For most of this year, we've focused on scientific questions
which we know the answers to. The essence of science, though, is the
investigation of the unknown. The following is a list of the hottest
questions facing physicists today, in my estimation. How will these work
out over the next few decades? You might be a scientist working on these
very questions in a few years. Even if you don't become a scientist,
you will be hearing about progress on these questions in the news during
your lifetime. What scientists discover about these issues will be very
important to everyone
on Earth.
These are listed in no particular order.
QUESTIONS
1. Can we stop or reverse global environmental change?
The activities of humans on Earth are affecting the ecology of the entire planet.
Accumulating CO2 in the atmosphere from burning oil and gasoline is causing
average temperatures to rise (global warming). This is causing the polar ice
caps to melt, which may eventually flood coastal cities. Some other pollution
(most notably chlorofluorocarbons, a.k.a. CFCs) is starting to destroy the
ozone molecules in the upper atmosphere, which absorb UV radiation from the
sun. The resulting increase in UV reaching the surface will increase the
amount of skin cancer. Species are going extinct at an alarming rate. Acid
rain and
logging (to support explosively growing human populations) are destroying
whole forests.
All the news isn't doom and gloom, but action (stopping CFC manufacture, reducing
CO2 emissions and stopping population growth) must be taken. 2.
Is there life elsewhere in the Universe?
Does Earth carry the only life in the Universe? The necessary chemicals — things
like amino acids — have been detected in gas clouds in our galaxy. Astronomers
and biochemists believe that the chemical processes leading to the development
of simple organisms are relatively easy — assuming there is a stable
place for the processes to happen. That means planets. Only since 1995 have
we known of planets orbiting other stars.
These planets are mostly large, like Jupiter or larger, and
probably not conducive to life like on Earth. There may be lots of Earth-size
planets out there, but we don't have the technology to detect them, yet. Once
we have found some Earth-size planets, that doesn't mean they have life on
them, but it increases the chances that there is life elsewhere.
Conditions are not good for life on any of the planets of our own solar system,
with the possible exception of Mars and a few of the moons of Jupiter and Saturn.
Although we know from the Viking, Pathfinder and MER landers and rovers that
there are
no large
life
forms (worm-size
or larger) on Mars, there is a possibility that microbe-size life is there.
There
may
also
be fossilized
remains of ancient microbial life on Mars that is now extinct. (Mars once had a thicker
atmosphere and water, but doesn't now.) Further reading: http://en.wikipedia.org/wiki/Drake_equation.
3. How small can we make machines?
Using a variety of manufacturing techniques, it is now possible to put millions
of transistors onto a computer chip the size of a fingernail. Physicists
and engineers are now trying to adapt those techniques to making small machines — gears,
motors, etc. — microscopic in size. The ultimate dream will be to make
machines that can be injected into a person's bloodsteam, designed to attack
cancer cells, or that can clean up toxic waste by breaking up specific molecules.
It may even be possible to make microscopic machines that can reproduce themselves
from substances they find. Would that be life? Further reading: http://en.wikipedia.org/wiki/Nanotechnology
4. Can we develop alternative energy sources?
We derive most of the energy we use from burning fossil fuels (like oil and
coal) or nuclear energy. These have two great drawbacks. First, there are
limited supplies of oil, coal and uranium. Once used, they can't be replenished,
and they are getting harder and harder to find. Second, the byproducts of
using them are harmful to the environment: burning fossil fuels creates global
warming and acid rain; spent uranium is very radioactive and will remain
dangerous for hundreds of thousands of years. What we need are alternatives.
Solar energy is one possibility. The problem is that today's solar cells
aren't
very efficient: only about 10% of the sunlight that hits them is converted
into electrical energy. If we could find a way to make solar cells convert
80% of available sunlight into electrical energy, that would be revolutionary.
Another possible energy source is nuclear fusion reactors.
5. Are room-temperature superconductors possible?
http://superconductors.org/
6. What is the structure of the quark?
Protons and neutrons are made of smaller particles called quarks. These particles
were mathematically predicted in the early 1960s, and their existence was quickly
confirmed in actual experiments using particle accelerators. Now there
is experimental evidence that quarks are themselves made of smaller particles!
Was Democritus right: is there a smallest piece of matter, or is it possible
to keep making smaller and smaller particles?
7. What are dark matter & dark energy
We understand only 5% of the Universe. The Universe is expanding, as it
has been since the Big Bang approximately 13.7 billion years ago. You
would expect that expansion to be slowing due to the gravitational tug
of the galaxies pulling on each other, but in fact the Universe's expansion
is speeding up. For this to happen, the current understanding of the
cause is that there is a "dark energy" content to space, and that this
dark energy acts kind of like pressure or anti-gravity, accelerating the expansion. To
account for the observed acceleration rate, the total dark energy content
would account for 75% of the total mass-energy of the
Universe. An additional 20% of the Universe is apparently in the form
of matter, but matter that is not formed into stars that glow or nebulae
that emit radiation. This stuff is called "dark matter". Despite the
similar sounding names, dark matter and dark energy are not related to
each other. The only thing they have in common is that we have no idea
what either of them really is. Further reading: http://en.wikipedia.org/wiki/Dark_matter and http://en.wikipedia.org/wiki/Dark_energy
8. What will be the ultimate fate of the Universe?
It seems likely that the Universe will expand forever, but some possibilities
for the nature of the dark energy make it possible for the dark energy
to "reverse sign", leading the Universe to eventually collapse in on
itself again: a Big Crunch.
9. Are the laws of physics unique? The multiverse?
10. Are quantum computers possible?
11. What is the essential nature of consciousness?
12. Why is there inertia?
Higgs boson
13. What is the true structure of space-time?
String theories
14. What is the source of ultra-high-energy cosmic rays? 15. Do gravitational waves exist? What can we learn from them once we
detect them?
16. Why is the Universe mostly made of matter instead of antimatter?
17. What is the cause of the Pioneer anomaly? 18. What unknown questions will confront us?
Lastly, of course there are mysteries in the Universe which we
don't even suspect yet.
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