Archives of Ask A Scientist!
About "Ask A Scientist!"
On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.
Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.
However, this is not really how most of the protons in the Universe were created. Cosmologists believe that there were no protons until about a microsecond had passed since the Big Bang.
The key idea is that protons themselves are not elementary particles, but are made up of particles called quarks. At very early times after the Big Bang, the Universe was a soup of elementary particles including electrons and their antiparticle, the positron, photons, quarks and antiquarks, among others. Many different reactions, including creation of quarks and antiquarks from collisions of photons, maintained a mixture of these particles. As the Universe aged, it also cooled, and once it got cold enough -- about a few trillion degrees -- the quarks in the soup bound up into particles called hadrons, which include not only the proton but also the neutron, the two constituents of all atomic nuclei.
Some nuclear reactions can convert protons into neutrons and vice versa, and others can bind them up to form atomic nuclei, much as the Sun burns protons into ordinary helium, which consists of two protons and two neutrons. Such reactions acted for a very short time in the early Universe, ceasing about three minutes after the Big Bang. The end result was a mixture of protons, helium and deuterium, with about 75% in the form of protons, about 25% in the form of ordinary helium, and tiny traces of deuterium (a bound state of a proton and a neutron sometimes called "heavy hydrogen''), helium-3 (which has two protons but only one neutron), and even smaller traces of lithium. Based on numerous observations and calculations, astrophysicists have concluded that all of the deuterium in the Universe today, and most of the ordinary helium, were produced about three minutes after the Big Bang.
Thus, the protons and neutrons in stars did not always exist but have been around since very early in the history of the Universe. Moreover, experiments show that the proton is exceptionally stable. Lower limits on its lifetime exceed a million trillion trillion years!
- What is ozone and what makes it?
- Why do the moon and the sun seem to change colors?
- I've always been puzzled by the way celestial bodies orbiting one another tend to "line up" on a roughly two-dimensional plane. Take the Solar System, for example: in all of the illustrations or moving simulations of planetary orbits I have seen, the planets always align themselves along roughly the same horizontal axis, with only slight vertical variation in their respective orbits. Is this phenomenon of "horizontal alignment" a result of the gravity of all the planets / moons / rings kind of pulling each other together even while they are all orbiting the same sun / planet? Was there an earlier time in the history of the solar system or of individual planets where there was a greater disparity between the horizontal alignments of different orbiting bodies? Or have I just been seeing simplified illustrations that don't accurately reflect all three dimensions in which bodies orbit other celestial bodies?
- What are Saturn's rings made of?
- How do we know how old the earth is?
- Why is space black?
- What happens at the absolute speed of zero? The earth is moving at some speed, the galaxy is moving at some speed. If you could stop all direction and speed, what would happen?
- What causes lightning?
- What is the aurora borealis and why does it occur?
- What was there before the "Big bang?" Why did it happen?