landings may now seem pure fantasy, but the will is
there.
Imagine,
Their appetite for new forms of tourism seems insatiable. However, access is certain to change over time once low-cost space transport systems are developed.
We would establish giant
lunar parks for leisure and relaxation. Low-cost housing would be
designed to host the necessary support personnel. Mass tourism will
have its day. Commercial backing will certainly fund these
activities.
As reserves of rare earth elements are depleted on Earth, lunar resources will step up to the task. Lunar mining may provide an effectively limitless supply of them.
Rare earth elements are central to present and future technologies.
Here on Earth, scientists project that we will exhaust rare earth elements in less than 1,000 years.
Yet bombardment of the Moon by asteroids over billions of years has deposited trillions of tons of rare earths on the lunar surface, based on analysis of the Apollo lunar samples.
Rare earth elements are mined on Earth through environmentally polluting operations.
This is such a toxic process that extraction is highly restricted. We can limit the inevitable pollution with robotically aided extraction, and lunar launch sites will facilitate ejection of toxic debris into space.
Rare earth elements are
key to present and future technologies. It will be difficult for
mining companies to resist the challenges of lunar extraction. The
potential rewards are enormous.
The needed fuel, in the form of liquid hydrogen and oxygen, would be sourced from ice deposits in cold polar craters.
Rocket fuel depots and spaceports are the future. Lunar fuel resources are a key component of interplanetary travel. We will make use of low lunar gravity to launch spacecraft throughout the solar system.
Lunar spaceports will
eventually serve as gateways to the stars.
We must look beyond the compelling goals of lunar and even interplanetary exploration along with commercially driven projects to seek answers to the most fundamental questions ever posed by humanity:
Telescopes will
eventually provide the answers, but on a scale beyond our current
dreams.
There's no atmosphere to limit our view. Stars don't twinkle, they shine as brilliant points of light. Such clarity is crucial if we are to search for distant planetary systems.
There are sites with
unlimited solar power on the tall crater rims to power our
instruments. Here the Sun never sets. Yet there is extreme cold in
the deep crater basins that remain in permanent shadow.
These might involve,
The conditions for the origin of life are unknown. Based on what we know of the solar system, life is a rare phenomenon. We have no idea how complex organisms might evolve. There are many random evolutionary directions that lead nowhere.
Darwinian evolution is
often invoked. It seems to have worked on Earth but, for all we
know, it could have been an immensely improbable fluke. We might
even be alone in the Universe.
Most of these are billions of years older than Earth.
Such exoplanets, if
inhabited, would inevitably be thousands or even millions of years
ahead of us in evolution. And in technology. They would have had so
much more time to evolve.
However, intelligent life is likely to be 'rare' and relatively 'short-lived'; this we know because we haven't yet encountered any advanced civilizations and because of the potential existential catastrophes that await us...
These span global
epidemics to nuclear wars and major asteroid impacts. Since the
number of likely targets with signs of life is small, we need to
search huge numbers of exoplanets for the elusive signatures of
life.
Exoplanets with rocky cores and Earth-like masses are preferred. Such relatively low-mass exoplanets are hard to detect. It's the larger ones we find most easily. And these are gas giants like Jupiters or Neptunes, hardly congenial to life.
Exoplanets need to have rocky cores
and be in habitable zones around Sun-like stars for conditions
required for life as we know it. After all, that's our only known
criterion for life. No guarantees, but we have just the one example,
our Earth.
And we will need light-gathering power to examine the atmospheric spectrum of our targets.
The list of biological tracers goes on...
This means digging deeply
into the infrared region of the electromagnetic spectrum. And that
requires a really large telescope if we are to see far away.
But even this won't get
us far into the infrared region where our prime signatures of
extraterrestrial biology are to be found.
We could detect the night
glow of any large cities.
We need many targets. And this requires monstrous megatelescopes, with enormous light-collecting apertures. Only by detecting unprecedented numbers of Earth-like planets can we hope to optimize our chances of finding signs of extraterrestrial life.
We may finally answer one of humanity's ultimate questions:
Huge lunar telescopes will also explore the first galaxies and stars in the Universe in unprecedented detail.
They will investigate the first massive black holes that we see shining as quasars. Such black holes are monstrous objects, weighing millions or even billions of solar masses. They are found in the centers of galaxies.
Even our Milky Way galaxy
hosts such a monster in its centre.
We see massive galaxies and black holes appear in the distant Universe, as far back as we can see. A huge black hole can form directly from collapse of a massive cloud of gas.
We 'don't know'...
With large lunar
telescopes, we can learn about the dawn of the Universe. We will see
the end of the dark ages, before there were stars and the first
starlight that heralded a new cosmic age.
Specifically, we will
need a special type of radio telescope operating at very low radio
frequencies. And the far side of the Moon is a unique site for a
low-frequency radio observatory.
Indeed, nearby clouds of
hydrogen gas are observed at the easy-to-detect-frequency of 1,420
megahertz (MHz).
Those longer, redshifted waves with their lower frequency are too ‘dim' for the telescopes of today.
At such low radio
frequencies, the terrestrial ionosphere simply scatters
low-frequency radio waves from deep space. Terrestrial radio noise
created by marine radars, radio and TV broadcasting, and cell phones
all get in the way.
The expansion of space lowers the frequency of these radio waves to the limits of what is observable. By searching for hydrogen clouds at a frequency of, say, 30 MHz, we peer back to a time long before there were any galaxies.
Using telescopes on the Moon, we'll map their radio shadows and finally start to answer the fundamental question:
Sure, we have uncovered the seeds of creation, the fluctuations that seeded galaxies. Yet the data is limited. Ultimately, the signals we tap come from a few million independent points in the sky. We are striving to do better.
But we risk running out
of information in the microwave sky.
To test this, we will need to look more deeply and sensitively into the past.
This is where exploration
of the dark ages can be a game changer - provided that we can
extract more information from the sky than current approaches allow.
With millions of clouds required to form a typical galaxy, the dark ages are our only hope.
They are completely
unexplored territory. They certainly present an enormous challenge,
but they also offer a unique glimpse of the beginning.
Probing the dark ages will open up a trillion bits of information and allow a huge increase in precision over surveys of all the galaxies in the visible Universe.
By moving to the dark
ages and focusing on low-frequency radio signals, we can take a
giant step forward.
This creates a sort of effervescent quantum foam in what otherwise is a vacuum. In other words, the vacuum has energy.
It is this energy that drives inflation. This phase does not last long; the quantum fluctuations are over as soon as space continues to expand and the matter cools slightly, though a trace is left behind in infinitesimal seeds of future structure.
The end of inflation is
where the cosmic journey begins.
Here is the link that will help us attack the ultimate mystery of inflation.
The fluctuations in the hydrogen absorption signal are not totally random. They have some slight asymmetry in their distribution of strengths.
The asymmetry amounts to a primordial deviation from the usual bell-shaped curve that describes any random distribution. Inflation predicts tiny deviations from randomness in the primordial density fluctuations.
This effect has yet to be measured.
But it is a robust prediction, true for all inflation models.
We'll need a huge increase in our current experimental sensitivity to detect it. Remember, elemental hydrogen is comprised of a single electron orbiting a single proton.
The radio waves in question are generated when electrons orbiting their protons flip their spin due to a collision with neighboring atoms.
When in the original position - when electron and proton are aligned - hydrogen has a lower energy signal. When the electron has been knocked out of alignment by the impinging light of the Universe, its spin-flips and the radio frequency is higher.
By seeking out the lower frequency of the original cloud, we can detect the shadow of a remote cloud of hydrogen, against the cosmic background radiation.
In short,
The discovery potential is vast, from the radio to the infrared and optical domains, and even beyond.
As yet, little attention has been given to the unique advantages of a lunar platform for studying the Universe. A standalone giant telescope project is inconceivable for budgetary reasons.
Instead, to cover the cost, lunar telescopes should be a key component of future lunar settlements. Piggybacking on lunar infrastructure meant for industry and tourism opens up new options for science.
Telescopes built
alongside other megaprojects will be a minor overhead, all in all.
The most extraordinary new frontier will be probing the dark ages of the Universe, just as a geologist studies the origins of progressively older layers of rocks here on Earth.
In order to achieve this vision, it must be integral to lunar projects from the earliest stages of planning.
There is an irrefutable
case to be made for science-driven projects integrated into
commercial activities. The scale for all these ventures is decades
or more, but the time to embrace the intent is now.
We again, hope to answer humanity's most fundamental questions:
There is a compelling
scientific case to be made now for a new era of unparalleled
exploration to visualize the edge of the Universe from the surface
of the Moon...
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